The prediction of steam generator secondary pH under SGTR condition of HPR1000. (April 2021) - Lu, Changdong
Abstract: The SG secondary pH under SGTR condition is a key factor that affects the iodine partition coefficient and thus affects the SGTR radiological consequence. Higher pH favors a higher iodine partition coefficient and thus a lower radiological consequence. In this paper, the SG secondary pH under SGTR condition of HPR1000 is studied combine with the thermal-hydraulic analysis. A pH evaluation model using chemical equilibrium method is developed, and is validated by comparison with the measured pH. The transient thermal-hydraulic characteristics of SGTR event have been analyzed to determine the time variant chemical concentrations in the SG secondary side. Then, the SG secondary pH as a function of time is calculated by the pH evaluation model. The calculation results indicate that the SG secondary pH decreases from the initial value of 9.1 to approximately 6.5 by the end of the transient. An iodine partition coefficient of 197 is derived with the minimum SG secondary pH value of 6.5, which envelopes the suggested value of 100 in the regulations.