Pressurization of Sealed Pu-238 Bearing Containers in Design Basis Accidents: Analysis and Risk Reduction

摘要

Plutonium-238 has been used since the 1960’s as the fuel in various Radioisotope Thermoelectric Generator (RTGs)systems to power numerous NASA space systems. Most recently, Los Alamos manufactured Plutonium-238 heatsources to power the Cassini-Huygens mission to Saturn, the Pluto New Horizons mission and the Mars ScienceLaboratory Rover. Plutonium-238 is an ideal material for space power applications due to its high curie content,which is proportional to the decay heat of the material. When Plutonium-238 decays, an energetic, ionized heliumatom is also released. Helium gas generation and subsequent pressure build-up in sealed containers is a primary areaof concern at the Plutonium Facility due to the high specific activity of Plutonium-238 (17 Ci/g for Pu-238compared to 0.062 Ci/g for Pu-239). Therefore, many of the bounding design basis accidents at the PlutoniumFacility in Los Alamos involve the potential release of Plutonium-238 oxides. As part of an overall effort to improvethe safety posture of the nuclear facility, we developed a container capable of maintaining confinement ofPlutonium-238 oxides for long times during normal storage and handling conditions and when exposed to facilitydesign basis accidents. The storage container was designed and tested to meet facility design basis accidentperformance criteria and the requirements of the DOE M441.1-1 Nuclear Material Packaging Manual (hereafterreferred to only as the “Packaging Manual”. The analysis techniques and methodology for the development of thestorage container is presented along with testing performed to demonstrate Packaging Manual compliance. Inaddition, techniques developed for rapid assessment of the over-pressurization hazard of legacy Plutonium-238bearing containers, where design basis information is incomplete or unavailable, are presented.