United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 96-15: Unexpected Plant Performance During Performance of New Surveillance Tests

                                 UNITED STATES
                         NUCLEAR REGULATORY COMMISSION
                     OFFICE OF NUCLEAR REACTOR REGULATION
                         WASHINGTON, D.C.  20555-0001

                                 March 8, 1996


NRC INFORMATION NOTICE 96-15:  UNEXPECTED PLANT PERFORMANCE DURING PERFORMANCE
                               OF NEW SURVEILLANCE TESTS 


Addressees

All holders of operating licenses or construction permits for nuclear power
reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to the potential for unexpected plant performance
during new surveillance tests performed in accordance with implementation of
improved Standardized Technical Specifications.  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 are not NRC requirements;
therefore, no specific action or written response is required.

Description of Circumstances

In November 1995, Unit 2 of the Edwin I. Hatch Nuclear Plant was in its
twelfth refueling outage in the cold shutdown mode; the "A" loop of the
residual heat removal system was in the shutdown cooling mode.  In accordance
with the recent licensee implementation of improved Standardized Technical
Specifications, component operation from the remote shutdown panel was being
tested for the first time.  When maintenance and operations personnel
performed activities to determine the cause of deficiencies identified during
the testing, approximately 12,000 gallons of water drained out of the reactor
vessel in less than 1 minute.  The low level of water in the reactor vessel
triggered automatic isolation of the shutdown cooling system, terminating the
event.  Further investigation revealed that an interlock designed to prevent a
draindown had been set improperly, actually causing the event.  Although the
event was compounded by personnel, procedural, and maintenance errors, NRC
inspectors attributed the root cause to inadequate modification, maintenance,
and testing control with respect to the remote shutdown panel and related
equipment.  

Over several years, various modifications were made to components which
operate from both the main control room and the remote shutdown panel.  Post-
modification testing of the components had not included operation from the
remote shutdown panel, nor were any periodic surveillance tests performed on
the remote shutdown panel.  The new surveillance test, when completed,
revealed that five valves, two valve position indications, one pump 
indication, and one annunciator were inoperable when control was transferred 


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                                                            March 8, 1996
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to the remote shutdown panel.  Prior to the performance of the valve
operations from the remote shutdown panel, the facility did not adequately 
ensure that the new surveillance tests included sufficient operational and
procedural controls to minimize the potential for a draindown path.     

Discussion

The recent implementation of improved Standardized Technical Specifications
may result in surveillance tests using circuitry that previously went
unchallenged.  Over time, these circuits may have degraded or been modified
and cause unexpected performance.  The normal plant configuration may not be
the most desirable configuration for these new tests.  For example, the normal
control switch lineup on the remote shutdown panel may be an appropriate
lineup for mitigating a control room fire, but may be less appropriate for
testing individual components.  The licensee operational experience described
in this information notice highlights the importance of plant configuration
control when implementing new surveillance tests. 

This information notice requires no specific action or written response.  If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.


                                    signed by

                               Dennis M. Crutchfield, Director
                               Division of Reactor Program Management 
                               Office of Nuclear Reactor Regulation

References

1.  Licensee Event Report 50-366/95-008, "Reactor Vessel Inventory Loss        
    Results in Unplanned Engineered Safety Feature System Actuation,"          
    (Accession No. 9512050133).
2.  NRC Inspection Report 50-366/95-26 (Accession No. 9512270044).
3.  NRC Inspection Report 50-366/95-23 (Accession No. 9512190043).

Technical contacts:  Paul M. Steiner, RII       
                     (404) 331-4187             
                     Internet: pms1@nrc.gov     

                     Neal K. Hunemuller, NRR
                     (301) 415-1152
                     Internet:nkg@nrc.gov
Page Last Reviewed/Updated Thursday, November 21, 2013