United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 83-78: Apparent Improper Modification of a Component Affecting Plant Safety

                                                            SSINS No.: 6835 
                                                            IN 83-78       

                                UNITED STATES
                           WASHINGTON, D.C. 20555
                              November 17, 1983

Information Notice No. 83-78:   APPARENT IMPROPER MODIFICATION OF A 
                                   COMPONENT AFFECTING PLANT SAFETY 


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


This information notice is provided as a notification of the apparent 
improper modification of a component affecting plant safety. The events 
described below involve a power operated relief valve (PORV). However, the 
area of concern is not limited to PORVs, but rather, relates to the 
modification of any component that affects plant safety. No specific action 
is required in response to this information notice, but it is expected that 
recipients will review the information presented for applicability to their 

Description of Circumstances: 

On September 19, 1983, the Sacramento Municipal Utility District notified 
the NRC resident inspector that while bringing the Rancho Seco Nuclear 
Generating Station into a condition where the once through steam generator 
tube leaks could be repaired, the pressurizer PORV opened. At the time of 
the opening, the reactor coolant system was at 135F and 29 psig. The 
event was terminated by closing the PORV block valve. After the event, the 
pressure had dropped approximately 10 psig and the PORV was apparently still 

Bench testing of a spare PORV, by the utility, indicated that the valve 
opened at 8 psig and reseated between 30 and 50 psig. However, when this 
spare valve was modified in a manner similar to that of the operating PORV, 
it opened at 30 psig and did not reseat at pressures as high as 575 psig. 

The modification to the operating PORV had been accomplished in May 1979. It
consisted of adding an indicator to the valve's operating lever. This 
indicator was visible in the control room, via closed circuit television, 
and provided an indication of whether the PORV was open or closed. Sometime 
between May 1979 and the start of the 1983 refueling outage, this indicator 
fell off the operating lever. It was reinstalled during the recently 
completed refueling outage. 


                                                          IN 83-78         
                                                          November 17, 1983 
                                                          Page 2 of 2      

Based on this testing, the utility concluded that the cause of the problem 
was the weight of the indicator. Therefore, utility personnel removed the 
indicator and will use a contrasting background to permit visual indication 
of the operating lever, itself, via the television monitor. 

Conversations with the PORV manufacturer indicated that it had not been 
consulted on the modification before the utility performed it. In fact, the 
first time the manufacturer knew about the modification was when it was 
notified of the valve's maloperation of September 19, 1983. 

It also appears that the PORV had not been tested after the modification had
been made. As evidenced by the later bench testing of the spare PORV, had 
post modification testing been performed, it would have quickly pointed out 
the shift in operating characteristics of the modified PORV. 

In summary, this event points out two important facets of component 
modification which are dictated by good practice, but which can easily be 
overlooked in the rush to get the plant back on line--namely: 

1.   Consultation with the component manufacturer before making the 
     modification; and 

2.   Testing of component after making the modification. 

Actions 2.2 and 3.2 of Generic Letter 83-28, "Required Actions Based on 
Generic Implications of Salem ATWS Events," addressed the establishment of 
vendor interface and post-maintenance test programs for components affecting
plant safety. Had a rudimentary vendor interface and/or post-maintenance 
test program been in effect for such components, it is reasonable to assume 
that this PORV maloperation could have been averted. 

No written response to this notice is required. If you have any questions 
regarding this matter, please contact the appropriate NRC Regional Office, 
or this office. 

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

Technical Contact:  R. J. Kiessel, IE

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