ML20100F683

Forwards Response to GL 95-07, Pressure Locking & Thermal Binding of Safety-Related Power-Operated Gate Valves

ML20100F683
Person / Time
Site:	Hope Creek
Issue date:	02/13/1996
From:	Eric Simpson Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-95-07, GL-95-7, LR-N96034, NUDOCS 9602210492
Download: ML20100F683 (13)

Text

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- Doctnc and Gas

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• Public Service Electric and Gas Company P.O. Box 236, Hancocks Bridge, NJ 08038 609-339-1700' w u.e, . " **'""5 FEB 131996.

LR-N96034 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Gentlemen:

RESPONSE TO NRC GENERIC LETTER 95 '

PRESSURE IDCKING AND THERMAL BINDING OF SAFETY-RELATED, POWER-OPERATED GATE VALVES HOPE CREEK GENERATING STATION FACILITY OPERATING LICENSE NO. NPF-57 DOCKET NO. 50-354 The Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 95-07, Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves, on August 17, 1995. In response to GL 95-07, Public Service Electric and Gas Company (PSE&G).has completed the Requested Actions for Hope Creek i Generating Station in accordance with the 180 day schedule contained in the generic letter to ensure that safety-related power-operated gate valves susceptible to pressure locking or  :

thermal binding will be capable of performing their intended safety functions under all modes of plant operation including test configurations.

The Enclosure provides a summary description and results of the susceptibility evaluations. Attachment 1 contains the screening criteria used in determining which power operated safety related gate valves are or are not susceptible to pressure locking or thermal binding. Attachment 2 is summary listing of those safety related power operated gate valves that were determined to be susceptible to pressure locking or thermal binding based on the screening criteria contained in Attachment 1. Attachment 2 also provides a summary of the disposition of each of these valves and corrective actions completed or planned along with the schedule for completion.

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l FEB 131996 pocum.ent Control Desk 2 LR-N96034 Should you have any questions on this submittal, please contact us.

Sincerely l

Enclosure w/ Attachments (2) l Affidavit C Mr. T. T. Martin, Administrator - Region i U. S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Mr. D. Jaffe, Licensing Project Manager - Hope Creek U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 14E21 Rockville, MD 20852 Mr. R. Summers (X24)

USNRC Senior Resident Inspector Mr. Kent Tosch, Manager, IV Bureau of Nuclear Engineering 33 Arctic Parkway CN 415 Trenton, NJ 08625 l

, c REF: LR-N96034 i

STATE OF NEW JERSEY )

) SS.

COUNTY OF SALEM )

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E. C;. Simpson, being duly sworn according to law deposes and says:

I am Senior Vice President - Nuclear Engineering of Public-Service Electric and Gas Company, and as such, I find the matters set.forth in the above referenced letter, concerning Hope Creek Generating Station, are true to the best of my knowledge,

- information and' belief. ,

f Subscribed and Sworn tp before me this

/3 day of 8 / A a n 96 M 2-4 '

Notary Pubiid' of New Jerdit(By My Commission expires on . . . . .

nmu L mflyp NOTARY PUBUC OF NEWJERSEY  !

My Commission Expires Oct.13,1997 4

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eL LR-N9'6034 ENCLOSURE

SUMMARY

DESCRIPTION RESPONSE TO NRC GENERIC LETTER 95-07, PRESSURE LOCKING AND THERMAL BINDING OF SAFETY RELATED POWER OPERATED GATE VALVES HOPE CREEK GENERATING STATION DOCKET NO. 50-354 This report provides information to satisfy the 180 day reporting requirements of Generic Letter 95-07 (Ref. 1). The scope of the review for Hope Creek Generating Station includes all power operated gate valves (air, hydraulic and motor operated) for their susceptibility to pressure locking or thermal binding as follows:

- Within the requested 90 days of the issuance of the generic letter, perform a screening evaluation of all safety related power operated gate valves to identify valves potentially susceptible to pressure locking or thermal binding. Provide a basis for operability for those valves identified as susceptible as required or take appropriate actions in accordance with Technical Specifications.

- Within the requested 180 days of the issuance.of the generic letter, evaluate operational configurations of those valves identified as susceptible and perform'further analyses as appropriate. Take needed corrective actions (or justify longer schedules) to ensure valves are capable of performing their intended. safety function.

The Hope Creek response is based on a series of reviews (Refs. 7 through 10) performed since the issuance of the Reference 4 AEOD Study. The review process identified safety related power operated gate valves that have an open function. No hydraulically operated valves were determined to have a safety related open function. The identified valves were then screened for susceptibility to pressure locking'or thermal binding using the criteria in Attachment 1 based upon the design and operating conditions to which the valve may be exposed, including process and ambient conditions. Valve surveillance requirements were also considered. Attachment 2 contains a listing of those valves considered susceptible based on the screening criteria in Attachment 1. No air operated valves passed beyond this screening review.

Additional evaluations (Ref. 8) were performed including detailed Page 1 of 3

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LR-N96034 ,

ENCLOSURE

SUMMARY

DESCRIPTION 4

' operability analyses'(Refs. 8

& 9),Las required,,of the valves

. . listed in Attachment.2. ' Operability for the ten valves listed 4

Lbelow was demonstrated based on detailed Motor Operated Valve

~(MOV) : capability analyses. The concern for the 10 valves listed i

below -was a susceptibility to pressure locking. The-results-and' bases for the conclusions were reviewed with NRR and Region I representatives on October 16, 1995.  ;

Valves Analyzed for Operability ,

1BCHV-F017A,B,C&D LPCI Injection Isolation I

^

1BDHV-F013 RCIC Injection Isolation.

1BEHV-F005A&B Core Spray Injection isolation 1BJHV-F006 HPCI Discharge to Core Spray

Isolation 1BJHV-F042 HPCI Pump Suction,' Suppression Pool Isolation 1BJHV-8278 HPCI Discharge to Feedwater Isolation '

t The valves analyzed within Reference 9 have baen scheduled for modification during the current refueling outage under the  ;

Reference 11 design change with one exception (1BJHV-F042) which i has been scheduled for modification at the next refueling outage (RF07). Deferral of the modification for 1BJHV-F042 (HPCI Pump i Suction, Suppression Pool Isolation) was determined to represent ,

4 a' prudent course of action. This would allow an appropriate design evolution which would enable resolution of issues associated with-its isolation from the torus. Additionally, this .

would allow the most suitable type modification from a systems  !

interface standpoint to be implemented. Safety of the public will not be compromised on the basis that the valve has appreciable margin of capability to perform its open safety

, function should pressure locking occur. Best estimate margin of 2

capability is +71% with a' sensitivity analysis of bounding analysis factors yielding a single worst' case of +15% margin.

Prior to completion of the modification, the valve will be e maintained so-as not to adversely affect the current analyzed  ;

p capability margin.

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Page 2 of 3  ;

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'IR-N96034 ,

i ENCLOSURE ]

SUMMARY

DESCRIPTION

References:

1. NRC Generic Letter 95-07, dated August 17, 1995

2. PSE&G initial response to Generic Letter 95-07, LR-N95164, ,

1 dated October 16, 1995 >

3. INPO Significant Operating Experience Report (SOER) 84-07, dated December 14, 1984

4. NRC AEOD Study S/92-07, dated December, 1992

5. NRC Information Notice 92-26, dated April 2, 1992 1 6. NRC Generic Letter 89-10, Supplement 6, dated March 8, 1994

7. Stone & Webster Study Project No. G-0508, " Thermal Binding and Hydraulic Locking of Gate Valves for Hope Creek Generating Station", dated July 27, 1993 (Susceptibility Screening)

8. PSE&G Engineering Evaluation No. H-1-ZZ-MEE-0864, " Motor >

Operated Gate Valve Pressure Locking / Thermal Binding Review", dated March 22, 1995

9. MPR Associates, Inc. letter and enclosure, " Hope Creek Gate Valve Pressure Locking Evaluation", dated September 27, 1995

10. MPR Associates, Inc. letter and enclosure, " Hope Creek HOVs '

Potentially Susceptibile to Pressure Locking and Thermal '

Binding", dated November 14, 1995

11. Design Change-Package 4EC-3579

12. Memorandum HCT-92-100 dated May.12, 1992 Page 3 of 3

I LR-N9.6034 ATTACHMENT 1 SUSCEPTIBILITY SCREENING METHODOLOGY INITIAL SCREENING BASED ON VALVE TYPE / FUNCTION An initial screen is performed for both pressure locking and thermal binding (PL/TB) based on the valve type and function.

All safety related air , hydraulic- and motor-operated valves were identified. The bill of materials (BOM) ~for each-valve was reviewed to determine the valve type (e.g., gate, globe, butterfly, etc.). All non-gate valves are eliminated, resulting in a list of all safety-related, power-operated gate valves. The design basis requirements of each valve were then reviewed to determine if the valve has a safety function to open. Valves which are not required to open are Dot susceptible to PL/TB and were eliminated from further evaluation.

SCREENING BASED ON DISK TYPE Hope Creek valves subject to the concerns of the Generic Letter are all flex wedge gate valves based on the initial screen above for valve type / function. Therefore, no specific disc type screening was required.

SCREENING BASED ON GENERAL CONDITIONS For each valve that was not screened out based on type / function, modifications or disk type, the general conditions under which the valve operates were reviewed to determine if it is susceptible to PL/TB. This screening is described below.

Pressure Lockina Pressure locking occurs when the fluid in the valve bonnet is at a higher pressure than the adjacent piping at the time of valve opening. The following two scenarios for elevated bonnet pressure were considered.

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" Bonnet Heatup" -- entrapment of incompressible fluid in the bonnet during valve closure, followed by bonnet heat-up prior to valve opening. The bonne heatup scenarios considered were:

heatup due to an increase in the temperature of the environment during an accident. (Normal ambient

< temperature variation is not considered because it occurs over a long time period and pressure changes tend to be alleviated through extremely small amounts Page 1 of 3

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i LR-N96034

- ATTACHMENT 1 i SUSCEPTIBILITY SCREENING METHOD 0 LOGY  ;

of leakage. Experience indicates that normal -

temperature variations are not a source of pressure  !

locking events),  !

heatup due to an increase in the temperature of the l process fluid on either side of the valve. l

. " Pressure-Trapping" -- pressurization of the valve bonnet during. normal system operation or system surveillance test conditions, followed by de-pressurization of the adjacent

. piping prior to valve opening. The following scenarios were considered:  ;

back-leakage past check valves, and v system operating pressures (including surveillance test i conditions) which are higher than the system pressure when the valve is required to open.

The normal and accident temperature envelopes from environmental design criteria for various plant locations were used to identify i potential heatup of the environment. The applicable P& IDS, 1 isometric drawings and Configuration Baseline Documents (CBDS) ,

! were reviewed to determine process fluid temperatures and nearby 4

heat sources. The CBDs were also used to determine the conditions when the valve is required to open to perform its ,

design basis function and the conditions under which the valve is '

closed. Valves for which there were no plausible bonnet heatup

or pressure-trapping scenarios are n21 susceptible to pressure

' locking.

i The following assumptions were made in performing this screening

, evaluation. -l

\

. 1. For valves in water systems, the bonnet is completely filled with water upon valve closure.

. 2. There is ne leakage from the bonnet either through the l l packing or through the bonnet-to-body seal. I

3. The disk-to-seat seal allows leakage from the adjacent

piping to the bonnet but not from the bonnet to the adjacent j pip ing.

l 4. Check. valves allow sufficient leakage such that the I Page 2 of 3

4 LR-N96034 ATTACHMENT 1

SUSCEPTIBILITY SCREENING METHODOLOGY pressures are the same on both sides of the check valve.

Thermal Bindina Thermal binding occurs due to temperature changes of valve

< internal components. The following scenarios for thermal binding were considered.

The process fluid temperature is greater than the ambient 3

temperature when the valve, is closed, which can result in heat up and expansion of the stem after insertion (closure).

The valve temperature increases or decreases between the time the valve is closed and then opened under design basis conditions, which can result in:

- Differential expansion of the disk and body, and

- Differential expansion of the body and stem The environment and process fluid temperatures during valve closure and subsequent opening under design basis conditions were determined as described above for pressure locking. Valves for which there were no plausible scenarios, as described above, were not susceptible to thermal binding. <

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-l ATTACHMENT 2 l-l EVALUATION'OF SUSCEPTIBLE VALVES r

i VALVE VALVE FUNCTION SUSCEPT- DISPOSITION-ACTUATOR ID. IBILITY NOTE 1BCHV-F004A'& B RHR PUMP A&B TO SUPPRESSION POOL SUCTION B NOTE 1

1BCHV-F007A-D RHR PUMP A-D MINI-FLOW H NOTE 2 1BCHV-F008 RHR SHUTDOWN COOLING OUTBOARD SUCTION H NOTE 3 ,

ISOLATION 1BCHV-F009 RHR. SHUTDOWN COOLING INBOARD SUCTION B NOTE 3 i ISOLATION 1BCHV-F016A & B RHR LOOP A&B CONTAINMENT SPAAY OUTBOARD H NOTE 4 ,

t ISOLATION i

1BCHV-F017A-D RHR LPCI INJECTION ISOLATION H -NOTE 5 j 1BCHV-F021A & B RHR LOOPS A&B CONTAINMENT SPRAY INBOARD H NOTE 4-ISOLATION ,

1BDHV-F013 RCIC INJECTION H NOTE 5 1BDHV-F031 RCIC PUMP SUCTION FROM SUPPRESSION POOL H NOTE 6  ;

1BEHV-F005A & B CORE SPRAY IDOPS A&B INBOARD INJECTION H NOTE 5  ;

1BJHV-F006 HPCI DISCHARGE TO CORE SPRAY ISOLATION H NOTE 5 1BJHV-F042 HPCI PUMP SUCTION FROM SUPPRESSION POOL H NOTE 5 ISOLATION i

1BJHV-8278 HPCI DISCHARGE TO FEEDWATER ISOLATION H NOTE 5 1FDHV-F001 HPCI TURBINE STEAM ADMISSION B NOTE 7 ,

1 T - THERMAL BINDING Page 1 of 4 H - HYDRAULIC IDCKING B - BOTH

LR-N96034 ATTACHMENT 2 EVALUATION OF SUSCEPTIBLE VALVES Note 1: A potential concern exist's should the second loop of Shutdown Cooling (SDC) be aligned when the first loop is operating at a high temperature. During the subsequent open stroke of the valve in the off going loop, thermal binding may occur. Pressure locking is also a potential concern in the standby SDC loop, should water in the bonnet heatup due to the potential physical proximity to an operating SDC flowpath. This is the' liquid entrapment type pressure locking scenario.

At Hope Creek, a normal shutdown closes the RHR Torus Suction Valves 1BCHV-F004A or B with torus fluid temperatures low, then opens F006A or B for RHR Shutdown Cooling alignment. For normal shutdown cooling, thermal input to F004A & B occurs after the valves are already closed and does not represent a safety concern should thermal binding occur. In a post accident situation, F004A or B is closed with torus flow as hot as 271*F. With the alignment to RHR and subsequent cooldown, the F004 valves may experience some thermal binding. Since the F004 valves do not have any design basis requirement to be opened, this is not a safety concern. Also, when either loop is in Shutdown Cooling, the loop is considered Inoperable for LPCI, Torus Cooling, and Containment Spray. These other modes of RHR. require the respective suction valve to be open. This is not a safety Concern.

Pressure locking occurrences caused by liquid entrapment have occurred in the industry due to relatively rapid fluid temperature increases (Refs. 3 & 4). Liquid entrapment and pressurization of the bonnet cavity can potentially occur should the valve disk and the valve packing provide a 100% seal. This is not credible given a slow ambient temperature increase. The maximum ambient temperature analyzed for pressure locking is 148'F (65'C). This does not relate to a rapid temperature increase associated with liquid entrapment and bonnet cavity pressurization of the F004A & B valves. Temperatures above 148'F occur.in the Reactor Building only under High Energy Line Break (HELB) conditions. These valves are not required to stroke to mitigate the consequences of a HELB in the Reactor Building based on Hope Creek Environmental Design Criteria and UFSAR Sections 3.6.1 and 3.6.3.

The "A" and "B" loop PHR torus suction valves (1BCHV-F004A & B) have over 38 feet of ?.4" diameter horizontal piping from the Shutdown Cooling 110wpath based on RHR isometric drawings. These valves are also considere' !.noperable for LPCI, Torus cooling, or Containment Spray whm. 9o3ed during Shutdown Cooling operation.

They must be successfully opened prior to being considered Page 2 of 4

LR-N96034 -

ATTACHMENT'2 EVALUATION OF SUSCEPTIBLE VALVES operable for the alternate modes.

On the basis'of the preceding discussion, liquid entrapment does not present a concern for these valves at Hope Creek.

Note 2: The RHR minimum flow valves are located in the Torus Room. A High Energy Line Break (HELB) could increase the ambient temperature in the room. The HELB to heat Room 4102 is caused by a HPCI Steam Line Break (UFSAR, TABLE 3. 6-5) . Operation of RHR is not required to mitigate the consequences of a HPCI steam line break external to primary containment-(UFSAR, Sections 3.6.1 and 3.6.3).

Note 3: The thermal binding issue suggested by the Reference 4 AEOD Study was caused by hand torquing the Valve closed. At Hope Creek, a hand torqued closed MOV is considered inoperable /

incapable of performing a remote open stroke. The safety design bases for the RHR Shutdown Cooling Suction (1BCHV-F008 & F009) valves is to be opened manually at the valve (UFSAR SECTION 5.4.7.1.5). Since this flow path is not single failure proof, the alternate shutdown cooling flow path is available as discussed by UFSAR section 15.2.9. Therefore, remote operation l of these valves is not a design basis requirement. )

Note 4: The RHR drywell spray valves are located in different i pipe chases. A significant distance of separation exists between the different divisions of these valves. A High Energy Line i Break (HELB) (UFSAR Pg. 6.3-5) would not affect more than one l division. Opening of more than one division is not allowed by I the Emergency Operating Procedures (EOPs). When one set of these I I

valves are operated in accordance with the EOPS, upstream pressure is near shutoff head of the corresponding RHR pump and not at keep fill pressure. Also, drywell spray is not required to mitigate the consequences for a break external to primary containment.

Note 5: This valve was determined to require additional analysis ,

to demonstrate operability based on detailed MOV capability l analyses. Although demonstrated to be operable, these valves  ;

were determined to require a design change to enable relief of l bonnet cavity pressure. A relief path will be provided by installation of a 1/8" weephole in the high pressure side of the valve disc. The valve internals will be refurbished as required to assure proper performance. These modifications will be completed during the current RFO6 outage with the exception of 1BJHV-F042. This valve will be modified during RF07. The justification for deferring completion of the modification to Page 3 of 4

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LR-N96034 ATTACHMENT 2 EVALUATION OF SUSCEPTIBLE VALVES this valve until RFO7 is provided in the enclosed Summary Description.

Note 6: The RCIC torus suction valve strokes open, based on flowrate and inventory, at least 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> after an isolation event. Pressure' locking would require a High Energy Line Break to increase the local ambient temperature. Automatic Isolation Systems monitor area temperatures and differential temperatures in the areas where high energy systems are located. RCIC system operation is not' required for a HELB in the torus room'(UFSAR Pg 3.6-27 and Table 3.6-5).

Note 7: The HPCI Steam Admission Valve (1FDHV-F001) physically drains to a large unlagged drain pot which continuously rejects condensate via a steam trap. This maintains the valve hot at near steam temperature. There is approximately a 160 degree difference between the valve temperature when the valve could be closed during surveillance testing and the lower temperature when it may be required to automatically open. HPCI is required to pass both a high pressure (high saturated temperature) and a low pressure (low saturated temperature) full flow test by Technical Specifications 4.5.1.b.3 & 4.5.1.c.2.a. When stroking during the low pressure test,' 1FDHV-F001 demonstrates that a 160*F temperature decrease does not thermally bind the valve. When the HPCI system is secured during a normal cooldown, the HPCI Steam Supply Isolation Valves (1FDHV-F002 & F003) are closed at approximately 350*F. These isolation valves are cycled for surveillance testing purposes during cold shutdown. No thermal binding of these valves has been indicated over a broader temperature decrease than applicable to F001. Since these three valves are essentially the same, the ability of the F002 & F003 to open demonstrates the capability of the F001 to perform its safety function.

The pressure locking event identified in the AEOD study was caused by improper system draining and warmup. Should the valve be used as a pressure blocking ~ point during a steam system hydro, any water inventory should be removed post hydro by opening (cracking) the valve prior to returning the system to service.

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