ML20005E224

Responds to Generic Ltr 89-10, Safety-Related Motor- Operated Valve Testing & Surveillance. Util Views Item 1 as Generic Backfit & Hesitant to Commit to Requirement Until After Impact Determined for Plant

ML20005E224
Person / Time
Site:	Vogtle
Issue date:	12/27/1989
From:	Hairston W GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ELV-01139, ELV-1139, GL-89-10, IEB-85-003, IEB-85-3, NUDOCS 9001040118
Download: ML20005E224 (11)

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               .,-       Georg.a Power Company
                       . 333 Pedmont Avenue ~

A'Janta. Georgia 30308 Telephone 404 526 3195

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h Meng Addrest 40 invemess Center Parkway Post Othee Box 1295 f3rmingham Atacama35201

Telephone 205 B68 5581 '

the soutrem elettrc system ' w.G.Ha W on,Ill December 27,--1989 Senior Vce President Nuclear Operattorts

                                                                                             .ELV-01139 0156 Docket Nos.             50-424 50-425~

U.- S. Nuclear Regulatory Commission ATTN: Document Control-Desk-Washington, D. C. 20555 Gentlemen: V0GTLE ELECTRIC GENERATING PLANT GENERIC LETTER 89-10 SAFETY-RELATED MOTOR OPERATED VALVE TESTING AND SURVEILLANCE On June 28,J 1989, the NRC issued Generic Letter (GL) 89-10, " Safety-Related Motor-0perated Valve- (MOV) Testing and Surveillance." The GL extended the recommendations outlined in NRC Bulletin 85-03 and its supplement to all safety-related and ." position-changeable" MOVs. The Reporting Requirements (Item 1)-requested that each licensee advise the NRC whether the recommendations and schedule contained in the GL would be met. The letter further requests that, for any recommendation which could not be met, the licensee should-present technical justification along with alternative actions and/or schedules. The enclosure to this letter provides the requested information. Georgia Power Company (GPC) concurs with the need to increase the overall functional reliability associated with MOVs, and will extend its program for the testing, inspection and maintenance of safety-related MOVs above that currently required by ASME Section XI. However, GPC has concerns regarding two major issues associated with M0V testing and GL 89-10. The two major issues are:

1. Requiring utilities to consider inadvertent mispositioning of MOVs, including those valves in safety-related systems which do not have an active safety function, and

2. Requiring utilities to test MOVs at maximum differential pressure.

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r Geo@iaPcnver A U. S. Nuclear Regulatory Commission ELV-Oll39 . Pace'Two We believe item (1) is a generic backfit and are hesitant to commit to this requirement until its impact has been determined for the Vogtle Electric . Generating Plant. The issue of differential pressure (dP) testing and valve performance at full dP conditions is very complex and is by-no means resolved technically.. Georgia Power Company unoarstands that the Nuclear Management and Resources Council (NUMARC) is planning to meet with the Staff to discuss industry concerns associated with GL 89-10. In the past, guidance from NUMARC has been used to help formulate programs which are acceptable to the NRC. Unfortunately, because ' of the complex issues surrounding this issue, clear guidance on an acceptable program is not available prior to this submittal in response to Generic Letter 89-10. The enclosure provides our response as requested by Generic Letter 1 89-10; however, we believe communications with the Staff will probably'be required. ' Our program, which began under NRC Bulletin 85-03, concentrates on ensuring the actuator / valve units are electrically and mechanically sound. At this time, it is our intent to complete the design basis review and static testing of safety-related valves within 5 years or three refueling outages. We hope the enclosed information is helpful in your review. Please contact this office if you have questions. Sincerel , f W* W. G. Hairston III WGH,III/PAH/gm

Enclosures:

1. Enclosure 1

2. Enclosure 2 xc: Georaia Power Comoany Mr. G. Bockhold, Jr., General Manager - Vogtle Plant Mr. P. D. Rushton, Manager Engineering and Licensing - Vogtle Mr. L. A. Ward, Manager Nuclear Maintenance and Support - Vogtle U. S. Nuclear Reaulatory Mr. S. D. Ebneter, Regional Administrator Mr. J. B. Hopkins, Licensing Project Manager - Vogtle Mr. J. F. Rogge, Senior Resident Inspector, Vogtle

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ENCLOSURE 1 INTRODUCTION Vogtle Electric Generating Plant (VEGP) has established a comprehensive program,.which, when implemented, will ensure that motor-operated valves (MOVs) as described below are set-up and maintained properly. The program was- initially developed to satisfy the requirements of NRC Bulletin 85-03 L but has since been expanded to include many additional valves. To date, approximately 200 MOVs have been set-up statically utilizing diagnostic equipment and approximately 45 of these valves have been tested under. differential pressure. Vogtle . Electric Generating Plant feels that an aggressive predictive / preventive maintenance program is- the key element in ensuring that MOVs will -operate on demand. Meticulous initial set-up utilizing diagnostic equipment followed by regularly scheduled preventive maintenance will eliminate the vast majority of problems which have been experienced throughout the industry involving MOVs. The VEGP' program is based on this concept and has been very successful to date. The existing VEGP MOV program has already been expanded well - beyond the requirements of NRC Bulletin 85-03 and is well on its way to including all safety-related and position-changeable MOVs as recommended in NRC Generic 1 Letter 89-10. The following is a brief summary of VEGP's position regarding each of the recommendations contained in the subject generic letter, l L RECOMMENDATION

SUMMARY

l l L Generic letter 89-10 Recommendation "A" l' " Review and document the design basis for the operation of each M0V. This l documentation should include the maximum differential pressure expected i during both the opening and closing-of the MOV for both normal operations I and abnormal events, to the extent that these M0V operations and events are ! included in the existing approved design basis." VEGP Response to Recommendation "A" A design basis review will be performed for each MOV covered by the generic p letter. The design basis review will include, as a minimum, the following:

1. Identification of all safety-related and position-changeable MOVs covered by the generic letter.

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2. Determination of the maximum differential pressure for each MOV.

3. Calculation of the minimum required opening and closing thrust and/or torque values for each M0V.

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                            ; 4.-   Evaluation of operator capability for each MOV to determine the maximum allowable thrust and/or torque including consideration for degraded voltage operation.

The generic letter states that any MOV in a safety-related system that is not blocked from inadvertent operation must be capable of recovering from an inadvertent mispositioning. This is clearly beyond the existing design basis _ for the plant and must be addressed in the design basis review. (See Enclosure 2). Safety-related MOVs may be required to operate against higher differential pressure following mispositioning than when performing their design basis function. Non-safety MOVs, which are not designed to perform an active' safety function and which are not currently included in the inservice test (IST) program, may be required to operate against higher differential pressures than originally designed. The implications of requiring position-changeable MOVs to be capable of recovering from an inadvertent mispositioning will be more clearly understood as the design basis review progresses. Determining maximum differential pressures' associated with an inadvertent mispositioning scenario will be complex and time consuming. For valves which are required to operate against a higher differential pressure when recovering from mispositioning than when performing their design basis function, the potential exists that valve operators may be undersized. Georgia Power Company (GPC) will evaluate the impact of requiring MOVs to recover from inadvertent mispositioning and formulate a position with regard to this aspect of the generic letter as additional data becomes available. Generic letter 89-10 Recommendation "B" "Using the results from item a., establish the correct switch settings. This should include establishing a program to review and revise, as necessary, the methods for selecting and setting all switches (i.e., torque, torque bypass, position limit, overload) for each valve operation (opening and closing). One purpose of this letter is to ensure that a program exists for selecting and setting valve operator switches to ensure high reliability of safety-related MOVs." VEGP Resoonse to Recommendation "B" The program implemented at VEGP to comply with the requirements of NRC Bulletin 85-03 established policies for setting torque, torque bypass and position limit switches. These policies, in combination with the minimum required and maximum allowable torque and/or thrust values calculated in

                               -the design basis review, will be utilized in setting up each M0V. The thermal overloads on all safety-related MOVs at VEGP are jumpered during operation; therefore, no engineering review of thermal overloads will be required.

Generic letter 89-10 Recommendation "C"

                                 " Individual MOV switch settings should be changed, as appropriate, to those established in response to item b. Whether the switch settings are changed or not, the MOV should be demonstrated to be operable by testing it at the

   . ,7   r design-basis differential pressure and/or flow determined in response to item     a. Testing MOVs at design-basis conditions is not recommended where such testing is precluded by the existing plant configuration.                 An explanation should be documented for any cases where testing with the design-basis differential pressure or flow cannot practicably be performed.

This explanation should include a description of the alternatives to design-basis differential pressure testing or flow testing that will be used to verify the correct settings. Note: .This letter 'is not intended to establish a-recommendation for valve testing for the condition simulating a break in the line containing the

            -MOV.       However, a break in the line should be considered in the analyses described in items a.,          b., and c. if MOV operation is relied on in the design basis.

Each MOV should be stroke tested, to verify that - the MOV is operable at no-pressure or no-flow conditions even if testing with differential - pressure or flow cannot be performed." VEGP Response to Recommendation "C" Each M0V will be set up statically utilizing M0V test equipment. All switches will be set based upon policies established in NRC Generic Letter 89-10 item "B" with sufficient margin to ensure operability at maximum differential pressure. No differential pressure testing is planned beyond that which has - already been performed in conjunction with NRC Bulletin 85-03. The need to perform additional differential pressure testing will be assessed as the design basis review progresses.

             . Generic letter 89-10 Recommendation "D"
                " Prepare or revise procedures to ensure that correct switch settings are
               ' determined and maintained throughout the life of the plant.              These procedures should include provisions to monitor MOV performance to ensure the switch settings are correct. This is particularly-important if the torque or torque bypass switch setting has been significantly raised above that required.

It may become necessary to adjust M0V switch settings because of the effects of wear or aging. Therefore, it is insufficient to merely verify that the switch settings are unchanged from previously established values. The switch settings should be verified in accordance with the program schedule (see item j.). The ASME Code Section XI stroke-timing test required by 10 CFR Part 50 is not oriented toward verification of switch settings. Therefore, additional measures should be taken to adequately verify that the switch settings ensure M0V operability. The switch settings need not be verified each time the ASME Code stroke-timing test is performed." VEGP Resoonse to Recommendation "D" Plant procedures were developed or revised to ensure that correct switch settings are determined and maintained to comply with the requirements of NRC Bulletin 85-03. These procedures cover diagnostic testing as well as i

           . electrical- and mechanical maintenance.             All maintenance activities involving: MOVs covered by the generic letter will be controlled to ensure
            .that Maintenance Engineering reviews any work performed and evaluates the
            'need for retesting to verify switch settings.

Generic Letter 89-10 Recommendation "E" "Regarding item - a. , no change to the existing plant design basis is intended and none should be inferred. The design-basis review should not be restricted to' a ' determination of estimated maximum design-basis differential pressure, but should include an examination of the pertinent design and installation' criteria that were used in choosing the particular MOV. For example, the review should include the effects on MOV performance of' design-basis degraded voltage, including the capability of the M0V's power supply and cables to provide the high initial current needed for the

             -operation of the MOV."

VEGP Response to Recommendation "E" As stated in item "A," a design basis review will be performed for each MOV covered by the generic letter. This review will include an evaluation of valve operator capability at degraded voltage as well as re.werification of the adequacy of the M0V's power supply and cables. Item "E" of the generic letter states that "no change to the existing design -basis-is intended and none should be inferred". This appears to conflict- with the statement "When determining the maximum differential pressure or flow for position-changeable MOVs, the fact that the MOV must be able-to recover from mispositioning should be considered". As stated in response to item "A", the impact of requiring MOVs to recover from inadvertent mispositioning will be evaluated and a position regarding this aspect of the generic letter will be formulated as the design basis review

              -progresses.      (See Enclosure 2).

Generic letter 89-10 Recommendation "F"

                " Documentation of- explanations and the description of actual test methods used for accomplishing item c. should be retained as part of the required records for the M0V.

It is also recognized that it may be impracticable to perform in situ MOV testing- at design-basis degraded voltage conditions. However, the switch settings established in response to item b. should at least be established to account for the situation where the valves may be called on to operate at design-basis differential pressure, or flow, and under degraded voltage conditions. If the licensee failed to consider degraded voltage, power supply, or cable adequacy for MOVs in systems covered by Bulletin 85-03, the design review and established switch settings for those M0Vs should be reevaluated. Alternative to testing a particular M0V in situ at design-basis pressure or fl ow, where such testing cannot practicably be performed, could include a comparison with appropriate design-basis test results on other MOVs, either in situ or prototype. If such test information is not available,

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r c.. ,+ 3 D' analytical -methods and extrapolations. to design-basis conditions, based on i the best data available, may be used until test data at design-basis conditions become available to verify operability of the M0V.- If this

two-stage approach is followed, it should be accomplished within the schedule outlined in item 1, and would allow for MOV testing and surveillance to proceed without excessive delay.

Testing of MOVs at design basis conditions need not be repeated unless the l M0V is replaced, modified, or overhauled to the extent that the licensee considers that the existing test results-are not representative of the MOV in its modified configuration." VEGP Response to Recommendation "F" As stated in response to Recommendation "A," all MOVs covered by the generic letter will be set up statically based on calculated values. The-calculations will consider degraded voltage to ensure that the switch , settings selected are adequate to ensure operability under degraded voltage ' conditions. No degraded voltage testing or additional differential I pressure testing is planned at this time. With respect to differential pressure testing, the generic letter states "it is not clear that tests of an M0V at low or moderate pressure differentials can be directly extrapolated to determine correct switch settings at design-basis conditions using any type of diagnostic equipment". This statement implies that each valve should be tested at maximum differential pressure, an approach which is neither possible nor

                                                        -practical. The letter goes on to state " demonstrating operability in situ at design basis conditions is not practical for some MOVs". We understand L                                                         the generic letter recognizes that it is not possible to test all valves at l                                                         maximum differential pressure. However, it does not provide any guidance l                                                         as to what would be an acceptable alternative.

L The workshops which were held to review the generic letter have raised additional questions relative to differential pressure -testing and acceptable alternatives. The Idaho National Engineering Laboratory (INEL) testing was discussed and the results of this testing seem to have caused I the -NRC to take a more conservative position with regard to demonstrating

• l valve operability. It was stated in the Washington meeting that the NRC did not have confidence' that data taken at reduced differential pressure could be extrapolated to predict loads at maximum differential pressure nor did they have confidence that data taken on one valve was necessarily applicable to another essentially identical valve. The NRC stated that the only methodology in which they have complete confidence is to test each L valve at maximum differential pressure thus demonstrating operability.

Several issues need to be considered relative to the INEL testing. First, b the testing was restricted to two valves operating under simulated pipe l break isolation conditions. Data based on test results involving two valves operating at these extreme conditions should not be construed as being representative of the typical M0V. Second, the testing and subsequent data evaluation took many months to perform under essentially ideal conditions and in reality, the testing raised more questions than it answered. For an individual utility to undertake a research and

      -r development      program of sufficient magnitude to address all         of the-outstanding questions relative to valve thrust requirements would require a-     ;

tremendous commitment of both time and money. An operating. nuclear power

               -plant is not the proper environment for conducting a program of this type.

The Electric Power Research Institute (EPRI) has undertaken a program to develop . improved methodology to calculate and predict valve thrust requirements. As many as twenty parameters have been identified which may . have some effect on valve / actuator performance. Until the industry has a clear. understanding of which parameters are significant and how they affect TK:ve performance, an extensive program of in situ dynamic testing would be ptemature. It is virtually impossible to simulate all design basis conditions when -performing in situ testing and without an approved methodology for extrapolating test conditions to design basis conditions the results are of limited value. L Georgia Power Company will continue to track and participate _in industry ? and NRC efforts addressing MOV issues. As additional data and guidance becomes available, it will be considered, and if appropriate, factored into the1 VEGP M0V program to ensure that the program remains current and addresses the relevant issues. Generic letter 89-10 Recommendation "G" "A number of deficiencies, misadjustments, and degraded conditions were discovered by licensees, either as .a result of their efforts to comply with Bulletin 85-03 or from other experiences. A list of these conditions (including improper switch settings) is included in Attachment A to this letter for licensee review and information." VEGP Response to Recommendation "G" The implementation of an aggressive predictive / preventive maintenance program is essential to attain a high level of motor-operated valve reliability. Maintaining each MOV in peak mechanical and electrical condition is the most important factor in ensuring that MOVs will perform on demand. VEGP has- implemented a preventive maintenance program which addresses MOVs and has performed extensive diagnostic testing beyond the requirements of NRC Bulletin 85-03. Generic letter 89-10 Recommendation "H" Each MOV failure and corrective action taken, including repair, alteration, analysis, test, and surveillance, should be analyzed or justified and documented. The documentation should include the results and history of each as-found deteriorated condition, malfunction, test, inspection, analysis, repair, or alteration. All documentation should be retained and reported in accordance with plant requirements. It is suggested that these MOV data be periodically examined (at least every 2 years or after each refueling outage after program implementation) as part of a monitoring and feedback effort to establish trends of MOV operability. These trends could provide the basis for a licensee revision of the testing frequency established to periodically verify the adequacy of

 .      v MOV switch settings (see items d. and j.) for this monitoring and feedback effort,- a' well-structured and component-oriented system (e.g., the Nuclear Plant Reliability Data System -{NPRDS) is needed to capture, track, and share the equipment history data. The NRC encourages the use of the industry-wide NPRDS, appropriately modified, for this purpose in view. of the multiple uses for these data."

VEGP Response to Recommendation "H" Maintenance Engineering is procedurally notified of all work associated with NRC Bulletin 85-03 valves . This allows Maintenance Engineering to evaluate the work being performed to ensure that it adequately addresses the problem and to specify any additional inspection and/or testing which may be required. This program will be expanded to include the valves covered by the generic letter. Historical records of.all maintenance work orders (MW0s) are contained in the Nuclear Plant Management Information System (NPMIS) and are available for review at any time. n .. . t [3 ENCLOSURE 2 DISCUSSION OF SINGLE FAILURE CRITERIA The generic letter explicitly states that "no change to the existing plant design basis is intended and none should be inferred"; however, during the Washington, D. C. workshop, the staff stated that certain aspects of the generic letter do go beyond the design basis of the plant. Specifically, in replying to a question, Mr. Jacobson of the NRC indicated that:

                                                 "this may go beyond your design-basis in the fact that we're saying that these valves have to be repositioned. Your design-basis may take as a single failure an operator error. You may say I've got another train that can handle it. What we're saying is you cannot take that as your single L

failure. You cannot take an operator error as single failure". [ Additionally, at the same meeting the NRC stated:

                                                 "A March ;.,, 1987 letter from Edward Jordan who was then director of the  i l-                                                fonner NRC Office of Inspection Enforcement, to the BWR Owners Group       1 stated the need to consider mispositioning even-though this may be beyond  i the design-basis for some plants. In regard to Generic letter 89-10, the fact that mispositioning may be beyond a plant's design basis has been t                                                 fully addressed in the NRC review process for the generic letter.

Particularly, a backfit analysis was prepared for the generic letter and , approved." i l The statement that "you cannot take an operator error as a single failure" negates earlier NRC guidance for designing nuclear power plants.  ; L Specifically, NRC guidance in SECY 77-439 " Single Failure Criterion", states:

                                                 "An active failure in a fluid system means (1) the failure of a component which relies on mechanical movement for its operation to complete its intended function on demand, or (2) an unintended movement of the component. Examples include the failure of a motor or air-operated valve to move or to assume its correct position on demand, spurious opening or closing of motor or air operated valve, or the failure of a pump to start or to stop on demand. In some instances such failures can be induced by operator error".

Spurious opening or closing of a valve has histcA ally been interpreted as a single failure which may be caused by the operator incorrectly positioning the valve.

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a I ENCLOSURE 2 (CONTINVED) The design basis for the Vogtle Electric Generating Plant assumed an operator error as defined in American National Standard Institute (ANSI) 58.9-1981. This standard defines as active failure as:

                   " active failures. An active failure is a malfunction, excluding passive failures, of a component that relies on mechanical movement to complete its intended function upon demand.

Examples of active failures include the failure of a powered valve or a check valve to move to its correct position, or the failure of a pump, fan, or diesel generator to start. Spurious operation of a powered component due to a failure originating within its automatic actuation or control systems shall be regarded as an active failure unless specific features or operating restrictions (such as

                    " racking out" a breaker to a motor-operator valve) are incorporated to prevent such spurious operation. An example of spurious operation is the unintended energizing of a powered valve to open or close."

Additionally, the standard states:

                    "3.7   The designer shall consider an operator error as a potential single active failure".

This guidance was used in the design basis for the Vogtle Electric Generating Plant , This design basis assumed that the incorrect positioning of a valve due to operator error was a single failure. The position stated by the NRC indicates recovery from an assumed single failure. VEGP was designed to achieve a safe shutdown condition, considering an assumed single failure.

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