ML20212D557
| ML20212D557 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/29/1986 |
| From: | Domer J TENNESSEE VALLEY AUTHORITY |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| TVA-SQN-TS-72, NUDOCS 8701020068 | |
| Download: ML20212D557 (3) | |
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TENNESSEE VALLEY AUTHORITY 0
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DEC 29 986
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T w SqN-TS-7 Direater of Ihselaar Reactor Regulation Attention: IIr. -3. Youngblood, Project Director
.PtB Project Directorate No. 4 Division of Pressurised Water Reactors (PWR)
Licensing A
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- U.84-gueleer Regulatory Consnission Washington, D.C.
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Dear IIr. Youngblood:
In the IIstter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 58000YAN NUCLEAR PLAll? - IIDLDED CASE CIRCUIT BREAKERS - TECHNICAL SPBCIPICATICIf INTERPRETATIOIf 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 of the need for i
testing of molded case etreuit breekers 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 a
'4.8.3.1.b.
Specifically, the proposed change deleted testing of the instantaneous trip function of~the molded case circuit breakers.
Your letter dated November 7, 1986 advised us of NRC's denial of this requested license amendment.
i During telephone calls held on October 16, 1986 and October 22, 1986, with T. Alexion and P. Gill of your staff, we proposed the following technical specification interpretation for trip function testing of molded case circuit breakers 1.
Overeurrent Trio (Thermal) Punction Test the thermal trip function of those molded case circuit breakers whose design includes a ther.nal trip element. Other overload trip functions will be tested as per the manufacturer's recommendations.
2.
Instantaneous Trio Function: Test the instantaneous trip function of gnly those molded case circuit breakers whose maximum calculated fault currents are determined to exceed the overcurrent trip range of the roupactive molded case circuit breakers and whose instantaneous trip function is a separate and distinct trip function from the overcurrent trip function.
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< This' proposed technical specification interpretation, which we described to you ~ in R._ L. Gridley's December 5,1986 letter, providos. for a minimum number of molded-case circuit breakers to be exposed to potentially degrading. test current levels. Based on NRC's willingness to review a
'submittel on this approach, which was expressed during the telephone calls identified above, we have performed the necessary engineering calculations that.we' would use to support our proposed technical specification interpretation.
O-Those calculations identified a smaller number of molded case circuit breakers..for.which testing in the overcurrent trip range could be avoided, than was-originally thought could be demonstrated by analyses.
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To minimize administrative details associated with segregating such a small number of breakers from the test program, all breakers provided
'with separate overcurrent and instantaneous trip features will be tested to verify operability of both features. Other breakers will be tested to ensure their designed trip functions are operable..This test program is l currently underway.
- The calculations that were performed used extremely conservative guidelines. Impedances of relays, switches, indicating lights, and internal board wiring were neglected.
The minimum cable length required to limit the fault current to the overcurrent trip point limits was
! calculated using standard accepted methods. This calculated cable length wac compared to the straight-line distance from the power source to the
. penetration as determined.from design drawings.
If the minimum straight-line distance exceeded the calculated minimum cable length, the b.
= fault current was taken to lue within the thermal trip range of the molded caseicircuit breaker.
This conservative approach was taken, in part, due to resource constraints within TVA. As additional resources become available, we will reevaluate the merits of pursuing this technical specification i
interpretation with NRC.
We are pleased that your staff has expressed a willingness to consider this proposed technical specification i.
interpretation,. and will advise you within six months af ter restart of Sequoyah unit 2.of our intent with respect to this issue.
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b Director of Nuclear Reactor Regulation DEC'20 m
' Please-direct. questions you may have concerning this issue to Timothy S.
Andreychek:st (615) 810-7470.
Very truly yours, TENNESCE VALLEY AUTHORITY y-~
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J. A.'Domer, Assistant Director
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cc:
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Nuclear Regulatory Comission Region II Attn:
.Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. - Michael H. Mobley, Director (w/o Enclosures)
Division of Radiological Health T.E.R.R.A. Building 150 9th Avenue North Nashville, Tennessee 37203 Mr. Carl Stahle Sequoyah Project Manager U.S. Nuclear Regulatory Comission 7920 Norfolk Avenue Bethesda, Maryland 20814 Mr. G. G. Zech, Director TVA Projects U.S. Nuclear Regulatory Comission Eegion II 101 Mcrietta Street, NW, Suite'2900 Atlanta, Georgia 30323