[Federal Register Volume 60, Number 143 (Wednesday, July 26, 1995)] [Notices] [Pages 38378-38379] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 95-18320] ======================================================================= ----------------------------------------------------------------------- NUCLEAR REGULATORY COMMISSION Proposed Generic Communication Generic Letter 89-10, Supplement 7, Valve Mispositioning in Pressurized-Water Reactors AGENCY: Nuclear Regulatory Commission. ACTION: Notice of opportunity for public comment. ----------------------------------------------------------------------- SUMMARY: The Nuclear Regulatory Commission (NRC) is proposing to issue Generic Letter 89-10, Supplement 7 to notify addressees that the NRC is removing the recommendation that MOV mispositioning be considered by pressurized-water reactor licensees in responding to GL 89-10, as was done for boiling-water reactor licensees in Supplement 4. The NRC is seeking comment from interested parties regarding both the technical and regulatory aspects of the proposed generic letter supplement presented under the Supplementary Information heading. This proposed generic letter supplement and supporting documentation were discussed in meeting number 276 of the Committee to Review Generic Requirements (CRGR) on July 11, 1995. The relevant information that was sent to the CRGR to support their review of the proposed generic letter is available in the NRC Public Document Room under accession number 9507170370. The NRC will consider comments received from interested parties in the final evaluation of the proposed generic letter supplement. The NRC's final evaluation will include a review of the technical position and, when appropriate, an analysis of the value/ impact on licensees. Should this generic letter supplement be issued by the NRC, it will become available for public inspection in the NRC Public Document Room. DATES: Comment period expires August 25, 1995. Comments submitted after this date will be considered if it is practical to do so, but assurance of consideration cannot be given except for comments received on or before this date. ADDRESSES: Submit written comments to Chief, Rules Review and Directives Branch, U.S. Nuclear Regulatory Commission, Washington, DC 20555. Written comments may also be delivered to 11545 Rockville Pike, Rockville, Maryland, from 7:30 am to 4:15 pm, Federal workdays. Copies of written comments received may be examined at the NRC Public Document Room, 2120 L Street, NW. (Lower Level), Washington, DC. FOR FURTHER INFORMATION CONTACT: David C. Fischer, (301) 415-2728. SUPPLEMENTARY INFORMATION: NRC Generic Letter 89-10, Supplement 7: Consideration of Valve Mispositioning in Pressurized-Water Reactors Addressees All holders of operating licenses (except those licenses that have been amended to a possession only status) or construction permits for nuclear power reactors. Purpose The U.S. Nuclear Regulatory Commission (NRC) is issuing this generic letter to notify addressees about a revised NRC position regarding consideration of valve mispositioning within the scope of Generic Letter (GL) 89-10 for pressurized-water reactors (PWRs). Although this generic letter forwards a new staff position, no specific action or written response is required. Background In GL 89-10 (June 28, 1989), ``Safety-Related Motor-Operated Valve Testing and Surveillance,'' the staff recommended, among other things, that any motor-operated valve (MOV) in a safety-related system that is not blocked [[Page 38379]] from inadvertent operation from either the control room, the motor control center, or the valve itself be considered capable of being mispositioned (referred to as position-changeable MOVs) and be included in licensee MOV programs. When determining the maximum differential pressure or flow for position-changeable MOVs, the licensees were asked to consider ``the fact that the MOV must be able to recover from mispositioning * * *'' Supplement 1 to GL 89-10 limited the prevention of inadvertent MOV operation within the context of the generic letter to the potential for MOV mispositioning from the control room. The Boiling Water Reactor Owners Group (BWROG) submitted a backfit appeal on the recommendations for position-changeable valves. The staff, with the assistance of Brookhaven National Laboratory (BNL), reviewed and evaluated the issues concerning the mispositioning of valves from the control room and determined that the recommendations in GL 89-10 should be changed for BWRs. The BNL study, which used probabilistic risk assessment (PRA) techniques, and the NRC staff evaluation and conclusions were transmitted in a letter from the NRC to the BWROG dated February 12, 1992. The conclusions were communicated to industry and the public at large via Supplement 4 to GL 89-10, also dated February 12, 1992. Supplement 4 indicated that the NRC would perform a similar review for PWRs and stated that GL 89-10 might be revised, if warranted, to clarify the NRC position regarding consideration of MOV mispositioning within the scope of GL 89-10 for PWRs. Description of Circumstances By letter dated July 21, 1992, the Westinghouse Owners Group (WOG) asked the NRC staff to notify PWR licensees that the provisions of GL 89-10 for valve mispositioning are not applicable to PWRs, based on arguments similar to those made by the BWROG. Discussion Under contract to the NRC staff, BNL performed a study similar to the one performed for BWRs of the safety significance of inadvertent operation of MOVs in safety-related piping systems of three PWRs. Consistent with Supplement 1 to GL 89-10, the scope of the study was limited to MOVs in safety-related systems that could be mispositioned from the control room. However, because the available PRA models do not include active mispositioning of MOVs or the physical phenomena that could inhibit repositioning, BNL's study of available plant models was limited in its ability to address this issue. Given this limited scope, BNL concluded that the risk insights from the mispositioning of unlocked MOVs were similar for both PWRs and BWRs. Although PWRs tend to have a higher core damage frequency (CDF) than BWRs, which would suggest that the net increase in CDF from mispositioning of MOVs would be higher for PWRs than for BWRs, PWRs typically have a lower conditional containment failure probability, which would tend to balance the overall risk to the public. The NRC is removing the recommendation that MOV mispositioning be considered by PWR licensees in responding to GL 89-10, as was done for BWR licensees in Supplement 4, in light of the following:Corrective actions have been taken by licensees subsequent to the Davis-Besse event (i.e., detailed control room design reviews, independent valve position verification programs, and operator training improvements). Corrective actions are being applied to many of the most important valves under the other provisions of GL 89-10. Other operational events are absent (other than Davis- Besse) in which mispositioning MOVs from the control room actually set up conditions that prevented repositioning. The results of the BNL study for PWRs. Implementation of this relaxation by licensees is voluntary. Staff Position The staff no longer considers the recommendations for inadvertent operation of MOVs from the control room to be within the scope of GL 89-10 for PWRs. However, the staff believes that consideration of valve mispositioning benefits safety. Modifying the provisions in GL 89-10 for valve mispositioning does not affect the GL 89-10 recommendations for licensees to review safety analyses, emergency procedures, and other plant documentation to determine the design-basis 1 fluid conditions under which all MOVs in safety-related piping systems may be called upon to function. This position also does not supersede the NRC generic recommendations or regulations on valve mispositioning that pertain to such other issues as interfacing-systems loss-of-coolant accidents (ISLOCAs) or fire protection (10 CFR Part 50, Appendix R). \1\ Design-basis conditions are those conditions during both normal operation and abnormal events that are within the design basis of the plant. --------------------------------------------------------------------------- Backfit Discussion This letter represents a relaxation of recommendations set forth in GL 89-10 and prior supplements. Implementation of this relaxation is voluntary and this generic letter supplement requests neither actions nor information from licensees. Therefore, this generic letter supplement is not considered a backfit and the staff has not performed a backfit analysis. Dated at Rockville, Maryland, this 19th day of July 1995. For the Nuclear Regulatory Commission. Brian K. Grimes, Director, Division of Project Support, Office of Nuclear Reactor Regulation. [FR Doc. 95-18320 Filed 7-25-95; 8:45 am] BILLING CODE 7590-01-P