Background: Loss of offsite power(LOOP) is a possible accident to any type of reactor

and this accident can reflect the main idea of reactor safety design. Therefore

it is very important to conduct a study on probabilistic safety assessment(PSA) of the molten salt reactor that is under LOOP circumstance. Purpose: The aim is to calculate the release frequency of molten salt radioactive material to the core caused by LOOP

and find out the biggest contributor to causing the radioactive release frequency. Methods: We carried out the PSA analysis of the LOOP using the PSA process risk spectrum

and assumed that the primary circuit had no valve and equipment reliability data based on the existing mature power plant equipment reliability data. Results: Through the PSA analysis

we got the accident sequences of the release of radioactive material to the core caused by LOOP and its frequency. The results show that the release frequency of molten salt radioactive material to the core caused by LOOP is about 2×10-11/(reactor·year)

which is far below that of the AP1000 LOOP. In addition

through the quantitative analysis

we obtained the point estimation and interval estimation of uncertainty analysis

and found that the biggest contributor to cause the release frequency of radioactive material to the core is the reactor cavity cooling function failure. Conclusion: This study provides effective help for the design and improvement of the following molten salt reactor system.