The AGR-1 experiment is a fueled multiple-capsule irradiation experiment that was irradiated in the Advanced Test Reactor (ATR) from December 26, 2006 until November 6, 2009 in support of the Very High Temperature Reactor (VHTR) Technology Development Office (TDO) Fuel Development and Qualification program. An important measure of the fuel performance is the quantification of the fission product releases over the duration of the experiment. To provide this data for the inert fission gasses(Kr and Xe), a fission product monitoring system (FPMS) was developed and implemented to monitor the individual capsule effluents for the radioactive species. The FPMS continuously measured the concentrations of various krypton and xenon isotopes in the sweep gas from each AGR-1 capsule to provide an indicator of fuel irradiation performance. Spectrometer systems quantified the concentrations of Kr-85m, Kr-87, Kr-88, Kr-89, Kr-90, Xe-131m, Xe-133, Xe 135, Xe 135m, Xe-137, Xe-138, and Xe-139 accumulated over repeated eight hour counting intervals.-. To determine initial fuel quality and fuel performance, release activity for each isotope of interest was derived from FPMS measurements and paired with a calculation of the corresponding isotopic production or birthrate. The release activities and birthrates were combined to determine Release-to-Birth ratios for the selected nuclides. R/B values provide indicators of initial fuel quality and fuel performance during irradiation. This paper presents a brief summary of the FPMS, the release to birth ratio data for the AGR-1 experiment and preliminary comparisons of AGR-1 experimental fuels data to fission gas release models.

A program has been conducted and is continuing at Battelle Memorial Inst. under the sponsorship of the United States Atomic Energy Commission to study the release of fission gas from UO2 and to relate the release to material properties, both chemical and structural. Work in the program has involved the preparation and characterization of sintered polycrystalline and fused single-crystal UO2 samples, the construction of a beam-tube loop facility for the irradiation of the UO2 under controlled temperature and atmosphere, and the collection and analysis of released fission gases during irradiation. Irradiation experiments have been conducted in purified helium-hydrogen atmosphere at temperatures from 500 to 1500 F, with fission gases continuously collected and analyzed for krypton and xenon during irradiation of natural uranium specimens. Irradiation exposures of the specimens have been in the region of 1018 nvt.