b'4.4 FAST NEUTRON IRRADIATIONRoadmaps and Collaborative Opportunitiesfor Fast Neutron IrradiationsPrincipal Investigators: Nicolas WoolstenhulmeTeam Members/Collaborators: Mike Worrall, Calvin DowneyNeutronic assessmentsI nterest in fast spectrum reactors(ATR, Transient Reactor Test Facility is at an all-time high for the(TREAT), High Flux Isotope Reactor have shown that existingpresent generation of nuclear(HFIR), and Massachusetts Institute thermal spectrumtechnology developers. However,of Technology Reactor (MITR). The test reactors can usedeveloping innovative fast reactoroutcomes of this workshop were spectral modificationfuel designs remains encumberedfruitful, yet somewhat nascent and strategies to supportwithout fast spectrum test reactorshence difficult to describe in concrete meaningful collaborativeavailable in or to the U.S. Irradiationterms. Developers of sodium fast irradiation opportunitiesof fuel rodlets in cadmium-linedreactors (SFR) see opportunities to for fast reactor fuelsbaskets in inner-core positions ofuse existing thermal spectrum reac-and materials. the thermal spectrum Advancedtors but have largely formulated their Test Reactor (ATR) has long beenfirst-generation core design around used to reject thermal neutrons tohistorically proven fuel systems help develop more prototypic radialthus minimizing their needs for power distributions. While useful,new irradiation data. All major SFR this design is not currently capabledevelopers are currently proceeding of housing rodlets long enough forwith construction of demonstration some data needs, nor does it provideplants and can foresee circumstances enough fast neutron flux for studyingwhere interim surveillance can desired effects in materials. Theconfirm that revived historic fuel Advanced Fuel Campaign (AFC)technologies perform as expected. has been investigating other strate- It is also foreseeable that future fuel gies for fast neutron irradiations ininnovations could undergo irradia-recent years, and other collaborativetions in demonstration plants, but opportunities have emerged in thishere data obtained from material test area. A workshop was held andreactors would be rather beneficial neutronic studies were performedin streamlining Nuclear Regulatory in fiscal year 2023 to exploreCommission license amendments for cooperative scenarios more fully. lead test rods/assemblies. Compared to SFRs, developers of alternate Project Description:fast reactor types (helium-cooled, In May 2023 Idaho National Labora- lead-cooled, molten salt) do not tory hosted the first Fast Neutronhave as much performance data for Irradiation Testbed Workshop toestablished fuel technologies. Thus, engage potential users from nationalirradiation tests in existing material labs and industry. A variety of fasttest reactors offer key opportunities reactor and fusion plant developersfor risk reduction. The same was were represented along with thefound to be largely true, and perhaps main four U.S. material test reactors 210 2023|AFC ACCOMPLISHMENTS'