Development of Tritium Behavior Analysis Code for Very High Temperature Gas-Cooled Reactor

Tritium is generated by a ternary fission reaction in TRISO coated fuel particles as well as by neutron absorption reactions with 6Li, 10B, 3He, etc, which are present in core graphite of VHTR and helium coolant, respectively. Since VHTR uses helium gas as its coolant, tritium can be readily diffused to other components in the system. In addition, because of tritium's higher diffusivity even in unbroken materials, the behavior in the VHTR system needs to be treated more importantly in the licensing point of view for its construction. In particular, the tritium activity concentration in the product hydrogen and in the components of the hydrogen plant should be adequately evaluated in order to confirm that regulatory requirements can be satisfied. In this respect, KAERI has developed tritium behavior analysis code for VHTR, which contributes to put a basis for the quantitative analysis of tritium behavior in a variety of environments of the VHTR system