Rapid hot-water depressurization experiment. Interim report, May 1977

An apparatus has been constructed for the purposes of studying the early response of water to very sudden depressurization from both BWR and PWR conditions. The apparatus incorporates a novel opening device which achieves extraordinarily rapid removal of pressure from the water--up to about 23 million psi/sec, resulting in 80 percent depressurization, in as little as 100 μsec. The present configuration of the container is a straight, 1/2 in. I.D. pipe with a full cross-sectional opening. Later experiments are to involve reduced cross-sectional openings, slower opening rates, and the construction of a 2 in. I.D. pipe to ascertain whether or not dimensional scaling influences the results. The early results of these experiments reveal that the pressure initially undershoots the saturation pressure dramatically. Under PWR conditions it almost reaches the ''spinodal line,'' or locus of limiting liquid superheat states. Following nucleation the pressure rapidly recovers to within about 70 percent of the saturation pressure. From experiments made to date, it appears that the very sudden pressure excursions do not accompany this recovery