(A) study on the evaluation of the radioactive source term at reactor coolant system of PWR

Abstract

The amount of radioactive materials released from nuclear power plant must be evaluated before construction stage for the shielding design and radioactive systems. Since 1984, any new methodologies are not provided. Especially, although the radionuclide concentration at reactor coolant system is predominant factor at source term evaluation, the base-data measured in USA during the 1980s are not updated. The purpose of this study is to provide the method and evaluation tool for radionuclide concentrations at reactor primary and secondary coolant systems respectively, and to compare the results with those of the well-known and recognized tools. In this study, an evaluation method for radionuclide concentrations at fuel pellet region and primary and secondary coolant systems is suggested and a corresponding code for source term evaluation is developed. The code named as SYCOS (System for Calculation Of Source term) is able to predict the radionuclide concentration of fission product at primary and secondary coolant systems with various reactor design parameters based on the simple calculations. SYCOS uses the simplified equation with the assumption of the steady state condition both for the fission product radioactivity at fuel pellet region and the fission product concentrations at reactor coolant systems. At fuel pellet region, ORIGEN 2 code was used for the calculation of the effective fission yield. The reference system is pressurized water reactor with U-tube steam generator. Also Chemical and Volume Control System and Boron Recovery System are considered as primary coolant purification system and steam generator blowdwon and condensate demineralizer as secondary coolant purification system. By applying SYCOS code to YGN unit 3 and 4 plants, the results are compared with the actual data measured from the object plants and calculation results of PWR-GALE and FSAR (Final Safety Analysis Report) of YGN 3&4. In this study, specifically, the expected fuel defect r...