ML031560768
| ML031560768 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 06/06/2003 |
| From: | Chandu Patel NRC/NRR/DLPM/LPD2 |
| To: | Moyer J Carolina Power & Light Co |
| Patel C P, NRR/DLPM, 415-3025 | |
| References | |
| TAC M97957 | |
| Download: ML031560768 (5) | |
Text
June 6, 2003 Mr. J. W. Moyer, Vice President Carolina Power & Light Company H. B. Robinson Steam Electric Plant, Unit No. 2 3581 West Entrance Road Hartsville, South Carolina 29550
SUBJECT:
H. B. ROBINSON STEAM ELECTRIC PLANT UNIT 2 - COMPLETION OF LICENSING ACTIVITY FOR ADEQUACY OF DELAYED OFFSITE POWER CIRCUIT (TAC NO. M97957)
Dear Mr. Moyer:
As a result of lessons learned from the Maine Yankee Independent Safety Assessment, NRC reviewed the offsite power system designs and Technical Specifications (TS) for operating plants licensed prior to 1980. Multi-Plant Action (MPA) B-48, Adequacy of Station Electrical System Voltage, was initiated by the NRC to determine if the onsite distribution system in connection with the offsite power sources had sufficient capacity and capability to start and operate all required safety loads within the equipment voltage rating. This review identified that H. B. Robinson Steam Electric Plant, Unit 2 (HBRSEP2) is a plant that was licensed with only one immediately available offsite power circuit and a delayed offsite circuit that requires the main generator links to be removed before offsite power can be restored to the onsite power distribution system.
The NRC staffs Safety Evaluation dated May 18, 1970, states:
Should a loss-of-coolant accident occur following transformer failure, the engineered safety features would be dependent on the redundant diesel generators for power until disconnect links could be removed from the station generator to permit the backfeeding of offsite power to the auxiliary electrical system through the station main transformer.
This would require about 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to accomplish.
This statement in the original NRC staffs Safety Evaluation confirms that the design of the offsite power system for HBRSEP2 was accepted on the basis that the design of the plant had a backfeed capability in the event of a transformer failure.
HBRSEP2 was constructed prior to the issuance of the current General Design Criterion (GDC) 17, "Electric Power Systems. The licensee-proposed design criterion, identified in Chapter 8 of the original Final Safety Analysis Report (FSAR) as GDC 39, is different than the draft GDC 39 published in the Federal Register on July 11, 1967. The published draft GDC 39, Emergency Power for Engineered Safety Features (Category A), differed from the licensees proposed criterion in that it separated the onsite power system requirements and explicitly stated that redundancy in each power system is required. Therefore, it is not clear in the licensees version of GDC 39 whether the emergency power source refers to onsite, offsite, or both power system requirements.
On July 21, 1988, the NRC amended its regulations in Title 10 of the Code of Federal Regulations (10 CFR) Part 50 by adding a new Section 50.63, Loss of Alternating Current Power. The objective of this rule is to reduce the risk of severe accidents resulting from station blackout (SBO) by maintaining a highly reliable AC power system and, as additional defense in depth, ensuring that plants can maintain adequate reactor core cooling and appropriate containment integrity for required durations. In its initial SBO submittal, the Carolina Power &
Light Company (CP&L, the licensee) took credit for removing the main generator disconnect links and backfeeding power from the 230 kV switchyard to qualify as a 4-hour coping plant.
CP&L revised its coping duration, however, from 4 to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> when the NRC staff questioned the time needed to actually remove the generator links and backfeed the onsite distribution system.
By a letter dated February 14, 1997, the NRC staff requested information regarding the adequacy of the delayed offsite power circuit for HBRSEP2. In its response, CP&L stated that an analysis has not been performed to demonstrate that the offsite power circuit can be made available in sufficient time following a loss of Startup Transformer #2 to prevent fuel design limits and design conditions of the reactor coolant pressure boundary from being exceeded.
CP&L further indicated in its response that it would take significantly longer than the minimum time of the 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> stated in the updated FSAR (UFSAR) to establish offsite power following a loss of Startup Transformer #2.
By a letter dated June 10, 1997, the NRC staff noted that the licensing basis for offsite power was modified from the original licensing requirements by CP&L during the NRC staffs resolution of MPA B-48. The current licensing basis for HBRSEP2 offsite power is one immediately available offsite power circuit (the 115 kV source via Startup Transformer #2) and one delayed offsite power circuit (backfeeding through the main and unit auxiliary transformers). The delayed offsite power circuit must be established in approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> following a loss of Startup Transformer #2 to power safety buses E1 and E2, as required for nuclear safety consideration.
During a meeting with the NRC on July 31, 1997, CP&L described planned enhancements that will improve the capability to cope with a loss of the startup transformer. The enhancements included a modification to install a disconnect switch to isolate the main generator from the main transformer, developing pre-staged clearances, enhancing pre-staged equipment, and additional training of plant staff.
During a meeting with the NRC on August, 17,1998, CP&L described the results of the Refueling Outage 18 demonstration activities, provided activity timelines, and summarized probabilistic safety analysis results. By a letter dated October 15, 1998, CP&L stated that the existing plant configuration need not be changed because of the following:
(1)
CP&L has demonstrated the capability of providing adequate assurance of the ability to establish the backfeed through the unit auxiliary transformer within approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> as stated in the UFSAR; (2)
The Dedicated Shutdown Diesel Generator provides power to equipment necessary for safe shutdown within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> of loss of onsite power and for the duration of the 8-hour SBO coping period; (3)
Proposed modification (addition of generator disconnect switch) to reduce the timelines does not result in appreciable improvements to CDF; and (4)
There is no appreciable increase in risk to the public from the accidental offsite release of radioactive material or potential impact on radiological exposure to the facility workers.
During June 2001, a team of five NRC inspectors from Region II conducted a safety design and performance capability inspection at HBRSEP2. The inspection was conducted in accordance with base inspection Procedure 71111.21, Safety Systems Design and Performance Capability. No findings of significance were identified during the inspection.
By a letter dated April 4, 2003, CP&L informed the NRC staff that it has confirmed through walkdowns and time validation activities that the backfeed alignment can be accomplished within the 4-hour time period identified in the UFSAR. CP&L further stated that the previously completed minor modification to the backfeed procedure and associated timelines, and any potential future changes in this area, have been and will be controlled in accordance with the Emergency Operating Procedures program and the requirements of 10 CFR 50.59. However, Revision 15 of the UFSAR (1998) indicated that a minimum time of 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> is estimated to accomplish backfeeding the plant busses through the unit auxiliary transformer. On May 12, 2003, CP&L revised UFSAR (Rev. 18) to indicate that approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> is estimated to accomplish backfeeding the plant busses through the unit auxiliary transformer. In view of the above revision of the UFSAR, the NRC staff finds that this issue is resolved.
Sincerely,
/RA/
Chandu P. Patel, Project Manager, Section 2 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-261 cc: See next page
ML031560768 OFFICE PM:PDII/S2 LA:PDII/S2 SC:PDII/S2 NAME CPatel EDunnington AHowe DATE 6/3/03 6/3/03 6/5/03
Mr. J. W. Moyer H. B. Robinson Steam Electric Plant, Carolina Power & Light Company Unit No. 2 cc:
Steven R. Carr Associate General Counsel - Legal Department Progress Energy Service Company, LLC Post Office Box 1551 Raleigh, North Carolina 27602-1551 Ms. Margaret A. Force Assistant Attorney General State of North Carolina Post Office Box 629 Raleigh, North Carolina 27602 U. S. Nuclear Regulatory Commission Resident Inspectors Office H. B. Robinson Steam Electric Plant 2112 Old Camden Road Hartsville, South Carolina 29550 Mr. T. P. Cleary Plant General Manager Carolina Power & Light Company H. B. Robinson Steam Electric Plant, Unit No. 2 3581 West Entrance Road Hartsville, South Carolina 29550 Mr. Chris L. Burton Director of Site Operations Carolina Power & Light Company H. B. Robinson Steam Electric Plant, Unit No. 2 3581 West Entrance Road Hartsville, South Carolina 29550 Public Service Commission State of South Carolina Post Office Drawer 11649 Columbia, South Carolina 29211 Mr. B. L. Fletcher III Manager - Support Services - Nuclear Carolina Power & Light Company H. B. Robinson Steam Electric Plant, Unit No. 2 3581 West Entrance Road Hartsville, South Carolina 29550-0790 Mr. C. T. Baucom Supervisor, Licensing/Regulatory Programs Carolina Power & Light Company H. B. Robinson Steam Electric Plant, Unit No. 2 3581 West Entrance Road Hartsville, South Carolina 29550 Ms. Beverly Hall, Section Chief N.C. Department of Environment and Natural Resources Division of Radiation Protection 3825 Barrett Dr.
Raleigh, North Carolina 27609-7721 Mr. Robert P. Gruber Executive Director Public Staff - NCUC 4326 Mail Service Center Raleigh, North Carolina 27699-4326 Mr. Virgil R. Autry, Director South Carolina Department of Health Bureau of Land & Waste Management 2600 Bull Street Columbia, South Carolina 29201 Mr. James W. Holt Manager Performance Evaluation and Regulatory Affairs PEB 7 Progress Energy Post Office Box 1551 Raleigh, North Carolina 27602-1551 Mr. John H. ONeill, Jr.
Shaw, Pittman, Potts, & Trowbridge 2300 N Street NW.
Washington, DC 20037-1128