b'Effect of Diamond Doping on the Fission Gas ReleaseIn UO 2Fuel Irradiated to 7.2 GWd/tHM.Principal Investigator: Pavel Medvedevto assess the ability of diamond, a material with the highest thermal conductivity of any known material, to improve the performance of the UO 2fuel.The concept of using diamond for this purpose, along with the fabrication method and characterization is well documented (Chen et al., 2015; Morrell, 2015).Results of the PIE of selected ATF-1 rodlets have been reported recently (Cappia, 2019).It was found that UO 2pellets doped with 5 vol % diamond exhibited a fission gas release of 1.08%. In order to determine whether the diamond doping had an impact on the fuel performance, fuel performance modeling was carried out to calculate fission gas release in undoped UO 2Figure 1. Comparison of theA n array of innovative fuels andunder identical irradiation conditions.calculated peak fuel temperaturematerials combinations hasResults of these calculations are the for the standard UO 2fuel and UO 2 - been irradiated in the Advancedmain subject of the present paper.5 vol % diamond composite.Test Reactor (ATR) at Idaho NationalBISON, a modern finite-element based Laboratory (INL) with an objectivenuclear fuel performance code, was to develop an Accident Tolerant Fuelutilized for the analysis presented (ATF) in response to the Fukushimahere.BISON has been under devel-accident.ATF-1 is an initial testopment at the INL since 2009. The series whose irradiation commencedBISON light water reactor (LWR) vali-in 2015.Detailed description ofdation database includes 73 integral the ATF-1 test matrix, experimentfuel rod assessment cases evidencing design, irradiation conditions andthat simulation results compare quite the current status of irradiation andwell with LWR experimental measure-postirradiation examination (PIE) hasments.Good agreement between been provided (Core et al., 2017). predicted and measured low burnup UO 2pellets doped with 5 vol %fission gas release is specifically called diamond fabricated by spark plasmaout (Assessment of BISON, 2018), sintering were included in the ATF-1making BISON particularly suitable for irradiation experiment in an effortthe present work.156 2019|AFC ACCOMPLISHMENTS'