NRC Generic Letter 1995-07
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001 August 17, 1995 NRC GENERIC LETTER 95-07: PRESSURE LOCKING AND THERMAL BINDING OF
SAFETY-RELATED POWER-OPERATED GATE VALVES
Addressee that have been All holders of operating licenses (except those licenses permits for nuclear power amended to possession-only status) or construction reactors.
PurDose The U.S. Nuclear Regulatory Commission (NRC) thatis issuing this generic letter to previously performed, request that addressees perform, or confirm of they safety-related, power-
(1)evaluations of operational configurations gate valves for operated (including motor-, air-, and hydraulically-operated)
and (2) further susceptibility to pressure locking and thermalto binding ensure that safety-related analyses, and any needed corrective actions, are susceptible to pressure locking or thermal power-operated gate valves that within the current binding are capable of performing the safety functions licensing bases of the facility.
for addressing NRC previously provided guidance on an acceptable approach valves (MOVs) in pressure locking and thermal binding of motor-operated Motor-Operated Supplement 6 to Generic Letter (GL) 89-10,not Safety-Related request specific actions by Valve Testing and Surveillance," but did This letter confirms (as licensees to address these problems at that time. are expected, under ,
was indicated earlier in Supplement 6) that licensees to ensure that safety- existing regulations, to take actions as necessary pressure locking or thermal related power-operated gate valves susceptible to safety functions. The binding are capable of performing their required directly from (and is guidance in Attachment 1 to this letter is derived 1 to GL 89-10,
intended to be the same as) the guidance in Enclosurethe guidance is being issued Supplement 6, except in this generic letter (1) implementation by licensees who as an approved genericONRC-staff position for pressure locking and thermal binding have not already satisfactorily addressedSupplement 6 (or equivalent industry of MOVs by implementing the guidance in locking and thermal methods); and (2)the guidance also includes pressure (i.e., air- and binding phenomena in other types of power-operated as MOVs. Additional information hydraulically operated) gate valves, as well basic approach to addressing provided in Attachment 1 does not alter the in Supplement 6 to GL 89-10.
pressure locking and thermal binding given valves, this letter requires that Finally, for MOVs and other power-operated regarding any actions licensees submit for staff review summary information locking or thermal binding taken to ensure that valves susceptible to pressure
95081102&085003 Q9E(
k- rGL 95-07 August 17, 1995 including are capable of performing their required safety functions,to implement the guidance
(1) actions taken by licensees on their own volition as well as provided in Supplement 6 (or equivalent industry methods),
Supplement 6 to GL 89-10,
(2) actions taken in response to this letter. (In pressure locking and the staff did not require any licensee response regarding thermal binding.)
a preliminary evaluation In this generic letter, the NRC staff is requesting power-operated gate of pressure locking and thermal binding of safety-related and resolution of the valves and, subsequently, a more detailed evaluation issue.
Background of disk binding The NRC staff and the nuclear industry have been aware has issued several event problems of gate valves for many years. The industry valves to operate due to reports describing failure of safety-related gate disks. Several of the pressure locking or thermal binding of the valve for identifying industry's generic communications have given guidance and corrective susceptible valves and for performing appropriate preventive pressure-locking and measures. Despite industry awareness of the problem, to events at U.S.
thermal-binding events continue to occur. In addition events was nuclear power plants, French experience with pressure-locking of the Third recently documented in NUREG/CP-0137 (July 1994), "Proceedings NRC/ASME Symposium on Valve and Pump Testing."
of operating licenses and In GL 89-10 (June 28, 1989), the staff asked holders of the capability of construction permits to provide additional assurance systems to safety-related MOYs and certain other MOVs in safety-related licensees were asked to perform their safety-related functions. In GL 89-10 both initially and review MOV design bases, verify MOV switch settings where practicable, periodically, test MOVs under design-basis conditions action, and trend improve evaluations of MOV failures and necessary corrective GL 89-10 (March 8, 1994), the MOV problems. In Enclosure 1 to Supplement 6 to to address pressure NRC staff described one acceptable approach for licensees valves.
locking and thermal binding of motor-operated gate
"Pressure Locking and In March 1993, the NRC issued NUREG-1275, Volume 9,the history of pressure- Thermal Binding of Gate Valves." This NUREG gives discusses the locking and thermal-binding events, describes the phenomena,summarizes consequences of locking or binding on valve functionality, of the phenomena.
preventive measures, and assesses the safety significance valve to fail Pressure locking or thermal binding can cause a power-operated safety train or system to to open, resulting in an inability of the associatedthermal binding represent perform its safety function. Pressure locking and redundant trains of potential common-cause failure modes that can render incapable of certain safety-related systems or multiple safety systems surveillance tests or normal performing their safety functions. Existing operating cycles might not reveal such failures.
GL 95-07 August 17, 1995 Descriotion of Circumstances After Issuing Volume 9 of NUREG-1275, the NRC staff performed a number of site visits to discuss pressure locking and thermal binding with licensees (1) to gather information on the technical issues andrelated to generic and plant-
(2)to determine the specific valve and system characteristics guidance for identification of implementation status of previous industry and corrective measures. NRC
susceptible valves and application of preventive of generic industry surveys indicated that in response to the number have performed multiple reviews communications on the subject, some licensees the staff found only of pressure locking and thermal binding. However, alleviate the effects of limited instances of valves being modified to pressure locking and thermal binding.
In Enclosure I to Supplement 6 of GL 89-10, the NRC staff reminded licensees to take actions to ensure that they are expected under existing regulations susceptible to pressure locking that safety-related motor-operated gate valvestheir required safety functions, or thermal binding are capable of performing and permit holders to and described an acceptable approach for licensees of motor-operated gate valves as address pressure locking and thermal binding on pressure locking and part of their GL 89-10 programs. The information provided in Enclosure 1 to thermal binding of motor-operated gate asvalves timely notification of operating Supplement 6 of GL 89-10 was intended GL 89-10 programs, the staff found experience feedback. During inspections ofpressure locking and thermal binding the actions taken by licensees to address many licensees had of motor-operated gate valves to be varied. Although for pressure locking and conducted some level of review of the potential valves, few licensees had either thermal binding of their motor-operated gate the motor actuators to overcome the
(1)thoroughly evaluated the capability ofregarding MOV and system performance, phenomena in light of recent information the phenomena as discussed in or (2)taken corrective action to prevent results, the NRC staff has Supplement 6. In view of these inspection is now warranted to ensure that determined that issuing this generic lettersusceptible to pressure locking or safety-related power-operated gate valves their required safety functions.
thermal binding are capable of performing GL 89-10 programs. In meetings most licensees are nearing completion of theirthe staff stated that, during its with industry representatives and licensees, progress being made by licensees GL 89-10 closure review, it will assess the binding of motor-operated gate in addressing pressure locking and thermal need not complete their response valves. The staff also stated that licenseesissue at the time that the to the pressure-locking and thermal-binding of MOYs within the scope of verification of the design-basis capability evaluate the acceptability of GL 89-10 is completed because the staff would thermal binding of all safety- addressee resolution to pressure locking and MOVs, in a consolidated effort related power-operated gate valves, including to this generic letter).
(through evaluation of actions taken in response letter would address the schedule Finally, the staff stated that this generic pressure locking and thermal for completing the licensees' response to the binding issue.
"2 GL 95-07 August 17, 1995 February 4, 1994, to discuss pressure The NRC staff held a public workshop on including prioritization of locking and thermal binding of gate valves, A summary of the public workshop is susceptible valves for corrective action. (Accession Number 9403020090) and available in the NRC Public Document Room locking and thermal binding, contains information on evaluation of pressure of susceptible valves.
and actions taken in response to the identification Notice (IN)95-14, On February 28, 1995, NRC issued Information Gate Valves to Pressure
- Susceptibility of Containment Sump Recirculation licensees to a report by Northeast Locking." This information notice alertedMillstone Nuclear Power Station, Nuclear Lnergy Company, the licensee for motor-operated gate valves Unit 2, that both containment sump recirculation a design-basis loss-of-coolant might experience pressure locking during On March 15, 1995, NRC issued accident and fail in the closed position. Safety-Related Power-Operated Gate IN 95-18, OPotential Pressure-Locking of by Connecticut Yankee Atomic Power Valves," alerting licensees to a reportNuclear Power Plant, that seven motor- Company, the licensee for Haddam Neck systems were susceptible to operated gate valves in the safety injectionoperability of the valves may have pressure locking to the extent that the been Jeopardized.
licensee performed an evaluation which On June 13, 1995, the Millstone Unit 2 valve (PORV) block valves were determined that the power-operated relief Specifically, it was found that, potentially susceptible to thermal binding. a subsequent plant cooldown was if the PORV block valves were closed and thermal binding. In GL 90-06, performed, the block valves could experience Relief Valve and Block Valve
'Resolution of Generic Issue 70, 'Power-Operated Low-Temperature Overpressure Reliability,' and Generic Issue 94, 'Additional to 10 CFR 50.54(f)," the staff Protection for Light-Water Reactors,' Pursuantin their GL 89-10 program.
asked licensees to include PORV block valves not be classified as safety related Therefore, although PORV block valves mayexpected to have evaluated these at particular plants, licensees will beor thermal binding. Similarly, valves for potential pressure locking pressure locking or thermal licensees may need to evaluate for potential of this generic letter based on binding other valves outside the scope previous licensing commitments.
Discussion phenomena are based on well-known The pressure-locking and thermal-binding valves and the determination of concepts. The identification of susceptible a thorough knowledge of components, when the phenomena might occur require locking occurs in flexible-wedge and systems, and plant operations. Pressure pressurized within the valve bonnet double-disk gate valves when fluid becomes the additional thrust and the actuator is not capable of overcoming pressure created across both requirements resulting from the differential the valve bonnet. For example, the valve disks by the pressurized fluid in normal open and close valve fluid may enter the valve bonnet (1) during pressure across a disk causes the disk cycling, (2) when a fluid differential a path to either increase the to move slightly away from the seat, creating
'- GL 95-07 August 17, 1995 or (3) for a steamline valve, fluid pressure or fill the bonnet with fluid, the disk and the valve orientation when differential pressure exists across the bonnet. Surveillance testing can permits condensate to collect and enter or thermal binding. For example, cause a valve to experience pressure locking core isolation cooling (RCIC) system an inboard isolation MO in the reactor plant failed in the closed position steamline at a boiling-water reactor (BWR)Pressure locking and thermal binding following routine surveillance testing. not necessarily render a valve can occur to varying degrees, but does damage may occur.
incapable of operating, although valve pressure locking. Pressure Various plant operating conditions can introduce anticipated, causing pressure locking in the valve bonnet might be higher than when (1)the gate valve is in a line under certain conditions. For example, only by check valves (which connected to a high-pressure system and isolated criteria) and may transmit pressure even when passing leak-tightness results from thermal
(2)bonnet volume temperature increases, pressurization in the valve bonnet might expansion of the confined fluid. Temperature operation, ambient air temperature increase in response to heatup during plant breaks, or thermal conduction or rise due to leaking components or pipe Over time, bonnet pressure could convection through connected piping. surfaces or stem packing. However, the decrease by leakage past the seating the system response time to initiate depressurization time may be longer thanfunction. Also, valve actuator valve actuation to perform its safety for seconds could degrade the motor operation at locked rotor conditions gatea few valve.
torque capability of a motor-operated a wedge gate valve that is closed Thermal binding is generally associated with to cool before attempting to open while the system is hot and then is allowed occurs because of different expansion and the valve. Mechanical interference valve body and disk materials. Thus, contraction characteristics of the the valve and disk are reheated.
reopening the valve might be prevented until to thermal binding. However, Solid-wedge gate valves are most susceptible significant temperature changes or flexible-wedge gate valves experiencing temperature differences may operating with significant upstream and downstream thermally bind.
Pressure locking or thermal binding occurs as a result of the valve design characteristics (wedge and valve body isconfiguration, flexibility, and material thermal coefficients) when the valve plantsubjected to specific pressures and Operating experience temperatures during various modes of always operation.
considered as part of the design indicates these situations were not basis for valves in many plants.
Reguested Actions letter, each addressee of this Within 90 days of the date of this generic the following actions:
generic letter is requested to perform and complete operational configurations of all Perform a screening evaluation of themotor-operated,
1. air-operated, and safety-related power-operated (i.e., those valves that are hydraulically operated) gate valves to identify or thermal binding; and potentially susceptible to pressure locking
3 > V GL 95-07 August 17, 1995 the potentially susceptible Document a basis for the operability beofsupported,
2. take action in valves or, where operability cannot Specifications.
accordance with individual plant Technical letter, each addressee of this Within 180 days of the date of this genericand complete the guidance provided in generic letter is requested to implement Attachment 1 to perform the following actions:
Evaluate the operational configurations of safety-related power-operated
1. hydraulically operated) gate (i.e., motor-operated, air-operated, andthat are susceptible to pressure valves in its plant to identify valves locking or thermal binding;
take needed corrective
2. Perform further analyses as appropriate,to and ensure that the susceptible actions (or Justify longer schedules), performing their intended safety valves identified in 1 are capable ofoperation, including test function(s) under all modes of plant configuration.
options for gate valves found Attachment 2 discusses potential resolution binding.
susceptible to pressure locking or thermal an evaluation of operational
[Note: If a licensee has previously performed gate valves susceptible to pressure configurations to identify motor-operated additional analyses and taken locking or thermal binding, and has performed in a manner that needed corrective actions for identifiedinvalves, Supplement 6 to GL 89-10 (or satisfactorily implements the guidancethe identified valves are capable of equivalent industry methods) so that the licensee need not perform any performing their required safety functions, for MOVs.J
additional action under paragraphs 1 and 2 above Reguested Information All addressees, including those who have already satisfactorily addressed MiOVs by implementing the guidance in pressure locking and thermal binding for industry methods), are requested to Supplement 6 to GL 89-10 (or equivalent provide a summary description of the following:
configurations performed in
1. The susceptibility evaluation of operational Action 1, and the response to (or consistent with) 180-daytoRequested consistent with) 180-day further analyses performed in response or (or criteria for determining that Requested Action 2, including the bases locking or thermal valves are or are not susceptible to pressure binding;
and the further analyses
2. The results of the susceptibility evaluation of the susceptible valves referred to in 1 above, including a listing identified;
- Aug, 17, 1995 Pag6_/ of 9
3. The corrective actions, or other dispositioning, for the valves identified as susceptible to pressure locking or thermal binding, including: (a) equipment or procedural modifications completed and planned (including the completion schedule for such actions); and (b) Justification for any determination that particular safety-related power-operated gate valves susceptible to pressure locking or thermal binding are acceptable as is.
The staff believes that a corrective action schedule (if corrective actions are needed) may be based on risk significance, including consideration of common cause failure of multiple valves. Plant operation and outage schedules may also be considered in developing corrective action schedules. However, the time schedules for completing corrective action in response to pressure locking or thermal binding concerns do not supersede the requirements of the NRC regulations and individual plant Technical Specifications in the event that a safety-related valve is determined to be incapable of performing its safety function. In GL 91-18 (November 7, 1991), 'Information to Licensees Regarding Two NRC Inspection Manual Sections on Resolution of Degraded and Nonconforming Conditions and on Operability," the staff provides guidance on the review of operability determinations and resolution of degraded and nonconforming conditions by licensees. An addressee's schedule for completing corrective action in response to this generic letter will be considered independent from GL 89-10.
Reguired Response All addressees are required to submit the following written response 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 above. If the addressee intends to implement the requested action(s), provide a schedule for completing implementation. If an addressee chooses not to take the requested action(s), provide 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, a written response to the information request specified 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 shall be submitted to the appropriate regional administrator.
A :> <<_ V GL95-07 August 17, 1995
Backfit Discussion
safety
10 CFR Part 50 (Appendix A, Criteria 1and 4) and plant licensing and test safety- analyses require and/or commit that the addressees design that those related components and systems to provide adequate assurance criteria in systems can perform their safety functions. Other individual In accordance with Appendix A to 10 CFR Part 50 apply to specific systems. the additional those regulations and licensing commitments, and under licensees are provisions of 10 CFR Part 50 (Appendix B,Criterion XVI), power-operated gate expected to take actions to ensure that safety-related binding are capable of valves susceptible to pressure locking or thermal 6 to GL 89-10 alerted performing their required safety functions. Supplement binding in MOVs, thermal licensees to the problems with pressure locking and these phenomena for MOVs, and described an acceptable approach for addressing from licensees.
but did not request any specific actions or response The actions requested in this generic letter are considered compliance and existing NRC procedures, backfits, under the provisions of 10 CFR 50.109 valves that are susceptible to ensure that safety-related, power-operated gate of performing their to pressure locking or thermal binding are capable of 10 CFR 50.109 intended safety functions. In accordance with the provisions was not performed for regarding compliance backfits, a full backfit analysis a documented evaluation which this proposed action; but the staff performed actions and the basis stated the objectives of and reasons for the requested of this evaluation will be made for invoking the compliance exception. A copy available in the NRC Public Document Room.
Federal Register Notification A notice of opportunity for public comment was published in the Federal Register (60 FR 15799) on March 27,1995. Comments were received from and 1private company. Copies of the
14 licensees, 1 industry organization, in the NRC Public staff evaluation of these comments will be made available Document Room.
Paperwork Reduction Act Statement by the The information collections contained in this request are covered which expires Office of Management and Budget clearance number 3150-0011, collection of information July 31, 1997. The public reporting burden for this per response, including the time for is estimated to average 75 hours8.680556e-4 days <br />0.0208 hours <br />1.240079e-4 weeks <br />2.85375e-5 months <br /> gathering and reviewing instructions, searching existing data sources, and reviewing the collection of maintaining the data needed, and completing any other aspect information. Send comments regarding this burden estimateforor reducing this of this collection of information, including suggestions U.S.
burden, to the Information and Records Management Branch (T-6F33), and to the Desk Nuclear Regulatory Commission, Washington, D.C. 20555-0001, (3150-0011),
Officer, Office of Information and Regulatory Affairs, NEOB-10202 Office of Management and Budget, Washington, D.C. 20503.
A . K> "-__ GL 95-07 August 17, 1995 Licensee response to the following request for in information is purely voluntary. This information would assist NRC evaluating the cost of complying with this generic letter:
inspections,
1. The licensee staff time and costs to perform requested corrective actions, and associated testing;
reports and
2. The licensee staff time and costs to prepare the requested documentation;
3. result of the inspection The additional short-term costs incurred as aactions findings such as the costs of the corrective or the costs of down time;
will be incurred in
4. An estimate of the additional long-term costs which such as the estimated the future as a result of implementing commitments maintenance.
costs of conducting future inspections or increased If you have any questions about this matter, please contact the technical contact or lead project manager listed below, or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
9-J4'1 Dennis M. Crutchfield, Director Division of Reactor Program Management Office of Nuclear Reactor Regulation Technical contacts: Howard J. Rathbun, NRR
(301) 415-2787 Thomas G. Scarbrough, NRR
(301) 415-2794 Lead project manager: Ronald B. Eaton, NRR
(301) 415-3041 Attachments:
1. Guidance for Addressing Pressure Locking and Thermal Binding of Power-Operated Gate Valves
2. Description of Potential Resolution Options for Gate Valves Found Susceptible to Pressure Locking or Thermal Binding
3. List of Recently Issued NRC Generic Letters kffldl'V~ [V6 4_4 Q_ )L-
->Attachment I
GL 95-07 August 18, 1995 GUIDANCE FOR ADDRESSING PRESSURE LOCKING AND
THERMAL BINDING OF POWER-OPERATED GATE VALVES
The material that follows summarizes one acceptable approach to addressing pressure locking and thermal binding of gate valves within the scope of the accompanying generic letter:
1. Perform an evaluation of the safety-related power-operated gate valves having operational configurations that may be susceptible to pressure locking or thermal binding. Document the basis for determining whether valves (a)are susceptible to pressure locking or thermal binding or (b)
can be removed from further consideration. For example, solid wedge disk gate valves might not be susceptible to pressure locking. Double disk gate valves are not likely to be susceptible to thermal binding.
The absence of a heat source could be a basis for eliminating valves from consideration of susceptibility to thermally induced pressure locking.
The evaluation should include consideration of the potential for gate valves to undergo pressure locking or thermal binding during surveillance testing.
The evaluation also should include review of generic studies for site- specific applicability, such as in the areas of thermal effects and design-basis depressurization. For example, the potential for thermally induced pressure locking of containment sump recirculation valves was recently recognized. Licensees should also be aware that efforts to improve the leak-tightness of primary system valve pressure boundaries could increase susceptibility to pressure locking.
Examples of unacceptable reasons as the sole basis for eliminating valves from consideration of pressure locking or thermal binding are (a)leakage rate, (b)engineering judgement without justification, and (c)lack of event occurrence at the specific plant.
Several plants have experienced either pressure locking or thermal binding in safety-related and non-safety-related systems. These cases are discussed in NUREG-1275, Volume 9. Examples of gate valves involved in pressure locking events are:
- low-pressure coolant injection (LPCI) and low-pressure core spray (LPCS) system injection valves;
- residual heat removal (RHR) system hot-leg crossover isolation valves;
\~-J Attachment 1 GL 95-07 August 17, 1995 suction valves;
- high-pressure coolant injection (HPCI)
- RHR heat exchanger outlet valves;
- emergency feedwater isolation valves; and
- RCIC steamline isolation valve.
binding events are:
Examples of gate valves involved in thermal valves;
- reactor depressurization system isolation
- RHR inboard suction isolation valves;
- HPCI steam admission valves;
valves;
- power-operated relief valve (PORV) block valves;
- reactor coolant system letdown isolation
- RHR suppression pool suction valves;
letdown heat exchanger
- containment isolation valves (sample line, Inlet header);
- condensate discharge valves; and
- reactor feedwater pump discharge valves.
Perform a further analysis of the safety-related, power-operated gate
2.
valves identified (in1 above) as suchsusceptible to either pressure locking can be opened to perform or thermal binding to ensure all modes valves of plant operation, including test their safety function under all configuration.
gate valve is found to be If a safety-related, power-operated thermal binding and the addressee susceptible to pressure locking or to overcome pressure locking or relies on the capability of the actuator uncertainties surrounding the thermal binding, consideration of the overcome these phenomena should be prediction of the required thrust to for bonnet pressure decay within the included in the evaluation. Credit unless operation of the valve response time may not be acceptable degrade actuator capability.
actuator under those conditions will not these phenomena, sliding In calculating thrust required to overcome than valve factors determined friction coefficients are more appropriate output capability in in the flow stream. Prediction of actuator
- \- Attachment 1 GL 95-07 August 17, 1995 response to pressure locking and thermal binding should be consistent with other evaluations of safety function capability (such as GL 89-10
programs for IOVs).
Attachment 2 to this generic letter describes potential resolution valves options that may be used by licensees for power-operated gate Several found susceptible to pressure locking or thermal binding.
preventive and corrective measures for pressure locking and thermal binding are also discussed in NUREG-1275, Volume 9, though each method has limitations with respect to applicability, safety, effectiveness, and cost.
CFR 50.59 for any valve The NRC regulations require an analysis under 10 post-modification of adequate and modifications and the establishment the modification.
inservice testing of any valves installed as part of For example, addressees may need to evaluate the effects of drilling the hole in the disk if this option is used to resolve a pressure-locking concern. One consideration is the fact that, with athe hole in one disk and the other flexible disk allowing fluid to enter valve bonnet, the valve will be leak-tight with respect to pipe flow in only one direction.
As required through Appendix B to 10 CFR Part 50, the any addressee may need to establish training for plant personnel to perform necessary procedural precautions/revisions into actions and incorporate specific personnel the existing plant operating procedures. For example, plant potential for might periodically stroke certain valves to reduce the thermal binding.
X * KJL *,-,ttachment 2 GL 95-07 August 17, 1995 Valves Description of PotentialPressure Resolution Options for Gate Binding Locking or Thermal Found Susceptible to to Overcome the Thrust
1. AnalYSS On to Justif Adequate CapabilitY BindinQ
Reauirements of Pressure LockinQ or Thermal the prediction of the thrust required to overcome The staff considers An addressee locking or thermal binding to be very difficult. to pressure able to justify adequate actuator capability in response of the may be (e.g., small) valves. Because pressure locking for certain and material expansion will and contraction uncertainties in valve geometries be required the staff believes considerable effort to characteristics, alternative in a manner adequate by a licensee to justify this binding.
resolve concerns regarding thermal Thrust Oni l to Justify Adequate CapabilitY to Overcome the
2. Testina or Thermal Bindins Requirements of Pressure Locking or prototype demonstrate through an in-situ An addressee may be able to adequate capability to overcome pressure test that the actuator hasvalve. The staff considers this alternative locking for a particular thermal binding concerns because of the difficult to justify for plant and valve conditions.
uncertainty in modeling actual CapablitY to of Testinc and Analysis to Justify Adequate Binding
3. A Combination Thrust Requirements of Pressure Locking orThermal Overcome the of the demonstrate adequate capability An addressee may be able to locking based on test information from the actuator to overcome pressure together with an or similar valves from other sources, staff particular valve applicability. As with Alternative 2, the analysis to demonstrate binding difficult to justify for thermal considers this alternative concerns.
Thermal or Binding Modifications toPrevent Pressure Locking
4. EguiDment to considers this to be the least difficult alternative valves.
The staff locking of susceptible gate justify in addressing pressure to prevent pressure locking are Examples of possible modifications thermal
9. Modifications to preventvalve with a provided in NUREG-1275, Volume such as replacing a wedge gate binding are also possible, parallel-disk gate valve.
Thermal or Binding Modifications to Prevent Pressure Locking
5. procedure alternative considers procedure modification to be a strong to thermal The staff of gate valves. As opposedjustifiable for preventing thermal binding are less likely to be a binding, procedure modifications pressure locking of gate valves.
alternative for preventing
__ Attachment 3 GL 95-07 August 17, 1995 Page I of I
LM F ECNTL ISID GENERIC LETTERS
LJST OF RECENTLY ISSUED
Generic Date of Letteir lzihizef t _ _.._ J _
-___. zbu ance issued lo
95-06 CHANGES IN THE OPERATOR 08/15/95 ALL HOLDERS OF OLs LICENSING PROGRAM (EXCEPT THOSE LICENSES
THAT HAVE BEEN AMENDED
TO A POSSESSION ONLY
NUCLEAR POWER REACTORS.
95-05 VOLTAGE-BASED REPAIR CRITERIA 08/03/95 ALL HOLDERS OF OLs OR
FOR WESTINGHOUSE STEAM GEN- CPs FOR PRESSURIZED
ERATOR TUBES AFFECTED BY OUT- WATER REACTORS (PWRs).
SIDE DIAMETER STRESS CORROSION
CRACKING
92-01, REACTOR VESSEL STRUCTURAL 05/19/95 ALL HOLDERS OF OLs REV. 1, INTEGRITY (EXCEPT THOSE LICENSES
SUPP. 1 THAT HAVE BEEN AMENDED TO
POSSESSION-ONLY STATUS)
OR CONSTRUCTION PERMITS
FOR NUCLEAR POWER
REACTORS.
95-04 FINAL DISPOSITION OF THE 04/28/95 ALL HOLDERS OF OLs OR
SYSTEMATIC EVALUATION CPs FOR NUCLEAR POWER
PROGRAM LESSONS-LEARNED ISSUES REACTORS.
95-03 CIRCUMFERENTIAL CRACKING OF 04/28/95 ALL HOLDERS OF OLs OR
STEAM GENERATOR TUBES CPs FOR PRESSURIZED
WATER REACTORS (PWRs).
95-02 USE OF NUMARC/EPRI REPORT 04/26/95 ALL HOLDERS OF OLs OR
TR-102348, RGUIDELINE ON CPs FOR NUCLEAR POWER
LICENSING DIGITAL UPGRADES," REACTORS.
IN DETERMINING THE ACCEPT-
ABILITY OF PERFORMING
ANALOG-TO-DIGITAL REPLACE-
MENTS UNDER 10 CFR 50.59 OL = OPERATING LICENSE
CP = CONSTRUCTION PERMIT
NPR - NUCLEAR POWER REACTORS
- .August 17, 1995 Licensee response to the following request for information is purely voluntary. This Information would assist NRC in evaluating the cost of complying with this generic letter:
1. The licensee staff time and costs to perform requested inspections, corrective actions, and associated testing;
2. The licensee staff time and costs to prepare the requested reports and documentation;
3. The additional short-term costs incurred as a result of the inspection findings such as the costs of the corrective actions or the costs of down time;
4. An estimate of the additional long-term costs which will be Incurred in the future as a result of implementing commitments such as the estimated costs of conducting future inspections or increased maintenance.
If you have any questions about this matter, please contact the technical contact or lead project manager listed below, or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager. orig /s/'d by BKGrimes/for Dennis M. Crutchfield, Director Division of Reactor Program Management Office of Nuclear Reactor Regulation Technical contacts: Howard J. Rathbun, NRR
(301) 415-2787 Thomas G. Scarbrough, NRR
(301) 415-2794 Lead project manager: Ronald B. Eaton, NRR
(301) 415-3041 Attachments:
1. Guidance for Addressing Pressure Locking and Thermal Binding of Power-Operated Gate Valves
2. Description of Potential Resolution Options for Gate Valves Found Susceptible to Pressure Locking or Thermal Binding
3. List of Recently Issued NRC Generic Letters DOCUMENT NAME: 95-07.GL
To receive a copy of this document, Indicate in the box CaCopy W/o attachment/en -Copy with attachment/enclosure M a No copy I OFFICE N:NRR l 1C/F:l- IDIIl lNAME RE l HFIELDl DATE
NAM 0/ /95
- A~*~& 08/e5'/95 . 08/f .THI
/95 ____.____._
Nv OFFICIAL RECORD COPY