ML102730428

Electronic Transmission, Draft Request for Additional Information Regarding 30-Day Notification of Changes to an Emergency Core Cooling System Evaluation Resulting in a Peak Cladding Temperature Difference in Excess of 50

ML102730428
Person / Time
Site:	Three Mile Island
Issue date:	09/30/2010
From:	Peter Bamford Plant Licensing Branch 1
To:	Chernoff H Plant Licensing Branch 1
Bamford, Peter J., NRR/DORL 415-2833
References
TAC ME4666
Download: ML102730428 (3)

Text

September 30, 2010 MEMORANDUM TO: Harold K. Chernoff, Chief Plant Licensing Branch I-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation FROM: Peter Bamford, Project Manager /ra/

Plant Licensing Branch I-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

SUBJECT:

THREE MILE ISLAND, UNIT NO. 1 - ELECTRONIC TRANSMISSION, DRAFT REQUEST FOR ADDITIONAL INFORMATION REGARDING 30-DAY NOTIFICATION OF CHANGES TO AN EMERGENCY CORE COOLING SYSTEM EVALUATION RESULTING IN A PEAK CLADDING TEMPERATURE DIFFERENCE IN EXCESS OF 50 DEGREES FAHRENHEIT (TAC NO. ME4666)

The attached draft request for additional information (RAI) was transmitted by electronic transmission on September 30, 2010 to Mr. Thomas Loomis, at Exelon Generation Company, LLC (Exelon, the licensee). This draft RAI was transmitted to facilitate the technical review being conducted by the Nuclear Regulatory Commission (NRC) staff and to support a conference call (if needed) with Exelon in order to clarify the licensees submittal reporting a change or error discovered in an Emergency Core Cooling System evaluation model or in the application of such a model that affects the peak cladding temperature (PCT) calculation at Three Mile Island Nuclear Station, Unit 1 (TMI-1). The draft RAI is related to the licensees submittal dated September 7, 2010. The draft question was sent to ensure that it was understandable, the regulatory basis was clear, and to determine if the information was previously docketed. Additionally, review of the draft RAI would allow Exelon to evaluate and agree upon a schedule to respond to the RAI. This memorandum and the attachment do not represent an NRC staff position.

Docket Nos. 50-289

Enclosure:

As stated

September 30, 2010 MEMORANDUM TO: Harold K. Chernoff, Chief Plant Licensing Branch I-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation FROM: Peter Bamford, Project Manager /ra/

Plant Licensing Branch I-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

SUBJECT:

THREE MILE ISLAND, UNIT NO. 1 - ELECTRONIC TRANSMISSION, DRAFT REQUEST FOR ADDITIONAL INFORMATION REGARDING 30-DAY NOTIFICATION OF CHANGES TO AN EMERGENCY CORE COOLING SYSTEM EVALUATION RESULTING IN A PEAK CLADDING TEMPERATURE DIFFERENCE IN EXCESS OF 50 DEGREES FAHRENHEIT (TAC NO. ME4666)

The attached draft request for additional information (RAI) was transmitted by electronic transmission on September 30, 2010 to Mr. Thomas Loomis, at Exelon Generation Company, LLC (Exelon, the licensee). This draft RAI was transmitted to facilitate the technical review being conducted by the Nuclear Regulatory Commission (NRC) staff and to support a conference call (if needed) with Exelon in order to clarify the licensees submittal reporting a change or error discovered in an Emergency Core Cooling System evaluation model or in the application of such a model that affects the peak cladding temperature (PCT) calculation at Three Mile Island Nuclear Station, Unit 1 (TMI-1). The draft RAI is related to the licensees submittal dated September 7, 2010. The draft question was sent to ensure that it was understandable, the regulatory basis was clear, and to determine if the information was previously docketed. Additionally, review of the draft RAI would allow Exelon to evaluate and agree upon a schedule to respond to the RAI. This memorandum and the attachment do not represent an NRC staff position.

Docket Nos. 50-289

Enclosure:

As stated DISTRIBUTION:

Public RidsNrrPMPBamford LPL1-2 R/F Accession No.: ML102730428

• via email OFFICE LPL1-2/PM SRXB/BC NAME PBamford AUlses*

DATE 09/30/10 09/29/2010 OFFICIAL RECORD COPY

DRAFT REQUEST FOR ADDITIONAL INFORMATION THREE MILE ISLAND UNIT 1 30-DAY NOTIFICATION OF CHANGES TO AN EMERGENCY CORE COOLING SYSTEM EVALUATION RESULTING IN A PEAK CLADDING TEMPERATURE DIFFERENCE IN EXCESS OF 50 DEGREES FAHRENHEIT DOCKET NO. 50-289 By letter dated September 7, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML102500300), Exelon Generation Company, LLC (Exelon, the licensee) submitted a notice reporting a change or error discovered in an Emergency Core Cooling System evaluation model or in the application of such a model that affects the peak cladding temperature (PCT) calculation at Three Mile Island Nuclear Station, Unit 1 (TMI-1).

This report was submitted pursuant to the requirements of Title 10 of the Code of Federal Regulations Section 50.46, which requires, in part, that licensees report a change in the evaluation model used resulting in a significant change in PCT (greater than 50 degrees Fahrenheit (°F)). The intent of this requirement is to enable the U.S. Nuclear Regulatory Commission (NRC) staff to establish the safety significance of this change (See Federal Register Volume 53, No. 180, pp. 35996-36005). Because of the magnitude of the reported change, 225°F, and because the means by which this value was determined is not clear in the submittal, the NRC staff does not have sufficient information to establish the safety significance of this change to the evaluation model and has determined that the following additional information is needed to complete its review.

Please provide additional detailed information regarding Exelons evaluation of the impact of this PCT modeling error. This information should include, but not be limited to, a discussion of the causes of the error and evidence to support a conclusion that the model as a whole remains adequate to predict PCT. Please include a discussion of the impact of this error on the full spectrum of postulated break sizes, as well as Exelons planned corrective actions, and actions to prevent recurrence. If a plant-specific assessment regarding the modeling errors was not performed, please justify the use of any generic evaluation.

Enclosure