Under the guidance of the Nuclear Science Committee (NSC) and the mandate of the Working Party on Scientific Issues of the Fuel Cycle (WPFC), the objective of the Task Force on Homogeneous versus Heterogeneous Recycle of Minor Actinides in Fast Reactors (TFHH) is to compare the different studies that have been performed in several international laboratories. In particular, this new effort will compare the criteria for a choice between homogeneous and heterogeneous recycle modes, the specific scenarios for implementation, potential non-proliferation issues, strategies for Cm management, etc. Moreover, the study will point out the potential impact, both on the reactor core and on the power plant (i.e., lay-out, maintenance, availability etc). Fuel and target related issues will be summarised with respect to potential limitations on maximum allowable Minor Actinides (MA) content, residence time, helium production and management, remote fabrication implications, etc These evaluation will reflect previous and ongoing or planned irradiation programs. Specific scenario studies will be also suggested, in order to underline specific needs and requirements, both for the short and long term. The study should enable reaching a deeper understanding and consensus on key issues and potential limitations, and allow making recommendations for further analytical and / or experimental demonstrations if needed.
Partitioning and Transmutation strategies based on critical fast reactors have been investigated in several countries, aiming at the transmutation of MA. Different approaches for implementation have been proposed, and in particular the homogeneous recycle of all (not separated) transuranics (TRU) in the fuel loaded in the fast reactor core, independent of the fuel form (e.g., oxide or metal) and of the coolant type (sodium, lead, gas). An alternative to homogeneous recycle in fast reactors could be to separate out the less radioactive component of the LWR spent nuclear fuel TRU (e.g., Pu or combined Np with Pu) in order to make driver fuels, and manage the remaining minor actinides (primarily Am and Cm and Np) in target fuels/assemblies or stored as waste either permanently or intermediately for future irradiation. Consequently, the driver and target fuels can be managed separately in the fuel cycle. This separate management and recycle of the Pu driver and MA target fuels constitutes heterogeneous recycle.
Potential advantages and disadvantages of both recycle modes have been pointed out and investigated in different institutions. Most of the crucial issues are related to the fuel cycle characteristics (impact on the fuel fabrication installations etc) and to the fuel forms (fabrication, characterization, performance evaluation under irradiation etc).
The different international studies offer often different perspectives and are based on different objectives, hypotheses and on different experimental results. For example, studies and assessments on MA targets have identified a variety of challenges, and indicated that target design and implementation strategies still require development, despite different perspectives, objectives and background of the different studies.
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Working Party on Scientific Issues of the Fuel Cycle (WPFC)
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For more information on this working party, please contact Yong-Joon CHOI (Tel: +33 1 45 24 10 91, yongjoon.choi@oecd.org)
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