One-Dimensional Model for Fission Product Plate out and Circulating Coolant Activities in a HTGR

Numerical prediction of fission product plateout and circulating coolant activities under normal operating conditions are crucial in the design of a high temperature gas-cooled reactor (HTGR). The results are used in the design of the purification system and the shielding of the components of the coolant systems for maintenance and repair. In addition, circulating coolant activities and plateout fission products significantly contribute to early source terms under loss of coolant accident scenarios. A development of a new computer code named POSCA (Plate-Out Surface and Circulating Activities) has been in progress targeting simulations of hundreds of nuclides during whole periods of reactor life time. This paper presents the numerical model of the POSCA code. In order to confirm the accuracy and reliability of the numerical model, a simple benchmark problem has been solved using POSCA and compared with analytical solutions. In this work, the numerical model of the POSCA code to predict the fission produce plateout and the circulating coolant activities was presented and it was benchmarked against the analytic solutions of a single loop problem.