Text

Replaces Documenting Discussion & Actions Taken on 891107 & 08 Re Util Verbal Discretionary Enforcement Request Concerning Tech Spec 15.3.0.A
	ML19332D506
Person / Time
Site:	Point Beach
Issue date:	11/10/1989
From:	Fay C; WISCONSIN ELECTRIC POWER CO.
To:	; NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML19332D505	List: ML19332D504; ML19332D506;
References
	CON-NRC-89-141 VPNPD-89-583, NUDOCS 8912040064
	Download: ML19332D506 (10)
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November;10, 1989 s

? Document. Control: Desk h

U.~S'. Nuclear Regulatory Commission Nail.Stop Pl-137 Washington,,DC 20555 REQUEST'FOR DISCRETIONARY ENFORCEMENT RELATED TO TECHNICAL SPECIFICATION 15.3.0.A

' POINT-BEACH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET'NOS. 50-266'AND 50-301-J n

lGentiement-A' letter documenting-the discussion and actions taken on November 7

.cnd 8, 1989, concerning Wisconsin Electric's verbal discretionary-fcnforcement request'was.provided on November 8, 1989.

This. letter correctseinaccuracies and clarifies the corrective actions.

As

.such,2thiscshould replace the November 8Lletter as documentation

'+j cf the discretionary enforcement request.

.on November 7,.1989,; Wisconsin Electric verbally requested discretionary enforcement for the Point Beach Nuclear Plant Units 1 cnd 2 Technical-specification 15.3.0.A.

This Limiting condition for' operation states:

"15.3.0.A:-

Many of the Limiting Conditions for Operation

'(LCO) presented in these specifications provide-a-testporary

. relaxation of the single failure criterion, consistent with E ' !' -

1overall: reliability considerations, to allow time periods during which corrective action may be taken to restore the

[.

O a. !.. system to full operability.

If the situation has not been

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corrected within the specified time period, and the LCo.

lgo-prescribes no. other-specification action, an affected unit, l

which is critical, shall be placed in the hot shutdown N $g$

condition within three hours.

In the event an LCO cannot.be g

satisfied because of-equipment failures or limitations beyond

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those 'specified in the' permissible conditions of the LCO, the g

affected unit, which is. critical, shall be placed in the hot Mg,

-shutdown condition within three hours of discovery of the

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situation."-

un November 7, 1989, it was discovered that the Point Beach Nuclear

= Plant _ was in a condition which was outside of the requirements of TS.~15.3.7.B.I.f and 15.3.7.B.l.g.

These TS state:

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?. Document Control Desk Novembei 10, 1989 Page'.2-l "15.3.7.B.l.f:

One of the batteries DOS or D06 may be inoperable for a period not exceeding 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months provided the

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other three batteries and four battery chargers remain 1

operable with one charger carrying the DC loads of each DC r-main distribution bus."

"15.3.7.B.l.gs One of the batteries D105 or D106 may be inoperable for a period not exceeding 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months provided the other three batteries and four battery chargers remain operable with one charger carrying the DC loads of each DC main distribution bus."

1 The requested' discretionary enforcement provided for the completion of charging battery D106 with the DOS and D06 batteries having been L

declared-technically inoperable in li.eu of taking Unit 1 to the hot L

chutdown condition as required by TC 19.3.0.A.

At the time the i

discretionary enforcement request was made to NRC Region III L

representatives, Unit 2 was and remains in the cold, refueling

-chutdown condition.

-On' November 6',

1989, at 2029 hours0.0235 days 0.564 hours 0.00335 weeks 7.720345e-4 months , a 72-hour LCo was entered when battery Dlo6 was removed from service for its five-year per-formance test.

At 0120-hours on November 7, the performance test was successfully completed and the battery was placed on a float charge.. It was anticipated that charging of this battery would be completed within the 72 hour8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months LCO (i.e., well before 2029 hours0.0235 days 0.564 hours 0.00335 weeks 7.720345e-4 months on l

November 9,-1989.)

It should be noted that D106, although being L

performance tested,.had its DC loads served by the charger and a qualified battery utilizing cables which were not' seismically qualified..This DC bus, therefore, had both normal and emergency power.

Nonetheless, the 72 hour8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months LCO was entered conservatively.

On November.7, 1989, at 1600 hours0.0185 days 0.444 hours 0.00265 weeks 6.088e-4 months , the PBNP Manager's Supervisory

' Staff determined that the'D05 and D06 station batteries were technically inoperable as a result of the discovery of an original plant: design deficiency which could render one or both of the two plant main DC systems : noperable as a result of a single bus f4 ult._ The potential problem had been reported to the Manager-PBNP at 1200 hours0.0139 days 0.333 hours 0.00198 weeks 4.566e-4 months by our' corporate-headquarters Nuclear i

Engineering group.

Upon arrival at the plant site approximately two hours later, the Nuclear Engineering group engineer presented the' issue to the Manager's Supervisory staff.

Subsequently, the MSS concluded that at the time of this determination, PBNP was cperating outside of Technical Specification requirements for the DC power system.

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.'Documsnt control Desk yf - No.vember:20, 1989 4

TPa'oe 3

Background

An independent" safety system functional inspection (SSFI) was

-performed by.a contractor in 1988.

During this audit, the team reviewed the-adequacy of protection of the main DC systems at Point Beach Nuclear PlantL(PBNP).

One of the audit findings

-(SSFI WE 88-14) stated'that the available short circuit current at q

.the main DC buses.D01 and D02 was' 15,700 amps and that.the UL

. rating. for-the main battery breaker (Westinghouse BMA 1200 amp) was~

q caly-10,000-amps.

During the audit, verbal confirmation was

.cbtained from' the manufacturer that a Type HMA breaker was capable p

of interrupting up to 20,000 amps when applied on a.125 V DC o

cystem.- This verbal information was subsequently confirmed in a 11etter,"which'also stated that testing had been done to confirm g

' this level' of interrupting capability, p

our response to the audit finding was that we would obtain test l

' data from Westinghouse and compare its acceptability for use in place of the-UL rating..In the course of our followu.p to obtain-the Westinghouse test data, it was confirmed on Novem>er 7, 1989, that the data originally discussed was not applicable to the type of. breaker ~ installed at PBNP.,

i The original design of;the PBNP DC systems utilised circuit breakers' exclusively in the distribution panel portions of the system.

This includes breakers in D01 and D02 which have thermal but not magnetic tri;p elements

Such breakers include the main ig ut breaker from tse system. battery (Westinghouse W HMA s

1200 amp), the supply breakers to panels D12 and Die (Westinghouse Type HLA 400 amp) and the supply breakers to panels D11 and D13 (Westinghouse Type HLA 300 g ).

It also includes the use of similar breakers in Panels Dll and D13 (Westinghouse Type HEA 70 amp).

This design is shown on Bechtel draw 2ng 6118-E-6 (Sheet 1).-

This type of breaker is also specified in the original

.cpecification for tsese panels (Bechtel specification 6118-E-37).

i Recent discussions with both Bechtel and Westinghouse have not

.resulted in. a. definition of the reason for utilization of this cpecial type of breaker (thermal overload only)it provides for in this

-cpplication.

One possible-explanation is that celectivity between successive breakers and between breakers and fuses'in some of the equipment supplied by these circuits.

It is usually not possible to obtain proper selective coordination between two molded-case circuit breakers which both have magnetic trip elements.

This is because the magnetic element in each breaker. will operate almost instantaneously to interrupt any fault

in excess of a specified fault current for the-breaker.

As such, it:is indeterminate _as to which breaker in a series combination will operate first to clear a fault or whether or not such operation will prevent the second breaker from also operating.

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[DocumentiControl Desk'

'NovemberL10, 1989 3

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g-m The use of. circuit breakers in the main portions of.the DC systems Lwasidiscussed with the NSSS supplier (and: breaker manufacturer) the 1

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architect-engineer who designed the system,Jas well as-with a contractor. performing our' electrical system coordination study, and L

Lwith other utilities.

It appears the~ design of our DC system is b

1 unique to this-facility.

Most other nuclear units utilize fuses or

-l

< fuse-disconnects'in this type of-application.

Because fuses onl i have-a thermal characteristic over their entire operating range,yit

-is -generally not difficult to obtain selective coordination between w

series devices.

Fuses, however, have relatively-.high interrupting

-1 capacityfunlike the thermal trip only breakers 2nstalled at PBNP.-

Several' of the circuit breakers in main DC buses D01 and D02 : and imost of those in buses.D11 and D13 are of a type which do:not have i

'the magnetic: trip function.

This results in 'hese breakers t

having only a thermal trip function.

Thus, the breakers are not

capable of interrupting fault currents of magnitudes in excess of cpproximately ten times the trip rating.. Fault currents of such tragnitudes are possible on some of the circuits-protected by these 1y breakers. -A fault on one of these circuits could result in

-currents which would not be. interrupted by any of the breakers in

c the-DC' system.

This could result in the fault current being custained until one of the components in the DC system o

catastrophically' fails or until the battery supplying the system is-. discharged'to a point where it no' longer can prov2de' sufficient snergy.:

Most of the circuits protected by such breakers, which originate et either Dol or~ D02, are considered safety-related.

As such, cufficient physical and electrical separation exists between these

. circuits such that simultaneous failure of both Dc systems (or any partLthereof) due-to a single incident is not considered probable.

In addition,: the fact that these conqponents are nuclear safety related required that they be QA.

On the other hand, some of the

' circuits originating at distribution panel. Dll and D13 run to common pieces of equipment.or in common raceways.

H For each of the 4160 V and 480 V AC buses, a separate DC control

' power supply is provided from D11 and D13.

For each of these

' buses, the two DC control power supplies are connected to a knife cwitch which allows for selection of one of the two DC supplies as that~which provides control power for the bus.

Several of the same circuits supplied from D11 and D13 are classified as nonsafety-related.

As such, these circuits in some d-cases are not physically separated from each other.

This results in the possibility that simultaneous faults on both DC systems s

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'could: occur due to the location of these circuits in a common raceway.: This. situation could also potentially result in failure L of both plant DC. systems.

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' Problem: Description L

L 1.

The supply to each bus D01 and D02 from the associated battery

.is protected by a Westinghouse HMA 1200 amp thermal trip on).y breaker.

The manufacturer has stated it is their opinion that Lthis-breaker will not interrupt fault currents in excess of u

L about 8000 amps.

Preliminary calculations indicate that a bus l

fault on either of these. buses could result in a fault current of up-to 16,000. asps.--A failure to interrupt such a fault:say u

result in total loss of the DC system which has been faulted.

While this is not a desirable situation, a single bus fault on either D01 or D02 will result in failure of only one of the two plant main DC systems.

This is due to the physical and electrical separation of these buses.

l 2.-

The supplies to DC distribution panels Dll and D12 (from D01)

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,and D13 and'D14 (from D02) are protected by Westinghouse Type HLA thermal.only breakers.

Westinghouse has stated that Lit is their opinion that these breakers will not interrupt

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fault. currents in excess ofiabout'5000 amps.

Preliminary calculations indicate that faults on these circuits could I

result.in a fault current of up to 16,000 amps.

A failure to interrupt such a fault may result in total failure of the DC system faulted.

However, a single bus or cable fault at Dil, D12, D13, Die,. or any of the cables supplying them will result 1in failure of only one of the two plant main DC systems. ~This is due to the fact these buses and the-supplies to them are considered safety-related and are therefore adequately physically and electrically separated.

3.

Failure on circuits supplied from D12 and Die are not of concern since all of the breakers in these-panels are of a thermal-magnetic' type and will adequately interrupt faults on circuits protected by them.

16.

Most of the breakers in panels.Dil and D13 are Westinghouse Type HFA thermal trip only.

Westinghouse has stated that it is their opinion that these breakers will not interrupt fault currents in excess of 2000 amps.- Preliminary calculations indicate thrit fault currents of up to 12,000 amps could occur on the circuits protected by~ these breakers.

As previously described, such faults could result in the failure of the DC system on which the fault occurs.

Unlike the situations described in (1) and (2) above, there is not always adequate

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y iDocument Control Desk lNovembo,r.10, 1989 Page 6' o

separation between the nonsafety-related circuits supplied by D11 ("A" train, DOS battery) and D13 ("B" train, D06 battery).

Breakers 1 through 20 in each of these panels provide control power to a single 4160 V or 480 V bus section.

Corresponding t

breakers from each panel provide a normal and alternate

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source.of control power (e.g., breaker #1 in D11 provides the

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normal ~ supply to 4160 V bus section 1A01 and breaker #1 in D13 provides an alternate supply to the same bus).

These pairs of circuits are connected to a knife switch arrangement in each bus.

It is possible that a casualty or failure in

- the vicinity of this switch could potentially result in a fault on h th circuits simultaneously and subsequent E

L' failure of both DC systems due to lack of a breaker anywhere in the supply path from the battery capable of interrypting

- the. fault current.

In addition, many of these same circuits l

are not considered safety-related.

This has resulted in nonsafety-related circuits originating at D11 and nonsafety-

- related circuits originating at D13 being run in common l'

- raceways.

Therefore, simultuneous faults could occur in selected raceway. sections which could ultimately result in failure of both plant DC systems.

Conclusion

~

It was concluded by' the Manager's Supervisory Staff at 1600 hours0.0185 days 0.444 hours 0.00265 weeks 6.088e-4 months en November 7, 1989, that to prevent the possibility of a single n

. fault rendering both main DC systems-inoperable, nonsafety-related E

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-loads must be shifted from one station battery to the other while naintaining-the maximum degree of redundancy possible.

The l

decision to shift nonsafety-related loads to battery DOS was based l-upon the following considerations:

' Switching of the. Unit 2 nonsafety-related loads from their

1..

normal to alternate supply (DOS battery) results in no possibility of a trip signal being generated to Unit 2 which 7

is shut down for refueling.

Whereas if Unit I nonsafety-related loads would be switched to their alternate supply l

(D06. battery), there could be a finite probability of generating a trip signal'to Unit 1.

The above results in all nonsafety-related loads (1&2A01,

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1&2A02,1&2B01, and 1&2502) being carried by batten DOS.

This removes the potential of a single fault affecting both batteries.

Assuming the ultraconservative, unanalyzed condition of a simultaneous Unit 1 and Unit 2 safeguards initiation, the switching of Unit 2 nonsafety-related loads to DOS adds a 2.

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,, November-10,,1989-2 Page.7 total of 108 amps maximum discharge for the first five seconds

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and 68 amps between five to ten seconds.

This is within the load. analysis for DOS, which' assumes 1001 amps for the first minute.

2.-

There-is a concern for safety-related loads about the L

_ interconnection of their respective breaker panels, D11 and

]

L D13.

With. four exceptions he alternate supply breakers to those knife switches were opened to preclude de pensibility of faults affecting both-DC trains-due to the presence of the circuits in. common equi;pment.

In the process of developing the work plan to open tie alternate supply breakers, the alternate supplies from D06 to 1A01, 1A02, 1801, and 1802 L

were not opened. until Wednesday afternoon.

L p

In addition to-the above, it was determined that these type'of breakers also supply DC power to the turbine crossover steam 1

dump system..Thus, potential short circuits affected by the

-cabling to this system should be addressed by removing the L

, crossover steam dump system from service and opening the affected breakers.

since the turbine crossover steam dump system is enabled at power levels exceeding 92%, it was determined that Unit.1 power level'should be reduced such that control power to the crossover steam dump system need not be. supplied by the Dc system.

corrective Actions

',1.-

.NRC Region III representatives were contacted at 1600 hours0.0185 days 0.444 hours 0.00265 weeks 6.088e-4 months by

~ the Manager-PBNP and-informed of the situation.

Neither of the resident inspectors was available at the plant at this time.

2.

At'1620 hours0.0188 days 0.45 hours 0.00268 weeks 6.1641e-4 months an orderly power reduction of Unit 1 to below the'92% power level commenced such that enabling of the-turbine crossover steam dump system for overspeed protection

.would not be re9uired.

As Unit 2 was in the refueling shutdown condition, the unit was not impacted by this issue.

3.

At approximately 1620 hours0.0188 days 0.45 hours 0.00268 weeks 6.1641e-4 months the NRC resident inspector was reached at his home and notified of the matter.

4.

At 1637 hours0.0189 days 0.455 hours 0.00271 weeks 6.228785e-4 months an ENS.notific'ation of the event to the NRC operations center was accomplished.

S.

.Between 1600-1730 hours, the following actions were accomplished:

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B-D*ocument Control' Desk November: 10, J1989.-

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A work plan for shifting nonsafety-related loads (2A01, a.

2A02, 2B01, 2B02) from D06 to DOS was developed.

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A L work p1an was developed for opening safety-related T

load' alternate control power breakers.

The work plan F

contained' provisions for performing this action in a' methodical-and sequential manner, with safety-related loads being carried by Unit 2 being accomplished first.

The work plan also contained provisions for verifying alternate DC control power supplies prior to opening the

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alternate Dc control-power breakers with subsequent verification that control power is available following the shift.

In conjunction with development of the work plan, an evaluation of_ potential Appendix R concerns was

-performed; It was concluded that for the purposes of Appendix R there is some redundancy in the backup DC g

L control power circuitry from D106 to D06 and from D105 to DOS.

Thus, with D06-and D105 fully operable, Appendix R concerns are satisfied.

As noted earlier'no work plan included opening the alternate supply ' breakers from D06 to the-Unit i nonsafety-i:

1 related; loads, Although it was determined that the DOS battery would c.

be considered'to be this inoperable battery, it was acknowledged this battery would be carrying additional L

nonsafety-related 3 cads (i.e. the control circuits for L

2A01,.2A02, 2B01,Jand 2B02).

Accordingly, a safety evaluation was performed to ensure that the battery could accommodate the additional loading.

The safety evaluation concluded the additional loading would be within the load analysis for that battery.

d.

A search was conducted for replacement de control breakers which possess the magnetic trip element.

Although several breakers of this type were located in our company storerooms, it was determined that they could not be :.natalled because of concerns associated with NRC IE Bulletin 88-10.

An evaluation was conducted of the effect of the e.

' proposed short-term corrective actions upon Unit 2 was conducted. ~A check valve in the "B" train of residual heat removal was out of service for maintenance, thus rendering "B" train inoperable.

It was pointed out that since fuel was.being reloaded into the core, decay heat removal capability was required in accordance with

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t TS :15.3.8. -It was acknowledged that if station battery DOS failed, there would be certain-conditions when the "A" train of residual heat removal ~would'not be remotely started'from the control room.

The "A" train of residual heat removal:has been in operation since the initiation p-

- of;the fuel reload and therefore, is therefore considered to be operable, f.

Additional' corrective action planning for restoring DOS

- to'an. operable status was initiated.

An: evaluation of potential Appendix R concerns was g..

. performed.

- 6..

- Between 1700-1730 hours NRC Region III representatives (Messrs. DeFayette and Jack 1w) were again contacted by the L

Manager-PBNP and informed'of the current status of the issue.

A third conversation, with Messrs. DeFayette and Jackiw was

. held from 1740-1755-hours.-

7.

. At 1800 hours0.0208 days 0.5 hours 0.00298 weeks 6.849e-4 months , the discretionary enforcement request was granted by NRC Region III personnel.

L 8.-

At 1900 hours0.022 days 0.528 hours 0.00314 weeks 7.2295e-4 months , all nonsafety-related DC loads had been shifted ito batte n DOS and all alternate power supply-breakers for safety-related loads had been opened.-

Note that the alternate power supplies to nonsafety-related loads from D06 had not t,

i I

been opened.

7 9.

On November 8,1989, at 0920 hours0.0106 days 0.256 hours 0.00152 weeks 3.5006e-4 months , batteg D106 was functionally restored to operability ~and the interim battery was> removed from the D106' bus.- Completion of associated work

~i activities.followed and'the battery was declared to be fully operable at 1007 hours0.0117 days 0.28 hours 0.00167 weeks 3.831635e-4 months .

At the time this cleared the Technical Specification issue of operating Unit 1 in a " condition prohibited by Tech Specs."

Subsequently it was determined that the alternate power supplies from D06 to Unit i nonsafety-related loads had not been opened.

10.

A modification request is in progress to restore battery DOS to full' operational status.

There are a total of eight non-safety-related breakers which must be replaced; however, priority-is being devoted to the four Unit I loads (IA01, lA02, 1801, 1802).

Replacement breakers having the mapetic

- trip-element. have been identified as being available within the facility.

These~replacem+9t breakers were located in spare breaker positions.

The 10 CFR 50.59 safety evaluation conducted for this modification addresses the replacement breakers with magnetic trip elements.

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11. 'The 2A01, 2A02, 2B01, and 2B02 connections to D11 and D13 have their breakers opened.

This results in the nonsafety-related loads to Dil.and D13 being disconnected and making it impossible for fault currents from those loads causing failure of.the plant and Dc: buses.

12.. Appropriate breakers with sufficient fault-current 6-capabilities will be procured and installed to supply 2A01, 2A02, 2B01,.and 2B02.

This will restore operability to these loads and allow restart of Unit 2 in accordance with the PBNP l-Technical Specifications.

f

' 13. -- The breakers for the turbine crossover steam dump system will be. replaced before the steam dunip system is declared L

operable and Unit 1 power level increased.

l It should be noted that performance testing of D105 is planned and h

will occur during the next few days as allowed by TS 15.3.7.B.1.g.

L Very truly yours, 1

e/

l C. W. Fay

-Vice President Nuclear ~ Power amp Copies. to NRC Regional Administrator,- Region III NRC Resident Inspector p

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ML19332D506

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