ML19312C402
| ML19312C402 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 07/10/1978 |
| From: | Thompson D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Parker W DUKE POWER CO. |
| References | |
| NUDOCS 7912130925 | |
| Download: ML19312C402 (2) | |
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W In Reply Refer To:
R11:JP0 50-369, 50-370 50-269, 50-270 50-287 Duke Power Company Attn:
Mr. William O. Parker, Jr.
Vice President, Steam Production P. O. Box 2178 422 South Church 5 reet Charlotte, Noich Carolina 28242 Gentlemen:
Euclosed Circular 78-13 is forwarded to you for information.
If there are any questions related to your understanding of the suggested actions, please contact this office.
Sincerely, e
bOf k"f v Dudle / Thompson Deputy Director
Enclosure:
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JUL 10 tan
. Duke Power Company cc w/ encl:
J. C. Rogers, Project Manager McGuire Nuclear Station P. O. Box 2178 Charlotte, North Carolina 28242 M. D. McIntosh, Plant Manager McGuire Nuclear Station P. O. Box 48S Cornelius, North Carolina 28031 J. E. S=ith, Station Manager Oconee Nuclear Station P. O. Box 1175 Seneca, South Carolina 29678 I
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 July 10, 1978 IE Circular No. 78-13 OPERABILITY OF SERVICE WATER PUMPS Description of Circumstances:
On January 11, 1978, Salem Generating Station Unit No. 1, a 4-loop Westinghouse PWR with once-through cooling located on the Delaware River, experienced high strainer differential pressu:es and the loss of four of six installed service water pumps within a period of approximately thirty minutes. At the time of this occurrence, the river surface was covered with a layer of frazil (slush) ice to an unknown depth.
Each service water pump discharge is equipped with an R. P. Adams VDWS-68 automatic self-cleaning strainer. The indication of failure was high strainer differential pressure.
Subsequent investigation showed that each of the four strainers had broken shear pins in the backwash shaft which caused the self-cleaning feature to becoce inoperable. The internals of the strainers revealed no unusual debris which could have caused differential pressures h;;h enough to shear the pins.
Each service water pump takes suction near the bottom of individual bays in the intake structure.
Examination of the bays revealed that silt had accumulated to significant heights between the traveling screen and pump suction in each of the bays associated with failed strainers.
The combined effects of high silt " walls," low river water level, and the surface ice, probably caused the pump suction to receive only ice-entrained water. This mixture then caused the strainers to clog and j
shear the backwash shear pins due to the high differential pressures.
l By the time the strainers were opened for inspection, the ice had melted.
The safety significance of this event stems from the potential, under a unique set of environmental circumstances, for a complete loss of I
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IE Circular No. 78-13 July 10, 1978 Corrective actions included the establishment of a periodic surveillance program to ensure that silt levels in the service water bays do not reach a level sufficiently high to cause recurrence of this event.
Holders of operating licenses or construction permits for power reactors who receive this Circular should review the service water design and postulated conditions in the ultimate heat sink to ensure that a similar combination of surface ice, water level, and forebay silting could not precipitate inoperability of the service water system.
If such condi-tions are credible, a program to monitor the conditions at the service water intake structure should be implementai and procedures established for corrective action to be taken under normal and emergency conditions.
No written response to this Circular is required.
If you require additional information regarding this matter, contact the Lirector of the appropriate NRC Regional Office.
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IE Circular No. 78-13 July 10, 1978 LISTING OF IE CIRCULARS ISSUED IN 1978 Circular Subject Date Issued To No.
of Issue 78-01 Loss of Well Logging 4/5/78 All Holders of Source Well Logging Source Licenses 78-02 Proper Lubricating Oil 4/20/78 All Holders of for Terry Turbines Reactor OLs or CFs 78-03 Packaging Greater Than 5/12/76 All Holders of Type A Quantities of Reactor OLs, cps, Low Specific Activity Fuel Cycle, Radioactive Material Priority I Material for Transport and Waste Disposal Licenses 78-04 Installation Error That 5/15/78 All Holders of Could Prevent Closing of Reactor OLs or Fire Doors cps 78-05 Inadvertent Safety Injection 5/23/78 All Holders of During Cooldown Reactor OLs or cps 78-06 Potential Common Mode 5/23/78 All Holders of Flooding of ECCS Equipment Reactor OLs or Rooms at BWR Facilities cps 78-07 Damaged Components of a S/31/78 All Holders of Bergen-Paterson Series Reactor OLs or 25000 Hydraulic Test cps Stand 78-08 Environmental Qualification 5/31/78 All Holders of of Safety Related Equipment Reactor OLs or at Nuclear Power Plants cps 09 Arcing of General Electric 6/5/78 All Holders of Company Size 2 Contactors cps Enclosure Page 1 of 2
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1 IE Circular No. 78-13 July 10, 1978 LISTING OF IE CIRCULARS ISSUED IN 1978 Circular Subject Date of Issued to No.
Issue 78-10 Control of Sealed 6/14/78 All Medical Sources Used in Licensees in Radiation Therapy Categories G and G1 78-11 Recirculation M-G 6/15/78 All Holders of Set Overspeed Stops BWR OLs or cps 78-12 HPCI Turbine Control 6/30/78 All Holders of Value Lift Rod Bending BWR OL's or cps except as listed in Encl. 2 Enclosure Page 2 of 2
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