DCL-10-001, Request for Clarification - Technical Specification Interpretation Regarding 230kV System Operability
| ML100490751 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 02/09/2010 |
| From: | Becker J Pacific Gas & Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| DCL-10-001 | |
| Download: ML100490751 (3) | |
Text
Pacific Gas and Electric Company James R. Becker Diablo Canyon Power Plant February 9, 2010 Site Vice President Mail Code 104/5/601 P. 0. Box 56 Avila Beach, CA 93424 PG&E Letter DCL-10-011 805.545.3462 Internal: 691.3462 U.S. Nuclear Regulatory Commission Fax: 805.545.6445 ATTN: Document Control Desk Washington, DC 20555 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 Request for Clarification - Technical Specification Interpretation Regarding 230kV System Operability
References:
- 1. PG&E Letter DCL-09-010, "Request for Technical Specification Interpretation Regarding 230kV System Operability," dated February 23, 2009.
- 2. Summary of July 22, 2009, Meeting With Pacific Gas and Electric Company on Technical Specification (TS) Interpretation of 230kV Offsite Power System (TAC Nos. ME0711 and ME0712), dated August 18, 2009.
- 3. PG&E Letter DCL-09-066, "Meeting to Discuss Basis for Request for Technical Specification Interpretation Regarding 230kV System Operability," dated September 14, 2009.
- 4. NRC Letter dated December 14, 2009, "Diablo Canyon Power Plant, Unit Nos. 1 and 2 - Request for Technical Specification Interpretation of 230 Kilovolt System Operability (TAC Nos. ME0711 AND ME0712)"
By letter dated February 23, 2009 (Reference 1), Pacific Gas and Electric Company (PG&E) requested NRC concurrence with PG&E's position regarding the basis for operability of the 230kV offsite power system as controlled by TS 3.8.1, "AC Sources
- Operating," and TS 3.8.2, "AC Sources - Shutdown." On July 22, 2009, PG&E met with the NRC to discuss the basis for its request for a technical specification interpretation. A summary of that meeting is provided in Reference 2. By letter dated September 14, 2009 (Reference 3), PG&E provided responses to several questions asked at the meeting.
The NRC provided its evaluation of the PG&E request for interpretation in a letter dated December 14, 2009 (Reference 4). PG&E requests the following clarifications regarding the staffs evaluation.
The NRC evaluation conclusion states, "While the capacity and capability of the 230 kV transmission system are important electrical system parameters and may affect TS operability, they are not specifically identified as TS LCO 3.8.1.a or TS LCO 3.8.2.a operability requirements and, therefore, should not be used to determine compliance with DCPP TS LCO 3.8.1 or TS LCO 3.8.2." The evaluation also confirms that the DCPP TS 3.8.1 and 3.8.2 Bases description of the offsite circuit is consistent with STS 3.8.1 and 3.8.2 Bases which state, in part, that "[a]n A member of the, STARS (Strategic Teaming and Resource Sharing) Alliance
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- Comanche Peak
- Diabto Canyon
- Palo Verde
- San Onofre
- South Texas Project
- WotfCreek
Document Control Desk PG&E Letter DCL-10-011 February 9, 2010 Page 2 offsite circuit consists of all breakers, transformers, switches, interrupting devices, cabling, and controls required to transmit power from the offsite transmission network to the onsite Class 1 E ESF bus(es)." From these statements, it is not clear if this response precludes considering one unit's 230kV system operable if, when supplying that unit's class 1 E buses and the other unit's 1 E buses, load flow and dynamic loading analyses demonstrate sufficient capacity to supply both units from that unit's startup transformer under the most challenging design conditions.
Clarification is requested.
The NRC evaluation states, "Compliance with DCPP TS LCO 3.8.1 also requires the offsite power sources meet GDC 17. This GDC requires the offsite power system
'provide sufficient capacity and capability to assure that (1) specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded as a result of anticipated operational occurrences and (2) the core is cooled and containment integrity and other vital functions are maintained in the event of postulated accidents.' Also, GDC 5 requires that licensees shall not share structures, systems, and components important to safety among nuclear power units, 'unless it can be shown that such sharing will not significantly impair their ability to perform their safety functions....'" The response goes on to describe that the system must have sufficient capacity and capability to (1) operate the engineered safety features (ESF) for a design-basis accident on one unit and concurrent safe shutdown on the remaining unit, and (2) operate the ESFs for dual unit trips as a result of a seismic event or abnormal operational occurrences. The term "concurrent safe shutdown" is not explicitly defined in the response. The response separately states on page 4 of the evaluation without reference to other documents that, "The licensee must ensure that a spurious ESF actuation on the non-accident unit would not result in the loss of the preferred power supply." With this information, is the correct definition of "concurrent safe shutdown" the worst case of an accident on one unit concurrent with a spurious ESF on the other unit, or a dual unit trip?
The NRC evaluation states, "offsite power operability is dependent on the availability of system voltages-above the degraded voltage setpoints, as described in TS 3.3.5,
'Loss of Power Diesel Generator Start Instrumentation.' Meeting these minimum voltage requirements ensures that preferred offsite power sources are available to support safe shutdown of DCPP under postulated conditions." The correct relay setpoint to use would appear to be that for the second level undervoltage protection relay as described in the bases of TS 3.3.5. For the purposes of operability, is it the voltage setpoint alone, or would it include the time delay element of the setpoint?
If you have further questions, or require additional information, please contact Tom Baldwin at (805) 545-4720.
A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Catlaway
- Comanche Peak
- Diablo Canyon
- Palo Verde
- San Onofre 9 South Texas Project
- WolfCreek
Document Control Desk February 9, 2010 Page 3 PG&E Letter DCL-10-0 11 7CQV cc:
Elmo E. Collins, NRC Region IV Michael S. Peck, NRC Senior Resident Inspector Alan B. Wang, NRC Project Manager Diablo Distribution A member of the STARS (Strategic Teaming and Resource Sharing) AlLiance CalLaway
- Comanche Peak e Diablo Canyon
- Palo Verde
- San Onofre
- South Texas Project
- WolfCreek