抄録
It is well known that during Loss of Coolant Accident (LOCA) in the contain-ment with pressure suppression system, when mainly steam flows into the wetwell pool water, noticeable pressure oscillation occurs in the system. This paper proposes an analytical model of the pressure oscillation phenomena induced by steam condensation at the outlet of a vent pipe. In this model the pressure oscillation is caused by complex motion of the phase boundary formed at the outlet of a vent pipe. That is, move of the phase boundary causes the condensing area and the temperature to change, leading to the oscillatory change of steam condensing rate and to the pressure oscillation caused by transient steam flow in a vent pipe. The calculation is made for the representative experimental conditions in Marviken with the actual BWR containment. Analytical results fairly well explain the experimental data (MX-II) concerning both the amplitudes and the frequencies of pressure oscillation. The code for calculation of analytical model is named VIBCON.
