ML20059L868

Safety Evaluation Supporting Amends 146 & 127 to Licenses DPR-77 & DPR-79,respectively

ML20059L868
Person / Time
Site:	Sequoyah
Issue date:	09/21/1990
From:	Office of Nuclear Reactor Regulation
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ML20059L866	List: ML20059L864 ML20059L868
References
NUDOCS 9010020069
Download: ML20059L868 (4)

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ENCLOSURE 3 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION

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i SUPPORTING AMENDMENT NO.146 T0 FACILITY OPERATING LICENSE NO. DPR-77 AND AMENDhENT NO.127 TO FACILITY OPEPATING LICENSE NO. DPR-79 TENNESSEE VALLEY AUTHORITY SEQUO,AH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NOS. 50-3?7 AND 50-328 i

1.0 INTRODUCTION

By letter dated July 20, 1990, the Tennessee Valley Authority (TVA) proposed i

to modify the Sequoyah Nuclear Plant, Units 1 and 2, Technical Specifications (TSs). The proposed changes are to revise the Action Statement "c" for i

Limiting Condition for Operation (LCO) 3.9.2 on source range neutron flux monitors for refueling operations. This action statement would be revised to add a statement that the provisions of TS 3.0.4 are not a)plicable to LCO 3.9.2 for entry into flode 6, Refueling. TS 3.0.4 states that tie licensee may not have the reactor enter an operational mode or other specified condition unless the conditions for the LCOs.are met witt.out reliance on provisions contained in i

any action statements. This provision in TS 3.0.4 does not prevent passage through operational modes as required to comply with action statement require-i ments.

Exceptions in the TSs to TS 3.0.4 are stated in the individual specifi -

cations.

The licensee is proposing such an exception for LCO 3.9.2 to allow the reactor to enter the refueling mode without meeting LC0 3.9.2 (i.e.,

without having as a minimum two 'operabic source range monitors).

Refueling is-1 Operational tiede 6 with fuel in~ the reactor vessel and the reactor vessel head closure bolts kss then fully tensioned or the head reroved.

The source range nuclear instrumentation are part of the excore (i.e, outside i

the core) nuclear instrumentation read to measure the leakage neutron flux from the core. The source range channels measure the-lowest levels of the neutron-flux during shutdown and startup. ~ There is a reactor trip off the source range i

channels to prevent too rapid an increase in reactor power during startup;.

however, no credit is given for this trip in the accident analyses.in Chap-ter 15 of the.Sequoyah Final Safety Analysis Report. The intermediate range and power range instrumentation are to measure the next higher levels of the neutron flux.

Because of difficulties in the Unit 1 Cycle 4 refueling outage, TVA requested a waiver of compliance to allow linit I to enter Mode 6 without two operable source range monitors. This was requested in TVA's letter dated March 25, 1990. The staff granted this waiver of compliance on flarch 25, 1990 and documented its approval of the waiver of comoliance in a letter dated March 27,1990.

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j 2.0 EVALUATION i

in its application, TVA stated that during the Unit 1 Cycle 4 refueling outage-it noted that LCO 3.9.2 unduly restricted entry into Mode 6 when there were less than two operable source range neutron flux monitors.

TVA stated that the restriction on Mode 6 entry is' overly restrictive because LC0 3.9.2 contains action state'nents that address inoperable source range neutron flux instrumen-tation channels, and these action state'nents do not limit the amount of time that source range channels may be inoperable.

TVA concluded that entry into Mode 6, while relying on the action statements for inoperable source range channels for LCO 3.9.2, should provide an acceptable level of safety. TVA further stated that by letter dated March 26, 1990, it requested a temporary exemption to TS 3.0.4 as it applies to LC0 3.9.2 to allow Unit I to enter Mode 6 with less than two-operable source range channels and NRC approved this request in its letter dated March 27, 1990.

TVA stated that this TS change would permanently exempt the provisions of TS 3.0.4 from LC0 3.9.2 and remove unnecessary restrictions on entry into Pode 6 with less than two operable source range channels. TVA stated that the proposed exemption to TS 3.0.4 would remove this unnecessary restriction without reducing safety and prevent the possible need for any future expedited licensing action in this area. TVA concluded that the action stetements of LCO 3.9.2, in conjunction with the requirements in TS 3.9.1 on minimum boron concentrations in the reactor coolant system during Mode 6, provide positive controls over activities that affect core reactivity and ensure an acceptable margin of safety if there are less than two operable source range monitors.

l The current LC0 3.9.2 and TS 3.0.4 do not allcw a unit to enter Mode 6, Refueling, with less than two operable source range channels because TS 3.0.4 does not allow entry of a unit into an " operational mode" unless the conditions for all applicable LCOs are met without relying on provisions in the associated action statements.

By Table 1.1 of the TSs, the transition from Mode 5, Cold Shutdown, to Mode 6 occurs when the first closure bolt of the reactor vessel head is less than fully tensioned.

For configuration control purposes, the unit is declared by TVA to-be in Mode 6 when the hydraulics of the bolt detensioning tool on the closure bolts are activated.

TVA is proposing to have the provisions cf TS 3.0.4 not apply to LC0 3.9.2.

LCO 3.9.2 applies only for Mode 6 and requires that at least two' source range channels shall be operable and operating.

If only one channel is operating, the acticn statements for LCO 3.9.2 require that all operations involving core alterations or positive reactivity changes arc immediately suspended.

If i

there are no channels operating, the boron concentration of the reactor coolant system is measured at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to determine that it meets LC0 3.9.1.

These actions are sufficient to keep the reactor indefinitely in a safe condition with less than two source range channels and the reactor in l

Mode 6.

Because of this, there are no time restraints in the TSs on how long the unit may be in the action staterents for LCO 3.9.2.

Therefore, the proposed change to exempt LCO 3.9.2 from provisions of TS 3.0.4 is consistent with the guidance on TS 3.0.4 and LCOs in Generic Letter (GL) 87-09, " Sections

-3.0 and 4.0 of-the' Standard Technical. Specifications on the Applicability of I

Limiting conditions for Operation and Surveillance Requirements," dated June 4, I

.: 1987. The provisions of GL 87-09 are consistent with exempting LCOs as LCO 3.9.2 from TS 3.0.4.

Also, the proposed change is viewed as having no safety significance because the action statenents of LCO 3.9.2 will be complied with in Mode 6 to keep the reactor in a safe condition. Based on this, the staff concludes that the preposed change is acceptable.

2 3.0 ENVIRONMENTAL C0f!SIDERAT10N These amendments involve a change to..cy.' cement with respect to the installation or use of a facility compe sent located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendments involve no significant incr*ase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significent increase in individual or cumulative occupational radiation expo-sure. The Commission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public coment on such finding. Accordingly, the amendments acct the eligibil-itycriteriaforcategoricalexclusionsetforthin10CFR51.22(c)(9).

Pursuant to 10 CFR 51.22(b), no environmental impact statement nor environ-mental assessnent need be prepareci in connection with the issuance of. these amendments.

4.0 CONCLUSION

The Comission rade a proposed determination that the amendront involves no significant hazards consideration which was published in the Federal Register (55FR34382)onAugust 22, 1990 and consulted with the State of Tennessee.

No public comnie.nts were received and the State of Tennessee did not have any comments.

The staff has concludcd, based on the.onsiderations discussed above, that:

(1) there is reascnable assurance that the health and sr.fety of the will not be endangered by operation in the proposed manner, and_(2) public such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will' not be inimical to the comon i

-l defense-and security nor to the health and safety of the public.-

Principal Contributor:

J. Donohew Dated:

September 21, 1990 J