ML060260021
| ML060260021 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 01/27/2006 |
| From: | Richard Laufer Plant Licensing Branch III-2 |
| To: | Lampert M - No Known Affiliation |
| SHea J, NRR/DLPM,415-1388 | |
| Shared Package | |
| ML060260038 | List: |
| References | |
| G20050841, LTR-05-0588, TAC MC9310 | |
| Download: ML060260021 (4) | |
Text
January 27, 2006 Ms. Mary Lampert 148 Washington Street Duxbury, MA 02332
Dear Ms. Lampert:
Your e-mail dated December 5, 2005, to the Chairman of the Nuclear Regulatory Commission (NRC), has been referred to me for response. In your e-mail, you expressed concerns relating to the proposed Pilgrim Nuclear Power Station (Pilgrim) single loop operation (SLO) amendment currently under review by the NRC staff.
The NRC published a Notice of Consideration of Issuance of Amendment to Facility Operating License, Proposed No Significant Hazards Consideration Determination, and Opportunity for Hearing, in accordance with Title 10 of the Code of Federal Regulations (10 CFR) Section 50.91, on December 21, 2004 (69 FR 76490). The rule allows a 30-day comment period and a 60-day period to file for a hearing. The amendment application is currently proceeding through the NRC amendment review process.
Although this amendment is in the NRC review process, I would like to address your concerns related to SLO for Pilgrim, in particular, and boiling-water reactors (BWRs) in general.
Power generation with a single recirculation loop in service is a recognized mode of operation for BWRs. Reactor control and operation in single-loop is very similar to that in two-loop operation (TLO). The primary difference is that as drive flow on the operating pump is increased, part of the total flow from the active jet pump loop will backflow through the inactive jet pumps. This effect reduces the net achievable core flow and limits the reactor power level that can be achieved. This also affects the normal relationship between drive flow and core flow as compared to TLO. At low core flow, SLO may be slightly less stable than TLO, but as core flow increases and reverse flow is established, the stability performance of TLO and SLO is similar. A conservative approximation is used to determine back flow through the inactive jet pumps, which provides a conservative determination of actual core flow during SLO.
Prior to 1986, the NRC staff had disallowed this mode of operation for most BWRs because of jet pump vibration problems, and thermal-hydraulic stability concerns at certain high thermal power and low core flow operating conditions. Accordingly, in general, BWR technical specifications (TSs) initially required a plant shutdown within several hours if one of the reactor coolant loops became inoperable. Subsequently, the NRC staff issued Generic Letter (GL) 86-09, Technical Resolution of Generic Issue No. B-59-(N-1) Loop Operation in BWRs and PWRs [presurized water reactors], dated March 31, 1986, to inform licensees that SLO would be acceptable provided operating limitations are imposed for the detection and suppression of thermal-hydraulic instabilities.
Additional operational restrictions based on NRC-approved methods are imposed during SLO to assure compliance with NRC regulations contained in Appendix A, General Design Criteria
[GDC] for Nuclear Power Plants, to Part 50 of 10 CFR. Criterion 10 of the GDC, Reactor Designs, requires that the reactor core and associated coolant, control, and protective systems
M. Lampert be designed with appropriate margins to assure that limits to protect against fuel damage are not exceeded during normal operation and anticipated operational occurrences.
The most recent unplanned recirculation system TS required shutdown at Pilgrim occurred in February 2002 due to a recirculation pump motor generator set field wiring failure. Although these components are accessible outside containment, the repair could not be diagnosed, planned, and implemented within the LCO time frame currently allowed. However, under the proposed TS amendment, the licensee could have performed repairs under SLO and prevented the need to perform the potentially higher risk activity of a plant shutdown.
In your e-mail, you referred to the Hope Creek Generating Station (Hope Creek), which is licensed for SLO and includes the associated operational restrictions required by NRC regulations. Hope Creek, or any other BWR licensed for SLO (including Pilgrim, if SLO is approved), would be required to shut down if safety limits and applicable operational restrictions cannot be maintained in accordance with TSs while in SLO.
In your e-mail, you also expressed concerns related to the core flow distribution during SLO for BWRs. As discussed previously, reactor control and operation are very similar for SLO and TLO in BWRs. Flow distribution in the reactor would be the same whether operating in SLO or TLO for the same reactor core flow. Fuel orifice flow restrictions provide a fairly even distribution of flow in the reactor under all forced recirculation flow conditions. Since a conservative estimation of reverse flow is determined under SLO conditions and since conservative NRC-approved methods are used to determine operational restrictions for SLO, there is reasonable assurance that fuel safety limits will not be exceeded during normal operation and anticipated operational occurrences while in SLO.
We share your concerns for the safety of your community and others who live and work in or near Pilgrim. The NRC staff will thoroughly review the proposed Pilgrim SLO amendment and it will not be approved unless the NRC staff can conclude that there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner.
Thank you for bringing your concerns to the attention of the NRC.
Sincerely,
/RA/
Richard J. Laufer, Chief Plant Licensing Branch I-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
M. Lampert be designed with appropriate margins to assure that limits to protect against fuel damage are not exceeded during normal operation and anticipated operational occurrences.
The most recent unplanned recirculation system TS required shutdown at Pilgrim occurred in February 2002 due to a recirculation pump motor generator set field wiring failure. Although these components are accessible outside containment, the repair could not be diagnosed, planned, and implemented within the LCO time frame currently allowed. However, under the proposed TS amendment, the licensee could have performed repairs under SLO and prevented the need to perform the potentially higher risk activity of a plant shutdown.
In your e-mail, you referred to the Hope Creek Generating Station (Hope Creek), which is licensed for SLO and includes the associated operational restrictions required by NRC regulations. Hope Creek, or any other BWR licensed for SLO (including Pilgrim, if SLO is approved), would be required to shut down if safety limits and applicable operational restrictions cannot be maintained in accordance with TSs while in SLO.
In your e-mail, you also expressed concerns related to the core flow distribution during SLO for BWRs. As discussed previously, reactor control and operation are very similar for SLO and TLO in BWRs. Flow distribution in the reactor would be the same whether operating in SLO or TLO for the same reactor core flow. Fuel orifice flow restrictions provide a fairly even distribution of flow in the reactor under all forced recirculation flow conditions. Since a conservative estimation of reverse flow is determined under SLO conditions and since conservative NRC-approved methods are used to determine operational restrictions for SLO, there is reasonable assurance that fuel safety limits will not be exceeded during normal operation and anticipated operational occurrences while in SLO.
We share your concerns for the safety of your community and others who live and work in or near Pilgrim. The NRC staff will thoroughly review the proposed Pilgrim SLO amendment and it will not be approved unless the NRC staff can conclude that there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner.
Thank you for bringing your concerns to the attention of the NRC.
Sincerely,
/RA/
Richard J. Laufer, Chief Plant Licensing Branch I-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation DISTRIBUTION: G20050841/LTR-05-0588 PUBLIC RidsNrrDorlLpLa RidsWpcMail RidsEdoMail Center RidsNrrDorl RidsAcrsAcnwMailCenter RidsNrrOd RidsNrrPMJShea GCranston RidsNrrAdro RidsNrrLASLittle TFord RidsOgcRp RidsRgn1MailCenter LCox RidsOpaMail RidsOcaMailCenter KJohnson Incoming: ML053480126 Accession No.: ML060260021 PKG.: ML060260038 OFFICE LPL1-1/PM LPL1-1/LA SBWB/BC LPL1-1/BC NAME JShea SLittle GCranston RLaufer DATE 1/26/06 1/26/06 1/26/06 1/27/06 OFFICIAL RECORD COPY