ML20196D412

Discusses 981110 Request Re Noed.Based on NRC Evaluation, Staff Concluded That NOED Warranted.Nrc Intends to Exercise Discretion Not to Enforce Compliance with TS 3.8.2.1,action B,For Period from 981110-12,at Stated Times

ML20196D412
Person / Time
Site:	Sequoyah
Issue date:	11/13/1998
From:	Reyes L NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:	Scalice J TENNESSEE VALLEY AUTHORITY
References
NOED-98-02-002, NOED-98-2-2, NUDOCS 9812020228
Download: ML20196D412 (5)

Text

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November 13, 1998 NOED No. 98-2-002- Y Tennessee Valley Authority ATTN: Mr. J. A. Scalice Chief Nuclear Officer and Executive Vice President 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801

SUBJECT:

~ NOTICE OF ENFORCEMENT DISCRETION FOR TENNESSEE VALLEY AUTHORITY REGARDING SEQUOYAH NUCLEAR PLANT UNIT 2

Dear Mr. Scalice:

By letter dated November 10,1998, you requested that the Nuclear Regulatory Commission (NRC) exercise discretion not to enforce compliance with the actions required in Unit 2 Technical Specification (TS) 3.8.2.1, Action b, which requires the return of the 120-VAC Vital Instrument Board 1-IV to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after failure of the 1-IV Vital Inverter.

That letter documented information previously discussed with the NRC in a telephone conversation on November 10,1998 at 9:30 a.m. You stated that on November 10,1998 at approximately 11:39 a.m. Unit 2 would not be in compliance with TS 3.8.2.1, Action b, which would require initiation of a shutdown and that the unit be in Cold Shutdown by 11:39 p.m. on November 11,1998. This Action Statement was entered on November 9,1998, at 11:39 a.m.

You requested that a Notice of Enforcement Discretion (NOED) be issued pursuant to the NRC's policy regarding exercise of discretion for an operating facility, set out in Section Vll.c, of the " General Statement of Policy and Procedures for NRC Enforcement Actions" (Enforcement Policy), NUREG-1600, and be effective for the period from 11:39 a.m., on November 10,1998

. to 11:39 a.m. on November 12,1998.

This condition was the result of the failure of the 1-IV 120-Vital Inverter, which led to the loss of power to the 1-IV 120-VAC Vital instrument Power Board, resulting in an immediate Unit 1 reactor trip from the reactor trip system instrumentation. At the time of the board failure, one )

channel of the power range instrumentation and the associated overpower delta temperature a function was tripped for testing. As a result of the board failure, another channel of this instrumentation conservatively failed to the trip condition and completed the two of four logic for initiation of a reactor trip. You stated that your root cause evaluations identified defective firing circuits in the bridge of the inverter as the probable cause of the event. The circuits were replaced,' the inverter and associated power board were retumed to service, and systematic circuit evaluation continued. You requested an additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the expiration of the 24-hour repair action of TS 3.8.2.1, Action b, to complete the testing of the Vital Inverter after

the circuit replacement to ensure operability.

9812O20228 981113 P yDR ADOCK 05000328 PDR (f lb

TVA 2 You provided as your safety rationale for issuing the NOED that Unit 2 does not have safety-related loads fed from the 120-VAC Vital Instrument Power Board 1-IV. One Unit 2 and some common non-safety related loads that affect Unit 2 were identified. However, those loads do not support required safety functions. Specifically, those loads included functions associated with the fuel oil, condenser circulating water, component cooling water, essential raw cooling water, waste disposal, control air, and emergency gas treatment systems. The functions served in these systems are primarily indication and alarm. The results of your probabilistic safety assessment indicated that the extension request would not change core damage frequency or large early release frequency.

In addition, you stated that requiring a shutdown of Unit 2 for this condition would involve the completion of actions that could challenge the safety system unnecessarily. Maintaining Unit 2 in a steady-state condition at power is less likely to result in a transient that could require safety system actuation.

You stated that compensatory measures would include the restriction of access to the ,

switchyard, relay room, emergency diesel generators, and the vital battery rooms. The l compensatory measures provided additional assurance by use of physical barriers, signs, and '

I control of access by the Operations group such that other critical systems are not impacted and enhance the availability of the offsite and emergency power supplies to plant systems.

The staff has reviewed the above rationale regarding the 1-IV Vital Inverter and the results of i your probabilistic safety assessment. In addition, your compensatory measures provide the appropriate justification to support a conclusion that enforcement discretion should be given to avoid undesirable transients as a result of forcing compliance with the TS, and would thus minimize potential safety consequences and operatlonal risks.  ;

l On the basis of the staff's evaluation of your request, including the compensatory measures  !

described above, the staff concluded that an NOED was warranted because we were clearly 1 satisfied that this action involved minimal or no safety impact and had no adverse radiological ,

impact on public health and safety. Therefore, it was our intention to exercise discretion not to j enforce compliance with TS 3.8.2.1, Action b, for the period from 11:39 a.m., on November 10, j 1998 until 11:39 a.m. on November 12,1998. However, this enforcement discretion was contingent upon the continued belief that the root cause of the 1-IV Vital Inverter problem was associated with a component failure in the bridge circuit. If, during the additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of enforcement discretion, you found that the root cause was other than a component failure in the bridge circuit, or a new problem was identified during testing that would require the 1-IV Vital Inverter to be declared inoperable, this enforcement discretion would have been terminated, after which you must have immediately complied with Action b of TS3.8.2.1. This letter documents our telephone conversation of November 10,1998 at 9:30 a.m., when we orally granted this notice of enforcement discretion.

I

s TVA 3 We understand that the condition causing the request for this NOED was resolved and that the 120-VAC Vital Instrument Board 1 IV was returned to operable status before plant shutdown was required and that the NRC-approved discretionary enforcement was not invoked.

Sincerely, Luis A. Reyes Regional Ad ini rator Docket No.: 50-328 License No.: DPR-79 cc: Senior Vice President Nuclear Operations Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Jack A. Bailey, Vice President Engineering and Technical Services Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Masoud Bajestani Site Vice President Sequoyah Nuclear Plant Tennessee Valley Authority P. O. Box 2000 Soddy-Daisy, TN 37379 General Counsel Tennessee Valley Authority ET 10H 400 West Summit Hill Drive Knoxville, TN 37902 cc cont'd: (See Page 4)

WA 4 i

.. cc: Continued Raul R. Baron, General Manager Nuclear Assurance Tennessee Valley Authority SM Lookout Place 1101 Market Street .

Chattanooga, TN 37402-2801 Mark J. Burzynski, Manager

' Nuclear Licensing Tennessee Valley Authority ,

4X Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801 J Pedro Salas, Manager ,

Licensing and industry Affairs '

Sequoyah Nuclear Plant -

Tennessee Valley Authority P. O. Box 2000 Soddy-Daisy, TN 37379

.J. T. Herron, Plant Manager Sequoyah. Nuclear Plant Tennessee Valley Authority l P. O. Box 2000 Soddy Daisy, TN 37379 4 l

Michael H. Mobley, Director Division of Radiological Health '

TN Dept, of Environment and Conservation 3rd Floor, LNC Annex  ;

401 Church Street '

Nashville, TN 37243-1532  !

- County Executive Hamilton County Courthouse Chattanooga, TN 37402-2801 Distribution:

L. R. Plisco, Ril

. H. Christensen, Ril i

' P. A. Taylor, Rll R. W. Heman, NRR

. F. Hebdon, NRR .

i Distrib'ution cont'd: (See Page 5) l

. . . - .. -. . ~.- . . .

f TVA. 5 Distribution: Continued W. C. Bearden, Rll

' C. F. Smith, Ril E. D. Testa, Rll' D. H. Thompson, Ril L. S. Mellen, Ril PUBLIC NRC Resident inspector, Operations U. S. Nuclear Regulatory Commission i 1260 Nuclear Plant Road Spring City, TN 37381 i NRC Resident inspector

- Sequoyah Nuclear Plant j

U. S. Nuclear Regulatory Commission '

2600 Igou Ferry Road Soddy-Daisy, TN 37379 i

i I

l OFFICE Ril:DRP Ril:DRP NRR:HQ , 3 Rit:DRP /\

SIGNATURE ggC y p p vsig{ '

(( A NAME, RPCarrion:dka HOChnstensen FJHebdon(p%' CACasto (/ g DATE 3 3 /98 31/ p 11/ 13 /98 11(5198 11/ 'J 198 11/ /98 11/ /98 COPY? f YES) NO )fES/ NO YES NO YES mo YES NO YES NO YES NO (PPICIAL RECORD CUPY DOCUMENT NAME: P:\NOEDLTRI.WPD L