b'The simplified Serpent/MCNP models of an ATR irradiation capsule provide a capability to do quick scoping/sensitivity calculations for configurations of interest to support design of experimental irradiations. Reduced diameter fuel samplescalculations of the radial power and to increase the power density andburnup distributions as a function of hence increase the burnup accu- irradiation time for full and reduced mulation rate at the Advanced Testdiameter test pellets.Fixed source Reactor (ATR), generically termedcalculations were performed with FAST Serpent for nominal and half-diameterMiniFuel irradiation tests at Oakfuel pellets for a range of linear-heat-Ridge National Laboratory (ORNL) generation-rates (LHGR) typical of Project Description: those for a PWR to determine the To support the LWR FAST experi- radial power and burnup distribu-mental activities, simplified two- tions as a function of irradiation dimensional models for the irradiationtime.The objective of the Brookhaven capsule in the I22 position in the ATRNational Laboratory (BNL) activities were developed for the MCNP andis to provide a capability to do quick Serpent Monte Carlo codes based onscoping/sensitivity calculations for an MCNP model provided by Idahoconfigurations of interest to support National Laboratory (INL).Thedesign of experimental irradiations.geometry for the capsule is shown inAccomplishments:Figure 1.There are three (3) locationsFixed source calculations were for the insertion of the test specimens. performed as described above for the Shown in the figure is a full diameterirradiation of full and half-diameter pressurized water reactor (PWR) fuelUO2 fuel pellets in the I22 location in rod that is segmented into ten (10)ATR for several LHGR characteristic of radial zones. A simplified surfacethose for a commercial PWR. Typical source based on information providedrelative radial power distribution are by INL for the flux at the I22 posi- shown in Figure 2 for cases with a tion in the ATR was utilized for initial 2020|AFC ACCOMPLISHMENTS 123'