ML20215C272
| ML20215C272 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/05/1986 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| TVA-SQN-TS-72, NUDOCS 8612150085 | |
| Download: ML20215C272 (3) | |
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-TENNESSEE VALLEY AUTHORITY CHATTANOOGA, TENNESSEE 37401 SN 157B' Lookout Place
't DEC05 996 TVA-SQN-TS-72' Director of Nuclear Reactor Regulation Attention: - Mr. B.. Youngblood, Project Director -
'PWR Project Directorate No. 4 Division of Pressurized Water Reactors (FWR)
Licensing A i
U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Youngblood:
In the Matter of
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Docket Nos. 50-327
[
. Tennessee Valley Authority
)
50-328 e
SEQUOYAH NUCLEAR PLANT - NOLDED CASE CIRCUIT BREAKERS - TECHNICAL
' SPECIFICATION CHANGE 72 On August 8', 1986 we submitted a requested amendment to Licenses DPR-77 and DPR-79 to change the technical specifications of Sequoyah Nuclear Plant units 1 and.2.
The proposed change clarified TVA's interpretation for testing of molded case circuit breakers and removed surveillance requirements 4.8.3.1.a.1.a. 4.8.3.1.a.1.b, 4.8.3.1.a.1.c, 4.8.3.1.a.2, 4.8.3.1.a.3, and 4.8.3.1'.b.'
Specifically, the proposed change deleted testing of the instantaneous trip function of the molded case circuit breakers.
The requested amendment was motivated by observed degradation in the breeker i'
- contacts due to testing conducted in the instantaneous trip current range performed with circuit breakers at.Sequoyah.
In addition, the General Electric Company, a manufacturer of circuit breakers, has stated that subjecting circuit breakers to currents sufficiently large enough to test the
'instantaneou's trip function will cause degradation of the breaker contacts, thereby reducing useful breaker life. They have further stated that there are no known risks to not testing the instantaneous trip function of these breakers. We have, however, initiated preparations to perform instantaneous trip testing of the molded case circuit breakers at Sequoyah, since neither TVA nor molded case circuit breaker vendors have been able to quantify the degradation;'that is, identify the number of instantaneous trips that may occur before the useful life of the breaker is expended.
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. q EC O S E86 Director of Nuclear Reactor Regulation During telephone. calls held on October 16 and October 22,.1986, with T. Alexion and P. Gill of.your' staff, we proposed the following technical specification. interpretation:
1.
Thermal Trio Function: Test the thermal trip function of all molded case circuit breakers.
2.s Instantaneous Trio Function:
Test the instantaneous trip function of 2RAE those molded case circuit' breakers whose faulted currents are f
determined to exceed the thermal trip range of the respective molded case
. circuit breakers.
This proposed technical. specification interpretation provides for a minimum number of molded case circuit breakers to be exposed to potontially damaging current levels. Based on NRC's willingness to review a submittal on this approach, which was expressed during the_ telephone calls identified above, we have begun performing.the necessary engineering calculations to support our proposed technical specification interpretation.
Our submittal will segregate the molded case' circuit breakers by protection function:
1..
Containment Penetrations: The faulted current will be taken at the load; the calculation of faulted current seen at the circuit breaker will take credit for impedance of the 1E cabling from the point of the fault to the
-circuit breaker.
2.
Non-1E Loads Off of IE Boards:
The faulted current will be taken at the furthest extent from the molded case circuit breakers that the associated 1
1E cabling and equipment will allow.
The planned submittal will include typical calculations for molded case circuit breakers that perform each of the two protectitn functions identified above._ Also, a tabulation of the required testing (thermal trip testing only or both thermal and instantaneous trip testing) will be provided.
We are pleased that your staff has expressed a willingness to consider the technical specification interpretation identified in this letter. We plan to provide a submittal of the resulting evaluations, including sample calculations and a tabular summary of all results, for your review by December 12, 1986.
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-. DEC 0 51996 Director of Nuclear Reactor Regulation
~ Please direct questions'you may have concerning this issue to Timothy S. Andreychek at (615) 870-7470.
Very truly yours, TENNESSEE V LEY AUTHORITY
-s-R.
idley, Dir ctor P
Nuclear Safety nd Licensing Sworn to and subscribg before me thi d"/A day of A/dd, 1986 fM
' Notary Public My Cormaission Expires I
i ec:
U.S. Nuclear Regulatory Commission Region II-
' Attn:
.Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. Carl St'ahle Sequoyah Project Manager U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20814 Mr. G. G. Zech Director, TVA Projects U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. Michael H. Mobley, Director Division of Radiological Haalth T.E.R.R.A. Building 150 9th Avenue North Nashville, Tennessee 37203
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