b'Design and Evaluation of aNew crystal development process provides pathway to produce laser crystals Nuclear Pumped Laser Detectorfaster and cheaper than previously possible.for Reactor Power Indication M easuring reactor and experiment power over time in test reactors, especially transient reactors, is an existing challenge. The emergence of autonomous small or micro-reactor systems will require accurate active power measurement that may be distributed at several axial and radial locations across the core. Flux and fission wires can be used to measure total fluence in the specimen in-reactor experiments but cannot provide power history or online data TOTAL APPROVED AMOUNT:to intelligent controls or autonomous applications. Ion and fission chambers are $776,129 over 3 years typically too large to be used within small systems and cannot operate accurately at the power range seen during transient operations. A new instrument is needed to PROJECT NUMBER:measure reactor and specimen power.19A39-146Flux in an operating nuclear reactor can be used to pump yttrium aluminum garnet PRINCIPAL INVESTIGATOR:(YAG) lasers. The power output from the laser is proportional to reactor power with Andy Beasley a very fast response time. Doping the YAG crystal with uranium or plutonium allows CO-INVESTIGATORS: thermal or fast neutron flux to pump the laser. By measuring the difference between Adrian Wagner, INL undoped and doped laser output, reactor power and thermal/fast neutron flux can Scott Watson, INL be determined over the range of reactor power of interest to researchers.Mark Prelas, University of Missouri This research resulted in new methodologies to develop polycrystalline undoped COLLABORATOR: and uranium doped YAG crystals. A new additive manufacturing process was Purdue University developed to produce zirconium dioxide doped with 10% uranium dioxide, which was necessary as part of the YAG crystal manufacturing process. The YAG crystals were sized to give proper output over the expected flux for steady-state and transient reactor operations in the Neutron Radiography and Transient Reactor Test reactors, but larger crystals are achievable. This new process can produce laser crystals much faster and cheaper than the typical single crystal growing method.TALENT PIPELINE:Brian Bettes, student at Purdue UniversityPatrick Moo, student at University of FloridaINTELLECTUAL PROPERTY:OBrien, R., and A. Beasley, Solid state nuclear pumped lasing sensors for in-pile reactor power and flux measurement, direct energy conversion, and related methods, U.S. Patent Application No. WO 2021/141882 A1 (July 15, 2021).98 Polycrystalline uranium YAG samples.'