United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 88-23, Supplement 1: Potential for Gas Binding of High-Pressure Safety Injection Pumps During a Loss-Of-Coolant Accident

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                      OFFICE OF NUCLEAR REACTOR REGULATION
                             WASHINGTON, D.C.  20555

                                 January 5, 1989


Information Notice No. 88-23, SUPPLEMENT 1:  POTENTIAL FOR GAS BINDING OF 
                                                 HIGH-PRESSURE SAFETY INJECTION 
                                                 PUMPS DURING A LOSS-OF-COOLANT 
                                                 ACCIDENT 

Addressees: 

All holders of operating licenses or construction permits for pressurized
water reactors (PWRs).

Purpose: 

The purpose of this supplement is to alert addressees to additional potential 
problems resulting from transport and accumulation of gases in the piping of 
emergency core cooling systems.  It is expected that recipients will review 
the information for applicability to their facilities and consider actions, 
as appropriate, to avoid similar problems.  However, suggestions contained 
in this information notice do not constitute NRC requirements; therefore, 
no specific action or written response is required. 

Description of Circumstances: 

Both units at the Farley plant have dual purpose centrifugal charging and high 
pressure safety injection (HPSI) pumps and dual purpose residual heat removal 
(RHR) and low pressure safety injection (LPSI) pumps.  After an event on 
February 26, 1988 at Unit 1 of the Farley plant, the licensee concluded that 
dissolved hydrogen from the volume control tank was coming out of solution in 
piping downstream from the tank.  At a point in the system beneath the bottom 
of the volume control tank, some of the gaseous hydrogen came out of solution 
and accumulated at the highpoint in piping connected to the suction header for 
the three centrifugal charging pumps.  That piping connects the discharge side 
of the LPSI pumps to the suction side of the HPSI pumps and is normally valved 
out of service.  During a loss-of-coolant accident (LOCA), when the suction 
side of the LPSI pumps is transferred from the refueling water storage tank 
(RWST) to the containment sump, the piping is valved into service.  If a LOCA 
had occurred before the problem was discovered approximately 50 standard cubic 
feet of hydrogen would have entered the portion of the suction header common 
to HPSI pumps A and B and possibly caused damage to the pumps due to gas binding.
This event was discussed in Information Notice No. 88-23 which was issued on 
May 12, 1988.

Each unit at the South Texas plant has separate HPSI and LPSI pumps in addition 
to centrifugal charging and RHR pumps.  On May 13, 1988, the licensee reported 



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.                                                     IN 88-23, Supplement 1
                                                     January 5, 1989
                                                     Page 2 of 2 


the loss of suction to the centrifugal charging pumps for Unit 2 when suction 
was transferred from the volume control tank to the RWST.  The piping from the 
nozzle at the bottom of the RWST to the suction header for the centrifugal 
charging pumps has two high points.  The highest point is at approximately the 
same elevation as the midplane of the RWST and is approximately 12.5 feet above 
the nozzle.  The suction header for the centrifugal charging pumps is 1.7 feet 
above the nozzle.  The licensee concluded that the presence of low water level 
in the RWST at the time suction was transferred resulted in pressures less than 
atmospheric pressure at the high point and the subsequent release of dissolved 
air.  In Mode 5, the technical specifications permit the water level in the RWST 
to be well below the midplane of the RWST.  With low water level in the RWST, 
the licensee's ability to respond to a boron dilution accident could be impaired 
by the release of dissolved air and the potential air binding of the pumps.  

Each unit at the North Anna and Surry plants has dual purpose centrifugal 
charging and HPSI pumps and dual purpose RHR and LPSI pumps.  At North Anna, 
on October 14, 1988, the licensee found from 0.4 to 70 cubic feet of gas at 
atmospheric pressure in various runs of piping connecting the RWST to the HPSI 
pumps and in piping connecting the LPSI pumps to the HPSI pumps.  The gas found 
in the piping in all cases was air, except in one piping run which contained 14% 
hydrogen.  Similar problems were found at Surry on October 12, 1988.

No specific action or written response is required by this information notice.  
If you have any questions about this matter, please contact the technical 
contact listed below or the Regional Administrator of the appropriate regional 
office. 




                                 Charles E. Rossi, Director 
                                 Division of Operational Events Assessment 
                                 Office of Nuclear Reactor Regulation 


Technical Contact:  Roger Woodruff, NRR 
                    (301) 492-1180 


Attachment:  List of Recently Issued Information Notices 

.                                                       Attachment
                                                       IN 88-23, Supplement 1
                                                       January 5, 1989
                                                       Page 1 of 1

                             LIST OF RECENTLY ISSUED
                            NRC INFORMATION NOTICES 
_____________________________________________________________________________
Information                                  Date of 
Notice No._____Subject_______________________Issuance_______Issued to________

89-01          Valve Body Erosion            1/4/89         All holders of OLs
                                                            or CPs for nuclear
                                                            power reactors.

88-46,         Licensee Report of Defective  12/30/88       All holders of OLs
Supp. 2        Refurbished Circuit Breakers                 or CPs for nuclear
                                                            power reactors.

88-101         Shipment of Contaminated      12/28/88       All holders of OLs
               Equipment between Nuclear                    or CPs for nuclear
               Power Stations                               power reactors.

88-100         Memorandum of Understanding   12/23/88       All major nuclear
               between NRC and OSHA                         materials licensees
               Relating to NRC-licensed                     and utilities holding
               Facilities (53 FR 43950,                     CPs and OLs.
               October 31, 1988)   

88-99          Detection and Monitoring      12/20/88       All holders of OLs
               of Sudden and/or Rapidly                     or CPs for PWRs.
               Increasing Primary-to-
               Secondary Leakage

88-98          Electrical Relay Degradation  12/19/88       All holders of OLs
               Caused by Oxidation of                       or CPs for nuclear
               Contact Surfaces                             power reactors.

88-97          Potentially Substandard       12/16/88       All holders of OLs
               Valve Replacement Parts                      or CPs for nuclear
                                                            power reactors.

88-96          Electrical Shock Fatalities   12/14/88       All holders of OLs
               at Nuclear Power Plants                      or CPs for nuclear
                                                            power reactors.

88-95          Inadequate Procurement        12/8/88        All holders of OLs
               Requirements Imposed by                      or CPs for nuclear
               Licensees on Vendors                         power reactors.

88-94          Potentially Undersized        12/2/88        All holders of OLs
               Valve Actuators                              or CPs for nuclear
                                                            power reactors.
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit 
Page Last Reviewed/Updated Tuesday, November 12, 2013