ML20101N052

Provides Response to NRC 960214 RAI Re Insp Repts 50-327/95-18 & 50-328/95-18,including Corrective Actions & Schedule for Resolution of Degraded Condition W/Eccs Throttle Valves

ML20101N052
Person / Time
Site:	Sequoyah
Issue date:	04/04/1996
From:	Adney R TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9604080210
Download: ML20101N052 (2)

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I Tennessee Valley Authority, Post Offico Box 2000, Soddy-Daisy, Tennessee 37379-2000 R.J. Adney Sao Vice President l Sequoyah Nuclear Plant April 4,1996 U.S. Nuclear Regulatory Commission A'ITN: Document Control Desk Washington, D.C. 20555 Gentlemen:

In the Matter of ) Docket Nos. 50-327 Tennessee Valley Authority ) 50-328 l

SEQUOYAH NUCLEAR PLANT (SQN) - NRC INSPECTION REPORT NOS. 50-327, 328/95 REPLY TO REQUEST FOR ADDITIONAL INFORMATION This letter provides TVA's reply to Mark S. Lesser's letter to O. D. Kingsley, Jr., dated l February 14,1996. Mr. Lesser's letter requested intended corrective actions and a schedule for l the resolution of a degraded condition with the emergency core cooling system (ECCS) l throttle valves and TVA's basis for concluding that the degraded condition is not a condition

! adverse to quality.

TVA's position that the potential erosion of the ECCS throttle valves is not an adverse l condition is based on previously-performed evaluations and analyses of the condition. The l issue of the potential inoperability of the ECCS throttle / balancing valves was initially identified at TVA's Watts Bar Nuclear Plant (WBN) and was documented by that plant in accordance with TVA's corrective action program. Through the generic review process, the WBN corrective action document was reviewed by SQN for applicability. Based on the l potential that the WBN identified condition could be applicable to SQN and under the guidance of the corrective action program, a problem evaluation report (PER) was initiated at SQN. SQN performed an operability evaluation of the condition under the guidance of Generic Letter 91-18. The evaluation determined that the condition met the operability requirements of ECCS (i.e., long-term core cooling); however, the system did not fully meet TVA's design qualifications. Based on this evaluation, it was determined that a condition adverse to quality did not exist (since the operability requirements of the system had been satisfied). The SQN PER was closed to the site issues list as a degraded condition that required a design change in order to achieve full design qualification.

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U.S. Nuclear Regulatory Commission ,

Page 2 April 4, 1996 I

The long-term action to be taken for the resolution of the degraded equipment condition is to implement a hardware modification. The hardware change is expected to consist of the installation of a pressure-reducing orifice assembly upstream of each throttle valve. This l modification would protect the valves from cavitation in the unlikely event of a large-break '

loss of coolant accident. The hardware modification will be implemented in accordance with  ;

the priority of all safety significant issues. 'Ihe hardware modification is currently projected for implementation during the Units I and 2 Cycle 9 refueling outages (Fall 1998 - Unit 1; Spring 1999 - Unit 2). i i

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

l l

l R. . A&q i

cc: Mr. D. E. LaBarge, Project Manager l Nuclear Regulatory Commission l One White Flint, North I 11555 Rockville Pike l Rockville, Maryland 20852-2739 l

NRC Resident Inspector Sequoyah Nuclear Plant l 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37379-3624 Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323-2711 1