Installation and Final Testing of an On-Line, Multi-Spectrometer Fission Product Monitoring System (FPMS) to Support Advanced Gas Reactor (AGR) Fuel Testing and Qualification in the Advanced Test Reactor

Abstract

Abstract-The US Department of Energy (DOE) is initiating tests of reactor fuel for use in an Advanced Gas Reactor (AGR).The AGR will use helium coolant, a low-power-density graphitemoderated core, and coated-particle fuel. A series of eight (8) fuel irradiation tests are planned for the Idaho National Laboratory's (INL's) Advanced Test Reactor (ATR). One important measure of fuel performance in these tests is quantification of the fission gas releases over the nominal 2-year duration of each irradiation experiment. This test objective will be met using the AGR Fission Product Monitoring System (FPMS) which includes seven (7) online detection stations viewing each of the six test capsule effluent lines (plus one spare). Each station incorporates both a heavilyshielded high-purity germanium (HPGe) gamma-ray spectrometer for quantification of the isotopic releases, and a NaI(Tl) scintillation detector to monitor the total count rate and identify the timing of the releases. The AGR-1 experiment will begin irradiation in December 2006. To support this experiment, the FPMS has been completely assembled, tested, and calibrated in a laboratory at the INL, and then reassembled in its final location in the ATR reactor basement. This paper presents the details of the equipment performance, the control and acquisition software, the installation in the ATR basement, and the test monitoring plan.

Determination of the Agr-1 Capsule to FPMS Spectrometer Transport Volumes From Leadout Flow Test Data

“…A plot of the FPMS-measured activity of 23 Ne at detector G5 (monitoring the effluent stream of capsule 5) over the course of the leadout flow experiment on capsule 5 is presented in Figure 2. Each plotted point is the 23 Ne activity (in microCuries per 58 cm 3 ) measured during a 20 minute spectral acquisition period. The effect of the increased decay time due to the sequentially decreasing outlet flow rate is reflected in the decreasing 23 Ne activity at the detector.…”

“…Measured 23 Ne activities and their uncertainties (Bq 1 ) during the leadout flow experiment are available at 20 minute intervals from the FPMS spectral data analyses. The viewed sample volume V S has been measured (by filling with water and weighing) and by calculation from the fabrication prints to have a volume of 58 2 cm 3 . Engineering estimates for the average capsule flow volume are V cap = 13 4 cm 3 .…”

“…To provide this important data for the inert fission gas releases, a Fission Product Monitoring System (FPMS) has been developed and implemented to monitor the individual capsule effluents for radioactive species. 3 In order to derive certain fuel performance parameters (most significantly isotopic release-to-birth ratios) the fission gas data measured at the FPMS must be corrected for decay during the transport time from the constantly-irradiated fuel capsule to the FPMS measurement location. Since the capsule effluent gas flow rates change according to the desired experimental conditions, it is convenient to define a capsule-to-FPMS transport volume that is a function of the hardware installation and then determine the desired transport time from this volume and the measured outlet flow rate.…”

“…Figure 1 Simplified flow diagram of the AGR-1 effluent monitoring system effluent from its associated test train capsule. Thus, each spectrum when analyzed provides the activity of fission gases in 58 cm 3 of the flowing gas stream from the associated capsule. An important parameter needed to relate this effluent gas concentration data to fuel behavior characteristics is the decay correction that must be applied to the FPMS-measured activity data to correct the radioactive fission gases for their decay during transport to the measurement station.…”

“…This system has been described elsewhere. 3 Each spectrometer views a 58 2 cm 3 volume of the gas through the leadout volume did not occur, a helium (He) gas supply is provided to the leadout. The gas supply flow rate is adjustable and the leadout pressure is monitored.…”