Plutonium disposition in the UK
As Cumbrians Opposed to a Radioactive Environment (CORE) recently noted, it was in 2008 that the UK Nuclear Decommissioning Authority (NDA) released a Comment Paper on the options for managing the plutonium stockpile accumulating from the reprocessing of spent fuel at Sellafield – a stockpile estimated by the NDA to reach 140+ tonnes (in the form of plutonium oxide powder) when all reprocessing at Sellafield has ceased.1
The NDA is years away from making a decision about how to dispose of the plutonium stockpile and/or to use it as reactor fuel. But the use of IFR/PRISM technology has been formally rejected. The NDA said in a March 2019 report:2
"The NDA considered a proposal by GE Hitachi Nuclear Energy (GEH) to build a fuel fabrication plant and two PRISM reactors to irradiate a plutonium alloy fuel. No PRISM reactors or fuel plants have ever been built, and the proposal considered by NDA therefore envisaged both the reactors and fuel plant being first of a kind.
"This approach had some theoretical benefits compared to the MOX options. PRISM fast reactors were put forward by GEH as commercially viable, "ready to deploy" and capable of quickly dispositioning the complete plutonium stockpile. However, the studies undertaken by NDA with GEH over the past few years have shown that a major research and development programme would be required, indicating a low level of technical maturity for the option with no guarantee of success.
"Whilst these R&D requirements are extensive, they are also reasonably well understood. However, the work needed for the fuel fabrication facility is considered preliminary and the proposal was based on not requiring further plutonium-active testing prior to scale-up and industrialisation. This major technical risk, based on GEH's proposal, would also be borne by the NDA. In addition, the regulatory review by the ONR and EA highlighted this approach as carrying significant licensing risks in all areas. Implementation scenarios were assessed as economically unfavourable compared to other options reflecting, in part, the technical and licensing uncertainties in the proposal.
"At this time, it is noted that the cost, scope and extent of work required to progress Fast Reactor options, such as the GEH PRISM, as well as the timeframe for these options to become available, means it is not credible for the NDA to develop these options, or have them available for implementation within the next 20 years. Therefore no further work with GEH has been funded by NDA. However, given the very long-term nature of any disposition programme, the NDA will continue to monitor Fast Reactor developments world-wide and assess levels of maturity and potential benefits."
Thus the NDA has reaffirmed views expressed in internal 2011 emails, released under Freedom of Information laws, that its "high-level assessment" of PRISM reactors for plutonium disposition found that "the technology maturity for the fuel, reactor and recycling plant are considered to all be low".3
The use of plutonium in MOX fuel for conventional light-water reactors or CANMOX fuel for CANDU EC-6 reactors remain under consideration by the NDA, but the prospects are not good. The use of plutonium in MOX fuel is the NDA's preferred option, but as the NDA's recent report states, "this [MOX] option carries significant risks and uncertainties since it is fundamentally dependent on the availability of suitable new reactors in the UK and the operators' willingness to use MOX fuel. As the overall design of a MOX plant depends on a number of reactor-specific factors, commitments from operators under suitable terms would be a pre-requisite to reaching a decision on this option."2
The previous MOX plant at Sellafield suffered "many years of disappointing performance" according to the NDA's chief executive, and the decision to close the plant was announced in August 2011 as there were no longer any customers in the aftermath of the Fukushima disaster in Japan.4
As for the CANMOX option ‒ the building of a CANMOX fuel plant and at least two CANDU EC-6 reactors ‒ the NDA report states that this is a "credible" option but "no discernible evidence was offered that this approach would be significantly simpler or more cost-effective than reuse as MOX in LWRs." The NDA notes "greater technical and implementation risks" with CANMOX compared to MOX "largely due to the fact that production of CANMOX fuel has not been demonstrated on an industrial-scale. In addition, there are currently no CANDU reactors in operation which achieve the levels of fuel irradiation proposed by SNC Lavalin for this option."2
Given the poor prospects for using plutonium as reactor fuel, immobilization followed by disposal may become the NDA's favoured option. Three immobilization options are being studied: hot isostatic pressing to produce a monolithic ceramic product; a pressing and sintering process similar to MOX manufacturing to produce pellets; and encapsulation in cement-based matrices as used in the UK for Intermediate Level Wastes.2
Plutonium disposition in the US
IFR/PRISM technology has also been rejected for plutonium disposition in the US. MOX has also been rejected ‒ in part because of significant delays and cost overruns with a partially constructed and now abandoned MOX fuel fabrication plant in South Carolina. The US government favors a "dilute and dispose" option for disposing of 34 tonnes of plutonium: the Savannah River Site facility will be used to dilute plutonium and it will be disposed of at the WIPP repository in New Mexico.5
The US Department of Energy's (DOE) Plutonium Disposition Working Group released a report in 2014 which considered the use of Advanced Disposition Reactors (ADR) for plutonium disposition.6 The ADR concept was similar to GE Hitachi's PRISM according to the DOE. The DOE's cost estimates for the use of ADRs for the processing of 34 tonnes of plutonium were as follows: 'capital project point estimate' US$9.4 billion; operating cost estimate US$33.4 billion; and other program costs US$7.6 billion. Thus the total would be "more than $58 billion life cycle cost when sunk costs cost are included." That was twice as much as the next most expensive option for plutonium management considered in the 2014 report.
The DOE report estimated that it would take 18 years to construct an ADR and associated facilities ‒ despite claims from GE Hitachi and others that IFR/PRISM technology could be operational in as little as five years. The DOE report stated: "Final design of a commercial fast reactor would require significant engineering and licensing and as such carries uncertainties in being able to complete within the assumed duration."6
On the technical challenges, the DOE report said:6
"Irradiation of plutonium fuel in fast reactors ... faces two major technical challenges: the first involves the design, construction, start-up, and licensing of a multi-billion dollar prototype modular, pool-type advanced fast-spectrum burner reactor; and the second involves the design and construction of the metal fuel fabrication in an existing facility. As with any initial design and construction of a first-of-a-kind prototype, significant challenges are endemic to the endeavor, however DOE has thirty years of experience with metal fuel fabrication and irradiation. The metal fuel fabrication facility challenges include: scale-up of the metal fuel fabrication process that has been operated only at a pilot scale, and performing modifications to an existing, aging, secure facility ... Potential new problems also may arise during the engineering and procurement of the fuel fabrication process to meet NRC's stringent Quality Assurance requirements for Nuclear Power Plants and Fuel Reprocessing Plants."
In short, the ADR option was associated with "significant technical risk" according to the DOE report, and metal fuel fabrication faces "significant technical challenges".
A review of the 2014 report, commissioned by the National Nuclear Security Administration and carried out by Aerospace, reached similar conclusions.7 Commenting on its own assessment and the 2014 DOE report, Aerospace said:
"Both reports acknowledge the high technical and programmatic risks inherent in the necessary research and development, technology demonstration, full-scale design, construction, and startup of an advanced fast spectrum burner sodium cooled reactor. Both reports acknowledge that additional new facilities for metal fabrication will be required, incurring additional technical and programmatic risk. It is expected in both reports that the NRC licensing process and fuel qualification process will be lengthy.
"ADR is the most complex and technically challenging option. The Aerospace assessment notes significant issues with the industrial base, including the adequacy of the workforce, fast reactor knowledge base, and the need for a significant R&D and technology development and demonstration phase ...
"Long term storage of spent plutonium metal fuel rods may require a different approach than that used for spent commercial uranium fuel rods, and may require the development of a new facility.
"The ADR project is more technically challenging and complex than the MOX Fuel option. New facilities are needed for plutonium metal processing, fuel fabrication, and spent fuel storage. Execution of design and construction in an NRC licensing environment is new for advanced liquid metal reactors and will require hundreds of nuclear qualified suppliers and construction workers over a decade or more."
Aerospace commented on problems common to fast reactors:7
"Based on experience with existing fast reactors that utilize sodium as the reactor core coolant, fires and steam explosions have been major problems during operations. A number of plants have been shut down for long periods of time in the past as a result of sodium fires. A research report of the International Panel on Fissile Materials on fast reactor programs highlights the maintenance and repair challenges at fast reactors: "The reliability of light-water reactors has increased to the point where, on average, they operate at 80 percent of their generating capacity. By contrast, a large fraction of sodium-cooled demonstration reactors have been shut down most of the time that they should have been generating electric power.""
Aerospace was also unimpressed by GE Hitachi's cost estimates:7
"Aerospace finds the quality and completeness of the cost basis of estimate is difficult to assess due to the age of the source data provided ... The ADR estimate also lacks costs associated with program-level risks that are likely to be encountered during development and operations. Therefore, the ADR program cost estimate reported in the 2014 [DOE] PWG report may be low relative to realized actual costs should the program proceed. It is very likely that the ADR program would be subject to funding constraints on capital and construction."
An August 2015 DOE Red Team report didn't even consider IFR/ADR technology worthy of detailed consideration:8
"The ADR option involves a capital investment similar in magnitude to the MFFF [Mixed Oxide Fuel Fabrication Facility] but with all of the risks associated with first of-a kind new reactor construction (e.g., liquid metal fast reactor), and this complex nuclear facility construction has not even been proposed yet for a Critical Decision (CD)-0. Choosing the ADR option would be akin to choosing to do the MOX approach all over again, but without a directly relevant and easily accessible reference facility/operation (such as exists for MOX in France) to provide a leg up on experience and design. Consequently, the remainder of this Red Team report focuses exclusively on the MOX approach and the Dilute and Dispose option, and enhancements thereof."
The DOE Red Team report said that the IFR/ADR option has "large uncertainties in siting, licensing, cost, technology demonstration, and other factors" but "could become more viable in the future" if fast reactors were to become part of the overall US nuclear energy strategy.8
1. CORE, 6 May 2019, 'A decision on the fate of UK's Plutonium stockpile remains years away', http://corecumbria.co.uk/briefings/a-decision-on-the-fate-of-uks-plutoni...
2. UK NDA (Nuclear Decommissioning Authority), March 2019, Progress on Plutonium Consolidation, Storage and Disposition, https://assets.publishing.service.gov.uk/government/uploads/system/uploa...
3. Rob Edwards, 24 Jan 2012, 'Plans for Sellafield plutonium reactor rejected', https://www.theguardian.com/environment/2012/jan/24/sellafield-plutonium...
4. Fiona Harvey, 3 Aug 2011, 'Sellafield Mox nuclear fuel plant to close', https://www.theguardian.com/environment/2011/aug/03/sellafield-mox-plant...
5. World Nuclear Association, 16 May 2018, 'Perry scraps completion of US MOX facility', http://www.world-nuclear-news.org/UF-Perry-scraps-completion-of-US-MOX-f...
6. US Department of Energy, April 2014, 'Report of the Plutonium Disposition Working Group: Analysis of Surplus Weapon Grade Plutonium Disposition Options', http://fissilematerials.org/library/doe14a.pdf
7. Aerospace, 20 Aug 2015, 'Plutonium Disposition Study Options Independent Assessment Phase 2 Report', prepared for National Nuclear Security Administration, https://www.energy.gov/sites/prod/files/2018/02/f49/Plutonium_Dispositio...
8. Thom Mason et al., 13 August 2015, 'Final Report of the Plutonium Disposition Red Team', for the US Department of Energy, https://www.energy.gov/sites/prod/files/2018/02/f49/Pu-Disposition-Red-T...