ML20203L582

Safety Evaluation Supporting Amend 4 to License NPF-43

ML20203L582
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Site:	Fermi
Issue date:	08/22/1986
From:	Office of Nuclear Reactor Regulation
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SAFETY EVALUATION 9Y THE OFFICE OF NUCLEAR REACTOR PEGitLATION SUPPORTING AMENDMENT NO. 4 TO FACILITY OPERATING LICENSE NO. NPF 43 DETROIT EDISON COMPANY WOLVERINE POWER SUPPLY C00 PERATIVE. INCORPORATED FERMI-?

D0CKET NO. 50-341

1.0 INTRODUCTION

The Fermi-2 facility has been in either the cold shutdown or refueling modes since October 11, 1985, and was restarted in the beginning of Auoust 1986. On Mav 27, 1986, Detroit Edison Company (the licensee) identified a problem relating to a potential undervoltage condition durino an update of its degraded grid relay setpoint desion calculations. This problem caused the licensee to reevaluate the values of the relay setpoints at which the supply of emergency power for Division I is automatically switched from the preferred source (i.e., the 120 kilovolt grid) to the onsite power supply (i.e., the emergency diesel generators). The need to consider,raisino the values of the undervoltage relay setpoints was limited to Division I since the Division II power supply has safety-related voltage reculators which reduce the voltage change on the Division II safety-related buses and the lower voltage bus loads. The results of the licensee's reevaluation of appropriete values for the Division I degraded grid relay setpoints indi-cated that these setpoints.should be raised from their present values of 89 percent of nominal to 95 percent of nominal to be in como11ance with the licensee's comitment to design its system in accordance with the criteria in Branch Technical. Position (RTP) PSB-1, " Adequacy of Station Electric Distribution System Voltaces."

On June 4, 1986, the licensee reported this deficiency to the NRC in accord-ance with the reporting requirements of 10 CFR 50.72.

Subsequently, t'o correct this deficiency, the licensee submitted a request for an emergency amendment to the Fermi-2 Technical Specifications in its letter dated June 11, 1986. The licensee stated in its submittal that it needed this change processed as an emergency amendment in accordance with 10 CFR 50.91(a)(5) because the proposed technical specification change would allow it to declare the Division I system operable and thereby allow it to release Division !! for surveillance testing.

(Only one of the two safety-related electrical divisions need be operable when in either the cold shutdown or refueling modes.) On June 13, 1986, the NRC staff denied the licensee's request for an emeroency technical specification amendment but granted the Itcensee, pursuant to the staff's discretionary authority, interim relief so it could declare Division I operable despite the reported deficiency in the values of the degraded grid relay setpoints. This relief was granted for a limited time period (i.e., only for the cold, shutdown or refueling modes) on the basis that there was not sufficient fission product inventory 8600280056 060022 PDR ADOCK 05000341 P

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s in the core to represent a threat to public health and safety. The licensee did not reauest a change in the time delay associated with the Division I relay setpoints in its letter of June 11, 1986.

The licensee met with the NRC staff on June 19, 1986, to discuss the staff's need for additional information. Subsequently, the licensee submitted a similar request for an amendment to the Fermi-2 Technical Specifications in its letter dated July 2, 1986, and asked that it he treated as an exigent amendment in accordance with 10 CFR 50.91(a)(6).

In this latter request, the licensee again proposed changing the Division I dearaded prid relay setpoints from 89 percent to 95 percent of the nominal voltages but now also requested that the time delay associated with the actuation of the Division I relays be increased from 19.7 to 44.0 seconds.

(As in its earlier submittal, the licensee did not propose changina the Division II degraded grid relay setpoints.or the associated time deiay.) The intent of this proposed change in the Division I setpoints is to provide assurance that a sustained degraded voltace (i.e., undervoltagel on the 120 kilovolt grid would not result in a possible failure of safety-related components.

This failure could result because a sustained degraded grid voltaae would lower the voltage on the safety-related buses feedino the Division I Class 1E equipment.

This could lower the voltage'of the power supplied to safety-related equipment to a level below the perfonnance capability of this equip-ment. The time delay is established to provide assurance that the temporary, anticipated low voltage conditions, which would be caused by the starting of large motors, will not unnecessarily isolate Division I from the 120 kilovolt prid. The licensee later submitted additional informatien and clarifications on this matter in its letters da,ted July 15 and July 24, 1986.

In its letter dated July 30, 1986, and supplemented on July 31, 1986, the licensee asked that its previous reauest for an exioent technical specifica-tion amendment be treated as an emeroency in accordance with the applicable portions of 10 CFp 50.91.

2.0 EVAL.UATION The licensee's reevaluation of its calculations to determine the values of the degraded grid relay setpoints revealed that it had made an error in its assumption regardino the allowable lower limit for undervoltage of certain safety-related equipment.

It had been assumed that the Division I Class IE motors could sustain an undervoltage of -20 percent of the equipment namaplate voltage. However, more recent information from the vendors of this equipment indicates that the voltage tolerance on a number of these Division I Class IE motors is actually +10 percent to -10 percent. The licensee states that certain of these motors, which are tha limiting com-ponents determining the allowable Division I relay setpoints, have been verified by their vendor to be capable of performina at an undervoltage of

-13 percent of their nameplate characteristics. The limiting components are Limitorque motor operated valves. Additionally, the licensee has con-cluded that it cannot afford to continue to incorporate into its calcula-tions a design margin of four percent. This desian margin was originally 1

i incorporated by the licensee into its calculations to: (1) account for any drifting in the value of the relay setpoints; and (2) provide assurance 4

that safety-related electrical components will not be subjected to sustained i

low voltage conditions which are close to their allowable limits.

I The licensee's updated calculation, using the verifiable lower operational voltace limits of the Class 1E equipment and not incorporating the previous four percent design margin discussed above, indicates that the degraded grid relay setpoints for Division I must be raised from 89 to 95 percent of the nominal voltage to assure adequate protection of safety-related equipment.

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Additionally, the licensee has determined in its updated calculations that the voltage recovery time from a voltage condition below that of the under-I voltage relay setpoints when startino laroe motors, is 44,0 seconds for i

Division I as opposed to the value of 19.7 seconds which it originally cal-1 culated. This required increase in time delay is based on the licensee's reassessment of the time required for: (1) the load tap changer (LTC) sensing relay on the transformer feedino t'e Division I 4160 volt buses to

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actuate; and (2) the LTC to operate in order to increase the vn1tage on the bus. Specifically, the LTC is incorporated into the 13.2 KV/4.16 KV trans-former supplying offsite power to the Division I A160 vnit beses.

The licensee states in its letter of July 2,1986, that it has provided alarms which are initiated at a voltage of 98 percent of the nominal voltage on the 4160 volt buses. These alarms alert the plant operators to l

implement administrative procedures to recover the system voltage before i

the relay setpoint of 95 percent is reached. These procedures include i

i starting the on-site combustion turbine generators (CTG) and transferring

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house loads to alternate off-site power sources.

Based on our review of the licensee's proposed request to increase the l

undervoltage relay setpoints from the 89 to 95 percent of nominal at the j

Division I safety-related 4160 volt buses, we find that the likelihood of an increase in power supply transfers from the preferred off-site suoply (i.e., the 120 kilovolt grid) to the on-site power supply (i.e., the i

emergency diesel cenerators), will not increase significantly. Our deter-mination is based on: (1) the decrease in the grid voltage to a level which would result in isolation from the grid, would occur aradually in l

most cases so that there would be sufficient time followine an alarm at l

98 percent of the nominal 4160 volt bus voltage which would alert the j

operators, to permit the operators to take action to recover the system voltage; (2) the LTC feature in the 13.2 KV/4.16 KV transformer provides j

continuous voltage regulation of the power supply at the 4160 volt buses which can compensate for relatively large swings in the 120 kilovolt grid voltage; and (3) the licensee has used appropriately conservative assump-l j

tions reoarding the initial low voltage condition of the grid and the maximum loading on the Class 1E buses. Additionally, the licensee has provided information indicating reliability of the 120 kilovolt grid over a ten year period and the reliability of the LTC in the 13.2 KV/4.16 KV I

transfomer feeding Division I.

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_4-In the course of our review of the licensee's proposed request to increase the Div'ision I time delay from 19.7 to 44.0 seconds before isolation from the preferred offsite power supply and the subsequent transfer to the onsite i

power supply in the event of sustained low voltage on the grid, we developed a concern reoarding the impact of this increase on the performance of the j

Division I Class IE equipment. Specifically, the proposed increase in this i

time delay could sub,iect connected and starting electrical components to a 4

low voltage condition for a longer period of time than that which might occur at the present value of 19.7 seconds.

In response to our concern on i

this matter, the licensee stated in its letter dated July 24, 1986, that all i

safety-related Division I electrical components are capable of perfoming their intended function without suffering any damage from the increase in i

the time delay. The licensee's basis for this statement is that the addi-tional recovery time it calculated in its reevaluation is the time required for the LTC to raise the 4160 volt bus voltage to above 97 percent of nominal l

from a voltage level above 95 percent but below 97 percent. This latter i

value is the approximate voltage at which the relays will reset. The time interval during which the safety-related bus voltace recovers to above 95 percent after the start of large motors remains unchanged. Therefore, the licensee concludes that the Division 1 safety-related electrical components i

will not be sub.jected to a lower than acceptable level for a longer period by this change in the time delay. We agree and find this conclusion to be i

acceptable.

i In evaluating the licensee's requested change in the degraded orid setpoints, we were concerned that'the hicher relay setpoints could increase the 4

frequency of plant shutdowns (i.e., a reactor trip) and increase the j

frequency of unprelubricated (" dry") starts of the emergency diesel gener-ators (EDGs). We conclude, however, that the higher relay setpoints will 3

l not significantly increase the likelihood of reactor trips and " dry" starts l

of the EDGs because: (1) the offsite power supply at the 4160 volt buses will be regulated by the LTC on the transformer feeding these buses; (2) there is a history of reliable operation of the 120 kilovolt grid for the last i

10 years; and (3) the LTC perfomance has also been reliable.

Based on our conclusion that the increased value of the dearaded grid relay setpoints will not result in any significant increase of either reactor i

scrams or unprelubricated starts of the emergency diesel centrators and i

that the EDGs will continue to be available in the event of any voltage i

instability on the 120 kilovolt orid, we find the prnoosed change to the j

Divisions I undervoltage trip setpoints in Table 3.3.3-2 of the Femi-2 i

j Technical Specifications to be acceptable.

Additionally, we conclude that the proposed increase in the Division I time delay from 19.7 to 44.0 seconds will not sub,iect safety-related electrical components to low voltage levels which could adversely affect their per-fomance. Rased on this conclusion, we find that the proposed increase in j

the Division I time delay in Table 3.3.3-2 is also acceptable.

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Our conclusions reoarding the acceptability of the proposed change in the i

Division I degraded grid relay setpoints is decendent on the verification by Region III of the documented undervoltage characteristics of the Division I safety-related electrical components.

3.0 FINDINGS OF AN EMERGENCY WARRANTING AN AMEN 0 MENT WITH0 TIT NOTICE i

The licensee first identified the need for the subject technical specifica-i tion amendment in late May 1986, and submitted its initial request for a.

l license amendment on June 11, 1986.

In the ordinary course of events, the i

timing of this submittal would have pemitted the NRC staff to evaluate the ouestion of whether the requested change represented a situation of l

No Significant Hazards Consideration (NSHC), publish its proposed findings in the Federal Register and wait 30 days before taking any further action on the request. This could have been accomplished without impacting the restart of the Femi-2 facility. However, the staff stated in its letter to the licensee dated June 13, 1986, that the licensee had not provided l

sufficient.iustification in its letter of June 11, 1986, to support a finding that an emergency technical specification amendment was warranted.

Specifically, the licensee was asking the staff to make a finding that a condition which would be limitino in October 1986 (i.e., the reouired 1

j surveillances for Division II components) represented an emergency in June 1986. More significantly, the staff found that the licensee had not sub-mitted sufficient infomation to cemit the staff to make a detemination i

regarding NSHC or to conduct its review of the reouest and complete its evaluation. To resolve these issues, the staff requested that the licensee meet with it; t,his meeting was held on June 19, 1986.

4 The staff has no acceptance criteria reoarding how hinh the degraded arid I

relay setpoints may he set. Accordingly, the staff felt that it was neces-j sary to probe, indepth, those factors which led to the proposed change in the values of the setpoints as well as to gain an understanding of the licensee's

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calculational techniques, including the underlying assumptions in this analysis. The staff's concern in this matter was that the value of the l

proposed setpoints (i.e., 95 percent of the nominal bus voltages) appeared

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to be relatively high compared to the prior value of 99 percent and those values used at other nuclear power plants. The underlying concern was that l

these relatively high setpoints could result in a sionificant increase in the frequency of reactor trips and unnrelubricated starts of the emergency l

diesel generators. After having discussed the staff's concerns and deter-i mined what additional information the staff needed for its review, the i

licensee resubmitted, on July 2, 1986, its original request which was modified to reflect the discussion at the meeting of June 19, 1986.

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l We find, based on the preceding discussion, that the licensee's request on June 11, 1986, for the subiect technical specification amendment j

submittedwithinareasonableoeriodoftime(i.e.,abouttwoweeks$was i

following recognition by the licensee of the need to do so. We further I

find that the licensee acted in a prudent and responsive manner to the staff's request for additional infomation and justification to support a c

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relativ.ely high value for the relay setpoints.

Given the nature of our i

underlying concerns in this matter and the consequent need to supply ample 1

information, we find that the resubmittal of the request for the technical specification amendment in about two weeks from the meeting on June 19, 1986, l

was a reasonable time for the licensee to respond.

While this modified request was resubmitted in a reasonable time frame con-i siderino the staff's concerns cited above, the licensee asked in its letter l

cf July 2, 1986, that its latest request be treated as an exigent amendment.

This request for a shortened notice period was predicated on an estimated restart date of July 23, 1986. The licensee stated that the normal noticing procedures which require a 30-day waiting period following publication in j

the Federal Register would thereby delay restart of the Fermi-2 facility.

j An initial start review of the licensee's letter of July 2,1986, indicated that the licensee had not provided sufficient justification for treatino this resubmittal as an exigent reouest. Accordingly, the licensee submitted on July 15, 1986, its basis for requesting an exigent amendment. The staff t

i found this acceptable and published its intention of issuino an exigent amendment in the Federal Register on July 22, 1986 (51 FR 26319).

Sub-sequently, the licensee requested in its letter dated July 30, 1986, and 1

supplemented it on July 31, 1986, that the subject technical specification be treated as an emeroency amendment. The licensee's basis for this emergency request was that there was no other impediment to restart.

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We have previously found that the licensee had provided sufficient justifi-cation for treating its request of July 2, 1986, as an exigent amendment.

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On July 31, 1986, although Region III was prepared to authorize restart of i

the facility, the licensee could not, by technical specification require-ments, commence restart of the facility without having both Division I and II operable and could not declare Division I operable until after the sub-

,iect technical specification amendment had been issued.

Based on this con-i sideration, the fact that the staff had already made a Final No Significant Hazards Consideration Detemination and had drafted a safety evaluation in which the staff found that the proposed technical specification amendment

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was acceptable, the staff informed the licensee in a telephone call on August 1, 1986, that it had found that the circumstances representing an i

emergency situation existed and could not have been avoided by prior appli-cation. Accordingly, the staff found in accordance with 10 CFR 50.91(a)(5),

that a valid emergency existed. On this basis, the requested emergency technical specification amendment was issued on August 1, 1986.

i 4.0 FINAt. NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION The Commission's reculations in 10 CFR 50.92 require that the Commission make a final determination that a license amendment involves no significant hazards considerations if operation of the facility in accordance with the r

amendment would not:

1 (1)

Involve a significant increase in the probability or consequences of an accident previously evaluated; or

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(2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3)

Involve a significant reduction in a margin of safety.

The information in Section 2.0 above provides the basis for evaluating this license amendment against these criteria. Since the reouested change to the Division I dearaded grid relay setpoints and the associated time delay are acceptable and the plant operating conditions, the physical status of the plant, and dose consequences of potential accidents are the same as without the requested change, the staff concludes that:

l (1) The proposed changes to the Division I degraded grid relay setpoints and the associated time delay in the Femi-2 Technical Specifications will not involve a significant increase in the probability or con-sequences of an accident previously evaluated because: (a) the pro-posed undervoltage relay setpoints for Division I continue to provide assurance that, in the event of an accident, there will be a reliable source of power available for the Class 1E buses of this division to operate the reoufred safety-related components and systems; (b) the.

emergency diesel generators will continue to be available.in the event of any voltage instability on the 120 kilovolt grid; and (c) the lowest voltage at safety-related equipment permitted by the revised setpoints will continue to be at or above the lowest voltages at which the safety-related equipment can function satisfactorily; (2) The proposed change to the Division I degraded grid relay setpoints and the associated time delay in the Femi-2 Technical Specifications will not create the possibility of a new or different kind of accident from an accident previously evaluated because the worst case (i.e.,

bounding) accidents, and the assumptions used in the analysis of these accidents, remain unchanged.

Specifically, the Division I relay set-points will continue to switch from the preferred source of power (i.e., the 120 kilovolt orid) to the emergency diesel generators if there is any significant and sustained decrease in the 120 kilovolt l

prid voltage. The increase in the time delay from 19.7 to 44.0 seconds will not change the accident analysis assumptions because the i

actual time period during which the Class IE equipment could be sub.iect i

to lower voltage which mioht damage the safety-related electrical equipment, remains effectively unchanged; (3) The proposed change to the Division I degraded grid relay setpoints 1

and the associated time delay in the Femi-? Technical Specifications will not involve a significant reduction in a margin of safety because even though there is a slightly bicher probability of an automatic, unprelubricated start of the energency diesel generators, the probability of a reactor trip and an automatic start of the EDG's' has been demonstrated to be relatively small based on the voltage stability of the !?O kilovolt arid over a ten-year period as well as '

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j the demonstrated reliability of the load tao changer on the 13.2

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KV/4.16 KV transformer which feeds the safety-related 4160 volt buses j

in Division I.

Additionally, the licensee has increased the time i

delay before the relays actuate to provide assurance that there will be sufficient time for the LTC transfomer to compensate for a decrease in the voltage of the 4160 volt buses due to starting of large motors l

when the 120 kilovolt grid voltage is at its lower limits, therehv.

minimizing unnecessary actuations of the EDGs.

Based on the above analysis, the proposed amendment involves no sionifi-l cant hazards considerations.

5.0 STATE CONSULTATION

In accordance with the Commission's reculations, policy, and procedures, a consultation was held with the State of Michican, Division of Radiological Health, by telephone on August 1, 1986. The coment by the State was that i

... it believes that the NRC's basis is sufficiently conservative." This comment was offered after a discussion of the conservatisms in the NRC's evaluation of the proposed change to the technical specifications.

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6.0 ENVIp0NMENTAL 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 i

and changes in surveillance requirements. The staff has determined that j

this amendment involves no significant increase in the amounts, and no i

significant change in the tyoes, of any effluents which may be released l

offsite, and that there is no significant increase in individual or cumula-tive occupational radiation exposure. The Comission has reached a finding that this amendment involves no signficiant hazards consideration. Accord-l-

inoly, this amendment meets the elicibility criteria for categorical exclusionsetforthin10CFR51.22(c)(9).

Pursuant no environmental impact statement or environmental as;to 10 CFR 51.22(b),

sessment need be pre-pared in connection with the issuance of this amendment.

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7.0 CONCLUSION

l The Comission made a finding that the subject amendment involves no signifi-cant hazards consideration which was published in the Federal Register I

(51 FR 26319) on July 22, 1986, and consulted with the State of Michigan.

i No public comments were received, and the State of Michigan comments are addressed above.

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

i (1) the amendment does not (a) significantly increase the probability or consequences of an accident oreviously evaluated (b) create the possibility of a new or different kind of accident from any previously evaluated or (c) significantly reduce a safety naroin and, therefore, the amendment does i

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e 9-not involve a significant hazards consideration; (?) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner; and (3) such activities will be con-ducted in compliance with the Commission's reculations and the issuance of the amendment will not be inimical to the common defense and the security or to the health and safety of the public.

Principal Contributors:

Evanoelos Marinos, DBL, NRR M. D. Lynch, DBL, NRR Dated:

August 22, 1986 s

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