Validation on a water leak calculation module of SWACS by high temperature and pressure water blowdown tests; Report No.2 : Study of water leak rate from a failed heat transfer tube in an LMFBR's SG

Hiroi, Hiroshi*; Miyake, Osamu; *

PNC TN941 82-37, 170 Pages, 1982/02

PNC-TN941-82-37.pdf:3.0MB

Blowdown tests of high temperature and pressure water from a long pipe were carried out to validate the computer code SWAC-11 which is used for the calculation of the water leak rate from a failed heat transfer tube in an LMFBR's SG. The steady leak rate, and transients of pressure and thrust force of the pipe were measured. Especially, the short term transient of thrust force can be obtained by a new measuring method using the spring-mass model. These data were compared with calculation results of SWAC-11. As for steady data, the Moody's model of the critical flow and the effect of the two-phase multiplier were studied. Major conclusions are as follows: (1)The calculation results of SWAC-11 almost agreed with the steady data. But in detail, SWAC-11 inclined to predict 10 15% less than experimental data of water leak rate and thrust force in the case of high pressure saturated water. This discrepancy will be reduced by introducing the Thom's correlation as the two-phase multiplier. (2)The calculation results of SWAC-11 also agreed with the experimental data after 5 msec since the blowdown was initiated. (3)The flow model of SWAC-11 can be applied to the blowdown of the subcooled water. (4)The thrust force (F) immediately after the blowdown is the sum of the wave force and the blowdown force. The relation of F, the initial pressure P, and cross section S can be given by the expression, F/SP=1.36. (5)Compared with calculation results in detail, the profiles of experimental data were found to be more complicated. This tendency was observed markedly in the case of the subcooled water blowdown. (6)Test results of superheated steam blowdown agreed with SWAC-11 predictions as for unsteady data as well as steady data.