ML091880256
| ML091880256 | |
| Person / Time | |
|---|---|
| Issue date: | 09/01/2009 |
| From: | Marilyn Evans NRC/NRR/ADES |
| To: | Marion A Nuclear Energy Institute |
| Architzel R, NRC/NRR/DSSA, 415-2804 | |
| References | |
| Download: ML091880256 (4) | |
Text
September 1, 2009 Alexander Marion, Vice President Nuclear Operations Nuclear Energy Institute 1776 I Street NW, Suite 400 Washington, DC 20006-3708
SUBJECT:
PATH FORWARD TO CLOSURE FOR GENERIC LETTER 2004-02, POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PRESSURIZED-WATER REACTORS
Dear Mr. Marion:
The purpose of this letter is to advise you of the Nuclear Regulatory Commission (NRC) path forward to closure of Generic Letter (GL) 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized-Water Reactors. We communicated this path forward at a public meeting with Nuclear Energy Institute and other stakeholders on June 23, 2009. It focuses on a new process for interacting with licensees that we expect will greatly enhance communication between the NRC staff and licensees, and that should expedite closure of pressurized water reactor (PWR) sump performance issues.
GL 2004-02 requested licensees of PWRs to complete certain corrective actions for emergency core cooling system (ECCS) strainers by December 31, 2007. For a number of reasons, most licensees were not able to meet this objective. However, the NRC understands that most licensees now consider their corrective actions complete. The NRC has granted a few licensees additional time to complete corrective actions necessary to fully address the ECCS sump performance issue.
Over the last 16 months, all PWR licensees have submitted one or more supplemental responses to GL 2004-02 to provide a greater level of detail and to update the information requested in the GL. The NRC provided additional information on expected content of these submittals via the Revised Content Guide for Generic Letter 2004-02 Supplemental Responses (November 2007) (Accession Number ML073110389) and Revised Review Guidance for Licensee Responses to Generic Letter 2004-02 (March 2008) (ML080230234).
In its detailed review of the supplemental responses, the NRC staff has found challenges in reaching issue closure. Because the sump performance issue is highly complex with numerous uncertainties, it is challenging to make a convincing case for compliance with the regulations and for the NRC staff to accept the cases presented to date as the basis for closing GL 2004-02. To complicate matters, the final review guidance was issued after many licensees had already submitted supplemental responses and after they had performed testing and evaluations intended to support closure of GL 2004-02 for their plants. Recognizing the challenges posed by the issues involved, the NRC staff established a process intended to determine whether a given licensee has shown compliance even in the presence of remaining
A. Marion uncertainties. However, to date we have been able to conclude that the submitted information is sufficient to support GL 2004-02 closure (with the exception of invessel downstream effects) for only about 16 of the 69 PWR units. The situation has been further complicated by the emergence of new information throughout the period during which the reviews of licensee supplemental responses have occurred. Consequently, the NRC staff has issued requests for additional information (RAIs) where needed.
The staff has received and reviewed responses to a few of these RAIs, and we have found that licensee responses to the RAIs are in some cases still not providing sufficient information for the staff to conclude that the affected plant has completed corrective actions for GL 2004-02. The primary issues relate to whether or not head loss testing and/or the inputs to the testing are prototypical or conservative compared to the expected sump performance in the plant after a loss-of-coolant accident.
To minimize the need for multiple rounds of RAIs, the NRC staff is implementing a new three-part process for RAI responses. Part one is unchanged. As the staff continues to review licensee supplemental responses and RAI responses in the future, we will develop RAIs as before. We will communicate the draft RAIs to the affected licensee and will provide the opportunity for the licensee to seek clarification of any or all of the RAIs, and to indicate (as applicable) whether the NRC already has sufficient information on the subject area of each RAI.
This is all established practice for NRC licensing reviews.
However, based on review of these RAI responses and the continued discrepancy between the NRC staffs expectations as communicated in the RAIs and some licensees responses to those RAIs, we have concluded that additional interactions are needed to resolve remaining issues.
After each licensee who has received RAIs develops its plans to address them, we will hold a public phone conference or meeting with that licensee. This is part two of the new interaction process. The purpose of this interaction will be to hear the licensees plans for each RAI and to provide feedback on whether the NRC staff believes the licensees path forward will likely be successful, from the NRC staffs perspective, in addressing the RAI. At the conclusion of the phone call, the NRC staff will summarize which RAIs do not appear to be on a path to success, based on the NRC staffs understanding of the licensees plans. Those items not perceived to be on a path to success will be the subjects of a public meeting at which the licensee and the NRC staff will discuss the licensees path forward for each item in detail. This meeting is part three of the interaction process. The NRC project manager will document, in the meeting summary, any remaining areas of disagreement. If the NRC does not have confidence at the conclusion of this meeting that the licensee is on a success path to issue closure with its planned actions, the NRC staff will consider the need for regulatory escalation, which may be plant-specific given the wide variety in sump conditions and licensee approaches to issue resolution.
On related matters, the NRC staff is currently interacting with the Pressurized Water Reactor Owners Group (PWROG) on two issues. The first is invessel downstream effects. The PWROG submitted Revision 1 to topical report WCAP-16793, Evaluation of Long-Term Cooling Considering Particulate, Fibrous and Chemical Debris in the Recirculating Fluid, in April 2009.
The NRC staff has provided a draft request for additional informatio to the PWROG. The staff has also informed the PWROG that it does not believe that the acceptance criteria proposed for determining whether adequate core flow exists are adequately supported by the data provided
A. Marion with the topical report. The NRC staff understands that the PWROG plans to deal with this concern through additional testing and evaluations.
The staff is also interacting with the PWROG on concerns the staff has with certain technical reports cited by some licensees as basis for greatly reducing assumed zones of influence (ZOI) for some types of insulation. Phone discussions have been ongoing for several weeks, but to date limited progress has been made in resolving the issues identified by the staff. The NRC staff understands that the PWROG is considering an additional series of tests to address the staffs concerns. The staff will interact with the PWROG to attempt to ensure that such testing would be found adequate. If we conclude that such testing in not a success path, we will expect licensees to address the issues on a plant-specific basis. As we meet with each licensee using the process described in this letter, we will ask those who credited the ZOI reductions noted in the previous paragraph to describe their contingency plan should the NRC staff not accept the reductions as defensible. A similar question may be asked should the WCAP-16793 generic approach to invessel downstream effects not be fruitful.
If you would like to discuss the contents of this letter further, please contact William H. Ruland at (301) 415-3283.
Sincerely,
/RA/
Michele G. Evans, Acting Associate Director for Engineering and Safety Systems Office of Nuclear Reactor Regulation
A. Marion with the topical report. The NRC staff understands that the PWROG plans to deal with this concern through additional testing and evaluations.
The staff is also interacting with the PWROG on concerns the staff has with certain technical reports cited by some licensees as basis for greatly reducing assumed zones of influence (ZOI) for some types of insulation. Phone discussions have been ongoing for several weeks, but to date limited progress has been made in resolving the issues identified by the staff. The NRC staff understands that the PWROG is considering an additional series of tests to address the staffs concerns. The staff will interact with the PWROG to attempt to ensure that such testing would be found adequate. If we conclude that such testing in not a success path, we will expect licensees to address the issues on a plant-specific basis. As we meet with each licensee using the process described in this letter, we will ask those who credited the ZOI reductions noted in the previous paragraph to describe their contingency plan should the NRC staff not accept the reductions as defensible. A similar question may be asked should the WCAP-16793 generic approach to invessel downstream effects not be fruitful.
If you would like to discuss the contents of this letter further, please contact William H. Ruland at (301) 415-3283.
Sincerely,
/RA/
Michele G. Evans, Acting Associate Director for Engineering and Safety Systems Office of Nuclear Reactor Regulation DISTRIBUTION:
PUBLIC SSIB R/F RidsNrrDss RidsNrrDssSsib RidsNrrDci EWong JGolla PKlein MYoder MSnodderly RidsNrrAdro RidsNrrod RidsNrrAdes ADAMS Accession Number: ML091880256 NRR-106 OFFICE NRR/DSS/SSIB:BC NRR/DCI: D NRR/DORL NRR/DSS: D NRR/ADES NAME MScott MEvans JGiitter WRuland MEvans DATE 07/20/09 07/22/09 07/24/09 08/28/09 09/01/09 OFFICIAL RECORD COPY