ML20062A588
| ML20062A588 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 10/10/1990 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20062A554 | List: |
| References | |
| NUDOCS 9010220188 | |
| Download: ML20062A588 (15) | |
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'4 ENCLOSURE 2 ARKANSAS NUCLEAR ONE. UNIT 2 (ANO-2)
STATION BL ACK0UT SAFETY EVALUATION REPORT i
1.0 INTRODUCTION
On July 21, 1986, the Code of receral Regulations ICCFR Part 50, was amended to include a new Section 50.63, entitled " Loss of All Alternating Current Power,"
(StationBlackout). The station blackout (SBO) rule requires that each light-water-cooled nuclear pcwer plant be able to withstand and recover from an SB0 i
of specified duration, requires licensees to submit inforr.etion as defined in 10 CFR Part E0.63 and requires licensees to provide a plan and schedule for conformance to the $80 rule. The SB0 rule further requires that the baseline assumptions, analysis and related informatien be available for NRC review.
Guicance for conformance to the rule is provided by (1) Regulatory Guide (RG) 1.155,StationBlackcot,(2)NUMARC87-00,GeidelinesandTechnicalBasesfor HUMARCInitiativesAddressingStationBlackoutatLightWaterReactors,and-(3)
NUl: ARC 87-00 Surplemental Questions / Answers anc Major Assurptions dated December 27,1909 (issued to the industry by NUMARC January 4,1990).
TofacilitatetheNRCstaff's(hereafterreferredtoasstaff)reviewoflicensee.
resportu to the SBC rule, the staff endorsed 2 generic response formats. One respor se format is for use by plants proposing to use an Alternate. AC (AAC) pont source and the other format is for use by plants proposing an AC indepen-dent response. The generic response formats provide the staff with a summary-of the ruults from the licensee's analysis'of'the plant's SB0 coping capability.
The licensees are expected tu verify the accuracy of the results and maintain documentation that supports the stated results.
Compli6nce to the SB0 rule is verified by a review of the licensee's submittal, er audit review of the supporting documentation as deer.ed necessary, and possible followup NRC inspec-tions to ensure that the licensee has implemented the appropriate hardware end/or procedure modifications th6t will be. required to coroply_ with _the SB0 rule.
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2-For ANO-2 the licensee has proposed using existing energency diesel generators (EDGs) as an AAC power source and has submitted its response in the applicable generic resporise forr.at. The licensee's original response was provided by letters f rom T. G. Campbell (Arkansas Power & Light Co.) to V. S. Iluelear Regulatory Commission (NRC) d6ted April 13, 1989.
In addition, the licensee provided responses to the NUMARC 87-00 Supplemental Questions / Answers by letters from N. S. Cains and J. J. Fisicaro to itRC dated April 3,1990, and July 17, 1990. The licensee responses were reviewed by Science Applications International Corporation (SAIC) under contract to the NRC. The results of the review are doeurtnted by a SAIC Technical Evaluation Report (TER), SAIC-90/1377, ArLLntes Nuclear One Unit 2 Station Blackout Evaluation," dated September 17, 19EC- ( Attachnient No.1).
2.0 EVAll'ATION
After reviewing the licensee's SB0 subir.ittel anc the SAIC TLR, the staff-concur 5 with the ccnclusions as identified in the SAIC TER (refer to Attachnient No. I for details cf the review).
Based on this review, the staff findings and recomer.dations are summarized as follows.
2.1 Station Platkout Duration The licensee has calculated a minimur acceptable statiun blackout duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> Ltsed on en offsite power design characteristic group of "P1", 6n Emergency AC configuration group "C", ar.d an EDG reliability t6tget of.95.
The target EDG reliability was based on ANO Unit 2 EDGs having en average reliability greater than 0.95, 0.94 and 0.90 over the last 100, 50 and 20 demands respectively.
The P1 grouping is based on an independence of offsite power classification of Group "I 1/2",a severe weather (SW) classification of Group "2" and an extremely severe weather (ESW) classification of Group "1".
After reviewing the availtble inforr.ation in the licensee's submittal, RG 1.155, NUMARC 07-00 and SAIC's TER, the staff agrees with the licensee's evaluation of a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> SB0 coping duration.
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2.2 Alternate AC (AAC) Power Source The licensee has proposed using existing EDGs as an AAC power source to operate systen;s necessary for the required SB0 coping duration and recovery therefrom.
2.2.3 General Staf f Position on AAC Power Sources The definition in 10CFR $50.2, RG 1.155 and NUMARC 87-00 define AAC power source in terms of four attributes: (1) connections to the offsite or the onsite AC power systems, (2) minimum potential for coninon cause failure with effsite power or the onsite emergency AC power sources, (3) tirely availability, and(4)requiredcapacityandreliability. More specifically, in regard to the fourth attribute, the 500 rule reads as follows:
"(4) Has sufficient espacity and reliability for operation of all systems required for coping with station blackout and for the time required to bring and maintain the plant in safe shut-down (non-design basis accident)."
In view of the variety of types, c6pacities and capabilities of power sources l
proposed as AAC sources by various licensees, the staff has characterized pro-posed AAC power sources es being either optin.um, fully capable or parti 611y capable. This characterization, which relates cnly to the capacity attribute cited above, was necessary in order to f acilitate the sthff review of licensee responses to the SB0 rule.
It does not invalidate or revoke any of the requirements or guidance applicable to AAC power sources.
An optimum AAC power source design is one that is capable of powering simultan-eously both safety trains of normal safe shutdown systems 6nd equipment.
Such-a design, following actuation of the AAC source, would provide completely re-dundant normal safe shutdown capability during an SB0 and recovery therefrom from the rain control room.
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4 A fully capable AAC power source design is one that is capable of powering at least one complete safety train of normal safe shutdown systems and equipment.
This includes decay heat removal, battery charging, HVAC (heating, ventilation and air conditioning), emergency lighting, and the associated controls and instrumentation. Thus, although redundant capability is not available, a fully capable AAC source would enable attainment of safe shutdown during an SB0 and recovery therefrom from the main control room.
A ninimally capable AAC power source design is one that is not capable of powering all (or any) normal s6fety train related safe shutdown equipment; but it is capable of powering specific equipinent that, in conjunction with extensive manual operator actions both inside ar2 outside of the control room, is criticel for attaining safe shutdown during an SBO.
Apperdix R diesels 7
proposed as an AAC source are examples of minirnelly capable AAC sources.
With this design, operability cf the main control room could not be assured unless the batteries were sired to operett for the SB0 duration, or battery charging capability was provided by the AAC source.
2.2.1.1 EDGs Used as AAC Power Sources The guidance on the use of existing emergency diesel generaturs (EDGs) as AAC powter sources it documented in the station blackout rule 10 CFR 550.63, RG 1.155 position C.3.3.5 and NUMARC 87-00 (Section 2.3.1(3). This guidance is further explained in NUMARC 87-00 Supplemental Questions and Answers dated December 27, 1989, under questions 3.4 and B.3.
The station blackout rule states:
At multi-unit sites, where the combination of emergency ac power sources exceeds the minimum redundancy requirements for safe shut-down (non-DBA) of all units, the remaining emergency ac power sources may be used as alternate ac power sources provided they meet the l
applicable requirements."
. 4 The rule statement requires minimum redundancy.
This means that in order to qualify as an AAC source, there must be an EDG available in the non-blackout (NB0) unit that is in aadition to the number of EDGs required to meet the min-imum EDG redundancy requirenent for powering a normal safe shutdown for a loss cf cffsite power (LOOP) event.
Thus, the EDG's in a two unit site with two dedicated EDG's per unit would not qualify as AAC sources because the two EDGs per unit just meet the minimum redundancy requirement, i.e., there is no excess EDG.
Howe.ver, there ere some plants at two ur.it sites which just meet minimum re-dundancy but where each EDG is of sufficient capacity to fully power all the normal LOCP loads of the NB0 unit, and also ht.s sufficient excess capecity for powering the required safe shutdown ic6ds of the SB0 unit.
In recognition of the existence of this type of situetion, the staff has interpreted the excess EDG redundancy recuirement of the SB0 rule to 6110w EDGs just meeting the minimum EDG redundancy reevirements, to qualify as AAC sources on the basis of excess capacity, provided the other enlicable requirements for AAC sources are also tr4t.
The NRC's basic position on the use of EDGs as AAC power sources on the basis of excess capacity is that such excess capacity should nct be attained by load shedding in the NB0 unit which results in a degradation of its normally avail-able safe shutdown capability for the less-of-offsite-power (LOOP) condition.
Any actions that would add to the burden of operators that are already in a high stress environment, such as lead switching or disablement of information read-outs or alarms in the control rcom, are considered to be a degradation of normal safe shutdown capability for LOOP-in the NB0 unit. The staff position is therefore that the norral equipment compliment should remain available with ocequate EDG capacity for use should it becvme necessary. The NEO' unit should have the capebility for hot shutdcwn/ hot stanoby forced cooling, cooldown and depressurization as required.
While additional events are not explicitly being postulated, it is not prudent to dimir.ish the capebility of the NB0 unit to raitigate problems should they arise.
It is not in the interest of safety to-I
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i 1 reduce the capability to handle various eventualities in one unit for the purpose of meeting the SB0 rule in another unit.
Each unit must n.eet the SBC rule on its own merits without reducing another unit's capability to respond to its own potential problems.
Therefore, e multi-unit site with the dedicated EDGs just meeting the minirom redundancy requirement but not having the excess capacity defined above for qualifying as an AAC scurce does not neet the SCO rule AAC source option requirements. Further measures are required such as a separate AAC source or a coping analysis which shows the plant can cope with and recover from SB0 for the required duration independer,t of AC power.-
C 2.2.1.2 Conr.ectability of AAC Power Sources The besic criteric governing the connectability of an AAC power source are contained in 10CFR 50.2 (The /AC source should be connectable to but nornelly not connected to the cffsite or onsite emergency AC power systems),10CFR 50.63 (500 should net assume a concurrent single failori or design basis accident.),
and in Apper. dix A of 10CFR 50 (The single failure criterion and the irdependence requiremt.nts apply to the NB0 unit.).
Therefore, in a one unit site as a minimum en AAC source need only be connecteble to one set of safe shutdown equipment, regardless of whether that equiprent is part of a safety train or not, or whether the AAC source is an excess redur.dancy EDG or an independent power source.
However, at a two (or more) unit site where the EDGs meet the AAC source excess redundancy criterion, one intertie circuit between units is acceptable provided it is separately connectable to each safety (EDG) bus in both units.
This follows fron the application of the above criteria and the assumptions-that must be taken that an SB0 can occur in either unit, and that the single failure-in the NB0 unit can be on either one of its EDGs or on its respective safety.
bus.
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-7 2.2.2 Proposed AAC Power Source The AND Station is a two unit site with two dedicated EDGs per unit. The pro-posed AAC power source for the blacked out unit is a cross-tied EDG from the NB0 ur.it.
The licensee's submittal states that the EDG/AAC source is available within I hour of the enset of the SB0 event, and has sufficient capability to provide power for safe shutdown of both units for a 4-hour SB0 duration. The licensee's submittal stated that load shedding is required in the NB0 unit in order to achieve this EDG capability and has, therefore, proposed a load management scheme to power the needed equipment for safe shutdown operation of the blacked-out unit erd NB0 unit.
No details of the load shedding scheme were provided. The steff has reviewed the licensee's response (see attachment 1 for det6ils) and has concluded that the load shedding scheme will result in the degradation of safe shut-down capability of the NB0 unit and the excess ct.pacity made evailable by load shedding cannot be credited as an AAC source for the tlacked cut unit. Therefore, the licensee's proposed actions do not conform to the guidance on the use of existing EDGs on the basis of excess capacity as an AAC powt.r sources as documented in the 10 CFR $50.63, RG.I.155 PositionC.3.3.5,NUMARC87-00section2.3.1(3),andNUMARC87-00 Supplemental Questions and Answers dated December 27,19E9.
Af ter reviewing the SAIC TER and the licensee's proposed actions for crediting existing NE0 unit EDGs as an AAC source, the staff has determined that the pro-posed AAC source for ANO-2 does not meet the requirements of 10 CFR 550.63.
Recommendation: The licensee should undertake further measures 'such as pro-l viding a separate AAC power source or a coping analysis which shows that the l
plent can cope with and recover from an SB0 for the required duration l
independent of AC power.
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. 2.3 Station Blackout Coping Capability The characteristics of the following plant systems and components were reviewed to assure that the systems have the availability, adequacy and capability to achieve and r.eintain a safe shutdown and recover from an SB0 for a 4-hour coping duration.
2.3.1 Condensate Inventory for Decay Heat Removal l
The licensee's submittels states that 62,266 gallons of condensate are required to remove decay heat from the reactor et ANO Unit 2 during a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> $80 event.
The minimum condersate storage tank (CST) capacity corresponding to minimum level per Technical Specifications for the unit is 160,000 gallons.
After reviewing the licensee's submittal and the SAIC TER, the staff agrees with the licer.see's assessment that the plant has adequate condensate inventory for a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> 5B0 duration.
In addition, the excess inventory available in the CST is available for 500 recovery.
However, there is no assurance that the condensate inventory can be used for the full 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> duration because the decay heat removal system would not continue to operate if the Class IE batteries are depleted (See Section 2.3.2) after one hour since the charging source for the battery (the AAC power) source does net meet the requirements of 10 CFR 550.63.
I 2.3.2 Class IE Battery Capacity The licensee stated that a battery capacity calculation was performed to verify that the Class IE batteries have sufficient capacity to meet the SB0 loads for one ',our.
It is assumed that the AAC power source energizes a battery charger associated with one division within one hour.
l Based upon tne staff review, the licensee's proposed AAC power source does not i
meet the requirerents of 10 CFR $50.63 and, therefore, cannut be assumed to power a battery charger within ore hour.
In accordance with NUMARC 87-00
9 Supplemental Questions / Answers, the licensee should ensure that the normal battery backed plant fronitoring and electrical system controls rtrain opera-tional for successfully ccping with and recovering from a SB0 event. The iicensee has not demonstrated that the Arkanshs Unit 2 batteries have sufficier.1 capacity to last for the full 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> SB0 duration withcut battery charging.
Also, the licensee has not provided an acceptable AAC source that meets the requirement of 10 CFR 50.63 for charging the batteries, Recora ndation:
The licensee should provide for ANO-2 an acceptable AAC power source to power battery charging for et least ore division or provide a battery that has suf ficient capacity to power all nero.a1 battery-backed nicnitoring and electrical systems and controls for the requirtd 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> SB0 duration and i'ecovery theref rom.
2.3.3 Compicssed Air The licerne stated that no air opereted valves are relied upon to cope with a station bl6ckout for one hour.
The turbine drivtr> auxiliary feedwater (AFW) pump, atmospheric durtt valves (ADVs) are relied upon for decay heat renovel during an SBO.
ADVs are air operated and fail open upon loss of air. The block valves upstreau of ADVs are norrrally closed motor operated valves which are powered by EDGs.
The AFK flow control valves arc de motor operated valves.
The ADV block volves 6re equipped with handwheels that can be used to adjust the decay heat r elease rate tr.onually upon-loss of power.
After reviewing the licensee's proposal and the SAIC TEp., the staff agrees with SAIC assessment that the licensts: dces nut have an AAC source that meets the requirementsof'theSB0 rule (seeSection2.2.2above)whichpowers'the equipment for air make up capability to operate the ADV valves needed for decay heat removal.
Pecommendetion:
The licenste should provide an acceptable AAC source for.
l ANO-2 that nieets the SB0 rule and provices means for powering the equipment for air make up to operate the ADV velves, or provide alternete means for achieving
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l decay heat remeval during ar. SB0 event.
Whatever method is chosen, the licensee should siniulate the proposed procedure and provide the appropriate operator training to ensure the decay heat removal can be adequately maintained.
2.3.4 Effects cf Loss of Ventilation i
The licensee bas stated in his submittels dated April 23, 1989, and April 3, 1990, that reasonable assurance of the operability of SB0 response equipment in dominent areas of cor.cerns (DAC) including the control room, was assessed using Appendix F to blHARC 87-00 and/or the Topical Report.
However, the licensee in his submittal detec' July 7,1990, has indicated that he he,s made the decision thet the control room HVAC will be powered from the AAC power source during an SB0 event. The licenste stated that supplying ventilation in one control room results in sufficient eccling in the other control room via opening between the two control rooms.
The licensee stated that only one safety bus of Unit 1 sup-plies power to the Unit I control room venti 16tico system.
Hence, in the case of Unit 2 being the blacked cet bnit and applying single failure on the EDG which supplies thc HVAC systera, will result in a loss of ventilatict of both control rooms for the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of an SB0 event.
Since the prcposed AAC power source does not meet the SBC rule requirements, unless an acceptable AAC source thet meets the SB0 rule is provided to power the cuntrol room HVAC in unit 2, the SB0 equipr.ent operability in unit 2 control room cannot be assured.
In-codition, the licensee rieeds to evaluate the effects of loss of HVAC in the Unit 1(NB0 unit)controlroom.
The licensee during the telephone conference of August 10.-1990, indicated that the nominc1 operating temperature was used in the calcul6 tion of the hebt up analysis of the control roorr.
However, the control room heat-up analysis should be r.ade by using the maximum bounding temperature.
Reccmmendation:
The licensee should provide for ANO-2 an accepte.ble AAC source th6t provides control roora HVAC systems or provide en analysis using the m6xtr.,um bounding centrol room temperature (Technical specification limit) that
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- vcrifies the operability of SB0 equipment will not be degraded for the required SB0 duration end recovery therefrom.
In additicn the licensee should evaluate the effects of loss of HVAC on the operability of the control room equipment in unit 1.
2.3.5 Containment Isolation
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The licensee stated that the containment isolation valves (CIVs) which must be capable of being closed or operated under SB0 conditions can be positioned (with indication) independent of the prefctred and blacked out unit's Class IE 1
power supplies.
However, the staff has identified two additional CIVs (CV 5047-1 and CV 5648-2) that require closure capability to ensure appropriate containment integrity.
The licensee should address the closure capability of these valves in the appropriate procedures.
Reconsnendation: The licensee should review the operational features of the above listed valves CV-5047-1 and CV-5648-2 and ensure that the SB0 procedures provide the means for proper control of these valves to assure contair. ment integrity for the requircd SB0 duration or provide rationale for their exclusico, 2.3.6 Reactor Coolant Inver. tory The licer.ste has stated that the ability.to maintain adequate reactor coolant system (RCS) inventory to ensure that the core is covered has been assessed for one hour, and after one hour the proposed AAC source powers the RCS makeup systen:s. However the proposed AAC source does not qualify as an AAC source based on excess capacity and, therefore, the assumption that AAC power source will powcr the necessary make-up systems to maintain adequate RCS inventory is invalid.
Recomendation:
The licensee should provide an acceptable AAC power source of sufficient capacity and capatility to provide power to the make-up systems and
i its supporting systems to maintain adequate RCS inventory or provide an essessraent that there will be adequate RCS inventory to ensure continued core cooling for the required SB0 duration and recovery therefrom.
2.4 procedures and Training The licensee has stated that the appropriate procedures have been reviewed and
- modified, furthermore, the licensee has stated that the changes will be implemented by the end of refueling outage number 8 (October 23,1991).
Although the licensee has completed appropriate procedures, additional procedures may be required cepending upon the licensee's proposed resolution of the AAC power source-(see section 2.2.2) issue.
The troposed procedure modifications indicated above were not reviewed, but the staff expects the licensee to r.;aintain and implement these procedures including any others that may be requirtd as part of the revised response to ensure an appropriete response to an SB0 event. Although personnel treining requirements for m. SB0 response were not specific 611y addressed by the liter.see's submittal, the staff expects the licensee to implement the appropriate training to ensure an effective response to the SBO.
2.5 Proposed Modifications:
The licensee stated that modifications will be necessary to cross-tie the ANO Unit I and 2 safety buses in order to provide the AAC power source to the blacked-out unit. The E0P' procedure would require modification to align the i
breekers, load shedding and coordination of activities between each unit's-operators. The AAC cross-tie acdifications are planned to be completed by the.
end of refueling outage No. 10 depending on NRC response.
_ Recon:mendation:
The licensee's proposed AAC for ANO-2 does not conform to the l
SB0 rule requiremen's, and therefore, the licensee _should consider the addition j
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of an independent AAC source. The licenset should provide a full description including the nature and objectives of the required modificaticos to meet the SB0 rule and a proposed schedule for implementation.
2.0 Ouality Assurance (QA) ar.d Technical Specificetions (TS)
The licensee did not provide any information regarding QA programs and TS for SB0 equipment to the guidance of RG 1.155, Appendices A & B.
t Furtherrcre, technical specifications (TS) for the SB0 equipment are currently beir,g considered generically by the NRC in the context of the Technical Specification Improveraent Progren and remains an open item at this time.
However, the staff woulc expect thet the plant procedures will reflect the appropriate testing and surveillance recuirements to ensut e the operability of the necessary SB0 equipment.
If the staff later determines that a TS regarding the SB0 equipment is warranted, the licensee will be notified of the implemente-tior, requirements.
Recura ndation:
The licensee should verify thet the SB0 equipment is covered by cn appropeiate QA progr6m consistent with the guidance of RG 1.155.. Further, this evalu6 tion should be docurented as part of the package supporting the SB0 l
rule response.
2.7 EDG Rellibility Frogram The licensee's submittal did not specifically address the EDG reliability program consistent with the guidance of RG 1.155, Section 1.2.
It is the staff's position that an EDG relie.bility program should be developed in I
accordance with the guidance of RG 1.155, Section 1.2.
Recommendation:
The licensee should implement an EDG n11 ability program which meets the guidance of RG 1.155, Section 1.2.
If an.EDG-reliability program currently exists, then it shoulo be evalueted and adjusted in
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.. 'I accordance with RG 1.105.
Confirm 6 tion that such a program is in place or will be implenented should be included in the documentation supporting the SB0 submittels that are to be maintained by the licensee, j
2.8 Scope of Staff Review Thestationblackoutrule(10CFR50.'63)requireslicenseestosubmitaresponse containing specifically defined information.
It also requires utilities to have baselint assumptions, analyses and related information used in their coping eveluation available to ilRC.. The staff and its contractor (SAIC) did not perform a detailed review of the proposed procedure modifications which are scheduled for 16ter implementation efter the nodifications that could result f rom the staff recott,;endations it this SER. Therefore, based on our review of-the licensee SB0 submittal and FSAR, we have identified the following areas for focus in any follonup inspection or assessment that c6y be undertaken by the NRC to further verify conformance with the SB0 rule.
a.
Hardware and procedural iaodifications, b.
500 procecures in accordance with RG 1.155, Position 3.4, and NUMARC E7-00, Section 4, 3
c.
Oper ator stuf fing and training to follow the identified actions-in the SB0 procedures, d.,
EDG reliability program meets es a minimum the guidelines of RG 1.155, e.
Equipment and components required to cope with an SB0 are incorporated in a QA progrum that neets the guidance of RG l
1.155, Appendix A, and f.
Actions tcLen pertaining to the specific reccarendations noted-6bove in this SER.
. 3.0 $Uf: MARY AND CONCLUSIONS:
The steff has reviewed the licensee's response to the station blackout (SBO) rule (10 CFR 50.63) and the Technical Evaluation Report (TER) prepared by the staff'sconsultant,ScienceApplicationsInternationalCorporation(SAIC).
Based on our review, we find that the ANO-2 does not conform with the SB0 rule and the guidance of RG 1.155, and, therefore, recommend that the licensee reevaluate the areas of concern that have been identified in this SER.
Guidance for the licensee to review and implerrent the staff's reconnendations is provided in RG 1.HS, NUMARC 8'/-00 and the' supplementary guidance (flVMARC 07-00 Supplementary Questions / Answers; NUMARC E7-00 Major Assumptions) dated December 27, 1989, which was itsued to the industry by NUMARC on January t.,
2950. The staff's concerns that are identified in this SER should be addressed by the licensee, and a revised respense submitted to the NRC within 60 days.
The staff has not approved the use of existing EDGs as an AAC source on the tesis of excess capacity rr.ade available by load shedding.
The licensee is, therefore, expected to ensure that the baseline assumptions of NUMARC 87-00 are applicable to the ANO plant. Also, the licensee is expected to document all andlybls add relatLd informdtior, and to maintain these available for NRC review.
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ATTACHMENT 1 t
SAIC-90/1377 TECHNICAL EVALUAT!0N REPORT ARKANSAS NUCLEAR ONE. UNIT 2 l
STATION BLACK 0UT EVALUATION l
e 5
.l Science Applications IntemationalCorparation i
An Employee Owned Company i
Final September 17, 1990.
i Prepared for:
U.S. Nuclear Regulatory comission Washington, D.C. 20555 Contract NRC-03-87-029-
-Task Order No. 38 1710 Goodridge Drive. P.O. Box 1303, McLean. Virginia 22102 (703) 82b4300 crv src on:e, aum ew se cwa sc e. on.sr sms.*, w w, ran a,ms o.. nor www row a ro. se oee swre an im zumy D g.
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TABLE OF CONTENTS Section P.Agt
1.0 BACKGROUND
I 2.0 REVIEW PROCESS....................
3 3.0 EVALUATION...........-...........
6 1
3.1 Proposed Station Blackout Duration........
6 3.2 Alternate AC (AAC) Power Source.........
9 3.3 Station Blackout Coping Capability........
13-3 3.4 Proposed Procedures and Training.........
20 l
3.5 Proposed Modifications.......~.......
21 3.6 Quality Assurance and Technical Specifications..
21
4.0 CONCLUSION
S......................
22
5.0 REFERENCES
25 I
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.q 1
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TECHNICAL EVALUATION REPORT ARKANSAS NUCLEAR ONE, UN!Y 2 STATION BLACK 0UT EVALUATION
1.0 BACKGROUND
On July 21, 1988, the Nuclear Regulatory Commission (NRC) amended its regulations in 10 CFR Part 50 by adding a new section, 50.63, " Loss of All Alternating Current Power" (1). The objective of this requirement is to assure that all nuclear power plants are capable of withstanding a station blackout (SBO)-and maintaining adequate reactor core cooling and appropriate containment integrity for a required duration. This requirement is based on information developed under the commission study of Unresolved Safety Issue
~
A-44, " Station Blackout", (2-6).
The staff issued Regulatory Guide (RG) 1.155, " Station Blackout," to provide guidance for meeting the requirements of 10 CFR 50.63-(7).
Concurrent with the development of this regulatory guide, the Nuclear Utility Management and Resource Council (NUMARC) developed a document entitled. " Guidelines =and j
Technical Basis for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors," NUMARC 87-00 (8). This document provides detailed guidelines and procedures on how to assess each plant's capabilities to comply with the SB0 rule. The NRC staff reviewed the guidelines and analysis methodology in NUMARC 87-00 and concluded that the NUMARC document provides an acceptable guidance for addressing the 10 CFR 50.63 requirements.
The application of this method results in selecting a. minimum acceptable SB0 duration capability from two to sixteen hours depending on the plant's characteristics.and vulnerabilities to the risk from station blackout. The plant's characteristics affecting the required coping capability'are:
the redundancy of the on-site emergency AC power-sources, the reliability of on-site emergency power sources, the frequency of loss of off-site power (LOOP),. and the probable time to restore off-site power.
In order to achieve a consistent systematic response from licensees to the SB0 rule and to expedite the staff review process,.NUMARC developed two-1 w
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generic response documents. These documents were reviewed e.nd endorsed by the NRC staff (9) for the purposes of plant specific submittals.
The documents I
are titled:
1.
" Generic Response to Station Blackout Rule fo" Plants Using l
Alternate AC Power," and 2.
" Generic Response to Station Blackout Rule for Plants Using AC i
Independent Station Blackout Response Power."
A plant specific submittal, using of the above generic formats, provides l
only a summary of results of the analysis of the plant's station blackout coping capability.
Licensees are expected to ensure that the baseline assumptions used in NUMARC 87 00 are applicable to their plants and to. verify i
the accuracy of the stated.results.
Compliance with the SB0 rule requirements is verified by review and evaluation of the licensee's submittal and: audit review of the supporting documents as necessary.- Follow up NRC inspections assure that the licensee has implemented the necessary changes as required to meet the SB0 rule.
In 1989, a joint NRC/SAIC team headed by an NRC staff member performed audit reviews of the methodology and documentation that support the licensees' submittals for several plants. These audits revealed several deficiencies which were not apparent from the review of the licensees' submittals using the agreed upon generic response format.
These deficiencies raised a generic t
question regarding the degree of,the licensees' conformance to the requirements of the SB0 rule. To resolve this question, on January 4,1990, NUMARC issued additional guidance as NUMARC 87-00 Supplemental s
Questions / Answers (10) addressing the NRC's concerns regarding the deficiencies. NUMARC requested that the licensees-send their supplemental
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responses to the NRC addressing these concerns by March 30, 1990, i
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l 2.0 REYl s PROCESS The review of the licensee's submittal is focused on the following areas consistent with the positions of RG 1.155:
A.
Minimum acceptable SB0 duration (Section 3.1),
B.
SB0 coping capability (Section 3.2),
C.
Procedures and training for SB0 (Section 3.4),
D.
Proposed modifications (Section 3.3), and E.
Quality assurance and technical specifications for SB0 equipment (Section3.5).
For the determination of the proposed minimum acceptable 580 duration, the following factors in the licensee's submittal are reviewed:
a) off-site power design characteristics, b) emergency AC power system configuration,' c) determination of the emergency diesel generator (EDG) reliability consistent' with NSAC-10B criteria (11), and d) determination of the accepted EDG target reliability.
Once these factors are known, Table 3-8 of NUMARC 87-00 or Table 2 of RG 1.155 provides a matrix for. determining the required coping.
1 duration.
For the 580 coping capability, the licensee's submittal is reviewed to assess the availability, adequacy and capability of the plant systems and components needed to achieve and maintain a safe shutdown condi. tion and recover from an SB0 of acceptable duration which is determined above.
The review process follows the guidelines given in RG 1.155, Section 3.2, to I
assure:
a.
availability of sufficient condensate inventory.for decay heat' 5
- removal, i
3
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b.
adequacy of the class IE battery capacity to support safe shutdown, c.
availability of adequate compressed air for air-operated valves j
necessary for safe shutdown, d.
adequacy of the ventilation systems in the vital and/or dominant areas that include equipment.necessary for_ safe shutdown of the
- plant, i
e.
ability to provide appropriate containment integrity, and f.
ability of the plant to maintain adequate ~ reactor coolant system inventory to ensure core cooling for the required coping duration.
The licensee's submittal is reviewed to verify _ that required procedures (i.e., revised existing and new) for coping with SB0 are identified and that appropriate operator training will be provided.
The licensee's submittal for any proposed modifications to emergency AC sources, battery capacity, condensate capacity, compressed air capacity, appropriate containment integrity and primary coolant make-up capability is reviewed. Technical specifications and quality assurance set forth by the licensee to ensure high reliability of the equipment, specifically_ added or 1
assigned to meet the requirements of the SB0 rule, are assessed for their adequacy.
The licensee's proposed use of an alternate AC power source is reviewed to determine whether it meets the criteria and guidelines of Section 3.3.5 of RG 1.155 and Appendix B of NUKARC 87 00.
l r
This SB0 evaluation is based on a review of the licensee's submittals dated April 13, 1989 (12), April 3, 1990 (14),_and July 17, 1990 (13), a telephone conversation between the NRC/SAIC and the licensee on August 10,.
1990, and the available information in the plant-Updated FinaliSi.fety Analysis Report (UFSAR) (15). -The evaluation does not include a concurrent site audit-
' 4 rt s
.,1 a,
f review of the supporting documentation.
Such an audit may be warranted as an additional confirmatory action.
This determination would be made and the audit would be scheduled and performed by the NRC staff at some later date.
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i 3.0 EVALUATION 3.1 Proposed Station Blackout Duration Licensee's submittal The licensee, Entergy Operations, Inc. (formally Arkansas Power and Light Company), calculated (12-14) a minimum acceptable station blackout-duration of four hours for the Arkansas Nuclear One (ANO),. Unit 2.
The licensee stated that no modifications are necessary to attain this proposed coping duration.
The plant factors used to calculate the proposed SB0 duration are:
l.
Off-site Power Design Characteristics I
i The plant AC power design characteristics group is "Pl" based on:
a.
Estimated frequency of LOOPS due to extremely severe weather (ESW) which places the plant in ESW Group "1,"
l b.
Estimated frequency of LOOPS due to severe weather (SW)-which.
I places the plant in SW Group "2,"
and j
.I Independence of the plant off-site power system characteristic c.
of "11/2," and d.
Expected frequency of grid-related LOOPS of less than one per 20 years, 1
2.
Emergency AC (EAC) Power Configuration Group i
The EAC power configuration group at Arkansas Nuclear One is "C."
Each unit is equipped-with two emergency diesel generators..One L
6
-lq l
l
l emergency diesel generator per unit is necessary to operate safe shutdown equipment following a LOOP.
t i
3.
Target Emergency Diesel Generator Reliability The licensee selected a target EDG reliability of 0.95 based on having a unit average EDG reliability for the last 100, 50, and 20 i
demands of greater than 0.95, 0.94, and 0.90 respectively, consistent with NUMARC 87-00.
The licensee submittals do not address a diesel generator reliability program incorporating the five elements discussed in RG--
1.155.
However, the licensee does recognize that the target reliability is to be maintained (14).
The methodology of maintaining the target is tied.to the resolution of Generic Safety Issue B 56.
i q
r Review of Licensee's Submittal Factors which affect the estimation of the'SB0 coping duration are: -the
- L independence of the offsite power system grouping, the estimated frequency of LOOPS due to ESW and SW conditions, the expected frequency of grid related LOOPS, the classification of EAC.-and.the selection of EDG target reliability.
The licensee's estimation of the frequency of l
LOOPS due to ESW condition conforms with that given'in Table 3-2 of' NUMARC 87-00.
I i
Using Table 3 3 of NUMARC 87-00, the expected frequency of LOOPS at ANO j
due to SW condition is estimated to be "0.0341" or *0.0072" placing the site in an SW group "4" or "2" depending on the site having offsite power'
~
transmission lines either on one or multiple rights-of-way, respectively, i
The licensee's submittal stated that the plant is in SW group "2" indicating that the site has power transmission. lines on multiple rights-of-way. A review of the Unit 2 UFSAR indicates that the site could be considered to have transmission lines on multiple rights-of-way.
7 d
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1 2
Our review of the ANO Unit 2 UFSAR, combined with information gained from the licensee during a phone' conversation on August 10, 1990, indicates that the independence of offsite power for ANO is "II/2" based on:
1.
All offsite power sources are connected to the' plant through two electrically connected switchyards.
i 1
2.
There are two emergency safety feature. (ESF) divisions in each unit, jl and both divisions are normally powered from the unit auxiliary transformer (UAT).
3.
The UAT for each unit is connected to the unit main generator.
4.
Upon loss of the main generator, a fast. automatic transfer occurs to one of two start-up transformers.
Unit ? would normally transfer to ST3 (see Figure 1); ST3 is powered by the Aui6 Transformer which can
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take power from either the 500 kV or 161 kV buses; 5.
Should the selected start-up transformer fail,. load can be manually transferred to the backup start-up transformer, which is.normally ST2.
ST2 can support the safe shutdown loads of one unit plus the design basis accident (DBA) loads of the other unit.
With regard to the expected frequency of grid _related LOOPS at the site, we can not confirm the stated results.
The available. information in-NUREG/CR-3992 (3), which gives a compendium of information on the loss'of-offsite power at nuclear power plants in U.S., indicates.that ANO did not have a grid-related LOOP up to 1984.
In the absence of'any contradicting information, we agree with the licensee's: statement t' hat the frequency of grid-related LOOPS is expected to be less than one per 20 years.
Our review of the ANO Unit 2 UFSAR indicates that therlicensee has-properly classified the EAC classification as "C" based on the facts that-there are two emergency AC power. supplies for each -unit and one emergency AC supply is necessary to operate safe shutdown equipment.for each unit.
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The licensee's determination of target emergency diesel generator
{
reliability is in iccordance with RG 1.155 and NUMARC 87-00. lAlthough the need to maintain the reliability-of the EDGs is recognized by the licensee, no specific program was committed to. We take the licensee statement to maintain target reliability as a commitment to establish a-j reliability program consistent with resolution of'the Generic Safety' Issue B 56.
Based on the above, the AC power design characteristics of the ANO site is "Pl" with a minimum required SB0 coping duration of four hours.
I 3.2 Alternate AC (AAC) Power Source Licensee's Submittal t
The licensee stated that the AAC power source at ANO will-be an emergency-AC power source from the non-blacked out unit which meets the criteria specified in Appendix B to NUMARC 87-00 and the assumptions in_Section.
q 2.3.1 of NUMARC 87-00 (12).
The' proposed AAC configuration-at ANO is j
shown in Figure 1.
The licensee stated that with this configuration,-
1 including the proposed cross-tie modification,' any one of the blacked lout unit's emergency buses can be energized manually from either of the-emergency buses of the non-blacked out unit.
The AAC power source will be available within one hour of the onset of an SB0 event and has
.l sufficient capacity to operate necessary safe shutdown systems-for both.
units. A load management scheme is being developed for th' AAC power e
source; the scheme is to be submitted to the NRC sometime after mid-
, September of 1990 (14).
l 4
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Arkansas Nuclear One Units One
& Two Simplified Single Line Diagram for Station Blackout To Mayflower To Morrillon East
[~g.L-To Fort Smith g
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t Review of Licensee's Submittal The licensee's proposed AAC power source configuration (Figure 1).
conforms to a variation of an acceptable configuration provided in NUMARC 87-00 Supplemental Questions / Answers under Question C.1 (10).
The AAC power source, one of the site EDGs, meets.all the required criteria in Appendix B of NUMARC 87-00 except for the following cases:
o Paragraph B.9 of Appendix B states, "the AAC power source shall be-
... capable of maintaining voltage.and frequency within limits.-
consistent with established industry standard that will not degrade the performance of any shutdown system or component. At a multi-unit _ site, except-for 1/2 Shared or 2/3 emergency AC power configuration,-an adjacent unit's Class IE power source may be~used' as an AAC power' source for the blacked-out' unit'if it is capable of powering the required loads at both units."
1 Paragraph ~ B.12 of Appendix B states, ".... the 'AAC system 'shall be i
o demonstrated by initial test to be capable of powering required q
shutdown equipment within one hour of a station blackout event."
I The guidance.on the use of existing EDGs as AAC. power. sources at multi-unit sites is documented in RG 1.155, Section 3.3.5,-NUMARC-87-00, Section 2.3.l(3), NUMARC 87-00 Supplemental Questions / Answers,- Quest'ons-3.4 and B.3, and further detailed-in References 16, 17,'and 18.1 In addition, the SB0 rule states that at multi-unit-sites where the combination of EAC power sources ' exceeds the minimum ~ redundancy requirements for safe shutdown (non-DBA) of all units, the' remaining EAC sources may-be used as AAC sources' provided that they meet the' applicable requirements, l.
1 The rule statement requires ' minimum redundancy.' This means that in order for an EDG to qualify as an AAC. source there <must' be an EDG a
available in the NB0 unit in addition to the' number of EDGs required to'
.1 j
meet the minimum EDG redundancy r~equirement for ' powering a' normal safe 1
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11 3
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shutdown loads following a LOOP event.
Thus, the EDGs in a two-unit ~ site with two dedicated EDGs per unit would not_ qualify as AAC sources.
Two-EDGs per unit would meet only the minimum redundancy requirement, and-there'is no excess EDG.
However, there are some plants at multi-unit ~ sites which have EDGs that just meet the minimum redundancy but each EDG has sufficient capacity to.
power all the normal LOOP loads of the NB0 unit and also has sufficient excess capacity to power the required safe shutdown loads of the SB0 4
unit. Recognizing the' existence of this type of situation, the staff has interpreted the 'if teral' excess EDG redundancy requirement of the 580 q
rule to allow large capacity EDGs to qualify as AACL sources,'provided other applicable requirements are met.
In order to take credit for this interpretation, the NRC staff's basic:-
position has been (16, 17, and-18) that:
l 1.
no action should be taken that would exacerbate the already-l difficult situation in the NB0 unit. Any_ actions that;-make operator-l tasks more difficult such as load switching or disablement of.
information readouts or alarms in the control. room areLalso I
considered to be a degradation of-normal safe shutdown capability for LOOP in the NB0 unit. And,
- I 2.
excess capacity of the EDG being designated as an AAC' source should' not be the capacity made available by. shedding orlnot powering 1
l normal safe shutdown loads in the-NB0 unit.
Examples'of such loads l
are: motor driven auxiliary feedwater pumps; heating,. ventilation and air conditioning loads; the power supply of. the plant computer; one or more sets of redundant instrumentation; etc. ;The shedding of-such loads constitutes degradation of _the normal safe' shutdown -
i capability of the NB0 unit.
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It is not in the interest of safety to'reduceLthe; capability to, handle Lr various eventualities in one unit for the 'purposeiof meeting the SB0 rule'-
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in another unit.
Each unit must meet the SB0 rule on its own merits-without reducing another unit's capability to respond to its own-potential problems.
1
-1 The excess capacity of the EDG in'the NB0 unit that qualifies it as an AAC source is, therefore, 'only that svallable capacity within the normal continuous rating but above.the EDG load represented by the complete contingent of safety related and non-safety related loads normally expected to be available for 'the LOOP condition.!'
In its SB0 supplemental information' submittal (13);the licensee stated that load shedding is required to ensure that selected SB0 equipment in i
the blacked out unit could be powered from one ~ of the EDGs' in the NB0 unit. During a telephone conversation on. August 10, 1990,- the licensee was asked by the staff to explain its load management scheme'and how tha't differs from the guidance.
The licensee stated that-since no conclusive' I
determination had been made yet it could not supply the requested, information at that time.
Our review of the Unit 1 UFSAR regarding the required LOOP. and SB0 loads indicates that the each EDG at Unit I does not'have sufficient capacity to meet the above guidance without a load shedding. scheme. 'If these-l loads were.not shed, the AAC power source would;not have sufficient capacity to power the selected equipment-needed for safe-shutdown-operation of the blacked out unit. -Therefore, the licensee's proposed AAC power source does not conform to the requirements of the SB0 rule, l
3.3 Station Blackout Coping Capability-The plant coping capability for the required duration of four h6urs is assessed based on the following.results:
13 e
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-- --. ~ ~. -
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1.
Condensate Inventory for Decay. Heat Removal-Licensee's Submittal' The licensee's submittal (12) stated that 62,268 gallons of condensate are required to. remove decay heat from the' reactor at ANO.
Unit'2 during a 4-hours SB0 event. The~ minimum condensate storage tank (CST) level per technical specifications is 160,000 gallons.,
Sufficient condensate inventory exists for decay heat removal during a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> SB0 event.
i Review of Licensee's submittal
.(
We performed' a calculation of the required condensate inventory based on NUMARC 87-00.
Our results confirmed.the licensee's: stated.
values and the fact that sufficient condensate inventory exists for decay heat removal during a four hour SBO. event. 'However, therelis no assurance that the decay heat' removal (OHR) systems at ANO Unit 2 1
would continue to operate if the Class IE batteries are depleted.
It is unknown how long the batteries are expected tollast (see item 2 below). The licensee needs to verify that the DHR systems'will remain operational and controllable' after the batteries are -
depleted, if the depletion time.is less than four hours.-
l 2.
Class.1E Battery capacity.
1
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l Licensee's Submittal The licensee stated that a battery capacity calculation hasLbeen' j
performed to verify that the class lE batteries'have. sufficient.
capacity to meet the station blackout loads for one hour.
'14 L
i Review of Licensee's Submittal I
According to the UFSAR (15) the. class IE batteries are sized to provide power for an eight hour emergency duty cycle.
Howevers the j
duty cycle' described in the UFSAR includes significant load shedding. The.UFSAR indicates the loads that are shed include:.
computer and peripherals (after one hour), two of four reactor i
I protection and ESF. channels (after two hours), and'other-loads..To j
conform with the guidance provided in.NUMARC 87-00 Supplemental.
q Questions / Answers, the licensee needs to ensure that the normal battery-backed plant monitoring and electrical system controls' j
remain operational for successfully coping with and recovering from an SB0 event.
The licensee has verified that the class lE batteries have sufficient capacity to meet t!'* SB0 loads, for one hour.u After one.
hour, the AAC ' power source will be-available and power the. equipment j
necessary, including the needed battery chargers,'to cope with an SBO.
However,.our review indicates that the proposed AAC power source does meet the requirements of the SB0 rule. 'Therefores the-licensee needs to certify that the battery load shedding stated in
-the UFSAR is consistent with the guidance provided.in.NUMARC 87-00 Supplemental Questions / Answers, or provide.an acceptable AAC power t
source.
I 3.
Compressed Air Licensee's Submittal The -licensee stated that no air-operated valves $re relied upon to cope with a station blackout for one hour.
-\\
15
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Review of Licensee's Submittal:
Our review of the UFSAR indicates that all: safety 'related air-operated valves were found to go to the safe position upon a loss of
~
air.
The valves-required to operate in order to cope with an_SB0 I
are those associated with the auxiliary feedwater (AFW)_and
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atmospheric dump systems. The AFW control valves are both' DC and' AC powered motor operated valves..The atmospheric dump valves (ADVs) j are air operated and_the'y fail open upon loss offair. The UFSAR l
indicates that the block valves upstream of theLADVs are normally--
closed MOVs which are powered by class IE power._ Since the AAC power source does not conform to the requirements:of the SB0 rule, neither compressed air nor electrical power are available. -Without i
compressed air or electrical power, the secondary steam would.have to be released to the atmosphere either by the manual manipulation of the ADV' block valves or by the ' automatic actuation of the main steam relief valves.
The licensee needs to provide an explanation-of the method it intends to use to remove'decaycheat.
If manual' operation of the ADV block valves is utilized, concerns related to the habitability of.the area.of the valves,~ communication with the control room, procedures to operate the system _in this manner, and.
l operator training arise and need to be addressed. Alternatively, the licensee needs to provide an AAC power source to support the-operation of the decay heat. removal system.
l 4.
Effects of Loss of Ventilation I
l Licensee's Submittal l
l The' licensee stated (12) that during an SB0 event no heating,_
ventilation and air conditioning-(HVAC) system's would'be.available to the following dominant areas of concern:<
16 m
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Emergency'Feedwater (EFW). pump room Primary make-up pump rooms
. Service water pump structure.
Control room c
Room 2091 (DC Elec. Equip.)
Room '2099 (DC Elec. Equip.)
I In a subsequent submitta.1 (13) the licensee stated that the control l
room HVAC will be powered by the AAC' power' source during an.SBO.
The licensee also stated it has performed a scoping analysis.which -
indicates that the Unit 2 LOCA/HELB containment temperature profile
]
envelops the SB0 condition.
Reasonable assurance of the operability of station black out t
response equipment in DACs was assessed by the licensee using.
Appendix F to NUMARC 87-00 and/or the Topical-Rtport as well is.
analyses previously performed.
f l
Review of Licensee's submittal t
~
The information provided by.the licensee and'that available inithe plant UFSAR is insu Uicient to make a judgement regarding the correctness of the licensee's stated results. The licensee only provided the final' steady-state temperatures for the EFW' pump room:
(158 F) and the control room (<l20'F).. No other informat' ion' is provided regarding other areas evaluated. Therefore, an audit.may.
i be required to confirm compliance.
During the telephone conversation on August 10, 1990, the licensee.
was asked to explain the selection of dominant areas of concern' -
The licensee stated that the analysis is stillhunder review' and it
.l was not ready.to discuss the' subject'.
IWith regard to the'controli room, the licensee stated that supplying ventilation to either, control room results in sufficient. cooling.in the other control room-via openings between the two control rooms. The. licensee claimed' J
17 i
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thatithasananalysisdemonstrating.thataventilatiEnsystemin either control room can cool both control rooms. 'The licensee indicated that the assumed control room temperature at the start of the analysis was not the maximum allowable' temperature by technical specifications; this would make the results of the licensee's l
l analysis mn-conservative.
t The licensee also added-that the Unit I control room HVAC'is powered from a single safety bus, while the Unit 2 controliroom HVAC=is powered from both trains of safety buses. Since the capacity'of the-AAC is not sufficient, when Unit 2 is the blacked:out unit, it is possible that'no control room HVAC would be available during an SBO' 4
event. Therefore, the licensee needs -to evaluate the : effects of loss of ventilation on knib control: rooms for the full fourL hour coping duration with an initial control room temperature' equal-to
.the maximum allowed by the plant--technicalispecifications..
5.
Containment -Isolation Li:ensee's Submittal i
l "he licensee reviewed the plant list of containmentcisolation val'ves (CIVs) to verify that valves which must be capable lof._b'eing ' closed or operated (cycled) under station blackout conditions can.be positioned (with indication) independent of the preferred and-blacked-out unit's class 1E power supplies.
The. licensee stated that no plant modifications are necessary to ensure that appropriate
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containment integrity.is provided under SB0' conditions.-
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Review of Licensee's Submittal An-independent review of the CIVs was; performed based on Table ~ 6.2-j 26 of the UFSAR for Unit 2.
After excluding those CIVs that conform; to'thecriteria,statedinRG.I.155,Section3.2.7,ithefollowing valves requiring closure capability were found:
18 j
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A.
Valve Status fail 111e
.Svstem-I 2CV 5647-1 N.O.
FAI 24" ECCS' I
2CV 5648-2 N.0..
FAl-24" ECCS' N.O. = Normally open 1
Containment sump suction FAI - Fails as is The licensee needs to address th9 closure of these valves ' n-i appropriate procedures.
6.
Reactor Coolant Inventory F
Licensee's Submittal
~
The 1.icensee stated (12) that the generic. analyses! listed in'Section 2.5.2 of NUMARC 87-00, which are applicable to. ANO Unit 2, were used to assess the plants ability to' maintain adequate reactor coolant '
l system inventory for one hour..The' licensee concluded that.the.-
t expected rate of. reactor coolant inventory loss'under SB0 conditions' j
does not result in core uncovering Lin an.SB0 event"of one' hour.
Therefore, make-up systems in additionito those currently available under SB0 conditions are not required.
Review of Licensee's Submittal i
Based on the licensee's statement:that reacto'r coolant: inventory loss under SB0 conditions'does not result-in core uncovering in.'an 3 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />, we interpret that reactor makeup;isJapplied,-starting at'one 1
hour.
Since the AAC power source does not conform to the requirements of the SB0 rule, no RCS make-up system will be -
j available.
Therefore the licensee,needsito have an analysis to demonstrate that the core is not uncovered.during the'four hour coping period, considering no makeup and a. leakage of 25 gpm per 19.-
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reactor coolant pump plus _the maximum allowable technical specification leakage.
3.4 Proposed Procedures and Training LI Licensee's Submittal i
The licensee stated that the following plant procedures have been reviewed per guidelines in.NUMARC 87-00, Section 4:
i 1.
AC power restoration, i
2.
Severe weather, and 3.
Station blackout response guidelir es..
The licensee listed the plant procedures.which fall in each-of above areas in the plant SBO. submittal.
The licensee stated that' procedures requiring changes'in the first two areas have been reviewed and modified l
if deemed necessary.
Procedure changes for station blackout response have been reviewed, and will be modified to-reflect the: changes resulting J
from the planned modifications.
All procedure changes are planned to be completed by the end of refueling outage number 8 forLUnit 2,~ estimated l
as October 23, 1991, subject to the NRC's approval of the modifications.
~
Review of Licensee's Submittal
-i We neither received or reviewed the affected procedures.
We cor. sider these procedures as plant specific actions concerning the required activities to prepare.for or to cope with an SB0 event. We believe'it is the' licensee's responsibility to revise and implement these procedures, p
as needed, to mitigate an SB0~ event,and to' assure that these procedures L
are complete and correct,-and that the associated' training needs are carried out accordingly.
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'A, 3.5 Proposed Modifications Licensee's submittal The licensee stated that modifications will be necessary to cross-tie the i
ANO Unit I and 2 safety buses in order to provide the AAC power source to.
the blacked-out unit.
The modification will include:
t 1.
Cabling between each unit's safety buses 2.
Unit I switchgear modifications to accommodate the cross-tie <
3.
Unit 2 switchgear modifications.to accommodate the cross-tie Procedure changes for both units to address breaker alignment, load shedding, coordination of activities, and realignment of power-suppl.ies when they become available; will be needed. The AAC cross-tie-modifications are planned to be completed by the end of refueling outages-No.10 at Unit I and No. 8 at Unit 2,, subject to the NRC's approval of the modifications.
Review of Licensee's Submittal i
The proposed cross-tie modification (see Figure 1) is consistent with an acceptable configuration provided in Appendix.C to NUMARC 87-00, j
Supplemental Questions / Answer:
Figure B of-Sample AAC Configurations.
This modification allows the licensee to power one of the emergency buses of the blacked out unit from'either of the EDGs of the non blacked out unit.
u 3.6-Quality Assurance and Technical Specifications:
l; The licensee's submittals do not document the conformance of the plant'.s L
SB0 equipment to the guidance of RG 1.155,. Appendices A and B.
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4.0 CONCLUSION
S 1
Based on our review of the licensee's submittals, a telephone j
conversation between NRC/SAIC and the licensee, and the information available l
in the plant UFSAR for Arkansas Nuclear One, Unit 2, we find the submittal l
does not conform with the requirements of the SB0 rule for the following l
1 j
reasons:
1.
Alternate AC Power Source The licensee's intended load shedding of the non-blacked out (NBO)L unit is not in conformance with the requirements of the.SB0' rule and-the guidelines provided in RG 1.155, NUMARC 87-00 Supplemental l
Questions / Answers, and References 16, 17, and 18..The load shedding j
scheme will result in the degradation of LOOP safe shutdown' q
capability of the NB0 unit. 'This excess capacity made available by
-)
load shedding could not be credited as an AAC source for' the blacked out unit (see the discussion under the AAC power. source-in Section 3.2).
Therefore, the AAC power source does not have sufficient capacity to power the selected safe shutdown equipment in the blacked out unit.
2.
Class IE Battery Capacity The plant UFSAR indicates that the class IE batteries will supply power for eight hours according to an emergency duty cycle'.. The emergency duty cycle includes significant load shedding after one hour.
Since the AAC power source cannot be assured to power the.
l battery charger, the licensee needs to ' etermine if the batteries d
d will support SB0 loads for four hours, consistent with the guidance provided in NUMARC 87-00 Supplemental Questions / Answers..
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Compressed. Air The licensee needs to provide the method it intends to use to remove decay heat,. assuming neither compressed air nor electric powerzis l
avail able. - If manual operation of the:ADV or ADV block valves is to' l
be required, the licensee needs to address related concerns as discussed in Section 3.3.
i 4.
Effects of Loss of Ventilation Insufficient information is available' in the UFSAR to verify the accuracy of the licensee's submittal. The conversation-with the licensee on August 10, 1990 resulted in the'following concern.
The '
licensee needs to evaluate the ~1oss of ventila' tion to both control rooms for four hours..This analysis is needed for the case where no EAC power source is available to the safety bus which powers the Unit I control room HVAC system.
In addition,.the licensee needs to utilize the maximum allowed control room temperature per technical specifications as the initial temperature.
5.
Containment Isolation 1
The licensee stated that all: containment-isolation valves which must be closed or operated for.an'SB0 event could be positioned with-indication independent of the preferred ~ and blacked out units class lE power supplies. Two. valves were identified which need'to be closed manually.
The licensee should verify that closure of these l
valves is included in: appropriate procedures.
6.
Reactor Coolant Inventory i
- I The licensee needs to evaluate the reactor coolant inventory with no -
make-up for four hours, considering a leakage of.25 gpm from each reactor coolant pump seal plus the maximum allowed technical J
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- s, specification: leakage. No make up capability can be' assumed due to.
lack of sufficient AAC capacity (see item 1.above),
7.
- Quality Assurance'and Technical Specifications The licensee's submittals do'not document the conformance of the plant's SB0 equipment to the' guidance of RG 1.155,. Appendices A and B.
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5.0 REFERENCES
1.
The Office of Federal Register, " Code of Federal Regulations. Title 10 Part 50.63," 10 CFR 50.63, January 1, 1989.
2.
U.S. Nuclear Regulatory Comission, " Evaluation _of Station Blackout Accidents at Nuclear Power Plants - Technical Findings Related To Unresolved Safety Issue A 44," NUREG-1032, Baranowsky, P. W., June 1988.
3.
U.S. Nuclear Regulatory Commission,'" Collection and Evaluation of -
Complete and Partial Losses of Off-site-Power at' Nuclear ~ Power. Plants,"'
NUREG/CR-3992, February 1985.
i 4.
U.S. Nuclear Regulatory Commission, " Reliability _ of Emergency AC Power System at Nuclear Power Plants," NUREG/CR-2989,.' July 1983.
~l 5.
U.S. Nuclear Regulatory Commission, " Emergency Diesel Generator Operat"ing i
Experience, 1981-1983," NUREG/CR-4347, December 1985.-
6.
U.S. Nuclear Regulatory Commission, " Station Blackout Accident Analyses (Part of NRC Task Action Plan A-44)," NUREG/CR-3226, May 1983.-
7.
U.S. Nuclear Regulatory Commission Office of Nuclear Regulatory Research, " Regulatory Guide 1.155 Station Blackout," August-1988.;
8.
Nuclear Management and Resources Council,.Inc., " Guidelines and Technical,
Bases for NUMARC Initiatives Addressing. Station Blackout.at Light Water.
Reactors," NUMARC 87-00,-November 1987.
9.
Thadani, A. C., letter to'W.H. 'Rasin of NUMARC, " Approval of NUMARC' DocumentsonStationBlackout(TAC-40577)/.0ctober7,1988-
. l
- 10. Thadani, A.
C., ' letter with attachment to A. Marion of NUMARC~, "PubliclyL
'l Noticed Meeting, December 27, 1989,." dated: January ~3,.1990,,(confirming "NUMARC 87-00 Supplemental Questions / Answers," December 27, 1987).-.
25
L gg..
l l
- 11. -Nuclear Safety Analysis Center, "The Reliability of Emergency Dieselt.
Generators at U.S. Nuclear Power Plants," NSAC-108, Wyckoff,. H.t, -
1-l September 1986.
Ti un
- 12. Campbell, T.
G.', letter to the Document Control Desk of U.S. Nuclear l
Regulatory Commission, " Arkansas Nuclear One, Unit 2, Docket Noa 50-868, i
Information Submittal for Station Blackout Rule.10CFR50.63," dated 2pril' 1
13, 1989.
13.
Fisicaro, J.
J., letter N. the document control Desk of U.S. Nuclear-Regulatory Commission, " Arkansas Nuclear One Units'l & 2, Docket Nos.
50 313 and 50-368, License Nos. DPR-51 and NPF-6, Station Blackout Issue - Supplemental Information," dated July, 17;'1990.-
- 14. Carns, N. S., letter N. the document control Desk of U.S. Nuclear Regulatory Commission, " Arkansas Nuclear One - Units 1 & 2,-Docket Nos.-
f 50-313 and 50 368, License Nos. DPR-51 and NPF-6, Station Blackout-l Issue - Supplemental Information," dated April 3,1990.
1
- 15. Arkansas Nuclear One,-Unit 2, Updated Final Safety Analysis Report.-
16.
Rosa, F., Memorandum to Docket Concerning Beaver Valley Un.its 1 and 2,
" Meeting Summary - Meeting of February 22, 1990,- on' Station Blackout Issues (TAC 68510/68511)," Docket Nos. 50-334 and.50 412, dated March 6,-
1990.
- 17. Tam, P. S., Memorandum for, " Daily Highlight-Forthcoming Meeting with NUMARConStationBlackout(SBO). Issues..(TAC'40577),"datedApril'25, 1990 (providing a Draft Staff Position Regarding Use of Emergency ACl Power Sources (EDGs) as Alternate AC (AAC) Power Sources-l dated April'24, 4
1990),
18.
Russell, W. T., letter to W. Rasin of NUMARC, " STATION BLACKOUT," dated June-6, 1990.
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