United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-96: Temporary Strainers Left Installed in Pump Suction Piping

                                                           SSINS No.:  6835
                                                            IN 85-96 

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                            WASHINGTON, DC 20555

                              December 23, 1985

Information Notice No. 85-96:   TEMPORARY STRAINERS LEFT INSTALLED IN 
                                   PUMP SUCTION PIPING 

Addressees: 

All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP). 

Purpose: 

This information notice is provided to alert recipients about a potentially 
significant problem pertaining to temporary construction strainers left in-
stalled in the suction piping of safety-related pumps. It is suggested that 
recipients review the information for applicability to their facilities and 
consider actions, if appropriate, to preclude a similar problem occurring at
their facilities. However, suggestions contained in this information notice 
do not constitute NRC requirements; therefore, no specific action or written
response is required. 

Description of Circumstances: 

Davis-Besse 1 

On August 2, 1985, at Davis-Besse Unit 1, operated by Toledo Edison Company 
(TEC), personnel discovered temporary strainers left installed in the 
suction piping of two high-pressure injection (HPI) pumps. The strainers 
were installed during plant construction to prevent debris from entering 
pump internals. These temporary construction strainers are normally removed 
before hot functional testing. Other pumps in safety-related systems 
including the decay heat removal, containment spray, and component cooling 
water systems, have subsequently been re-checked by radiograph or actual 
disassembly; however, no strainers were found. 

With the Davis-Besse plant in cold shutdown, the first HPI pump strainer was
found during maintenance to repair a flange leak. The discovery occurred 
when TEC Engineering processed a report indicating strainer damage. 
Evidently the strainer was damaged as maintenance personnel attempted to 
remove what appeared to be a pipe spacer ring. The ring was actually part of 
the strainer. Strainer identification was made difficult because, once 
installed, the visible ring closely resembled the spacer rings used to 
replace strainers in other systems. Strainers normally were removed from the 
ring and then the rings were reinserted as pipe spacers. The stainless steel 
strainers consist of a perforated conical basket that is attached to a 
circular flange plate bolted to pump suction piping. 


8512190037 
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                                                         IN 85-96 
                                                         December 23, 1985 
                                                         Page 2 of 3 

The principal cause for the temporary strainer oversight at Davis-Besse was 
a failure of the system turnover checklist to include construction strainer 
removal after system flushing. 

Summer 

On August 27, 1985, during maintenance on the "B" train of the reactor 
building spray (RBS) pump, personnel at the V.C. Summer nuclear power plant 
found a startup construction strainer installed in the pump suction piping. 
The strainer, installed during the 1982 plant startup, was removed and the 
RBS pump returned to service. Similarly on August 29, 1985, maintenance 
personnel determined that the suction piping for the "A" train RBS pump had 
a construction strainer installed. This strainer also was removed and the 
pump returned to service. A review of quality assurance records confirmed 
that strainers installed for pumps in other safety-related systems were 
removed before plant startup. However, records for the RBS system indicated 
that the strainers had not been removed. 

Although left installed in the RBS system since startup, the construction 
strainers were checked annually for debris accumulation as part of a 
preventive maintenance program. Other checks also were performed to 
determine if structural failure had occurred. Apparently the strainers were 
assumed to be a permanent design feature rather than a temporary one. 
Differences in the notation on system drawings may have contributed to the 
false assumption that the strainers were to be installed permanently. RBS 
system drawings, unlike those of other safety-related systems, noted the 
location of temporary strainers with a symbol which was described in the 
legend. Other system draw-ings had a specific footnote about the location on 
the drawing. 

Discussion: 

There are several mechanisms by which temporary construction strainers could
cause safety systems to be made inoperable. These include physical failure 
of the non-safety related strainer which could cause pump or valve failures,
flow restrictions under extremes of pump flows associated with an accident, 
and accumulated blockage of the construction strainer resulting insufficient
flow. An example of impaired operations specific to strainers in systems 
used during the recirculation mode is temporary strainer clogging by debris 
passed through the intake screen, resulting in loss of pump net positive 
suction head. 

Because construction strainers were not designed as safety related 
components and their modes of failure or contribution to system 
inoperability were not evaluated, such temporary strainers constitute an 
unanalyzed plant condition. 

.

                                                         IN 85-96 
                                                         December 23, 1985 
                                                         Page 3 of 3 

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


                                   Edward L. Jordan, Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  Ronald Young, IE 
                    (301) 492-8985 

Attachment:    List of Recently Issued IE Information Notices 
Page Last Reviewed/Updated Tuesday, November 12, 2013