ML20206D566
| ML20206D566 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/29/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20206D538 | List: |
| References | |
| NUDOCS 9905040152 | |
| Download: ML20206D566 (4) | |
Text
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L UNITED STATES i
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j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20065-0001
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I SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l
RELATED TO AMENDMENT NO. 132 TO FACILITY OPERATING LICENSE NO. DPR-80 l
AND AMENDMENT NO. 130 TO FACILITY OPERATING LICENSE NO. DPR-82 PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON NUCLEAR POWER PLANT. UNITS 1 AND 2 DOCKET NOS. 50-275 AND 50-323
1.0 INTRODUCTION
By letter dated January 14,1998, as supplemented by letters dated May 19,1998, September 28,1998, and three letters dated February 5,1999, Pacific Gas and Electric Company (PGE) submitted a License Amendment Request for the review and approval of a modification to the Diablo Canyon Nuc! ear Power Plant (DCNPP), Units 1 and 2,230 kV offsite power system with the installation of a startup transformer having an automatic load tap changer (LTC), along with the installation of shunt capacitor banks.
The supplemental letters dated September 28,1998, and February 5,1999 (3 letters), provided additional clarifying information, did not expand the scope of the application as originally net!ced, and did not change the staff's original proposed no significant hazards consideration determination published in the Federal Register on October 7,1998 (63 FR 53952).
2.0 EVALdATION The offsite power system for the Diablo Canyon Power Plant consists of one 230 kV immediate and one 500 kV delayed access circuits from the transmissie network. The immedis:te access circuit consists of: (a) two transmission lines (one from Morro Bay Power Plant switchyard and the other from the Mesa Substation)'.o Diablo's 230 kV switchyard, (b) the Diablo 230 kV switchyard, and (c) one transmissior line from Diablo's 230 kV switchyard to each unit's startup transformer and safety busses. Thr, delayed access circuit consists of: (a) three 500 kV transmission lines to Diablo's 500 kV switchyard, (b) a Diablo 500 kV switchyard, and (c) two transmission lines (one for each ursit) from Diablo's 500 kV switchyard through each unit's main transformer to the safety buses. The delayed circuit is made available to safety systems through operation of a motor-ope'ated disconnect switch from the main control room.
On August 8,1995, the licensee determined that the 230 kV system may not have been able to meet its operability requirements for some system loading conditions. Studies conducted at that time indicated that during peak system loading, all 230 kV lines and the Morro Bay Power 9905040152 990429 PDR ADOCK 05000275 P
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. Plant Units 3 and 4 needed to be in service to ensure operability (i.e., minimum 230 kV voltage requirements are met at the Diablo Canyon safety buses following unit trip to a design basis event). This finding was reported to the NRC by License Event Report 1-95-007.
In addition, Califomia is in the process of restructuring its electric industry. Legislation passed by the Califomia legislature and signed into law describes requirements associated with restructuring of the electric industry. This legislation, in part, required the establishment of an independent System Operator (ISO) that will be responsible for directing operation of the i
transmission system and controlling power flow and availability. Various decisions of the Califomia Public Utilities Commission which preceded the enactment of the restructuring legislation also required that the licensee (Pacific Gas and Electric) and Southem Califomia Edison submit plans to voluntarily divest at least half of their fossil-fueled generation facilities to assure that the utilities do not exercise market power in Califomia due to their generation capability. In complying with this requirement, the licensee has agreed to sell the Morro Bay Power Plant. Morro Bay is an approximately 1000 MWe power plant consisting of four natural gas fired units.
To resolve voltage / operability issues on the 230 kV system (reported in Licensee Event Report 1 95-007) and in preparation for electric industry restructuring (primarily the sale of Morro Bay),
the licensee implemented the following changes. The startup transformer for each unit was replaced with a transformer having an automatic load tap changer (LTC); and shunt capacitor banks were installed at the Diablo Canyon 230 KV switchyard and at the Mesa 115 kV Substation. The objective of these changes was (1) to provide DCPP with an adequate immediate access offsite power source from the 230 kV system assuming operation of the transmission network in accordance with Westem System Coordinating Council (WSCC) emergency and normal operating voltage criteria, and (2) to ensure that DCPP is no longer dependent on Morro Bay operation. WSCC emergency and normal operating voltage criteria allows the transmission system to be operated with voltages of +5 percent /-10 percent (241.5 kV to 207 kV) during emergency conditions and +5 percem/-5 percent (241.5 kV to 218.5 kV) during normal conditions.
By letter dated December 12,1997, and in a subsequent meeting on December 22,1997, the licensee submitted information and discussed issues relating to electric industry restructuring and the above described changes. As part of this information exchange, the licensee indicated that they had reviewed the changes in accordance with 10 CFR 50.59, and concluded that the changes do not involve an unreviewed safety question (USQ). NRC approval was, thus, considered not required prior to implementing the changes. The NRC staff disagreed and indicated that some of the changes may involve a USQ and require NRC review and approval prior to their implementation. As a result, the licensee, by letter dated January 14,1998, requested that the NRC review the appropriateness of their USQ determination and, if the NRC determined that the 230 kV changes involve a USQ, the licensee requested that the changes then be reviewed and approved as a license amendment request in accordance with 10 CFR 50.90.
Because the staff concluded that the changes should be deemed a USQ, an evaluation was initiated, as requested by the licensee, for the review and approval of the changes as a license amendment in accordance with 10 CFR 50.90.
3-In response to an NRC request for adddonal information, the licensee, by letter dated May 19, 1998, provided results of stability analysis for the following offsite system configurations:
1.
Normal configuration:
All 230 kV transmission lines in serrice (which could have an impact on operability of offsite power at DCPP) inc!9 ding v>ltage support devicea such as the automatic load tap changer and capacitor banks at DCPP and Mesa.
2.
Off-normal configurations:
a.
Capacitor banks at DCPP and Mesa unavailable, b.
Capacitor banks at DCPP and Mesa unavailable and both Units 1 and 2 aligned to a single startup transformer, c.
Automatic load tap changer unavailable, d.
One of two startup transformer unavailable, e.
Capacitor banks at Mess unavailable, f.
Capacitor banks at Mesa unavailable and both Units 1 and 2 aligned to a single startup transformer, g.
Capacitor banks at DCPP unavailable, l
h.
Capacitor banks at DCPP unavailable and both Units 1 and 2 aligned to a single startup transformer.
1.
Any single 230 kV transmission line between DCPP and Midway or Gates unavailable,
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Both 230 kV transmission lines between Morro Bay and Gates or between Morro Bay and Midway unavailable, k.
One 230 kV bus (or bus section) located in the DCPP or Morro Bay switchyard unavailable, and I.
Startup or shutdown of one unit with the other unit operating.
Normal System Confiaurations For the normal offsite system configuration (defined above), analysis results indicate that the 230 kV system will continue to remain operable in accordance with licensing basis requirements described above following offsite system contingencies or events. These analysis results satisfy staff review procedures / guidelines described in Section 8.2, Part lil.1.(f), of the NRC's Standard Review Plan (NUREG-0800) for meeting the requirements of Criterion 17 of 10 CFR 9
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4 Part 50, Appendix A. The results provide reasonable assurance that o# site power will be operable and thus available to safety system loads.vhen needed following a addent. The failure of equipment (such as the capacitor banks and automatic load tap changers which have been added to the system as either new or replacement equipment) have been included as single contingencies / events in the analysis. The NRC staff thus concludes that the proposed new oNsite system configuration, which utilizes the availability of power from the Gates and Midway cubstations and automatic load tap changers and capacitors to maintain / support voltage, has sufficient reliability to be available when needed, and is considered acceptable.
Off-Normal System Confiourations For the off-normal configurations (defined above) and for various combinations of these j
configurations, analysis results also indicated operability or inoperability with actions (if available) that are needed to reestablish operability for each configuration. Operability was clarified / defined with respect to the DCPP technical specifications. Operability is assumed when analysis demonstrates the availability of the 230 kV system following a design basis accident.
Criterion 17 of 10 CFR Past 50, Appendix A, requires the availability of offsite power to safety i
system loads following a design basis accident. The licensee's clarification / definition for operability meets this requirement. Thus, when the offsite system will be operated with an off-normal configuration, the system's reliability (the availability of the 230 kV system with sufficient capacity and capability when needed following a design basis event) will not be significantly affected. Individual system components have excellent reliability as demonstrated by their 1
operating history. The majority of components perform their design function on a continuous basis and thus their operability (or availability) is also continuously monitored. Loss of availability, monitored by offsite system operators, is immediately reported by procedure to DCPP operators. The newly installed load tap changers and capacitor banks have been conservatively designed and are likewise considered to have excellent reliability. Operability of the load tap changer is monitored from the DCPP control room. Operability of capacitor banks is monitored remotely by offsite system operators and inoperability is immediately reported by procedure to DCPP operators.
The NRC staff concludes that the component parts of the offsite system have the necessary reliability to assure the availability of offsite power when needed following a design basis event.
The proposed offsite system changes meet the requirements of Criterion 17 of 10 CFR Part 50, Appendix A, and are considered acceptable.
Based on the above, the NRC staff concludes that there is reasonable assurance that the proposed new offsite system configuration will have sufficient capacity and capability to supply power when needed to safety system loads and other required equipment following a design basis event, that it, meets Criterion 17 of 10 CFR Part 50, Appendix A, and that it is therefore acceptable.
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3.0 STATE CONSULTATION
in accordance with the Commission's regulations, the California State official was notified of the
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proposed issuance of the amendments. The State official had no commente.
4.0 ENVIRONMENTAL CONSIDERATION
These amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (63 FR 53952). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that (1) there is
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reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors: J. Knox Date: April 29, 1999 l
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