Nuclear Engineering and Design 236 (2006) 2405–2410 Design and test of hydraulic vacuum breaker check valve for simplified boiling water reactor H.J. Yoon ∗ , S.T. Revankar, Y. Xu, M. Ishii School of Nuclear Engineering, Purdue University, West Lafayette, IN 47906, United States Received 26 May 2005; received in revised form 6 February 2006; accepted 8 February 2006 Abstract In the current design of the simplified boiling water reactor, the vacuum breaker check valve is an important safety component. The vacuum breaker check valve is the only key safety components which is not passive in nature. Failure of this mechanical valve drastically reduces the passive containment cooling system cooling capability and hence containment pressure may exceed the design pressure. To eliminate this problem novel vacuum breaker check valve was developed to replace the mechanical valve. This new design is based on a passive hydraulic head, which is fail-safe and is truly passive in operation. Moreover this new design needs only one additional tank and one set of piping each to the wetwell and drywell. This system is simple in design and hence is easy to maintain and to qualify for operation. The passive vacuum breaker check valve performance was first evaluated using RELAP5. Then the passive vacuum breaker check valve was constructed and implemented in the PUMA integral test facility. Its performance was studied in a large break loss of coolant accident simulation test performed in PUMA facility. © 2006 Elsevier B.V. All rights reserved. 1. Introduction The passive containment cooling system (PCCS) is an engi- neered safety system effective in the long term cooling of a sim- plified boiling water reactor (SBWR) containment (GE, 1992). The PCCS condensers condense the steam in the drywell (DW). The condensate is then drained to the reactor pressure vessel (RPV) through the gravity driven cooling system (GDCS) tank. Non-condensable gases accumulated in the PCCS condensers are vented to the wetwell (WW) gas space. The driving head for the steam is provided by the pressure difference between the DW and the WW. The gas space above the WW serves as the gas reservoir for the nitrogen and other non-condensable gases. During blowdown, most of the non-condensable gases from the DW are passed through eight DW-to-WW vertical vent pipes to the WW gas space. If the DW steam is condensed, the WW pressure can be higher than the DW pressure. If the WW gas pressure is higher than the upper DW space pressure then the PCCS cannot vent the non-condensable gas. This will drastically ∗ Corresponding author. Tel.: +1 765 496 3902; fax: +1 765 494 9570. E-mail address: hyoon@purdue.edu (H.J. Yoon). reduce the effectiveness of the PCCS in long term containment cooling. To prevent the over pressurization of the WW relative to the DW, there is a vacuum breaker system between the WW and the DW. The vacuum breaker consists of three sets of check valves, which open when the WW pressure exceeds the DW pres- sure at a preset pressure difference. The vacuum breaker check valve, being a mechanical valve, is prone to failure. The vacuum breaker check valves are the only key safety components which are not passive in nature. If the vacuum breaker valve fail to close, the non-condensable from WW gas space can enter DW. This in turn can drastically reduce PCCS cooling capability. If the vacuum breaker check valve fail to open, then the PCCS venting may be opposed due to high WW pressure compared to DW pressure. This leads to non-condensable accumulation in PCCS condenser tubes and drastically degrades PCCS perfor- mance. To eliminate this problem a new design of the vacuum breaker check valve was developed to replace the mechanical valve. This new design is based on a static hydraulic head which is fail-safe. The operation of this new design of vacuum breaker check valve is truly passive. Moreover this new design needs only one additional tank and one set of piping each to the WW and DW. This system is simple in design and hence is easy to maintain and to qualify for operation. 0029-5493/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nucengdes.2006.02.013