ML20064A972
| ML20064A972 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/24/1990 |
| From: | SCIENCE APPLICATIONS INTERNATIONAL CORP. (FORMERLY |
| To: | NRC |
| Shared Package | |
| ML20062C434 | List: |
| References | |
| CON-NRC-03-87-029, CON-NRC-3-87-29 SAIC-90-1370, TAC-68572, TAC-68573, NUDOCS 9010030250 | |
| Download: ML20064A972 (30) | |
Text
i ATTACHMENT 1 i
SAIC-90/1370 TECHNICAL EVALUATION REPORT NORTH ANNA POWER STATION UNITS 1 AND 2 j
STATION BLACK 0UT EVALUATION TAC Nos. 68572 AND 68573 SAIE Science Applications International Corporation An Employee Owned Company I
Final September 24, 1990 Prepared for: _
U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Contract NRC-03-87-029 Task Order No. 38 qQ(OC)3D PostOmce Box 1303,1710 Goodadge Dnve. McLean. Virginia 22102 (703) B214300
TABLE OF CONTENTS
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Section Eggt
1.0 BACKGROUND
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2.0 REVIEW PROCESS.......................................
3 3.0 EVALVATION...........................................
5 3.1 Proposed Station Blackout Duration..............
15 3.2 Alternate AC (AAC) Power Source.................
10-3.3 Station-Blackout Coping Capability...............
14 3.4 Proposed Procedures and Training................-
20 3.5 Propo sed Mod i fi cati ons..........................
22 3.6 Quality Assurance and Technical Specifications..
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4.0 CONCLUSION
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5.0 REFERENCES
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TECHNICAL EVALUATION REPORT l
NORTH ANNA POWER STATION UNITS 1 AND 2 STATION BLACK 0UT EVALUATION l
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1.0 BACKGROUND
t 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 I
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 'esource Council (NUMARC) developed a document entitled, " Guidelines and 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 NWRC 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 onsite emergency AC power sources, the reliability of onsite emergen::y -
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power sources, the frequency of loss of offsite power (LOOP), and the probable time to restore offsite 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
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l generic response documents.
These documents were reviewed and endorsed by the NRC staff (9) for the purposes of plant specific submittals.
The documents are titled:
1.
" Generic Response to Station Blackout Rule for Plants Using Alternate AC Power," and 2.
" Generic Response to Station Blackout Rule for Plants Using AC Independent Station Blackout Response Power."
3 A plant-specific submittal, using one of the. above generic formats, provides 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 the accuracy of the stated results.. Compliance wich the SB0 rule' requirements is verified by review and evaluation of the, licensee's submittal and audit review of the supporting documents as nece.sary.
Follow up NRC inspections assure that the licensee has implemenced the necessary changes as required to meet the SB0-rule, i
In 1989, a joint NRC/SAIC team headed by an NRC staff nember 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' sutwittals using the agreed upon generic response format. -These deficiencies raised a generic question regarding the degree of the licensees' conformanca to the requirements of the SB0 rule.
To resolve this question, on January 4, 1990,.
NUMARC issued additional guidance as NUMARC 87-00 Supplemental Questions / Answers (15) addressing the NRC's concerns regarding the deficiencies. NUMARC requested that the licensees send their supplemental responses ~to the NRC adoressing these concerns by March 30,'1990.
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l 2.0 REVIEW 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),
8.
SB0 copir.g capability (Section 3.2),
C.
Procedures and training for SB0 (Section 3.4),
0.
Proposed modifications (Section 3.3), and E.
Quality assurance and technical specifications for SB0 equipment (Section 3.5).
For the determination of the proposed minimum acceptable SB0 duration, the following factors in the licensee's submittal are reviewed:
a) offsite power design characteristics, b) emergency ac power system configuration, c) determination of the emergency diesel generator (EDG) reliability consistent-with NSAC-108 criteria (9), and d) determination of the. accepted-EDG target l
reliability. Once these factors are known, Table 3-8 of NUMARC 87-00 or Table 2 of Regulatory Guide 1.155 provides a matrix for-determining the required coping duration.
For the SB0 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 condition 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 assure:
availability of sufficient condensate inventory for decay heat a.
- removal, 3
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b.
adequacy of the class lE battery capacity to support safe
- shutdown, i
c.
availability of adequate ' compressed air for air-operated valves 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, e.
ability to provide appropriate containment integrity, and j
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 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 NUMARC 87-00.
This SB0 evaluation is based on a review of the licensee's submittals-dated April 17 and 20, 1989-(ll.and 20), and March 30,1990(12), a telephone conversation on July 3,1990, and the available information in the plant Updated Final Safety Analysis Report (UFSAR)'(13); it does.not include a 4
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concurrent site audit 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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l 3.0 EVALUATION 3.1 Proposed Station Blackout Duration Licensee's submittal The licensee, Virginia Electric and Power Company (VEPCO), calculated (11 and 12) a minimum acceptable station blackout duration of eight hours for North Anna Power Station Units 1 and 2.
The licensee stated no modifications are necessary to attain this coping duration, i
The plant factors used to estimate the proposed SB0 duration are:
1.
Offsite Power Design Characteristics-The plant AC power design characteristic group is "P2" based on:
a.
Independence of the plant off site power system characteristics of "I1/2,"
b.
Expected frecuency of grid-related LOOPS of less than one-l per 20 years, c.
Estimated frequency of LOOPS due to extremely severe weather (ESW) places the plant in ESW group "4,"
and d.
Estimated frequency of LOOPS due to severe weather (SW) places the plant in SW group "2."
2.
Emergency AC (EAC) Power Configuration Group The EAC power configuration of the plant is "C."
Each unit at-l North Anna power station is equipped with two dedicated EDGs.
One EDG per unit is necessary to operate safe' shutdown equipment following a LOOP.
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3.
Target Emergency Diesel Generator Reliability l
The licensee selected a target EDG reliability of 0.95 based on having a nuclear unit average EDG reliability of greater than 0.95 for the last 100 demands.
The licensee stated (12) that the-targeted EDG reliability will be maintained.
Review Of Licensee's submittal The factors which affect the estimation of the required SB0 coping duration are: the independence of offsite power system, the estimated frequency of LOOPS due to the severe'and extremely severe weather conditions, the expected frequency of the grid-related LOOPS, the classification of EAC, and the selection of EDG target reliability.
The licensee's estimated frequency of LOOPS due to SW and ESW conditions conform with those given in Table 3-2 of NUMARC 87-00. The licensee correctly classified the EAC configuration of each unit as "C."
l The licensee stated that the independence of.the offsite power system grouping is "11/2." A review of the North Anna power station UFSAR indicates that:
1.
All offsite power sources are connected to the plant through one switchyard.
2.
At each unit, there are two divisions of 4.16 kV emergency buses, j
each division is normally powered from a separate and independent offsite power source through.-a reserve station service transformer (RSST), see Figure 1 (20).
3.
Upon the loss of RSST "A," "B," or "C," (loss of preferred power source), the connected emergency bus (es), i.e. Bus 1H, 2H, 1J or-2J, can only be vowered through manual closure of circuit breakers which tie independent divisions together.
This means of providing l
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1501 15F1 15El TRANSFER "C"
. TRANSFER "F-TRANSFER E-l 1503 15F3 15F4 15E3
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EMERGENCY EERGENCY EMERGENCY EMERGENCY BUS - 1.1
, ' _i BUS 1i BUS 21 BUS 2H
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EDG MOD DN EDG EDG EDG IJ IH 2J 2H i
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NORTH ANrM POWER STATION L
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power does not conform to the operating guidance regarding the independence of the emergency trains in a unit.
p using the guidance provided in Table 5 of RG 1.155 the independence of the offsite power system grouping is "I3."
This conclusion is driven by the configuration discussed in item 3 above.
l The licensee's statement of nuclear unit average EDG reliability of greater than 0.95 for the last 100 demands as a justification for selecting a target EDG reliability of 0.95 is in conformance with both NUMARC 87 00 and RG I.155.
Although the licensee is committed to maintain the targeted EDG reliability, it did not state whether the plant has any formal EDG reliability program which conforms to guidance provided in RG 1.155.
Since the information supporting the EOG-target reliability is only'available onsite for review, an audit may be required to confirm compliance.
With regard to the expected frequency of grid related LOOPS at' the site, we cannot 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 the U.S., indicates that the North Anna station did not have any grid-related LOOPS prior to the calendar year 1984.
This time period does not include the last six years of operation of the North Anna power station.
However, in the-absence of any contradicting information, we agree with the licensee's statement.
Based on the above, we concur with the licensee that the offsite power design characteristics of the site is "P2" requiring a minimum coping duration of eight hours. The independence of offsite' power grouping does not affect the classification of the site's offsite power design.
characteristic grouping.
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3.2 Alternate Ac (AAC) Power Source Licensee's Submittal The licensee stated that the AAC power source at North Anna will be from~
f one of the four EDGs at the site.
This AAC power source will be available to the blacked out unit within one~ hour from the onset of an SB0 event and has sufficient capacity and capability for coping with an SB0 for four hours while maintaining and bringing both units to safe shutdown conditions.
The proposed AAC power configuration is shown in-Figure 1.
The licensee proposed a modification of the electrical connection configuration of the EDGs.
Currently, emergency buses 2J and I
2H for unit 2 are connected to each other through tie breaker 25H1, but-no such connection exists between unit 1 emergency buses lJ and lH. The proposed modification would add tie breaker 15J4.to connect emergency bus lJ to emergency bus lH.
Review of Licensee's submittal The licensee's proposed AAC power source configuration, see Figure 1, does not conforms to an acceptable configuration provided in NUMARC 87-00 Supplemental Questions / Answers under Question C.1 (15).
The licensee addressed this non conformance for the Surry power station by-q L
proposing to install a non-safety grade cross-tie between the transfer Buses "D" and "E" (16).
The licensee needs to commit to the same modification for the North Anna Units 1 and 2.
This is needed to have an acceptable cross connect to power the needed air compressor.from.the operating EDGs.
The proposed 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:
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Paragraph B.9 of Appendix B states, "the AAC power source shall be
... capable of maintaining voltage and frequency within limits 10 l
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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.
l 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 I
capable of powering the required loads at both units."
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o Paragraph B.12 of Appendix B states, "... the AAC system shell be demonstrated by initial test to be capable of_ powering reg &/sd l
shutdown equipment within one hour of a station blackout svent."
.l 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; Questions 3.4 and 8.3, and further detailed in References 17,-18, and 19.
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addition, the SB0 rule' states that at' multi-unit sites where the I
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 sour:es' provided that they meet the applicable requirements.
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 available in the NB0 unit in addition to the number of EDGs required to meet the minimum EDG redundancy requirement for powering a normal safe 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 E3Gs per unit would meet only the minimum redundancy requirement, and there is no excest EDG.
l However, there are some plants at' multi-unit sites.which have EDGs that just meet the minimum redundancy but each EDG has sufficient capacity tc power all the normal LOOP loads of the NB0 unit and also tas sufficient excess capacity to power the required safe shutdown loads of the SB0 unit.
Recognizing the existence of.this type of situation, the staff 11 3
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has interpreted the ' literal' excess EOG redundancy requirement of the SB0 rule to allow large capacity EDGs to qualify as AAC sources, provided other applicable requirements are met.
In order to take credit for this interpretation, the NRC staff's basic position has been (17, 18, and 19) that:
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no action should be taken that would exacerbate the already difficult situation in the NB0 unit. Any actions that make operator tasks more difficult such as load switching or i
disablement of information readouts or alarms in the control ' room are also considered to be a degradation of normal safe shutdown capability for LOOP in the NB0 unit. And, 2.
excess capacity of the EDG being designated as an AAC source.
should not be the capacity made available by shedding or not powering normal safe shutdown loads in the NB0 unit.
Examples of such loads are:
motor driven auxiliary feedwater pumps;- heating, ventilation and air conditioning loads; the power' supply of-the plant computer; one or more sets of redurdant instrumentation; etc.
The shedding of such loads constitutes degradation of the normal safe shutdown. capability of the NB0 unit.
It is not in the interest of safety to reduce the capability to handle various eventualities in one unit for the purpose of meeting the SB0 rule 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.
The excess capacity of the EDG in the NB0 unit that qualifies it as an AAC source is, therefore, 'only that available 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.'
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In its SB0 supplemental response (12), the licensee stated that load shedding is needed in the NB0 unit to provide power to selected equipment in the blacked out unit.
During a telephone conversation on July 3, 1990, the licensee provided a list of NB0 and SB0-loads that are t
expected to be carried by one EDG.
On the NB0 load list, the licensee did not consider the load requirements associated with the residual heat removal (RHR) pump, component cooling water pump (CCW), turbine.
generator oil pump, and generator lift pump.
The licensee identified the following SB0 loads:
two battery chargers and associated loads, two control rod drive mechanism fans, control room / emergency switchgear chiller, emergency switchgear room air conditioning unit, pressurizer
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heater, and transformer losses for a total of 519 kW.
The licensee stated that the instrument air compressors are powered from emergency buses 1H and 2H, therefore, an air compressor may not be available until-the electrical cross-tie is made.
To conform with the guidance stated above, the licersee needs to consider the load requirements associated with the RHR pump, turbine generator oil pump, CCW pump, and generator lift pump as part of the required loads on the NB0 unit.
Our review of the plant UFSAR indicates a discrepancy on equipment load requirements between what is' given in-the UFSAR and that provided by the licensee.
If we were to add the missing loads to the licensee's identified NB0 loads, then the total NB0 loads will exceed the 2,000 hour0 days <br />0 hours <br />0 weeks <br />0 months <br /> rating capacity (3,000 kW) of each EDG.
Table 8.3-6 of the UFSAR, which itemizes.the individual equipment loads, l
gives a total of 2749 to 2938 kW for operation from 1 to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after l
a LOOP.
Therefore, the site EDGs cannot be considered.as a viable AAC power source for the blacked out unit.
l Based on the above, we conclude that the licensee's proposed AAC power l
source does not conform to the requirements of the SB0 rule, and the-4 l
licensee needs to provide an alternate power source to support the required SB0 loads, i
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3.3 Station Blackout Coping Capability The plant coping capability with a station blackout for the required duration of eight hours is assessed based on the following results:
1.
Condensate Inventory for Decay Heat Removal Licensee's submittal The licensee stated that 103,024 gallons of water are required for decay heat removal for the proposed SB0 duration of eight hours.
The minimum available water in the Emergency Condensate Storage Tank (ECST) per technical specifications is 110,000 gallons per l
unit.
This volume of water exceeds the quantity required'to cope with an SBC of 8-hour duration.
The licensee stated that no plant modifications or procedure changes are needed to; utilize this water source.
Review of Licensee's Submittal I
l The licensee estimated the needed condensate inventory for decay heat removal during an 8-hour 380 duration using a generic equation given in NUMARC 87 00.
The licensee-stated that the plant will be maintained in a hot standby condition during the SB0 event.
For the purpose of this' review we used data from Branch Technical Position ASB 9 2, " Residual Decay Heat Release Rate for Light' Water Reactors," (14) to estimate the needed water to maintain hot standby condition for an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> SB0 event.
Based on a maximum-reactor thermal power of 2,905 MWt, we estimated that -103,300 gallons of condensate would be needed to remove decay heat during an 8-hour SB0 event. A review of the plant UFSAR (revision 9/89) indicates that the minimum ECST tank level is 110,000 at all times.
Therefore, we agree with the licensee that the plant has 14 l
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I sufficient condensate inventory to cope with an:SB0 event of eight hours duration. However, the licensee needs to describe the 1
operability of the decay heat removal system in the absence of sufficient AC and DC power sources during an SB0 event (see Section 3.2 above, and item 2 below).
2.
Class lE Battery Capacity Licensee's Submittal The licensee stated in the April 17, 1989 submittal (11) that the-station batteries have sufficient capacity to meet SB0 loads for one hour without charging, after which battery voltage will degrade.
Each unit at North Anna has two batteries per safety train.
The AAC power source will support the battery chargers on one safety train.
Therefore, one division (two channels) of instrumentation will be available for the entire SB0 event.
The i
batteries not connected to the AAC powered charger will be-monitored and the loads will be procedurally: stripped to maintain additional channels of instrumentation.
Review of Licensee's Submittal Since the AAC power source does not meet the guidan.ce for the SB0 rule, the assumption that one division of class 1E batteries are charged from AAC source is invalid.
To conform with the guidance provided in NUMARC 87-00 Supplemental Questions / Answers the licensee needs to ensure that the normal battery-backed plant monitoring and electrical system controls remain operational for.
successfully coping with and recovering from an SB0 event.
Therefore, the licensee needs to' provide a separate AAC power.
source, or provide additional battery capacity to support the required SB0 loads for eight hours without charge.
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3.
Compressed Air l
Licensee's Submittal In the April 17, 1989-(11) SB0 submittal, the licensee stated that all air operated valves (A0Vs) needed for one hour SB0 ccping can either be operated manually or have sufficient back-up sources independent of the preferred and blacked out unit's class lE power.
supply.
Valves requiring manual operation or that need back-up power sources for operation are identified in plant procedures.
Both North Anna units operate on a common compressed air system, with one instrument air compressor per unit powered from an emergency bus.
There are also separate air bottles or a nitrogen supply on critical valves to allow control without a compressor.-
An air compressor will be available within one hour after the electrical cross-connect is established.
Review of Licensee's Submittal Since the air system is common between the units and the compressors are supported from emergency buses, the coinpressed air will be available within one hour when the electrical cross-connect is established. This assessment is' based on the i
assumption that the licensee will commit to add a non-safety grade cross tie Latween transfer buses "D" and "E."
A review of the plant UFSAR indicates that the auxiliary feedwater (AFW) system is equipped with redundant flow control' valves.
These valves are either air-operated or motor-operated valves.
The atmospheric dump valves which are used to control decay heat release rate are l
also air operated.
The UFSAR also states that"these air operated valves are equipped with back-up compressed air, and local manual l
back-up. Therefore, we agree with the licensee that air operated-valves needed to cope with an SB0 have sufficient back-up source i
for their operations.
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4.
Effects of Loss of Ventilation l
Licensee's submittal i
The licensee's canulated post.SB0 steady state ambient air temperature for the plant areas containing $80 equipment is as follows:
1 Area Temperature ('F) f.inal Initial Emergency Switchgear Room 153'F (<l20'F)*
NP 4
Charging Pump Cubicle 300'F (<l20'F)*
NP i
i Control Room 181'F (<120'F)*
NP AFW Pump Room 175'F NP
- = Temperature when HVAC is available 91 hour0.00105 days <br />0.0253 hours <br />1.50463e-4 weeks <br />3.46255e-5 months <br /> NP = Not provided by the licensee i
No heating, ventilation, and air conditio41ng (HVAC) systeia would be availabic to the emergency switchgear room, control room, chargirs pump cubicle and AFW pump room for the first hour following an SB0 event.
The op m bility of the $80 response equipment in the dominant areas of concern has been assessed in accordance with Appendix F and the Topical Report to the NUMARC 87 00.
The licensee has asserted that opening doors and dampers and initiating appropriate HVAC within one hour after the 580 will reduce the emergency switchgear room (ESR), charging pump cubicle AFW pump room and control room temperatures to less than 120'F.
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Review of Licensee's submittal The licensee's submittal dated March 30, 1990 (12) implied that the NUMARC 87-00 method was used for calculating the steady state l
room ambient air temperature rise in dominant areas of concern.
F The NUMARC 87 00 method is not applicable to an eight hour room i
heat up snd therefore, a different method needs to be used.
In addition, since the AAC power source does not conform to the requirements of the SB0 rule, the assumption of HVAC availability l
within one hour is invalid.
Therefore, the licensee needs to re-assess the room heat up calculations by considering an appropriate method for an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> SBO.
The licensee's implicit assumption that HVAC operation after one hour will insure a temperature less than 120'F in the control room. ESR, and charging pump cubicle is incorrect. Detailed transient room heat up calculations have shown that most of a room's temperature rise after the loss of HVAC occurs in the first hour.
Thus, it is likely that, at one hour, the area temperatures to be almost the same as the final calculated temperatures before the AAC powered HVAC is assumed to be initiated.
Therefore, it is expected that calculated final temperatures in tM above areas to be well in excess of 120'F.
The licensee needs to re-assess the operability of the 580 equipment in the above areas using the l
final ambient temperatures resulting from the loss of HVAC during i
an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> SB0 event.
In addition, the licensee needs to provide additional specific details on anticipated operator actions in the AFW pump room to justify the acceptability of a 175'F environment.
These details need to specifically address the ability of the operator to adequately perform his functions in this room during an SB0 event.
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Containment Isolation i
l Licensee's submittal i
The licensee reviewed the plant list of containment isolation valves to verify that valves which must be capable of being closed or operated (cycled) during an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> SB0 duration can be i
positioned (with indication) independent of the preferred and j
blacked out unit's class IE power supplies.
The licensee stated that no procedure changes or plant modifications are required to ensure that appropriate containment integrity can be maintained l
under SB0 conditions.
l Review of Licensee's submittal i
A review of the containment isolation valves (CIVs) was performed using the CIVs identified on Table 6.2 39 of the North Anna UFSAR.
This review was performed in accordance with the criteria 1
delineated in NUMARC 87 00 and RG 1.155. We concur with the licensee's statement that all CIVs which must be capable of being closed or operated (cycled) during the SB0 coping duration can be positioned (with indication) independent of the preferred and blacked out unit's class lE power supplies.
6.
Reactor Coolant Inventory Licensee's submittal The licensee stated that a plant specific analysis performed for the Surry Power Station resulted in demonstrating that core uncovering would not occur during the one hour period following an SB0 event.
This analysis bounds the North Ana reactor coolant system (RCS) inventory requirement.
Therefore, make-up systems are not required to maintain core cooling under natural circulation for the initial one hour period.
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During the telephone conversation on July 3, 1990, the licensee stated that a charging pump in the NB0 unit can provide sufficient make up flow to the RCS of both units through a cross connect line.
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Review of Licensee's Submittal l
We performed an independent evaluation to assess the reactor coolant inventory depletion.
This evaluation consid: red the volume of water above the core available for lentage prior to core uncovering and the charging pump capacity at normal expected RCS pres *ure as compared to the leakage rate from both units.
The blacked out unit requires a charging flow rate of 100 gpn, 25 gpm per pump for seal leak and an assumed 25 gpm for the maximum allowed technical specification leak rate, for maintaining the RCS inventory.
The NB0 unit requires a charging flow to replenish the losses from the nominal seal leakage fror, pumps and the level shrink caused by cooldown.
At each unit there are three charging pumps, each with a design flow rate capacity of 150 gpm.
Therefore, one charging pump has sufficient capacity to maintain the RCS inventory at the NB0 unit and prevent core uncovering at the blacked out unit provided that the reactor at the NB0 unit is kept at hot standby condition during an SB0 event.
However, the licensee needs to justify the adequacy of this method for maintaining the RCS water level above the core without the benefit of instrumentation or DC power in the blacked out unit after one hour when the batteries are depleted.
3.4 Proposed Procedures and Training i
Licensee's submittal The licensee has stated that the following procedures have been i
reviewed against the guidance of NUMARC 87 00, Section 4, and have been or will be modified where necessary:
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t i-1.
AC power restoration including the Virginia Power Transmission j
System Restoration Plan and Station Procedure AP 10.2, l
]
" Restoration of Switchyard."
2.
Severe weather procedure including Station Procedure AP 41,
" Severe Weather Conditions."
3.
Station blackout response including implementation of the AAC source to achieve safe shutdown on both units.
t 4.
Station ECA 0 Series (Emergency Contingency Action) procedures based on Westinghouse generic procedures changed in accordance with NUMARC 87 00 for 580 " defense-in depth."
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5.
Power restoration to a de energized emergency bus procedures (AP-10 Series).
6.
Procedures for using the proposed new manual cross tie between emergency busses lJ and lH, and operator flexibility in electrical load selection consistent with plant conditions and the 2000 hour0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> rating of the EDG.
The licensee has stated that all of the aforementioned procedure changes will be implemented within two years after a notification is received fromtheNRCinaccordancewith10CFR50.63(c)(3).
Review of Licensee's Submittal We neither received nor reviewed the affected procedures.
These procedures are plant specific actions concerning the required activities to cope with an SBO.
We believe it is the licensee's responsibility to revise and implement these procedures, as needed, to mitigate an SB0 event and to assure that these procedures are complete and correct and that the associated training needs are carried out accordingly.
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3.5 Proposed Nodifications Licensee's submittal The licensee proposes (11) to add an emergency bus tie breaker between Bus lH and IJ in Unit 1.
This modification will allow transfer of power from emergency Bus lJ to Unit 2.
The licensee stated that the modifications of procedures are to be implemented within two years after the notification provided by the staff in accordance with 10 CFR 50.63 (c)(3).
Review of Licensee's Submittal The proposed modification does not conform to the guidance provided in NUMARC 87 00 Supplemental Questions / Answers. The licensee acknowledged (12) that this modification is unacceptable to the staff and proposed a new modification for the Surry power station.
The new modification (16) cross ties transfer Buses "D" and "E."
The licensee needs to perform a similar modification for the North Anna plant.
In. addition, since the proposed AAC power source does not have sufficient capacity, additional modifications are needed in order for the North Anna power station to t
become an AAC plant.
3.6 Quality Assurance And Technical Specifications The licensee's submittals do not document the conformance of the plant's 580 equipment to the guidance of RG 1.155, Appendices A and B.
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1
4.0 CONCLU$10N$
Based on our review of the licensee's submittals and the related supporting documents and discussions for the Nortn Anna Power Station Units 1 and 2, we find that the submittal does not conform to the requirements of the SB0 rule and the guidance of RG 1.155 for the following reasons:
1.
Independence of Offsite Power System The licensee classifies the site as "11/2."
Our review indicates that the site is "13" since upon loss of power from either RSST "A," "B," or "C" (preferred power sources) only one division of emergency buses can be powered.
The RG 1.155 position is that all emergency buses be powered.
2.
Alternate AC Power Source i
The licensee's proposed load shedding of the non blacked out (NBO) unit is not in conformance with the requirements of the 580 rule and the guidelines provided in RG 1.155, NUMARC 87 00 Supplemental Questions / Answers. The load shedding scheme will result in the degradation of the LOOP safe shutdown capability of the N80 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 tource does not have sufficient capacity to power the selected skie shutdown equipment in the blacked out unit.
3.
Condensate Inventory for Decay Heat Removal Although sufficient condensate inventory exists for each unit in the emergency condensate storage tank, the ability of the auxiliary feedwater system to provide that water to the steam generators is in doubt due to the lack of DC power for control and i
1
o instrumentation, resulting from insufficient AAC capacity (see items 2 and 4).
i 4.
Class 1E Battery Capacity The plant UFSAR indicates that each class IE battery will last for one hour without being charged.
However, the batteries are needed to supply the connected loads for eight hours.
Since the proposed AAC power source does not conform to the requirements of the SB0 rule, the assumption that one division of the class lE batteries
)
will be charged from the AAC source is invalid.
Therefore the licensee needs to provide a separate AAC power source, or provide additional battery capacity to ensure that the class IE batteries will last for eight hours without charge.
To conform with the guidance provided in NUMARC 87-00 Supplemental Questions / Answers, I
the licensee needs to ensure that the normal battery backed plant monitoring and electrical system controls remain operational for successfully coping with and recovering from an S80 event.
5.
Effects of Loss of Ventilation The licensee's submittal indicates that the NUMARC 87-00 method was used to calculate the ambient air temperature rise-in the dominant areas of concern.
This method is only applicable to a four coping plant.
The licensee also takes credit from the i
availability of the AAC powered HVAC to selected areas in the blacked out unit.
Since the AAC power source does not conform to the requirements of the SB0 rule, the assumption of the availability of the required HVAC is invalid.
Therefore, the licensee needs to re assess the room heat-up calculations and SB0 equipment operability using an appropriate method for an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> SB0 event without HVAC, or provide an alternate AAC source.
In addition, the acceptability of an AFW pump room at 175'F for operator entry and manual actions needs to be further justified by the licensee. Further, the licensee needs to justify why there is i
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1 no mention of opening the control cabinet doors within 30 minutes from the onset of an SB0 cs guided in NU' ARC 87 00 Supplemental Questions / Answers.
6.
Reactor Coolant Inventory The licensee proposes to use a charging pump from the NB0 unit to provide the needed RCS make-up in the blacked out unit. Our
)
review indicates that the NB0 charging pump has sufficient capacity to maintain an adequate RCS inventory in the SB0 unit.
However, the licensee needs to justify the adequacy of this method for maintaining the RCS inventory above the core without the benefit of instrumentation or DC power in the blacked out unit.
7.
Proposed Modifications The selection of one of the EDGs as an AAC power source does not conform with the requirements of the SB0 rule, in addition, the licensee's proposed modification of the emergency bus tie breaker does not conform to the guidance provided in NUMARC 87 00 Supplemental Questions / Answer. Therefore, additional modifications are necessary for the North Anna power station to become an AAC plant.
8.
Quality Assurance and Technical Specifications The licensee has not submitted any information regarding the quality assurance or technical specifications aspects of $80 coping equipment. This does not meet the requirements of RG 1.155 Section 3.5 and Appendices A and B.
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o 5.0 References l
1.
The Office of Federal Register, " Code of Federal Regulations Title 10 Part 50.63," 10 CFR 50.63, January 1, 1989, i
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 Comission, " Collection and Evaluation of Complete and Partial losses of Offsite Power at Nuclear Power Plants,"
NUREG/CR 3992, February 1985.
4.
U.S. Nuclear Regulatory Comission, " Reliability of Emergency AC Power System at Nuclear Power Plants," NUREG/CR-2989, July 1983.
5.
U.S. Nuclear Regulatory Comission, " Emergency Diesel Generator Operating Experience, 1981 1983," NUREG/CR 4347, December 1985.
6.
U.S. Nuclear Regulatory Comission, " Station Blackout Accident Analyses (Part of NRC Task Action Plan A 44)," NUREG/CR-3226, May 1983.
7.
U.S. Nuclear Regulatory Comission 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 Documents on Station Blackout (TAC 40577)", October 7, 1988.
10.
Nuclear Safety Analysis Center, "The Reliability of Emergency Diesel Generators at U.S. Nuclear Power Plants," NSAC-108, Wyckoff, H.,
September 1986.
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i 11.
Cartwright, W. R., letter to USNRC Document Control Desk, " Virginia Electric and Power Company, Surry Power Station Units 1 and 2 North l
Anna Power Station Units 1 and 2, Response to 10 CFR 50.63: Loss of all Alternating Current Power," Docket Nos. 50 280 and 50 281, NRC License Nos. DPR 32 and DPR 37, letter Serial No.88-414, dated April 17, 1989.
12.
Stewart, W. L., letter to USNRC Document Control Desk, " Virginia Electric and Power Company, Surry Power Station Units 1 and 2, North Anna Power Station Units 1 and 2, Supplemental Response to 10 CFR 50.63:
Loss of all Alternating Current Power," Docket Nos. 50 280 and 50 281, NRC License Nos. DPR 32 and DPR 37, letter Serial No. 88 4148, dated l
March 30, 1990.
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13.
North Anna Power Station Units 1 and 2 Updated Final Safety Analysis l
Report.
i 14.
U.S. Nuclear Regulatory Commission," Standard Technical Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants LWR Edition," NUREG 0800, June 1987.
15.
Thadani, A. C., letter with attachment to A. Marion of NUMARC, " Publicly Noticed Meeting, December 27, 1989," dated January 3, 1990 (confirming "NUMARC 87 00 Supplemental Questions / Answers," December 27,1987).
16.
Stewart W. L., letter to USNRC Document Control Desk, " Virginia Electric and Power Company Surry Power Station Units 1 and 2 Station Blackout Supplemental Response," Docket Nos. 50-280 and 50 261, NRC License Nos.
DPR 32 and DPR-37, letter Serial No.90-410, dated August 1,1990.
f 17.
Rosa, F., Memorandum to Docket Concerning Beaver Valley Units 1 and 2,.
j
" Meeting Sumary - Meeting of February 22, 1990, on Station Blackout Issues (TAC 68510/68511)," Docket Nos. 50-334 and'50 412, dated March 6,
[
l
- 1990, i
27 i
i J
18.
Tam, P. S.,i4emorandum for, " Daily Highlight Forthcoming Meeting with NUMARC on Station Blackout (SBO) Issues (TAC 40577)," (providing a Draft Staff Position Regarding Use of Emergency AC Power Sources (EDGs) as Alternate AC (AAC) Power Sources, dated April 24,1990), dated April 25, 1990.
19.
Russell, W. T.,
letter to W. Rasin of NUMARC, " STATION BLACKOUT," dated June 6, 1990, i
4 20.
Cartwright W. R., letter to USNRC Document Control Desk, " Virginia Electric and Power Company, Surry Power Station Units 1 and 2 North Anna Power Station Units 1 and 2, Supplemental Information to 10 CFR 50.63 Response: Loss of all Alternating Current Power," Docket Nos.
50 280, 50 281, 50 338, and 50 339, License Nos. OPR 32, DPR 37, NPF-4 and NPF 7, letter Serial No. 88 414A, dated April 20, 1989, a
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