The wind channel test will research air flow resistance characteristic and effects of air channel shape and air inlet location on natural circulation flow.

The influence of environment wind and surrounding buildings on the natural convection flow had been especially considered. Moreover, the velocity field at the lower turning of air baffle

and the surface wind pressure distribution of containment were needed for design. The main purposes of the test were: a) To verify the feasibility of passive containment cooling system design. Main emphasis was put on the influence of the environmental wind; b) To supply a database for preliminary design and design improvement, especially the experimental data of velocity field in annuli and pressure drop of each section. The velocity field in the low baffle end zone was calculated and tested.

The model tests (1/10 in scale) with different flow deflectors were done to study the way of improvement. Both test and calculated results indicated that there were an enclosed vortex in the stagnant bottom and an obvious separate bubble formed at the rear of the baffle. The flow deflectors could reduce the separate bubble. Another model test was run in 0.2—0.5 m/s water velocity. A larger vortex at the upper stream of flying object protect shielding and a smaller bubble at the down stream of it were proved by both test and calculation.

A pressure distribution test in the surface of containment was done in a low velocity wind tunnel with various wind speeds, air entrances, yaw and pitch angles. The test shows that the pressure is positive in the area of -35° < 0 < 35°. The influence of wind on natural convection of containment was also done with a 1/50 integral model. The test results revealed that natural convection flow rate was enhanced in general by outside wind and horizontal wind (a = 0) had the better effect than a < 0° or a > 0°. The position of chimney might influence the air flowing around the containment. The distance between containment and chimney should be larger than 4 times of chimney diameter. However, smoke wind tunnel test showed no exhausted hot air was re-circulated under any d outside wind conditions.

1.2. Summary

1) The studies of passive ERHR system, CMT injection system and passive containment cooling system prove that the design of all these passive systems are feasible and reliable in principle and can meet basically the required safety functions.

2) Some undesired thermal hydraulic phenomena were found and identified in these studies. For example, the flow vortex in the containment air duct, and “water hammer” of ERHR test may have bad impacts on its safety functions and should be avoided in the next step tests and AC600/1000 design.

3) All data obtained have been already used for design improvement and next R&D program planning.

3. ANALYSIS CODE DEVELOPMENT AND CALCULATION FOR NATURAL CIRCULATION BEHAVIOR OF AC600/1000