Development of web-based Off-Site Consequence Analysis Program (OSCAP) for extending ILRT intervals and its application

Abstract

For an offsite consequence analysis, MELCOR Accident Consequence Code System (MACCS) II code is widely used as a tool. In this study, the algorithm of web-based Off-Site Consequence Analysis Program (OSCAP) using the MACCS II code was developed for an integrated leak rate test (ILRT) interval extension and Level 3 probabilistic safety assessment (PSA), and verification and validation (V&V) of the program was performed. The main input data of the MACCS II code are meteorological data, population distribution data and source term data. However, it requires lots of time and efforts to generate the main input data for an offsite consequence analysis using the MACCS II code. For example, the meteorological data are collected from each nuclear power site in real time, but the formats of the raw data collected are different from each other as a site. To reduce efforts and time for risk assessments, the web-based OSCAP has an automatic processing module which converts the format of the raw data collected from each site in Korea to the input data format of the MACCS II code. The program also provides an automatic function of converting the latest population data from Statistics Korea, the National Statistical Office, to the population distribution input data format of the MACCS II code. In case of the source term data, the program includes the release fraction of each source term category resulting from Modular Accident Analysis Program (MAAP) code analysis and the core inventory data from ORIGEN code analysis. These analysis results of each plant in Korea are stored in a database module of the web-based OSCAP, so a user could select the defaulted source term data of each plant without handling source term input data. For V&V of the web-based OSCAP, the following analyses were performed. First of all, an offsite consequence analysis for reference plants was carried out using only the MACCS II code, and using the web-based OSCAP based on both methodologies of NUREG-1493 and NEI interim report. Secondly, the results of the offsite consequence analysis were compared with each other. Lastly, a sensitivity analysis was accomplished for the main input data of the meteorological data and the population distribution data using the web-based OSCAP. It is considered that the program can remarkably reduce man-power on performing a periodic risk assessment according to extending ILRT intervals, and Level 3 PSA. Also, the program can be applied to making accident management plan (AMP) and quantitative health objective (QHO), and to the field of public acceptance (PA).