ML20082N810

Safety Evaluation Supporting Amend 99 to License NPF-30

ML20082N810
Person / Time
Site:	Callaway
Issue date:	04/18/1995
From:	NRC (Affiliation Not Assigned)
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ML20082N804	List: ML20082N810
References
NUDOCS 9504250387
Download: ML20082N810 (5)

Text

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t UNITED STATES NUCLEAR REGULATORY COMMISSION If WASHINGTON, D.C. 2000H001

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.99 TO FACILITY OPERATING LICENSE NO. NPF-30 UNION ELECTRIC COMPANY CALLAWAY PLANT. UNIT 1 DOCKET NO. 50-483

1.0 INTRODUCTION

By letter dated September 9, 1994, as supplemented on December 22, 1994, Union Electric Company (UEC) requested an amendment to Operating License NPF-30, which would revise the Callaway Plant Technical Specifications (TS) 3/4.8.2.1, 3/4.8.2.2, 3/4.8.3.1, and 3/4.8.3.2.

Specifically, the proposed changes would address the 125-volt DC busses and include provisions for swing battery chargers, which will be added during the current refueling outage. Additionally, changes would address 120-volt AC vital busses and remove provisions for the 4160-volt and 480-volt AC emergency busses.

The December 22, 1994, submittal provided supplemental information which did not affect the initial proposed no significant hazards determination.

2.0 EVALUATION The onsite AC power distribution network contains two independent divisions of electrical busses (NB01 and NB03).

Each of these divisions or load groups consists of one 4160-volt AC emergency bus that feeds, via transformers, four 480-volt emergency load center busses (NG01/NG03, NG02/NG04). The NG busses supply power to the four full-capacity chargers (NK21/NK23, NK22/NK24).

Each charger supplies a Class IE 125-volt DC bus (NK01, NK03, NK02, or NK04) and an associated battery bank (NKll, NK13, NK12, or NK14).

Each DC bus also supplies a Class IE 120-volt AC vital bus (NN01, NN03, NN02, or NN04) through an associated inverter (NNll, NN13, NN12, or NN14).

In the amendment request, the licensee proposed a revision to Technical Specifications (TS) 3.8.2.1 and 3.8.2.2 (125-volt DC sources) and TS 3.8.3.1 and 3.8.3.2 (onsite power distribution). The licensee proposed that TS 3.8.2.1 and 3.8.2.2 for battery banks and chargers be revised to include the 125-volt DC busses and provisions for installed swing chargers, which will be added to the plant design during the current refueling outage.

The licensee proposed that TS 3.8.3.1 and 3.8.3.2 be revised to address only the 120-volt AC vital busses. The specifications for the 4160-volt and 480-volt emergency busses would be deleted, since these busses supply 9504250387 950418 yDR ADOCK 05000483 PDR

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• power to the battery chargers for which there are more restrictive limiting conditions for operation (LCO), action statements, and surveillance requirement (SRs) in TS 3.8.2.1 and 3.8.2.2.

The licensee's interpretation of " operable" requires that when a line is deenergized, the most restrictive allowed outage times (A0T) for the bus and/or the loads it supplies govern plant actions as prescribed by the TS.

The licensee also proposed two modifications to the plant design during the current refueling outage. The first modification would provide permanently installed swing chargers for the 125-volt DC system. The second would provide uninterruptible power supplies (UPSs) for the 120-volt AC vital instrument power supplies. The current TS provides for one spare battery charger and one spare inverter for the power block.

These items are physically located central to all of the Class 1E DC systems but are not electrically connected.

If a charger or inverter should fail, the spare could be connected to the affected system and the malfunctioning equipment could be repaired without long-term disruption of the system.

In the proposed modification the current battery charger will be permanently installed as a swing charger for 125-volt DC buses NK01 and NK03. Another charger will be procured and installed as a swing charger for 125-volt DC busses NK02 and NK04. This modification will be made under the provisions of Section 50.59 of Title 10 of the Code of Federal Regulations (10 CFR 50.59).

It will allow 125-volt DC power to be supplied from the installed swing chargers, whereas the previous design did not allow switchover in the 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> A0T specified in the current TS.

The second modification is an upgrade of the existing inverters (NNII, NN13, NN12, and NN14).

Each existing inverter will be replaced by a state-of-the-art UPS consisting of an inverter, a standby 480-volt to 120-volt isolation transformer, and an automatic transfer switch.

The gating and synchronization circuit of the new UPS will monitor the plant AC system and keep inverter output in phase and the same frequency as the backup supply. This will allow make-before-brake transfers so that the bus is not deenergized at any time. This modification requires no TS changes and is being made under the provisions of 10 CFR 50.59.

2.1 Chanae to Technical Specification 3/4.8.2.1 The proposed TS 3.8.2.1 LCO includes busses NK01 and NK03 and installed full-capacity battery charger NK25 in part a) and busses NK02 and NK04 and I

full-capacity battery charger NK26 in part b).

In the action statement, the term " battery bank and/or full-capacity charger and DC bus" is replaced by the term "DC electrical source." This change is also clarified in the associated Bases section.

TS 3.8.2.1 would include all requirements for the 125-volt DC sources.

Since the busses are included in the LCO, this specification would become a "standalone" and does not rely on current TS 3.8.3.1.

TS 3.8.3.1 is limited to the 120-volt AC vital buses. The swing chargers are being added to the LCO to allow for flexibility. The chargers will supply one bus at a time.

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r SR 4.8.2.1.a.3 will be added, since the DC busses will be addressed within TS 3.8.2.1.

It also ensures that the buses are energized by stipulating the verification of correct breaker alignment and indicated voltage on the buses at least once every 7 days.

Since the proposed changes do not involve any design changes nor are there any changes to the method by.which any safety-related plant system performs its safety function,-the staff finds the proposed changes acceptable.

2.2 Chanaes to Technical Specification 3/4.8.2.2 The proposed TS 3.8.2.2 LC0 addresses the DC busses and the swing chargers for consistency with TS 3.8.2.1, except only one DC source is required in modes 5 and 6.

The action statement and SR are modified to use the term "DC electrical source."

These changes are similar to those discussed under Section 2.1 and are acceptable for the same reason.

2.3 Chanaes to Technical Soecification 3/4.8.3.1 The proposed TS 3.8.3.1 LC0 addresses only the 120-volt AC vital busses and their associated inverters.

The requirements for 4160-volt AC emergency busses (NB01 and NB02) and 480-volt AC emergency busses (NG01, NG03, NG05E, NG02, NG04, and NG06E) are deleted.

The requirement in the current TS 3.8.3.1 LC0 that tie breaker 52 NG0116 between 480-volt buses NG01 and NG03 and tie breaker 52 NG0216 between 480-volt buses NG02 and NG04 be open will be relocated to Table 3.3-3, Action 19, Functional Unit 8.b (loss of power 4 kV bus undervoltage - grid degraded voltage), which allows a single tie breaker to be closed for up to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to repair failed or degraded equipment.

A requirement will be added to Table 4.3-2, functional Unit 8.b, to verify on a weekly basis that these tie breakers are open.

The portion of TS 3.8.3.1 LC0 that addresses 125-volt DC busses NK01-NK04 will be deleted, since it will be incorporated in TS 3.8.2.1 (DC source).

TS 3.8.3.1.a Action Statement will be deleted, since it only stipulated actions in the event an AC emergency bus was not fully energized.

TS 3.8.3.1.c Action Statement is al:o being deleted, since it will be incorporated in the proposed TS 3.8 2.1 Action Statement.

The LCO in TS 3.8.3.1 will be revised to address only 120-volt AC vital buses and their associated inverters.

iiie requirements for 4160-volt AC emergency busses (NB01 and NB02) and 480-volt AC emergency busses (NG01, NG03, NG05e, NG02, NG04, and NG06E) are deleted from this LC0 because the definition of operable as used by the licensee requires that when a bus is deenergized, the most restrictive A0T for the bus and/or the loads it supplies govern plant actions as prescribed by the TS.

Busses NB01/NG01 and NB02/NG02 will supply Class IE battery chargers.

If they are

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4-deenergized, the 2-hour A0T of LC0 TS 3.8.2.1 will apply, since a battery charger will be deenergized. Busses NG03 and NG04 also will supply

-battery chargers and will have a 2-hour A0T.

If one or both of these l

buses were deenergized and the DC bus was supplied by the associated swing charger, the A0Ts of the rema' ing loads would be assessed.

In all likelihood, the A0Ts would bs restricted to that associated with a i

containment isolation valve, i4.e of which are 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

Similarly, busses l

NG05E and NG06E would supply lo,dt csociated with auxiliary equipment of i

the essential service water syst e + ose A0T would be 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, I

consistent with TS 3.7.4.

On the Ww of the licensee's commitment that i

when a bus is deenergized the most restr*ctive A0T for the bus and/or the loads it supplies govern plant act"ons as orescribed by the TS, the staff finds deletion of the requirements for 4%a-volt and 480-volt AC emergency busses from the LC0 in TS 3.8.3.1 atcept s h.

The requirement to maintain the tie breakers between the redundant hs open is relocated from TS 3.8.3.1 to Tables 3.3-3 and 4.3-2.

The changa also includes, in Table 3.3-3, Action 19, an 8-hour A0T when a s W is tie breaker between busses NG01 and NG03 or NG02 and NG04 is closed to repair failed or degraded equipment. The closing of the tie breaker would cause the degraded voltage bistable setting to be incorrect, resulting in the inoperability of four of four channels of one safety load group, thus exceeding the I

minimum channels needed and placing the plant in TS 3.0.3.

The staff agrees that there is a safety benefit to operating the plant under this i

degraded condition with the tie breaker closed for a short time to repair I

failed or degraded equipment while the redundant train is fully operable and protected, rather than requiring a forced shutdown under the constraints of TS 3.0.3.

In a letter dated December 22, 1994, the licensee revised Action 19, Table 3.3-3, to state that a single tie breaker may be closed for up to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> only to repair failed or degraded equipment.

On this basis, the staff finds the proposed change is acceptable.

The requirement added to Table 4.3-2, Functional Unit 8.b.,

to verify on a weekly basis that these tie breakers are open, enhances safety and is therefore acceptable.

The relocation of TS 3.8.2.1 LC0 (DC source) to the portion of TS 3.8.3.1 that addresses 125-volt busses NK01-NK04 represents a restructuring, so that all requirements associated with the DC sources, including the busses, are addressed in a single specification.

The staff finds the proposed change is acceptable.

Action Statement 3.8.3.1.a is not necessary because the requirements for AC emergency busses are deleted from TS 3.8.3.1.

As described previously, the loads to which the emergency busses supply power dictate plant actions as prescribed by the TS. Action Statement 3.5.3.1.c is also deleted because it is covered by the proposed LCO in TS 3.8.2.1 and its action statement. The staff finds the proposed changes are acceptable.

Additionally, the number sign (#) before each electrical bus, battery, and battery charger listed is deleted, and "120 Volt A.C. Vital" is added before the electrical busses in TS 3.8.3.1.

This revision is typographical and will make the affected pages more consistent with others and, therefore, is acceptable.

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4 2.4 Chances to Technical Soecification 3/4.8.3.2 The LCO in TS 3.8.3.2 addresses only the 120-volt AC vital busses and their associated inverters, and those portions that address the AC emergency busses and the 125-volt DC busses are deleted.

The action statement addresses only 120-volt AC vital busses. These changes are similar to those discussed under Section 2.3 and are acceptable for the same reason.

The staff finds the licensee's proposal to restructure and simplify DC sources and AC vital busses acceptable. The changes are consistent with the licensee's definition of " operable" which requires the most restrictive A0T be imposed for the bus and/or the loads it supplies when a bus is deenergized.

Therefore, the staff finds the proposed TS amendment request acceptable.

3.0 STATE CONSULTATION

In accordance with the Commission's regulations, the Missouri State official was notified of the proposed issuance of the amendment.

The State official had no comments.

4.0 ENVIRONMENTAL CONSIDERATION

The amendment changes a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements.

The staff has determined that the 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 cumulative occupational radiation exposure.

The Cormission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding (60 FR 506). Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 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 this amendment.

5.0 CONCLUSION

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 endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) 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: S.K. Mitra Date: April 18, 1995

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