AGR-5/6/7 Experiment Monitoring and Simulation Progress

Abstract

Advanced Gas Reactor (AGR)-5/6/7 is the last of a series of experiments conducted in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL) in support of development and qualification of tri-structural isotropic (TRISO) low-enriched fuel for use in high-temperature gas-cooled reactors. The test train contains five separate capsules that are independently controlled and monitored. Each capsule contains multiple 12.51-mm-long compacts filled with low-enriched uranium carbide/oxide (UCO) TRISO fuel particles. The objectives of the AGR-5/6/7 experiment are to: 1. Irradiate reference-design fuel particles to support fuel qualification. 2. Establish operating margins for the fuel beyond normal operating conditions. 3. Provide irradiated-fuel performance data and irradiated-fuel samples for post-irradiation examination (PIE) and safety testing. vi Capsule 1 occurred from the fourth cycle (164B), and were rigorously mitigated to minimize fission product crosstalk between capsules. This gas line problem prevented fission product release measurement for Capsule 1 during the last three cycles and caused various fission gas leakage events into the other four capsules. By the end of the sixth cycle, 166A, a significant number of in-pile particle failures occurred in Capsule 1, causing a substantial increase in R/B values. In addition, numerous particle failures were observed in Capsule 3 and perhaps a small number of failures might have occurred in Capsule 2 during the last cycle, 168A. In contrast, no in-pile failures are likely in the top two capsules (4 and 5) based on absence of the typical spike in gross gamma counts and low failure estimates by the end of Cycle 168A using the AGR-3/4 R/B per exposed kernel model. Increased and unstable R/Bs in Capsules 4 and 5 can be contributed to fission gas leakage from Capsule 1.

"Advanced" isn't Always Better: Assessing the Safety, Security, and Environmental Impacts of Non-Light-Water Nuclear Reactors

“…Three of the irradiation capsules containing fuel for the formal qualification tests eventually lost all functioning thermocouples, so that critical temperature data were not obtained for a number of irradiation cycles. And in 2019, one of the capsules suddenly began releasing fission products at a high enough rate to exceed the yearly dose limit for operation of the Advanced Test Reactor, requiring operators to isolate the capsule and stop collecting fission product release data from it (Pham et al 2020). There is little public information about what impact these problems will have on completion of the program.…”

“…Operator errors could enable such an accident (Carlson 2014). Water and/or air ingress is suspected as the cause of the large number of TRISO particle failures and subsequent high fission product releases that occurred in one of the capsules during the AGR-5/6/7 irradiation at the Advanced Test Reactor at the INL-high enough to exceed a downwind annual radiation dose limit (Palmer 2020;Pham et al 2020).…”

“…However, it is unlikely that X-Energy's TRISO fuel will be able to achieve such a high burnup, at least in the near term. Because the AGR-5/6/7 tests previously described at Idaho National Laboratory were not completed (Pham et al 2020), the peak fuel burnup achieved was likely only about 15.3 percent, or 148,000 MWd/MTHM, falling short of the Xe-100 target burnup and the original test goal of 19.1 percent (Palmer 2019). The NRC is not likely to approve a peak burnup greater than-or even close to-this value for the planned Xe-100 demonstration plant.…”

“…Moreover, due to the problems encountered during the irradiations described above, there are gaps in the data and the program may never fully achieve its goals. In particular, the AGR-5/6/7 irradiation tests, which were intended to serve as a formal program to qualify TRISO fuel under both normal and abnormal operating conditions, were terminated prematurely (Pham et al 2020). It is unclear whether the data that was collected will be adequate for finalizing fuel fabrication specifications and for the requisite NRC approval for use of the fuel.…”

Analysis and Design for Irradiation of High Power TRISO Fuel Compact Specimens in HFIR

“…The AGR UCO particles have similar diameters to the fuel that will be used in the KP-FHR, and the particles are expected to reach particle powers near 1,000 mW/particle during HFIR irradiation. This peak power will be substantially higher than in previous AGR tests, which were ~100 mW/particle for AGR-1, ~150 mW/particle (UCO) and ~200 mW/particle (UO 2 ) for AGR-2, and ~200 mW/particle (expected) for AGR-5/6/7 [9,10,11]. The higher-power irradiation testing could potentially allow for higher KP-FHR powers [5].…”