Computations of post-trip reactor core thermal hydraulics using a strain parameter turbulence model

Coated plutonia particle fuel has been proposed recently for use in radioisotope power systems and radioisotope heater units for a variety of space missions requiring power levels from milliwatts to tens or even hundreds of watts. The 238PuO2 fuel kernels are coated with a strong layer of ZrC designed to fully retain the helium gas generated by the radioactive decay of 238Pu. A recent investigation has concluded that helium retention in large-grain ( > 200 mu m) granular and polycrystalline fuel kernels is possible even at high-temperatures (> 1700 K). Results of performance analysis showed that this fuel form could increase by 2.3-2.4 times the thermal power output of a light weight radioisotope heater unit. These figures are for a single-size (500 mu m) particles compact, assuming 10% and 5% helium gas release respectively, and a fuel temperature of 1723 K, following 10 years of storage. A binary-size (300 and 1200 mu m) particles compact increases the thermal power output of the RHU by an additional 15%.