First high temperature safety tests of AGR-1 TRISO fuel with the Fuel Accident Condition Simulator (FACS) furnace

Abstract

Three TRISO fuel compacts from the AGR-1 irradiation experiment were subjected to safety tests at 1600 and 1800°C for approximately 300 h to evaluate the fission product retention characteristics. Silver behavior was dominated by rapid release of an appreciable fraction of the compact inventory (3 to 34%) at the beginning of the tests, believed to be from inventory residing in the compact matrix and outer pyrocarbon (OPyC) prior to the safety test.

AGR-1 Post Irradiation Examination Final Report

“…Complete TRISO failure was evident in only one case (the 1800°C FACS test of Compact 4-3-2); most of the remaining 85 Kr release curves represent diffusion through intact OPyC in particles with failed SiC (the IPyC was also cracked in these cases). Significant 85 Kr release from Compact 4-3-2 appears to be from incremental coating failure in three particles; with a sequence of SiC failure followed by OPyC failure in the first two particles, and only SiC failure in the third particle near the end of the test (Demkowicz et al 2015e).…”

Detection and analysis of particles with failed SiC in AGR-1 fuel compacts

“…Four compacts were safety tested at 1800°C (~16,500 particles). Approximately twenty particles with SiC failures were detected in the three 1800°C compacts included in Table 1 and Table 2; and a fourth compact, Compact 4-3-2, was determined by separate analysis to most likely have had three particles with failed SiC [Demkowicz et al, 2015].…”

“…Rapid release of gaseous radioisotopes of krypton or xenon was used to monitor for TRISO coating failure in individual particles. Detection of this type of coating failure was an extremely rare event, with no occurrences during the three-year AGR-1 irradiation test of approximately 298,000 particles [Scates, 2010] and only two suspect particles in one of the fourteen safety-tested compacts (a compact tested at 1800°C) [Demkowicz et al, 2015].…”

Destructive PIE and Safety Testing of Six AGR-2 UO₂ Capsule 3 Compacts

“…The Compact 3-4-1 safety test was prematurely terminated after holding at 1,700°C for 164 h because escalating cesium release (approaching 9% of the total inventory) might otherwise have resulted in dose rates from fission products on the furnace internals exceeding standard operating limits adhered to for safe hands-on maintenance of the furnace. (Demkowicz et al 2015a). Cesium release from a particle with failed SiC was followed after a short break-through period by a gradual release of 0.085 particle equivalents of 85 Kr over about 80 h (Figure 3-1).…”