ACTIVITY TRANSPORT IN VESSEL-TYPE PHWRS

A simple mathematical model is presented describing the time evolution of radiation fields in a pressurized heavy-water reactor (PHWR) upon removal of the main radionuclide source (in-situ activated Stellite in -core components). The model is also extended to analyze the recontami nation behavior of critical components after they are decontaminated. The basic properties of the materials, including their rates of corros ion and the release to the water, are lumped into a phenomenological c onstant, The procedure applied precludes an absolute calculation of th is parameter. but facilitates the description of the impact caused by changes in the materials' performance upon the time evolution of radia tion fields.