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
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