ML20203B926

Forwards Suppl Responses to GL 95-07, Pressure Locking & Thermal Binding of Safety-Related Power Operated Gate Valves, as Requested During 970611 Telcon.Commitment Associated W/Cycle 9 Design Changes Included

ML20203B926
Person / Time
Site:	Sequoyah
Issue date:	12/01/1997
From:	Salas P TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20203B931	List: ML20203B926 ML20203B959 ML20203B973
References
GL-95-07, GL-95-7, NUDOCS 9712150188
Download: ML20203B926 (7)

Text

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IM Tennesete Vahy Authority. Post ONe Box 2000, Soddy-Dat; Tennessee 37379-2000 December 1, 1997 >

U.S. Nuclear Regulatory Commiss. ion ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

.In the Matter of ) Docket Nos. 50-327 Tennessee Valley Authority ) 50-328 SEQUOYAH NUCI7H PLANT (SQN) - SUPPLEMENTAL RESPONSE TO GENERIC LETTER sGL) 95 PRESSURE LOCKING AND THERMAL BINDING OF SAFETY-RELATED POWER OPERATED GATE VALVES

References:

1. TVA letter t.o NRC dated August 6, 1996, "Sequoyah Nuclear Plant (SON) - Units 1 and 2

- Response 1 NRC Request for Additional Information - Generic Letter (GL) 95-07,

' Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves' (TAC Nos. M93519 and M93520)"

2. TVA letter to NRC dated March 15, 1996,

" Browns Ferry (BFN) Sequoyah (SQN), and Watts Bar (WBN) Nuclear Plants - Supplemental ,

Response to Generic Letter (GL) 95 ' Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves'"

The purpose of this letter is to provide additional information that supplements TVA's previous GL 95-07 responses in the above references.

In June 1997, NRC conducted an inspection (Inspection Report 97-06) of SQN's GL 89-10 program. During this inspection, NRC requested that TVA address several questions related to information provided in References 1 and 2. On June 11, ,

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1997, a teleconference between NRC and members of SQN's Engineering organization was held to discuss the staff's questions. TVA. resolved a portion of the questions and geh, g agreed to provide the enclosed information as a supplement

, , , , ,, to SQN's previous GL 95-07 responses. The enclosed 9712150188 971201 DR -

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0.S. Nuclear Regulatory Commiselon Page 2 December 1, 1997 information will support completion of NRC's review of GL 95-07 for SON.

TVA is providing commitments that involve design changes that will be implemented during the Cycle 9 refueling outages for both units. The design changes eliminate any concerns relative to calculation methodology or available valve margins and completely removes the potential for pressure locking on the following valves:

FCV-63-25 FCV-63-26 FCV-72-2 FCV-72-39 FCV-72-40 FCV-72-41 Note that documentation previously provided in References 1 and 2 forms the basis for operability on the above valves.

Enclosure 1 provides the additional information associated with NRC questions from the June 11, 1997, teleconference.

Enclosure 2 provides a TVA commitment associated with the Cycle 9 design changes.

Please direct questions concerning this issue to me at (423) 843-7170 or J. D. Smith at (423) 843-6672.

Sine r, Pedro Salas Licensing and Industry Affairs Manager Subscribed o this /T and sworn day oftg{/t&oyhM)befoye

/ me fM) YkL Ld '

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My Commission Expires 7>/ O 2 / /b

[/ [gdf JDS:DVC:PMB Enclosures cc: See page 3

0.S. Nuclear Regulatory Commission Page 3 December 1, 1997 cc (Enclosures):

Mr. R. W. Hernan, Project Manager Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 Mr. Michael H. Mobley, Director (w/o Enclosures)

Division of Radiological Health Third Floor-L&C Annex 401 Church Street Nashville, Tennessee 37243-1532 NRC Resident Sequoyah Nuclear Plant 2600 Iyon Ferry Road Soddy-Jatsy, Tennessee 37379-3624 Regione.1 Administrator U.S. Nuclear Regulatory Commission Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303-3415

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ENCLOSURE 1 TENNESSEE VAILEY AUTHORITY SEQUOYAH NUCLEAR PLANT (SQN)

UNITS 1 AND 2 SUPPLEMENTAL RESPONSE TO GENE"'C LETTER (GL) 95 PRESSURE LOCKING AND THERMAL BIND 1 4G OF SAFETY-RELATED POWER OPERATED GATE VALVES NRC REQUEST SON's Referenced 2 letter included calculations to determine thrust requirements to overcome pressure locking. These calculations were performed utilizing the " Grand Gulf" methodology. NRC has identified several restrictions associated with this methodology. TVA agreed that calculations would be performed in accordance with the

" Commonwealth Edison" methodology and resubmitted for the following valves:

FCV-01-016 FCV-62-138 FCV-63-001, -006, -007, -156, -157 FCV-68-332, -333 TVA RESPONSE TVA has performed calculations in accordance with the Commonwealth Edison methodology and adequate margin exists for the above valves. The calculations are provided in Attachment A to this enclosure.

NRC REQUEST SON has contracted with Velan Engineering to perform testing to determine the thrust requirements associated with overcoming pressure locking of Velan flexible wedge gate valves. NRC requested a copy of the Velan report.

TVA RESPONSE Velan's testing is complete. The testing indicated an insignificant increase in thrust requirements due to pressure El-1

locking at the SON c oditions. At*.achment B contains a copy of Velan's report on esting.

NRC REQUEST SON's response to Question 2 of Reference 1 states that Boron Injection Tank Outlet Isolation Valves FCV-63-025 and

-026, will operate at locked rotor until the charging pumps develop full discharge pressure. NRC requested calculations to verify that adequate actuator capability (including thermal overload) exists at the locked rotor condition, to overcome pressure locking. NRC stated that this type of calculation has not been accepted in the past, but it would be considered if a significantly large margin in actuator capability exists.

TVA RESPONSE TVA has chosen not to pursue supporting operation of these motor-operated valves (MOVs) at locked rotor conditions for long-term pressure locking qualification. Accordingly, TVA will implement a design change to eliminate pressure locking concerns for these valves. This modification will be completed prior to startup from the Units 1 and 2 Cycle 9 refueling outages.

NRC REQUEST SON's Referenced 2 letter (Note 36 in Attachment 3) states that it was acceptable for actuators on Containment Spray Valves FCV-72-002 and -039, to operate at locked rotor until the containment spray pumpt develop full discharge pressure.

NRC stated that the calculations provided to address this issu.a showed less than an acceptable amount of margin for the long-term pressure locking corrective action.

TVA RESPONSE TVA determined that a design change is needed to comply with-long-term qualification requirements for GL 95-07. TVA will implement a design change for these valves prior to startup from the Units 1 and 2 Cycle 9 refueling outages. This will alleviate the pressure locking concerns of GL 95-07 for these valves.

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NRC REQUEST SON's Referenced 2 letter (Note 38 of Attachment 3) states that residual heat removal to Containment Spray Header Valves FCV-72-040 and -041, would be susceptible to pressure locking after securing shutdown cooling during startup. The analysis assumes that bonnet leakage, based on Commonwealth Edison leakage rates, will prevent valves from pressure locking.

NRC stated that the Commonwealth Edison leakage rates have not been accepted by the staff.

TVA RESPONSE Rather than attempting to quantify a aonnet leakage rate for these MOVs, TVA will implement a design change for these valves prior to startup from the Units 1 and 2 Cycle 9 refueling outages. This design change will alleviate the pressure locking concern for these valves.

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