Nuclear Safeguards Considerations For The Pebble Bed Modular Reactor (PBMR)

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

“…Consequently, a non-zero "material unaccounted for" is to be expected at such facilities. Such uncertainties have already been reported at the HTR-10 in China, where there was "uncertainty about the precise number of pebbles in the core, because the redundant facility pebble-counters did not exactly agree" (Durst et al 2009). This problem would be compounded in a commercial-scale reactor such as the Xe-100, which would have 10 times as many pebbles as the HTR-10.…”

“…After reviewing this issue in 2006, DOE researchers found that although HTGR spent fuel would be technically challenging to reprocess, it would still be attractive to potential proliferators as a source of material for nuclear weapons (Durst et al 2009). A 2010 Areva (now Framatome) study similarly concluded that:…”

“…However, even if it were possible to uniquely identify each pebble, it would not be practical to use the identifier to track each item throughout the facility in real time. DOE researchers have pointed out that "the declaration and accounting of such large numbers of fuel pebbles individually would be onerous" and concluded that existing reactor safeguards approaches would not work for pebble-bed reactors (Durst et al 2009). Instead, the DOE researchers proposed a new approach that more closely resembles safeguards at bulk-handling facilities (such as nuclear fuel fabrication plants) than those applied at traditional reactors.…”

“…Therefore, instead of trying to count and keep track of every individual fuel pebble, operators would use radiationbased fuel flow monitors, designed to detect anomalies in the pebble streams (Durst et al 2009). Such systems would have to be sensitive enough to distinguish signals caused by fuel diversions from normal statistical variations, and would also have uncertainties.…”

“…If such measures were to be lost temporarily-for instance, if a surveillance camera stopped working-then the only way to recover continuity of knowledge would be to conduct a time-consuming inventory of all material at the facility. Also, in contrast with LWR spent fuel, safeguards inspectors would not be able to directly observe pebble-bed reactor spent fuel in storage (Durst et al 2009). At LWRs, spent fuel is stored below several meters of water, providing radiation shielding but allowing inspectors to view the spent fuel.…”