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The AGR-1 experiment is a fueled multiple-capsule irradiation experiment being conducted in the Advanced Test Reactor (ATR) in support of the Advanced Gas Reactor (AGR) Fuel Development and Qualification Program. A flow experiment conducted during the AGR-1 irradiation provided data that included the effect of flow rate changes on the decay of a short-lived radionuclide ( 23 Ne). This data has been analyzed to determine the capsule-specific downstream transport volume through which the capsule effluents must pass before arrival at the fission product monitoring system spectrometers. These resultant transport volumes when coupled with capsule outlet flow rates determine the transport times from capsule-to-detector. In this work an analysis protocol is developed and applied in order to determine capsule-specific transport volumes to precisions of better than 7%.

PCGAP is a software package, which was written to provide gamma-ray pulse height spectrum analysis on a personal computer platform using the Windows NT operating system. It is a collection of programs, which provide a wide range of operability extending from the single user environment to the general purpose counting room. Included in the package are necessary data structures and libraries used to compute quantitative radionuclide concentrations. PCGAP also contains techniques to decontaminate photopeak interferences; determine activity concentrations for radionuclides independent of their associated spectral photopeak size; and three methods to determine the energy scale of a spectrum.PCGAP performs a non-linear least squares fitting of a Gaussian function to spectral photopeaks. The fitting algorithm can fit up to five concurrent photopeaks using a common spectral background. The package includes a program that will automatically locate spectral photopeaks, fit them to a Gaussian function, identify the radionuclides associated with the found photopeaks, and compute a net activity concentration, and for an 8K spectrum do it in less than 30 seconds on a reasonably configured PC. PCGAP also includes a program which allows the operator to manually (using mouse clicks) identify photopeak locations, fit limits and background positions, initiate a fit to the photopeaks and then display the resulting Gaussian function forms. This interactive display function is particularly useful to resolve or properly fit photopeaks with complex adjacent structure and for photopeaks that are near the limit of detection.iv

The US Department of Energy has embarked on a series of tests of TRISO-coated particle reactor fuel intended for use in the Very High Temperature Reactor (VHTR) as part of the Advanced Gas Reactor (AGR) program. The AGR-1 TRISO fuel experiment, currently underway, is the first in a series of eight fuel tests planned for irradiation in the Advanced Test Reactor (ATR) located at the Idaho National Laboratory (INL). The AGR-1 experiment reached a peak compact averaged burn up of 9% FIMA with no known TRISO fuel particle failures in March 2008. The burnup goal for the majority of the fuel compacts is to have a compact averaged burnup greater than 18% FIMA and a minimum compact averaged burnup of 14% FIMA.At the INL the TRISO fuel in the AGR-1 experiment is closely monitored while it is being irradiated in the ATR. The effluent monitoring system used for the AGR-1 fuel is the Fission Product Monitoring System (FPMS). The FPMS is a valuable tool that provides near real-time data indicative of the AGR-1 test fuel performance and incorporates both highpurity germanium (HPGe) gamma-ray spectrometers and sodium iodide [NaI(Tl)] scintillation detector-based gross radiation monitors.To quantify the fuel performance, release-to-birth ratios (R/B's) of radioactive fission gases are computed. The gamma-ray spectra acquired by the AGR-1 FPMS are analyzed and used to determine the released activities of specific fission gases, while a dedicated detector provides near-real time count rate information. Isotopic build up and depletion calculations provide the associated isotopic birth rates. This paper highlights the features of the FPMS, encompassing the equipment, methods and measures that enable the calculation of the release-to-birth ratios. Some preliminary results from the AGR-1 experiment are also presented.