Verification and validation procedures of calculation codes for determining corrosive conditions in the BWR primary cooling system based on water radiolysis and mixed potential models

Abstract

Corrosive conditions in the BWR primary cooling system are usually expressed by the corrosion index, ECP. In order to determine ECP at any location in the primary cooling system, ECP should be evaluated by computer simulation codes consisting of water radiolysis models to determine the concentrations of corrosive radiolytic species and mixed potential models to determine ECP based on corrosive species. Measures for mitigation of SCC crack growth rate by decreasing ECP are authorized by the JSME Standards; however, measures for mitigation of ECP by hydrogen addition have not been authorized yet. In the paper, standard procedures to authorize the computer simulation codes based on the verification and validation (V&V) method are proposed. The numerical justification of every code applied as a standard code should be verified and its accuracy and applicability for plant analysis should be validated. Benchmark analysis for verification procedures is proposed while a comparison of the calculated results with the measured ones for the evaluated plant is also proposed for the validation procedures. It is strongly recommended that the results of V&V evaluation of the codes that might be applied for evaluation of corrosive conditions in operating power plants are published in a peer-reviewed journal before their application. © 2013 Atomic Energy Society of Japan.