Post‐encapsulation plutonia reduction for Galileo and Ulysses GPHS modules: The module reduction and monitoring facility (MRMF)

In heat source systems of the type C/Ir/PuO2, ingrowth of CO and CO2 is evident. This is due to a cyclical reaction between the C and PuO2 constituents. Gas tap results show that repeated exchanges using a pure inert gas backfill reduces the CO/CO2 ingrowth rate. Also, the temperatures experienced during Radioisotope Thermoelectric Generator (RTG) processing reduces further the effect such that normal RTG storage temperatures do not result in this deleterious effect. A 36‐station vacuum/inert gas manifold has been developed at Mound Facility to serve as a Module Reduction and Monitoring Facility (MRMF) for up to 68 GPHS‐type heat source modules. This method of storage effectively prevented atmospheric contamination of modules while reducing the CO/CO2 ingrowth rate. This paper describes in detail the theoretical, practical, facility, and quality/reliability aspects of this processing facility that has supported the Galileo and Ulysses RTG programs.