Official plans to manage French uranium and plutonium stockpiles over the long term were dealt a new blow when a scientific committee expressed doubts on conclusions drawn from unsupported scenarios. The report by the National committee for the assessment of research and studies on the management of radioactive materials and wastes (Commission nationale d'évaluation des recherches et études relatives à la gestion des matières et des déchets radioactifs - CNE), published on 16 June 2010, comes shortly after the revised edition of the National management scheme for radioactive materials and wastes, PNGMDR, stressed the need for considering the possibility that long term plans to re-use accumulated nuclear materials fail.
The "closeness" over time of the French nuclear fuel cycle, a core assertion to back the official "reprocessing-recycling" strategy supported by the PNGMDR, relies very much on the role of future reactors. While the current management options lead to the accumulation of uranium and plutonium stocks in various forms, their "re-usable" status is officially justified by the prospect of using them to feed this new fleet.
The underlying scenario is the progressive deployment of so-called Generation-IV generation reactors. France currently operates 58 pressurized water reactors (PWR), totaling 63 GWe of capacity. The scenario, based on maintaining a level of around 60 GWe of capacity, is to use the new EPR (European Pressurized water Reactor) to replace 40 GWe of ageing capacity between 2020 and 2040, until future FBRs are mature enough, then replacing the remaining 20 GWe by these FBRs between 2040 and 2050. Using the projected 60 years lifetime of EPRs, they could eventually be replaced by FBRs between 2080 and 2100. The general plan is therefore to shift from 100% PWRs to a mix of two thirds PWRs and one third FBRs by 2050, and then 100% FBRs by 2100.
According to the PNGMDR, this deployment of Generation-IV FBRs:
is the "reference industrial solution" for the management of spent REU and MOX fuel, which are not reprocessed, with their stockpiles projected to reach 1,320 tHM and 2,550 tHM respectively by 2030;
needs to be started with plutonium loads that will use the projected stockpile. Industry estimates that 505 to 565 tHM of plutonium (separated and in spent UOX, REU and MOX fuel) will be available by 2040, corresponding to the needs of 25 FBRs of 1,450 MWe capacity;
could then use depleted uranium stocks as fertile material to generate the new plutonium that it needs. According to the scheme, the large stockpiles, projected to reach more than 450,000 tHM by 2030, provide for "thousands of years" of operation.
Scientists from the CNE basically say it won't be that simple. The work of the committee, which operated for 15 years under a 1991 Act (loi n� 91-1381 du 30 d�cembre 1991 relative aux recherches sur la gestion des d�chets radioactifs) and was reapppointed under a 2006 Act (loi n� 2006-739 du 28 juin 2006 de programme relative � la gestion durable des mati�res et des d�chets radioactifs), usually focuses on research on long-lived radioactive waste rather than plans to re-use plutonium and uranium on the long term.
The CNE believes in the principle of relying on FBRs for optimizing the long-term balance of plutonium. The report stresses that re-using plutonium in PWRs degrades its isotopic composition, and is therefore limited because of constraints on the share of plutonium in the fuel for safety reasons. This is why, the CNE notes, "numerous options for the multi-recycling of plutonium in PWRs have been explored and are foregone now". Conversely, the neutronic balance would be better in FBRs and the plutonium quality stabilizes through recycling, which the CNE considers "a reason to reserve plutonium for FBRs". The CNE also notes that multi-recycling of plutonium in FBRs generates 3.5 times much less americium and curium than in PWRs. Also, FBRs could be further used for transmutation of minor actinides. And finally, the CNE signals that the production of plutonium from fertile uranium-238 is much faster in FBRs than in PWRs.
But the CNE warns against hasty conclusions on the real-scale implementation of this strategy, warily pointing to the technical obstacles and the potential consequences on safety or economics.
The first area of concern for the CNE is the need to develop a precise characterization of the flows of materials involved and their evolution over time. The scenarios developed by the French Atomic Energy Commission (Commissariat � l'�nergie atomique, CEA) mostly provide target figures for balance at equilibrium, without assessing the transition phases. The report notes the FBRs fleet of 60 GWe could recycle 80 tHM of plutonium and 330 tHM of uranium every year, and use 40 tHM of reprocessed uranium. But this equilibrium between production and consumption of plutonium and minor actinides could only be reached by 2100. Moreover, the report recalls that the time for developing the new capacities needed for generation, reprocessing, fuel fabrication could be longer than assumed in the scenario. According to the CNE, both EDF and AREVA expressed cautiousness with the timeline for the deployment of recycling and transmutation in FBRs, starting with the plan to put 2 GWe per year in operation between 2040 and 2050.
The CNE also calls for a cautious examination of safety issues related to the quantities and the characteristics of the materials involved. The inventory of plutonium at a time, in the reactors and the reprocessing plants, would reach between 900 and up to 1,200 tHM, depending on the scenario; the inventory of minor actinides would vary between 75 tHM and 160 tHM. The report also touches on problems arising in fabrication, use, transport, manipulation and reprocessing of the fuels needed, for instance due to their thermal load.
Finally, the report stresses the implications on economics, as the construction and operation of FBRs and their fuel fabrication and reprocessing plants would be more costly than in the case of PWRs, and the high uncertainty attached to the current estimates. The CNE also recalls that EDF itself is wary that economic assumptions might not be realistic enough, considering past experience of "systematic cost increases of projects developed, together with delays". As they stand, the studies on scenarios mostly "highlight the size of new industrial equipment and the technical breakthrough needed", the CNE concludes, and "cast serious doubts" on the most complex options. Altogether, they "rarely allow, for a given problem, to diagnose the technical or financial difficulties". A mild way of suggesting that any demonstration of effectiveness, safety and economics of official long term plans to re-use French plutonium and uranium stockpiles is still very far away.