Flow Field and Blowdown Test of Secondary Side Lower Part of Steam Generator

The lower blowdown structure located in the tubesheet of steam generator (SG) in nuclear power plant can suck out the sludge on the tubesheet secondary side surface and discharge it. In order to reasonably design this structure and improve the blowdown efficiency, based on the SG prototype structure of passive large-scale advanced pressurized water reactor (CAP1400), a blowdown test piece was designed according to the ratio of 1:4 to simulate the tubesheet, heat transfer tube and other components at the lower part of SG. Computational fluid dynamics (CFD) calculation was carried out for the lower flow field, and the results were compared with those of the blowdown test. The fluid flow characteristics near the tube sheet surface were obtained. This test provides a basis for reducing sludge accumulation and improving the design by studying the fluid flow characteristics and sludge distribution law near SG tube plate, measuring the pressure drop of each part of the test piece and comparing the design of SG single-side and double-side blowdown structures. It is found that the performance of single/double-side blowdown structure is basically the same, and the single-side blowdown structure can effectively discharge the sludge particles in the test piece.