Reducing the Use of Highly Enriched Uranium in Civilian Research Reactors (2016)

1

Background and Study Task

This report assesses the status of and progress toward eliminating the worldwide use of highly enriched uranium (HEU) fuel in civilian research and test reactors. Elimination of HEU¹ fuel in research and test reactors (hereafter, referred to as simply “research reactors”²) is one of several efforts that support the nuclear nonproliferation goal of minimizing or eliminating the use of weapon-usable nuclear material in civilian applications. The main civilian applications that use special nuclear material (primarily HEU) are research reactors, targets for medical isotope production, and propulsion systems for remote missions. Research reactors use HEU-based fuel to achieve a large flux of neutrons with which to perform basic research, materials studies, and materials production. Molybdenum-99 (⁹⁹Mo), the precursor of the most commonly used medical isotope, is produced primarily by irradiating HEU targets.³ Propulsion systems designed for long-duration, remote missions (e.g., missions involving spacecraft or

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¹ HEU is defined as uranium enriched to 20 percent or higher in the isotope ²³⁵U; weapon-grade HEU (W-HEU) is enriched to 90 percent or higher (e.g., see Glaser, 2006).

² The U.S. Nuclear Regulatory Commission (USNRC) differentiates between a research and a test reactor by thermal output power level; research reactors operate at 10 megawatts or less, and test reactors operate above this level. For the purposes of this report, this differentiation is not important. For more information on the USNRC’s regulation of research and test reactors, see http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/research-reactors-bg.html.

³ A common medical isotope used for medical diagnostic studies is a metastable state of technetium (technetium-99m, ^99mTc). ^99mTc can be produced by irradiating HEU targets in reactors, resulting in the fission of ²³⁵U to molybdenum-99 (which has a 66-hour half-life), which in turn decays to ^99mTc (with a 6-hour half-life).

icebreakers) use HEU-fueled nuclear reactors as a long-lived steady power source. Of these three main applications, research reactors use the vast majority of civilian HEU.

Compared to nuclear power reactors, research reactors require far less fuel and operate at much lower power levels and temperatures. However, to accomplish their basic mission of producing large numbers of neutrons over a sustained period of time, HEU fuel is used because, with currently qualified fuels, it allows for the design of compact reactors with higher neutron fluxes.

Research reactors are used for training and education, irradiation of materials, and extracted beam applications (IAEA, 2014). Training and educating the next generation of nuclear scientists and reactor operators is their most common mission and therefore many of them are located at universities. Irradiation of samples and materials within and near the core of the research reactor is important for materials testing and applications that require transmutation⁴—the changing of one element into another, in this case induced by the radiation inside the reactor. Irradiating materials in the intense radiation environment of a research reactor reveals how their engineering properties (e.g., strength, swelling, and ductility) change and deteriorate under such conditions, a critical test for selecting and qualifying the materials needed to safely harness nuclear power. The production of radioisotopes through transmutation is useful in industry and medicine. In extracted beam applications, neutrons emitted from the core of a reactor travel through beam tubes to experimental stations outside of the core, where they can be used for basic scientific studies of materials under a wide variety of temperatures, pressures, magnetic fields, and other relevant conditions, as discussed in Chapter 3.

A large neutron flux is essential for most of these applications, whether for efficient material production or usable signal-to-noise ratios in scientific investigations. The high density of ²³⁵U in an HEU reactor fuel leads to a compact core and enables high neutron flux per gram of material, making it an attractive fuel for these applications. Unfortunately, this same property makes HEU attractive as the core component in a rudimentary nuclear weapon.

Since the late 1970s, government and international programs have aimed to reduce the use of HEU fuel in research reactors (see details of these programs in Chapters 2 and 5). These programs have focused on the conversion of reactor fuel from HEU to low enriched uranium (LEU).⁵ From a non-

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⁴ Transmutation occurs when a neutron bombarding an atomic nucleus is absorbed, changing it into a different isotope of the same element, or when a nucleus fissions, producing two or more different elements. Other processes are involved in transmutation; see Glossary for a more detailed definition.

⁵ LEU is defined as uranium enriched to less than 20 percent in the isotope ²³⁵U.

proliferation standpoint, the closure of an HEU-fueled reactor would accomplish the same goal. However, conversion programs seek the cooperation of the operators via assurances or incentives to maintain performance and operating costs. Closure or shutdown is not a goal of conversion programs, but it may be an unintended consequence once decision or policy makers consider nonproliferation goals, conversion costs, or reactor aging (see Chapter 2).

MOTIVATION FOR THE STUDY

This study was mandated by Congress in the American Medical Isotopes Production Act of 2012. Section 3178 of the act states

The Secretary [of Energy] shall enter into an arrangement with the National Academy of Sciences [the Academies] to conduct . . . an assessment of the progress made by the Department [of Energy] and others to eliminate all worldwide use of highly enriched uranium in reactor fuel, reactor targets, and medical isotope production facilities.⁶

During negotiations between the National Academies of Sciences, Engineering, and Medicine (the Academies) and the National Nuclear Security Administration (NNSA),⁷ it was agreed that two studies would be conducted to support this mandate: one on medical isotope production without HEU targets and the other on the conversion of research reactors to LEU. These studies were separated because efforts to eliminate HEU use in research reactor fuel and medical isotope production targets are proceeding along independent lines, engage largely different technical communities, and confront different technical, economic, and regulatory challenges. The status of and progress toward the production of medical isotopes without the use of HEU is the subject of a separate but parallel Academies study and report.⁸ The statement of task for the research reactor conversion study was developed to be consistent with the congressional mandate and analogous to the medical isotope study. The statement of task can be found in Box 1.1 and in Appendix A.

STRATEGY TO ADDRESS THE STUDY CHARGE

This study was carried out by a committee of experts appointed by the Academies. The committee consists of 10 members and 1 technical consul-

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⁶ The full text of the bill pertinent to this study is available at http://www.gpo.gov/fdsys/pkg/BILLS-112hr4310enr/pdf/BILLS-112hr4310enr.pdf (accessed December 15, 2014).

⁷ The NNSA is a semi-autonomous agency within the Department of Energy (DOE) and is the organization sponsoring this study.

⁸ Information about the study can be found at http://www8.nationalacademies.org/cp/projectview.aspx?key=49673.

tant with expertise that spans the issues relevant to the study task: materials science; nonproliferation policy; nuclear engineering; research reactor fuel design, fabrication, and qualification; reactor operations; research reactor performance analysis (e.g., neutronics, thermal hydraulic analysis, accident analysis); and research reactor regulation. In selecting the membership of this committee, the Academies sought to obtain a balanced committee composed of members with relevant disciplinary expertise and no current connection to the NNSA’s Office of Material Management and Minimization (M³) or nuclear regulatory agencies. The committee chair is an academy member with demonstrated leadership capabilities, but she has no direct experience in nuclear research reactor conversion or fuel development. Biographical sketches of the committee members and technical consultant are provided in Appendix B.

The committee contacted a broad variety of parties and agencies to obtain information to address its study charge. The committee held seven meetings to receive information from subject matter experts, representatives from research reactor facilities, user communities, and federal agency staff (Appendix C). A joint International Atomic Energy Agency (IAEA) and Academies meeting was held to develop a publicly available list of existing

civilian research reactors worldwide currently using HEU fuel.⁹Appendix E provides a synopsis of the joint IAEA–Academies meeting and the resulting list of HEU-fueled research reactors.

Committee members toured domestic research reactor facilities in conjunction with their data-gathering sessions: the Advanced Test Reactor (ATR), its critical assembly (ATR-C), and the Transient Reactor Test Facility in Idaho Falls, Idaho; the University of Missouri Research Reactor in Columbia, Missouri; the Neutron Beam Split-Core Reactor at the National Institute of Standards and Technology Center for Neutron Research in Gaithersburg, Maryland; the High Flux Isotope Reactor and the Spallation Neutron Source in Oak Ridge, Tennessee; and the Y-12 National Security Complex LEU fuel fabrication line, also in Oak Ridge. A subgroup of the committee¹⁰ toured Babcock and Wilcox Technologies’ (BWXT’s) fuel fabrication facility and new production line for uranium-molybdenum (UMo, also known as “U-moly”) monolithic fuel in Lynchburg, Virginia.

Other subgroups of the committee toured a variety of foreign reactors: the MARIA reactor in Poland¹¹; the Forschungs-Neutronenquelle Heinz Maier-Leibnitz-II reactor in Germany; Belgian Reactor-2 in Belgium; the High Flux Reactor in the Netherlands; the High Flux Reactor at the Institut Laue-Langevin in France; and MIR.M1, BOR-60, SM-3, RBT-6, and RBT-10/2 at the Joint Stock Company “State Scientific Center—Research Institute of Atomic Reactors” in Dimitrovgrad, Russia. These trips also included meetings with representatives from the Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA) and Compagnie pour l’Etude et la Réalisation de Combustibles (the subsidiary of AREVA responsible for research reactor fuel manufacture) in Paris and representatives from the Russian Academy of Sciences, Center for Energy and Security Studies, and Rosatom (the Russian national nuclear corporation) in Moscow. During the site visits and tours, committee members discussed opportunities and challenges associated with research reactor fuel conversion and fabrication

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⁹ This joint meeting was the result of discussions between the Academies and the IAEA regarding two similar but previously disconnected efforts. Task 1 from this study’s statement of task directs the committee to establish a list of research reactors currently using HEU fuel. At the same time, the IAEA was initiating efforts to update a similar list to better assist its member states. By combining the efforts of the two organizations, the joint IAEA–Academies meeting was able to attract a broad international community of experts to produce a list.

¹⁰ Because of BWXT visitor restrictions, only committee members who were U.S. citizens (excluding U.S. citizens with dual citizenship) were allowed to participate in the tour.

¹¹ A note about research reactor naming convention: the names of research reactors can be written in all capital letters. In some cases, these names are acronyms, while in others they are a series of letters and numbers without acronyms. In this report, the capitalization of the name of the research reactor follows the reactor operator’s use. For example, the MARIA reactor in Poland is capitalized (and is not an acronym) while the name of the Eole reactor in France is not.

with facility operators and gained a deeper understanding of and multiple perspectives on the issues surrounding the conversion of research reactors to LEU fuel. A full list of the committee’s data-gathering sessions and site visits can be found in Appendix C.

The subject matter of the study touches on topics that are considered sensitive (i.e., nuclear security and terrorism). However, the entire report is publicly available, and the findings and recommendations are based on publicly available information. One organization provided unclassified, controlled-restricted information for this study through Freedom of Information Act exemptions approved by the Academies. This information was related to the U.S. government’s pricing of HEU and LEU fuel and contributed to the committee’s overall understanding of the various factors affecting fuel conversion. That said, none of the controlled-restricted information is included in this report.

Early in the study the committee chose a broad interpretation of its task statement as follows:

• The Task 1 list was generated using publicly available information only. A joint IAEA–Academies meeting and expert opinion obtained through public meetings and further supported through public documents provided important input.
• The Task 1 list of civilian reactors would include critical and subcritical assemblies, pulsed reactors, and steady-state reactors. A land-based reactor not connected to the grid (not providing electricity to the grid, for example) was the committee’s working definition of “civilian research reactor”; therefore, the committee excluded propulsion reactors (e.g., spacecraft, icebreakers, or naval) in its definition. Research reactors with a dual use (i.e., civilian and military) were included in the Task 1 list; reactors with a sole military purpose were excluded because the statement of task clearly specifies the scope to include “civilian” reactors only.¹² See Chapter 2 and Appendix E for more details.
• Planned research reactors using HEU fuel were identified during numerous site visits and investigated through the IAEA’s research

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¹² The committee is aware of the Fissile Material Working Group’s (FMWG’s) recommendation to expand the scope of civilian research reactors to include propulsion and propulsion systems, but this was not consistent with the committee’s interpretation of its statement of task. The FMWG recommendations for the 2016 Nuclear Security Summit are available at http://www.fmwg.org/FMWG_Results_We_Need_in_2016.pdf. P. 4: “Other civilian uses and non-weapons applications, including propulsion reactors and military research reactors, have been outside of the discussion. Though it will be politically difficult to establish consensus on elimination in all non-weapons applications, HEU minimization and elimination efforts cannot maximize security gains if the scope is not comprehensive.”

• reactor database. Other planned reactors were identified during consultations with experts.

• The “review of status” requested in Task 2 reviewed progress since the last major Academies study on this topic (NRC, 2009).
• The phrase “use of HEU in fuel for research reactors” from Task 3 included HEU fuel stored at civilian facilities (as defined above) such as fresh and spent fuel. This includes research reactors that shut down but have HEU fuel (fresh and/or spent) remaining on site. As such, the committee explored U.S. fuel return programs.
• The reference in Task 3 to “others” included programs throughout the world related to elimination of HEU fuel from research reactors.
• Conversion is a general term which can be defined as the changing of one type of fuel to another (i.e., different chemical composition or enrichment level) in a reactor. Throughout this report it typically refers to conversion of HEU-fueled reactors to LEU-fueled reactors. Exceptions will be clear from the context.

BACKGROUND

Proliferation concerns about the use of HEU in civilian applications have motivated national and international programs to replace HEU with LEU. Within the United States, the NNSA manages efforts to eliminate or minimize (where elimination is not possible) special nuclear materials¹³ in civilian applications through the Office of Material Management and Minimization.¹⁴ This office is organized into three major activities: material removal, reactor conversion, and material disposal.¹⁵

The history of the U.S. reactor conversion programs can be described by three periods and changes in management: 1978 to 2003, 2004 to 2014, and 2015 to the present. From 1978 to 2003, the Reduced Enrichment for Research and Test Reactors (RERTR) program was responsible for the initial conversion efforts for the U.S. government. In 2004, the Global Threat Reduction Initiative (GTRI) was established. From 2004 to 2014, conversions and related activities were led by GTRI’s Convert Program. In part because of increased funding, the pace of conversions accelerated and

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¹³ Special nuclear material is defined by Title I of the Atomic Energy Act of 1954 as plutonium, uranium-233, or uranium enriched in the isotopes uranium-233 or uranium-235 (from USNRC website: http://www.nrc.gov/materials/sp-nucmaterials.html).

¹⁴ See http://nnsa.energy.gov/aboutus/ourprograms/dnn/m3; M³ was established in January 2015.

¹⁵ For reasons noted above, the committee explored U.S. fuel return and removal programs, but it did not investigate the third pillar of the Global Threat Reduction Initiative (GTRI; secure) or the M³ program (dispose).

the scope of the program expanded. The program also began to include shutdown research reactors in its progress metrics. The latter half of the GTRI Convert Program (2009, the date of its last domestic conversion, to 2014) was defined by an increased focus on a single basic formulation for very high-density LEU fuel and increased attention to conversion of non-U.S. reactors. Finally, in a January 2015 reorganization, GTRI became part of the new M³ office, with the reactor conversion program remaining largely intact as the Office of Conversion (see Figure 1.1 for a time line of the U.S. conversion programs; further details on the M³ reorganization can be found in Chapter 6). One of this committee’s tasks is to assess progress of the conversion efforts over the past 5 years: the late-GTRI and M³ eras.

Following many years of success in the conversion of both domestic- and foreign-owned civilian research reactors, the U.S. conversion program¹⁶ has become increasingly focused on the challenges involved with the conversion of the high performance research reactors (HPRRs)¹⁷ in the United States and Europe. Because many of these reactors are optimized for very high in-core/near-core neutron fluxes and have compact cores, they require the development of very high-density fuels (see Chapter 4 for more discussion of these fuels or Snelgrove et al., 1996; Van den Berghe and Lemoine, 2014). The U.S. conversion program requires that conversion will not significantly affect a reactor’s safety, performance, or operations. These constraints present significant technical challenges, causing a major expansion of the time line for conversion of these reactors, now projected to be completed in 2035 (Bunn et al., 2014; DOE, 2014¹⁸), compared to the 2018 deadline projected in the NNSA’s fiscal year (FY) 2009 budget request and discussed in the last Academies report (DOE, 2008¹⁹; NRC, 2009).

Several factors contribute to the urgency of optimizing the effectiveness of the M³ Office of Conversion. The final Nuclear Security Summit will be held in 2016, thus ending focused international support on the goals aligned with those of the M³ Office of Conversion and its other offices. The dates

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¹⁶ “The U.S. conversion program” refers to both the GTRI Convert Program and the M³ Office of Conversion.

¹⁷ High performance research reactors are, in the most general sense of the definition, reactors for which available fuels do not currently exist to support conversion without an effect on their performance (Roglans, written communication, September 2015). However, the use of “HPRR” in this report normally refers to research reactors that have compact cores and produce very high fluxes of neutrons.

¹⁸ From the NNSA’s FY 2015 budget request, p. 462: “By 2035, convert or verify the shutdown prior to conversion of approximately 200 HEU reactors and isotope production facilities.”

¹⁹ From the NNSA’s FY 2009 budget request, p. 531:

By 2018, convert to LEU 129 of 207 HEU reactors. (The IAEA identified 207 reactors designed to operate on HEU fuels. These reactors average 5 kg of HEU per reactor to operate. LEU fuel exists or is being developed which will allow 129 of these 207 reactors to be converted thus minimizing the use of HEU in civilian applications.)

FIGURE 1.1 A time line of U.S. civilian research reactor conversion programs through the current projected end date of 2035. The Reduced Enrichment of Research and Test Reactor (RERTR) program was first established in 1978; the Global Threat Reduction Initiative (GTRI) replaced RERTR in 2004, and the Office of Material Management and Minimization (M³) replaced GTRI in January 2015. This figure illustrates the changing mission of the programs; most recently, a change from GTRI’s three main pillars of convert-remove-secure to M³’s focus on convert-remove-dispose (the management of securing civilian HEU has moved into another office within the National Nuclear Security Administration). The interrupted green bar shows a pause from 1993 to 1996 when the RERTR Program switched from reprocessing to spent fuel storage as a back-end solution because of a change in U.S. policy. The remove program is expected to end in 2022 with the conclusion of the Gap Removal program described in Chapter 6. Two exceptions to this end date have been granted: 2025 for Austria and 2029 for Japan. SOURCE: Landers (2014) and http://nnsa.energy.gov/aboutus/ourprograms/dnn/m3.

for conversion of the world’s highest performance research reactors—which are, on average, more than 40 years old—are about two decades away (see Chapter 2), and the M³ Office of Nuclear Material Removal is scheduled to end in 2022.²⁰ The last research reactor conversion in the United States was in 2009, and the rate of conversions worldwide has decreased (see Chapter 5), although permanent reactor shutdowns continue at a healthy pace. In addition, the M³ Office of Conversion end date for converting the remaining research reactors that are not high performance has lengthened significantly, with a currently projected end date two decades away, comparable to the conversion dates for the HPRRs, although for different reasons.

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²⁰ The U.S.-origin fuel return program is ending because nearly all of the fuel identified under this program (Training, Research, Isotopes, General Atomics [TRIGA], and Materials Test Reactors fuel) has either been returned or has been planned for return. This program is no longer an incentive for conversion. The Gap Materials Program is a broader-scoped program and continues to provide incentives for conversion through 2022 (and with some exceptions, beyond that date).

The committee investigated several questions as it addressed its task:

• If conversion to LEU fuel becomes possible at about the same time as the end of the operational lifetime of a reactor, then does it make sense to plan to convert that reactor if newly designed LEU-fueled reactors are being planned, constructed, or commissioned at the same time?
• What can be done to accelerate reactor conversions and minimize the quantities of the highest enriched civilian HEU fuel?
• What are other countries doing to accelerate conversion of HPRRs that require new fuel to be developed?

REPORT ROADMAP

The chapters of this report address the elements of the study charge. This first chapter provides background and an introduction to the study.

• Chapter 2 reviews the original and enduring motivations for the elimination of HEU from civilian applications, discusses the establishment of the definition of LEU, and provides an overview of the U.S. research reactor conversion program and its evolving scope over the years. The Task 1 list (civilian research and test reactors that operate using HEU fuel) is also provided in Chapter 2, with further discussion in Appendixes E (the synopsis of the IAEA-Academies meeting) and F (information collected by the committee from a wide variety of open sources on additional operating reactors that are considered outside the scope of this study). Chapter 2 also includes a review of civilian research and test reactor status over the past 5 years (Task 2).
• Chapter 3 discusses the purpose and performance requirements of the currently operating HPRRs and their continuing roles for science, engineering, and medical applications.
• Chapter 4 considers the technical obstacles to conversion of the remaining HEU-fueled civilian research reactors, primarily the HPRRs, including progress in developing high-density and very high-density fuels for the conversion of HPRRs and the consequent time line. In many cases, obstacles to reactor conversion are nontechnical.
• Chapter 5 reviews these nontechnical obstacles to conversion, paying particular attention to reactors in Russia, but also providing other examples to highlight both challenges and their potential solutions.

• Chapter 6 provides an assessment of the status and progress of the M³ Office of Conversion, including the progress being made to eliminate worldwide use of HEU in fuel for civilian research and test reactors, and recommendations for how the program can improve its effectiveness.
• The concluding remarks in Chapter 7 highlight the continuing importance of HEU minimization and elimination in civilian reactors, underscore the challenges still to be tackled, and point to hopeful next steps for the M³ Office of Conversion.
• Appendix C lists the committee’s meetings and site visits during which it gathered information for this report. Appendix D provides a list of acronyms used throughout the report. Appendix G provides a glossary of terms.

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