Results of the failure propagation tests in the steam generator safety tests facility (SWAT-3)

not registered; not registered; not registered; Daigo, Yoshimichi

The Failure Propagation Tests have been carried out using the Steam Generator Safety Test Facility (SWAT-3) in PNC O-arai Engineering Center since 1979, in order to select a design basis leak (DBL) for sodium-water reaction accidents in Japanese prototype LMFBR MONJU's steam generators. Here reported are results of third Failure Propagation Tests (SWAT-3 Run-14 and Run-15) conducted in September 1980 and April 1981. Aim of these tests are to grasp how tube failures develop from the occurrence of initial leak to the completion of the water dump. The significant results are as follows: (1) In Run-14 test whose initial leak rate was 18 g/sec, the failure propagations occurred at 94, 145, and 168 sec, and additional two propagations occurred during tho water dump. (2) In Run-15 test, at first no propagation occurred during about four hours injection at the leak rate of 1.2 g/sec, therefore, as it was increased up to 14 g/sec by changing the water conditions, propagations occurred at 50, 195, 224 and 253 sec which was during the dump. (3) The maximum water leak rate is 2.7 kg/sec during the water dumping in Run-15, which suggests that the water leak rate during the water dump can exceed that before dump. (4) Numbers of the failed tubes are four in both tests. The maximum size of penetration is 18 mm 4.1 mm which was generated at the fifth propagation in Run-15 and is fish-mouth type. (5) Mechanism of the propagations is wastage in the small leak region, but in the range of the leak rate above hundred g/sec, there are some cases of high temperature effect added to wastage effect.