Text

Responds to Request for Addl Info on SBO Sers.Util Reviewing Project Schedule for Implementation of Station Blackout Mods & Will Advise NRC of Results by 920316.Justification for Five Year Schedule Encl
	ML18151A935
Person / Time
Site:	Surry, North Anna
Issue date:	02/10/1992
From:	Stewart W; VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	; NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
	91-738A, NUDOCS 9202190097
	Download: ML18151A935 (60)
	v • d • e

t-1 e VIRGINIA ELECTRIC AND PowER COMPANY RICHMOND, VIRGINIA 23261 February 10, 1992 U.S. Nuclear Regulatory Commission Serial No. 91-738A Attention: Document Control Desk NL&P/GDM R6a Washington, D.C. 20555 Docket Nos. 50-280 50-281 50-338 50-339 License Nos. DPR-32 DPR-37 NPF-4 NPF-7 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 NORTH ANNA POWER STATION UNITS 1 AND 2 STATION BLACKOUT SAFETY EVALUATION REPORTS RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION Pursuant to the requirements of 10 CFR 50.63, Virginia Electric and Power Company provided proposals for ensuring that both North Anna and Surry Power Stations can withstand and recover from a station blackout (SBO) of a specified duration. These proposals were provided in our letter dated April 30, 1991 (Ser. No.91-242) and supplemented by our letter dated July 31, 1991 (Ser. No.91-402). The approach for each station was found acceptable by the NRG contingent upon the resolution of several open items and the justification of the project implementation schedule as detailed in your December 6, 1991 letter and attached supplemental SER.

Our response and proposed technical resolution of the open items is provided in Attachments 1 and 2 for Surry and North Anna Power Stations, respectively. As discussed in the attachments, we believe our request for categorization of both Surry and North Anna Power Stations as four hour coping duration plants with an Emergency Diesel Generator reliability of 0.950 is appropriate. The project will consist of the preparation of diesel generator specifications, procurement of three diesel generators and miscellaneous support equipment, development of engineering calculations and design implementation packages, construction of two diesel generator buildings, installation of equipment, and, finally, tie-ins to the transfer buses which must be performed sequentially during outages of sufficient duration*.

Our project schedule for the implementation of station blackout modifications is currently under review. We are performing an in-depth review of each specific project activity to determine if any enhancements to our previously proposed five year

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l I,. \ -2 e schedule can be made in order to meet the NRC staff's desired schedule. Our original schedule was based on the current five year outage forecast to facilitate equipment installation and transfer bus tie-ins, and provides for partial compliance with the SBO rule prior to overall project completion. This schedule provides for the installation of the alternate AC (AAC) diesel at North Anna prior to the October, 1994 Unit 1 outage, the first Surry AAC diesel prior to the September, 1994 Unit 2 outage, and the second prior to the September, 1995 Unit 1 outage. For North Anna, partial compliance with SBO would be achieved by the end of the April, 1995 Unit 2 refueling outage, since the 1J or 2H emergency bus could be powered by the AAC source. This assures that an SBO could be mitigated. For Surry, partial compliance with SBO would be achieved at the end of the September, 1995 Unit 1 outage, since emergency bus 1J or 2H could be powered by an AAC source. This assures that an SBO on either unit would be mitigated by powering either of these two buses. We will advise you of the results of our ongoing schedule review by March 16, 1992. The present justification for the five year schedules is provided in the attachments for your information.

If you have any questions or require additional information, please contact us.

Very truly yours,

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W. L. Stewart Senior Vice President - Nuclear Attachments cc: U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, N.W.

Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station Mr. M. S. Lesser NRC Senior Resident Inspector North Anna Power Station

STATION BLACKOUT SER.'S RESPONSE

'IO_REI)UEST FOR ADDITIONAL INFORMATION ,

REC'D W/LTR IJI'D 02/10/92 **** 9202190097

-NOTICE-THE ATIACHED FILES ARE OFFICIAL RECORDS OF THE INFORMATION &

REPORTS MANAGEMENT BRANCH.

THEY HAVE BEEN CHARGED TO YOU FOR A LIMITED TIME PERIOD AND MUST BE RETURNED TO THE RE-CORDS & ARCHIVES SERVICES SEC-TION P1-22 WHITE FLINT. PLEASE DO NOT SEND DOCUMENTS CHARGED OUT THROUGH THE MAIL. REMOVAL OF ANY PAGE(S) FROM DOCUMENT FOR REPRODUCTION MUST BE RE-

.FERR ED TO FILE PERSONNEL .

.-NOTICE-

ATTACHMENT 1 RESPONSE TO STATION BLACKOUT RULE SURRY POWER STATION Virginia Electric and Power Company

r ' ..t RESPONSE TO STATION BLACKOUT RULE RESOLUTION OF OPEN ITEMS SURRY POWER STATION A. Station Blackout Duration (SSER Section 2.1)

NRC Evaluation:

The staff concurs with the licensee regarding the electrical independence of Surry station switchyards based on the switchyard modifications. However, as discussed in SE Section 2.1, upon loss of the reserve station service transformer RSST-C, the only method of energizing the second division would be by manually tying 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 "13."

The staff does not agree with the licensee's determination of the offsite power design characteristic group of "P2*." The staff finds this to be "P2" based on independence of offsite power classification of "13," a SW classification of Group "1" and ESW classification of Group "4."

The licensee correctly identified the emergency AC configuration group "D."

The staff finds the selection of lower EOG target reliability (0.95) than that required by Regulatory Guide (RG) 1.155 to be acceptable, since the proposed AAC source for Surry, Units 1 and 2 is two independent non-safety grade diesel generators which can provide power to the safety-related buses at the station and has sufficient capacity and capability to power one division of the LOOP loads of each unit.

Based on the above, the staff finds the minimum SBO coping duration to be 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months rather than 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months as determined by the licensee.

Response

In the Virginia Electric and Power Company letter of April 30, 1991, it was determined (utilizing NUMARC 87-00 Section 3) that Surry could be categorized as having an independence of off-site power group of 11/2, an offsite AC power design characteristic group of P2* and an EAC power configuration group of D.

The Staff Evaluation included in the Supplemental SER issued with the NRC letter dated December 6, 1991 disagreed with Virginia Electric and Power Company's selection of the independence of offsite power group of 11/2 and has determined it to be 13. Thus the Staff has determined that the offsite power design characteristic group of P2* is not applicable to Surry since this category is not allowable for 13 plants and have stated that this classification should be

P2. As a result, the NRC has concluded that Surry is not a 4 hour4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months coping plant 1

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as would be allowable for P2* plants (Ref. NUMARC 87-00, table 3-9) but instead is an 8-hour plant. Virginia Electric and Power Company believes that we have correctly categorized both the independence of the offsite power group and the offsite power design characteristic group as I 1/2 and P2*, respectively, and would like to further clarify our position.

The NRC refers to their previous Safety Evaluation (Section 2.1) in which they discussed the loss of RSST-C. This issue was discussed because the NRC did not (at that time) agree that Surry's switchyards were independent. This discussion is only applicable for I group determination provided that a station does not have electrically independent switchyards. Since Virginia Electric and Power Company has demonstrated (and the NRC has agreed) that the 230 and 500 kV switchyards are electrically independent, then the discussion of loss of RSST-C is no longer applicable.

NU MARC 87-00 Section 3.2.1, part 1D, provides guidance which is acceptable to the NRC for determining I group. Since the switchyards at Surry are electrically independent, the answer to Question "A" of Section 3.2.1 is NQ and, therefore, Surry is categorized an I 1/2 plant. In addition, the answers to questions "8(1 )" and "8(2)" are also NQ since the normal source of AC power for the safe shutdown buses is the RSSTs and not the main generator, tending to reinforce the I 1/2 categorization.

Also, due to independence and separation of the Surry switchyards, the answer to statement 11-1 in table 5 of Reg. Guide 1.155 is clearly "yes," therefore, per R.G. 1.155, Surry can be categorized as having an independence of offsite power group of 11. Statements under 11-2 are not applicable since the table clearly allows a YES answer to 11-1 or 11-2. Likewise, the statements under 12 and 13 are not applicable since the switchyards are electrically independent.

Since we have chosen to use the NUMARC methodology, NUMARC 87-00 Section 3.2.1, part 1E, paragraph B, Table 3-5b (for Hurricane Exposed Plants) was used to determine the "Offsite AC Power Design" group. With a Severe Weather (SW) classification of group 1 and an Extremely Severe Weather (ESW) classification of group 4, Surry is clearly an Offsite AC Power Design group P2*.

In accordance with NUMARC 87-00, Section 3.2.5 - Table 3.8, an Offsite AC Power group of P2* with an EAC group D yields a 4 hour4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months coping duration with an EDG target reliability of 0.975.

Based on arguments previously presented (and accepted by the NRC) the target EOG reliability can be reduced to 0.95. The requested result is a coping duration of 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months with a target EOG reliability of 0.95 .

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B. Proposed AAC Power Source (SSER Section 2.2)

NRC Evaluation:

The staff finds the licensee's proposed addition of two non-safety grade diesel generators as an AAC power source to be acceptable. However, the licensee should provide confirmation that the proposed AAC power source meets the other criteria of Appendix 8 of NUMARC 87-00, specifically items 8.8, 8.9, 8.1 O, 8.11, 8.12, and 8.13 and RG 1.155, Position C.3.3.5.5.

The staff does not agree with the S80 duration of 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months . The licensee needs to modify the S80 duration from 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months to 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months (see Section 2.1) and confirm that each day tank will be sized to allow the diesel to run for the S80 duration of 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

Also, the automatic connection of the AAC diesel generators to a pre-selected emergency bus is not acceptable to the staff since it violates RG 1.155, Section 3.3.5.3. The staff finds the use of existing automatic load sequencing acceptable provided the licensee demonstrates by test that all S80 equipment can be powered from an AAC source within 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months .

Response

The Alternate AC sources proposed for Surry are planned to meet the

8.8 applicable criteria specified in NUMARC 87-00 Appendix H. In addition to the design criteria provided in our previous submittals, the following confirms our plans to meet the guidance provided in items 8.8, 8.9, 8.10, 8.11, 8.12, and 8.13, and R.G. 1.155 position 3.3.5.5.

The following features of the AAC design should minimize the potential for common cause failure:

1. Each AAC power system shall be equipped with a DC power source that is electrically independent from the Station's preferred and safety-related power system. Certain breakers required for S80 conditions will utilize DC control power from the existing station 1E batteries. The existing station 1E batteries have been found acceptable in the SSER Section 2.4. We presently plan that there will be a separate DC power system including batteries for each S80 AAC diesel.

2. Each AAC power system shall be equipped with an air start system that is independent of the preferred safety-related EOG air start system and the blacked-out unit's preferred and safety-related power supply. The source of air to the AAC diesel air start systems receivers may also be available to support the station or other functions in the AAC diesel building, but the starting components will not be interconnected in a manner which would allow station air problems to render an S80 AAC diesel unable to start.

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3. Each AAC power system shall be provided with a fuel oil supply that is separate from the fuel oil supply for the onsite emergency AC power system. A separate day tank will be supplied for each diesel which is fed from the onsite storage tank. The fuel oil supplied to the AAC day tank will be sampled and analyzed consistent with applicable standards prior to transfer to the day tank. It should be noted that the size of the day tank which would be required for an eight hour duration may be larger than acceptable based on insurance and other considerations. This may impact the preliminary design which is being pursued.

It should be noted that though these machines are not safety related, we are trying to install them in a highly reliable configuration. The fuel tank for a four hour coping duration would be about 1200 gallons, which is close to the guidance provided for safety related machines supplied in NUREG 0800, Standard Review Plan, Section 9.5.1, page 47. Should an 8 hour9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months duration be required in order to have a 0.95 EOG reliability, we would be required to install a significantly larger day tank. This is acceptable for these machines, but is not as desirable as using a shorter duration and therefore smaller tank, which would be possible with a 4 hour4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months duration and 0.95 reliability.

4. Should the *AAC*power source be an identical machine to the emergency onsite AC power source, active failures of the emergency AC power source will be evaluated for applicability to the AAC source and corrective action taken to reduce subsequent failures.

5. No single point vulnerability should exist whereby a likely weather-related event or single active failure could disable any portion of the onsite emergency AC power sources or the preferred power sources, and simultaneously fail the AAC power sources.

The AAC Diesel Generator Building design will meet or exceed the requirements of the Virginia Building Code which is based on the Building Officials and Code Administrators (BOCA) Code. This should provide sufficient protection against the effects of likely weather related events but will not provide tornado missile. protection or protection against a seismic event. The building will be a separate structure located within the protected area with a floor elevation higher than the surrounding area. The building will be located northeast of the Unit 2 Turbine Building in the yard area bordered by the Condensate Polishing Building, the auxiliary boiler building and the new rad waste facility. This location will provide some natural protection against severe weather.

Station interface for AAC diesel support systems will be by elevated utilities which will be enclosed to provide adequate protection from severe weather. Adequate electrical protection will be provided for the generator portion of the AAC source, its associated equipment and cables. This protection should prevent any single failure from simultaneously affecting any EAC source or preferred power source and the AAC source.

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6. Each AAC power system will be capable of operating during and after a station blackout without any support systems powered from the preferred power supply or the blacked-out unit's power sources affected by the event.

The systems required for operation of each AAC source will be powered from a dedicated bus powered by their respective AAC diesel and/or from dedicated batteries.

7.

Modifications and maintenance activities performed on the AAC sources will be conducted in accordance with existing Station procedures. The AAC diesels and support systems will be designated as nonsafety related with special regulatory significance (NSQ) and will be included in the post modification/maintenance testing program.

B.9 Each AAC source will be sized to carry the required loads associated with one safety division, of either unit, in the event of a loss of offsite power (LOOP). The net available capacity of a machine based on a 2000 hour0.0231 days 0.556 hours 0.00331 weeks 7.61e-4 months rating may be less than the approximate 3000 kilowatts stated in our earlier letters but should be about that value. An actual net rating will not be available until after purchase and installation.

The proposed design will provide the automatic alignment of one of the AAC sources to the E transfer bus and the other AAC source will automatically align to the F transfer bus. These buses supply power to the safety-related buses at the station and once the diesels are aligned to the transfer buses they will be manually aligned to one of the emergency buses in each unit. Once the emergency buses are energized, the existing automatic sequence can be used to power required loads. The AAC sources will not be automatically aligned to the emergency buses. The required loads are those loads necessary to maintain the plant in a safe shutdown condition following an SBO.

B.1 O Each AAC power source will be started and brought to operating conditions once every three months, following manufacturer's recommendations and/or in accordance with plant-developed procedures. A timed start test (within the time period specified for blackout conditions) and a rated load capacity test of each diesel will be performed once per combined plant refueling cycle during a refueling outage of either unit.

It should be noted that diesel loading may be simulated other than by powering actual plant loads.

B.11 Surveillance and maintenance procedures will be developed for both AAC sources in accordance with Station administrative procedures. Maintenance procedures will incorporate manufacturer recommendations, however, they may be modified based on corporate experience and plant information.

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y I _,J, B.12 An initial test program will be developed to demonstrate the load carrying capability and availability of each AAC diesel generator. This test will demonstrate the availability to power necessary shutdown buses within ten minutes following a station blackout. The actual test loads may be different from the shutdown loads powered during the event.

B.13 Both AAC sources will be included in the existing EDG reliability program (as described in section K of this submittal) or a similar program. The AAC reliability will be maintained at or above 0.95 as defined by the Virginia Electric and Power Company EDG reliability program which is in accordance with NSAC-108 and R.G. 1.155 position C.3.3.5.5.

C. Condensate Inventory for Decay Heat Removal (SSER Section 2.3)

NRC Evaluation:

Based on its review and the results of its consultant's analysis, the staff agrees with the licensee's conclusion that the emergency CST as required by TS will have sufficient water for coping with a 4- or 8-hour SBO event. Therefore, the staff considers this condensate inventory issue resolved.

Response

Resolved.

D. Class 1 E Battery Capacity (SSER Section 2.4)

NRC Evaluation:

The staff finds this to be acceptable based on the proposed AAC sources and availability of one charger within 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months .

Response

Resolved.

E. Compressed Air (SSER Section 2.5)

NRC Evaluation:

Since the compressed air capacity is still under review, the staff finds this issue to be an open item .

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Response

Instrument air will be made available from a source other than air bottles to the atmospheric steam dump valves (PORVs). Although the PORVs are not specifically needed to remove decay heat (this function can be accomplished by the main steam safety valves), we believe it is desirable to provide instrument air to them to give the operator added flexibility in coping with the event.

There are several options available to Surry Power Station in providing instrument air during an SBO. At present we plan to develop station procedures to power a normal bus feeding either one of the two station air compressors.

No bottles or accumulators will be provided due to their size and cost.

F. Effects of Loss of Ventilation (SSER Section 2.6}

NRC Evaluation:

Based on its review and its concerns discussed in the above Sections 2.6.a and 2.6.b, the staff has not been able to conclude that the licensee's analyses of the effects of loss of ventilation in the control room complex and the ESGR complex are acceptable. The staff considers that this issue with respect to the effects of loss of ventilation at the Surry plant is not fully resolved; therefore, this issue is identified as an open item .

Response

Additional concerns were raised by the staff on the evaluations performed for several of the areas of the plant that were analyzed for the effects of the loss of ventilation event. Clarification for each of the areas is provided below.

1. Control Room Complex and Emergency Switchgear Room Complex The staff questioned the basis for the initial room temperatures which were assumed in the ventilation analysis on the control and emergency switchgear room (CR/ESGR) complex. In addition, concern was expressed over the absence of a procedural commitment to open control room cabinet doors after the onset of an SBO.

The initial temperatures assumed for the control and emergency switchgear room complex were based on Assumption 2.2.1 of NUMARC 87-00 which states that just prior to the event all plant equipment is either normally operating or available from a standby state. Air-conditioning for the CR/ESGR is accomplished by the CR/ESGR air handling and cooling

system. Upon completion of the control room complex air-conditioning upgrade modification there will be five chillers which are able to operate both units redundant air handling trains, only two chillers are needed at

any one time. Operability of the air-conditioning equipment for the 7

CR/ESGR complex is governed by Technical Specifications which require that two air-conditioning trains be operable (for both units).

Therefore, it is reasonable to assume that CR/ESGR air-conditioning is functioning properly just prior to an SBO event. Control of the CR/ESGR area temperature is a function of the setpoint of the chiller chilled water outlet which is held at a constant value. The chillers load and unload to maintain this constant temperature in response to varying CR/ESGR heat load, thereby maintaining a constant area temperature. Therefore, unless a chiller becomes inoperable, a constant temperature will be maintained.

Based on the above, the analysis concluded that the temperatures resulting from a loss of forced ventilation in the CR/ESGR areas was less than or equal to 110°F in all cases. Therefore, since the final temperature in the CR/ESGR is 10°F less than the Technical Specification limit which is considered the operability limit of the equipment, no operator action to open doors is required.

However, since Virginia Electric and Power Company will become a 1 O minute AAC plant in order to resolve questions regarding canal inventory, this point becomes moot and no commitments on initial temperature are necessary.

2. Charging Pump Cubicle Resolved.

3. Auxiliary Feed Pump House Resolved.

G. Reactor Coolant Inventory (SSER Section 2.7}

NRC Evaluation:

The staff finds, based on the availability of AAC power within 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months following the onset of an SBO event, that the licensee has adequate coping capability to maintain reactor coolant inventory for an SBO duration of 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

Response

Resolved, however, we request a duration of four hours with a target EDG reliability of 0.95 .

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H. Canal Inventory (SSER Section 2.8)

NRC Evaluation:

In order to provide AC power to the condens~r isolation valves within 30 minutes, the licensee should consider a 1a-minute AAC power source per RG 1.155, Section C.3.3.5.3. The licensee should commit to performing a test to demonstrate that the AAC power source can power the shutdown buses within 10 minutes of the onset of an SBO. In that case, no coping analysis is required.

Otherwise, the licensee should provide assurance of net positive suction head for heat sinks by listing the condenser isolation valves and other valves not powered by the AAC source in an appropriate procedure and by identifying actions required to ensure these valves are fully closed by providing positive indication (local, remote, etc.) independent of the Class 1E power source. The supporting documentation should be included with other information to be maintained by the licensee in support of its SBO submittals. -

Response

The staff requested the licensee consider committing to a 1O minute AAC per R.G. 1.155 Section C.3.3.5.3, since condenser isolation is desired within 30 minutes of the onset of an SBO.

Virginia Electric and Power Company will commit to providing a 1O minute AAC power source and conducting a test to demonstrate that the AAC source is available to power the shutdown buses within 1O minutes after the operator has ascertained that an SBO condition exists and that emergency diesel generators can not be started. The determination of the existence of an SBO will be in accordance with station procedures, which will also identify required actions to conserve canal inventory.

The AAC source will be automatically loaded onto the transfer buses and then manually loaded to the emergency buses where the existing automatic sequencing can be used to power shutdown equipment I. Proposed Modifications (SSER 2.9)

NRC Evaluation:

The staff considers the 5-year time frame to complete the modifications and procedure changes as excessive. The licensee should implement the changes within 3 years, or provide a detailed justification as to why a longer time frame is required. The justification should include a detailed schedule of the different phases of the project. Also, the licensee should consider the receipt of this SSE

- as the starting time, since the staff has accepted the proposed AAC source .

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Response

Virginia Electric and Power Company had previously requested 5 years following the receipt of favorable notification of the proposed approach to compliance with 10CFR50.63 to complete the necessary modifications and procedural changes. As stated in the previously referenced Supplemental SER, the staff considered the 5-year time frame to be excessive and has directed that Virginia Electric and Power Company implement the changes within 3 years, or provide a detailed justification (including a detailed schedule depicting various phases of the project) as to why 5 years is required. We, therefore, offer the following justification as to the need for 5 years to complete this project.

Attachments:

A. SBO Projects Schedule B. Present Transfer Bus Configuration C. Transfer Bus Configuration - Pre-1994 Unit 2 outage D. Transfer Bus Configuration - Post-1994 Unit 2 outage E. Transfer Bus Configuration - Pre-1995 Unit 1 outage F. Transfer Bus Configuration - Post-1995 Unit 1 outage/

Pre-1996 Unit 2 outage G. Transfer Bus Configuration - Post-1996 Unit 2 outage Virginia Electric and Power Company proposes to sequence this work into seven main phases (see Attachment A) consisting of the following major activities (some overlapping of phases will occur):

Phase 1 - Prepare procurement specifications for Jan. 92 -Oct. 93: SBO diesel, 4 kV switchgear, MCCs, SBO diesel control panel and other equipment, evaluation of bids, place P.O.s, fabricate and deliver equipment.

Phase 2 - Perform engineering activities Jan. 92 .: April 94: including finalizing of design, preparation of engineering calculations, preparation of engineering drawings, and completion of design change packages .

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J Phase 3 - Pre-1994 Unit 2 outage construction.

Aug. 93 - Oct. 94: This will include construction of SBO Building, installation of SBO diesel No.

1, installation of 4160V SBO diesel No. 1 bus and associated 4160V breakers including tie breaker to SBO diesel No. 2 bus, installation of D to E tie breakers in normal switchgear room (not including tie-in to D and E buses), installation of bus work and cable from SBO Building through the plant and into normal switchgear room, performance of associated testing.

Phase 4 - Construction during 1994 Unit 2 outage Sept. 94 - Nov. 94: - This will include final tie-in to E bus, and associated testing.

Phase 5 - Pre-1995 Unit 1 outage construction.

Ending July 95: This will include installation of SBO diesel No. 2, installation of 4160V SBO diesel No. 2 bus and associated 4160V breakers, installation of F tie breaker in normal switchgear room (not including tie-in to F bus), installation of cable and bus work from the SBO Building through the plant and into the normal switchgear room and performance of associated testing.

Phase 6 - Construction during 1995 Unit 1 outage.

Oct. 95-Dec. 95: This will include final tie-in to D bus, and associated testing.

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Phase 7 - Construction during 1996 Unit 2 outage.

Feb. 95-April 96: This includes final tie-in to F bus and associated testing.

NOTE: The preparation of procedures and personnel training, even though not shown as specific milestones on the attached schedule, will be completed as required to support the various phases of the project and are expected to comprise a significant effort.

Justification for the proposed 5-year completion for this project can, therefore, be summarized as follows:

1. The procurement and fabrication time, including vendor selection for the major equipment, is extensive. Fabrication and delivery of SBO diesel after engineering approval of drawings is anticipated to take approximately 12 months.

2. Extensive pre-outage construction is required prior to the final station tie-ins to transfer buses D, E, and F being made.

3. The tie-ins to the D, E, and F transfer buses have to be properly sequenced since one offsite source to at least one emergency bus is disabled during any transfer bus outage. Also, tie-ins to the transfer buses require extensive changes to existing breaker logics, undervoltage protection and bus relaying schemes. There are also extensive changes required to accommodate new 4160V breaker interlocks. This will result in significant changes in and additions to plant procedures which will require significant personnel training.

4. Only one transfer bus should be worked per any given outage due to the significant testing required and to minimize operator confusion with regard to complexity of breaker lineups and testing sequence required for a given condition. This should minimize the potential for low power/offline risk. If work were performed on more than one transfer bus during an outage, it is expected that this would significantly increase the required length of the outage.

NRC INFORMATION NOTICE 91-68 indicates the need for careful planning during evolutions similar to those planned for SBO installation.

5. Since F transfer bus provides power to emergency buses 1H and 2J, it is desirable that this bus be worked during a Unit 2 outage. If

F bus is completed last (i.e. after the tie-ins to buses D and E are made to SBO diesel No. 1) and during the Unit 2 outage in 1996, this will assure that at least one safety bus of each unit (i.e. bus 1J and 2H) will have the capability of being powered from the in-12

service AAC source (i.e. SBO diesel No. 1). Also, when F bus is removed from service safety bus 1H still has a dedicated EOG that can supply power to that bus while the tie-ins to F bus are being completed. It should be noted that Surry will require a temporary waiver of Technical Specification requirements for Unit 1 since when F bus is removed from service, Unit 1 will be in an LCO.

6. Partial compliance with SBO can be achieved at the end of the Unit 2 1994 outage and 1995 Unit 1 outage since bus 1J or 2H can be powered by an AAC source, thus assuring that an SBO on either unit can be mitigated by powering of either of these two buses.

7. A recent event at Davis-Besse Unit 1 on October 14, 1991, during implementation of work associated with their SBO diesel underscores the need to proceed prudently on such a complex project. The failure of an auxiliary transformer associated with the SBO diesel generator occurred when it was initially energized from the Station 4160V system causing extensive damage to the transformer, switchgear, and associated bus work.

8. In conjunction with implementation of the Surry SBO modifications, Virginia Electric and Power Company is also proceeding with simultaneous implementation of SBO modifications at North Anna. Compressing the implementation schedule into 3 years would tend to exacerbate an already complex project coordination effort.

J. Quality Assurance (QA) and Technical Specifications (SE)

(SSER Section 2.10)

NRC Evaluation:

The licensee needs to address this recommendation.

Response

The nonsafety systems and equipment being relied upon to meet the requirements of the SBO Rule will be included in a QA program which meets the requirements of R.G. 1.155 Section 3.5, and Appendices A and B.

The inclusion of the new SBO equipment in a QA program which governs their associated design, specification, and testing activities in addition to the development and maintenance of a periodic testing program with trending and root cause evaluation (as discussed below) should be adequate to assure their proper operation; therefore, there is no need to apply Technical Specifications to the SBO equipment. This position is further reinforced by the fact that per

NUMARC 87-00 Section 7.2.4 SBO is not considered as a design basis event 13

' .J (DBE). Documentation standards for equipment operability are not to be as rigorous as are typically required to meet the design basis requirements of 10CFR50.49 and suitable independence will exist between the SBO equipment and the safety-related systems, required to respond to a DBE, such that there is no potential for common cause failure.

K. EOG Reliability Program (SSER Section 2.11)

NRC Evaluation:

The licensee needs to address this recommendation.

Response

The reliable operation of the Surry onsite emergency AC power sources has been ensured by the establishment and implementation of the Station EDG Reliability Program. The EDG Reliability Program is designed to monitor and maintain the reliability level of the EDG power sources over time for assurance that the selected reliability levels are being achieved. The Virginia Electric and Power Company EDG Reliability Program is consistent with the guidelines of NUMARC 87-00, Appendix D (EDG Reliability Prog'ram), and includes the .1 *I I

following elements or activities:

1. Unit EDG reliability target levels are consistent with R.G. 1.155, Table 2.

The presently selected EDG reliability target for the Surry Units is 0.975; monitoring the calculating of this reliability target is performed whenever EDG start or load-run failures occur, and on a monthly basis. These values are compared to the following exceedance trigger values established in the EDG Reliability Program:

3 failures in 20 demands 4 failures in 50 demands 5 failures in 100 demands In addition, if an individual EDG experiences four or more failures in its last twenty five demands, it is deemed a problem EDG. Should this occur, accelerated testing will be performed in accordance with the program.

2. The surveillance testing and reliability monitoring programs are designed to track and monitor EDG performance, and to support preventive and corrective maintenance activities. EDG availability is also monitored and compared to established goals on a monthly basis.

3. The EDG Reliability Program also ensures that the target EDG reliability "is* being achieved, that an appropriate maintenance program is being implemented, and that the capability for failure analysis and root cause investigations are provided. Graded corrective actions are implemented

14

if one or more of the exceedance trigger values, as described in 1 above, are met.

4. The EDG Reliability Program implements an information and data collection system to service elements of the program, and monitors achieved EDG reliability levels against target values.

5. The EDG Reliability Program identifies responsibility for the major program elements. Management overview for ensuring that reliability levels are being achieved and that the program is functioning properly has also been implemented.

The new SBO AAC diesel generators will be included in either this or a similar program.

The resolution of Generic Issue B-56, Emergency Diesel Generator Reliability, is currently under consideration and review within the NRC and between the NRC and the industry. Our current program is designed to assure that proper attention to diesel reliability is maintained and that corrective actions are taken when necessary. We will continue to review this program as required. However, we will not make a commitment relative to Reg Guide 1.155 at this time. We will however, monitor the resolution of B-56 and respond to it in a manner that we deem reasonable .

15

1 991 1992 1993 1994 1995 NRC SER I I N,ANNA I I

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ATTACHMENT G

ATTACHMENT 2 RESPONSE TO STATION BLACKOUT RULE NORTH ANNA POWER STATION VIRGINIA ELECTRIC AND POWER COMPANY

RESPONSE TO STATION BLACKOUT RULE RESOLUTION OF OPEN ITEMS NORTH ANNA POWER STATION A. Station Blackout Duration (SSER Section 2.1)

NRC Evaluation:

The staff agrees with the licensee's determination of the independence of offsite power Group "I 1/2" based on the proposed addition of a bus tie between the transfer buses "D" and "E". However, the staff finds the proposed SBO duration to be 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months rather than 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months in accordance with Table 2 of RG 1.155 .

. The licensee's determination of a 4-hour coping duration is based not upon the RG 1.155 guidance, but rather upon the NRC staff's agreeing to a relaxation of the EOG target reliability at the Dresden station from 0.975 to 0.95. However, at the Dresden station, the relaxation of the EOG target reliability from 0.975 to 0.95 did not result in a corresponding decrease in the required SBO duration from 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months to 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months , as it would at the North Anna station. Therefore, the two situations are different. The staff concludes that the SBO duration (based on an EOG target reliability of 0.95) at North Anna should remain at 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

Since the licensee states that the proposed AAC source at North Anna will be available in 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months , and can power a full division of safe shutdown equipment, the staff would not expect any significant difference between an 8-hour versus 4-hour SBO analysis.

Response

In the Virginia Electric and Power Company letter of April 30, 1991, to the NRC it was determined, utilizing R.G. 1.155 and NUMARC 87-00, Section 3 that North Anna could be categorized as a P2 plant with a 4 hour4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months SBO duration and an EOG target reliability of 0.975. This was based upon a severe weather (SW) classification of Group 2, an extremely severe weather (ESW) classification of Group 4, an independence of offsite power classification of I 1/2, and an emergency AC power configuration (EAC) Group C. It was further stated that

Virginia Electric and Power Company requested a relaxation of the target 1

reliability from 0.975 to 0.95 based on the precedent for such a relaxation granted for Commonwealth Edison's Dresden Units 2 and 3 and Quad Cities Units 1 and 2 in the SERs issued for those stations.

The Staff Evaluation included in the Supplemental SER issued with the NRC letter dated December 6, 1991 agreed with the Virginia Electric and Power Company determination of the Independence of Offsite Power Group I 1/2 based on the proposed addition of a bus tie between transfer buses D & E.

However, the staff disagreed with the SBO duration of 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months and found it instead to be 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months and 0.95 EOG reliability in accordance with Table 2 of R.G. 1.155 and thus the issue of relaxation of the target reliability was considered unacceptable. Therefore, we believe that the staff interpreted this as a request for relaxation of both reliability and duration instead of as a request for relaxation of only either one of the two items.

It appears that there was confusion in the manner in which this issue was presented in our April 30, 1991, letter and we would, therefore, like to restate

and thus clarify our position.

The North Anna coping duration category was determined in accordance with NUMARC 87-00 Section 3, R.G. 1.155 Section 3.1 and based on the addition of bus ties between transfer buses D and E as part of the overall North Anna SBO design.

Based on the above, it has been determined for North Anna that:

a) Site susceptibility to grid-related loss of offsite power events is not a

-factor since North Anna is not expected to exceed the once per 20 site-year limit per NUMARC 87-00, Section 3.2.1, part 1.A.

b) The ESW group is 4. This was determined by utilizing NUMARC 87-00 Table 3-2. It should be noted that ESW 4 is based on storms with wind speeds >125mph, expected at North Anna at an annual frequency of

.0034 per NUMARC 87-00 Table 3-2. From NUMARC 87-00 Table 3-1, North Anna can be considered a borderline ESW 3 plant since its ESW4 2

< I classification is only slightly greater than an ESW 3 classification which results in an annual ~ 125 mph wind speed frequency of .0033.

c) The SW group is 2. From NUMARC 87-00, Section 3.2.1, Part 1.C and Table 6 of R.G. 1.155, this was determined by (1.2 x 1o-2)h 3 + ch 4 = .00337 where b = 12.5 (since transmission lines are separated by at least 1/4 mile commencing at a point 1 mile from the plant).

C=O h1 = 15 (NUMARC Table 3-3) h2 = .0000367 (NUMARC Table 3-3) h3 = .08 (NUMARC Table 3-3) h4 = 0 (NUMARC Table 3-3)

Utilizing Table 3-4 from NUMARC 87-00 and Table 6 from R.G. 1.155, a severe weather frequency of .00337 yields a SW Group 2 classification.

Again, it should be noted that North Anna can be considered a borderline SW Group 1 plant from NUMARC 87-00 Table 3-4 or R.G.1.155 Table 6, since its SW 2 classification is only slightly greater than an SW 1 classification. An SW 1 classification would result from a frequency of

.0033.

d) North Anna is categorized as I 1/2. This was determined from NUMA RC Section 3.2.1, Part 1.D since the response to questions 8(1) and 8(2) are NQ.

These responses are considered NQ because the normal supply to the emergency buses is via the reserve station service transformers and not the main generators. The NRC staff has agreed with this evaluation.

e) The Offsite AC Power Design Characteristic Group is classified as P2.

This results from utilizing NUMARC 87-00 Table 3-5a for I 1/2 sites with ESW Group 4 and SW group 2 classifications.

3

It should be noted, as previously mentioned, that since North Anna can be considered to be a borderline SW Group 1 and ESW Group 3 plant, it can be further considered to be a borderline P1 plant since from NUMARC 87-00 Table 3-5a, an ESW 3 and SW 1 classification would yield an offsite design characteristic group classification of P1.

f) The emergency AC power configuration is classified as EAC Group C.

This was determined as follows:

North Anna has a total of 4 emergency diesel generators (EOGs) (2 per unit) of which 2 EOGs (1 per unit) are required for safe shutdown loads following a LOOP. Therefore, from NUMARC 87-00 Table 3-7 or R.G.

1.155 Table 3 (on a per unit basis), since North Anna requires one dedicated EOG for safe shutdown and has a total of 2 dedicated EOGs available, the EAC group can be selected as C .

It should be noted that when the SBO diesel generator is added it will have the ability to access either emergency bus of either unit. Then on a two unit bases, it could be reasoned that North Anna is similar to an EAC Group B plant since (per NUMARC 87-00 Table 3-7 or R.G. 1.155 Table

3) North Anna would then have a total of 5 supplies available (4 EOGs and 1 SBO AAC diesel generator) and would require two supplies to accommodate both units safe shutdown loads.

g) Utilizing the guidelines of NSAC 108, the EOG reliabilities (as of 3/15/91) have been calculated to be:

Last 20 demands - .989 Last 50 demands - .986 Last 100 demands - .990 h) The allowed EOG target reliability can be selected as either .95 or .975 from NUMARC 87-00 section 3.2.4 .

4

These target reliabilities are allowed since North Anna is an EAC Group C site and since the calculated reliabilities exceed those threshold reliabilities in NUMARC 87-00 Section 3-2.4(1) and R.G. 1.155 Section-1.1.3.

_i) :, - The-coping _duration category for North Anna is determined to be either:

8 hour@ .95 EOG reliability or 4 hour4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months @ .975 EOG reliability The above options are allowed per NUMARC 87-00 Table 3-8 or R.G.-

1.155 Table 2 for P2, EAC Group C plants.

As a result of the above, Virginia Electric and Power Company can categorize North Anna as a 4-hour coping duration plant with an EOG target reliability of 0.975. Virginia Electric and Power Company further requests relaxation of the target reliability from 0.975 to 0.950 based on the following considerations:

1. The NRG, in the SERs issued for Commonwealth Edison's Dresden Units 2 and 3 and Quad Cities Units 1 and 2 plants, has allowed the utility to relax the target reliability on the EDGs from 0.975 to 0.95. Dresden and Quad Cities are classified as P1, EAC Group D plants. Accordingly, the minimum target reliability permitted by the guide is 0.975 for each site.

The staff's acceptance of the lower EOG target reliability was limited to EOG configurations similar to Dresden and Quad Cities contingent upon the following:

a. _l'The AAC power source is sized to power the complete contingent of safety-related and nonsafety-related loads associated with one safety division of each unit simultaneously that are normally expected to be available for the loss of offsite power (LOOP) condition.

b. "The AAC power source is connectible to all EOG buses of all the units."

5

c. "The AAC source should be diverse from existing EDGs.

Lack of diversity must be justified by addressing how common mode failures are minimized."

Since the Dresden and Quad Cities plants are EAC Group D designs, a

station blackout must be postulated to affect both units (NUMARC 87-00, Section 2.3.1 (2)). Accordingly, an AAC power source will be installed with sufficient capacity to power one safety division of each unit in the event of a LOOP. At North Anna, an AAC will be installed which will have sufficient capacity to power the LOOP loads associated with one safety division of either unit. This is consistent with the above criterion since a station blackout at North Anna is postulated to occur on only one unit (NUMARC 87-00, Section 2.3.1 (2) and 10CFR50.2). This arrangement provides reliability equivalent to that afforded by the proposed Dresden and Quad Cities design .

At Dresden and Quad Cities, the AAC source connects to a single bus from which ties are made to the safety-related buses of each unit. This provides AAC access to all EDG buses at the site. The proposed North Anna design would permit the connection of the AAC source to the three transfer buses that supply power to the safety-related buses at the station. This design similarly permits the AAC source to access all EDG buses of each unit consistent with the above criteria.

The proposed North Anna design provides both diversity and independence (Reg. Guide 1.155, Section 3.2.5) among the AAC and EDGs as follows:

- The AAC diesel will be a more recent design than the existing EDGs .

. - . The EDGs and AAC diesel. will not share common structures .

6

., I

- The EDGs and AAC diesel will not share common support systems (e.g. fuel oil day tank, cooling, control power, etc).

- Power and control cables for the EDGs and AAC diesel will be separated where required.

- The EDGs and AAC diesel will not share mechanical and electrical protective devices.

- The AAC diesel will not normally be connected to the EOG buses or the transfer buses.

An alternate AC (AAC) power source will be utilized at North Anna which meets the criteria specified in Appendix B to NUMARC 87-00.

The AAC power source will be available to the blacked-out unit within one hour following the onset of a station blackout event. This AAC source will have sufficient capacity to operate all systems (one safety division) necessary for coping with a station blackout for the required SBO duration of 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months . An AC independent coping analysis was performed for the one hour required to connect the AAC power source to the blacked-out unit. The results of this analysis indicate that reactor core uncovery will not occur within one hour.

2. As previously discussed, North Anna's ESW classification of Group 4 was chosen based on an annual expectation of storms > 125 mph of 0.0034. The corresponding annual expectancy of an ESW 3 plant is slightly less than North Anna at 0.0033. North Anna can thus be considered to be a borderline ESW 3 plant. Also, North Anna's SW classification of Group 2 was chosen based on a calculated estimated frequency of loss of offsite power due to severe weather of 0.00337. The

. corresponding expected frequency of an SW 1 plant is slightly less than North Anna at 0.0033. North Anna can thus be considered to be a borderline SW 1 plant. It can, therefore, be reasoned that North Anna is a borderline P1 plant since utilizing NUMARC 87-00 Table 3-5a and 7

' 1 considering an ESW 3 and SW 1 classification, would result in an offsite design characteristic group of P1. Since North Anna is an EAC Group C plant, a P1, EAC Group C plant would be classified as a 4 hour4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months coping duration at an EOG target reliability of 0.95 per NUMARC 87-00 Table 3-8 or R.G. 1.155 Table 2.

3. As previously discussed, when North Anna adds the SBO AAC diesel generator, there will be a total of five diesels installed (4 EDGs and 1 SBO OG).

With a total of five diesel generators installed, any one of which can power the LOOP loads associated with any one safety division of either unit, the probability of a station blackout at North Anna approaches that afforded by an EAC Group B design. In fact, if the AAC was qualified and installed as a safety-related machine, North Anna would be an EAC Group B site with a 4-hour coping duration and an EOG target reliability of 0.950 (R.G. 1.155, Table 2, NUMARC 87-00 Table 3-2).

4. The staff presently has the opportunity to consider relaxation of the parameters of Table 2 of R.G. 1.155 per Note a. The costs and efforts which would be required to maintain an EOG reliability program for 0.975 reliability would be greater than those for a 0.95 program. Since separate programs and parameters would be needed for EOGs with 0.975 reliability and the AAC diesel with 0.95, the effort required for two programs would be significant and the benefit would be negligible. The probability that more than three of five diesels with 0.95 reliability would not be able to start and load is not realistic.

B. Proposed AAC Power Source (SSER Section 2.2)

NRC Evaluation:

The staff finds the licensee's proposed addition of a non-safety grade diesel as an AAC power source to be acceptable. However, the licensee should provide confirmation that the proposed AAC power source meets the other criteria of 8

Appendix 8 of NUMARC 87-00, specifically items 8.8, 8.9, 8.10, 8.11, 8.12, and 8.13, and RG 1.155, Position C.3.3.5.5.

The staff does not agree with the S80 duration of 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months . The licensee needs to modify the S80 duration from 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months to 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months (see Section 2.1) and confirm that each day tank will be sized to allow the diesel to run for the S80 duration of 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

The staff finds the use of the existing automatic load sequencing acceptable provided the licensee demonstrates by test that all S80 equipment can be powered from the AAC source within 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months .

Response

The Alternate AC source proposed for North Anna is planned to meet the applicable criteria specified in NUMARC 87-00 Appendix 8. In addition to the design criteria provided in our previous submittals, the following confirms our plans to meet the guidance provided in items 8.8, 8.9, 8.1 O, 8.11, 8.12, and 8.13, and R.G. 1.155 position 3.3.5.5.

8.8 The following planned features of the AAC design should minimize the potential for common cause failure:

1. The AAC power system will be equipped with a DC power source that is electrically independent from the Station's preferred and safety-related power system. Certain breakers required for S80 conditions will utilize DC control power from the existing station 1E batteries. The existing station 1E batteries have been found acceptable in the SSER Section 2.4. There will be a separate DC power system including batteries for the S80 AAC diesel.

2. The AAC power system will be equipped with an air start system that is independent of the preferred safety-related EDG air start system and the blacked-out unit's preferred and safety-related power supply. The source of air for the AAC diesel starting system may also be available to support the station or other functions in the AAC diesel building, but the starting 9

< I components will not be interconnected in a manner which should allow station air problems to render the SBO AAC diesel generator unable to start.

3. The AAC power system will be provided with a fuel oil supply that is separate from the fuel oil supply for the onsite emergency AC power system. A separate day tank will be supplied which is fed from the onsite storage tank. The fuel oil supplied to the AAC day tank will be sampled and analyzed consistent with applicable standards prior to transfer to the day tank. It should be noted that the size of the day tank which would be required for eight hour operation may be larger than acceptable based on insurance and other considerations. This may impact the preliminary design which is being pursued.

It should be noted that though this machine is not safety related, we are trying to install it in a highly reliable configuration. The fuel tank for a four hour coping duration would be about 1200 gallons, which is close to the guidance provided for safety related machines supplied in NUREG 0800, Standard Review Plan, Section 9.5.1, page 47. Should an 8 hour9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months duration be required in order to have a 0.95 EDG reliability, we would be required to install a significantly larger day tank.

This is acceptable for this machine, but is not as desirable as using a

shorter duration and therefore smaller tank, which would be possible with a 4 hour4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months duration and 0.95 reliability.

4. Should the AAC power source be an identical machine to the emergency onsite AC power source, active failures of the emergency AC power source will be evaluated for applicability and corrective action taken to reduce subsequent failures. Due to the difference in rating and date of manufacture, they are not expected to be exactly identical even if the machines are from the same manufacturer.

5. No single point vulnerability is expected to exist whereby a likely weather-related event or single active failure could disable any portion of 10

< I the onsite emergency AC power sources or the preferred power sources, and simultaneously fail the AAC power source.

The AAC Diesel Generator Building design will meet or exceed the requirements of the Virginia Building Code which is based on the Building Officials and Code Administrators (BOCA) Code. This should provide sufficient protection against the effects of likely weather related events but will not provide tornado missile protection or protection against a seismic event. The building will be a separate structure located within the protected area with a floor elevation higher than the probable flood elevation.

The building will be located on the west end of the Unit 2 Turbine

Building in the basin formed by the flood berm, the Turbine Building and the Auxiliary Boiler Building. This location will provide some natural protection against severe weather.

Station interface for AAC diesel support systems are planned to be by buried utilities which should provide adequate protection. Adequate electrical protection.will be provided for the generator portion of the AAC source, its associated equipment and cables. This protection should prevent any single failure from simultaneously affecting any EAC source or preferred power source and the AAC source.

6. The AAC power system will be capable of operating during and after a station blackout without any support systems powered from the preferred power supply, or the blacked-out unit's power sources affected by the event.

The systems required for operation of the AAC source will be powered from a dedicated bus powered by the AAC diesel.

7. Modifications and maintenance activities performed on the AAC source will be conducted in accordance with existing Station procedures. The AAC diesel and support systems will be designated as nonsafety related 11

t l with special regulatory significance (NSQ) and will be included in the post modification/maintenance testing program.

B.9 The AAC source will be sized to carry the required loads associated with one safety division, of either unit, in the event of a loss of offsite power (LOOP). The proposed design will permit the manual alignment of the AAC source to any of the three Station transfer buses that supply power to the safety-related buses at the Station. The required loads are those loads necessary to maintain the plant in a safe shutdown condition following an SBO.

Since the machine involved has not been purchased at this time, its net rating on a 2000 hour0.0231 days 0.556 hours 0.00331 weeks 7.61e-4 months basis can not be stated. We anticipate that the net rating will be approximately 3000 kilowatts, however, it may differ based on the machine purchased.

B.1 O The 'AAC power source will be started and brought to operating conditions approximately once every three months, following manufacturer's recommendations and/or in accordance with plant-developed procedures.

Once during a refueling outage of either unit, a timed start test (within the time period specified for blackout conditions) and a rated load capacity test will be performed.

It should be noted that diesel loading may be simulated other than by powering actual plant loads. It should also be noted that a refueling test will be performed only once per plant refueling cycle and not on a per unit refueling basis.

B.11 Surveillance and maintenance procedures will be developed for the AAC source in accordance with Station administrative procedures. Maintenance procedures will incorporate manufacturer recommendations, however these may be modified based on corporate experience and plant information; 8.12 An initial test program will be developed to demonstrate the load carrying capability** and availability of the AAC diesel generator. This test will demonstrate the availability to power necessary shutdown equipment within one hour following a station blackout. The actual test loads may be different from the shutdown loads powered during the event.

12

\ 1

B.13 The AAC will be included in the existing EDG reliability program as described in section K of this submittal or a similar program. The AAC reliability will be maintained at or above 0.95 as defined by the Virginia Electric and Power Company EOG reliability program which is in general accordance with NSAC-108 and R.G. 1.155 position C.3.3.5.5.

C. Condensate Inventory for Decay Heat Removal (SSER Section 2.3}

NRC Evaluation:

The licensee did not specifically address the SE concern. However, the staff

finds that two channels of instrumentation will be available for the entire SBO duration based on the addition of the proposed AAC source, which will power two battery chargers (one train) within 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months on the blacked-out unit. Hence, the staff considers the condensate inventory issue resolved.

Response

Resolved.

D. Class 1 E Battery Capacity (SSER section 2.4)

NRC Evaluation:

The staff finds this to be acceptable based on the proposed AAC sources and availability within 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months of two battery chargers (one train).

Response

Resolved .

13

E. Compressed Air {SSER section 2.5)

NRC Evaluation:

Based on its review and its understanding that the SBO procedures will specify that an air compressor be powered immediately from the non-blacked out unit or within 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months on the SBO unit, the staff concludes that the licensee will have sufficient compressed air to cope with an SBO event at the North Anna plant.

Therefore, the staff considers this compressed air issue resolved.

Response

Resolved.

F. Effects of Loss of Ventilation {SSER Section 2.6)

NRC Evaluation:

Based on its review and its concerns discussed in the above Sections 2.6.a, 2.6.b, 2.6.c, 2.6.d, the staff has not been able to conclude that the licensee's analyses of the effects of loss of ventilation at the North Anna plant remains unresolved and is considered an open item.

Response

Additional concerns were raised by the staff on the evaluations performed for several of the areas of the plant that were analyzed for the effects of the loss of ventilation event. Clarification for each of the areas is provided below.

1. Control Room Complex and Emergency Switchgear Room Complex

. The staff questioned the basis for the initial.room .temperatures which were assumed in the ventilation analysis on the control and emergency switchgear room (CR/ESGR) complex. In addition, concern was 14

expressed over the absence of a procedural commitment to open control room cabinet doors after the onset of an SBO.

The initial temperatures assumed for the control and emergency switchgear room complex were based on Assumption 2.2.1 of NUMARC 87-00 which states that just prior to the event plant equipment is either normally operating or available from a standby state. Air-conditioning for the CR/ESGR is accomplished by the CR/ESGR air handling and cooling system. Each unit has two trains of air handling equipment service by three air-conditioning chillers (two trains and a spare). Operability of the air-conditioning equipment for the CR/ESGR complex is governed by Technical Specifications which require that two air-conditioning trains be operable (per unit). Therefore, it is reasonable to assume that CR/ESGR

air-conditioning is functioning properly just prior to an SBO event.

Control of the *CR/ESGR area temperature is a function of the setpoint of the chiller chilled water outlet which is held at a constant value. The

chillers load and unload to maintain this constant temperature in response to varying CR/ESGR heat load, thereby maintaining a constant area temperature. Therefore, unless a chiller becomes inoperable, a constant temperature should be maintained.

Based on the above, the analysis concluded that the temperatures resulting from a loss of forced ventilation in the CR/ESGR areas was less than or equal to 100°F in all cases. Therefore, since the final temperature in the CR/ESGR is 20°F less than the Technical Specification limit which is considered the operability limit of the equipment, no operator action to open doors is required.

However, since there are no specific or stated administrative controls or temperature limits (other than the Technical Specification limit of 120°F) for the CR/ESGR complex, an administrative limit of 90°F for Control Room temperature will be added to appropriate procedures when the AAC source becomes operable. This limit should assure that in the event of an SBO the temperature rise in the CR/ESGR complex will be less than the Technical Specification limit of 120°F. In addition, appropriate 15

direction will be added to the response procedures to direct the operators to open cabinet doors within 30 minutes after the onset and identification of an SBO if CR/ESGR cooling has not been restored.

2. Charging Pump Cubicle The staff questioned the methodology used in evaluating the charging pump cubicle. The following is a clarification of the approach used in assessing charging pump cubicle ventilation.

The charging pump motors are self air cooled with integral ventilation fans mounted on each end of the motor shaft. The configuration of the motor ventilation consists of ductwork bolted directly to the motor frame.

Were it not for the resistance offered by the attached ductwork, the motor fans would provide sufficient cooling for the motors.

The ductwork is tied into the central exhaust system and the central

exhaust fans are normally relied upon to assist the motor fans to provide motor cooling. The charging pump cubicle ventilation is also provided by the motor/central exhaust ventilation system, whereby air is drawn into the cubicle through the manway opening and exhausted through the motor. In the event that a motor is running without the central exhaust fans running, some ventilation is provided to the cubicle and motor by the integral motor fans.

A sensitivity study on the effects of reduced ventilation flow rates through the motor was performed and determined that even a minimal amount of air being exhausted by the motor was sufficient to maintain cubicle temperatures at their initial assumed values (120°F). In turn, given the performance characteristics of the integral motor fans (2885 scfm at 1/2 inch H20) and a review of ventilation system test data and ductwork layout, it was estimated that the motor fans would be exhausting

. approximately 1000 scfm until the AAC source energized an emergency bus and approximately 1500 cfm should only one central exhaust fan be energized. The motor manufacturer (Westinghouse) reviewed these conditions and concluded the motor could be operated continuously 16

\ 1

3.

without exceeding its design (winding) temperature rise of 80°C, nor would it affect the motor's qualified life.

Auxiliary Feed Pump House An analysis of the turbine-driven auxiliary feed pump (TDAFW) room was conducted for an 8-hour SBO and the final temperature was calculated to be approximately 129°F. This exceeds the NUMARC limit of 120°F for habitability of personnel. However, since there are no operator actions required to be performed inside of the TDAFW room, this temperature is acceptable.

Station abnormal procedures for providing auxiliary feedwater in the event of a loss of AC power requires the operator to go to the motor-driven AFW pump room to manually realign the TDAFW pump to all three steam generators. The manual valves which are manipulated are in the motor-driven pump cubicle.

From an equipment operability standpoint, this temperature is lower than the NUMARC limit for which operability would be a concern. In addition, per NUMARC Section 7.2.4, SBO is not considered a design basis event, thus assurance of equipment operability need not be provided to the same level of precision and detail required by 10CFRS0.49 for safety-related equipment located in harsh environments.

4. Containment Resolved.

17

1 G. Reactor Coolant Inventory (SSER 2.7)

NRC Evaluation:

The staff finds, based on the availability of AAC power within 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months following the onset of an SBO event, that adequate coping capability exists to maintain reactor coolant inventory for an SBO duration of 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

Response

Resolved, however, we still request a duration of four hours with a target EOG reliability of 0.95.

H. Proposed Modifications (SSER 2.8)

NRC Evaluation:

The staff considers the 5-year time frame to complete the modifications and procedure changes as excessive. The licensee should implement the changes within 3 years, or provide a detailed justification as to why a longer time frame is required. The justification should include a detailed schedule of the different phases of the *project. Also, the licensee should consider the receipt of this SSE as the starting time, since the staff has accepted the proposed AAC source.

Response

Virginia Electric and Power Company had previously requested 5 years following the receipt of favorable notification of the proposed approach to compliance with 10CFR50.63 to complete the necessary modifications and procedural changes. As stated in the previously referenced Supplemental SER, the staff considered the 5-year time frame to be excessive and has directed that Virginia Electric and Power Company implement the changes within 3 years, or provide a detailed justification (including a detailed schedule depicting various phases of the project) as to why 5 years is required. We, 18

therefore, offer the following justification as to the need for 5 years to complete this project.

Attachments:

A. SBO Projects Schedule B. Present Transfer Bus Configuration C. Transfer Bus Configuration - Pre-1994 Unit 1 outage D. Transfer Bus Configuration - Post-1994 Unit 1 outage E. Transfer Bus Configuration - Post-1995 Unit 2 outage F. Transfer Bus Configuration - Pre-1996 Unit 2 outage G. Transfer Bus Configuration - Post-1996 Unit 2 outage Virginia Electric and Power Company proposes to sequence this work into seven main phases (see Attachment A) consisting of the following major activities (some overlapping of phases will occur):

Phase 1 - Prepare procurement specifications for Jan. 92 - Oct. 93: SBO diesel, 4 kV switchgear, MCCs, SBO diesel control panel and other equipment, evaluation of bids, place P.O.s, fabricate and deliver equipment.

19

Phase 2 -

Jan. 92 - April 94:

Perform engineering activities including finalizing of design, preparation of engineering calculations, preparation of engineering drawings, completion of design change packages.

Phase 3 - Pre-1994 Unit 1 outage construction.

Aug. 93 - Aug. 94: This will include construction of SBO Building, installation of SBO diesel, installation of 4160V SBO diesel bus and associated 4160V breakers, installation of D to E tie breakers in normal switchgear room (not including tie-ins to D and E buses), installation of bus work and cable from SBO Building through the plant and into normal switchgear room, performance of associated testing.

Phase 4- Construction during 1994 Unit 1 outage.

0ct. 94 - Dec. 94: This will include final tie-in to D bus, and associated testing.

Phase 5 - Construction during 1995 Unit 2 outage.

April 95 -June 95: This will include final tie-in to E bus, and associated testing.

20

\ I Phase 6 - Pre-1996 Unit 1 outage construction.

May 95 - Nov. 95: This includes installation of F bus tie breaker in normal switchgear room (not including tie-in to F bus), installation of remaining cable and raceway from SBO Building, through the plant and into the normal switchgear room, performance of associated testing.

Phase 7- Construction during 1996 Unit 2 outage.

0ct. 95 -Dec. 96: This includes final tie-in to F bus and associated testing.

NOTE: The *preparation of procedures and training of personnel, even though not shown as specific milestones on the attached schedule, will

.be completed as required to support the various phases of the project and are expected to comprise a significant effort.

Justification for the proposed 5-year completion for this project can, therefore, be summarized as follows:

.1. The procurement and fabrication time, including vendor selection for the major equipment, is extensive. Fabrication and delivery of the SBO diesel after engineering approval of drawings is anticipated to take approximately 12 months.

2. Extensive pre-outage construction is required prior to final station tie-ins being made.

3. The tie-ins to the D, E, and F transfer buses have to be properly sequenced since one offsite source to at least one emergency bus is disabled during any transfer bus outage. Also, tie-ins to the transfer buses require extensive changes to existing breaker logics undervoltage protection and bus relaying schemes. There 21

' I are also extensive changes required to accommodate new 4160V breaker interlocks. This will result in significant changes in and additions to plant procedures which will require significant personnel training.

4. Only one transfer bus should be worked per any given outage due to the significant testing required and to minimize operator confusion with regards to complexity of breaker lineups and testing sequence required for a given condition. This should minimize the potential for adverse impact on minimizing low power/offline risk.

5. If work were performed on more than one transfer bus during an outage, it is expected that this would significantly increase the required length of the outages beyond that presently scheduled .

NRC Information Notice 91-68 indicates the need for careful planning during evolutions similar to those being considered for SBO installation.

6. Since F transfer bus provides power to emergency buses 1H and 2J, it is desirable that this bus be worked during a Unit 2 outage.

This is due to the availability of the normal bus 1B alternate feed to bus 1H. Bus 2J (also powered from transfer bus F) has no alternate feed and thus completion of the F bus tie-ins during a Unit 1 outage would place Unit 2 in an LCO (as one offsite feed would be unavailable). This would probably require shutdown of Unit 2 or approval of a temporary Technical Specification waiver.

7. Partial compliance with SBO can be achieved at the end of the Unit 1 1994 outage and 1995 Unit 2 outage since bus 1J or 2H can be powered, thus assuring that an SBO on either unit can be mitigated by powering of either of these two buses.

22

~-----

' I

8. A recent event at Davis-Besse Unit 1 on October 14, 1991, during implementation of work associated with their SBO diesel underscores the need to proceed prudently on such a complex project. The failure of an auxiliary transformer associated with the SBO diesel generator occurred when it was initially energized from the Station 4160V system causing extensive damage to the transformer, switchgear, and associated bus work. This was part of the work required to support final station tie-in during a refueling outage. This resulted in the loss of off-site power to an emergency bus, and the starting and loading of an EOG. The need to~carefully prepare and properly implement modifications which can have such significant impact on a station can therefore not be overstated.

9. In conjunction with implementation of the North Anna SBO modifications, Virginia Electric and Power Company is also proceeding with simultaneous implementation of SBO modifications at Surry. Compressing the implementation schedule into 3 years would tend to exacerbate an already complex project coordination effort.

J. Quality Assurance (QA) and Technical Specifications (SE)

(SSER 'Section 2.9)

NRC Evaluation:

The licensee needs to address this recommendation.

Response

The nonsafety systems and equipment being relied upon to meet the requirements of the SBO Rule will be included in a QA program which meets the requirements of R.G. 1.155 Section 3.5, and Appendices A and B.

23

The inclusion of the SBO equipment in a QA program which governs their associated design, specification, and testing activities in addition to the development and maintenance of a periodic testing program with trending and root cause evaluation (as discussed below) should be adequate to assure their proper operation; therefore, there is no need to apply Technical Specifications to the SBO equipment.

This position is further reinforced by the fact that SBO is not considered as a design basis event (DBE). Documentation standards for equipment operability are not to be as rigorous as are typically required to meet the design basis requirements of 10CFR50.49, and suitable independence will exist between the SBO equipment and the safety-related systems required to respond to a DBE, such that there is no anticipated potential for common cause failure.

K. EDG Reliability Program (SSER Section 2.1 O)

NRC Evaluation:

The licensee needs to address this recommendation.

Response

-rhe reliable *operation of the North Anna onsite emergency AC power sources has been ensured by the establishment and implementation of the Station EOG Reliability Program. The EOG Reliability Program is designed to monitor and maintain the reliability level of the EOG power sources over time for assurance that the selected reliability levels are being achieved. The Virginia Electric and Power Company EOG Reliability Program is consistent with the guidelines of NUMARC 87-00, Appendix D (EOG Reliability Program), and includes the following elements or activities:

1. Unit EOG reliability target levels are consistent with R.G. 1.155, Table 2.

The selected EOG reliability target for the North Anna Units is 0.950; monitoring of this reliability target is performed whenever EOG start or load-run failures occur, and on a monthly basis. These values are 24

< t compared to the following exceedance trigger values established in the EDG Reliability Program:

- 3 failures in 20 demands

- 5 failures in 50 demands

- 8 failures in 100 demands In addition, if an individual EDG experiences four or more failures in its last twenty five demands, it is deemed a problem EDG. Should this occur, accelerated testing will be performed in accordance with the program.

2. The surveillance testing and reliability monitoring programs are designed

to .. track and monitor EOG performance, and to support preventive and corrective maintenance activities. EDG availability is also monitored and compared to established goals on a monthly basis.

3. The EDG Reliability Program also ensures that target EDG reliability is being achieved, that an appropriate maintenance program is being implemented, and that capability for failure analysis and root cause investigations is provided. Graded corrective actions are implemented if one or more of the exceedance trigger values, as described in 1 above, are met.

4. The EOG Reliability Program implements an information and da,a collection system to service elements of the program, and monitors achieved EDG reliability levels against target values.

5. The EDG Reliability Program identifies responsibility for the major program elements. Management overview for ensuring that reliability levels are being achieved and that the program is functioning properly has also been implemented.

The new SBO AAC diesel will be included either in this program or in a similar program.

25

The resolution of generic issue 8-56, Emergency Diesel Generator Reliability is currently under consideration and review within the NRC and between the NRC and industry. Our current program is designed to assure that proper attention to diesel reliability is maintained and that corrective actions are taken when necessary. We will continue to review this program as required, however, we will not make commitments relative to RG 1.155 at this time.

We will monitor the resolution of 8-56 and respond to it in a reasonable manner.

26

1 991 1992 1993 1994 1995

~ I NRC SER I I I I I I f NEGATIVE M,ANNA 1 N.ANNA 2 W,ANNA 1 N,ANNA 2 N.ANNA 1 1--1 1-f 1--f 1---f I

IWITIAL VP SURRY 2 1--1 SURRY 1 1--1 SURRY 2 1--1 SURRY 1 H

SlAIRT 2 1--f AESPCtlCE N,AIIIA I

SURRY TYPE 2 STUDY NRC SER I

3 YEARS CClf'LETE I~

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PROCURE DIESELS, ETC I

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I I N,ANNA PRE OOT C'ST *r*

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1991 1992 1993 1994 1995 1996 STATION BLACKOUT PROJECTS SCHEDULES ATTACHMENT A

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