ML11157A063
| ML11157A063 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 06/09/2011 |
| From: | Leeds E Office of Nuclear Reactor Regulation |
| To: | Apostolakis G, Jaczko G, Magwood W, Ostendorff W, Kristine Svinicki NRC/OCM, NRC/Chairman |
| Stang J, DORL/LPL2-1 415-1345 | |
| References | |
| NOED 11-2-003 | |
| Download: ML11157A063 (7) | |
Text
June 9, 2011 MEMORANDUM TO: Chairman Jaczko Commissioner Svinicki Commissioner Apostolakis Commissioner Magwood Commissioner Ostendorff FROM: Eric J. Leeds, Director /RA by William H. Ruland for/
Office of the Nuclear Reactor Regulation
SUBJECT:
NOTICE OF ENFORCEMENT DISCRETION (SEVERE WEATHER)
GRANTED FOR THE OCONEE NUCLEAR STATION, UNITS 2 AND 3 This memorandum is to inform the Commission that the U.S. Nuclear Regulatory Commission (NRC) granted a notice of enforcement discretion (NOED) as a result of severe weather to Duke Energy Carolinas, LLC, on June 2, 2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML11159A011), for the Oconee Nuclear Station, Units 2 and 3.
The action is based on the licensee's request dated June 2, 2011, for a severe weather NOED.
The staff is providing this information memorandum in accordance with NRC Inspection Manual Part 9900, Technical Guidance, and it requires no Commission action. Enclosed is a summary of the NOED and the actions taken by the NRC staff.
Enclosure:
As stated cc: SECY OGC OCA OPA CFO EDO CONTACT: John F. Stang, NRR/DORL (301) 415-1345
ML11157A063 *concurrence via email OFFICE NRR/LPL2-1/PM NRR/LPL2-1/LA NRR/LPL2-1/BC NRR/DPR/D*
NAME JStang MOBrien GKulesa TMcGinty DATE 06/07/11 06/06/11 06/06/11 06/03/11 OFFICE NRR/DSS/D (A)* NRR/DCI/D(A)* NRR/DE/D* NRR/DRA/D(A)*
SBahadur JLubinski PHiland NAME MCheok (SWeerakkody for) (BThomas for) (GWilson for)
DATE 06/03/11 06/03/11 06/03/11 06/03/11 OFFICE NRR/DORL/D Tech Editor* RII/DRP/D* NRR/D RCroteau ELeeds NAME JGiitter JDougherty (WJones for) (WRuland for)
DATE 06/07/11 06/08/11 06/06/11* 06/09/11 Licensee: Duke Energy Carolinas, LLC Facility: Oconee Nuclear Station, Units 2 and 3 Docket Nos.: 50-270 and 50-287 NOED No. 11-2-003 The U.S. Nuclear Regulatory Commission (NRC) granted a severe weather notice of enforcement discretion (NOED) in response to a request by the licensee (Duke Energy) dated June 2, 2011.
The following list of events describes the basis for the severe weather NOED:
- In January 2011, at Oconee Nuclear Station, Unit 1, valve 1HP-5 (outboard letdown line containment isolation valve) failed to fully close as required when a jumper installed to support testing came loose. The licensee investigated the incident, declared the valve inoperable and placed the unit in cold shutdown to facilitate repairs. The licensee performed an extent-of-condition investigation on similar valves in Units 2 and 3, and concluded that the valves were operable.
- On May 31, 2011, the licensee discovered that the commercially available software it used to model air-operated valve performance was based on information provided by the vendor. The licensee had used the software package to evaluate the margin to close containment isolation valves (2HP-5, 2HP-21, 3HP-5, and 3HP-21) at pressures expected during certain design-basis events. The licensee worked with the vendor to determine the potential impact on the valves ability to perform their intended function (to close and isolate the reactor building during a loss-of-coolant accident or main steamline break). See the drawing below and valves in the blue boxes:
Enclosure
- On June 2, 2011, at approximately 12:10 p.m., the licensee declared containment isolation valves 2HP-5, and 2HP-21, (in Unit 2) and 3HP-5, and 3HP-21 (in Unit 3) inoperable upon confirmation that errors were discovered in approved calculations that resulted in a reduction in the valves closing force margin. Ongoing evaluations indicated that the valves required spring closing forces were inadequate, resulting in a negative closing margin at normal reactor coolant system pressures.
- Once the licensee declared the valves inoperable, Oconee Units 2 and 3 entered into Technical Specification (TS) Limiting Condition for Operation 3.6.3, Containment Isolation Valves, which requires that each containment isolation valve be operable in Modes 1, 2, 3, and 4 or that the affected penetration flow path be isolated within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
If the penetration is not isolated within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, the unit must be placed in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. Unit 1 was not affected, because it is shutdown for a refueling outage.
- At approximately 3:30 p.m. on June 2, 2011, the licensee verbally requested enforcement discretion for an extension of the completion time for TS 3.6.3, Required Action A.1, for Oconee Nuclear Station, Units 2 and 3, of up to 14 days or until the existing grid conditions are improved, either by weather or available reserve capacity, for a period of at least 10 days. This will enable the safe and orderly shutdown of one or both units to make repairs or take other actions to restore compliance with the TS. The total time for this discretion will not exceed 14 days. The licensee based the NOED request, on the extreme vulnerability of the transmission grid resulting from both high electrical demand, caused by current and predicted extreme high temperature (see next page), and the inability to purchase replacement electrical power for Units 2 and 3 because of low power reserves in the southeastern portion of the grid.
- The NRC approved the NOED on June 2, 2011, at approximately 6:30 p.m.
SEVERE WEATHER NOED NRC INSPECTION MANUAL PART 9900 TECHNICAL GUIDANCE For this type of NOED, the NRC must determine that public health and safety and the environment will not be affected unacceptably. This determination is qualitative and must balance the effect of a plant shutdown on public health and safety against the potential radiological or other hazards associated with continued operation, using both risk insights and informed judgments, as appropriate. In unusual situations, severe weather or other natural phenomena may result in the determination by a government or responsible independent entity (such as a regional power authority) that power delivery challenges in combination with potential adverse effects (nonradiological) to public health and safety constitute an emergency situation.
Such situations are rarely expected to occur. When these conditions exist, a severe-weather NOED may be appropriate if enforcing compliance with specific license requirements could worsen the emergency situation. The licensee's request must be sufficiently detailed for the NRC staff to determine that granting the NOED will not affect public health and safety unacceptably. In the case of a severe weather NOED, the NRC requires the licensee to provide the following information, in addition to that required for a normal NOED:
- the name, organization, and telephone number of the official who made the emergency situation determination
- details of the basis and nature of the emergency situation including its effect on the following:
o onsite and offsite emergency plan o plant and site ingress and egress o offsite and onsite power sources o grid stability o actions taken to avert or alleviate the emergency situation
- potential consequences of compliance with existing license requirements
- impact of the emergency situation on plant safety including the capability of the ultimate heat sink
- potential adverse effects on public health and safety from enforcing compliance with specific license requirements during the emergency situation.
The NRC staff independently verifies the status of the electric power grid by calling such monitoring organizations as the Federal Energy Regulatory Commission (FERC); the electric reliability organization, which, in this case, is the North American Electric Reliability Corporation (NERC); the reliability council with Oconee Nuclear Station, which is the SERC Reliability Corporation (SERC); and the associated independent system operator (e.g., the Midwest Independent Transmission System Operator). The calls verify the specific condition of the grid to ensure that, according to the reliability standards, the grid is actually in an emergency condition. When this is the case, corrective actions are taken to ensure that stability is maintained in the grid and associated distribution area. Such actions can include the prohibition of any activity that affects generation capacity, load reductions and load management (up to and including rolling brownouts), and the requirement to purchase available power.
For the specific conditions involving the subject NOED, the NRC staff contacted FERC, NERC, SERC, and the transmission system operator (Duke Energy) to verify the actual grid conditions.
After comparing the associated grid capacity to the demand, all organizations stated that Duke Energys transmission grid was in an emergency condition. The extremely high temperatures in Duke Energys distribution area resulted in significantly higher demand on the transmission grid.
This, added to the lack of overall generating capacity in the southeast region, resulted in an emergency condition according to the grid reliability standards. If the licensee performed the required shutdown of Oconee Unit 2 or 3, it would result in a level 3 emergency condition (potentially resulting in forced rolling brownouts). Power outages for residential customers could jeopardize the health of the public because of the extremely high temperatures in the area.
Transmission topology limits Duke Energys import capability. For the duration of the NOED, Duke Energy will continue to maximize imported power and capacity to restore the grid to a normal operating status. In ensuring the reliability of delivered generation on a regional basis, Duke Energy is aware of the status of generation availability in the regional electric power grid.
Based on the NRCs independent review of the current grid information and expected weather and load conditions, the agency does not expect grid conditions to change significantly over the duration of the NOED.
The NRC staff reviewed the licensees request for enforcement discretion and found that it satisfied the requirements for a severe weather NOED. Therefore, the NRC approved the NOED request on June 2, 2011, at approximately 6:30 p.m.