ML20057A235
| ML20057A235 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 09/08/1993 |
| From: | Fenech R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-008, IEB-88-8, NUDOCS 9309130256 | |
| Download: ML20057A235 (4) | |
Text
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y Tennesses Vaney AuMorf?y. Post Othce Bor 2300, Soddy Daisy Tennessee 37379-2000
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Robert A. Fenech Vce President, Searyae. Nucleae Plant t
f September 8, 1993 U.S. Nuclear Regulatory Commission ATTN: Doc e nt Control Desk Washington, D.C. 20555 Gentlemen:
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In the Matter of
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Docket Nos. 50-327 i
Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - NRC BULLETIN NO. 88-08, THERMAL STRESSES IN PIPING CONNECTED TO REACTOR C001 ANT SYSTEMS (RCSs) -
References:
1.
NRC letter to TVA dated. September 16, 1991, "NRC Bulletin 88-08, ' Thermal Stresses in Piping Connected to Reactor Coolant Systems' - Sequoyah Nuclear Plant, Units 1 and 2-(TAC Nos. 69686 and 69687)"
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IVA letter to NRC dated October 27, 1989, "Sequoyah-F Nuclear Plant (SQN) - NRC Bulletin 88-08, Supplement 3,
' Thermal Stresses in Piping Connected to Reactor Coolant Systems'"
3.
TVA letter to NRC dated October 3, 1989 "Sequoyah
. Nuclear Plant (SQN) - NRC Bulletin 88-08, Thermal Stresses in Piping Connected to Reactor Coolant Systems" 4.
TVA letter to NRC' dated May 5, 1989,."Sequoyah Nuclear Plant (SQN) Unit 2 - NRC Bulletin 88-08, Thermal i
Stresses in Piping Connected to Reactor Coolant Systems:
.i (RCSs)"
5.
TVA letter to NRC dated April 18, 1989, "Sequoyah
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Nuclear Plant (SQN) - NRC Bulletin 88-08, Thermal Stresses in Piping Connected to Reactor Coolant Systems"
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U.S. Nuclear Regulatory Commission Page 2 September 8, 1993 6.
TVA letter to NRC dated January 10, 1989, "Sequoyah Nuclear Plant (SQN) - NRC Bulletin 88-08, Thermal Stresses in Piping Connected to Reactor Coolant Systems" 7.
IVA letter to NRC dated September 19, 1988, "Sequoyah Nuclear Plant (SQN) Unit 1 - NRC Bulletin 88-08, Thermal Stresses in Piping Connected to Reactor Coolant Systems" 8.
7VA letter to NRC dated August 24, 1988, "Sequoyah nuclear Plant (SQN) - NRC Bulletin 88-08, Thermal Stresses in Piping Connected to Reactor Coolant Systems" l
References 2 through 8 provided TVA's response to the subject NRC bulletin and its supplements. Reference 1 provided NRC's closure of the issue for SQN and also contained evaluation criteria to provide assurance that piping connected to the RCS will not be subjected to thermal stratification and thermal cycling. Based upon this evaluation criteria, J
SQN contracted for an independent audit to ensure present and future
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compliance with the subject bulletin requirements.
As a result of the audit. TVA identified a location where the piping configuration is similar to the piping geometry identified in Supplement 1 of the subject bulletin. Specifically, the area where the alternate charging line connects to the No. 4 cold leg of the RCS was identified to be potentially susceptible to thernal stratification.
Presently, this area is contained in the Augmented section of the In-Service Inspection Program and is scheduled to be examined every other refueling outage. Recent inspections revealed there were no indications of cracking. Additionally, the normal charging line geometry is not susceptible to the problem described in the subject bulletin; therefore, to ensure that thermal stratification does not take place in the alternate charging line, the function of each line is being reversed. By implementing this modification, normal flow will be provided through the alternate charging line eliminating the chance of thermal stratification. This modification will be implemented before restart from the Unit 1 Cycle 6 refueling outage.
The Unit 2 modification has been completed.
In Reference 3, credit was taken for the double isolation provided at the inlet to the centrifugal charging pump injection tank (CCPIT) to prevent the slow ingress of cold water into the RCS. However, the CCPIT inlet valves began leaking at the start of Cycle 6 operation for Unit 2.
This condition is documented in the SQN Corrective Action Program. These valves are currently scheduled to be repaired during the Unit 2 Cycle 6 outage. To allow interim operation during the remainder of the Unit 2 Cycle 6 operation, SQN Nuclear Engineering has performed an analysis of this condition. The analysis stipulates that a maximum leakage rate of 0.15 gallons per minute through the CCPIT is acceptable during the remainder of the Unit 2 Cycle 6 operation.
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U.S. Nuclear Regulatory Commission i
Page 3 September 8, 1993 l
The attached enclosure provides a description of the commitment made in this letter.
If you have any questions concerning the enciesed information, please contact W. C. Ludwig at (615) 843-7460.
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Sincerely, f
- ' =A Robert A. Fenech l
Enclosure
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Mr. D. E. LaBarge, Project Manager U.S. Nuclear Regulatory Commission One White' Flint, North i
11555 Rockville Pike Rockville, Maryland 20852-2739 i
NRC Resident Inspector Sequoyah Nuclear Plant 3
2600 Igou Ferry. Road i
Soddy-Daisy,. Tennessee 37379-3624 Regional Administrator U.S. Nuclear Regulatory Commission j
Region 11
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101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323-0199
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D4 CLOSURE Commitment The function of the normal and/or alternate charging line will be reversed before restart from the Unit 1 Cycle 6 refueling outage.
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