ML20116F797
| ML20116F797 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 11/02/1992 |
| From: | Piet P COMMONWEALTH EDISON CO. |
| To: | Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20116F800 | List: |
| References | |
| NUDOCS 9211110044 | |
| Download: ML20116F797 (8) | |
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l Commonwealth Edison O
1@0 Opus Place Noven,be r 2, 1992 l
'O Dc Aners Gmve, hhnors 60M5 Mr. A. Bert Davis liegional Administrator U.S. Nuclear Regulatory Connission Region III 799 Roosevelt Road Glen Ellyn. IL f>0137
Subject:
Dresden Nuclear Power Station Units 2 and 3 Request for Regional Temporary Waiver of Compliance to Facility Operating Licenses DPR-19 and DFR-25 NROJockethou50 237_and_30:2A9
Reference:
Teleconf crence between Connor.eealth Edison and NRC Staf f,
dated October 30, 1992.
Dear Mr. Davis:
This letter confirmo the conclusions reached during the referenced teleconf erence between Connonwealth Edison (CECO) and the NRC Staf f on October 30, 1992, during which CECO requested a Regional Temporary Waiver of Compliance to the Actions required upon a total loss of function to the Degt.
'd Voltage (Secono Level Undervoltage) protective features (Technical Specit ication Section 3.2.B, Table 3.2.2, Note 1).
Ccmmonwealth Edison sincerely anpreciates the timely efforts of the NRC staff (both at Region III and NRR) in the review of the proposed Temporary Waiver of Compilance.
CECO requested that the requirement necessitating an innediate ano orderly shutdown to cold conditions be waived inter,nittently (for up to a maximum period of one hour per bus, not to exceed two occurrences per bus) f or the duration of the waiver period.
The applicable Degraded Voltage (Second Level Undervoltage) relays affect the following 4160 volt buses at Dresden Station: 23-1, 24-1, 33 1, and 34-1.
The requested waiver period, effective
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for both Dresden Unit 2 and Unit 3, will commence at 12:00 PM (CST), October
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31, 1992 and end no later than 12:00 PM (CST) on November 3, 1992. NRC Region III verbal approval was received at 7:25 PM (CST) on October 30, 1992. The basis for this request is attached, and includes ue following:
A discussion of the requirements for which a waiver is requested.
A discussion of the circumstances surrounding the situation, including the need for prompt action and a description of why the situation could not have been avoided.
A discussion of compensatory actions.
An evaluation of the safety significance and potestial consequences of the proposed change.
A discussion which justifies the duration of the equest.
The basis for concluding that the request does not involve a significant hazards consideration.
The basis for concluding that the request does not involve irreversibic environmental consequences.
9215: 10044 921104 PDR
.\\ DOCK 05000237 ZNLD/2262-1 P
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Mr. A. lert Davis November 2, 1992 The request for a Regional Temporary Waiver of Compliance has been revir 'e i and approved by Commonwenith Edison Senior Management, as well as_by the Dresden Station On-Site Review Committee in accordance with Commonwealth Edison procedures.
If at any time Commonwealth Edison anticipates that the temporary alteration, and or testing compromises the capability of the trip function in any way, Dresden Station will immediately enter the appropriate action statement and initiate an orderly shutdown of the affected unit.
As of November 1,1992, CECO successfully completed all work as described in the Temporary Waiver of Compliance.
Please direct any questions regarding this submittal to this office.
Sincerely, t ;/&w k
Peter L. Piet Nuclear Licensing Administratcr Attachment cc: NRR Document Control Desk W. Forney - RIII R. Barrett - NRR B. Siegel, Project Manager - NRR W. Rogers, Senior Resident Inspector - Dresder.
Of fice of Nuclear Facility Safety - IDNS i
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l ZNLD/2262-2 l
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1, DISCUSSK)M OETHE REQUISEMENTS FOR.WHICH A.WAIVERJS REQUlHED.
The Dresden Unit 2 and 3 Technical Specifications (DPR-19 and DPR-25, respectively), Appendix A, Section 3.2.B. Table 3.2.2, " Instrumentation That Initiates or Controls the Core and Containment Cooling Systems" specify the protective requirements for Degraded Voltage -(Second Level Under voltage). The Trip Function for Degraded Voltage on the 4 kV Emergency Buses Trip level setting is specified as " Greater than or equal to 3708 volts (equals 3784 volts less 2% tolerance) af ter'less than or V) equal to 5 minutes (plus 5% tolerance) with a 7 second (plus or minus inherent time delay."
For the purposes of this waiver of complian
, the Trip function needs to be bypassed intermittently (for less than or.e hour to exceed two occurrences per bus} f or a short duration in order to not modify the relay configuration that controls the initiation of degraded voltage protection. The action statement for this trip f unction requires immediate shutdown with total loss of function. Total loss of function will be realized for a maximum time period of one hour per ESF Division with the proposed temporary alterations.
Due to the requested time period requested for this waiver, Ceco believes this to be a Regional Waiver of Compliance which will begin at 12:00 noon (CST) 10/31/92 for a duration of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> as the time duration is less than 7 days.
E CIRCUMSTANCES _SURBOUNDING_THEERVAllON Recently, Commonwealth Edison received notice of a Part 21 (10 CFR 21) concern rivarding the ABB Type 27N relays. This type of relay is usad to provide pr ection in the event that a Degraded Voltage condition occurs at Dresden on the 4160 volt buses 23-1, 24-1, 33-1, 34-1.
The ABB 27N undervoltage relays detect a degraded condition on busses 23-1, 24-1, 33-1, and 34-1 and will transfer the source of power from thece busses to the emergency diesel generator. Additionally, it will not allow the restart of the icw pressure ECCS pwmps until voltage has been restored and the relay has been reset.
The purpose of the Part 21 notification was to alert 1;teesees to the fact that the ABB Type 27N relays have been'shown to be susceptisle to setpoint-drift if subjected to elevated radiation doses. Such radiation levels-are expected to occur during a postulated LOCA with significant_ fuel failure.
The setpoint could potentially drif t. high and the undervoltaga trips would occur instantaneously.
Consequently, this setpoint drift will result in a loss of offsite power to the 4 kV safety buses that would prevent subsequent restart of the LPCI and Core Spray pumps. CECO =immediately initiated a Part 21 evaluation upon receipt of the notification and determined that the operability of the relays were in question. CECO subseouently initiated an Operability Evaluation to determine. the operability of the relays and determined that the installed relay.
configuration was susceptible to high radiation in the event of a LOCA,
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with severe-fuel damage and subsequent injection of the 2B.and 3A Core The 27N undervoltage relays are irradiated by the core spray Spray pumps.
line 1404-12 in a post LOCA scenario.
To eliminate the effects _of radiation, as a compensatory measure, e o Spray pumps 2B and 3A vere taken out-of_ service (pulled to lock).
.a a result an ENS notification was made on October 27, 1992.
73LD/2262-3
Curr ently, both Unit 2 and Unit 3 are in a seven day 1,C0 (Technical Specifications 3.5.A.2).
Core Spray is the source of the elevated dose rates associated with the relays during the postulated accident.
To remedy the situation, the ABB 27N relay configuration needs to be modified to removt the portion of the relay susceptible to the radiation drift problem.
The harmonic filters, designed to filter excess noise from the signal, is the portion of the relay to which the susceptibility to high radiation fields exists.
During the time that the first relay is removed, a trip of that relay contact will be installed (ie., jumper).
Following the modification and calibration of the first relay, the relay will be reinst s11ed, the jumper removed, and then the relay will be tripped by removing the voltage to the relay momentarily and this will test the relay contacts.
At that Up to this point the regraded voltage protection is operabic.
time the agastat relay must be replaced to maintain the seven second delay f unction.
Once the agastat relay has been replaced the existing relays no longer provide a 7 second delay but rather a 14 second delay since only one of the relays has been modified.
Just before the agastat relay is replaced, the second level relay trip will be bypassed to expedite the subsequent testing of the agastat relay. This makes inoptrabic the second icvel degraded voltage protection. At this time a jumper will be installed to simulate a trip of the second level relays and verify that the relay contacts are functional. Next the trip and reset functions of the second relay are installed (ie., jumpers). The reset function is maintained 1y utilizing a spare contact on the first relay. At this time the second level undervoltage protection is restored. Then the second relay is modified, calibrated, and installed. During the testing of this second modified degradet voltage relay, the affected diesel generator would be momentarily (less than 1 minute) incapable of supplying power to its loads because the restoration of voltage after an actual degraded voltage condition would not be recognized by the logic.
Finally the jumpers are removed and this relay is tripped similar1 to the first relay.
3, plSCUSSON OF_ COMED 4SATOftY_ACT10t4S As previously stated, the 2B and 3A Core Spray pumps have been pulled to lock and are administrative 1y out-of service, thus reducing the probability that the ABB 27N relays would be subjected to a postulated radiation field.
In the time period that the waiver is in effect and the relay modifications and testing are being performed, access to and around the switchyard area will be severely restricted, thus reducing the probability that disturbances to the grid will occur.
For the de stion of the waiver, operating personnel will be on standby and in communica' ion with plant personnel perf orming the temporary alterations and associated testing, to ensure, in the event of a degraded voltage condition, that the plant can be brought to a safe configuration without risk of injury to plant personnel or risk to plant i
equipment.
heightened 1cyc1 of awareness briefing shall be given to all involved
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personnel ensuring a complete communication line is initiated and continued throughout the plant evolution.
I 7.NLD/2262-4
An administrative verification of operability of the appropriate emergency diesel generators, LPCI and IIPC1, shall be performed prior to the initiation of the waiver.
This demonstration of operability shall be limited to an administrative verification of logs or other information to determine if the appropriate systems are in the proper alignment The load dispatcher shall be informed of the situation, stressing the need f or maintaining grid stability in the vicinity surrounding the i
Dresden Station switchyard. This measure ensures that the probability of entering a degraded voltage condition is further reduced.
Prior to the perf ormance of the temporary alteration and/or testing, all plant personnel involved in the physical changes shall be well versed in this maneuver; thus reducing the chances of an inadvertent trip of the relay function.
4.
EVALUAINN_OETHELE din "iWANGE AND f'Q1EMBALCDNSEAUENCES The current plant conx prulon J!.D m y one core spray pump is within the safety analysis of 0 0,L's for the allowed-outage-time specified by the Technical Specificatsor Actions. Due to the limited time for which the degraded voltage condition is bypassed within the duration of the waiver re pest, the proba ility of a design basis event (1.ACA) ir conjunction with a degraded voltage condition occurring is minimal.
With the above mentioned compensatory measures in place, all saf ety functions at the plant can be accomplished to mitigate a design basis accident. For the duration of the waiver, the risk to the plant is minimal due to the limited time (less than one hour per Division not to exceed two occurrences) that the degraded volta p protection is bypassed and because the other Division is still available.
If at any time CECO anticipates that the temporary alteration. and or testing compromises f
the capability of the trip function in any way, we will immediately enter the action statement and initiate an orderly shutdown of the affected unit.
5, IMSCUSStON_WHICtLJUSIIBES_THEAUfLADOfLOETHC.BEQUESI The duration of the requested temporary waiver for Dresden Unit 2 and 3 is for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> starting at 11:00 PM (CST), October 31, 1992 and ending no later than 12:00 PM (CST) on November 3, 1992.
This duration is necessary in order to provide a suf ficient time period to allow the safe completion of the temporary alteration and any associated qualification testing associated with the ABB 27N relays.
The duration of the waiver (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) is of a time f rame that limits the risk of the plant due to the shcrt duration that the automat!c protective f eature may be bypassed..
2NLD/2262-5 1i-
The risk associated with the occurrence of a DEA during the duration of the waiver is concidered minimal. The degraded voltage protection for each ESF Pus will be disabled f or one hour per bus for the duration of the walver. The station has taken compensatory actions which will reduce the activities external and internal to the plant which could increase the occurrence of a degraded voltage condition. All emergency core cooling systems are operable with the exception of one core spray pump por unit.
Four LPCI pumps and hPC1 will be availabic to facilitate safe shutdown and decay heat removal following the loss of coolant accident.
6.
pASIS EOft CONCLUQ4NG3MATJHE HEQUESIDOES_NODNYOLVE A S!GNIBCANUiAZARDS_ CONSIDERATION Commonwealth Edison has evaluated the proposed temporary waiver of compliance and determineo that it does not represent a significant har.t.rds consideration.
Based on the criteria which defines a significant hazards consideration established in 10 CFR 50.92(c),
operation of Dresden Units 2 and 3 in accordance with the request for Temporary Walver of Compliance will not:
InvolveAsientficant JocreaseJn hprobotWitty_pr_conseguences_atan,accMortt pf1VIOUSly pyaluated; The climination of the protective relays does not increase the probability of a degraded voltage condition, or any other type of accident scenario. The failure or loss of the relays are not assumed to initiate any accident, especially a degraded voltage condition.
For the duration of the waiver, the risk to the plant is minimal due to the limited time (less than one hour per Division not to exceed two occurrences) that the actual degraded voltage protection is not in service and because the other Division is still available. With the compensatory measures in place, operating personnel will be available and ready to retain the manual initiation of all mitigative techniques.
Ct9 ele _1tle_p0S$1bility.pfAneyterJtfferent Altigf_pCGMenLff9m3Gy.p(9Yl0Ully evolusted:
The f ailure or loss of a protective degraded voltage (second icvel) relay is not assumed as any accident initiator. Therefore, the proposed configuration of the plant for the limited duration of the waiver does not create the possibility of a new or different kind of accident form any previously evaluated.
INLD/2262-6 e.
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Does.not involve a.signmcent reductionJRthe.marginoffefety; The probability of a degraded voltrge situation ccincident with a LOCA for the duration of the waiver request is minimal. Normal plant operation is unchanged for the duration of the waiver.
For the duration of the waiver, the risk to the plant is minimal due to the limited time (less than one hour per Division not to exceed two occurrences) that the actual degraded voltage protection is not in service and because the other Division is still available. The compensatory measures instituted by the site reduce the probability that a degraded voltage condition would be expected within the Dresden Station switchyard.
Therefore, for the duration of the waiver request, the margin of safety is not significantly reduced.
7, BA383 EOR _ CONCLUDING _THAT_THE.f?EQUESLDQES_HQllN10 LYE IRREY_EBSID.LE EMYlRONMENTAL_ CONSEQUENCES The request does not involve a change in the use of the facility as defined in 10 CFR 20.
There are no increases in the probability of an event that would increase the dose consequences to the public. There is no significant increase in the probability of a scenario that would challenge systems necessary to mitigate the dose consequences to the public. Commonwealth Edison has determined that this Temporary Waiver of Compliance does not involve a significant increase in the amount, or a significant cbange in the types, of any effluents that may be released off-site and that there is not a significant increase in individual or cumulative occupational radiation exposure.
This Temporary Waiver of Compliance meets the eligibility criteria for a categorical exclusion set forth in 10 CFR $1.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with granting of the Temporary Walver of Compliance.
l ZNLD/2262-7 i
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