2
Disposition of Surplus Plutonium by the United States
The U.S. government defines surplus plutonium as plutonium that “is no longer needed for U.S. national security or programmatic purposes” (DOE 2015, p. S-1).1 The U.S. stockpile of surplus plutonium currently exceeds 60 MT and exists in many forms, including reactor fuel, pits2 from retired nuclear weapons, used nuclear fuel, and scraps and residues from nuclear weapons production (see Figure 2-1) (DOE 2015).
The disposition pathways for some stocks of U.S. surplus plutonium have already been determined by DOE-NNSA, as shown in Figure 2-1.3 Of direct relevance to the present study is the proposed disposition pathway for 34 MT of pits and associated plutonium metals and oxides. These materials are being dispositioned by the DOE-NNSA under the Plutonium Management and Disposition Agreement (PMDA), which was signed by the United States and the Russian Federation in 2000 and amended in 2010. The intent of the PMDA is for both parties to convert surplus plutonium into forms unusable for nuclear weapons; specific methods of disposition are outlined within the PMDA.
The 2000 agreement commits both countries to the disposition of no less than 34 MT of weapons-grade4 plutonium by one or both of two options: (1) incorporation of pit plutonium into mixed oxide (MOX) reactor fuel5 followed by irradiation in nuclear reactors, or (2) immobilization of non-pit plutonium in glass or ceramic matrixes followed by encapsulation with high-level radioactive waste in a system suitable for geologic disposal.6 The amended 2010 agreement recognized only irradiated MOX fuel as the disposition option of choice. Therefore, the committee did not include immobilization as an option for disposition in its assessments. The United States and the Russian Federation are required under the agreement to begin surplus plutonium disposition by 2018, with implementation to be verified by the International Atomic Energy Agency (DOS 2000, 2010). See Section 3.3 for more details on the PMDA, its technical and procedural requirements, and political statements regarding the current status of its implementation by both the United States and the Russian Federation.
Both of the PMDA surplus plutonium disposition options listed above, incorporation into MOX fuel followed by irradiation or immobilization with high-level radioactive waste, meet a set of criteria developed by a National Academy of Sciences committee in 1994 and commonly known as the “spent fuel standard” (NAS 1994). Written at the end of the Cold War and as nuclear materials were being declared as excess to weapons programs in the United States and the Russian Federation, approaches to characterize and evaluate options for plutonium management and disposition that would minimize the risk of plutonium recovery for reuse in weapons were presented:
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1 See also the first declaration of surplus (referred to as “excess”) plutonium (DOE 1996b, Table 15, p. 76).
2 A “pit” is the core of an implosion-type nuclear weapon (DOE 2015, p. S-1).
3 Two entities within DOE are involved in the dilute and dispose conceptual plan. DOE-NNSA is responsible for development and execution of the plan for the disposition of 34 MT identified by the PMDA. DOE-EM is responsible for disposing of the surplus plutonium once it has been diluted and declared as waste.
4 Defined in the PMDA as “plutonium with an isotopic ratio of plutonium 240 to plutonium 239 of no more than 0.10” (DOS 2000, p. 2).
5 MOX fuel contains plutonium and slightly enriched uranium, both in oxide form (DOS 2000).
6 A third option, any other methods that may be agreed to in writing by the Parties, is also included in both the original and amended PMDA.
Options for the long-term disposition of weapons plutonium should seek to meet a “spent fuel standard”—that is, to make this plutonium roughly as inaccessible for weapons use as the much larger and growing stock of plutonium in civilian spent fuel. Options that left the weapons plutonium more accessible would mean that this material would continue to pose a unique safeguards problem indefinitely. Conversely, the costs, complexities, risks, and delays of going beyond the spent fuel standard to eliminate the excess weapons plutonium completely or nearly so would not offer substantial additional security benefits unless society were prepared to take the same approach with the global stock of civilian plutonium. (NAS, 1994, p. 36, emphasis original)
DOE has issued a series of environmental impact statements (EISs) and records of decision to shape and modify the disposition strategy for U.S. surplus plutonium (see Section 3.2 and Box 3-1). In 2000, DOE issued a Record of Decision (ROD) selecting the MOX fuel option using commercial nuclear reactors for dispositioning 34 MT of surplus plutonium under the 2000 PMDA and the immobilization option for dispositioning surplus plutonium that was not suitable for MOX fuel. In 2002, the George W. Bush administration cancelled the immobilization program citing budget constraints and the decision to support only one approach for plutonium disposal (see Box 2-1). This change was accounted for in the 2010 amended PMDA, as noted previously.
The MOX fuel option within the PMDA provides four barriers to recovery of the plutonium and is comparable to the spent fuel standard for the diversion, recovery, or theft of U.S. surplus plutonium (NAS 1994):
- Chemical: The plutonium-239 in metal form is first oxidized and then chemically diluted by blending with uranium oxide (UO2) to form MOX fuel.
- Isotopic: The plutonium-239 isotopic composition is shifted during irradiation by the fission of plutonium-239 and -241 and by the transmutation of plutonium-239 to -240, plutonium -240 to -241, and plutonium -241 to -242.
- Radiation: Irradiated MOX fuel creates a radiation barrier sufficient to be self-protecting for decades.
- Physical: the weight and size of a nuclear fuel assembly are sufficient to require special handling equipment for processing.7
The United States began construction of a facility to manufacture MOX fuel, the Mixed Oxide Fuel Fabrication Facility (“MOX Plant”), at the Savannah River Site in South Carolina in 2007. Construction has encountered substantial schedule delays and cost overruns. The Obama administration proposed to stop construction of this facility and instead use a “dilute and dispose process” to disposition 34 MT of surplus plutonium (Goodson 2018). Congress provided $5 million to DOE-NNSA in fiscal year 2016 to begin planning and development of a conceptual design for the dilute and dispose process (see Box 2-1). In fiscal year 2017, Congress provided $15 million to DOE-NNSA to continue planning and development of the dilute and dispose option; it also mandated this National Academies of Sciences, Engineering, and Medicine evaluation (U.S. Congress 2016). In May 2018, the Trump administration announced plans to cancel the MOX plant and declared the dilute and dispose option as the program of record.8 In October 2018, the DOE-NNSA issued a letter to CB&I AREVA MOX Services, the contractor of the MOX plant, directing them to terminate construction of the plant. DOE plans to convert the existing MOX infrastructure to a facility that would produce up to 50 plutonium pits per year by 2030.
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7 The PMDA requirements do not include deep geologic disposal of the irradiated MOX fuel by either party, only irradiation to create a radiation barrier to recovery. If and when the irradiated MOX fuel were to be emplaced in a deep geologic repository, this would add a physical barrier to recovery, diversion, and theft.
8 On May 10, 2018, Secretary Perry issued a letter to Congress announcing DOE’s decision to cancel the MOX plant and move to the dilute and dispose option for disposal of surplus plutonium citing a cost estimate that showed the cost of dilute and dispose was less than half of the projected cost of the MOX option (Demarest 2018). The authority to take such action by Sec. Perry was granted through the National Defense Authorization Act for 2018 (H.R. 2810, 115th Cong. (2018).
2.1 Conceptual Plans for Dilute and Dispose
The dilution process entails first the oxidization of surplus plutonium metal and then the dry blending of the plutonium oxide with an adulterant to dilute the plutonium-239 content (see Figure 2-3a for additional process details). In the conceptual plan, the blended material will be packaged to make it suitable for transport to and disposal in WIPP, a deep geologic repository located within a bedded salt formation near Carlsbad, New Mexico. After approximately 20 years of testing and development, the WIPP opened in 1999 to dispose of defense-generated transuranic (TRU) waste created by the U.S. government (see Figure 2-4) (GAO 2017).9 TRU waste emplaced in WIPP will eventually be encased in salt as the salt formation naturally creeps to close voids and reconsolidates, making the TRU waste isolated from the environment. The dilute and dispose process has been demonstrated at a small scale by DOE-EM as it begins to process 6 MT of surplus plutonium (Figure 2-1). Additionally, DOE reports that 4.8 MT of plutonium similarly processed is emplaced at WIPP.
DOE-NNSA asserts that the end state of the dilute and dispose process would introduce sufficient chemical and physical barriers to meet the intent of the PMDA for preventing plutonium recovery and reuse. DOE-NNSA states that the barriers include: oxidation and dilution of plutonium with an adulterant (“chemical”) and disposal of the packaged and diluted plutonium in a deep geologic repository (“physical”). The term “end state” refers to the state of the surplus plutonium after both dilution and disposal. However, the dilute and dispose process is not currently a PMDA-approved method for dispositioning U.S. surplus plutonium.
A conceptual flowsheet for the dilute and dispose process is shown in Figure 2-2; four DOE sites would be involved in the implementation of this process: Pantex Plant in Texas; Los Alamos National Laboratory in New Mexico; Savannah River Site (SRS) in South Carolina; and WIPP in New Mexico. The front end of the dilute and dispose process is identical to that for the MOX process until the process converges on “Dilute” in Figure 2-2.
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9 The term “transuranic waste” is defined in the Waste Isolation Pilot Plant Withdrawal Act as “waste containing more than 100 nanocuries of alpha-emitting transuranic isotopes per gram of waste, with half-lives greater than 20 years, except for—(A) high-level radioactive waste; (B) waste that the Secretary has determined, with the concurrence of the Administrator, does not need the degree of isolation required by the disposal regulations; or (C) waste that the Nuclear Regulatory Commission has approved for disposal on a case-by-case basis in accordance with part 61 of title 10, Code of Federal Regulations.” Waste Isolation Pilot Plant Withdrawal Act, Pub. L. No. 102-579, 106 Stat. 4777, 4779 (1992)
Beginning with the box labelled, Surplus Pit Management, a total of 26.2 MT of pits from disassembled nuclear weapons (labelled “surplus pits”) will be shipped from the Pantex Plant to Los Alamos National Laboratory via Office of Secure Transport (OST).
The Pit Disassembly and Processing step is the disassembly and conversion of the pits into plutonium oxide, which will take place at Los Alamos National Laboratory. This oxidized material will be packaged for transportation and storage (placed into a DOE-STD-3013 container) and shipped via OST to the Savannah River Site for further processing.
Non-Pit Oxide Production indicates a total of 7.8 MT of non-pit plutonium that is stored in different DOE sites; a portion of the non-pit plutonium is oxidized and will be sent directly to the Savannah River Site for further processing, the remaining portion of non-pit plutonium will be shipped first to Los Alamos National Laboratory to be oxidized before being shipped to and processed at the SRS.10 All shipments described in this step are shipped via OST.
During the Dilute and Process and Geological Repository Disposal steps, the oxidized plutonium is processed, packaged, and emplaced in WIPP. When the plutonium oxide reaches the SRS, it will follow a different processing path than that proposed for the MOX process. Figures 2-3a and 2-3b provide details on the dilution, packaging, and characterization steps that will take place at SRS.
The process outlined in the detailed but unclassified flow sheet (Figure 2-3a) for the dilute process was shown to the committee at a mock-up unclassified glovebox at SRS. The “radiological barrier” in the figure refers to a can/bag/can barrier put in place to protect workers from contamination of the diluted plutonium. It does not refer to additional radioactive material added to the diluted plutonium, or a “radiation barrier,” as used previously in this report.
The dilution processing steps are as follows:
- The 3013 canisters containing the oxidized plutonium will be opened at SRS in a glovebox, and dry-blend the plutonium oxide with a multicomponent adulterant11 to dilute the plutonium-239 content. The diluted plutonium oxide will be placed into new cans (can/bag/can); the final assembly is then assayed and packaged into a stainless steel pipe, the Criticality Controlled Component (CCC). Two can/bag/can assemblies are placed into a single CCC. The CCC is placed inside of a Criticality Controlled Overpack (CCO). The CCO is a 55-gallon drum. CCOs are placed in approved containers for transport, TRUPACT-II, for shipment to WIPP. The dilution process at SRS is currently being carried out at a small-scale in order to process 6 MT of surplus non-pit plutonium for dilution and disposal (Gunter Decl.12) (see Figure 2-1 and Box 3-1).
- Not shown in the processing steps in Figure 2-3a is the termination of safeguards. The current status and plans for the removal of safeguards and an assessment of the security of the diluted plutonium are under development so the committee makes no assessment of this step in this Interim Report.
- If safeguards are terminated and the diluted plutonium13 is certified to meet WIPP’s waste acceptance criteria (WAC), the packaged plutonium waste form will be organizationally transferred to DOE-EM, which will ship it to WIPP and emplace it in the repository as contact-handled transuranic (CH-TRU) waste (DOE 2016d). See Figure 2-4.
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10 The quantities of pit and non-pit surplus plutonium for disposition are listed in Section I – Quantities and Methods of Disposition in the PMDA as amended in 2010. The location and proportion of oxidized/non-oxidized non-pit plutonium is classified by the U.S. government.
11 As noted previously, the properties of the adulterant are classified by the U.S. government.
12 South Carolina v. U.S. Department of Energy, No. 1:16-cv-00391-JMC (D.S.C. 2017).
13 The oxidized plutonium is considered “material” as it enters the process at SRS and the packaged and diluted plutonium is considered “waste” after it is determined to meet the WIPP WAC (GAO 2017). Plutonium is handled as accountable material until it is diluted and declared to be waste.
The dilute and dispose process will require extensive interstate truck transportation over a projected period of about 25 years.14 The DOE OST15 will be responsible for shipping undiluted plutonium materials from the Pantex Plant to Los Alamos and from Los Alamos to Savannah River following safety, security, and safeguarding protocols that have been in use for many decades. The packaged diluted plutonium waste will be shipped from Savannah River to the WIPP site by DOE-EM using existing TRU waste shipping casks and resources. DOE-EM plans to rely on the present set of rules and procedures, which have been used successfully to transport over 12,000 TRU waste shipments to WIPP, to ensure the safety and security of the proposed dilute and dispose TRU shipments (DOE-EM 2017).
A 2015 DOE red team review compared the MOX and dilute and dispose options and concluded that the latter process was technically viable and could be implemented at about half the cost of the former (Mason 2015). The red team also concluded in the executive summary (Mason 2015, p. xi) that the “risks associated with the Dilute and Dispose option are far lower than the MOX approach, since both the technology and the disposition process associated with Dilute and Dispose are far simpler.”16 The review also identified regulatory and other issues, including WIPP capacity, that “are not insurmountable” but should be addressed as early as possible during the planning phase. Although the committee has not yet seen risk assessments or program documents associated with the life-cycle cost estimate and cannot comment on risk, the committee notes that the technical complexity of the dilute and dispose option is lower than that of the MOX option.
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14 WIPP does not accept waste via rail (WIPP n.d.).
15 See https://www.energy.gov/nnsa/office-secure-transportation (accessed September 10, 2018).
16 The type of risk quoted above refers to the assessment of programmatic and technical risks (see Mason 2015, p. 34 for more discussion).
2.2 Current Status of DOE-NNSA Dilute and Dispose Planning Effort
DOE-NNSA received funding from Congress to begin planning for the dilute and dispose process in 2016, following the completion of the red team review referenced in the previous Section 2.1 (GAO 2017) (see Box 2-1). A high-level schedule of the dilute and dispose plan is shown in Figure 2-5. The planning effort is being managed under DOE Order 413.3B and has passed Critical Decision-0 (CD-0), Approve Mission Need (DOE 2010).17
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17 Order 413.3B outlines an internal DOE process for reviewing and approving large acquisition programs through Critical Decision milestones. After reaching CD0, DOE program managers may proceed with conceptual planning. See DOE 2010 (Table 2.0, p. A-5).
The process outlined in the National Environmental Policy Act (NEPA) requires DOE to obtain public comments and inputs for decisions and actions. The NEPA schedule for dilute and dispose in Figure 2-5 shows that a Notice of Intent (NOI) will be issued in late FY 2018 and a final EIS in mid FY 2020. Although requested, the committee has not yet seen a detailed NEPA strategy for the conceptual plan or details on what constitutes a final EIS, and the NOI had not been issued as of the writing of this Interim Report.
Also seen in Figure 2-5 is the planned duration of the dilute and dispose process. DOE-NNSA currently estimates that the effort to dilute and dispose of 34 MT of surplus plutonium will take 31 years to complete, beginning with conceptual design in 2018 and ending with emplacement of all 34 MT of diluted plutonium at WIPP in 2049.
