An experimental study of the hydrodynamic aspect of the expansion process in a hypothetical core disruptive accident (HCDA) by means of a shock-tube technique is described. The working fluid pair was water-air. Interface displacement data for shock strengths in the range 0.5–3.0 were obtained by means of high-speed photography. The displacement data are fitted into least-square polynomials in time, which are used to compute accelerations and entrainment velocities. The accelerations thus obtained, which are in the range 950 m/s2−15,000 m/s2, are uniform in time. The entrainment velocities for experiments performed with the circular driven section are consistently higher than those for the experiments performed with the square driven section at the same accelerations. The difference is attributed to the entrainment velocity for the latter case being time-dependent. Furthermore, an upper bound on the rate of entrainment in an HCDA is proposed.

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