Design improvements of passive flow controlling safety injection tank

Advanced SITs of the evolutionary PWRs have the advantage that it can passively control the ECC water discharge flow rate. Thus, the LPSI pumps can be eliminated from the safety injection system owing to the benefit of the advanced SITs. In the present study, a passive sealing plate was designed in order to overcome the shortcoming of the advanced SITs, i.e., the early nitrogen discharge through the stand pipe. The operating principle of the sealing plate depends only on the natural phenomena of buoyancy and gravity. The performance of the sealing plate was evaluated using the VAPER test facility, equipped with a full-scale SIT. It was verified that the passive sealing plate effectively prevented the air discharge during the whole duration of the ECC water discharge. Also, the major performance parameters of the advanced SIT were not sensitive to the installation of the sealing plate. (author)