ML20211M370
| ML20211M370 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 12/08/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20211M361 | List: |
| References | |
| NUDOCS 8612170156 | |
| Download: ML20211M370 (7) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 99 TOFACILITYOPERATINGLICENSENO.DPR-p AND AMENDMENT NO. 89 TO FACILITY OPERATING LICENSE NO. DPR-48 COPMONWEALTH EDISON COMPANY ZION NUCLEAR POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-295 AND 50-304 INTRODUCTION By letter dated September 19, 1986, the Commonwealth Edison Company (licensee) submitted a proposed technical specification (TSI change for the Zion Nuclear PowerStation(Zion) Units 1and2. The requested change would modify a limit-
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ing condition for operation (LC01 to allow one bettery charger assigned to a 125 V d.c. bus of a unit in either cold shutdown or undergoing refueling to be used indefinitely to fulfill the battery charger operability requirement of a d.c. bus of an operating unit. This would be physically accomplished through the use of existing crosstie circuit breakers.
DISCUSSION The need for this change derives from the planned replacement of the Zion station battery banks. This replacement effort is being conducted as part of a program to upgrade and expand the capacity of Zion's safety-related batteries. The 125 V d.c. power distribution systen at Zion consists of five battery banks. Two of the banks are assigned to Unit 1 (banks 111 and 112), two are assigned to Unit ? (banks 211 and 212), the fifth bank is assigred to supply power to both Unit 1 and Unit ?.
The two, Unit 1, dedicated batteries and the shared battery are scheduled to be replaced during the current refueling outage of Unit 1.
0612170156 061200 ADOCKOD00g;5 DR The replacement of the dedicated batteries is not envisioned to create a viola-tion of technical specifications. As stated in the referenced letter, a unit in
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the cold shutdown or refueling shutdown mode raquires only two batteries.
There-fore, using the shared battery plus one or the other dedicated Unit 1 banks to supply the d.c. requirements of Unit 1 is acceptable and satisfies the unit's safety requirements. However a problem arises when the shared battery undergoes replacement.
Technical specification 3.15.2.F which describes an LCO for battery chargers only, requires an operating reactor to be shut down within 14 days should a re-quired 125 V battery charger or its distribution system be made or found inoperable.
Since it is extremely difficult to separate a battery bank from its charger, remov-ing a battery from service effectively removes its charger from service.
It follows that any LCO related to a battery is necessarily applicable to its charger. Likewise, any TS requirement related to a battery charger is likely to impact its associated ba tte ry.
Licensee projects the need for longer than a 14 day period to replace the shared bank.
Based on paragraph F's requirements, this effectively prohibits the continued operation of Unit No. 2 after fourteen days.
EVALUATION The Zion Units' Technical Specification Section 4.15.1.E.4.c requires that a capacity performance discharge test be conducted each refueling outage.
In 1975, Section 3.15.2.E which describes an LCO for batteries only, required that a unit be placed in cold shutdown within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following the inoperability of a battery and/or distribution system. The performance of the required discharge
test for the 011 battery requires that 011 be inoperable for longer than ?4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
This would have evidently required the shutdown of the operating unit.
In response to this concern, the technical specifications were amended to allow one O.C. bus of a shutdown unit to fulfill the operability requirements of a D.C. bus of an operatino unit for an unspecified period.
This provision for the extended use of the D.C. buses dedicated to a shutdown unit was only applied to Section 3.15.2.E.
It was not extended to Section 3.15.2.F.
Licensee believes that the reason for overlooking paragraph F was that the dis-charge tests and subsequent recharging are easily completed within approximately 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br />. Thus, there was no need, in 1975, to extend the proposed chance to paragraph F.
Therefore, the amendment request granted by the referenced letter only addressed paragraph E.
Licensee feels that the logic that formed the basis for the approval transmitted in the referenced letter is precisely the same as the logic that Commonwealth Edison is proposing to justify this current proposed change. That is, when a unit is in cold shutdown or refueling modes, three batteries are not reouired.
Therefore, using one of the batteries from a shutdown unit to supply Lower to a bus of the other unit is acceptable.
The staff finds the licensee's argument unconvincing.
Appendix A of Part 50 nf the Code of Federal Regulations sets forth " General Design Criteria" (60Cl for i
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-4 nuclear power plants. GDC 5. " Sharing o' Structures. Systems and Components" prohibits the sharing of comoonents important to safety unless it can be shown that such sharing will not significantly impair the component's ability to per-form its safety function.
Any crosstie provision between generating units of a multi-unit site shnuld exist primarily to provide emergency interchange power or to facilitate maintenance or equipment changes.
Staff cannot foresee any maintenance need or testing recuire-ment which could not be accomplished within fourteen days. The plannad replacement is not considered a routine maintenance effort.
Never should a crosstie be allowed to be maintained on an indefinite basis particularly when the systen's original design did not envision, as a rnutine operating scheme, the continuous crosstieing of battery banks between units. This is particularly significant in light of the guidance contained in Regulatory Guide 1.81 " Shared Emargancy and Shutdown Electric Systems for Multi-Unit Nuclear Power Plants" which recommends that d.c. systems in multi-unit plants not be shared on an indefinite basis.
Contrary to licensee's contention, Staff's decision to restrict the March 14, 1975 technical specification change to Section 3.15.2.E does not appear to be an oversight. The staff view is that the reason the change was not extended to para-graph F was specifically to prevent the crosstieing of d.c. facilities for periods in excess of 14 days.
The TS change request states 11crnsee's willingness to accept the proposed change on an interim basis, pending completion of the staff's review. The staff's view is that, although a permanent change to the technical specification is inappropriate, an interim, one-time chance can be justified.
The staff bases this view on the fact that during the replacement effort, the power which would normally be supplied to Unit 2 by the shared battery, will be provided from one of the dedicated batteries of Unit 1.
Since this alternate source is safety grade and since the d.c. power requirement of Unit 1 is low due to its shutdown status, sufficient capacity will be available from the Unit 1 battery bank to temporarily supply the a.c. power needs of both units.
Staff can predict no series of events, having a reasonable probability of occurrence, which would jeopardize the safe shutdown capability of Unit 2 or the safe shutdown status of Unit 1 using this shared configuration for a short period of time.
TECHNICAL FINDING The staff proposes to grant in part and deny in part the licensee's amer.dment request.
For the reasons set forth above staff denies licensee's request to permanently modify Technical Specification Section 3.15.2.F to exclude the 14 day Ifmitation on crosstied operation of the d.c. distribution systems of Unit I and Unit 2.
However, in order to facilitate the replacement of the shared battery bank, staff grants the requested one time thenge. During the L' nit 1 Fall 1986 refueling outage with Unit No. 1 in Mode 5 or 6, one battery bus normally de-dicated to Unite 1 may be cross connected to the battery bus normally served by
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6-the shared battery. This one time change will be in effect until the replace-ment effort is completed or until January 31, 1987 (a date suggested by licensee),
whichever comes first. During the time the d.c. systems are cross connecteJ, the output voltage and current of the crosstied charger should be checked and recorded immediately and daily thereafter.
Reference:
Letter of March 14, 1975 from R. A. Purple, NRC, to B. Lee, 4
Commonwealth Edison Company.
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ENVIRONMENTAL CONSIDERATION 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 sionificant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that these amendments involve no sionificant hazards consideration and there has been no public comment on such finding. Accordingly, these amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR Sec 51.22(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 these amendments.
CONCLUSION We have concluded, based on the considerations discussed above, that:
1 (1) there is reasonable assurance that the health and safety of tha 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: December 8, 1986 PRINCIPAL CONTRIBUTOR:
E. N. Fields
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