Natural Circulation Capability Research Articles

A Comparison of the RELAP5/MOD3 Code with the IIST Natural Circulation Experiments

A series of experiments dealing with variable secondary-side cooling conditions have been conducted at the IIST facility, including the natural circulation experiments under the secondary-side conditions of normal feedwater, loss of feedwater, and full of air. Different cooling conditions at the secondary side directly affect the primary-to-secondary heat transfer and then may influence the heat removal capability of natural circulation in the primary system. The corresponding analytical work is performed using the RELAP5/MOD3 code. Good agreement is reached both qualitatively and quantitatively between the experimental data and calculated results, demonstrating the satisfactory assessment of RELAP5/MOD3 code compared with the IIST natural circulation experiments. The cooling conditions at the secondary side have no significant effect on the heat removal capability of natural circulation as long as sufficient coolant exists on the steam generator secondary side, based on current IIST data and analytical results. Continuous increase of the core temperature and system pressure is also demonstrated experimentally and analytically in the test with the secondary side dry for the sake of deficient heat transfer capability at the steam generator secondary system.

Shield water system design options to improve the safety of fusion reactor blankets

This paper examines the potential of the shield and the shield cooling system of a fusion reactor to be an effective heat sink inside the reactor vacuum vessel, thereby improving the performance of the fusion reactor blanket during an undercooling accident such as a loss of cooling accident (LOCA) or loss of flow accident (LOFA). The paper demonstrates that having a shield cooling system capable of natural circulation during such an accident can make the difference between a blanket surviving the accident or not. The paper also demonstrates that it is inexpensive to add natural circulation capability to a shield cooling system.

高速実験炉「常陽」における自然循環試験

In experimental fast reactor "JOYO", natural circulation test with a trip of all main pumps in the 75MW full power operation was conducted on December 23, 1981. Transition of the main loop flow from forced flow to natural circulation was smooth, and high natural circulation capability was verified. The peak fuel subassembly outlet sodium temperature during this test was below that during 75MW normal operation. Previous to the test, natural circulation analysis code MIMIRN2 was developed. The predicted peak value of the fuel subassembly outlet sodium temperature was in a good agreement with the measured value.