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Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report (2012)

Chapter: 2 Challenges and Opportunities Associated with Conversion

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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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2

Challenges and Opportunities Associated with Conversion

Session 2 of the symposium (see Appendix A) focused on technical challenges associated with conversion and potential solutions for overcoming those challenges. Three panels of Russian Federation (R.F.) and U.S. speakers were organized to address these topics:

•  Panel 2.1: Technical challenges associated with conversion and potential solutions featured Russian and U.S. presentations on low enriched uranium (LEU) fuel design, core modifications, and approaches for maintaining reactor performance and missions after conversion.

•  Panel 2.2: Other technical challenges associated with conversion featured presentations on ageing and obsolescence, regulatory challenges, and challenges posed by research reactors that cannot be converted.

•  Panel 2.3: How challenges associated with previously converted reactors were overcome featured presentations on approaches for overcoming the conversion challenges identified by the other panels in this session.

These panel presentations are summarized in this chapter along with key thoughts from the participant discussions.

FUEL DESIGN FOR CONVERSION

Two presentations on fuel design for conversion were given by Panel 2.1 speakers: Daniel Wachs (Idaho National Laboratory) reported on efforts to develop LEU fuels for converting U.S.-origin reactors (Wachs, 2011),

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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and Yu.S. Cherepnin (Dollezhal Scientific Research and Design Institute of Energy Technologies [NIKIET]) described progress and prospects for reduction of fuel enrichment in Russian-origin reactors (Cherepnin, 2011).

Fuel Design for U.S.-Origin Reactors

Daniel Wachs

Highly enriched uranium (HEU) fuel elements in U.S.-origin research and test reactors consist of aluminum-clad plates (see Chapter 1) that contain a UAlx or U3O8-aluminum dispersion fuel meat clad in aluminum or a uranium-zirconium hydride (UZrHx) fuel meat clad in stainless steel (TRIGA fuel). Work carried out by Argonne National Laboratory and the Idaho National Laboratory, in cooperation with other American, European, and Korean organizations, has resulted in the development of three LEU dispersion fuel systems1 for conversion of plate-type reactors:

•  UAlx (density = 2.3 grams of uranium per cubic centimeter [gU/cm3])

•  U3O8 (3.2 gU/cm3)

•  U3Si2 (4.8 gU/cm3)

These fuel systems are adequate for converting all but “high performance” research and test reactors.2 There are six HEU-fueled high-performance research reactors in the United States3 as well as four HEU-fueled high-performance research reactors in Europe that cannot be

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1 The Reduced Enrichment for Research and Test Reactors (RERTR) program (see Chapter 1) also participated in the qualification of a fourth LEU fuel system: a uranium-zirconium hydride with an erbium burnable poison (UZrHx-Er) fuel system that is used for the conversion of TRIGA (Test, Research, Isotope production—General Atomics) reactors. General Atomics began developing a higher-density fuel (up to 3.7 gU/cm3) before the RERTR program was started in 1978. The RERTR program performed irradiation tests on 20/20 (i.e., 20 weight percent uranium, 20 percent enriched), 30/20, and 45/20 fuels. The 30/20 fuel was used to convert the Oregon State TRIGA Mark II reactor, discussed later in this chapter, and the University of Wisconsin Nuclear Reactor, discussed in Chapter 3, as well as a number of other TRIGA reactors in the United States and abroad.

2 These high-performance reactors have high-power-density (i.e., high-flux-density) cores. Fuels having higher uranium densities than are available with existing LEU fuels are required to convert these reactors.

3 As noted in Chapter 1, there are two additional HEU-fueled research reactors in the United States (NTR General Electric and TREAT; see Footnote 20 in Chapter 1) that appear to be convertible using current-type LEU fuels. The Department of Energy (DOE) is completing studies to confirm the feasibility of converting these reactors using current-type LEU fuels. Additional research will be required to more fully develop the capability to fabricate these LEU fuels.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

converted with these existing LEU fuel systems. The U.S. reactors are shown in Table 1-1 in Chapter 1; the European reactors are the following:

•  Belgian Reactor 2 (BR2) at the Belgian Nuclear Research Centre in Mol, Belgium

•  Forschungsreaktor München II (FRM-II) at the Technical University of Munich, Germany

•  Jules Horowitz Reactor (JHR), under construction at the CEA Cadarache Research Centre in Cadarache, France (discussed in Chapter 4)

•  Réacteur à Haut Flux (RHF) at the Institut Max von Laue-Paul Langevin (ILL) in Grenoble, France

Higher-density LEU fuel systems based on uranium-molybdenum (UMo) alloys are now under development for use in converting these U.S. and European reactors. Test irradiations have been carried out on several UMo alloys to assess their suitability for use as fuel for these reactors. Testing revealed that alloy phases with high U/Mo ratios (e.g., U-10Mo4) were most stable under irradiation because they suppressed the formation of fission gas bubbles.5

Two LEU fuel systems based on this alloy are now under development by Idaho National Laboratory and partners:

•  UMo dispersion fuel: A UMo alloy dispersed in an aluminum matrix with uranium densities up to 8.5 gU/cm3. An LEU fuel system based on this material is being developed for conversion of BR2, RHF, and JHR.6

•  Monolithic UMo fuel: Metallic UMo foils with a uranium density of 15.5 gU/cm3. An LEU fuel system based on this material is being developed for conversion of ATR, HFIR, NBSR, MITR, and MURR (Figure 2-1).

Test irradiations of fuel elements containing both of these materials are now being carried out to develop and qualify these fuel systems.

UMo Dispersion LEU Fuel

Initial irradiations of fuel elements containing UMo dispersions resulted in the formation of interaction layers between the UMo and Al particles and the development of porosity and distortion (pillowing). The addition of small amounts (∼2 percent) silicon to the aluminum phase was

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4 That is, alloys consisting of 9 parts uranium to 1 part molybdenum by weight.

5 Fission gas bubbles are formed in the fuel phase as a result of the production of gaseous fission products.

6 At present, no LEU replacement fuel has been identified for the FRM II reactor.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

image

FIGURE 2-1 Schematic cross-section of a research reactor fuel element containing monolithic UMo. SOURCE: Wachs (2011).

found to suppress the development of this interaction layer at burnups of up to 70 percent. However, test irradiations of this fuel material at high power (∼ 500 watts per square centimeter [W/cm2]), high uranium loadings (> 8 gU/cm3), and high burnup (> 70 percent) resulted in the formation of small blisters on the fuel plates. Follow-up experiments are planned for the fall of 2011 to determine why such blistering occurs and how the fuel element can be modified to eliminate it. A bounding-case irradiation of this fuel material in BR2 is planned for 2011-2012.

UMo Monolithic LEU Fuel

Fuel plates under development for high-performance U.S. reactors consist of a UMo alloy foil (“U-10Mo Foil” in Figure 2-1) surrounded by a zirconium fission recoil barrier (“2X Zirconium Interlayer” in Figure 2-1) in an aluminum cladding (“Al 6061 Cladding” in Figure 2-1). The barrier is intended to prevent interactions at the interface of the fuel meat and cladding. A key issue for this fuel is the stability of this interface. Although the interface is mechanically stable, swelling of the fuel meat during irradiation could lead to the development of porosity at the interface and eventual delamination of the foil from the cladding. Such swelling and delamination could prove to be a life-limiting factor for this fuel system.

Qualification testing of this fuel for three high-performance research reactors (MITR, MURR, and NBSR) is currently under way. A partial fuel assembly7 is currently being irradiated in ATR at the Idaho National Laboratory (Figure 2-2), and irradiation of ATR fuel elements is planned

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7 As the name suggests, a partial fuel assembly contains only portions of a full fuel assembly. For example, a partial assembly might contain fewer fuel plates than a full assembly.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

image

FIGURE 2.2 End view of a partial fuel assembly (AIFP-7) containing monolithic UMo fuel that is currently undergoing test irradiations in the ATR. SOURCE: Wachs (2011).

to begin in 2012. Lead test assembly irradiations are planned once these irradiations are completed.

Testing of this fuel system for use in the highest-performance U.S. reactors (i.e., ATR, HFIR) is planned to begin in late 2011. Bounding-condition irradiation tests (greater than 500 W/cm2 and greater than 60 percent burnup) on a full-size fuel plate will be carried out at the ATR in late 2011. Fuel qualification testing will be initiated after these irradiation tests are completed.

Fuel Design for Russian-Origin Reactors

Yu.S. Cherepnin

Most Russian research and test reactors use HEU fuels consisting of UO2-aluminum dispersions fabricated as thin-walled tubular elements of various enrichments and configurations. A Russian program was started in the 1990s to further reduce the enrichment of fuel used in Russian-origin research reactors that are located outside of the Russian Federation. This work has been led by three Russian organizations (NIKIET, Bochvar All-

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

Russian Scientific Research Institute for Inorganic Materials [VNIINM], and Novosibirsk Chemical Concentrates Plant [NZKhK]) with the collaboration of several other organizations and customers (i.e., research reactor operators) and has resulted in the development of LEU fuels.

The initial phase of this program created UO2-Al LEU fuel assemblies for conversion of all existing Russian-origin research reactors that are located outside of the Russian Federation. The aim was to reduce the enrichment of uranium in the fuel elements without changing fuel element geometry. LEU fuel assemblies of several designs have been developed (Figure 2-3):

•  VVR-M2 fuel assembly. This assembly has a tubular geometry and contains a UO2-aluminum dispersion fuel meat with a density of 2.5 gU/cm3. These fuel assemblies have undergone a full cycle of design, testing, and licensing and are currently being manufactured at the fuel production facility at NZKhK in Novosibirsk. This fuel is being supplied to Russian-origin research reactors in Hungary, Vietnam, and Romania.

•  IRT-4M fuel assembly. This assembly has a square geometry and contains a UO2-aluminum dispersion fuel meat with a density of 3.0 gU/cm3. This fuel, which is fully licensed, is the highest-demand fuel for Russian-origin research reactors located outside of the Russian Federation. This fuel is being supplied to Russian-origin research reactors in the Czech Republic, Uzbekistan, and Libya.

•  VVR-KN fuel assembly. This assembly has a hexagonal geometry and is being developed for use in a Russian-origin research reactor in Kazakhstan. It will replace a 36 percent enriched assembly that is now in use. Three assemblies have been manufactured and are now being irradiated in the reactor. Conversion studies and fuel qualification activities for this reactor are proceeding in close cooperation with the reactor operator, producing good results.

•  MR fuel assembly. Design work is about to begin to develop a UO2-aluminum dispersion fuel for this tubular fuel assembly. The fuel meat (which currently has an enrichment of 36 percent) is expected to have an enrichment of 19.5 percent with a density no less than 3.5 g U/cm3. It is expected to take about a year to complete this design work and manufacture fuel assemblies for testing. The 19.5 percent enriched fuel will be used in the Russian-origin MARIA research reactor in Poland.

The transition to these LEU fuel assemblies has proceeded using the same fabrication technologies and equipment for producing HEU fuel. However, the use of LEU fuels can reduce reactor “performance” (i.e., reduce neutron flux densities in the core and reflector regions) by up to about 15 percent and shorten fuel replacement cycles. Consequently, the develop-

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

image

FIGURE 2-3 Schematic illustrations of (left) VVR-M2 tubular fuel assembly, (middle) IRT-4M square fuel assembly, and (right) MR tubular fuel assembly. The VVR-KN hexagonal fuel assembly is not shown. SOURCE: Cherepnin (2011).

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

ment of higher-density LEU fuels is needed to maintain reactor performance and fuel cycle length and also to increase fuel robustness by allowing an increase in cladding thickness.

The development of higher-density fuels is being carried out in a second phase of the Russian program to reduce fuel enrichments. Work is proceeding on a UMo dispersion LEU fuel with a density of about 5 gU/cm3.8 Test irradiations of this material have been carried out to burnups of 40-60 percent. Design efforts are under way for two fuel assembly types: IRT-3M (which has a tubular geometry) and IRT-U (which has a pin geometry).

The third phase of the reduced enrichment program is envisaged to involve the development of completely new fuel designs for future reactors. These new designs should be safe, reliable, easy to fabricate, and economically efficient compared to current designs. UMo monolithic LEU fuels manufactured in the form of pins appear to be a promising future design concept. These could be arranged in geometries to mimic the tubular, square, and hexagonal geometries of current-generation fuel assemblies that are used in Russian-origin research reactors.

CORE MODIFICATIONS FOR CONVERSION

Two presentations on modifications of research reactor cores to address the technical challenges of conversion were given by Panel 2.1 speakers: John Stevens (Argonne National Laboratory) provided a U.S. viewpoint on core modifications (Stevens, 2011), and I.T. Tetiyakov (NIKIET) provided a Russian viewpoint (Tetiyakov, 2011).

U.S. Viewpoint on Core Modifications

John Stevens

The conversion of a research reactor from HEU to LEU fuel can result in performance penalties in the reactor, primarily arising from the reduced density of uranium-235 and absorption of neutrons by uranium-238. Modifications to a reactor core may be required to overcome these penalties. Several core modification strategies have been used to overcome the penalties associated with the conversion of U.S.-origin research reactors; these include modifications to the following:

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8 Extrusion processes are used to manufacture research reactor fuel in Russia, whereas rolling processes are used to produce research reactor fuels in the United States and Europe. Both processes produce suitable fuels, but fuel produced by extrusion generally has a lower density than fuel produced by rolling.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

•  fuel plate thickness and reflector locations;

•  fuel meat thickness;

•  uranium and burnable absorber loading; and

•  fueled height of the core.

When making modifications to a reactor core one should strive to change as little as possible. Two particularly successful strategies for overcoming performance penalties that entail minimal changes are (1) tuning the burnable absorber to match the fuel composition; and (2) if cost is acceptable, modifying reflector materials and/or geometries.

Of course, the fuel will, by definition, change from HEU to LEU during the conversion process, and the LEU fuel must be “acceptable” for conversion. An LEU fuel is considered to be acceptable for conversion when it meets the following criteria:

•  Qualified: the fuel assembly has been successfully irradiation tested and is licensable.

•  Commercially available: The fuel assembly is available from a commercial manufacturer.

•  Suitable: The fuel assembly satisfies the criteria for LEU conversion of a specific reactor; safety criteria are satisfied; fuel service lifetime is comparable to current HEU fuel; and the performance of experiments is not significantly lower than for HEU fuel.

•  The reactor operator and regulator agree to accept fuel assembly for conversion.

Successful conversion requires the involvement of reactor operators to understand their needs and constraints.

The following examples were presented to illustrate some of the core modification options that are available to overcome conversion penalties. Some of the reactors described in these examples have already been converted, whereas others have not yet been converted.

Oregon State TRIGA Mark II Reactor

The Oregon State TRIGA reactor is licensed to operate at a steady state power of 1.1 megawatts (MW) and can pulse to 2,500 MW with a peak steady-state thermal flux of about 1013 neutrons per square centimeter per second (n/cm2-s) in the B1 position. The reactor was originally fueled with a 70 percent enriched UZrHx fuel with a 1.6 weight percent erbium burnable absorber. The reactor was converted to a 19.75 percent enriched UZrHx fuel with a 1.1 weight percent erbium burnable absorber.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

image

FIGURE 2-4 Plot of excess reactivity versus time at constant burnup rate for the Oregon State TRIGA Reactor. Adjusting the burnable poison to 1.1 percent in the LEU core provided an acceptable shutdown margin and maintained the longevity of the core (middle curve in the figure). SOURCE: Stevens (2011).

This reactor has a lifetime core, and it was important to the reactor operator to maintain a full grid of fuel assemblies in the converted core to maintain flexibility for conducting irradiation experiments. However, maintaining a full core reduced the shutdown margin (i.e., raised the excess reactivity) at the beginning of life of the new reactor core. Adjusting the erbium burnable poison to 1.1 percent in the converted core restored the shutdown margin and maintained the longevity of the core (Figure 2-4).

RPI Research Reactor

The RPI research reactor is licensed to operate at 1 MW power and has a peak flux of about 3.1 × 1013 n/cm2-s. The core was converted from a 93 percent enriched UAlx-aluminum dispersion fuel to 19.75 percent enriched uranium silicide (U3Si2)-aluminum dispersion fuel in 2007. The LEU fuel contains slightly more uranium-235 than the HEU fuel it replaced to account for the increased neutron absorption by uranium-238.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

The conversion goal for this reactor was to allow for 10 years of operation at acceptable neutron flux density levels using the same number or fewer fuel assemblies. A silicide fuel with the same fuel meat thickness as the original HEU fuel met this goal when the core contained 17 fuel assemblies. However, by increasing the thickness of the fuel meat by 0.1 millimeters, the conversion goal could be met using only 13 fuel assemblies, a savings of 4 assemblies. Additionally, by changing the locations of some of the beryllium reflector blocks, designers were able to increase neutron flux densities in key locations in the reactor core to better suit experimental needs.

MURR

MURR is a high-performance research reactor with a very compact core (core volume of only 33 liters with 4.3 liters of fuel meat) with a peak thermal flux of about 6.0 × 1014 n/cm2-s (Figure 2-5). The reactor is

image

FIGURE 2-5 Photo of the MURR reactor core. SOURCE: Roglans (2011).

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

refueled weekly to maintain a greater than 90 percent capacity factor for efficient production of medical isotopes.

Conversion studies for this reactor showed that if the fuel geometry was unchanged, conversion using UMo monolithic LEU fuel would result in a harder neutron spectrum and, thus, increased power in some regions of the reactor. A means to control this higher power density needed to be identified for conversion to become possible.

The reactor fuel plates are curved, and there is no flexibility to rearrange them to reduce power peaking. However, it was determined that by using four distinct thicknesses of fuel meat in the assemblies (ranging from 0.23-0.43 millimeters), peaking factors could be reduced to acceptable levels.

Belgian BR2

The Belgian BR2 reactor typically operates at 50-80 MW with a peak thermal flux of about 0.8-1.1 × 1015 n/cm2-s. The fuel consists of curved plates that are swaged together at stiffener joints to form six concentric tubes. The fuel meat is 93 percent enriched uranium containing integrated boron and samarium burnable poisons.

The reactor is planned to be converted using a 19.75 percent enriched UMo dispersion LEU fuel. However, integrating a burnable poison into these fuel plates will be difficult owing to the high-volume fraction of UMo in the dispersion. Consequently, the reactor operator plans to install cadmium wires in the swage joints between the curved fuel plates to control reactivity, a technique that has been used successfully in some other conversions to silicide fuel.

RHF

RHF has a maximum power of 58 MW and a peak thermal neutron flux of about 1.5 × 1015 n/cm2-s. The core consists of a one-time-use assembly consisting of 280 curved plates arranged between two concentric cylindrical “sideplates.” The reactor is currently fueled with a 93 percent enriched UAlx-aluminum dispersion fuel with boron-10 burnable poisons at the tops and bottoms of the fuel plates.

This reactor is used as a neutron beam source, and a key requirement for conversion is the preservation of “brightness” (i.e., intensity) of these beams and the reactor cycle length. To meet these objectives, the fueled height of the reactor core will be increased by eliminating the burnable poison zones at the tops and bottoms of the fuel plates. (These poisons will be moved to another location in the reactor.) However, even with this change there will still be a 5-10 percent loss in brightness at key experimental

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

positions. This loss of brightness can be compensated for by increasing the beam times for some experiments, but it will not affect overall throughput of experiments in the reactor.

Russian Viewpoint on Core Modifications

I.T. Tetiyakov

When converting a research reactor from HEU to LEU fuel it is important to avoid degradation of the following:

•  Consumer characteristics: neutron flux level, thermal power, neutron spectrum, and adequacy of safety systems.

•  Safety characteristics: reactivity margins, effectiveness of control rods, and peak power density.

•  Performance characteristics: fuel cycle duration, number of planned reactor shutdowns, and reactor serviceability.

•  Technical and economic indices: mass of uranium loading, volume of spent fuel to be reprocessed, and financial expenditure for fuel purchase and reprocessing of spent fuel.

There are two potential paths for converting a research reactor while maintaining these characteristics. One path is to design a new core that can fit into the existing reactor. The other path is to maintain the geometric configuration of the current core but change the design and arrangement of fuel and/or reflector elements.

Conversion to LEU fuel may result in decreased uranium-235 content and will result in increased uranium-238 content in the reactor core. This can change the neutronic characteristics of the core, which in turn can change its reactivity, the effectiveness of control rods, and the dynamics of fuel burnup. All of these changes can affect reactor safety. Consequently, safety analyses must be carried out to demonstrate that conversion will preserve reactor safety at required levels, including neutron-physical analysis, thermal-hydraulic analysis, and an analysis of transient and emergency operations.

As illustrated by the following three examples, for some Russian research reactors there are no developed LEU fuel elements that would enable conversion with acceptable consumer characteristics. Moreover, some Russian research reactors are approaching the ends of their operating lives, and there is a need to consider whether to shut down these reactors or modernize them.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

IRT (Moscow Engineering and Physics Institute)

The IRT is a medium-flux, 2.5 MW pool-type reactor with a square core containing 16 IRT-3M fuel elements enriched in uranium-235 to 90 percent. Initial studies have been carried out to examine the feasibility of converting this reactor to 19.75 percent enriched fuel elements of an IRT-4M design containing a UO2-aluminum dispersion fuel meat.

These studies indicate that conversion would result in some consumer and economic penalties compared to HEU fuel: neutron flux densities in the fuel and reflector regions would decrease by 20-30 percent and 10-20 percent, respectively, and the number of fuel elements in the core would increase by 2-4 elements.9 The economics of conversion will depend on the cost of LEU fuel elements and their reprocessing compared to the costs for HEU fuel elements.10 However, there would be no unacceptable changes in safety characteristics, and fuel burnups would not change.

IVV-2M (Institute of Nuclear Materials, Zarechny)

The IVV-2M is a high-flux, 15 MW pool-type reactor with a hexagonal core containing 42 hexagonal fuel elements enriched in uranium-235 to 90 percent. Initial studies have been carried out to examine the feasibility of converting this reactor to 19.75 percent enriched fuel containing a UO2-aluminum dispersion fuel meat.

This reactor is being very effectively operated at present and has a high level of utilization, so any significant loss of consumer characteristics following conversion would be problematic. Initial conversion studies have focused on identifying a fuel type that would meet consumer needs. Analytical studies have examined the reactor characteristics that would result from conversion to dispersion fuels having uranium densities of 3.5 and 6.5 gU/cm3 as well as a UMo-aluminum dispersion fuel.

Conversion to a 3.5 gU/cm3 fuel that was manufactured using existing (extrusion-based) fuel fabrication technologies would result in insufficient reactivity reserve and the deterioration of other consumer characteristics such as burnup. Conversion using 6.0-6.5 gU/cm3 fuel would improve the feasibility of conversion if fuel elements with such material were able to be manufactured economically.

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9 This conclusion was reached by studying the use of existing IRT-4M LEU fuel. A feasibility study with the IRT-3M UMo fuel of higher density, currently under development, is under way at MEPhI (see Chapter 3) and may reach different conclusions when completed.

10 In Russia, reprocessing costs are based on fuel mass.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

WWR-M (Petersburg Nuclear Physics Institute, Gatchina)

The WWR-M is an 18 MW pool-type reactor with a hexagonal core containing 145 fuel elements of WWR-5M design that are enriched in uranium-235 to 90 percent (Figure 2-6). Although this reactor entered service in 1959, it is still operating very effectively and has achieved several increases in power and flux densities since it was commissioned. It is now the highest power reactor of its type in existence.

Initial studies have been carried out to assess the feasibility of converting this reactor to 36 percent enriched and 19.75 percent enriched fuel. It was observed that as enrichments decrease, burnups, thermal neutron flux densities, and fast neutron flux densities also decrease. These studies indicate that fuel having a uranium density of 8.25 gU/cm3 would be required to convert this reactor without sacrificing needed consumer characteristics. However, fuels with this density are not available at present.

MAINTAINING PERFORMANCE AND MISSIONS

Two presentations discussing performance and missions of reactors after conversion were given by Panel 2.1 speakers: Jordi Roglans (Argonne National Laboratory) provided a U.S. viewpoint on maintaining performance and missions (Roglans, 2011), and A.L. Petelin (Research Institute of Atomic Reactors [RIAR]) provided a description of several Russian research reactors at RIAR and their missions (Svyatkin et al., 2011).

U.S. Viewpoint on Maintaining Performance and Missions

Jordi Roglans

The Global Threat Reduction Initiative (GTRI) strives to achieve several goals when converting research reactors:

•  Develop or identify an LEU fuel assembly that is acceptable for conversion.

•  Ensure that the ability of the reactor to perform its scientific mission is not significantly diminished.

•  Ensure that conversion can be achieved without requiring major changes in reactor structures or equipment.

•  Demonstrate that the LEU fuel meets all safety requirements and that conversion and subsequent operations can be accomplished safely.

•  Ensure that annual operating costs do not increase significantly as the result of conversion.

•  Develop a conversion schedule that is based on operational requirements, capabilities, and regulatory processes.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

image

FIGURE 2-6 Schematic illustration of the WWR-M reactor core. SOURCE: Tetiyakov (2011).

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

As noted in John Stevens’ presentation (summarized elsewhere in this chapter), a fuel assembly is considered to be acceptable for use in a conversion project when it meets the following criteria and the reactor operator and regulator agree to accept fuel assembly for conversion:

•  Qualified: The fuel assembly has been successfully irradiation-tested and is licensable.

•  Commercially available: The fuel assembly is available from a commercial manufacturer.

•  Suitable: The fuel assembly satisfies the criteria for LEU conversion of a specific reactor; safety criteria are satisfied; fuel service lifetime is comparable to current HEU fuel; and the performance of experiments is not significantly lower than for HEU fuel.

When converting from an HEU to LEU fuel, one should strive to make as few changes as possible in the fuel assembly and core geometries. Conversion should also be carried out in a way that has the least possible effect on scientific operations in the facility.

The annual operating costs of a reactor will be affected by the costs of the LEU fuel assemblies compared to the HEU fuel assemblies they are replacing. The new very-high-density UMo fuels will likely cost more to fabricate because there are more manufacturing steps. However, work is under way to minimize those cost differences with the goal of maintaining or even reducing when feasible the number of LEU fuel assemblies that are consumed in a reactor each year compared to HEU fuel assemblies.11 The number of fuel assemblies consumed per year dominates costs when LEU and HEU fuel assemblies are of similar cost.

Analytical studies are typically needed to determine whether conversion can be accomplished without a significant impact on reactor performance and missions. However, such formal studies may not be required for HEU-fueled reactors that are of a similar type and performance to reactors that have already been converted to LEU.

The analytical studies needed to assess the potential for conversion include:

•  Feasibility studies that identify suitable LEU fuel assemblies (either existing qualified fuels or new fuels under development), compare reactor performance with HEU and LEU fuels, and calculate key safety parameters.

•  Operational and safety analyses to demonstrate that the transition from HEU to LEU fuel can be done safely and without interrupting normal

________________

11 Service lifetimes of LEU fuel assemblies can be increased if the uranium-235 loadings are higher than comparable loadings in the HEU fuel.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

reactor operations, and also that the converted reactor satisfies all safety requirements.

One also needs to formulate safety requirements and resolve any issues raised by regulators regarding the reactor’s safety documentation. Additionally, economic impact studies may be required to determine the overall impact and acceptability of conversion.

A feasibility study entails many activities. Initially, fuel requirements and experimental performance indicators must be defined. With respect to the latter, it is important to determine what the most important experimental positions are in the reactor and what performance characteristics (e.g., flux densities and neutron energy distributions) are required in those positions. Iterative modeling studies are used to determine these characteristics as well as other operating criteria such as shutdown margins. Fuel assembly and reactor core designs are adjusted, and the models are rerun until acceptable performance and other important reactor characteristics are achieved. The final LEU fuel assembly design can be selected once these studies are completed.

Some high-performance reactors may require fuel-design optimization and possibly facility-specific mitigation measures to address any performance penalties arising from conversion. For U.S. high-performance reactors, the anticipated unmitigated decreases in performance resulting from conversion do not preclude any current applications but could affect application throughputs. The high demand for these reactors is already limiting scientific output and isotope production. Consequently, several mitigation strategies are being pursued to avoid throughput penalties.

For the U.S. high-performance reactors, the following mitigation strategies are being pursued:

•  HFIR: The anticipated performance penalty of 10-15 percent will be mitigated by increasing reactor power from 85 MW to 100 MW. This could result in small gains in performance.

•  MITR: The anticipated performance penalty of 5-10 percent will be mitigated by increasing reactor power from 6 MW to 7 MW.

•  MURR: The anticipated performance penalty of 15 percent will be mitigated by changing LEU plate thickness (see the presentation by John Stevens elsewhere in this chapter) and by increasing reactor power from 10 MW to 12 MW.

•  NBSR: The anticipated performance penalty of 10 percent will be mitigated by upgrading the cold neutron source.

Power increases in HFIR, MITR, and MURR are possible because their existing cooling systems are adequate to handle the increased heat loads. As

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

a result of these mitigation strategies, no current applications are expected to be precluded by conversion. In ATR, preliminary studies indicate that there could be a 5-10 percent performance penalty after conversion. A strategy to mitigate this penalty has not yet been identified.

The key to successful conversion is collaboration. In the case of high-performance reactors or reactors with unique designs, iterative collaborations among facility operators, fuel designers, and conversion analysts are essential to optimize fuel and core design and minimize performance impacts.

Descriptions of Russian Research Reactors

A.L. Petelin

The Russian presentation focused on current characteristics and missions of the research reactors at RIAR in Dimitrovgrad. RIAR is Russia’s largest complex for examinations of full-scale components of nuclear reactors and irradiated materials. It also has equipment and facilities for fuel cycle research and a radiochemical complex for investigation and production of transuranic elements and radioisotopes.

RIAR currently operates five research reactors. A sixth reactor is being decommissioned. The characteristics and missions of the operating reactors are described briefly in the following sections.

SM-3

SM-3 is a 100 MW pressurized water flux trap-type reactor containing 32 fuel elements enriched in uranium-235 to 90 percent. The reactor has a compact square core (420 mm in plan dimension and 350 mm in height) with a central trap. Up to 41 positions are available for irradiation experiments in the central trap, core, and reflector. The maximum thermal neutron flux density in the central trap is 5 × 1015 n/cm2-s. Thermal neutron flux densities of 1.5 × 1013 to 1.5 × 1014 n/cm2-s can be obtained in the reflector.

The reactor has two low-temperature coolant water loops and a high-temperature loop that can be used for fuel testing, examination of fission-product releases from leaky fuel rods and their removal from primary cooling circuits, and the irradiation of structural and absorbing materials. The spectral characteristics and neutron-flux-density variability in this reactor also make it useful for producing a range of isotopes, including transplutonium elements and industrial isotopes such as cobalt-60.

This reactor is potentially useful for other high-dose irradiation applications, for example, testing of fuel and structural materials for high-

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

temperature reactors, fast-boiling reactors, and supercritical reactors, as well as new designs for research reactors. In particular, new LEU fuel compositions can be examined for applications in high-flux reactors. The reactor can also be used for training.

MIR.M112

MIR.M1 is a 100 MW loop-type reactor that uses 48-58 fuel elements enriched in uranium-235 to 90 percent (see Figure 3-8 in Chapter 3). It has seven loop facilities: Two with water coolant (PV-1, PV-2), two with water/boiling-water coolant (PVK-1, PVK-2), two with water/boiling water and steam coolant (PVP-1, PVP-2), and one with nitrogen and helium coolant (PG). The facility also contains hot cells and cooling pools. The maximum thermal neutron flux in the loop channel is 5-7 × 1014 n/cm2-s.

A variety of experimental activities are currently performed in this reactor. These include the examination of advanced VVER-1000 fuel, testing of VVER-1000 fuel with high burnup (greater than or equal to 60 megawatt days per kilogram of uranium [MWd/KgU]), testing of new VVER cladding materials, and examination of fission-product releases from VVER-1000 fuel rods containing artificial defects. The reactor is also used to test LEU fuel and produce the industrial isotope iridium-192.

This reactor is potentially useful for other types of experimental applications, including high-temperature and high-pressure testing of reactor materials, simulation of severe reactor accidents, testing of innovative fuel and cladding materials, and expanded production of isotopes. Realizing some of these activities would require upgrades to some of the reactor loops.

RBT-6 and RBT-10/2

The RBT-6 and RBT-10/2 reactors are pool-type reactors of similar design. The RBT-6 operates with 56 fuel elements at a power of 6 MW, whereas RBT-10/2 operates with 78 fuel elements at a power of 10 MW. Both reactors have neutron flux densities of about 1 × 1014 n/cm2-s. The fuel for both reactors is UO2 dispersed in a copper-beryllium matrix enriched to 90 percent.

Although these reactors operate at full power most of the time, their experimental channels (up to 8 for RBT-6, slightly more channels for RBT-10/2) only have about 50 percent utilization. There is interest in increasing the usage of these reactors. Possible additional experimental activities

________________

12 This reactor is also discussed in another symposium presentation that is summarized in Chapter 3.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

include silicon doping, isotope production (including molybdenum-99 production), testing of industrial materials, and neutron capture therapy. Some of these activities would require redesign of the experimental channels.

BOR-60

BOR-60 is a 60 MW sodium-cooled fast reactor that can produce up to 12 MW of electricity. It is fueled with UO2 or UO2-PuO2 fuel with uranium-235 enrichments of 45-90 percent and plutonium content of 70 percent. It has a maximum neutron flux density of 3.7 × 1015 n/cm2-s.

This reactor is currently used for test irradiations of reactor fuels and materials, including new fuels, cladding, and structural materials for fast reactors, water cooled reactors, and fusion reactors. It is also being used for transmutation research, other fuel cycle research, and isotope production. The experimental applications could be expanded to include advanced reactor and fuel cycle research.

AGEING AND OBSOLESCENCE OF RESEARCH REACTORS

Two presentations on understanding and addressing the ageing and obsolescence of research reactors were given by Panel 2.2 speakers: H.-J. Roegler (an independent consultant from Germany, formerly with Siemens13) described an International Atomic Energy Agency (IAEA) initiative on research reactor ageing and ageing management (Roegler, 2011). E.P. Ryazantsev (Kurchatov Institute) provided a historical description of the research and test reactors at the Kurchatov Institute (Ryazantsev, 2011).

IAEA Initiative on Research Reactor Ageing and Ageing Management

H.-J. Roegler

The IAEA’s activities in ageing and ageing management for research reactors began in the mid 1990s. In March 1995, the IAEA issued a TECDOC report (IAEA, 1995) on how to manage ageing in research reactors. Two months following the release of this report, the IAEA sponsored a conference on research reactor ageing; the conference was held in Germany and involved more than 100 participants. In December 2008—more than a decade after publication of the TECDOC and sponsorship of the follow-up conference—the IAEA hosted an expert meeting at its Vienna headquarters to review the history of the agency’s efforts on ageing, including the ade-

________________

13 And under a Contract Service Agreement with the IAEA.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

quacy of existing documentation, and to consider whether an initiative to collect additional information was warranted.

As the result of this expert meeting, the IAEA initiated the development of a database on research reactor ageing. This database is intended to address ageing as a technical and safety issue and explicitly excludes reactor conversion to LEU fuel. Information for the database was collected from research reactor operators using a standard template that was developed by the IAEA. The template permitted the reporting of a maximum of 3 ageing problems, classified by 13 possible ageing mechanisms in 76 reactor systems arranged in 9 groups. The template provided space for descriptions of ageing problems and actions taken to mitigate or cure them. A contact address for the reporting reactor was also required.

The templates were distributed in February 2009 to 133 research reactor operators plus 28 other manufacturers and authorities. Responses from these organizations were incorporated into the database in October that same year. A total of 188 templates were initially submitted from 77 reactor facilities plus 6 other institutions (contributors were permitted to submit more than one template per facility). After review and revisions of the initial submissions, a total of 155 templates reporting on 367 ageing problems were included in the database.

There was a rather high-level of non-participation (43 percent) in this survey, which could have been caused by several factors, including language barriers, inexperience with completing these types of templates, or concern that the ageing problems might be publicly disclosed. One non-respondent justified the lack of participation as follows:

We do not have an ageing management program, because we do not have the funding for such a thing. We fix things when they break. That is unfortunately the nature of our business here due to monetary constraints. For me to fill out your template with something that is irrelevant is not worth your time, or ours. …We also do not necessarily wish to have this information be publicly available.

However, a convincing number of useful observations emerged from the template data that were submitted to the IAEA:

•  The 77 reactors represented in the template responses range from less than 5 years to more than 50 years old. The average age was 37.8 years (Figure 2-7).

•  The most frequently reported ageing problems were obsolescence and technology changes (92 out of 367 reports); corrosion (73 out of 367); and changes to regulatory requirements and standards (49 out of 367).

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

Other frequently reported ageing problems included mechanical fatigue and wear and radiation-induced ageing (Figure 2-8).

•  There were more ageing problems reported for younger reactors than for older reactors. This suggests that ageing problems begin with the initiation of operation of a research reactor.

Taken together, these data demonstrate the need for the future management of ageing in research reactors.

Although the database intentionally excluded information related to conversion, as noted previously, the information in the database is still potentially useful for conversion planning, because conversion needs to consider past as well as future ageing. The information in the database could be used, for example, to identify:

•  Ageing systems and mechanisms to investigate

•  Issues to discuss with the authorities

•  Contacts for advice on addressing every type of ageing problems

The IAEA is planning to undertake a first update of this ageing database in August 2011. This will involve the reconfirmation of research reactor operator contacts, updates to the content of templates, and fresh approaches to the research reactor operators who did not provide information in 2009.

image

FIGURE 2-7 Age distribution of research reactors surveyed by the IAEA. SOURCE: Roegler (2011).

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

image

FIGURE 2-8 Reported ageing mechanisms at research reactors surveyed by the IAEA.

NOTE: A = Radiation induced; B = Temperature induced; C = Creep due to stress; D = Mechanical displacement/fatigue/wear; E = Material deposition; F = Erosion; G = Corrosion; H = Damage (power excursion); I = Flooding consequences; J= Fire consequences; K= Obsolescence/technology change; L = Required/standard changes; M = Other.

Blue = Different systems (out of 76) nominated per mechanisem.

Red = Total nominated issues (out of 367) per mechanism.

SOURCE: Roegler (2011).

Reactors at the Kurchatov Institute14

E.P. Ryazantsev

The practical use of atomic energy for civilian and military purposes in the Soviet Union began with the launching of research reactor F-1 in December 1946. The reactor is graphite moderated and is fueled with 50 tonnes of natural uranium. Its operational range extends from 25 kW to 4 MW. This reactor is still operating today and is used as a reference source for neutron fluxes.

There have been a total of 80 research reactors constructed by the Soviet Union, including the following 15 reactors that were constructed in foreign countries:

•  VVR-S (2-10 MW power): Constructed in East Germany, Czechoslovakia, Romania, Poland, Hungary, and Egypt between 1957 and 1961.

________________

14 Some of the Russian reactors described in this presentation are also discussed in another presentation that is summarized in Chapter 3.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

•  IRT-2000 (2-10 MW): Constructed in China, Bulgaria, North Korea, and Iraq between 1961 and 1967.

•  TBP-C (10 MW): Constructed in China in 1959.

•  RA (10 MW): Constructed in Yugoslavia in 1959.

•  IRT-10000 (10 MW): Constructed in Libya in 1981.

•  MARIA (30 MW): Constructed in Poland in 1974.

•  IVV-9 (0.5 MW): Constructed in Vietnam in 1983.

Eleven research reactors besides F-1 have been constructed at the Kurchatov Institute:

•  RFT: Channel graphite reactor; initial power 10 MW, later upgraded to 20 MW; began operations in 1957 and was partially demolished in 1962.

•  VVR-2: Pool-type reactor; initial power 0.3 MW, later upgraded to 3 MW; began operations in 1954 and was dismantled in 1983.

•  IRT: Pool-type reactor; initial power 2 MW, later upgraded to 5 MW; began operation in 1957 and was dismantled in 1979.

•  MR: Channel-type reactor immersed in a pool; initial power of 20 MW, later upgraded to 50 MW; began operation in 1963 and was shut down in 1993.

•  Chamomile: High-temperature neutron thermoionic converter; 0.1 MW; began operation in 1964 and was shut down in 1996.

•  Hydra: Homogeneous pulse reactor; 0.01 MW (30 mega Joules per pulse); began operations in 1972 and is currently operational.

•  Yenisei: High-temperature neutron thermoionic converter; 0.1 MW; began operation in 1973 and was dismantled in 1986.

•  IR-8: Pool-type reactor; 8 MW; began operation in 1981 and is currently operational (Figure 2-9).

•  Argus: Homogeneous reactor; 0.02 MW; began operations in 1981 and is currently operational.

•  Gamma: Cabinet water-cooled reactor; 0.125 MW; began operation in 1982 and is currently operational.

•  OR (referred to as OP-M in Table 1-2 in Chapter 1): Pool-type reactor; 0.3 MW; began operation in 1989 and is currently operational.

These reactors created an experimental base for nuclear and materials research at the Kurchatov Institute.

The remainder of this presentation focused on the characteristics of the MR and IR-8 reactors at the Kurchatov Institute and activities at a branch institute in Sosnony Bory (Leningrad region).

MR was equipped with 10 experimental loops, each of which functioned as a small prototype power reactor. Several coolants were used in

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

these loops, including pressurized water, steam-water mixtures, helium, carbon dioxide, and liquid lead bismuth. The neutron flux density in the reflector was 5 × 1014 n/cm2-s. This reactor was used to work out the structure of active zones of nuclear reactors and test 400 fuel assemblies and more than 8,000 fuel rods for VVER, RBMK, ACT, high-temperature, and naval reactors.

IR-8 has a compact core with an effective reflector that provides for large thermal neutron densities of 2.3 × 1014 n/cm2-s. The core contains 12

image

FIGURE 2-9. Photograph of the IR-8 reactor at the Kurchatov Institute. SOURCE: Ryazantsev (2011).

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

experimental channels in a horizontal orientation. This reactor is used to carry out fundamental research in nuclear physics, solid state physics and superconductivity, and other experiments.

The Scientific Research Technological Institute (NITI), a branch of the Kurchatov Institute, was created in Sosnovy Bor in 1964. It has a full-scale prototype submarine reactor.

REGULATORY CHALLENGES TO CONVERSION

Two presentations on the regulatory challenges of converting research reactors were given by Panel 2.2 speakers: Alexander Adams (U.S. Nuclear Regulatory Commission) provided a U.S. viewpoint (Adams, 2011), and V.S. Bezzubtsev provided a Russian viewpoint (Bezzubtsev, 2011).

U.S. Viewpoint on Regulatory Challenges

Alexander Adams

The mission of the U.S. Nuclear Regulatory Commission (USNRC) is to ensure that the commercial use of nuclear materials in the United States is conducted safely. The USNRC is responsible for regulating civilian research reactors, including research reactor fuels and conversions, but the agency does not regulate U.S. Department of Energy (DOE) reactors.

Regulation of Research Reactor Fuel

Research reactor fuel development is the responsibility of DOE under the GTRI program. The USNRC does not get involved directly in these fuel development activities, but it does have the responsibility for approving LEU fuels for use in USNRC-licensed reactors.

USNRC approval of new LEU fuels is based on information submitted by DOE, including:

•  Results of LEU fuel development and testing.

•  Information on LEU fuel fabrication.

•  LEU fuel qualification reports.

The USNRC must conclude that an LEU fuel is suitable and acceptable for use before approving it for use in USNRC-licensed reactors. Once an LEU fuel is approved, licensees can reference the USNRC evaluation in their Safety Analysis Reports; licensees do not have to justify the generic aspects of an LEU fuel that has been approved by the USNRC. However, licensees are required to address any facility-specific issues related to use of that fuel.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

To date, the USNRC has approved three LEU fuels for use in USNRC-licensed reactors:

•  Uranium silicide (U3Si2) fuel;

•  U-ZrHx fuel for TRIGA reactors; and

•  Special Power Excursion Reactor Test (SPERT) fuel elements.

Regulation of Research Reactor Conversions

When regulatory requirements for conversion became effective there were 26 HEU-fueled civilian research reactors in the United States under the regulatory authority of the USNRC. Most of these reactors were being operated by universities. The current conversion status of these reactors is shown below:

•  Sixteen reactors were converted to LEU fuel, and five of those reactors were subsequently shut down after conversion.

•  The licenses of four reactors were terminated before conversion.

•  Decommissioning was approved for two reactors before conversion.

•  No suitable fuel has been identified for one reactor (MITR).

•  Unique purpose applications (described later) are pending for two reactors.

•  Suitable fuel has been identified but no funding is available to convert one reactor (NTR General Electric).

The first group of reactor conversions (10 reactors) was completed in 2000. The second group of reactor conversions (6 reactors) began in 2006 and was completed in 2009. In 2007, the USNRC staff turned its attention to conversion of three of the four remaining HEU-fueled reactors that it licenses, which are high-performance reactors: MITR, MURR, and NBSR.15

The Commission issued a policy statement in 1982 that fully supported the Reduced Enrichment for Research and Test Reactors (RERTR) program. Initially, many research reactor licensees resisted the call for conversion, informing the USNRC that they preferred instead to implement additional security measures at their facilities. The Commission members and staff engaged licensees through a number of outreach activities, and a Commission-sponsored LEU study group comprising licensed technical experts prepared a report on the technical feasibility of conversion.

________________

15 The USNRC does not regulate the High Flux Isotope Reactor at the Oak Ridge National Laboratory or the Advanced Test Reactor and its critical assembly at the Idaho National Laboratory. These reactors are the responsibility of DOE.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

The Commission also developed a conversion rule, which was promulgated in Title 10, Section 50.64 of the Code of Federal Regulations (10 CFR 50.64, Limitations on the Use of Highly Enriched Uranium [HEU] in Domestic Non-power Reactors) in 1986. At about the same time this rule was issued, the Commission initiated steps to reduce the amount of unirradiated HEU fuel that licensees were authorized to possess at their facilities. Licensees now minimize their onsite inventories.

The regulations in 10 CFR 50.64 prohibit new construction permits for HEU-fueled reactors unless those reactors have a “unique purpose.” It also prohibits acquisition of additional HEU fuel for current reactors if LEU fuel acceptable to the Commission is available, again unless the reactor has a unique purpose. The regulations also require reactor licensees to replace HEU fuel with LEU fuel acceptable to the Commission in accordance with an approved schedule. To be acceptable to the Commission, LEU fuel must (1) meet the operating requirements of the existing license, or (2) based on a safety review and approval by the USNRC, be used in a manner that protects public health and safety and promotes the common defense and security, and (3) limit to the maximum extent possible the use of HEU fuel.

The USNRC defines “unique purpose” as a project, program, or commercial activity that cannot be reasonably accomplished without HEU. This includes specific projects, programs, or commercial activities that significantly serve the U.S. national interest; reactor physics or reactor development; research based on HEU flux levels or spectra; or reactor cores of special design.

The Commission initially received four unique purpose applications from U.S. licensees. Two of these (for the MITR and the Cintichem Reactor16) were withdrawn, and the other two (for MURR and NBSR) have been pending for about 20 years. The Commission staff decided to defer decisions on these applications shortly after they were submitted; these decisions will continue to be deferred until a fuel acceptable to the Commission is developed for use in these reactors.

The timing of conversion depends on several factors: The availability of government funding; the availability of LEU fuel acceptable to the Commission; the availability of shipping casks to remove HEU fuel from the facility after conversion17; and the level of reactor usage.

NUREG 1537 (Guidelines for Preparing and Reviewing Applications for the Licensing of Non-Power Reactors) contains guidance for licensees to submit conversion applications to the USNRC. The conversion application must include an update of the reactor’s Safety Analysis Report relating to

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16 The Cintichem Reactor was located in Tuxedo, New York. It was shut down in 1990.

17 Depending on its design, HEU fuel is shipped to either the Savannah River Site in South Carolina (for aluminum-based fuels) or the Idaho National Laboratory (for other fuel designs), where it is stored.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

issues that are impacted by conversion to LEU. Specific areas of focus in the application include the following:

•  Reactor neutronics and thermal hydraulics: Codes and calculations that have been benchmarked against the HEU reactor should be used to analyze the LEU reactor. The licensee should show that margins of safety are maintained in the LEU reactor.

•  Reactor accidents: The licensee should reanalyze the HEU Safety Analysis Report accidents using LEU fuel to determine the impacts from conversion. Particular concerns include changes in power per fuel element, fission product inventory, and reactivity. The licensee must also perform a review to determine whether conversion to LEU fuel introduces new accident scenarios. Conversion should not have a significant impact on accident analysis results and normally should not introduce new accident scenarios.

The application also identifies all necessary changes to the license, facility, and operating procedures arising from conversion. The application must be limited to conversion and cannot include other changes or upgrades. Those are handled through the normal license amendment process.

Once the USNRC reviews and accepts an application, it issues an enforcement order directing the licensee to convert to LEU fuel and make any necessary changes to its license, facility, and procedures. By issuing enforcement orders, the USNRC assumes the burden for defending against any legal challenges that arise from conversion, thereby relieving the licensee from this responsibility.

Several lessons have been learned from the civilian research reactor conversions that have been carried out to date in the United States. First, updating the safety analyses and preparing the conversion application take time and effort and can result in the discovery of other technical issues. Second, the key to successful conversions is to develop an LEU reactor design that can be successfully analyzed and built. Finally, conversion has benefits beyond the elimination of HEU: Most notably, it can result in increased technical expertise among reactor staff and improved knowledge of reactor characteristics and operating behavior. Conversion also provides valuable training opportunities: At university reactor facilities, many students have been involved in the development of conversion analyses.

Russian Viewpoint on Regulatory Challenges

V.S. Bezzubtsev

The Russian Federation has been cooperating with the United States and the IAEA in several GTRI programs. These include the return of

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

Russian-origin HEU fuel to the Russian Federation from countries in Eastern Europe and Asia; reduction of fuel enrichment in research and test reactors; and enhancement of physical security for high-risk radioactive sources. Active international cooperation and collaboration are necessary for achieving the strategic objectives of GTRI.

ROSTEXNADZOR is the nuclear safety watchdog in the Russian Federation. It is responsible for regulating more than 6,000 facilities in the Russian Federation, including research and test reactors.18 It has three primary functions: regulatory control, licensing, and supervision of atomic energy facilities.

The federal codes and standards developed by ROSTEXNADZOR are of two types: (1) general and (2) facility specific. The agency develops and promulgates federal codes and standards for atomic energy use, administrative regulations, guidelines, and safety guides. The federal codes and standards provide general safety provisions for each type of atomic energy facility, for example, nuclear power plants, research reactors, icebreaker reactors, and nuclear fuel cycle facilities. These codes and standards also provide specific provisions for activities at these facilities including siting, construction, operation, and decommissioning.

There are 10 separate codes and standards for research nuclear installations, which include research reactors. These include, for example:

•  General Safety Assurance Provisions for Research Nuclear Installations (NP-033-01)

•  Requirements for the Content of Research Nuclear Facility Safety Analysis Reports (NP-049-03)

•  Rules of Nuclear Safety for Research Reactors (NP-009-04)

•  Requirements for a Content of Action Plan for Protection of Personnel in Case of an Accident at a Research Nuclear Installation (NP-075-06)

Many of these codes and standards draw from IAEA documents, either in full or part, the latter being adapted to local conditions.

An effort is currently under way to enhance the regulatory framework for nuclear and radiation safety at research reactors in the Russian Federation. This includes the modification of current regulatory documents and the development of new regulations. The new regulations would require periodic safety reviews of research reactors, development of rules for withdrawing research reactors from state supervision, and development of procedures for modifying the design, engineering, and operating documentation of research reactors.

________________

18 This number includes radiation sources at hospitals.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

image

FIGURE 2-10 Status of research reactors in the Russian Federation. RR = research reactors; CBs = critical assemblies; SCBs = subcritical assemblies. SOURCE: Bezzubtsev (2011).

There were 74 licensed research reactors (including critical and subcritical assemblies) in the Russian Federation in 2011. These are being operated by 19 organizations, including Rosatom and the Russian Academy of Sciences. These reactors comprise (Figure 2-10):

•  32 research reactors (24 operating, 6 decommissioned, and 2 under construction)

•  30 critical assemblies

•  12 subcritical assemblies

The average operation age of the research reactors is 24 years, but 17 reactors have been operating for more than 30 years.

ROSTEXNADZOR is just beginning to develop regulations for the conversion of research reactors in the Russian Federation. The regulator does not see any serious barriers or obstacles that might prevent conversion-related licensing activities. The USNRC’s rich experience with fuel development and conversion-related approval activities would be useful for ROSTEXNADZOR in organizing its work.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

The specific issues that will need to be addressed by ROSTEXNADZOR in research reactor conversion in the Russian Federation are the following:

•  R&D for design and fabrication of new LEU fuel, LEU fuel tests, and validation of LEU fuel characteristics and operating conditions.

•  Safety demonstrations of fabrication, transportation, storage, and disposal of new LEU fuel.

•  Analysis of flux kinetics and distribution in reactor cores with LEU fuel.

•  Thermohydraulic analysis.

•  Safety analysis, including certification of computer codes; justification of safe operation limits and conditions; accident initiators; and modification of Safety Analysis Reports, plans of personnel and public protection, quality assurance programs, and operational procedures.

•  Modification of research nuclear installation designs.

CHALLENGES POSED BY REACTORS THAT CANNOT BE CONVERTED

Two presentations on the challenges posed by research reactors that cannot be converted were given by Panel 2.2 speakers: Jeffrey Chamberlin (U.S. Department of Energy, National Nuclear Security Administration) provided a U.S. viewpoint (Chamberlin, 2011), and G. Pshakin (Institute for Physics and Power Engineering in Obninsk) provided a Russian viewpoint (Zrodnikov et al., 2011).

U.S. Viewpoint on Challenges

Jeffrey Chamberlin

GTRI is the key program within the U.S. government for implementing the U.S. policy to minimize the civilian use of HEU. GTRI’s mission is to reduce and protect vulnerable nuclear and radiological materials located at civilian sites worldwide. Its specific goals are to: (1) convert research reactors and isotope production facilities from HEU to LEU; (2) remove and dispose of excess nuclear and radiological materials; and (3) protect high-priority nuclear and radiological materials from theft and sabotage.

GTRI’s Reactor Conversion Program is focused on converting civilian research reactors worldwide to operate on LEU fuel. Its goal is to convert or verify the shutdown of 200 civilian research reactors and HEU facilities by 2020.19 However, GTRI does not specifically encourage the shutdown of

________________

19 This deadline slipped to 2022 while this report was being completed because of Fiscal Year 2011 federal budget reductions.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

research reactors; such decisions are made by facility operators. A research reactor does not have to be considered to be vulnerable to be a candidate for conversion. GTRI is focused on converting civilian reactors and HEU facilities that use HEU fuel because it provides for permanent threat reduction.

Since the inception of GTRI in 2004, 23 HEU-fueled research reactors have been converted as part of the program, including 7 research reactors in the United States and 16 research reactors in other countries.20 The most recent conversions were the Kyoto University Research Reactor in Japan (March 2010) and the Rez Reactor in the Czech Republic (April 2011).

As noted in Chapter 1, nearly all U.S. HEU-fueled reactors that can convert with existing LEU fuels have successfully been converted (see also Footnote 3 in this chapter). As noted in previous presentations, there are six HEU-fueled U.S. research reactors (ATR and its critical assembly, HFIR, MITR, MURR, and NBSR) that cannot be converted until a new LEU fuel is developed. Additionally, in December 2010, DOE and Rosatom signed an Implementing Agreement to perform feasibility studies for the possible conversion of six HEU-fueled research reactors in the Russian Federation.

The reduction of HEU use in civilian applications is supported at the highest levels in the U.S. and Russian governments. In a joint statement issued on July 6, 2009, Russian Federation President Dmitry Medvedev and U.S. President Barack Obama issued a joint statement expressing their strong support for HEU minimization:

We declare an intent to broaden and deepen long-term cooperation to further increase the level of security of nuclear facilities around the world, including through minimization of the use of highly enriched uranium in civilian applications and through consolidation and conversion of nuclear materials.

This call for minimization was echoed in UN Security Council Joint Resolution 1887, which was issued in September 2009, and in the April 2010 Nuclear Security Summit.

GTRI works in cooperation with reactor owners/operators to convert reactors to LEU fuel. This cooperation involves:

•  Performance of feasibility studies to determine if reactors can be converted and still achieve their missions without major changes in reactor structures or equipment.

________________

20 In Chapter 1, it was noted that 35 conversions or shutdowns of HEU-fueled reactors have occurred since 2004. This larger number includes 10 reactors that were shut down and 2 reactors that were converted to LEU under domestic programs rather than GTRI.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

•  Ensuring that required fuel assembly criteria for LEU conversion are satisfied; LEU fuel provides a similar service lifetime as the HEU fuel; there is no significant penalty in reactor performance; and safety criteria are satisfied.

•  Development of a schedule for conversion based on operational requirements, capabilities, and regulatory processes.

•  Demonstrating that conversion and subsequent reactor operations can be accomplished safely.

•  Determining, to the extent possible, that overall costs associated with conversion do not significantly increase the annual operating expenditures for reactor owners/operators.

•  Obtaining/verifying that agreements and authorities are in place to proceed with conversion.

GTRI’s starting assumption for reactor conversions is that “anything is possible.” The experience gained from previous conversions demonstrates that there are many ways to overcome technical barriers. Indeed, many of the recent successful conversions of U.S. reactors were not thought to be possible 20-30 years ago.

Although GTRI policy is to take all reasonable steps to convert facilities and reduce the use of HEU, there may be some facilities that are not feasible to convert. For example, a feasibility study for a particular reactor might indicate that conversion is not feasible because LEU fuel assembly criteria are not satisfied and a unique fuel development effort is not technically or economically feasible. This might be the case for fast reactors, fast critical assemblies, or HEU reactors with very small core volumes.

In such cases, there are four options for addressing HEU minimization at such facilities:

•  Option 1: Assess the possibility of changing the facility mission such that it can be accomplished with LEU fuel. However, GTRI does not advocate a change of reactor mission for the sole purpose of converting.

•  Option 2: Reduce HEU enrichments. This may be technically feasible in some cases where LEU conversion is not. Note, however, that reduced enrichments above 20 percent are not considered HEU minimization under international norms or GTRI policy.

•  Option 3: Shut down the facility or consolidate it with similar facilities if it is underutilized.

•  Option 4: If no other options exist for the facility other than to operate with HEU, remove all excess HEU and enhance physical protection measures to achieve threat reduction.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

GTRI considers each of these options to be “last resort” and does not endorse them as a matter of policy. These options must be considered on a case-by-case basis by the facility and the host government.

Russian Viewpoint on Challenges

G. Pshakin

The BFS-1 and BFS-2 critical assemblies21 at the Institute for Physics and Power Engineering in Obninsk (Figure 2-11) provide a good example of reactors that cannot be converted to LEU fuel. These reactors, which are fueled with HEU and plutonium, were constructed in the late 1950s and early 1960s as part of the Soviet Union’s fast breeder program for nuclear energy development. Although these assemblies cannot be used for designing commercial-scale fast breeder reactors, they are useful for simulating fast breeder reactor cores, for fuel cycle research, and for studying the transmutation of minor actinides. This fuel used in these assemblies is not self-protecting22 and therefore poses special security concerns.

Converting these facilities to LEU fuel cannot be accomplished without sacrificing the current mission. Moreover, even if the uranium enrichment of the fuel could be reduced, plutonium would still be required to simulate the cores of fast breeder reactors.

There are two options for addressing the security concerns associated with these facilities: (1) shut down the facility and remove all nuclear materials; or (2) organize a state-of-the-art materials protection, control and accounting (MPC&A) system and enhance the culture of personnel through proper training, motivation, and support. The second option is obviously preferable.

The facility has cooperated with the United States to develop an MPC&A system. It includes a non-destructive analytical system based on high-resolution germanium detectors for isotopic measurement of accounted items; neutron coincident counters for nuclear material mass measurements; and specially designed access and monitoring systems. This program has to protect more than 100,000 HEU and plutonium discs that are used to model the cores of fast breeder reactors.

________________

21 As noted in Chapter 1, a critical assembly contains sufficient fissionable and moderator material to sustain a fission chain reaction at a low (close to zero) level. It is designed so that fissionable and moderator materials can be easily rearranged in various geometries to mock up different reactor designs.

22 As noted in Chapter 1, a material is considered to be “self-protecting” if it produces a dose rate greater than 100 rad per hour at 1 meter in air. These high levels create substantial radiological barriers to illicit use.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

image

FIGURE 2-11 Photograph of a BFS critical assembly (BFS-1). SOURCE: Zrodnikov et al. (2011).

DISCUSSION

Time was set aside during this session for free discussion among symposium participants. Some of the key comments from that discussion are presented in this section.

•  Research reactors will continue to be an essential tool for many applications. B. Myasoedov commented that he expected the role of research reactors to grow in the future to support the development of more complex reactor designs for nuclear power plants, including those based on fast reactor designs; for radiopharmaceutical production; and for analytical methods (such a neutron activation analysis) to support safety monitoring and control. He suggested that Russia and the United States should agree to work together and with third-party countries to design a standardized research reactor that could be produced on an industrial basis. This would eliminate the need to design individual, customized cores and fuel elements.

•  Past experience suggests that successful conversion solutions can be found for most reactors. Jim Snelgrove commented that in view of the success that has occurred in converting reactors in the United States and some other countries, a key take-away message from this symposium should be that it is possible to find conversion solutions if one works hard enough to uncover them. Yu.S. Cherepnin added that some of the presentations in this session documented how enrichment levels could be reduced without degrading reactor performance. These examples should be publicized. H.-J. Roegler commented that conversion can result in improvements to reactors.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

•  Current work under way in Russia on monolithic fuel development could pave the way for conversion of many Russian research reactors. Jim Matos commented that the densities of the LEU dispersion fuels described in the Russian presentations are too low to be used in converting many Russian reactors. Jim Snelgrove noted that monolithic pin-type LEU fuel is also being tested in Russia. This fuel is a potential replacement for the tube-type fuel that is now being used in Russian research reactors. The recent agreement between DOE and Rosatom to assess the feasibility of converting six Russian research reactors could play an important role in assessing the potential utility of this LEU fuel.

•  There may be some research reactors that cannot be converted. V. Ivanov noted that there may be some reactors with unique purposes that cannot be converted. For example, the multipurpose fast breeder reactor to be built in Dimitrovgrad will be fueled with HEU and plutonium. The concept of reducing risk by eliminating HEU does not make sense for this reactor because the HEU is used alongside plutonium. This is also true for critical assemblies. He also noted that the concept of “unique mission” has not yet been defined in Russia, and he suggested that there should be a limited list of parameters that could be applied to determine uniqueness. N.V. Arkhangelsky reminded symposium participants that it was recognized from the very beginning of the RERTR program that there are a number of research reactors that would not lend themselves to conversion, including fast breeders.

•  Reactor ageing is a potential complication for conversion, but it can be managed. V. Ivanov noted that unless national regulatory requirements dictate conversion, the decision to convert, upgrade, or shut down a reactor will be made by the operator/owner. The owner/operator must determine whether it makes sense to convert the reactor if the remaining lifetime is negligible. H.-J. Roegler commented that, in his experience, research reactor ageing problems can be cured, although in some cases it can take time. A.N. Chebeskov commented that different reactor facilities may have access to different resources to manage ageing. Having a set of best practices to manage ageing could be a topic for international cooperation.

•  Reactor customers (users) are an important part of the conversion process. V. Ivanov commented that conversion work needs to be transparent to customers, not just designers and research reactor specialists. He suggested that it would make sense for the international community, including the customers of research reactors, to cooperate more closely on conversion.

•  There may be economic advantages to conversion. Richard Meserve noted that conversion may have economic advantages that were not discussed by any of the symposium presenters. In particular, LEU costs could be lower, depending on how that material is priced, and costs for securing

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

LEU fuel should be much lower than for HEU fuel. Jordi Roglans commented that transportation costs, especially international transportation costs, will be lower for LEU fuel because HEU is often transported by the military.

•  A worldwide ethic on conversion should be developed. Yu.S. Cherepnin suggested that the world community should develop a new ethic against operating reactors with HEU. Strong signals should be sent to operators of HEU reactors that they need to convert, and funding should be demanded from governments to support conversion.

•  Working together, the Russian Federation and the United States have played and will continue to play important global roles in research reactor conversion. N. Laverov noted that the Russian Federation has decommissioned 200 nuclear submarines and, working with the United States, has returned 100,000 tonnes of natural uranium and 500 tonnes of HEU from foreign countries. The recent agreement between DOE and Rosatom to assess the feasibility of converting six Russian research reactors is an important step for eliminating HEU use in Russian research reactors. It is important that the Russian Federation and the United States serve as an example to countries by reducing the enrichments of their research reactors to lower levels.

REFERENCES

Adams, A. 2011. Regulatory Challenges and Solutions: High-Enriched to Low-Enriched Uranium Fuel Conversion. Presentation to the Research Reactor Conversion Symposium. June 9.

Bezzubtsev, V. 2011. Regulating Safe Operation of Russian Research Reactors. Presentation to the Research Reactor Conversion Symposium. June 9.

Chamberlin, J. 2011. Challenges Posed by Research Reactors That Cannot be Converted (U.S. Viewpoint). Presentation to the Research Reactor Conversion Symposium. June 9.

Cherepnin, Yu. 2011. Experience of Resolving the Problems Arising in Conversion of Research Reactors. Presentation to the Research Reactor Conversion Symposium. June 9.

IAEA [International Atomic Energy Agency]. 1995. Management of Research Reactor Ageing. IAEA-TECDOC-792. Vienna: International Atomic Energy Agency.

Roegler, H. 2011. Obsolescence & Ageing: Findings from the IAEA Initiative on Research Reactor Ageing and Ageing Management. Presentation to the Research Reactor Conversion Symposium. June 9.

Roglans, J. 2011. Maintaining Performance and Missions (U.S. viewpoint). Presentation to the Research Reactor Conversion Symposium. June 8.

Ryazantsev, E. 2011. Ageing and Obsolescence of Research Reactors. Presentation to the Research Reactor Conversion Symposium. June 9.

Stevens, J. 2011. Core Modifications to Address Technical Challenges of Conversion. Presentation to the Research Reactor Conversion Symposium. June 8.

Svyatkin, M.N., Izhutov, A.L., and Petelin, A.L. 2011. Use of Research Reactors of Scientific Centre RIAR. Presentation to the Research Reactor Conversion Symposium. June 8.

Tetiyakov, I.T. 2011. Modification of the Reactor Cores. Presentation to the Research Reactor Conversion Symposium. June 8.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×

Wachs, D. 2011. Research and Test Reactor Fuel System Development. Presentation to the Research Reactor Conversion Symposium. June 8.

Zrodnikov, A., Pshakin, G., and Matveenko, I. 2011. Research Reactors That Cannot be Converted. Presentation to the Research Reactor Conversion Symposium. June 9.

Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×
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×
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×
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
×
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Suggested Citation:"2 Challenges and Opportunities Associated with Conversion." National Research Council. 2012. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors: A Workshop Report. Washington, DC: The National Academies Press. doi: 10.17226/13346.
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Highly enriched uranium (HEU) is used for two major civilian purposes: as fuel for research reactors and as targets for medical isotope production. This material can be dangerous in the wrong hands. Stolen or diverted HEU can be used-in conjunction with some knowledge of physics-to build nuclear explosive devices. Thus, the continued civilian use of HEU is of concern particularly because this material may not be uniformly well-protected. To address these concerns, the National Research Council (NRC) of the U.S. National Academies and the Russian Academy of Sciences (RAS) held a joint symposium on June 8-10, 2011.

Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors summarizes the proceedings of this joint symposium. This report addresses: (1) recent progress on conversion of research reactors, with a focus on U.S.- and R.F.-origin reactors; (2) lessons learned for overcoming conversion challenges, increasing the effectiveness of research reactor use, and enabling new reactor missions; (3) future research reactor conversion plans, challenges, and opportunities; and (4) actions that could be taken by U.S. and Russian organizations to promote conversion. The agenda for the symposium is provided in Appendix A, biographical sketches of the committee members are provided in Appendix B, and the report concludes with the statement of task in Appendix C.

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