ML20207A877

Forwards RAI Re Licensee 960213 180-day Response to GL 95-07, Pressure Locking & Thermal Binding of Safety-Related Power-Operated Gate Valves, for Plant,Units 1 & 2.Response Requested within 120 Days from Date of Ltr

ML20207A877
Person / Time
Site:	South Texas
Issue date:	05/25/1999
From:	Alexion T NRC (Affiliation Not Assigned)
To:	Cottle W HOUSTON LIGHTING & POWER CO.
References
GL-95-07, GL-95-7, TAC-MA93521, TAC-MA93522, NUDOCS 9905280012
Download: ML20207A877 (12)

Text

j-f 4 Mr. Williim T. Cottl3 May 25, 1999 Przsid2nt and Chirf Exrcutiva Officar

-l STP Nucir r Op: rating Company South Texas Project Electric

- Generating Station P. O. Box 289 Wadsworth, TX 77483

SUBJECT:

SOUTH TEXAS PROJECT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION, GENERIC LETTER 95-07 (TAC NOS. MA93521 AND l MA93522) -

]

Dear Mr. Cottle:

On August 17,1995, the Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves," to request that licensees take actions to ensure that safety-related power-operated gate valves that are susceptible to pressure locking or thermal binding are capable of performing their safety functions.

In a letter dated February 13,1996, the former operator, Houston Lighting & Power Company. )

(HL&P) submitted its 180-day response to GL 95-07 for South Texas Project, Units 1 and 2. 1 The NRC staff reviewed the submittal and requested additional information in a letter dated June 7,1996. In a letter dated July 11,1996, the HL&P provided the additional information.

The NRC staff has reviewed HL&P's GL 95-07 submittals and has determined that additional

- information is necessary to complete its safety evaluation. Enclosed is a request for additional information (RAI). This RAI was discussed with Mr. Philip Walker of your staff on May 24, 1999, and a mutually agreeable response to the RAI of within 120 days from the date of this letter was established. The staff appreciates the efforts expended with respect to this matter. If circumstances result in the need to revise the target date, please call me at your earliest opportunity. ,

Sincerely, ORIG.~ SIGNED BY Thomas W. Alexion, Project Manager, Section 1 9905280012 990525 -

Division of Licensing Project Management PDR ADOCK 05000498 P PDR Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499 j

Enclosure:

As stated cc w/ encl: See next page i DISTRIBUTION: f (SeelestM90MMOD 409y SRichards 1 )

PUBLIC OGC PDIV-1 r/f ACRS -

I SBlack r7i A3. xBrockman, Riv _

• no substantive change from RAI input,' with the exception that Terao agreed with allowing 120 days for a response per 05/24/99 telecon with Terao DOCUMENT NAME: G:\PDIV-1\SouthTexas\RAl93521.wpd To c.w. . c., or m. oocum.nunee.= m m. t>ox c.c., so .im:r-nv.nceur e-c=v wm .ncnm.nv.ncmur. N - wo ec oy OFFICE PDIV-1/PM-E PDIV-D/LA .E EMEB/SC PDIV-1/SC G NAME TAlexion r MI CJamerson k DTerao* RGrammb DATE f/b/99 .5" / ilJII /99 05/12/99 b /I/99 OFFICIAL RECORD COPY ,

78:

• p \ UNITED STATES

j. j' NUCLEAR REGULATORY COMMISSION e WASHINGTON, D.C. 30seH001

• • • • • May 25,1999 Mr. William T. Cottle

- President and Chief Executive Officer STP Nucleai Operating Company South Texas Project Electric Generating Station P. O. Box 289 Wadsworth,TX 77483

SUBJECT:

SOUTH TEXAS PROJECT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION, GENERIC LETTER 95-07 (TAC NOS. MA93521 AND MA93522)

Dear Mr. Cottle:

On August 17,1995, the Nuclear Regulatory Commission (NRC) issued Generic Letter .

(GL) 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves," to request that licensees take actions to ensure that safety-related power-operated gate valves that are susceptible to pressure locking or thermal binding are capable of performing their safety functions, in a letter dated February 13,1996, the former operator, Houston Lighting & Power Company (HL&P) submitted its 180-day response to GL 95-07 for South Texas Project, Units 1 and 2.

The NRC staff reviewed the submittal and requested additional information in a letter dated .

June 7,1996. In a letter dated July 11,1996, the HL&P provided the additional information. 1 The NRC staff has reviewed HL&P's GL 95-07 submittals and has determined that additional information is necessary to complete its safety evaluation. Enclosed is a request for additional information (RAl). This RAI was discussed with Mr. Philip Walker of your staff on May 24, 1999, and a mutually agreeable response to the RAI of within 120 days from the date of this letter was established. The staff appreciates the efforts expended with respect to this matter. If circumstances result in the need to revise the target date, please call me at your earliest opportunity.

Sincere r

Thomas W' Alexion, Project Mariager, Section 1 Project Directorate IV & Decommissioning Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosure:

As stated cc w/ encl: See next page

1. _ _ . . _ _ _ _ _ .~ --

. ~ . . . _ -

l South Texas, Units 1 & 2 i

ec:

1 Mr. Comelius F. O'Keefe Jack R. Newman, Esq.

Senior Resident inspector Morgan, Lewis & Bockius 1 U.S. Nuc!aar Regulatory Commission 1800 M Street, N.W. I P. O. Box 910 Washington, DC 20036-5869  !

Bay City, TX 77414 Mr. J. J. Sheppard l A. Ramirer/C. M. Canady Vice President  ;

City of Austin Engineering & Technical Services Electric Utility Department STP Nuclear Operating Company 721 Barton Springs Road P. O. Box 289 l Austin,TX 78704 Wadsworth, TX 77483 )

Mr. M. T. Hardt Office of the Govemor Mr. W. C. Gunst ATTN: John Howard, Director City Public Service Board Er,vironmental and Natural P. O. Box 1771 Resources Policy San Antonio, TX 78296 P. O. Box 1?428 Austin, TX 76711 i Mr. G. E. Vaughn/C. A. Johnson l Central Power and Light Company Jon C. Wood P. O. Box 289 Matthews & Branscomb MailCode: N5012 One Alamo Center Wadsworth, TX 74483 106 S. St. Mary's Street, Suite 700 San Antonio, TX 78205-3692 INPO Records Center Arthur C. Tate, Director 700 Galleria Parkway Division of Compliance & Inspection l Atlanta, GA 30339-3064 Bureau of Radiation Control Texas Department of Health j Regional Administrator, Region IV 1100 West 49th Street  ;

U.S. Nuclear Regulatory Commission Austin,TX 78756 l 611 Ryan Plaza Drive, Suite 400 '

Arlington, TX 76011 Jim Calloway Public' Utility Commission of Texas D. G. Tees /R. L. Balcom Electric Industry Analysis Houston Lighting & Power Co. P. O. Box 13326 P. O. Box 1700 Austin, TX 78711-3326 Houston, TX 77251 Mr. William T. Cottle ,

Judge, Matagorda County President and Chief Executive Officer Matagorda County Courthouse STP Nuclear Operating Company i 1700 Seventh Street South Texas Project Electric Bay City, TX 77414 Generating Station P. O. Box 289 Wadsworth, TX 77483 May 1999 I

Reauest for Additional Infqr.matiSD Resoonse to Gmef';I,Mter (GL) 95-07 South Texas Project. Uniets 1 and 2

1. The submittals dated February 13 and July 11,1996, state that the high head safety injection hot leg isolation valves, 2N121XSl0008NB/C and 2N122XSl0008NB/C, and the low head safety injection hot leg isolation valves,1N161XRH0019NB/C and 1N162XRH0019NB/C, are susceptible to thermal-induced pressure locking, are opened j 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> into the accident, that a 23-psi / 'F thermal-induced pressurization rate was applicable, that the Commonwealth (Comed) pressure-locking methodology was used to calculate the thrust required for the valves to operate during pressure-locking conditions ]

and that full voltage would be available to the valves' actuators when the valves are required to open during the design-basis accident. During a telephone call conducted '!

on May 6,1999, you stated that the valves are opened 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> into the accident in lieu of 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and that the environmental temperature of the area where the valves are {

~ located will increase approximately 40 *F during the accident.

a. Describe the basis for the 23-psi / 'F thermal-induced pressurization rate that was used in your calculations to determine maximum bonnet pressure. Testing conducted by Idaho National Engineering and Environmental Laboratory (INEEL) identified that thermal-induced pressurization rates of 50 pal / 'F are more appropriate. This testing is discussed in NUREG/CR-6611,"Results of Pressure Locking and Thermal Binding Tests of Gate Valves." Assuming zero leakage through the valve seats and stem packing, zero entrapped air and negligible pressure expansion of the valve bonnet, the theoretical increase in bonnet pressure due to temperature increase is greater than 50 psi / 'F. The staff requests that you reevaluate the use of the 23-psi / 'F thermal-induced pressurization rate for valves 2N121XSl0008NB/C,2N122XSl0008NB/C, 1N161XRH0019NB/C, and 1N162XRH0019NB/C and any other applicable valves susceptible to thermal-induced pressure locking and discuss the results of the evaluation. If applicable, discuss long-term corrective action, and any short-term corrective action to ensure operability if long-term corrective action is not complete.

b. Describe your design- and licensing-bases requirements for determining when full or degraded voltage is available to the actuators for valves 2N121 XSl0008NB/C, 2N122XSl0008NB/C, I N161 XRH0019NB/C, and I 1N162XRH0019NB/C. Explain why it is acceptable to assume that full voltage is .

available to the valves' actuators during an accident. l l

c. Your submittals state that the Comed pressure-locking calculation assumed that the initial bonnet pressure (prior to an increase in ambient temperature) in the bonnets of 2N121XSl0008NB/C,2N122XSl0008NB/C,1N161XRH0019NB/C, and 1N162XRH0019NB/C was equal to that of the static of head of water in the piping. Explain why the bonnets of these valves would not be initially pressurized to reactor coolant system (RCS) normal operating pressure due to leakage from the check valves that isolate the RCS from the safety injection system.

Enclosure

1 2

GL 95-07 states that various plant operating conditions can introduce pressure I locking and that gate valves in lines connected to high-pressure systems and i isolated only by check valves (which may transmit pressure even when passing

leak-tightness criteria) may create pressure-locking conditions. With the exception of the South Texas Project, all GL 95-07 responses that have been submitted to the NRC for review assume leakage through check valves that j separate RCS from the adjoining systems. The staff requests that you ieevaluato the potential for check valve leakage to pressurize the bonnets of valves 2N121XSl0008NB/C,2N122XSl0008NB/C,1N161XRH0019NB/C, and 1N162XRH0019NB/C and any other applicable valves that may be susceptible to pressure locking and discuss the results of the evaluation. If applicable, discuss long-term corrective action, and any short-term corrective action to ensure operability if long-term corrective action is not comp!ste.

2. In Attachment 1 to GL 95-07, the NRC staff requested that licensees include consideration of the potential for gate valves to undergo pressure locking or thermal binding during surveHlance testing. Valve stroke time testing is considered a surveillance test. During workshops on GL 95-07 in each region, the NRC staff stated that, if closing a safety-related power-operated gate valve for test or surveillance defeats the capability of the safety system or train, the licensee should per.'orm one of the following within the scope of GL 95-07:

I

a. Verify that the valve is not susceptible to pressure locking or thermal binding l while closed, '

b. follow plant technical specifications for the train / system while the valve is closed,

c. demonstrate that the actuator has sufficient capacity to overcome these phenomena, or

d. make appropriate hardwaro and/or procedural modifications to prevent pressure locking and thermal binding.

The staff stated that normally open, safety-related power-operated gate valves, which are closed for surveillance but must return to the open position, would be evaluated within the scope of GL 95-07. Please discuss if valves that meet this criterion were included in your review.

3. Enclosure 6 of your GL 95-07 submittal dated July 11,1996, states that you used an analytical method to demonstrate that pressurizer power-operated relief valve (PORV) block valves,1 R141XRC0001NB and 1R142XRC0001NB, and the RCS normal and alternate charging flow isolation valves,2R171XCV0003,2R171XCV0006, 2R172XCV0003, and 2R172XCV0006, would operate during thermal-binding conditions.

During a telephone conversation conducted on May 6,1999, you informed the NRC that this thermal binding analytical method was obtained from NUREG/CR 5807,

" improvements in Motor Operated Gate Valve Design and Prediction Models for Nuclear Power Plant Systems." Discuss any testing that was performed to validate this methodology and identify any other valves that used this methodology to demonstrate that the valves would operate during thermal-binding conditions. This thermal-binding methodology is not considered to be acceptable corrective action for GL 95-07 unless

_ - ~

3 testing demonstrates that the methodology is valid. If this methodology has not been i tested, the staff requests that you reevaluate the pressurizer PORV block valves, the RCS normal and alternate charging flow isolation valves, and any other applicable valves for susceptibility to thermal binding and discuss the results of the evaluation. If applicable, discuss long-term corrective action, and any short term corrective action to ensure operability if long-term corrective action is not complete.

4. Based on the limitations of its study, Comed recommends that when using its methodology, minimum margins should be applied between calculated pressure-locking thrust and actuator capability. These margins along with aiagnostic equipment accuracy and other methodology limitations are defined in a letter from Comed to the NRC dated May 29,1998 (Accession Number 9806040184). The margin between actuator capability and calculated pressure-locking thrust in the calculation for the pressurizer PORV block valve,1 R141XRC0001 A, provided in your GL 95-07 submittal dated July 11,1996, does not meet the Comed minimum margin provisions. The NRC staff requests that you reevaluate 1R141XRC0001 A, and any other applicable valves that do l not meet the Comed minimum margin, diagnostic equipment accuracy, and methodology limitations, and discuss the results of the evaluation. If applicable, discuss long-term corrective action, and any short-term corrective action to ensure operability if long-term corrective ackn is not complete.

5. Explain why containment spray pump (CSP) discharge valves,2N1101XCS0001 A/B/C and 2N1102XCS0001 A/B/C, are not susceptible to pressure locking following operation of the CSPs. Discuss if there are any pressure-locking scenarios where the valves will operate at locked-rotor conditions until the CSP develops full discharge pressure.

The NRC has accepted operation of motor-operated valve motor actuators for approximately 1 second at locked-rotor conditions because testing performed by INEEL  :

(NUREG/CR-6478, " Motor-Operated Valve (MOV) Actuator Motor and Gearbox Testing") demonstrates that the capability of the actuator does not degrade for that period of time.

If applicable, explain how long valves 2N1101XCS0001 A/B/C and 2N1102XCS0001 A/B/C would operate at locked-rotor conditions. If greater than approximately 1 second, explain how any reduction in actuator capability due to operation at locked rotor was accounted for or describe any testing that demonstrates that actuator capability will or will not degrade after operating at locked rotor for greater than approximately 1 second.

Discuss long-term corrective action, and any short-term corrective action to ensure operability if long-term corrective action is not complete.

I Mr. Wilitm T. Cottle May 25, 1999 Pr;sident cnd Chief ExIcutivs Officer I STP NuclIrr Operating Comp 1ny

. South Texas Project Electric

_7 Generating Station P. O. Box 289 Wadsworth,TX 77483

SUBJECT:

SOUTH TEXAS PROJECT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION, GENERIC LETTER 95-07 (TAC NOS. MA93521 AND MA93522)

Dear Mr. Cottle:

On August 17,1995, the Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves,' to request that licensees take actions to ent,ure that safety-related power-operated gate valves that are susceptible to pressure locking or thermal binding are capable of performing their safety functions.

In a letter dated February 13,1996, the former operator, Houston Lighting & Power Company (HL&P) submitted its 180-day response to GL 95-07 for South Texas Project, Units 1 and 2.

The NRC staff reviewed the submittal and requested additional information in a letter dated June 7,1996. In a letter dated July 11,1996, the HL&P provided the additional information.

The NRC staff has reviewed HL&P's GL 95-07 submittals and has determined that additional 1 information is necessary to complete its safety evaluation. Enclosed is a request for additional information (RAl). This RAI was discussed with Mr. Philip Walker of your staff on May 24, 1999, and a mutually agreeable response to the RAI of within 120 days from the date of this  ;

letter was established. The staff appreciates the efforts expended with respect to this matter. If circumstances result in the need to revise the target date, please call me at your earliest opportunity.

Sincerely, ORIG. SIGNED BY Thomas W. Alexion, Project Manager, Section 1 Project Directorate IV & Decommissioning Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50 499

Enclosure:

As stated cc w/ encl: See next page DISTRIBUTION:

Docket File (50-498/8(N00) SRichards PUBLIC OGC PDIV-1 r/f ACRS SBlack KBrockman, RIV

• no substantive change from RAI input, with the exception that Terao agreed with allowing 120 days for a response per 05/24/99 telecon with Terao DOCUMENT NAME: G:\PDIV-1\SouthTexas\RAl93521.wpd To voceive a cop r of his document. heicato m the bow C= Copy me ettechment/ enclosure E= Copy with ettschmenWenclosu,o N = No et y OFRCE PDIV-1/PM-E PDIV-D/LA .E EMEB/SC PDIV-1/SC G NAME TAlexionk N CJamerson k DTerso* RGrammk DATE f/bh S / pi/99 05/12/99 I /I/99 OFFICIAL RECORD COPY

r 1 p

y: UNITED STATES

, g NUCLEAR REGULATORY COMMISSION e WASHINGTON, D.C. 30006 40M May 25,1999 Mr. William T. Cottle President and Chief Executive Officer l

STP Nuclear Operating Company .

South Texas Project Electric '

Generating Station P. O. Box 289 '

Wadsworth,TX 77483

SUBJECT:

SOUTH TEXAS PROJECT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION, GENERIC LETTER 95-07 (TAC NOS. MA93521 AND MA93522)

Dear Mr. Cottle:

3 On August 17,1995, the Nuclear Regulatory Commission (NRC) lasued Generic Letter ,

(GL) 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate ,

Valves," to request that licensees take actions to ensure that safety-related power-operated -

gate valves that are susceptible to pressure locking or thermal binding are capable of performing their safety functions.

In a letter dated February 13,1996, the former operator, Houston Lighting & Power Company (HL&P) submitted its 180-day response to GL 95-07 for South Texas Project, Units 1 and 2.

' The NRC staff reviewed the submittal and requested additional information in a letter dated

~

June 7,1996. In a letter dated July 11,1996, the HL&P provided the additional information.

The NRC staff has reviewe; i!L&P's GL 95-07 submittals and has determined that additional information is necessary to complete its safety evaluation. Enclosed is a request for additional information (RAI). This RAI was discussed with Mr. Philip Walker of your staff on May 24, 1999, and a mutually agreeable response to the RAI of within 120 days from the date of this letter was established. The staff appreciates the efforts expended with respect to this matter. If circumstances result in the need to revise the target date, please call me at your earliest opportunity.

Sincere

• h Thomas W. Alexion, Project Manager, Section 1 Project Directorate IV & Decommissioning i DMsion of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50 499

Enclosure:

As stated cc w/ encl: See next page

.% ,.m .

..w%,.w...,.%. . -~ ~ = w eA s. w wwe'*=* ***"* * * * " ~ ~ * ~ ' * ~ ~ ^'

r South Texas, Units 1 & 2 cc:

Mr. Comelius F. O'Keefe Jack R. Newman, Esq.

Senior Resident inspector Morgan, Lewis & Bocklus U.S. Nuclear Regulatory Commission 1800 M Street, N.W.

P. O. Box 910 Washington, DC 20036-5869 Bay City, TX 77414 Mr. J. J. Sheppard A. Ramirez/C. M. Canady Vice President City of Austin . Engineering & Technical Services Electric Utility Department STP Nuclear Operating Company 721 Barton Springs Road P. O. Box 289 Austin,TX 78704 Wadsworth,TX 77483 Mr. M. T. Hardt Office of the Govemor Mr. W. C. Gunst ATTN: John Howard, Director City Public Service Board. Environmentaland Natural P. O. Box 1771 Resources Policy San Antonio, TX 78296 P. O. Box 12428 Austin,TX 78711 Mr. G. E. Vaughn/C. A. Johnson Central Power and Light Company Jon C. Wood P. O. Box 259 Matthews & Branscomb Mail Code: N5012 One Alamo Center Wadsworth, TX 74483 106 S. St. Mary's Street, Suite 700 San Antonio, TX 78205-3692 INPO Records Center Arthur C. Tate, Director 700 Galleria Parkway Division of Compliance & Inspection ,

Atlanta, GA 30339-3064 Bureau of Radiation Control Texas Department of Health Regional Administrator, Region IV 1100 West 49th Street U.S. Nuclear Regulatory Commission Austin,TX 78756 611 Ryan Plaza Drive, Suite 400 Arlington,TX 76011 Jim Calloway Public Utility Commission of Texas D. G. Tees /R. L Balcom Electric industry Analysis Houston Lighting & Power Co. P. O. Box 13326 P. O. Box 1700 Austin, TX 78711-3326 Houston,TX 77251 Mr. William T. Cottle .

Judge, Matagorda County President and Chief Executive Officer Matagorda County Courthouse STP Nuclear Operating Company 1700 Seventh Street South Texas Project Electric Bay City TX 77414 Generating Station P. O. Box 289 Wadsworth, TX 77483 May 1990

r Reauest for AdditionalInformation l

Resoonse to Generic Letter (GL) 95-07 f

.Gouth Texas Project. Units 1 and 2

1. The submittals dated February 13 and July 11,1996, state that the high head safety l injection hot leg isolation valves,2N121XSl0008A/B/C and 2N122XSl0008A/B/C, and the low head safety injection hot leg isolation valves,1N161XRH0019A/B/C and ,

1N162XRH0019A/B/C, are susceptible to thermal-induced pressure locking, are opened 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> into the accident, that a 23-psi / 'F thermal-Induced pressurization rate was applicable, that the Commonwealth (Comed) pressure-locking methodology was used to calculate the thrust required for the valves to operate during pressure-locking conditions and that full voltage would be available to the valves' actuators when the valves are required to open during the design-basis accident. During a telephone call conducted j ori May 6,1999, you stated that the valves are opened 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> into the accident in lieu '

of 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and that the environmental temperature of the area where the valves are located will increase approx!mately 40 *F during the accident. -

a. Describe the basis for the 23-psi / 'F thermal-induced pressurization rate that was used in your. calculations to determine maximum bonnet pressure. Testing conducted by Idaho National Engineering and Environmental Laboratory (INEEL) identified that thermal-induced pressurization rates of 50 pal / *F are more appropriate. This testing is discussed in NUREG/CR-6611, "Results of Pressure Locking and Thermal Binding Tests of Gate Valves." Assuming zero leakage through the valve seats and stem packing, zero entrapped air and negligible pressure expansion of the valve bonnet, the theoreticalincrease in bonnet pressure due to temperature' increase is greater than 50 pal / 'F. The staff requests that you reevaluate the use of the 23-psi / 'F thermal-induced pressurization rate for valves 2N121XS10008A/B/C,2N122XSl0008A/B/C, 1N161XRH0019A/B/C, and 1N162XRH0019A/B/C and any other applicable valves susceptible to thermal-induced pressure locking and discuss the results of the evaluation. If applicable, discuss long-term corrective action, and any short-term corrective action to ensure operability if long-term corrective action is not complete.

b. Describe your design- and licensing-bases requirements for determining when full or degraded voltage is available to the actuators for valves 2N 121 XSl0008A/B/C, 2N 122XS10008A/B/C,1 N161 XRH0019A/B/C, and 1N162XRH0019A/B/C. Explain why it is acceptable to assume that full voltage is available to the valves' actuators during an accident.

c. Your submittals state that the Comed pressure-locking calculation assumed that the initial bonnet pressure (prior to an increase in ambient temperature) in the bonnets of 2N121XSIOOO8A/B/C,2N122XS10008A/B/C,1N161XRH0019A/B/C3 and 1N162XRH0019A/B/C was equal to that of the static of head of water in the piping. Explain why the bonnets of these valves would not be initially pressurized to reactor coolant system (RCS) normal operating pressure due to leakage from the check valves that isolate the RCS from the safety injection system.

Enclosure I

1

. , a .c ,_ _ -.:~.:= = __ ,__._._-._c----~x-- - - - . . _ _ _ . _ -

]

r 2

GL 95-07 states that various plant operating conditions can introduce pressure locking and that gate valves in lines connected to high-pressure systems and isolated only by check valves (which may transmit pressure even when passing leak-tightness criteria) may create pressure-locking conditions. With the exception of the South Texas Project, all GL 95-07 responces that hsve been submitted to the NRC for review assume leakage through check valves that separate RCS from the adjoining systems. The staff requests that you .

reevaluate the potential for check valve leakage to pressurize the bonnets of valves 2N121XSl0008A/B/C,2N122XSl0008A/B/C,1N161XRH0019A/EVC, and 1N162XRH0019A/B/C and any other applicable valves that may be susceptible to pressure locking and discuss the results of the evaluation. If applicable, discuss long-term corrective action, and any short-term corrective action to ensure operability if long-term corrective action is not complete.

2. In Attachment 1 to GL 95-07, the NRC staff requested that licensees include consideration of the potential for gate valves to undergo pressure locking or thermal binding during surveillance testing. Valve stroke time testing is considered a surveillance test. During workshops on GL 95-07 in each region, the NRC staff stated that, if closing a safety related power-operated gate valve for test or surveillance defeats the capability of the safety system or train, the licensee should perform one of the following within the scope of GL 95-07:

a. Verify that the valve is not susceptible to pressure locking or thermal binding while closed,

b. follow plant technical specifications for the train / system while the valve is closed,

c. demonstrate that the actuator has sufficient capacity to overcome these phenomena, or

d. make appropriate hardware and/or procedural modifications to prevent pressure locking and thermal binding.

The staff stated that normally open, safety-related power-operated gate valves, which are closed for surveillance but must retum to the open position, would be evaluated within the scope of GL 95-07. Please discuss if valves that meet this criterion were included in your review.

3. Enclosure 6 of your GL 95-07 submittal dated July 11,1996, states that you used an analytical method to demonstrate that pressurizer power-operated relief valve (PORV) block valves,1R141XRC0001 A/B and 1R142XRC0001 A/B, and the RCS normal and alternate charging flow isolation valves,2R171XCV0003,2R171XCV0006, 2R172XCV0003, and 2R172XCV0006, would operate during thermal-binding conditions.

During a teleohone conversation conducted on May 6,1999, you informed the NRC that i this thermal binding analytical method was obtained from NUREG/CR 5807,

" improvements in Motor Operated Gate Valve Design and Prediction Models for Nuclear Power Plant Systems." Discuss any testing that was performed to validate this methodology and identify any other valves that used this methodology to demonstrate that the valves would operate during thermal-binding conditions. This thermal-binding methodology is not considered to be acceptable corrective action for GL 95-07 unless

===~:==- -- =.. - ' - - -

p 3

testing demonstrates that the methodology is valid. If this methodology has not been tested, the staff requests that you reevaluate the pressurizer PORV block valves, the RCS normal and attemate charging flow isolation valves, and any other applicable valves for susceptibility to thermal binding and discuss the results of the evaluation. If applicable, discuss long-term corrective action, and any short term corrective action to ensure operability if long-term corrective action is not complete.

4. Based on the limitations of its study, Comed recommends that when using its methodology, minimum margins should be applied between calculated pressure-locking thrust and actuator cap' ability. These margins along with diagnostic equipment accuracy ,

and other methodology limitations are de'ined in a letter from Comed to the NRC dated May 29,1998 (Accession Number 9806040184). The margin between actuator capability and calculated pressure-locking thrust in the calculation for the pressurizer PORV block valve,1R141XRC0061 A, provided in your GL 95-07 submittal dated July 11,1996, does not meet the Comed minimum margin provisions. The NRC staff requests that you reevaluate 1R141XRC0001 A and any other applicable valves that do not meet the Comed minimum margin, diagnostic equipment accuracy, and .

methodology limitations, and discuss the results of the evaluation. If applicable, discuss

. long-term corrective action, and any short-torm corrective action to ensure operability !!

long-term corrective action is not complete.

5. Explain why containment spray pump (CSP) discharge valves,2N1101XCS0001 A/B/C and 2N1102XCS0001 A/B/C, are not susceptible to pressure locking following operation of the CSPs. Discuss if there are any pressure-locking scenarios where the valves will operate at locked-rotor conditions until the CSP develops full discharge pressure.

The NRC has accepted operation of motor-operated valve motor actuators for ,

approximately 1 second at locked-rotor conditions because testing performed by INEEL (NUREG/CR-6478, " Motor-Operated Valve (MOV) Actuator Motor and Gearbox Testing") demonstrates that the capability of the actuator does not degrade for that period of time.

If applicable, explain how long valves 2N1101XCS0001 A/B/C and 2N1102XCS0001 A/B/C would operate at locked-rotor conditions. If greater than approximately 1 second, explain how any reduction in actuator capability due to operation at locked rotor was accounted for or describe any testing that demonstrates that actuator capability will or will not degrade after operating at locked rotor for greater than approximately 1 second.

Discuss long-term corrective action, and any short-term corrective action to ensure operability if long term corrective action is not complete.

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