ML12348A055

Response to RAI Regarding 10 CFR 50.46 Notification of Change in Peak Cladding Temperature for Large Break Loss of Coolant Accident Analysis

ML12348A055
Person / Time
Site:	Oconee
Issue date:	12/07/2012
From:	Geoffrey Miller Duke Energy Carolinas
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
Download: ML12348A055 (6)

Text

Duke 10 CFR 50.46 GARRYD. MILLER Energy Sr Vice President Nuclear Engineering Duke Energy ECO7H/526 South Church Street Charlotte,NC 28201-1006 MailingAddress:

P.O. Box 1006- ECO7H December 7, 2012 Charlotte,NC 28201-1006 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

Subject:

Duke Energy Carolinas, LLC (Duke Energy)

Oconee Nuclear Station, Units 1, 2, and 3 Docket Numbers 50-269, 50-270, and 50-287 Response to NRC RAI regarding 10 CFR 50.46 Notification of Change in Peak Cladding Temperature for Large Break Loss of Coolant Accident Analysis

Reference:

1) Letter, D. C. Culp (Duke Energy) to USNRC,

Subject:

Oconee Nuclear Station Day Report Pursuant to 10 CFR 50.46, Changes to or Errors in an Evaluation Model, March 9, 2012. [ADAMS Accession No. ML12073A354]

2) Email correspondence, John Boska (NRC) to Kent R. Alter (Duke Energy),

Subject:

Oconee Units 1, 2, and 3, NRC Request for Additional Information on Errors Reported per 10 CFR 50.46, ME9119, October 26, 2012. [ADAMS Accession No. ML12300A201]

3) Letter, Pedro Salas, Director, Regulatory Affairs (AREVA NP Inc.) to USNRC,

Subject:

"Generic RAI Response to a 30-day 10 CFR 50.46 Report of Significant PCT Change", (NRC:12:062), December 6, 2012.

On March 9, 2012, (Reference 1) Duke Energy submitted a 30-day report pursuant to 10 CFR 50.46(a)(3)(ii) regarding the impact on Peak Cladding Temperature (PCT) from two errors in the Emergency Core Cooling System (ECCS) evaluation model used to assess a postulated Large Break Loss of Coolant Accident (LBLOCA) for Oconee Nuclear Station. This information is specific to the application of the AREVA ECCS evaluation model for B&W plants, as applied to Oconee Nuclear Station.

The NRC transmitted, via email, (Reference 2) Requests for Additional Information (RAIs) regarding the Reference 1 letter, dated March 9, 2012 [ADAMS Accession No. ML12073A354] concerning the 30-day report pursuant to 10 CFR 50.46(a)(3)(ii). The purpose of this letter is to provide a response to the RAIs.

U.S. Nuclear Regulatory Commission December 7, 2012 Page 2 In response to the first RAI question, AREVA has submitted a generic response to the NRC in Reference 3. Duke Energy Carolinas has provided a response to the second RAI question, as provided in the enclosure to this letter.

There are no regulatory commitments contained in this letter.

Please address any comments or questions regarding this matter to Paul Guill at (704) 382-4753 (pauLguill@duke-energy.com).

Sincerely, Garry . Miller Senior Vice President Nuclear Engineering

Enclosure:

Response to NRC RAI regarding 10 CFR 50.46 Notification of Change in Peak Cladding Temperature for Large Break Loss of Coolant Accident Analysis

U.S. Nuclear Regulatory Commission December 7, 2012 Page 3 xc (with attachment):

V. M. McCree, Region II Administrator U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Avenue NE, Suite 1200 Atlanta, GA 30303-1257 J. P. Boska, Senior Project Manager (ONS)

U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop 0-8 C2 Rockville, MD 20852-2738 NRC Senior Resident Inspector Oconee Nuclear Station

DUKE ENERGY CAROLINAS, LLC OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 ENCLOSURE RESPONSE TO NRC RAI REGARDING 10 CFR 50.46 NOTIFICATION OF CHANGE IN PEAK CLADDING TEMPERATURE FOR LARGE BREAK LOSS OF COOLANT ACCIDENT ANALYSIS 2 total pages to follow

Response to NRC Requests for Additional Information (Question 1)

NRC RAI Question 1 There are two changes to peak cladding temperature (PCT) for Large Break Loss of Coolant Accident (LBLOCA) analysis discussed in the report submitted by the licensee. The first change is an Evaluation Model (EM) application error in the determination of the end of Emergency Core Cooling System (ECCS) bypass which resulted in an 80*F decrease in PCT. The second change is an EM modeling change to include the effects of the upper plenum column weldments which resulted in an 80°F increase in PCT.

Provide the analysis that lead to each change having an 80 degree change in PCT.

Duke Energy Carolinas Response to NRC RAI Question 1 In response to the first RAI question, AREVA has submitted a generic response to the NRC.

Please see AREVA Letter from Pedro Salas, Director, Regulatory Affairs to NRC dated December 6, 2012, which transmits AREVA Document ANP-3180 (NP), Revision 0, "177 Fuel-Assembly Plant RAI Response to a 30-Day 50.46 Report of Significant PCT Change",

December 2012. The AREVA report has been reviewed by Duke Energy and is provided in response to RAI Question 1 for Oconee Nuclear Station.

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Response to NRC Requests for Additional Information (Question 2)

NRC RAI Question 2 10 CFR 50.46(a)(3)(ii) states: " ... If the change or error is significant, the applicant or licensee shall provide this report within 30 days and include with the report a proposed schedule for providing a reanalysis or taking other action as may be needed to show compliance with 50.46 requirements... "

The PCT for LBLOCA for Oconee Units 1, 2, and 3 has changed by an absolute value of 160°F since the analysis was performed. Simply reporting the changes and errors in the methodology does not satisfy the intent of the regulation. Justify not providing a schedule for reanalysis or taking other action to show compliance with Section 50.46.

Duke Energy Carolinas Response to NRC RAI Question 2 The response to RAI Question 1 provides additional detail regarding the analytical bases for the two peak cladding temperature (PCT) error estimates, which were based upon explicit RELAP5/Mod2-B&W code runs for the nuclear steam supply systems (NSSS) designed by Babcock & Wilcox (B&W). One error that was corrected in the evaluation models was specific to the determination of the end of emergency core cooling system (ECCS) bypass time. A separate error correction to the ECCS evaluation model was made based on the effects of the upper plenum column weldments.

As evidenced by the information provided in the response to RAI Question 1, both of these error corrections have been analyzed in detail. Furthermore, the error corrections in the ECCS evaluation model do not result in any challenge to the 10 CFR 50.46(b) acceptance criteria. As the individual error corrections have been identified for the applicable evaluation model, and there are no other known changes identified at this time, the overall evaluation model is considered bounding and complete.

The corrected ECCS evaluation model, as discussed in AREVA Report ANP-3180 (NP), will be used for any future analyses.

In summary, the response to RAI Question 1 establishes the following:

" The error-adjusted LBLOCA PCTs for Oconee Nuclear Station Units 1, 2, and 3 remain considerably below the 10 CFR 50.46(b) acceptance criteria.

" The SBLOCA analyses are not affected by the ECCS evaluation model errors.

• The response provides additional information regarding the nature of the PCT error evaluations, which are supported by explicit analyses using the B&W plant ECCS evaluation model.

" The analysis, with the identified corrections, is considered adequate to demonstrate compliance with the requirements of 10 CFR 50.46.

Based on the above, there are no adverse impacts to safety. Therefore, further LBLOCA reanalysis for Oconee Nuclear Station Units 1, 2, and 3 is not warranted.

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