United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-23: Inadequate Surveillance and Postmaintenance and Postmodification System Testing

                                                      SSINS No.:  6835    
                                                       IN 85-23 

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

                               March 22, 1985 

Information Notice No. 85-23:  INADEQUATE SURVEILLANCE AND 
                                  POSTMAINTENANCE AND POSTMODIFICATION 
                                  SYSTEM TESTING 

Addressees: 

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

Purpose: 

This information notice is to alert addressees of several instances pertain-
ing to improper system modifications, inadequate postmodification system 
testing, and inadequate surveillance testing recently detected at the 
McGuire nuclear power facility. 

It is expected that recipients will review the information contained in this
notice for applicability to their facilities and consider actions, if appro-
priate, to preclude similar problems from occurring at their facilities. 
However, suggestions contained in this notice do not constitute NRC 
requirements; therefore, no specific action or written response is required. 

Description of Circumstances: 

On November 1, 1984, Duke Power Company (DPC) informed the NRC that the four
Rosemont differential pressure transmitters that control the closing of four
isolation valves of the upper-head injection (UHI) system at McGuire Unit 1 
were improperly installed (i.e., the impulse lines were reversed when the 
original Barton reverse-acting differential pressure switches were replaced 
with Rosemont direct-acting differential pressure transmitters during April 
of 1984). As a result, the UHI isolation valves failed to close during 
draining of the accumulator when the water level in the UHI accumulator 
reached the set point. In addition to the improper installation, the 
postmodification testing was limited to a dry calibration method that does 
not use the actual reference leg of the accumulator; therefore, the 
installation error was not detected by the postmodification test. 
Consequently, the plant was operated for approximately five months with the 
UHI isolation valves inoperable. 

The McGuire UHI system design includes a separate nitrogen accumulator that 
supplies pressurized nitrogen to force the water from the UHI accumulator 
into the reactor vessel during the initial phase of a design-basis loss-of-
coolant accident (LOCA). Thus, if a design-basis LOCA had occurred while the
UHI isolation valves were inoperable, the UHI system would have been actu-
ated; however, the UHI isolation valves would not have closed when the water
in the  

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                                                           IN 85-23  
                                                           March 22, 1985 
                                                           Page 2 of 3 

UHI accumulator had been depleted. As a result, nitrogen gas could have been
injected into the reactor vessel during the course of a design-basis LOCA. 
Under such conditions, and using Appendix K assumptions, DPC's analysis 
indicated that the peak cladding temperature of 2200F most likely would 
have been exceeded and that the worst-case increase in containment pressure 
could have resulted in exceeding the design pressure by 2 psi. 

A related but separate event involved the establishing of the set points for
closing the UHI isolation valves. On February 14, 1984, DPC approved the use
of a dry calibration method, which would establish the trip set point for 
closing the UHI isolation valves relative to the bottom of the UHI water 
accumulator tank. However, a 24-inch nonconservative error in the trip set 
point occurred at McGuire Units 1 and 2 when the responsible instrument 
engineer misinterpreted the tank measurements made by instrument 
technicians. Because the dry calibration method does not use the actual 
process leg of the UHI accumulator, this error was left undetected at both 
units for several months. The calibration error was finally detected on 
November 2, 1984, while DPC personnel were taking "as-found" data in 
response to the previous error involving the incorrect installation of the 
differential pressure transmit-ters. The consequences of this event would be 
the early isolation of the UHI water accumulator during a design-basis LOCA, 
resulting in less water being delivered to the vessel than assumed in the 
analysis. 

A completely unrelated event involved the inoperability of two of the four 
overpower delta temperature reactor protection channels at McGuire Unit 2. 
This defect was discovered on November 26, 1984, by a DPC engineer while 
performing a posttrip review of a reactor scram in which signals of the two 
affected channels responded contrary to that expected. This event was caused
because an electrical jumper was not installed on two of the four overpower 
delta temperature input logic cards. The purpose of the jumper is to ensure 
that the overpower delta temperature system provides protection for decreas-
ing temperature, as might be expected on a steam line break. DPC's surveill-
ance tests only verified that protection would be provided for increasing 
temperature, but not for decreasing temperature. This defect was left unde-
tected for an unknown period of time, but most likely it had existed since 
initial plant startup. Subsequent investigations revealed that in addition 
to inadequate testing, there was an absence of instructions and descriptions
of the required jumpers. 

The above examples illustrate the need for thorough reviews and detailed 
attention to plant surveillance and postmaintenance and postmodification 
tests, to ensure that they accomplish the required verification of system 
function. 

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                                                      IN 85-23  
                                                      March 22, 1985  
                                                      Page 3 of 3 

No specific action or written response is required by this information 
notice; however, if you have any questions regarding this notice, please 
contact the Regional Administrator of the appropriate NRC regional office or
the technical contact listed below. 


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

Technical Contacts:  I. Villalva, IE 
                     (301) 492-9007 

                     H. Dance, RII 
                    (404) 221-5533 

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