ML20073T316

Safety Evaluation Supporting Amends 28 & 17 to Licenses DPR-77 & DPR-79,respectively

ML20073T316
Person / Time
Site:	Sequoyah
Issue date:	05/03/1983
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20073T315	List: ML20073T314 ML20073T316 ML20073T319
References
TAC-51383, TAC-51384, NUDOCS 8305110250
Download: ML20073T316 (3)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AHENDHENT NO. 28 TO FACILITY OPERATING LICENSE DPR-77 AND AMENDHENT NO. 17 TO FACILITY OPERATING LICENSE OPR-79 TENNESSEE VALLEY AUTHORITY INTRODUCTION In a submittal dated March 28, 1983, Tennessee Valley Authority (TVA) submitted a f

proposed Technical Specification change for the Upper Head Injection (UHI) accumu-lator water level setpoint and tolerances. The accumulators are presently required to isolate at 103.4 0.5 inches above the tank vendor working line. During an 18-month surveillance required by the Sequoyah Technical Specifications, the inability to remain witnin this setpoint and tolerance was initially discovered.

For the interim period of time until resolution of the situation, TVA has adhered to a 30-day surveillance period to ensure that the accumulator water level would be within Technical Specification limits. TVA has been unable to comply with the accumulator water level Technical Specification requiring TVA to recalibrate the satpoint every 30 days. TVA has applied a Westinghouse evaluation to justify changing Technical Specification 4.5.1.2.c setpoint and tolerance to 87.1 S.6 inches.

EVALUATION t

The licensee considers the setpoint and tolerance on the accumulator water level unnecessarily restrictive for safe plant operation. TVA has provided an assessment (Ref.1) which supports changing the water level setpoint to 82.1 inches above the i

tank vendor working line (87.1 inches after correction of mass of cover gas) with a tolerance of 5.6 inches. The proposed setpoint and tolerance conesponds to an 3

increased allowable water delivery from the accumulator of 50 ft.

Two sets of calculations were discussed in Reference 1.

The first set (using the 1978 UHI model (Ref. 2)) was performed for the limiting break with perfect and imperfect mixing assumptions in the upper head. TVA has shown previously (Ref. 3) that minimizing the amount of water delivered to the upper head is conservative for imperfect mixing, and maximizing the delivered UHI water is conservative for i

perfect mixing. Themfore, both cases need to be assessed to determine an allowable setpoint and tolerance. A summary of the worst case results follows:

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Table 1 Worst Case Sequoyah ECCS Performance with the 1978 model l

Hixing Volume of UHI3 Break Hodel Delivered (ft )

Fn PCT ('F) l O.6 DECLG Imperfect 900 2.237 2200 0.6 DECLG Perfect 1053 2.32 2111 Since the imperfect mixing case is alrea$ at the 10 CFR 50.46 limit of 2200"F, i

only the perfect mixing case can be adjusted to increase the water volume and, thus, increase the tolerance. Based on previous analyses, the sensitivity of peak clad-ding temperature (PCT) to volume of UHI water delivered (Ref. 3), change in F (Ref. 4), and reduction in pellet tenperature uncertainty (Ref. 5) has been d0ter-mi ned. By applying the results of these sensitivity studies, the licensee estimated that the rgt effect on PCT would be neagly zero if the delivered water was increased i

to 1105 ft (an ine.rease of about 50 ft ) and the F was reduced to the 2.237 value used for imperfect mixing. The second set of,calcuIations discussed used the 1981 model revisions appropriate for UHI plants (Ref. 6) with the following results:

Table 2 i

Worst Case Sequoyah ECCS Performance with the 1981 model Hixing Volume of UH13 Break Hodel Delivered (ft )

Fn PCT ('F)

J 0.8 DECLG Imperfect 900 2.237 2147 0.8 DECLG Perfect 1049 2.237 1982 t

Applying the same sensitivity factors of Ref. 3 thru 5 to the results using the 1981 model, shows that even more margin exists for increasing the level setpoint and toler-ance than was the case for the 1978 model. This method of applying sensitivity factors has been used for ECCS assessment on several cases for steam generator tube i

plugging and cladding swelling and rupture. For the Sequoyah application, the sensi-tivity factors are applied over a narrow temperature range and are well established.

Af ter applying the sensitivity factors to the calculated resultg, the peak cladding temperature would still be below the 10 CFR 50.46 limit of 2200'F. The staff. there-i fore, finds the licensee's justification for expanding the UH1 volumetric delivery limits to be acceptable, and therefore finds the proposed amendment acceptable.

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, l ENVIRONMENTAL CONSIDERATION We have determined that the amendr.ents do not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any signif-icant environrental impact. Having made this determination, we have further con-cluded that the amendments involve an action which is insignificant from the stand-point of environnental inpact and, pursuant to 10 CFR 51.5(d)(4), that an environ-mental inpact statement or negative declaration and environnental impact appraisal need not be prepared in connection with the issuance of these amendients.

CONCLUSION We have concluded, based on the considerations discussed above, that: (1) because the anendments do not involve a significant increase in the probability or con-sequences of accidents previously considered, do not create the possibility of an accident of a type different from any evaluated previously, and do not involve a significant decrease in a safety nargin, the amendments do not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in coupliance with the Commission's regulations and the issuance of these anendments will not be inimical to the comon defense and security or to the health and safety of the public.

REFERENCES:

1.

Letter from L. H. !! ills (TVA) to E. Adensam (NRC) dated March 28, 1983.

2.

WCAP-8479 (Rev. 2) " Westinghouse Energency Core Cooling System Evaluation Itodel Application to Plants Equipped with Upper Head Injection," November 1977.

3.

Telecopy from TVA dated 4-25-83.

4.

Sequoyah Final Safety Analysis Report dated February 1974 and subsequent amendments.

5.

WCAP-9180, " Consideration of Uncertainties in the Specification of Core Hot Channel Factor Limits," September 1977, (WCAP-9181 Nonproprietary).

6.

WCAP-9220-p-A Rev.1. " Westinghouse ECCS Evaluation flodel 1981 Version,"

Appendix B, February 1982, (WCAP-9221-A Nonproprietary).

Date: May 3, 1983 Principal Contributors: Norman Lauben, Reactor Systems Branch, DSI Itelanie Miller, Licensing Branch No. 4, DL Carl Stahle, Licensing Branch No. 4, DL

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