ML18153C403
| ML18153C403 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 10/15/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18152A162 | List: |
| References | |
| NUDOCS 9010250052 | |
| Download: ML18153C403 (11) | |
Text
-
UNITED STATES e
NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REGARDING STATION BLACKOUT SURRY POWER STATION, UNITS 1 AND 2
1.0 INTRODUCTION
On July 21, 1988, the Code of Federal Regulations, 10 CFR Part 50, was amended to include a new Section 50.63, entitled "Loss of All Alternating Current Power, 11 (Station Blackout). The station blackout (SBO) rule requires that each light-water-cooled nuclear power plant be able to withstand and recover from an SBO of specified duration, requires licensees to submit information as defined in 10 CFR 50.63, and requires licensees to provide a plan and schedule for,
conformance to the SBO rule. The SBO.rule further requires that the baseline assumptions, analysis and related information be available for NRC review.
Guidance for conformance to the rule is provided by (1) Regulatory Guide (RG) 1.155, Station Blackout, (2) NUMARC 87-00, Guidelines and Technical Bases for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors, and (3) NUMARC 87-00 Supplemental Questions/Answers an<4Major Assumptions dated December 27, 1989 (issued to the industry by NUMARC January 4, 1990).
To facilitate the NRC staff's (hereafter referred to as staff) review of licensee responses to the SBO rule, the staff endorsed two generic response formats.
One response format is for use by plants proposing to use an alternate AC (AAC) power source and the other format is for use by plants proposing an AC independent response.
The generic response formats provide the staff with a suD111ary of the results from the licensee's analysis of the plant's SBO coping capability.
The licensees are expected to verify the accuracy of the results and maintain documentation that supports the stated results. Compliance to the SBO rule is verified by a review of the licensee's submittal, an audit review of the supporting documentation as deemed necessary, and possible follow-up NRC inspections to
- " ensure that the licensee has implemented the appropriate hardware and/or pro-
,,.,~edure modifications that will be required to comply with the SBO rule.
The licensee proposes to use existing emergency diesel generators (EDGs) as an AAC source and has submitted its response in the applicable generic response format.
The licensee's original response was provided by letters from W.R. Cartwright (Virginia Electric and Power Company) to Document Control Desk of the U.S. Nuclear Regulatory Connission (NRC), dated April 17 and April 20, 1989.
In addition, the licensee provided a response to the NUMARC 87-00 Supplemental Questions/Answers by a letter from W. L. Stewart to Document Control Desk, Nuclear Regulatory CoD111ission, dated March 30, 1990. Further information was supplied by a letter from W. L. Stewart to Document Control Desk, Nuclear Regulatory CoD111ission, dated August 1, 1990.
The licensee's responses were reviewed by Science Applications International Corporation (SAIC) under contract to the NRC.
The results of the review are documented by an SAIC Technical Evaluation Report (TER), SAIC-90/1371, "Surry Power Station, Units 1 and 2, Station Blackout Evaluation," dated September 24, 1990 {Attachment No. 1).
- Nuclear Management and Resources Council, Inc.
9010250052 901015 PDR ADOCK 05000280 p
e e 2.0 EVALUATION After reviewing the licensee's SBO submittals and the SAIC TER, the staff concurs with the conclusions as identified in the SAIC TER (refer to Attachment No. 1 for details of the review).
Based on this review, the staff findings and recommenda-tions are summarized as follows.
2.1 Station Blackout Duration The licensee has calculated a minimum acceptable SBO duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> based on an offsite power design characteristic group of "P2*", an emergency AC configuration group "C", and an EOG reliability target of 0.95.
The "P2*" grouping is based on an independence of offsite power classification of Group "I 1/2", a severe weather (SW} classification of Group "1" and an ex-tremely severe weather (ESW) classification of Group "4". The licensee, in their August 1, 1990 submittal, states that the Surry switchyard has a 500 kV section and a 230kV section which are not electrically connected.
The staff disagrees with this characterization and notes upon review of the FSAR that the switch-yards are electrically connected at two points through two 500/230/34.5 kV trans-formers, with the 34.5 kV windings serving as power supply sources to the 4.16 kV safety buses through 34.5/4.16 kV transformers.
One 34.5 kV winding supplies power to one division of each unit, whereas the other 34.5 kV winding supplies power to the other division of each unit.
Upon failure of one of the two 34.5 kV sources, the safety bus of one division of each unit would remain energized with-out requiring an automatic or manual transfer, while the other division would be supplied via an automatic transfer of power from a separate 230 kV/34.5 kV trans-former.
However, as discussed in the attached TER, upon loss of reserve station service transformer RSST-C, the only method of energizing the second division would be by manually tieing the two emergency buses together. This method of connecting the two emergency buses together is unacceptable in determining the independence of offsite power classification. Therefore, the independence of offsite power is Group 0 !3". This results in a required coping duration of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, rather than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
2.2 Alternate AC (AAC) Power Source The licensee has proposed to use the EDGs as an AAC power source to operate systems necessary for the required SBO coping duration and recovery therefrom.
2.2.1 General staff position on AAC power sources The definition* in 10 CFR §50.21 RG 1.155 and NUMARC 87-00 define AAC power source in terms of four attributes: ll) connections to the offsite or the onsite AC power systems, (2) minimum potential for conunon cause failure with offsite power or the onsite emergency AC power sources, (3) timely availability, and (4) re-quired capacity and reliability. More specifically, in regard to the fourth attribute, the SBO rule reads as follows:
"(4)
Has sufficient capacity 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 shutdown (non-design basis accident)."
e In view of the variety of types, capacities and capabilities of power sources proposed as AAC sources by various licensees, the staff has characterized pro-posed AAC power sources as being either optimum, fully capable or partially capable. This characterization, which relates only to the capacity attribute cited above, was necessary in order to facilitate the staff review of licensee responses to the SBO rule. It does not invalidate or revoke any of the require-ments 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 and equipment.
Such a design, following actuation of the AAC source, would provide completely redun-dant normal safe shutdown capability during an SBO and recovery therefrom from the main control room.
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.
Th.is includes decay heat remova 1, battery charging, HVAC {heating, ventilation and air conditioning), emergency lighting, and the associated controls and instrumentation. Thus, although redundant capability is not available, a fu_lly capable AAC source would enable attainment of safe shutdown during an SBO and recQvery therefrom from the main control room.
A minimally capable AAC power source design is one that is not capable of power-ing all (or any) normal safety train related safe shutdown equipment; but it is capable of powering specific equipment that, in conjunction with extensive manual operator actions both inside and outside of the control room, is critical for attaining safe shutdown during an SBO.
Appendix R diesels proposed as an AAC source are examples of minimally capable AAC sources. With this design, operability of the main control room could not be assured unless the batteries were sized to operate for the SBO 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 EDGs as AAC power sources is documented in the SBO rule 10 CFR §50.63, 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 SBO rule states:
11At multi-unit sites, where the combination of emergency ac power sources exceeds the minimum redundancy requirements for safe shutdown (non-DBA) of all units, the remaining emergency ac power sources may be used as alternate ac power sources provided they meet the applicable requirements."
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 (NBO) unit that is in addition to the number of EDGs required to meet the min-imum EDG redundancy requirement for powering a normal safe shutdown for a loss of offsite power (LOOP) event. Thus, the EDG 1s in a two-unit site with two dedi-cated EDG 1s 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.
e e However, there are some plants at two-unit sites which just meet minimum redun-dancy, but where each EDG is of sufficient capacity to fully power all the normal LOOP loads of the NBO unit, and also has sufficient excess capacity for powering the required safe shutdown loads of the SBO unit.
In recognition of the existence of this type of situation, the staff has interpreted the excess EDG redundancy requirement of the SBO rule to allow EDGs just meeting the minimum EDG redundancy requirements to qualify as AAC sources on the basis of excess capacity, provided the other applicable requirements for AAC sources are also met.
The NRC 1 s basic position on the use of EDGs as AAC power sources on the basis of excess capacity is that such excess capacity should not be attained by load shedding in the NBO unit which results in a degradation of its normally avail-able safe shutdown capability for the LOOP condition.
Any actions that would add to the burden of operators that are already in a high stress environment, such us 1oad switching or disablement of information readouts or alarms in the con-trol room, are considered to be a degradation of normal safe shutdown capability for LOOP in the NBO unit. The staff position is, therefore, that the normal equip-ment compliment should remain available with adequate EDG capacity for use should it become necessary. The NBO unit should have the capability for hot shutdown/
hot standby forced cooling, cooldown and depressurization as required. While additional events are not explicitly being postulated, it is not prudent to dim-inish the capability of the NBO unit to mitigate problems should they arise.
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 SBO rule in another unit. Each unit must meet the SBO rule on its own merits without reducing another unit's capability to respond to its own potential problems. Therefore, a multi-unit site with the dedicated EDGs just meeting the minimum redundancy requirement but not having the excess capacity defined above for qualifying as an AAC source does not meet the SBO 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 SBO for the.. required duration.
2.2.1.2 Connectability of AAC power sources The basic criteria governing the connectability of an AAC power source are con-tained in 10.CFR 50.2 {the AAC source should be connectable to but normally not connected to the offsite or onsite emergency AC power systems), 10 CFR 50.63
{SBO should not assume a concurrent single failure or design basis accident),
and in Appendix A of 10 CFR Part 50 (the single failure criterion and the independence requirements apply to the NBO unit). Therefore, in a one-unit site, as a minimum, an AAC source need only be connectable to one set of safe shutdown equipment, regardless of whether that equipment is part of a safety train or not, or whether the AAC source is an excess redundancy EOG 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 (EOG) bus in both units. This fol-lows from the application of the above criteria and the assumptions that must be taken that an SBO can occur in either unit, and that the single failure in the NBO unit can be on either one of its EDGs or on its respective safety bus.
2.2.2 Proposed AAC power source The Surry Power Station presently has three EDGs, with one of the EDGs shared between two units.
The licensee proposes to add another EOG and dedicate two EDGs to each unit. Additional switchgear and electrical connections between the 4160V buses of Units 1 and 2 would also be added so that either one of the two EDGs of the NBO unit could serve as an AAC power source for the SBO unit.
The licensee's submittal states that the proposed AAC source is available with-in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> of the onset of the SBO event, and has sufficient capability to pro-vide power for the safe shutdown of both units for a 4-hour SBO duration.
However, a July 2, 1990 telefax to the NRC from the licensee, showing a prelim-inary tabulation of loads on the AAC source (NBO and SBO unit loads), did not include several of the normal LOOP loads on the NBO unit. Subsequently, during a telecon on July 3, 1990, the licensee discussed with the staff their proposed load management scheme for the NBO unit. The purpose of this load management scheme was to eliminate loads from the EDGs such that they would qualify as AAC sources on the basis of excess capacity. The staff told the licensee that their load management scheme on the NBO unit did not conform to the SBO rule.
By letter dated August 1, 1990, the licensee submitted a revised tabulation of the AAC source loadings (NBO and SBO unit loads) for the Surry Power Station. The re-vised tabulation excluded normal LOOP loads such as the RHR pumps and the turbine generator auxiliaries on the NBD unit. Based on the July 2, 1990 preliminary tabulation of the AAC loads and the revised August 1, 1990 tabulation, the staff concludes that the Surry Power Station EDGs do not have the excess capacity available to qualify them as an AAC source for the SBO unit.
After reviewing the SAIC TER and the licensee's proposed actions for crediting existing NBO unit EDG(s) as an AAC source, the staff has determined that the proposed AAC source does not meet the requirements of 10 CFR §50.63.
Reconunendation:
The licensee should undertake further measures, such as provid-ing an independent AAC power source, or a coping analysis which shows that the plant can cope with and recover from an SBO, for the required duration independ-ent of AC power.
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 maintain safe shutdown and recovery from an SBO for an 8-hour coping duration.
2.3.1 Condensate inventory for decay heat removal The licensee states that it has been determined, using NUMARC 87-00 methodology, that 56,495 gallons of condensate water are required for decay heat removal for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
The licensee also states that the minimum emergency condensate storage
e e
'- tank (CST) level allowed by the Technical Specifications (TS) is 110,000 gallons. The attached TER notes that approximately 96,000 gallons are needed for decay heat removal for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, which is less than the 110,000 gallons.
However, the TER notes that a review of the UFSAR indicates that only 96 000 gallons are required by the TS.
Therefore, the licensee needs to calculite the inventory required for an 8-hour coping duration, and confirm whether the cal-culated value is enveloped by the TS requirement. Also, the licensee needs to assess how the decay heat removal function will be accomplished without the benefit of instrumentation or DC power in the blacked-out unit after the battery is discharged in 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> (see Section 2.3.2).
Recommendation:
The licensee should evaluate the condensate inventory needed for decay heat removal for an 8-hour coping duration and recovery therefrom, and verify that this inventory is available in the CST and that it is enveloped by the TS.
The licensee should include these analyses and verification in the documentation supporting the SBO submittal that is maintained by the licensee.
2.3.2 Class lE battery capacity The licensee stated the design basis for the station batteries is a 2-hour duty cycle and that a battery calculation has been performed pursuant to NUMARC 87-00 methodology to verify that the Class lE batteries have sufficient capacity to meet the SBO loads for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. Further, the AAC source would be available to power the battery chargers (one DC train of each unit) after 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> following the onset of the SBO.
The licensee did not specifically state that both battery banks of the NBO unit would be powered by battery chargers during the SBO event.
The staff's review shows that the licensee's proposed AAC power source does not have the required excess capacity to qualify as an AAC source in accordance with the requirement of 10 CFR §50.63, and therefore cannot be credited toward charging the batteries. It appears that the batteries will be discharged in 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> without charging and there is no assurance that the decay heat removal function can be maintained without the control room instrumentation.and DC power required for systems and control in the blackout unit for the required SBO duration.
Reco11111endation:
The licensee should provide a battery of sufficient capacity to power all normal battery-backed monitoring and electrical systems and con-trols for the required SBO duration and recovery therefrom, or provide battery charging from an acceptable AAC power source.
2.3.3 Compressed air The licensee has stated that all air-operated vilves needed for 1-hour SBO cop-ing can be either operated manually or have sufficient backup sources of power.
Also, the licensee stated that an air compressor will be available within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> after the electrical cross-connect is established to supply power to the SBO unit from the NBO unit. Surry Power Station has a co11111on compressed air system for Units 1 and 2, and one instrument air compressor per unit is powered from an emergency bus. Also, the licensee has proposed to make modifi-cations to provide bottled air supply to atmospheric dump valves in lieu of normal air supply from the plant air compressors during the first hour of the SBO to support the 1-hour coping capability.
e e After reviewing the information provided by the licensee and the SAIC TER, the staff agrees with SAIC assessment that once the proposed modification is com-pleted, adequate compressed air will be available to power the valves needed for decay heat removal.
However, the Surry Power Station does not have a qualified AAC power source (see Section 2.2.2) and therefore, while the proposed modifica-tion does resolve the compressed air issue, it does not resolve the SBO issue.
2.3.4 Effects of loss of ventilation The licensee identified several areas that require forced ventilation.
These include the control room (common for Units 1 and 2), the emergency switchgear rooms (one for each unit), and the charging pump cubicles (common for Units 1 and 2). The licensee calculated 4-hour steady-state temperatures as follows (without forced ventilation):
- Control room
- Emergency switchgear room
- Charging pump cubicles
- Auxiliary feedwater pump room 187°F 179°F 366°F 187°F The licensee stated that ventilation to the control room and emergency switch-gear rooms would be provided within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.
However, modifications to the HVAC systems in these areas would be required to ensure that a chiller and appropriate air handling units are available with any EOG operating.
No informa-tion was provided as to what steps would be taken to ensure that the control room and switchgear rooms do not exceed 120°F during the first hour of the SBO.
Nor did the licensee state that their procedures would include a provision to open the cabinet doors in the control room within 30 minutes.
The licensee also stated that although ventilation to the charging pump rooms could be lost for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, depending on the EOG available, that based on NUMARC 87-00, Appendix F, and the short time of operation without ventila-tion, reasonable assurance of operability exists for the equipment in the charging pump cubicles. However, the licensee needs to verify that the required SBO equipment will remain operable during the SBO duration.
The licensee calculated the steady-state temperature to rise to 187°F in the auxiliary feedwater (AFW) pump rooms (one for each unit), if no remedial measures were taken or no forced ventilation provided in first 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
The licensee proposes to maintain temperatures to less than 120°F in these areas by opening doors and dampers. Also, after instrument air becomes available, forced cooling can be provided for these areas. The licensee has not specifically determined the steady-state temperature that will result from opening doors and dampers.
Consequently, the operator(s) ability to function in that environment is not known.
For containment heat-up, the licensee noted that cooling in the NBO unit would be available once instrument air and component cooling water was restored (potentially 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />), and based on a Westinghouse analysis, the total tempera-ture rise would be about 15°F for an SBO.
Then, based on NUMARC 87-00, Appendix F and previous equipment qualification, the licensee concluded that the equipment degradation within containment during the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> would be minimal.
The licensee's analyses is based on a 4-hour coping duration using NUMARC 87-00 methodology for the heat-up calculations. However, the staff has determined that an 8-hour coping duration is required, and NUMARC methodology is not appro-priate for an 8-hour coping duration. Also, the licensee's proposal to provide HVAC for limiting the heat-up in some of the dominant areas depends on the avail-ability of the excess capacity of an EOG that will be used as an AAC source.
However, the staff has determined that the EDGs of the NBO unit do not have excess capacity to be used as the proposed AAC source.
Recommendation:
The licensee should provide an acceptable AAC source, or provide other means to provide the necessary HVAC during an SBO.
If an acceptable proposed AAC is not available until 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, the licensee should evaluate the control room, charging pump cubicles, auxiliary feedwater pump room, and switchgear room, and confirm that there is reasonable assurance of equipment operability and oper-ator habitability during the first hour of the SBO.
The licensee should provide more specific details on the required operator actions and their ability to with-stand the high temperatures while opening doors and dampers to limit the heat-up in the AFW pump rooms.
The.
licensee should include in their SBO procedures a provision to open the control room cabinet doors within 30 minutes after the on-set of an SBO.
Also, these calculations and analyses should be included as part of the SBO submittal maintained by the licensee.
2.3.5 Containment isolation The licensee reviewed the plant list of containment isolation valves (CIVs) to verify that valves which must be capable of being closed or operated (cycled) during an SBO can be positioned (with indication) independent of the blacked-out unit's power supplies. The licensee stated that no plant modifications are necessary to insure containment integrity during an SBO.
The staff agr*ees and concludes that there is reasonable assurance that proper containment isolation can be obtained during an SBO.
2.3.6 Reactor coolant inventory The licensee used a plant-specific analysis to assess that reactor coolant inven-tory was adequate to prevent core uncovery during the first hour of an SBO.
Within that time, a charging pump in the NBO unit would be started to provide make-up flow to the RCS of both units through a cross-connect line, and would provide sufficient flow to ensure core cooling for the SBO period.
The staff agrees that the one charging pump should have sufficient capacity to prevent core uncovering of the blacked-out unit and to maintain RCS inventory at the NBO unit provided that the NBO unit is kept at hot standby during the SBO event.
However, the licensee needs to add an acceptable AAC source to power the charging pump and maintain a charge on the battery or describe how the inventory above the core will be monitored and maintained without the benefit of instrumentation or DC power in the blacked-out unit after 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> when the.battery becomes discharged.
Recommendation:
The licensee should provide an acceptable independent AAC source of sufficient capacity and capability to provide power to the supporting systems needed to monitor and maintain adequate RCS inventory.
l
' 2.4 Procedures and Training The licensee has stated that the procedures required for SBO coping have been identified and will be completed within 2 years after the notification by the NRC of its acceptance of the proposed modifications and method of coping with an SBO.
The licensee did not specifically address the training requirement.
The proposed procedure modifications were not reviewed by the NRC staff, but the staff expects the licensee to maintain and implement these procedures, including any others that may be required as part of the revised response, to ensure an appropriate response to an SBO event. Although personnel training requirements for an SBO response were not specifically addressed by the licensee's submittal, the staff expects the licensee to implement the appropriate training to ensure an effective response to an SBO.
2.5 Proposed Modifications In addition to a fourth EDG that is proposed to be installed and the associated switchgear changes to permit two EDGs to be dedicated to each unit, the licensee proposes to add a non-class lE crosstie connection between the 4160V transfer Bus "D" of Unit 1 and the 4160V Bus "E" of Unit 2. This crosstie will permit an EDG associated with one of the safety divisions of one unit to be connected (during an SBO) to the corresponding safety division of the other unit, such that the EDG associated with the NBO unit can serve as the AAC power source for the blacked-out unit, regardless of which of the two units is blacked-out. The present bus connections permit the second safety division of one unit to be connected to the corresponding safety division of the other unit. Together, the two proposed crosstie arrangements permit either unit to be blacked-out and either of the EDGs of the NBO unit to serve as the AAC power source for the blacked-out unit, thus meeting the single failure criteria for the NBO unit.
However, since the EDGs do not meet the excess capacity requirements of the SBO rule, the staff concludes that none of the EDGs qualify as an AAC power source.
The licensee also noted that air bottles will be added to the power-operated relief valves and modifications will be made to the control room and emergency switchgear room HVAC systems to assure adequate cooling.
No modifications to other plant equipment are described.
However, in view of the staff positions as documented in this SE, other modifications may be required.
Reco11111endation:
The licensee should provide an AAC source that meets the requirements of the SBO rule or an alternative method for coping with an SBO.
A full description of the proposed modifications, including the nature and objectives of the required modifications to meet the SBO rule, and a proposed schedule for implementation should be provided.
2.6 Quality Assurance (QA) and Technical Specifications (TS)
The licensee did not provide any information regarding QA programs and TS for SBO equipment.
TS for the SBO equipment are currently being considered generically by the NRC in the context of the Technical Specification Improvement Program and remains an open item at this time.
However, the staff would expect that the plant procedures will reflect the appropriate testing and surveillance
1
' requirements to ensure the operability of the necessary SBO equipment.
If the staff later determines that a TS regarding the SBO equipment is warranted, the licensee will be notified of the implementation requirements.
Recommendation:
The licensee should verify that the SBO equipment is covered by an appropriate QA program consistent with the guidance of RG 1.155. Further this verification should be documented as part of the package supporting the SBO rule response.
2.7 EOG Reliability Program The licensee stated that the EOG target reliability of 0.95 is to be maintained, however, no information was provided as to how this would be accomplished.
Reconunendation:
It is the staff's position that an EDG reliability program should be developed in accordance with the guidance of RG 1.155, Section 1.2.
Confirmation that such a program is in place or will be implemented should be included in the documentation that is to be maintained by the licensee in support of the SBO submittals.
2.8 Scope of Staff Review The SBO rule (10 CFR 50.63) requires licensees to submit a response containing specifically defined information. It also requires utilities 11 ---- to have baseline assumptions, analyses and related information used in their coping evaluation available to NRC."
The staff and its contractor did not perform a detailed review of the proposed procedure modifications which are scheduled for later implementation. Therefore, based on our review of the licensee's SBO submittals and the UFSAR, we have identified the following areas for focus in any follow-up inspection or assessment that may be undertaken by the NRC to further verify conformance with the SBO rule.
- a.
Hardware and procedural modifications,
- b.
SBO procedures in accordance with RG 1.155, Position 3.4, and NUMARC 87-00, Section 4,
- c.
Operator staffing and training to follow the identified actions in the SBO procedures,
- d.
EDG reliability program, meeting as a minimum, the guidelines of RG 1.155,
- e.
Equipment and components required to cope with an SBO are incorporated in a QA program that meets the guidance of RG 1.155, Appendix A,
- f.
Actions taken pertaining to the specific reco11111endations noted in this SE.
Additional areas may be identified following staff review of licensee's revised response to the SBO rule.
e e 3.0
SUMMARY
AND CONCLUSIONS The staff has reviewed the licensee's response to the SBO rule (10 CFR 50.63) and the TER prepared by the staff's consultant, Science Applications Internationa1 Corporation. Based on the staff's review of the licensee's submitta1s and the SAIC TER, the staff finds that the Surry Power Station does not conform with the SBO rule and the guidance of RG 1.155, and therefore recoRillends that the 1icensee reevaluate the areas of concern that have been identified in this SE.
Guidance for the licensee to review and implement the staff's recommendations is provided in RG 1.155, NUMARC 87-00 and the supplementary guidance (NUMARC 87-00 Supplementary Questions/Answers; NUMARC 87-00 Major Assumptions) dated December 27, 1989, which was issued to the in-dustry by NUMARC on January 4, 1990.
The staff's concerns that are identified in this SE should be addressed by the licensee, and a revised response submitted to the NRC within 60 days.
The licensee is expected to ensure that the baseline assumptions of NUMARC 87-00 are applicable to the Surry Power Plant. Also, the licensee should maintain all analyses and related information in the documenta-tion supporting the SBO submittal for further inspection and assessment as may be undertaken by the NRC to audit conformance with the SBO rule.
Dated: October 15, 1990 Princilal Contributor:
A. Toaston