Abstract: Background: For solid fuel molten salt reactor, the Station Blackout Anticipated Transient Without Scram (SBO-ATWS) is an accident with very low probability, but the consequences are more serious compared with other design basis accidents. The decay heat may not be removed timely and the core safety will be challenged. Purpose: The aim is to study the core safety features under SBO-ATWS accident. Methods: The transient characteristic of simplified system for solid fuel molten salt reactor under SBO-ATWS accident was calculated by using RELAP5/MOD4.0 code which was modified to suit to solid molten salt reactor. Two scenarios (valid or not) of Passive Residual Heat Removal System (PRHR) were simulated. Results: The calculation results show that the effect of PRHR in early accident is not obvious, but the long-term effect is disctinct. The PRHR will ultimately make the core temperature and coolant temperature to reach a stable state even if it is failure.The fuel element temperature rises very slowly in the circumstance of SBO-ATWS which provides more than 20 day’s grace period for human intervention and taking necessary measures. Conclusion: The results show that the solid fuel molten salt reactor has high safety in response to SBO-ATWS.

Key words: Solid fuel molten salt reactor, Station Blackout Anticipated Transient Without Scram (SBO-ATWS), Passive Residual Heat Removal System (PRHR), RELAP5/MOD4.0