This report presents the results of a neutronic analysis related to the homogeneous recycling of different TRU mixtures (Pu, PuNp, PuNpAm, PuNpAmCm or PuNpAmCmBkCf) in PWRs using MOX-UE fuel, i.e. MOX fuel with a U235 enriched uranium support instead of depleted uranium (i.e. containing 0.25% U235) for standard MOX fuel. It focuses mainly on reactor physics issues and does not cope with other issues like economics, fuel fabrication, transportation or reprocessing that are essential to assess a system as a whole. This will be dealt with later if it is deemed necessary.

This report characterizes fuel cycle options in four areas -resource utilization, radioactive waste, fuel cycle safety, and proliferation resistance and physical protection. Graphs and tables provide insights regarding which features of a fuel cycle option most impact performance for a given characteristic. For example, some characteristics are insensitive to reactor technology but very sensitive to whether and what is recycled. Sometimes it is variations within a class of options that matter. For still other characteristics, the pattern is that a feature impacts performance only under certain situations and is irrelevant in others.Resource utilization: The utilization of uranium ranges from <1% for all thermal reactor concepts, up to ~10% for fast reactors with no fuel recycle, and approaching 100% for sustained recycle with fast reactors. The patterns for utilization of thorium are less clear due to less study of option space.Radioactive waste: There are many possible ways to reduce radiotoxicity and/or the mass of waste streams having both high-heat and high long-term radiotoxicity. The combination of decay heat and radiotoxicity complicates waste disposal and there is no international precedent for disposal of waste that has both high decay heat and high long-term radiotoxicity. The value of a given improvement method can range from very little to orders of magnitude depending on which other improvement methods are also used in a fuel cycle. For example, low processing loss of transuranic material to waste has little value in a single-recycle strategy but can have orders of magnitude impact in sustained recycle.Fuel cycle safety: Safety is too important to ignore during concept selection and development. Historical experience suggests that some types of safety issues are easier to resolve in concept development, detailed design, and/or operation than others. "Easier" can mean lower design cost to add safety systems as a design goes from concept to details, fewer iterations and delays with regulators, easier operation, a more transparent safety case engendering higher trust, less chance for expensive changes during construction, less chance of expensive retrofitting during operation, etc. Co-location of facilities, e.g., separation and fuel fabrication, is one of the ways that the potential risk of future fuel cycles may be reduced. Although the radiological risk from transportation has been shown to be low, public concerns are high and any industrial transport involves common daily transportation risks.Proliferation resistance and physical protection: There are many perspectives in this area, but there is no tool and no single indicator that covers the entire area and all four stages from material acquisition, transportation, transformation of material, and weapon fabrication. Conflicting claims can be often be better understood if it is realized that each claim can be valid within its subset of the entire area. Technology Insights and Perspectivesiv September 30, 2010 SUMMARYThis report characterize...

A 1000 MWth commercial-scale Sodium Fast Reactor (SFR) design with a conversion ratio (CR) of 0.50 was selected in this study to perform perturbations on the external feed coming from Light Water Reactor Spent Nuclear Fuel (LWR SNF) and separation groupings in the reprocessing scheme. A secondary SFR design with a higher conversion ratio (CR=0.75) was also analyzed as a possible alternative, although no perturbations were applied to this model.Metal and oxide fuel SFR designs were both included in the analysis. Initial results showed good agreement between the UREX+1a base cases and data previously published in the literature for the SFR conceptual design. The initial set of perturbations involved varying the external feed to study the so-called 'vintage problem', which addresses the large variation in burnup and cooling needed to be accommodated in the SFR. Three sets of external feed isotopic vectors were generated for the cases of a low burnup and long cooling time (33 MWd/kg, 30 year cooled LWR SNF), high burnup and medium cooling time (51 MWd/kg, 10 year cooled LWR SNF), and the reference high burnup and short cooling time (51 MWd/kg, 5 year cooled LWR SNF.) Results show that the choice of external feed has little impact on the TRU enrichment, burnup, or cycle length of either the metal or oxide fuel SFR because all the TRU vectors having similar fissile plutonium content. Also, the slightly larger presence of americium in the low burnup, long cooling time vector increases its consumption rate in the SFR, and thus increases the production of curium 242 and 244 compared to a high burnup, short cooling time TRU vector.The second set of perturbations involved varying the external feed and reprocessing of the TRU groupings for the metal and oxide SFR designs. Four separation technologies were applied to the LWR SNF; PUREX, UREX+2/+3, UREX+4, and UREX+1a. In the case of metal fuel, this perturbation only affects the feed of isotopes coming from the separation facility, while the electrochemical reprocessing recycles all TRU isotopes from the SFR back into the reactor core as fuel. This is different from the oxide case, in which the four separation technologies (PUREX and UREX+) may also be applied to the reprocessing of the SFR fuel. In the case of PUREX, for example, the neptunium, americium, curium, berkelium, and californium are separated from the discharged fuel reprocessing and assumed to be disposed of, thus creating fresh plutonium-only oxide fuel.The effects of the choice of separation and reprocessing strategy on the neutron emission, gamma energy, and decay heat at beginning-of-equilibrium cycle (BOEC) and the decay heat at end-ofequilibrium cycle (EOEC) were also incorporated into this study. The effects of different 'groupings' were found to have a minimal effect on the parameters mentioned above for the metal fuel SFR, since all TRU isotopes are homogeneously recycled back into the core. In the case of an oxide fuel SFR, the BOEC charge neutron emission, gamma energy, and decay heat all decr...

Preliminary studies of used fuel generated in the US Department of Energy's Advanced Fuel Cycle Initiative have indicated that current used fuel transport casks may be insufficient for the transportation of said fuel. This work considers transport of three 5-year-cooled oxide advanced burner reactor used fuel assemblies with a burn-up of 160 MWD kg 21 . A transport cask designed to carry these assemblies is proposed. This design employs a 7-cm-thick lead gamma shield and a 20-cm-thick NS-4-FR composite neutron shield. The temperature profile within the cask, from its centre to its exterior surface, is determined by two-dimensional computational fluid dynamics simulations of conduction, convection and radiation within the cask. Simulations are performed for a cask with a smooth external surface and various neutron shield thicknesses. Separate simulations are performed for a cask with a corrugated external surface and a neutron shield thickness that satisfies shielding constraints. Resulting temperature profiles indicate that a threeassembly cask with a smooth external surface will meet fuel cladding temperature requirements but will cause outer surface temperatures to exceed the regulatory limit. A cask with a corrugated external surface will not exceed the limits for both the fuel cladding and outer surface temperatures.

SUMMARYFrom a physics standpoint, it is feasible to sustain continuous multi-recycle in either thermal or fast reactors. In Fiscal Year 2009, transmutation work at INL provided important new insight, caveats, and tools on multi-recycle. This work entails new data and calculation methods for systematic evaluation of fuel cycle options, allowing comparison of key physics related in-core and out-of-core performances.Multi-recycle of MOX, even with all the transuranics, is possible provided continuous enrichment of the uranium phase to ~6.5% while limiting the transuranic enrichment to slightly less than 8% to satisfy the expected void reactivity constraint. Multi-recycle of heterogeneous-IMF assemblies is possible with continuous enrichment of the UOX pins to ~4.95% and having 60 of the 264 fuel pins being intermatrix. A new tool enables quick assessment of the impact of different cooling times on isotopic evolution. The effect of cooling time was found to be almost as controlling on higher mass actinide concentrations in fuel as the selection of thermal versus fast neutron spectra. A new dataset was built which provides on-the-fly estimates of gamma and neutron dose in MOX fuels as a function of the isotopic evolution. All studies this year focused on the impact of dynamic feedback due to choices made in option space. Both the equilibrium fuel cycle concentrations and the transient time to reach equilibrium for each isotope were evaluated over a range of reactor, reprocessing and cooling time combinations. New bounding cases and analysis methods for evaluating both reactor void reactivity and radiation worker safety were established. This holistic collection of physics analyses and methods gives improved resolution of fuel cycle options, and impacts thereof, over that of previous ad-hoc and singlepoint analyses.The buildup of problem isotopes in both thermal and fast systems was found to be controlled by the presence of gateway isotopes in the fuel. Gateway isotopes are governed by similar transmutation physics as U-238 but instead of breeding Pu-239, they breed curium and the higher mass actinides. It is the buildup of these transmutation products, Cm, Bk, and Cf, which pose an issue to out-of-core fuel handling operations because of their associated intense decay heat and radiation fields. Gateway Pu-242 and Am-243 are formed in Light Water Reactors (LWR) and then are externally fed to the burner reactor as its make-up fuel. The external supply of these gateway isotopes behaves as an external driving force towards the creation and buildup of Cm-Bk-Cf in the fuel cycle, analogous to plutonium breeding from uranium. The lower the burner reactor's conversion ratio, the higher the external feed of LWR TRU and therefore the gateway isotopes. Hence, the Cm-Bk-Cf buildup over successive recycles is greater for lower conversion ratio. In this report, the authors consider the dynamic transmutation feedback caused by gateway isotopes in burner reactors: MOX-UE, heterogeneous-IMF and Sodium cooled Fast Reactor (SFR). The p...