[Federal Register Volume 61, Number 34 (Tuesday, February 20, 1996)]
[Notices]
[Pages 6392-6397]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-3691]



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NUCLEAR REGULATORY COMMISSION

Proposed Generic Letter: Periodic Verification of Design-Basis 
Capability of Safety-Related Motor-Operated Valves (M93706); 
Opportunity for Public Comment

AGENCY: Nuclear Regulatory Commission.

ACTION: Notice of opportunity for public comment.

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SUMMARY: The Nuclear Regulatory Commission (NRC) is proposing to issue 
a generic letter to (1) more explicitly address the need for the 
periodic verification of the capability of safety-related motor-
operated valves (MOVs) to perform their safety functions consistent 
with the current licensing bases of nuclear power plants, (2) request 
that each licensee establish a program, or ensure the effectiveness of 
a current program, at each facility within its purview, to verify on a 
periodic basis that safety-related MOVs continue to be capable of 
performing their safety functions within the current licensing bases of 
the facility, and (3) require that licensees provide written responses 
to the generic letter relating to implementation of the requested 
actions.
    NRC regulations require that components important to the safe 
operation of a nuclear power plant, including MOVs, be treated in a 
manner that provides assurance of their performance. Appendix A, 
``General Design Criteria for Nuclear Power Plants,'' and Appendix B, 
``Quality Assurance Criteria for Nuclear Power Plants and Fuel 
Reprocessing Plants,'' to Part 50 of Title 10 of the Code of Federal 
Regulations (10 CFR Part 50) include broad-based requirements in this 
regard. In 10 CFR 50.55a(f), the NRC requires licensees to comply with 
Section XI of the American Society of Mechanical Engineers Boiler and 
Pressure Vessel Code (ASME Code).
    Nuclear power plant operating experience, valve performance 
problems and MOV research have revealed that the focus of the ASME Code 
on stroke time and leak-rate testing for MOVs was not sufficient in 
light of the design of the valves and the conditions under which they 
must function. For this reason, on June 28, 1989, the NRC staff issued 
Generic Letter (GL) 89-10, ``Safety-Related Motor-Operated Valve 
Testing and Surveillance.'' In GL 89-10, the staff requested that 
licensees and permit holders ensure the capability of MOVs in safety-
related systems to perform their intended functions by reviewing MOV 
design bases, verifying MOV switch settings initially and periodically, 
testing MOVs under 

[[Page 6393]]
design-basis conditions where practicable, improving evaluations of MOV 
failures and necessary corrective action, and trending MOV problems. 
The staff requested that licensees complete the GL 89-10 program within 
approximately three refueling outages or 5 years from the issuance of 
the generic letter. Permit holders were requested to complete the GL 
89-10 program before plant startup or in accordance with the above 
schedule, whichever was later.
    Recommendation ``d'' of GL 89-10 requested that licensees and 
permit holders prepare procedures to ensure that correct MOV switch 
settings are maintained throughout the life of the plant. GL 89-10 
stated that it may become necessary to adjust MOV switch settings 
because of wear or aging and that additional measures beyond ASME Code 
stroke-time testing should be taken to adequately verify that the 
switch settings ensure MOV operability.
    Recommendation ``j'' of GL 89-10 stated that licensees should 
periodically verify MOV capability every 5 years or every 3 refueling 
outages. Recommendation ``h'' of GL 89-10 requested that licensees 
evaluate trends in MOV performance every 2 years or at each refueling 
outage.
    The staff has issued seven supplements to GL 89-10 that provided 
additional guidance and information on GL 89-10 program scope, design-
basis reviews, switch settings, testing, periodic verification, 
trending, and schedule extensions. Supplement 6 to GL 89-10 stated that 
no licensee had adequately justified the use of static test data as the 
sole basis for periodically ensuring MOV design-basis capability.
    GL 89-10 and its supplements provide only limited guidance 
regarding periodic verification and the measures appropriate to assure 
preservation of design-basis capability. This generic letter provides 
more complete guidance regarding periodic verification of safety-
related MOVs. Although this guidance could have been provided in a 
supplement to GL 89-10, the staff considered preparation of this new 
generic letter appropriate to allow closure of the staff review of GL 
89-10 programs as promptly as possible.
    The proposed generic letter was discussed in meeting number 280 of 
the Committee to Review Generic Requirements (CRGR) on January 31, 
1996. The relevant information that was sent to the CRGR will be placed 
in the Public Document Room. The NRC will consider comments received 
from interested parties in the final evaluation of the proposed generic 
letter. The final evaluation by the NRC will include a review of the 
technical position and, as appropriate, an analysis of the value/impact 
on licensees. Should this generic letter be issued by the NRC, it will 
become available for public inspection in the NRC Public Document Room.

DATES: Comment period expires April 22, 1996. Comments submitted after 
this date will be considered if it is practical to do so; assurance of 
consideration can only be given for those 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 
20555-0001. 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: Thomas G. Scarbrough, (301) 415-2794, 
e-mail: [email protected]

SUPPLEMENTARY INFORMATION:

NRC Generic Letter 96-XX: Periodic Verification of Design-Basis 
Capability of Safety-Related Motor-Operated Valves (M93706)

Addressees

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

Purpose

    The U.S. Nuclear Regulatory Commission (NRC) is issuing this 
generic letter to (1) discuss the periodic verification of the 
capability of safety-related motor-operated valves (MOVs) to perform 
their safety functions consistent with the current licensing bases of 
nuclear power plants, (2) request that addressees implement actions 
described herein, and (3) require that addressees provide to the NRC a 
written response to this generic letter relating to implementation of 
the requested actions.

Background

    NRC regulations require that components that are important to the 
safe operation of a nuclear power plant, including MOVs, be treated in 
a manner that provides assurance of their performance. Appendix A, 
``General Design Criteria for Nuclear Power Plants,'' and Appendix B, 
``Quality Assurance Criteria for Nuclear Power Plants and Fuel 
Reprocessing Plants,'' to Part 50 of Title 10 of the Code of Federal 
Regulations (10 CFR Part 50) include broad-based requirements in this 
regard. In 10 CFR 50.55a(f), the NRC requires licensees to comply with 
Section XI of the American Society of Mechanical Engineers Boiler and 
Pressure Vessel Code (ASME Code).
    Nuclear power plant operating experience, valve performance 
problems and MOV research have revealed that the focus of the ASME Code 
on stroke time and leak-rate testing for MOVs was not sufficient in 
light of the design of the valves and the conditions under which they 
must function. For this reason, on June 28, 1989, the NRC staff issued 
Generic Letter (GL) 89-10, ``Safety-Related Motor-Operated Valve 
Testing and Surveillance.'' In GL 89-10, the staff requested that 
licensees and permit holders ensure the capability of MOVs in safety-
related systems to perform their intended functions by reviewing MOV 
design bases, verifying MOV switch settings initially and periodically, 
testing MOVs under design-basis conditions where practicable, improving 
evaluations of MOV failures and necessary corrective action, and 
trending MOV problems. The staff requested that licensees complete the 
GL 89-10 program within approximately three refueling outages or 5 
years from the issuance of the generic letter. Permit holders were 
requested to complete the GL 89-10 program before plant startup or in 
accordance with the above schedule, whichever was later.
    Recommendation ``d'' of GL 89-10 requested that licensees and 
permit holders prepare procedures to ensure that correct MOV switch 
settings are maintained throughout the life of the plant. GL 89-10 
stated that it may become necessary to adjust MOV switch settings 
because of wear or aging and that additional measures beyond ASME Code 
stroke-time testing should be taken to adequately verify that the 
switch settings ensure MOV operability. Recommendation ``j'' of GL 89-
10 stated that licensees should periodically verify MOV capability 
every 5 years or every 3 refueling outages. Recommendation ``h'' of GL 
89-10 requested that licensees evaluate trends in MOV performance every 
2 years or at each refueling outage.
    The staff has issued seven supplements to GL 89-10 that provided 
additional guidance and information on GL 89-10 program scope, design-
basis reviews, switch settings, testing, periodic verification, 
trending, and schedule extensions. Supplement 6 to GL 89-10 stated that 
no licensee had adequately justified the use of static test data as the 
sole basis for periodically ensuring MOV design-basis capability. 

[[Page 6394]]

    GL 89-10 and its supplements provide only limited guidance 
regarding periodic verification and the measures appropriate to assure 
preservation of design-basis capability. This generic letter provides 
more complete guidance regarding periodic verification of safety-
related MOVs. Although this guidance could have been provided in a 
supplement to GL 89-10, the staff considered preparation of this new 
generic letter appropriate to allow closure of the staff review of GL 
89-10 programs as promptly as possible.

Discussion

    Nuclear power plant utilities are nearing completion of the 
verification of the design-basis capability of their GL 89-10 MOVs. The 
NRC staff has been closing its review of individual GL 89-10 programs 
on the basis of the completion of the design-basis verification of 
safety-related MOVs at each nuclear power plant and the utility's 
establishment of a program for periodic verification of MOV design-
basis capability and for the trending of MOV problems. The staff may 
conduct a more complete review of licensee programs for MOV periodic 
verification as part of the implementation of this generic letter.
    The staff believes that various approaches can be taken by 
licensees to establish a periodic verification program that provides 
confidence in the long-term capability of MOVs to perform their design-
basis safety functions. With each approach, the licensee should address 
potential degradation that can result in (1) the increase in thrust or 
torque requirements to operate the valves and (2) the decrease in the 
output capability of the motor actuator.
    The staff has long recognized the limitations of using stroke-time 
testing as a means of monitoring the operational readiness of MOVs (see 
GL 89-04, Supplement 1, ``Guidance on Developing Acceptable Inservice 
Testing Programs'') and has supported industry efforts to improve MOV 
periodic monitoring under the inservice testing (IST) program and GL 
89-10. As such, the staff would consider a periodic verification 
program that provides an acceptable level of quality and safety as an 
alternative to the current IST requirements for stroke-time testing and 
could authorize such an alternative, upon application by a licensee, 
pursuant to the provisions of 10 CFR 50.55a(a)(3)(i). Guidance in this 
generic letter and GL 89-04 (Supplement 1) could be used by a licensee 
in determining whether its periodic verification program provides an 
acceptable level of quality and safety.
    In Attachment 1 to this generic letter, the staff discusses 
industry and regulatory activities and programs related to maintaining 
long term capability of safety-related MOVs and provides the staff 
position regarding American Society of Mechanical Engineers (ASME) Code 
Case OMN-1. The staff also identifies attributes of periodic 
verification programs that the staff considers to be effective and an 
example approach in implementing those attributes. Additionally, as 
discussed in Attachment 1, certain licensees developed MOV periodic 
verification programs that the staff found acceptable during the 
closure of its review of GL 89-10 programs.
    Licensees may consolidate long-term MOV periodic verification and 
trending activities as part of their programs to meet the Maintenance 
Rule (10 CFR 50.65) and other applicable regulations.

Requested Actions

    Each addressee of this generic letter is requested to establish a 
program, or to ensure the effectiveness of its current program, to 
verify on a periodic basis that safety-related MOVs continue to be 
capable of performing their safety functions within the current 
licensing bases of the facility. The program should ensure that changes 
in performance requirements resulting from degradation (such as those 
caused by age) can be properly identified and accounted for. Addressees 
that have developed periodic verification programs in response to GL 
89-10 should review those programs to determine whether any changes are 
appropriate in light of the information in this generic letter.

Required Response

    All addressees are required to submit the following written 
responses to this generic letter:
    1. Within 60 days from the date of this generic letter, a written 
response indicating whether or not the addressee will implement the 
action(s) requested herein. If the addressee intends to implement the 
requested action(s), the addressee shall submit a schedule for 
completing implementation. If an addressee chooses not to implement the 
requested action(s), the addressee shall submit a description of any 
proposed alternative course of action, the schedule for completing the 
alternative course of action (if applicable), and the safety basis for 
determining the acceptability of the planned alternative course of 
action.
    2. Within 180 days from the date of this generic letter, or upon 
notification to NRC of completion of GL 89-10 (whichever is later), the 
addressee shall submit a written summary description of its MOV 
periodic verification program established in accordance with the 
Requested Actions paragraph or the alternative course of action 
established by the addressee in response to item 1 above.
    All addressees shall submit the required written reports to the 
U.S. Nuclear Regulatory Commission, Attn: Document Control Desk, 
Washington, D.C. 20555-0001, under oath or affirmation under the 
provisions of Section 182a, Atomic Energy Act of 1954, as amended, and 
10 CFR 50.54(f). In addition, a copy of the report shall be submitted 
to the appropriate Regional Administrator.

Backfit Discussion

    10 CFR Part 50 (Appendix A, Criteria 1 and 4) and plant licensing 
safety analyses require and/or commit that the addressees design and 
test safety-related components and systems to provide adequate 
assurance that those systems can perform their safety functions. Other 
individual criteria in Appendix A to 10 CFR Part 50, or commitments 
made by licensees in their Final Safety Analysis Reports, apply to 
specific systems. In accordance with those regulations and licensing 
commitments, and under the additional provisions of Criterion XVI of 
Appendix B to 10 CFR Part 50, licensees are expected to take actions to 
ensure that safety-related MOVs are capable of performing their 
required safety functions.
    Recommendation ``d'' of GL 89-10 requested that licensees and 
permit holders prepare procedures to ensure that correct MOV switch 
settings are maintained throughout the life of the plant. GL 89-10 
stated that it may become necessary to adjust MOV switch settings 
because of wear or aging and that additional measures beyond ASME Code 
stroke-time testing should be taken to adequately verify that the 
switch settings ensure MOV operability. The NRC staff issued GL 89-10 
as a compliance backfit as defined in 10 CFR 50.109. The actions 
requested in this generic letter are considered compliance backfits, 
under the provisions of 10 CFR 50.109 and existing NRC procedures, to 
ensure that safety-related MOVs are capable of performing their 
intended safety functions. In accordance with the provisions of 10 CFR 
50.109 regarding compliance backfits, a full backfit analysis was not 
performed for this proposed action; but the staff performed a 
documented evaluation, which stated the objectives of and reasons for 
the requested actions and the basis for invoking the compliance 
exception. A 

[[Page 6395]]
copy of this evaluation will be made available in the NRC Public 
Document Room.

Federal Register Notification

    This generic letter is being issued for a 60-day public comment 
period.

Paperwork Reduction Act Statement

    The information collections contained in this request are covered 
by the Office of Management and Budget clearance number 3150-0011, 
which expires July 31, 1997. The public reporting burden for this 
collection of information is estimated to average 75 hours per 
response, including the time for reviewing instructions, searching 
existing data sources, gathering and maintaining the data needed, and 
completing and reviewing the collection of information. Send comments 
regarding this burden estimate or any other aspect of this collection 
of information, including suggestions for reducing this burden, to the 
Information and Records Management Branch (T-6 F33), U.S. Nuclear 
Regulatory Commission, Washington, D.C. 20555-0001, and to the Desk 
Officer, Office of Information and Regulatory Affairs, NEOB-10202 
(3150-0011), Office of Management and Budget, Washington, D.C. 20503.

Attachment 1--Activities and Programs Related to Maintaining Long-Term 
Capability of Safety-Related Motor-Operated Valves

    Over the last several years, licensees and permit holders have 
conducted tests of a large number of MOVs under static and dynamic 
conditions as part of the implementation of their GL 89-10 programs. 
From these tests, licensees and permit holders have identified 
significant weaknesses in the design and qualification of MOVs used in 
nuclear power plants. These weaknesses caused many MOVs to fail to 
operate properly during testing. Further, some MOVs operated adequately 
under test conditions, but analyses of the test results subsequently 
revealed that the MOVs might not have performed their safety functions 
under design-basis conditions. Licensees and permit holders are 
applying significant resources to ensure that, despite the potential 
weaknesses in original design and qualification, MOVs are currently 
capable of performing their safety functions under design-basis 
conditions.
    In completing their GL 89-10 programs, licensees and permit holders 
may have based their confidence in the current design-basis capability 
of some safety-related MOVs on the thrust/torque requirements obtained 
directly from the dynamic testing without additional margin for age-
related degradation. For some valves, licensees may have employed other 
methods (such as grouping) to establish design-basis capability. In 
some cases, the thrust/torque requirements obtained from the dynamic 
tests were significantly less than the thrust/torque required to 
operate apparently identical MOVs. Below, the staff discusses a 
research program conducted by the Electric Power Research Institute 
(EPRI) that indicates the potential for the thrust/torque required to 
operate a valve to increase with service. Aging can also decrease the 
thrust/torque output of motor actuators. Therefore, an effective 
program for periodic verification of MOV design capability will require 
that licensees understand the performance of their safety-related MOVs 
and the manner in which that performance can change with aging.
    Static diagnostic tests provide information on the thrust/torque 
output of the motor actuator and any changes to the motor-actuator 
output as a result of aging effects. The thrust and torque required to 
operate a valve are highly dependent on the differential pressure and 
flow across the valve disk, which are not present during static 
testing. Therefore, dynamic tests can provide information on the 
thrust/torque requirements and any changes to those requirements as a 
result of aging effects. Although not currently validated, efforts are 
underway within the nuclear industry to develop methods to obtain 
information from static tests that would allow prediction of valve 
dynamic performance. As discussed below, EPRI has developed an 
analytical methodology that, when combined with static test data, 
provides bounding information on the thrust/torque requirements to 
operate gate, globe and butterfly valves under dynamic conditions.
    While there may be benefits to performing dynamic testing to 
ascertain the thrust/torque requirements and changes to these 
requirements as a result of aging, there are also potential detriments 
to dynamic testing (e.g., blowdown testing by EPRI resulted in damage 
to some valves). The staff has not concluded that dynamic testing is 
the preferred method for periodic verification testing and believes 
dynamic testing may not be appropriate for certain situations. The 
proposed method for periodic verification testing and demonstration of 
a particular valve's acceptability and ability to perform consistent 
with its design basis are the responsibility of the licensee.

Electric Power Research Institute (EPRI)

    A motor-operated valve (MOV) testing program conducted by EPRI has 
provided significant information regarding the long-term design-basis 
capability of safety-related MOVs. In addition to finding that the 
thrust required to operate gate valves is typically greater than the 
thrust originally predicted by valve vendors, the EPRI program found 
that the thrust required to operate gate valves can increase with valve 
strokes until a plateau is reached. Due to limited resources and their 
view that only limited and acceptable globe and butterfly valve 
degradation would occur with repetitive valve stroking, EPRI did not 
perform similar preconditioning tests on the globe and butterfly valves 
in its MOV program. Therefore, licensees will need to demonstrate that 
the EPRI methodology predicts long-term bounding thrust/torque 
requirements for globe and butterfly valves when applied as part of an 
MOV periodic verification program. For example, information might be 
evaluated from periodic dynamic verification testing of globe and 
butterfly valves being planned by some licensees. EPRI also found that 
certain valves could be damaged during high flow and blowdown 
testing.\1\

    \1\ In addition to information applicable to MOV periodic 
verification, the EPRI program has revealed performance 
characteristics of MOVs that might adversely affect a licensee's 
determination of the current capability of certain MOVs. In 
particular, EPRI found that a high percentage of gate valves were 
damaged during hot water and steam blowdown testing with thrust 
requirements unable to be predicted. For MOVs that might be damaged 
under such conditions, EPRI established possible modifications to 
valve internals for proper clearances and for rounding sharp edges. 
With respect to globe valves, EPRI found that reliable prediction of 
globe valve thrust requirements requires an appropriate seat or 
guide area in thrust calculations. Although EPRI tested only one 
globe valve under high temperature and blowdown conditions, the test 
revealed significantly higher thrust requirements than predicted. 
EPRI also found that load-sensitive behavior (or rate of loading) 
can reduce actuator thrust output under dynamic conditions. EPRI has 
furnished the results of their MOV tests to licensees through 
industry meetings, and the NRC staff has disseminated the results of 
the tests to licensees through information notices on the EPRI test 
program and public meetings. Some licensees have already 
incorporated this information into their MOV programs.)
---------------------------------------------------------------------------

    The Nuclear Energy Institute (NEI) submitted EPRI Topical Report 
TR-103237, ``EPRI MOV Performance Prediction Program,'' describing the 
methodology developed by EPRI to predict dynamic thrust and torque 
requirements for gate, globe, and butterfly valves without dynamic 
tests by licensees. The staff prepared a safety evaluation (SE) which 
approves the topical report for use and reference. Hence, the staff 
would find it acceptable 

[[Page 6396]]
if a licensee applied the EPRI methodology (in accordance with this 
generic letter and the conditions or limitations contained in the NRC 
staff's SE) in establishing a program for periodic verification of MOV 
design-basis capability.

Boiling Water Reactor (BWR) Owners' Group

    The BWR Owners' Group submitted Topical Report NEDC 32264, 
``Application of Probabilistic Safety Assessment to Generic Letter 89-
10 Implementation,'' which provides a methodology to rank the MOVs in 
GL 89-10 programs with respect to their relative importance to core 
damage frequency, including appropriate considerations regarding other 
consequences to be added by an expert panel. The staff is issuing an SE 
on the topical report. The staff considers the methodology acceptable 
(in accordance with any conditions or limitations contained in the NRC 
staff's SE) for ranking MOVs in BWRs because the plant-specific IPE-
based insights are supplemented by generic insights and expert review 
involving additional considerations, such as external events and 
shutdown issues. In addition, the use of the MOV rankings is in 
combination with deterministic considerations that ensure a minimally 
acceptable frequency of testing is established even for the least risk-
significant valves.

NRC Research Activities

    In the 1980s, the NRC Office of Nuclear Regulatory Research (RES) 
sponsored a test program by the Idaho National Engineering Laboratory 
(INEL) to determine the thrust required to operate motor-operated gate 
valves under dynamic flow conditions. The results of the EPRI valve 
test program confirmed the findings of the NRC's smaller-scale test 
program. More recently, preliminary results from the testing of valve 
material samples sponsored by RES indicate that valve friction can 
increase with aging.
    With respect to MOV ranking, RES sponsored a study of appropriate 
frequencies of periodic testing of MOVs based on their risk 
significance. This work is summarized in an article titled ``Risk-Based 
Approach for Prioritizing Motor-Operated Valves'' in NUREG/CP-0137, 
``Proceedings of the Third NRC/ASME Symposium on Valve and Pump 
Testing.''

American Society of Mechanical Engineers (ASME)

    Licensees are currently bound by the requirements in their Code-of-
record regarding stroke-time inservice testing (IST), as supplemented 
by the additional measures they establish to ensure that MOV design-
basis capability is maintained pursuant to their GL 89-10 commitments 
or relief requests approved by the staff.
    The ASME Operations and Maintenance Code Committee has developed a 
method to verify MOV design-basis capability through periodic testing. 
Through a non-mandatory code case (OMN-1, entitled: ``Alternative Rules 
for Preservice and Inservice Testing of Certain Electric Motor Operated 
Valve Assemblies in LWR Power Plants, OM Code 1995 Edition; Subsection 
ISTC''), ASME is allowing the replacement of frequent stroke-time 
testing with periodic exercising of all safety-related MOVs once per 
cycle and diagnostic testing under static or dynamic conditions, as 
appropriate.
    With certain limitations, the staff considers the code case to meet 
the intent of this generic letter:
    (1) When implementing the code case, the staff notes as an 
additional precaution that the benefits (such as identification of 
decreased thrust output and increased thrust requirements) and 
potential adverse effects (such as accelerated aging or valve damage) 
need to be considered when determining appropriate testing for each 
MOV.
    (2) The code case states that the maximum inservice test frequency 
shall not exceed 10 years. The staff agrees with this condition of a 
maximum test interval of 10 years based on current knowledge and 
experience. In addition to this maximum test interval, where a selected 
test interval extends beyond five years, the licensee should evaluate 
information obtained from valve testing conducted during the first 
five-year time period to validate assumptions made in justifying the 
longer test interval. Based on performance and test experience obtained 
during the initial interval, a licensee may be able to justify 
lengthened MOV periodic verification intervals.
    (3) Some licensees are developing programs for risk-informed 
inservice testing. As part of an industry pilot effort, two licensees 
have submitted exemption requests to utilize a risk-informed approach 
to determine inservice test frequencies for certain components, in lieu 
of testing these components per the frequencies specified by the ASME 
Code. Licensees involved in risk-informed IST programs that seek to 
implement the ASME code case need to specifically address the 
relationship of the code case to their pilot initiative.

Plant-Specific Programs

    The staff has found effective programs for periodic verification of 
safety-related MOV design-basis capability at nuclear power plants to 
be characterized by several attributes, as follow:
     A risk-informed approach may be used to prioritize valve 
test activities, such as frequency of individual valve tests and 
selection of valves to be tested.
     The valve test program should provide adequate confidence 
that safety-related MOVs will remain operable until the next scheduled 
test.
     The importance of the valve should be considered in 
determining an appropriate mix of exercising and diagnostic testing. In 
establishing the mix of testing, the licensee should consider the 
benefits (such as identification of decreased thrust output and 
increased thrust requirements) and potential adverse effects (such as 
accelerated aging or valve damage) when determining the appropriate 
type of periodic verification testing for each safety-related MOV.
     All safety-related MOVs covered by the GL 89-10 program 
should be considered in the development of the periodic verification 
program. The program should include safety-related MOVs that are 
assumed to be capable of returning to their safety position when placed 
in a position that prevents their safety system (or train) from 
performing its safety function; and the system (or train) is not 
declared inoperable when the MOVs are in their nonsafety position.
     Licensees should evaluate and monitor valve performance 
and maintenance and periodically adjust the periodic verification 
program, as appropriate.
    Licensees of several facilities (for example, Callaway, Monticello, 
and South Texas) had established MOV periodic verification programs 
that the staff found acceptable during closure of its review of GL 89-
10 programs. One approach to MOV periodic verification that the staff 
found acceptable is to diagnostically test each safety-related MOV 
every 5 years (or every 3 refueling outages) to determine thrust and 
torque motor-actuator output and any changes in the output. A specific 
margin to account for potential degradation such as that caused by age 
(in addition to margin for diagnostic error, equipment repeatability, 
load-sensitive behavior, and lubricant degradation) is established 
above the minimum thrust and torque requirements determined under the 
GL 89-10 program. The selection of MOVs for testing and their test 
conditions should take into account 

[[Page 6397]]
safety significance, available margin, MOV environment, and the 
benefits and potential adverse effects of static and dynamic periodic 
verification testing on the selected MOV sample. Measures such as 
grouping and sharing of valve performance between facilities are 
appropriate to minimize the need to conduct more rigorous periodic 
verification tests.
    As discussed in this generic letter, the staff has long recognized 
the limitations of using stroke-time testing as a means of monitoring 
the operational readiness of MOVs (see GL 89-04) and has supported 
industry efforts to improve MOV periodic monitoring under the IST 
program and GL 89-10. As such, the staff would consider a periodic 
verification program that provides an acceptable level of quality and 
safety as an alternative to the current IST requirements for stroke-
time testing and could authorize such an alternative, upon application 
by a licensee, pursuant to the provisions of 10 CFR 50.55a(a)(3)(i).

    Dated at Rockville, Maryland, this 13th day of February, 1996.

For the Nuclear Regulatory Commission.
Theodore R. Quay,
Acting Director, Division of Reactor Program Management, Office of 
Nuclear Reactor Regulation.
[FR Doc. 96-3691 Filed 2-16-96; 8:45 am]
BILLING CODE 7590-01-P