ML103340339

Request for Additional Information, Related to Second Inservice Inspection Interval Relief Requests

ML103340339
Person / Time
Site:	Clinton
Issue date:	12/21/2010
From:	Nicholas Difrancesco Plant Licensing Branch III
To:	Pacilio M Exelon Generation Co
DiFrancesco N, NRR/DORL/LPL3-2, 415-1115
References
TAC ME4185, TAC ME4183, TAC ME4184, TAC ME4186, TAC ME4187, TAC ME4188, TAC ME4189
Download: ML103340339 (4)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 21, 2010 Mr. Michael J. Pacilio President and Chief Nuclear Officer Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

CLINTON POWER STATION, UNIT NO.1 - REQUEST FOR ADDITIONAL INFORMATION RELATED TO SECOND INSERVICE INSPECTION INTERVAL RELIEF REQUESTS (RR) 4216,4217,4218,4219,4220,4221, AND 4222 (TAC NOS. ME4183, ME4184, ME4185, ME4186, ME4187, ME4188, AND ME4189)

Dear Mr. Pacilio:

By letter dated July 1, 2010 (Adams Document Agency Management System (ADAMS)

Accession No. ML101870190), Exelon Generation Company, LLC (the licensee), submitted relief requests from American Society of Mechanical Engineer Boiler and Pressure Vessel Code,Section XI requirements at Clinton Power Station, Unit No.1 for the Second Inservice Inspection Interval.

The Nuclear Regulatory Commission (NRC) staff is reviewing your submittal and has determined that additional information is required to complete the review. The specific information requested is addressed in the enclosure to this letter. During a discussion with Mr. Mitchell Mathews of your staff on December 20, 2010, it was agreed that you would provide a response within 45 days from the date of this letter.

The NRC staff considers that timely responses to requests for additional information help ensure sufficient time is available for staff review and contribute toward the NRC's goal of efficient and effective use of staff resources. If circumstances result in the need to revise the requested response date, please contact me at (301) 415-1115.

Sincerely, Nicholas J. DiFrancesco, Project Manager Plant Licensing Branch 111-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-461

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION EXELON GENERATION COMPANY, LLC CLINTON POWER STATION, UNIT NO.1 SECOND INSERVICE INSPECTION INTERVAL RELIEF REQUESTS (RR) 4216 THROUGH 4222 DOCKET NO.: 50-461 TAC NOS. ME4183, ME4184, ME4185, ME4186, ME4187. ME4188, AND ME4189 Generic Question Pertaining to RR Nos. 4216 through 4222

1. Please confirm that all examinations included in [relief request] RR Nos. 4216 through 4222 have been completed in full. If any have not been completed in full, please note exactly what has been completed.

RR No. 4216 - Surface Examination of Residual Heat Removal Pump "An Casing Weld

2. The illustrations provided in the submittal do not make clear how the instrument line obstructs the required examination. Please include a visual representation that clearly illustrates the obstruction.

3. It was noted that to increase inspection coverage would require staff at Clinton Power Station, Unit No.1 to "cut out the noted instrument line and weld it back." However, it was not made clear if alternate modes of inspection, such as miniaturized cameras, were used to attempt to obtain greater coverage despite the blocking instrument line.

Please discuss the efforts used to maximize inspection coverage without plant modification and why these efforts did, or did not, lead to increased coverage.

RR No. 4217 - Reactor Pressure Vessel (RPV) Head-to-Flange Weld

4. The submittal did not identify how the variation with configuration/geometry of RPV head flange across the length of the weld produced such varied coverage percentages. Can these coverage differences be contributed entirely to the near field effects? Please specify exactly what variations along the weld length reduced the weld coverage for this weld.

5. Please explain why the near field effects are problematic in only one-third of the weld length.

ENCLOSURE

-2 RR No. 4218 - RPV Shell-to-Flange Weld

6. There is no clear identification of how the RPV shell flange configuration/geometry varies through the length of the weld to produce such varied coverage percentages.

Can these coverage differences be contributed entirely to the near field effects? Please specify exactly what variations reduced the weld coverage for this weld.

7. Please explain why the near field effects are problematic in only one-third of the weld length.

RR No. 4219...,. RPV Nozzle-to-Shell Welds

8. No clear identification of how the RPV nozzle-to-shell welds vary to produce the coverage percentages is presented. Please specify what specific variations reduce the weld coverage for each of these welds below 90 percent.

ML103340339 NRR-088 LPL3-2/PM NDiFrancesco 1221110