United States Nuclear Regulatory Commission - Protecting People and the Environment

IE Circular No. 78-13 - Inoperability of Multiple Service Water Pumps



CR78013 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                         WASHINGTON, D. C.  20555 

                               July 6, 1978 

MEMORANDUM FOR:     B. H. Grier, Director, Region I 
                    J. P. O'Reilly, Director, Region II 
                    J. G. Keppler, Director, Region III 
                    K. V. Seyfrit, Director, Region IV 
                    R. H. Engelken, Director, Region V 

FROM:               Norman C. Moseley, Director, ROI, IE 

SUBJECT:            IE CIRCULAR 78-13 - INOPERABILITY OF MULTIPLE
					SERVICE WATER PUMPS 

     The subject document is transmitted for issuance on July 10, 1978. The 
Circular should be issued to all holders of Reactor Operating Licenses and 
Construction Permits except for plants located in Alabama, Arkansas, 
California, Florida, Georgia, Louisiana, Mississippi, and South Carolina. 
Also enclosed is a draft copy of the transmittal letter. 


                                   Norman C. Moseley, Director 
                                   Division of Reactor Operations 
                                     Inspection 
                                   Office of Inspection and 
                                     Enforcement 

Enclosures: 
1.  IE Circular 78-13 
2.  Draft Transmittal Letter 

CONTACT:  R. W. Woodruff, IE 
          49-28180 
.

(Transmittal letter for Circular 78-13 except for plants located in 
Arkansas, California, Florida, Georgia, Louisiana, Mississippi, and South 
Carolina) 

Addressee: 

Enclosed 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. 


                                        Signature 
                                        (Regional Director) 

Enclosure:  
IE Circular 78-13 
.

                              UNITED STATES 
                      NUCLEAR REGULATORY COMMISSION 
                   OFFICE OF INSPECTION AND ENFORCEMENT 
                          WASHINGTON, D.C. 20555 

                              July 10, 1978 

                                                         IE Circular 78-13 

INOPERABILITY 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 pressures 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 become inoperable. The internals of the 
strainers revealed no unusual debris which could have caused differential 
pressures high 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 shear the backwash shear pins 
due to the high differential pressures. 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 service 
water. 

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July 10, 1978                                         IE Circular No. 78-13 

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 conditions are credible, 
a program to monitor the conditions at the service water intake structure 
should be implemented 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 Director of the appropriate 
NRC Regional Office. 

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