Fission product plateout calculations for a gas turbine HTGR

Fission product plateout distributions for a direct cycle gas turbine high-temperature gas-cooled reactor (GT-HTGR) were calculated. This reactor concept uses a helium gas turbine power conversion system with all major components integrated into a prestressed concrete reactor vessel. The magnitude and distribution of fission product contaminants is important in the plant design phase for developing maintenance and handling procedures. Plateout distributions for 137Cs, 140La, Te, 90Sr, /sup 110m/Ag, and 131I have been calculated using a modified version of the computer code PAD. A major uncertainty is lack of adsorption data on the materials of interest. Perfect sink (i.e., no desorption) behavior was assumed for La, Te, Ag, and Sr. A sensitivity calculation was performed on the diffusion coefficient and mass transfer coefficients for Ag. Similarly, a sensitivity analysis for the adsorption isotherms for Cs and I is discussed. Recommendations are made for further work needed to determine design activity levels for the GT-HTGR system. (U.S.)