Modeling the activity and scaling factor of I-129 in the primary coolant and CVCS resin of operating PWR

Abstract

To estimate the activity of (129)Iat the primary coolant and chemical and volume control system (CVCS) resin in Korean pressurized water reactor (PWR) plants, a theoretical methodology was developed on the basis of an existing model of primary coolant activity and new model of CVCS resin activity. In order to reflect the difference between (129)Iand (137)cS, the different power-related diffusivities in the defective fuel were derived, and the variable removal efficiency of the CVCS resin for Cs-137 was applied as a function of the coolant activity ratio Of I-131/(CS)-C-137. The current computational method was validated by using the measured coolant activities of Cs-137, and the results show better agreement than a previously suggested parameter correlation method between (129)Iand Cs-137. There was also reasonable agreement in a comparison of the results of the test resin columns of the coolant from the PWR plants of other countries. It was shown that the ratio of the effective removal efficiency of (129)Iand Cs-137 in the CVCS resin linearly influences the activity ratio o I-129/Cs-137 in the coolant, but on the other hand, its influence on the activity ratio in the CVCS resin is relatively less sensitive compared with that in the coolant. (C) 2005 Elsevier Ltd. All rights reserved.