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Information Notice No. 83-78: Apparent Improper Modification of a Component Affecting Plant Safety
SSINS No.: 6835 IN 83-78 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 November 17, 1983 Information Notice No. 83-78: APPARENT IMPROPER MODIFICATION OF A COMPONENT AFFECTING PLANT SAFETY Addressees: All nuclear power reactor facilities holding an operating license (OL) or construction permit (CP). Purpose: 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 facilities. 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 135
F 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 open. 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. 8311010018 . 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 49-28119 Attachment: List of Recently Issued IE Information Notices .
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