Hydrogen injection in BWR and related radiation chemistry

Abstract

Hydrogen injection to feed water systems in boiling water reactors (BWR) has drawn wide attention as one of the possible countermeasures to the stress corrosion cracking (SCC) of 304 type stainless steel piping. To confirm the effectiveness of the hydrogen injection, a computer simulation of the complicated radiolysis reactions was carried out. The result of the simulation showed that the reactor water data monitored at the usual sampling points in actual plants reflect mainly the reactions in the downcomer portion but not in the reactor core in BWR. The calculation claimed approximately 300 ppb hydrogen in feed water to reduce the oxygen concentration in the recirculation lines to a negligible level, while one order of magnitude higher level of hydrogen is necessary to suppress oxygen in the reactor core. The computer simulation requires many radiation chemical data as in-put, among which are G values of initial products for water radiolysis at high temperature. An experimental approach was made to confirm the G values for high temperature radiolysis of water. The result does not seem to be consistent with the high temperature G values reported by Burns.