Abstract:

Background: Nitrate salt natural circulation loop (NNCL) system is an important platform for studying molten salt natural circulation characteristic. And the foundation for the design and verification passive residual heat removal system in the fluoride slat-cooled high temperature reactor might be obtained in this platform. Purpose: This study aims to analyze characteristics of NNCL system under different heating power, air flow, etc. Methods: The RELAP5/MOD4.0 code was employed with modification of applicability for NNCL. Simulation was performed for the NNCL system under various running conditions. Results: The calculation results show that air flow has an important effect on NNCL mass flow rate and an inverse relationship with mass flow rate; the steady temperature and mass flow rate of NNCL will increase with the heating power and the steady mass flow rate of NNCL will decrease with the air inlet temperature; NNCL system needs a long time to get a steady state, about 8?27 h. In order to keep the nitrate salt in liquid and not deteriorate, power should be limited in 20?40 kW at the rated air mass flow rate. Conclusion: Heating power and air mass flow rate are the most important factors to effect of the NNCL steady state, which can influence the temperature and the mass flow rate of NNCL system.

Key words: Natural circulation, RELAP5/MOD4.0, Passive residual heat removal system, Nitrate slat