ML20213G635

Safety Evaluation Supporting Amends 104 & 94 to Licenses DPR-39 & DPR-48,respectively

ML20213G635
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	05/08/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20213G575	List: ML20213G573 ML20213G608 ML20213G635
References
NUDOCS 8705180380
Download: ML20213G635 (4)

Text

/ o mergq, URNTEJ 8TATES l' a NUCLEAR REGULATORY COMMISSION F, j me om o. c. ==

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.104 TO FACILITY OPERATING LICENSE NO. DPR-39 AND AMEN 0 MENT NO. 94 TO FACILITY OPERATING LICENSE NO. DPR-48 COMMONWEALTH EDISON COMPANY ZION NUCLEAR POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-295 AND 50-304 INTRODUCTION ,

The Comonwealth Edison, by letter dated February 10, 1987, requested on immediate,onetimeTechnicalSpecification(TS)changetoperformmaintenance and modifications on its comon "0" Diesel Generator (DG). This change allows that the present Limiting Condition for Operation (proposed LCO) 3.15.2.c for the "0" DG be extended from 7 days to 21 days during Spring,1987, while Unit 2 is in refueling. The subject DG is shared between two units and the 4 existing LCO 3.15.1.8 requires this DG to be operable whenever either unit is in operation, thus, the licensee has not been able to perform maintenance or j modifications which take longer than the 7 day LCO. i k Previously, Power Systems Branch reviewed a similar request from Zion and by memos dated November 4,1983 and January 27, 1984 from L. S. Rubenstein to G.

C. Lainas found that the request was warranted and therefore, granted. The only deviation from the previously approved amendment is a reduction in the requested time period from 45 days to the 21 days.

The proposed amendment is to improve "0" DG's reliability, personnel safety, and to comply with a 10 CFR 50 Appendix R comitment. The licensee also provided estimated manhours for each work item. The requested modifications and maintenance consists of:

1. Normal refueling outage maintenance.

2. Upgrading for DG instrumentation and control circuits, and DG turbo lube oil filter.

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3. Appendix R comitment modification for DG breaker and engine isolation switch.

4. Testing.

EVALUATION The DGs provide power for equipment required to safely shutdown the reactor and to remove reactor decay heat following a loss of offsite power (LOOP) or a LOOPandalossofcoolantaccident(LOCA). The Electrical, Instrumentation and Control Systems Branch / Division of PWR Licensing-A (PAEI) has reviewed the Auxiliary Power System which provides power to equipment necessary to safely shutdown. We find that:

1. The Switchyard maintains six-345kv offsite power sources which exceed the requirement of 10 CFR 50 Appendix A. GDC 17. The switchyard design (Ring-Bus Arrangement) locates system faults and isolates rapidly. As a result Zion has not experienced a complete LOOP since their criticality l in 1973.

2. The power supplies to Engineered Safety Features (ESF) buses are available from either Unit Auxiliary Transformer or System Auxiliar the offsite power source as well as the adjacent unit's Unit(y Transformer 2)offsite of power source through its System Auxiliary Transformers. Thus, including 3 a backfeed capability of the Unit Auxiliary Transformer, a total of four offsite power paths to ESF buses are available.

3. The ESF system is comprised of three independent divisions and the total loss of any one of the three electrical divisions on either unit will not prevent safe shutdown. In the event either of the Unit 1 DGs becomes inoperable, following a complete LOOP with the "0" DG on maintenance, the unit can still safely shutdown with one DG according to Table 8.4.2-1 of FSAR.

4 The Zion Probabilistic Safety Study regarding LOOP indicates that the pro-bability of occurrence of a total LOOP at Zion is considerably less than theindustryaverage(i.e.,0.068vs0.194 Events /Siteyear).

5. Whilethe"0"DGisoutofservice,theDGs(2Aand28)ofUnit2willbe available to power two additional service water pumps in case such a need arises and the DG's operability will be verified daily.

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TECHNICAL FINDINGS Considering the number of the offsite power sources and the ESF desi n features, it appears that the probability of a total LOOP per year i! low.

Furthennore, the occurrence of a total LOOP for the duration of 21 days while the "0" DG is outaged is even lower.

Because of the fact that the "0" DG is shared between two units and the TS requires it to be operable when either unit is in operation, any extensive maintenance which takes more than the allowed 7 day LC0 could not be performed.  ;

However, the experience with DG Maintenance indicates that an extended outage is often necessary and vital to assure DG reliability. l In addition, the licensee has connitted to maintain the operability of 2A and l' 28 of Unit 2 while it is on refueling (i.e., four DGs are available while the "0" DG is out) and the impact of this configuration has been analyzed by the Reliability & Risk Assessment Branch. The SER concluded that "the proposed configuration seem to be reliable, perhaps more so than the currently allowed configuration for the loss of offsite power sequences of concern". Since there has not been any ESF system configuration changes, the previously analyzed reliability estimates and conclusion should remain valid.

- Finally, Zion has implemented our previous SER recommendation wherein the surveillance testing 4.15.1.8.2 will be perfonned on DGs 1A,18, 2A, and 28 immediately prior to removal of the *0" DG from service.

{ It is our judgment that an event requiring plant shutdown concurrent with a ,

LOOP and the loss of an additional DG is a very unlikely event over the 21 day period and, therefore, does not represent a significant danger to the i

+ health and safety of the public.

We conclude that one time relief from the requirement of the TS is, therefore.

• acceptable and reconnend that their request be granted, i ENVIRONMENTAL CONSIDERATION i These amendments involve a change in the installation or use of the facilities components located within the restricted areas as defined in 10 CFR 20. The staff has determined that these amendments involve 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  !

cumulative occupational radiation exposure. The Connission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public connent on such finding. Accordingly. l these amendments meet the eligibility criteria for categorical exclusion set  ;

forthin10CFRSec51.22(c)(9). Pursuantto10CFR51.22(b)noenvironmental impact statement or environmental assessment need be prepared in connection with .

the issuance of these amendments.  !

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CONCLUSION We have concluded, based on the considerations discussed above, that: (1)there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regulations and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.

Dated: May 8,198.4'/

PRINCIPAL CONTRIBUTOR:

Peter Kang i r

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