ML20094G021

Forwards Response to NRC 951002 Ltr Re Violations Noted in Insp Repts 50-327/95-18 & 50-328/95-18.Util Denies Violation

ML20094G021
Person / Time
Site:	Sequoyah
Issue date:	10/31/1995
From:	Adney R TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9511090194
Download: ML20094G021 (5)

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Tennessee OaNoy Authority, Post' Omce Box 2000. Soddy-Daisy, Tennessee 37379-2000 ~ . '

i 2I gn , i RJ. Adney{

. , i Sne Vce Presdent U- '

s Sequoyah Nuclear Plant . ,-

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U.S. Nuclear Regulatory Commission : i e (ATTN: DocumentControlDesk~

1 Washington, D.C. 20555 3 .

-l Centlemen:  ;

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iIn the Matter of ) Docket Nos. 50-327

Tennessee Valley Authority )- 50-328 l 1

, .I E .SEQUOYAH NUCLEAR PLANT (SQN) - NRC INSPECTION REPORT NOS. 50-327, .i y; 328/95 REPLY TO NOTICE OF VIOLATION (NOV) 50-327,328/95-18-01 Enclosed is TVA's reply to Mark S. Lesser's letter to O. D. Kingsley, Jr., dated October 2, i 1995, which transmitted the subject NOV. This NOV pertains to corrective action -

associated with emergency core cooling system throttle valves.  !

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i  ; TVA denies that a violation occurred as stated in the NOV. The enclosure explains the

. reasons for TVA's denial. '

In addition, the discussion in Inspection Report 95-18 conceming this issue indicates a

' difference of opinion between NRC and TVA in the application of Generic Letter 91-18 and  :

v. ~ 10 CFR 50.59 when discrepancies between the plant and its licensing basis are identified.

TVA has requested a" meeting with NRC to resolve this difference ofopinion. We believe the resolution of this ; difference may affect the ultimate disisosition of this violation.

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? ,n: U.S. Nuclear Regulatory Commission :

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,  ? October"31, 1995- -

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If you have questions regarding this response, please telephone R. H. Shell at (423) 843-7170. .. l

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- Sincerely,; :

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- R. J. Adneyj -

' Enclosure cc (Enclosure)

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.Mr. D. E. LaBarge, Project Manager Nuclear Regulatory Commission -

g One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739

-NRC Resident Inspector -

Sequoyah Nuclear Plant

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' 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37379-3624 Regional Adnumstrator-U.S. Nuclear Regulatory Commission .

Region II 101 Marietta Street, NW, Suite 2900 l

- Atlanta, Georgia 30323-2711; 1

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ENCLOSURE:

. RESPONSE TO NRC INSPECTION REPORT- 1

' NOS. 50-327,328/95-18. _ . . _ _,

MARK S. LESSER'S LETTER TO OLIVER D. KINGSLEY, JR. i

, DATED OCTOBER 2,1995

--Violation 50-327f 328/95-18-01

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• 10,CFR 50, Appendix B, Criterion XVI requires, in part, that measures shall be established )

to ensure that conditions adverse to quality are promptly identified and corrected. j q

"CSntrary to the above, prompt corrective action was not implemented for a condition i-  : adverse to quality. Specifically, on July 18,1994, Westinghouse notified the licensee of an adverse condition involving accelerated degradation of Emergency Core Cooling System

' throttle valves during accident scenarios which could cause premature system pump failure, c and actions to correct or compensate for the condition were not implemented until July 17,

'1995. ]

I "This is a severity level IV violation (Supplement 1)."

Background Information ,

1 The subject issue involves a condition where throttle valves in the high head and I I

intermediate head safety injection portion of the emergency core cooling system may

~ degrade as a result of a high pressure drop across the valves during a loss of coolant accident (LOCA). This pressure drop is postulated to result in cavitation-induced erosion u of the throttle valve seats. Erosion of the valve seat could result in a loss of flow resistance which may allow the emergency core cooling system (ECCS) pumps to approach or exceed run-out flow within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> post-LOCA.

' The issue was originally' identified at Sequoyah Nuclear Plant (SQN) through the corrective  !

action program generic review of a Watts Bar Nuclear Plant (WBN) problem. During a

' design review of the WBN emergency core cooling system, the WBN intermediate and high head injection flow balance valves were determined to be globe valves which are not  ;

designed for flow balancing operation. A subsequent review of the valves at SQN confirmed these valves to be significantly different from the WBN valves. The SQN valves  ;

r 1 are throttle valves which are specifically designed for flow balancing operation. To

' demonstrate the suitability of the SQN valves, TVA performed a calculation utilizing the L methodology and acceptance criteria from Electric Power Research Institute (EPRI)  :

Standard NP-6516, " Guide for the Application and Use of Valves in Power Plant Systems."

This cilculation concluded that the SQN valves could be required to operate under flow conditions'which result in valve seat erosion.

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a At that time, Westinghouse was contacted to assist in the evaluation of the subject can6 tion .l o since the susceptible valves were within the scope of the equipment originally supplid by .  ;

~t he nuclear steam supply systems (NSSS) equipment vendor and were originally specified . j

.-by. Westinghouse before the EPRI standard was published. ,

. Westinghouse provided SQN with ajustification for continued operation which indicated j that the existing throttle valves will perform their function for a minimum of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> ]

: following a LOCA. : Westinghouse concluded that the intermediate and high-head injection j

pumps are not required to operate more than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> following a LOCA since the reactor i

- coolant system conditions are such that s' single RHR pump is sufficient for long-term

coolin'g. This evaluation assumed that the existing SQN emergency operating procedures - l would be in effect for accident mitigation and recovery. -!

1 As part of the closure process for the corrective action document, the Menagement Review  :

0  ; Committee (MRC) reviewed the issue in February 1995. He MRC directed that this issue  ;

i be captured in the Technical Support Center activation and operation procedure

(Emergency Plan Implementing Procedure [EPIP] 6). The MRC believed that this l procedure was the best place to remind plant personnel of the issue because the procedure l

would be in use if the potential degradation were to occur. The subject procedure was  !

[ revised on July 17,1995.  !

Oi Basis for Danimi of the Viniatinn I

- TVA does not dispute that it did not promptly respond to the MRC direction to revise the c Technical Support Center activation and operation procedure. However, TVA concluded in the Summer of 1994 and still concludes that based on the evaluation performed by

, _ Westinghouse, a revision to the procedure was not required for continued safe operation of

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! the plant. Consequently, it was not a required corrective action in the context of  :

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: 10 CFR 50, Appendix B, Criterion XVI. He subject procedure revision was merely an  !

i l enhancement to remind plant personnel of a potentia condition following a LOCA. This

[ position is backed by a revised Westinghouse evaluation which clarified that the original

. justification of continued operation was based upon accident mitigation and recovery utilizing the existing emergency procedures and that no supplemental procedure changes

. were necessanyi If the existing procedures were followed, RCS conditions would be such i 1 that operation of the intermediate and high-head ECCS pumps would be limited during the . l f.'  : time when significant erosion of the flow-balancing valves is postulated to occur. The plant

! emergency procedures'will ensure that sufficient RHR flow is available for long-term core kC  ; cooling.

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- In summary, because the existing plant emergency procedures would limit throttle valve seat erosion and the fact that the subject pumps would not be required to operate if the valve seats became eroded several days following a LOCA, no further corrective actions were needed. 'Ihe subsequent revision to EPIP-6 was an enhancement not a corrective action,

, As such, the timeliness ofits implementation should not be the basis of a violation.-

For these reasons, TVA denies this violation.

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