ML20244B487
| ML20244B487 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 04/12/1989 |
| From: | Murphy W VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BVY-98-36, NUDOCS 8904190223 | |
| Download: ML20244B487 (9) | |
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, VERMONT YANKEE NUCLEAR POWER CORPORATION l
1 BVY 98-36 RD 5, Box 169, Ferry Road, Brattleboro, VT 05301 ENGINEERING OFFICE i
~
580 MAIN STREET BOLTON, MA 01740 (508)779 4711 April 12, 1989 U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Attention:
Document Control Desk
References:
a)
License No. DPR-28 (Docket No. 50-271) b)
10CFR50.63, " Loss of All Alternating Current Power" c)
Letter, USNRC (Thadani) to NUMARC (Rosin), " Approval of NUMARC Documentation Station Blackout," dated 10/7/88
Dear Sir:
Subject:
Response to Station Blackout Rule 10CFR50.63 The following response is based on the NUMARC generic response format recommended by NUMARC 87-00 and endorsed by the NRC staff in Reference c).
On July 21, 1988, the Nuclear Regulatory Commission (NRC) amended its regu-lations in 10CFR, Part 50.
A new section, 50.63, was added which requires that each light-water-cooled nuclear power plant be able to withstand and recover from a Station Blackout (SBO) of a specified duration.
Utilities are expected to have the base line assumptions, analyses, and related information used in their coping evaluation availtble for NRC review.
It also identifies the fac-tors that must be considered in specifying the SB0 duration. Section 50.63 requires that, for the SB0 duration, the plant can be capable of maintaining core cooling and appropriate containment integrity. Section 50.63 further requires that each licensee submit the following information:
1.
a proposed SB0 duration including a justification for the selection based on the redundancy and reliability of the on-site emergency ac power sour-ces, the expected frequency of Loss of Off-Site Power (LOOP), and the prob-able time needed to restore off-site power; 2.
a description of the procedures that will be implemented for SB0 events for the duration (as determined in Item 1 above) and for recovery therefrom; and 3.
a list and proposed schedule for any needed modifications to equipment and associated procedures necessary for the specified SB0 duration.
9904190223 890412 8[O PDR AUDCK 05000271 p
l VERMONT YANKEE NUCLEAR POWER CORPORATION l 'U.S. Nuclear Regulatory Commission April 12, 1989 Page 2 The NRC issued a revised Regulatory Guide 1.155, " Station Blackout," in August 1988 which describes a means acceptable to the NRC staff for meeting the requirements of 10CFR50.63. Regulatory Guide 1.155. states that the NRC staff has determined that NUMARC 87-00, " Guidelines and Technical Bases for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors," also provides guidance that is in large part identical to the Regulatory Guide 1.155 guidance and is acceptable to the NRC staff for meeting those requirements. Table 1 to Regulatory Guide 1.155 provides a cross reference between Regulatory Guide 1.155 and NUMARC 87-00 and notes where the Regulatory Guide takes precedence. Vermont Yankee Nuclear Power Corporation has evaluated the Vermont Yankee Nuclear Power Station against the requirements of the SB0 rule using the guidance of NUMARC 87-00 and Regulatory Guide 1.155. The results of this i evaluation are detailed belcw (applicable NUMARC 87-00 sections are shown in parentheses). Vermont Yankee will apply Quality Assurance in accordance with our approved 10CFR Appendix B program (YOQAP-1A) to the extent practicable to all modifications necessary to meet the requirements of 10CFR50.63. Accordingly, the QA program will apply to the modifications Vermont Yankee will implement on the Vermont Yankee site, including the tie line up to the Vernon Hydroelectric Station, but not including the Vernon Hydroelectric Station or future tie line maintenance. A. Proposed Station Blackout Duration NUMARC 87-00, Section 3, was used to determine a proposed SB0 duration of eight hours. The following plant factors were identified in determining the proposed SB0 duration: 1. AC power design characteristic group is F3 based on: a. Expected frequency of grid-related LOOP does exceed once per 20 years (Section 3.2.1, Part 1A, Page 3-3). b. Estimated frequency of LOOP due to extremely severe weather pla-ces the plant in ESW Group 4 (Section 3.2.1, Part 18, Page 3-4). c. Estimated frequency of LOOP due to severe weather places the plant in SW Group 3 (Section 3.2.1, Part IC, Page 3-7). d. The Off-Site Power System is in the II/2 Group (Section 3.2.1, Part ID, Page 3-10). 2. The emergency ac power configuration group is C, based on (Section 3.2.2, Part 2C, Page 3-13)- 1 l a. There are two emergency ac power supplies not credited as alter-nate ac power sources (Section 3.2.2, Part 2A, Page 3-15).
VERMONT YANKEE NUCLEAR POWER CORPORATION ~ U.S. Nuclear Regulatory Commission April 12, 1989 Page 3 b One emergency ac power supply is necessary to operate safe shut-down equipment following a loss of off-site power (Section 3.2.2, Part 2B, Page 3-15). 3. The target EDG reliability is 0.95. This was selected based on having a nuclear unit average EDC reliability for the last 100 demands greater than 0.95, consistent with NUMARC 87-00, Section 3.2.4. 4. An alternate ac power source will be utilized at Vermont Yankee Nuclear Power Station which will meet the criteria specified in Appendix B to NUMARC 87-00. Attachment A to this letter provides a description of Vermont Yankee's alternate ac power source, the Vernon Hydroelectric Station. Vermont Yankee's alternate ac power source is available within ten minutes of the onset of the SB0 event and has sufficient capacity and capability to operate systems necessary for the required SB0 duration of eight hours to bring and maintain the plant in safe shutdown. That alternate ac power source will provide the approximate equivalent of one emergency Diesel Generator (OG), and is capable of supplying the entire emergency bus load required under the postulated design basis accident conditions (Vermont Yankee FSAR, Section 8.5.4). The existing calculations and analysis for Class 1E battery capacity, compressed air supply, and containment isolation capabilities for design basis accident conditions envelope Vermont Yankee's SB0 requirements. B. Procedure Description Plant procedures have been reviewed and no modifications are required to meet the intent of the guidelines in NUMARC 87-00, Section 4, which apply to Vermont Yankee, in the following areas: 1. AC power restoration per NUMARC 87-00, Section 4.2.2 (OT-3122, " Loss of Normal Power Procedure"). 2. Severe weather per NUMARC 87-00, Section 4.2.3 (OT-3127, Natural Phenomenaj. The latest revision of the following plant procedures shall be used, as required by plant conditions, to cope with a loss of ac power: 1. OT 3122, " Loss of Normal Power - Procedure" 2. OE 3100, " Scram Procedure" 3. OE 3101, " Reactivity Control Procedure" 4. OE 3102, "RPV Level Control" 5. OE 3103, "Drywell Pressure and Temperature" 6. OE 3104, " Torus Temperature and Level Control Procedure" 7. OE 3105, " Secondary Containment Control Procedure" 8. OT 3127, " Natural Phenomena"
l VERMONT YANKEE NUCLEAR POWER CORPORATION 1 \\ U.S. Nuclear Regulatory Commission April 12, 1989 Page 4 1 In addition, operating procedures for systems available during the event will be used. A list of probable operating procedures would include, but not be limited to, the following: 1 OP 2121, " Reactor Core Isolation Cooling System" 2. OP 2120, "High Pressure Coolant Injection System" 3. OP 2124, " Residual Heat Removal System" 4. OP 2181, " Service hater / Alternate Cooling Operating Procedure" c. Proposed Modifications and Schedule The alternate ac source has the capacity and capability to power the equip-ment necessary to cope with a SB0 in accordance with the NUMARC 87-00, Section 7, for the required coping duration determined in accordance with NUMARC 87-00, Section 3.2.5. Attachment A to this letter provides a description of Vermont Yankee's alternate ac power source and the required modifications. Vermont Yankee has assessed the availability of condensate inventory for decay heat removal, the effects of loss of ventilation on equipment, and the ability to maintain adequate reactor coolant inventory while using the alternate ac source. Our assessment is summarized as follows: 1. Condensate Inventory for Decay Heat Removal (Section 7.2.1) It has been determined from Section 7.2.1 of NUMARC 87-00 that 71,000 gallons of water are required for decay heat removal for eight hours (this includes inventory necessary to depressurize the reactor to 100 psig). The minimum permissible condensate storage tank level per Technical Specifications provides 75,000 gallons of water, which exceeds the required quantity for coping with an eight-hour SBO. i No plant modifications or procedure changes are needed to utilize these water sources. 2. Effects of Loss of Ventilation (Section 7.2.4) The alternate ac power source provides power to the required HVAC systems. No modifications and/or procedures are reauired to provide reasonable assurance for equipment operability.
-VERMONT YANKEE NUCLEAR POWER CORPORATION U.S.' Nuclear. Regulatory Commission ' April 12, 1989 Page 5 3. Reactor Coolant Inventory (Section 2.5)' The alternate ac source powers the necessary make-up systems to main-ltain adequate Reactor Coolant. System inventory to ensure that the core is cooled for the required coping duration. Conclusion [ The centrol circuit' modifications discussed in Attachment A will be implemented no later than 1992 following the preparation of the design change and procure-ment of necessary components.- As discussed in Attachment A to this'1etter, cer-tain modifications to Vermont Yankee's alternate ac power source. tie line are necessary to fully comply with the requirements of 10CFR50.63. Because the Vernon Hydroelectric Station will be undergoing an upgrade during the.next three years, which will also require modifications to the tie line, Vermont Yankee will coordinate the tie line modifications with the hydrostation's upgrade program and schedule. Until the tie line modification is complete,- Vermont Yankee will' maintain the tie line to the hydrostation to ensure its historical reliability continues..These activities include, in part, inspection of the above ground portion.of the line, testing of the line, maintenance of the ~1ine right of way and testing of the associated switchgear'and transformer. We trust that the above information is satisfactory and in accordance with the requirements of 10CFR50.63; however, should you have any questions or desire further information, please do not hesitate to contact us. Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION An- ? Warren P. rphy Vice President and Manager of Operations /dm Attachment l cc: USNRC Regional Administrator, Region I USNRC Resident Inspector, VYNPS i _ _ _ _ _ _ _ _ _ _ _ _._____________________._.______j
(, VERMONT.. YANKEE NUCLEAR POWER CORPORATION lU.S. Nuclear Regulatory Commission -April 12, 1989 .Page'6 STATE OF VERMONT) -)ss WINDHAM COUNTY ) Then personally appeared before me, Warren P. Murphy, who, being duly-sworn, did state that he is Vice President and Manager of Operations of Vermont Yankee Nuclear Power Corporation, that he is duly authorized to execute and file the foregoing document in the name and on the behalf of Vermont Yankee Nuclear Power Corporation and that the statements therein are,true to the best of his knowledge and belief. Cah a k. v Judy /I.)Ha#ris Notary Public A $ My Cordission Expires February 10, 1991 /t NOTARY T PUBLIC i hift 00HT4..p* % 0
f a l .f ATTACHMENT A ) Alterrate AC Power Supply 1 The existing 4;160 V tie line, New England Power ;ompany's Vernon Hydroelectric Station, will be used.as the alternate ac power supply. The hydrostation-has a very good reliability record, with only two unplanned outages (a total of.less than three hours) since 1965. Additionally, in 1986, a Diesel Generator (OG) was installed at the hydrostation which can be used to restart the hydrostation quickly following a loss of-generation. As described in-Section.8.5.5 of.the Vermont Yankee FSAR, the 4,160 V tie from the Vermont Yankee Station to the Vernon Hydroelectric Station is connected through a trans-former to the Vernon Hydroelectric Station 2,400 V Bus System. This Bus System is connected to the station's ten hydroelectric generators and also is con-nected through six transformers to the outside 69 kV switchyard (see attached sketch). -Four 69 kV transmission lines from this switchyard connect the Vernon Hydroelectric Station to the Interconnected Transmission System of New England. Thus, the Vernon Hydroelectric Station 2,400 V Bus System is energized and available whether the Vernon generators are operating or not. The 4,160 V connection from the Vernon Hydroelectric Station to Vermont Yankee consists of a fully insulated cable which runs on a pole line for about 2,300 feet and then runs underground to the Vermont Yankee switchgear for approximately 1,700 feet. The total capacity of the ten Vernon Hydroelectric Station generators is 26,000 kW. The normal operating mode of the Vernon Station requires that 6,000 kW of generation capacity always be connected to the 2,400 V bus, either as spinning reserve or in actual generation. Since the maximum capacity of the transformer which supplies the Vermont Yankee tie is 2,700 kVA, the connection to the Vernon Hydroelectric Station provides approximately the same capacity as ~ one of the emergency DGs, which is more than adequate capacity to cope with the postulated station blackout. The switching arrangement for connection of the Vernon tie line to a Vermont Yankee emergency bus is shown on the attached sketch. Three circuit breakers are used: 3V to connect to Emergency Bus 3; 4V to connect to Emergency Bus 4; and 3V4, which is the feeder breaker for toe Vernon Hydroelectric Station tie line. The control switches for the three breakers are located in the Vermont Yankee Control room and the availability of the Vernon tie line is indi-cated continuously o~y a voltmeter and ammeter adjacent to the control switches. In addition, although it is not required for operation of the tie line, there is a direct telephone circuit between the Main Control Room and the Vernon Hydroelectric Station to allow immediate communications between the two stations. Loau capacity testing of the tie line is performed in accordance with the Vermont Yankee procedure, OP 4142, "Vernon Tie Surveillance." The hydrostation is continuously "on-line," supplying power to the 69 kV Transmission System, and the tie line is continuously energized. Therefore, since the alternate ac source is in effect continuously being load tested, OP 4142 requires load testing of the tie line once every five years.
Attachment A Page 2 The 125 V de control power for Breakers 3V and 3V4 is supplied from Station l Battery A1, and control power for Breaker 4V is supplied from Station Battery l B1. Because of the control power arrangement, a failure of Battery Al could j prevent remote operation of Breakers 3V and 3V4. Th(1 would prevent the Vernon Hydroelectric tie line from being available during the 10-minute time require-ment needed to justify no coping assessment. NOTE: All of the required breakers could still be operated manually to make the alternate source of ac available following a loss of control power, but this could not be accomplished within the ten-minute time frame. A design change will be implemented by 1992 to provide a source of control power to Breaker 3V4 which is independent of Batteries Al and B1. Breakers 3V, 4V and 3V4 are normally open and can only be closed by manual operation, and the breakker control circuits are interlocked to ensure that the Vernon tie line cannot be connected to a live emergency bus. The existing overhead section for the tie line does not fully meet the requirements of an alternate ac source because the line is not protected from potential weather-induced outages. The New England Power Company (NEPCO) is in the final stages of approving a major upgrade of the hydrostation. Final appro-val of the upgrade is expected within the next year, with completion expected within the next three years. The proposed upgrades will raise the operating voltage of the hydrostation from 2.4 kV to 13.8 kV and replace some of the older equipment (e.g., transformers, generetors). Therefore, Vermont Yankee is moni-toring NEPCO's efforts and will cocedinate the tie line modifications necessary to bring it into full compliance with the requirements of 10CFR50.63, with NEPCO's hydrostation upgrade program. i
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