A study on low-pressure subcooled flow boiling using RELAP5/MOD3.4

Subcooled flow boiling is an important thermal hydraulic phenomenon in PWR core analysis, especially for accident analysis. Generally, RELAP5/MOD3.4 is adequate for modeling high-pressure subcooled boiling. However, there is a lack of assessing the code's capability of modeling low-pressure sub-cooled boiling. In this paper, the capability of RELAP5/MOD3.4 of modeling low-pressure subcooled boiling is analyzed and assessed, and the results show that it is not applicable. In order to improve the performance, code modifications are made and evaluated. The assessment results show that the performance of modified code of modeling subcooled boiling is improved obviously.