[Federal Register Volume 60, Number 143 (Wednesday, July 26, 1995)]
[Pages 38378-38379]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-18320]



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.


NRC Generic Letter 89-10, Supplement 7: Consideration of Valve 
Mispositioning in Pressurized-Water Reactors


    All holders of operating licenses (except those licenses that have 
been amended to a possession only status) or construction permits for 
nuclear power reactors.


    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.


    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 

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.


    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 
     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 
[FR Doc. 95-18320 Filed 7-25-95; 8:45 am]