COCOSYS analysis on aerosol wash-down of THAI-AW3 experiment and generic containment

Abstract

During severe accidents, fission products as aerosols are released into the containment and consequently deposited on walls. The condensate flow on walls could wash the deposited aerosols downwards to the sump. Therefore, the aerosol wash-down process on walls is significant to evaluate radioactive source term distribution in nuclear containment. In this paper, the containment code COCOSYS coupled with aerosol wash-down model AULA and condensate coverage model CONRAG is used to analyze the aerosol wash-down process of THAI-AW3 experiment and ‘Generic Containment’. THAI-AW3 experiment was conducted by Becker Technologies to investigate insoluble aerosol wash-down behavior from the vertical, quasi-horizontal surfaces, and a small puddle. The COCOSYS calculated results shows the aerosol wash-down is predicted well, as well as the thermal-hydraulics in THAI-AW3 experiment. There are no significant differences of aerosol wash-down efficiency between the calculation and measurement. The acceptable COCOSYS is to enable further analysis on the aerosol wash-down process of the Generic Containment within SARNET2 activity under a full severe accident scenario in order to test the aerosol wash-down model. The evolutions of the containment’ thermal-hydraulics are analysed. The calculation offers the aerosol distribution, the aerosol wash-down mass, and the aerosol distribution inside containment over time. The comparisons with previous COCOSYS simulations indicate that the modification of COCOSYS, e.g. the coupling with condensate coverage model CONRAG, is necessary to investigate the aerosol wash-down.