United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 89-77: Debris in Containment Emergency Sumps and Incorrect Screen Configurations

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

                              November 21, 1989


Information Notice No. 89-77: DEBRIS IN CONTAINMENT EMERGENCY SUMPS 
                                  AND INCORRECT SCREEN CONFIGURATIONS

Addressees:

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

Purpose:

This information notice is intended to alert addressees to potential 
problems resulting from inadequate housekeeping and insufficient 
surveillance of containment emergency recirculation sumps.  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:

During the recovery period after a loss-of-coolant accident, following 
injection of emergency coolant from the refueling water storage tank, water 
is collected within the containment emergency recirculation sump to be 
pumped back into the reactor coolant system.  The emergency sump structures 
are designed to provide for a continuous flow of water to the recirculation 
pumps by preventing the entry of air or debris, thereby protecting the 
recirculation pumps from damage due to loss of net positive suction head or 
entrained solid material.  To provide guidance for sump designs, the NRC 
staff issued Regulatory Guide 1.82, "Water Sources for Long-Term 
Recirculation Cooling Following a Loss-of-Coolant Accident," dated June 
1974, which was revised in November 1985.  Regulatory Guide 1.82 emphasizes 
the need for inservice inspection of emergency core cooling sump components, 
including debris interceptors, vortex suppressors, and sump outlets.  The 
staff also expressed the need for emergency sumps to be protected from 
debris in Standard Review Plan 6.2.2 and Generic Letter 85-22, "Potential 
for Loss of Post-LOCA Recirculation Capability Due to Insulation Debris 
Blockage."  PWR standard technical specifications and the technical 
specifications of many plants require visual inspection of the containment 
emergency sump and verification that the suction inlets to the recirculation 
pumps are not restricted by debris.  Sump components, including trash racks 
and screens, must also be inspected.  The surveillance interval is typically 
18 months.

On June 16, 1988, following a recirculation flow verification test, loose 
parts and debris were found in the containment sump, the recirculation 
pumps, and the suction piping of Surry Units 1 and 2.  Some of the items 
were large enough to 


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have caused pump damage or flow degradation.  In addition, some of the sump 
screens were found to have gaps,  which could have allowed additional loose 
material to enter the sump.  One screen was found to be missing.  Following 
investigation of the event by the licensee and the NRC staff, the licensee 
incorporated sump surveillance requirements similar to those of PWR standard 
technical specifications into their plant procedures.  The NRC issued a 
notice of violation and proposed imposition of a $50,000 civil penalty.

On July 8, 1989, the licensee for the Trojan facility discovered numerous 
items in the containment sump.  The NRC was informed of this condition on 
July 12, 1989.  On July 14, 1989, after containment had been closed out, an 
NRC inspector and the licensee found additional debris.  On July 17, 1989, 
the top sump screen and portions of the inner screen were found to be 
missing.  On July 19, 1989, the NRC identified additional missing and 
damaged inner sump screens.  Debris had previously been found in the Trojan 
sump during a 1988 outage.  In 1980, a residual heat removal pump was jammed 
by a welding rod between the impeller and the casing ring demonstrating the 
potential safety significance of loose debris in the containment emergency 
sump.  The Trojan Technical Specifications contain periodic inspection 
requirements for the containment emergency sump and sump screens.  The 
licensee's inspection procedures for the containment emergency sump did not 
have adequate inspection criteria.  The NRC issued a notice of violation and 
proposed imposition of a $280,000 fine for a severity level II violation. 

As a result of the problems identified at the Trojan facility, the NRC 
resident inspector recently performed an inspection of the Diablo Canyon 
sump and sump screens, including a comparison of the design drawing to the 
actual arrangement of the sump screens.  Debris was found in the Unit 1 and 
Unit 2 sumps, and the sump screen arrangement on the design drawing was 
found to be incorrect.  The sump screens were not configured in accordance 
with the FSAR drawing. The Diablo Canyon Technical Specifications contain 
periodic inspection requirements for the containment emergency sump and sump 
screens.  Initial findings indicate that plant procedures for sump 
inspection were not sufficient or detailed enough to assure adequate 
inspections.

This information notice requires no specific action or written response.  If 
you have any questions about the information in this notice, please contact 
the technical contact listed below or the appropriate NRR project manager.




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

Technical Contact:  Walton Jensen, NRR
                    (301) 492-1190

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