ML20212Q719

Safety Evaluation Supporting Amend 27 to License NPF-18

ML20212Q719
Person / Time
Site:	LaSalle
Issue date:	08/29/1986
From:	Office of Nuclear Reactor Regulation
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ML20212Q713	List: ML20212Q709 ML20212Q715 ML20212Q719
References
NUDOCS 8609080018
Download: ML20212Q719 (3)

Text

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1. garg'og UNITED STATES

[ g NUCLEAR REGULATORY COMMISSION

, ji p WASHINGTON, D. C. 20555

\...../

SAFETY EVALUATION BY THE OFFICE OF NdCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 27 TO FACILITY OPERATING LICENSE NO. NPF-18 COMMONWEALTH EDISON COMPANY LA SALLE COUNTY STATION, UNIT 2 DOCKET NO. 50-374

1.0 INTRODUCTION

Item II.K.3.18, " Modification of Automatic Depressurization System logic -

Feasibility for Increased Diversity for Some Event Seauences" of NUREG-0737 .

required the licensee to modify the automatic denressurization system (ADS) actuation logic in order to eliminate the need for manual actuation to assure adequate core cooling. To ensure satisfactory resolution of the outstandino concern, la Salle Unit 2, Operating License No. NPF-18 contains License Condition P.C.(18)(d)(i), which requires modifications of the ADS.

By letters dated May 4.1981, and May 6,1981, Commonwealth Edison Company (CECO) endorsed the BVR Owner's Group study results as applicable to la Salle County Station and committed to implement ADS modifications recommended in the study. The loaic will be modified by either: (1) eliminating the high drywell pressure trip or (?) bypassing the high drywell pressure trip

, after runout of a timer started at the reactor vessel level 1. The staff l indicated that either of these modifications were acceptable. In Amendment 62 to the la Salle Final Safety Analysis Report, CECO opted to modify the ADS logic to bypass the high drywell pressure trip after a sustained low

, water level signal; and to add a manual switch which may be used to inhibit the ADS action, if necessary. By letter dated July 3, 1986, CECO provided a description of the logic modifications and elementary diaarams of the modified ADS actuation circuitry and requestec' a revision to the technical specifications which reflects the change to the ADS logic.

The automatic deoressurization system, through seven safety / relief valves, functions as a backup to the operation of the high pressure coolant systems by depressurizing the reactor vessel so that the low pressure systems may inject water for core cooling. The present ADS design is activated auto-matica11y upon coincident signals of low reactor water level, high drywell pressure and low pressure emeraency core cooling system (ECCS) pumps runnino. A time delay of approximately 2 minutes after receipt of these signals allows time for the water level to be restored by the hiah pressure coolant systems prior to autcmatic blowdown. For transient events which do not directly produce a high drywell pressure sianal and are further degraded by a loss of all high pressure coolant systems, adequate core cooling is assured by manual depressurization of the reactor vessel.

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5 2.0 EVALUATION In order to eliminate the need for manual ADS actuation to ensure adequate com .

cooling.'the ligensee has provided four bypass timers which will automatically bypass the four drywell high pressure initiation signals after a g.5 minute time delay. Each time delay is activated on its corresponding level 1 initiation signal. An alam is provided in the control room to indicate that the bypass logic has been activated. After the 9.5 minutes have elapsed, the high drywell pressure is no longer required for ADS actuation and the 105 second ADS actua-

' tion ti.ner is initiated. Another alam indicates that this timer has started.

After this time delay, the ADS solenoids are energized provided that at least one low pressure pump in that division is operating. The 105 second timer allows the operator to manually inhibit ADS actuation if desind. The sum of the time delays associated with the ADS actuation timer and the drywell pressure bypass timer is less than or equal to 687 seconds (9.5 minutes +

117 seconds allowable value for the ADS initiation timer). The bypass timers automatically reset when the low water level signal clears or the reset button is depressed. The settings for the pressure bypass timers are desemined based upon minimizing the operator actions related to the ADS logic, minimizing the chance for unintentional ADS. and limiting the impacc on the design basis ECCS analyses. In addition, a manual inhibit switch is also included to allow the operator to inhibit ADS operation without repeatedly pressing the iPeset push-button. An indicating light and an annunciator alert the operator of the in-3 hibit condition. The pressure relief function and the manual ADS or individual safety relief valve control is not affected by this manual inhibit switch, i This modification also allows the operator to manually initiate ADS without i the low pressure ECCS pumps in that division operating. This i

flexibility in the use of the Emergency Operating ProceduresE0P) (provides additional where the operator, for example, is instructed to perfom an " emergency depressurization" t

to prevent containment damage. The seal-in feature has also been revised such that the seal-in occurs only if the final relays which energize the ADS solencias are actually energized. This eliminates the possibility of inadvertent

&gressurization of the reactor pressure vessel if a low pressure ECCS pump is

narted end a previous seal-in has not been reset. i a

'.he licensee proposed a revision to the Technical Specifications Tables 3.3.3-1, 3.3.3-2 and 4.3.3.1-1 to add drywell pressure bypass timers and man-

ual inhibit switches. The inscription of ' ADS Timer' in these tables is changed to ' Initiation Timer.' Since Specification 3.3.3 is concerned with the instrumentation which actuates the ADS system and not the ADS valves, the word " valve" is changed to " trip system" in ACTION 34 of Specification Table 3.3.3-1. To clarify the distinction between ADS valve (s) and ADS trip system.

foot note ** has been adoed to Specification 3.5.1 to refer to Technical i Specification 3.3.3 if an ADS trip system is inoperable. The staff has reviewed the licensee's submittal and concludes that the LaSalle Unit 2 ADS design

confo ms to the requirements of TMI Action Plan Item II.K.3.18 regarding ADS automatic actuation to ensure adequate core cooling and is, therefore. -

acceptable. The staff has also reviewed the licensee's proposed Technical Specification changes and finds that they appropriately address the actuation i

instrusarntation setpoints and surveillance requirements for the changes made

to the ADS logic and are, therefore.. acceptable. Since the logic requireo by ,

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4 these proposed changes is not yet installed for Unit 2, the request that these Technical Specification changes not be made effective until the first refueling outage should be oranted. This effective date is,.also, con-sistent with the License Condition 2.C.(18)(d)(1).

3.0 ENVIRONMENTAL CONSIDERATION

This amendment involves a change in the installation and use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes in surveillance requirements. The staff has dete; mined that this amendment involves no significant increase in the amounts, and no significant change in the types,.of any effluents that may be released offsite, and that there is no significant increase in individual or cumula-tive occupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding. Accord-ingly, this amendment meets the elioibility criteria for categorical exclusionsetforthin10CFR51.22(c)(9). Pursuant to 10 CFR 51.22(b),

no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.

4.0 CONCLUSION

The Commission rade a proposed determination that the amendment involves no significant hazards consideration which was published in the Federal l

Register (51 FR 27280) on Wednesday, July 30, 1986, and consulted with the

state of Illinois. No public comments were received, and the state of Illinois did not have any comments.

The staff has concluded, based on the considerations discussed above, that:

(1) there is reasonable assurance that the health and safety of the public will not be endancered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regula-tions and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributor: A. Bournia, BWR Project Directorate No. 3, DBL l

Dated: August 29, 1986

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