STUDY ON TRITIUM RELEASE FROM SOLID BREEDING MATERIALS USING THE RESEARCH REACTOR YAYOI

Tritium release behavior from solid breeding materials was studied in order to clarify the mechanism of migration process. In-situ tritium r elease experiments (TTTEx) and in-situ luminescence measurements from radiation defects using the research reactor YAYOI at the University o f Tokyo played important roles in these studies combining with off-pil e experiments and modeling studies. In in-situ tritium release experim ents, intra-grain and grain boundary diffusivities were separately eva luated. The chemical from of the released tritium was found to be dete rmined by the oxygen potential in the system. Surface reaction, which often becomes the rate determining step in tritium release, was intens ively studied. The surface reaction rate was found to be determined by the oxygen potential in the system and swamping reaction with H-2 or H2O. It was also suggested that at low oxygen potential bonding streng th of surface -OT differs from that at high oxygen potential. This was also supported by off-pile infrared absorption study of surface -OH. Tritium surface reaction model (DAD) was constructed based on these re sults. The tritium residence time agreed well with experimental result s. In order to study the behavior of radiation defects and its interac tion with tritium migration behavior, in-situ luminescence measurement and tritium release experiments under reactor irradiation at high tem perature and under controlled atmosphere were conducted. As a first st ep, defects behavior under irradiation was studied. (C)1997 Elsevier S cience Ltd.