ET 11-0003, Correction to 10 CFR 50.55a Request for Alternative to ASME Code Case N-579, Use of Nonstandard Nuts, Class 1, 2, and 3, Mc, CS Components and Supports Construction Section III, Division 1
| ML110740436 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 03/03/2011 |
| From: | Garrett T Wolf Creek |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| ET 11-0003 | |
| Download: ML110740436 (5) | |
Text
W LF CREEK I NUCLEAR OPERATING CORPORATION Terry J. Garrett Vice President Engineering March 3, 2011 ET 11-0003 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
References:
Subject:
Docket 50-482:
Correction to 10 CFR 50.55a Request for Alternative to ASME Code Case N-579, "Use of Nonstandard Nuts, Class 1, 2, and 3, MC, CS Components and Supports Construction Section III, Division 1" Gentlemen:
This letter is requesting approval of a correction to a previously submitted and approved 10 CFR 50.55a Request. Reference 1 requested Nuclear Regulatory Commission (NRC) approval of a 10 CFR 50.55a Request for the Third Ten-Year Interval for Wolf Creek Generating Station's (WCGS's) Inservice Inspection (ISI) Program pursuant to 10 CFR 50.55a(a)(3)(i). Reference 2 provided the NRC's approval of that 10 CFR 50.55a Request.
Since that time Wolf Creek Nuclear Operating Corporation (WCNOC) has become aware of an incorrect reference in the June 2010 10 CFR 50.55a request. The June 2010 request made reference to the incorrect ASME Section III Addendum of the Construction Code for the subject component in Section 2, "Applicable Code Edition and Addenda." The applicable Construction Code and Addenda for the subject component incorrectly referenced ASME Section III, 1974 Edition including Summer 1975 Addendum. The correct reference is the Summer 1974 Addendum. Therefore, the correct Construction Code and Addenda for the component is ASME Section III, 1974 Edition including Summer 1974 Addendum. This incorrect reference was also carried over to the text of the NRC Safety Evaluation (SE) approving the 10 CFR 50.55a Request.
4\\cY-7 P.O. Box 411 / Burlington, KS 66839 / Phone: (620) 364-8831 An Equal Opportunity Employer M/F/HC/VET
ET 11-0003 Page 2 of 2 A comparison of subsections NA and NC of the Summer 1974 and Summer 1975 Addenda to the ASME Code was performed including paragraph NC-2127, which was referenced in the relief request and provides the requirements for the bolting material for ASME Section II1. There were no changes in paragraph NC-2127 between the Summer 1974 and Summer 1975 Addenda. The comparison of the Summer 1974 and Summer 1975 Addenda for all of the other NA and NC paragraphs identified no changes that had an effect on the request. Therefore, the incorrect reference to the Summer 1975 Addendum will not have any impact on the 10 CFR 50.55a Request previously approved by the NRC.
The attachment contains the revised 10 CFR 50.55a Request, which corrects the Construction Code and Addenda listed for the subject component in Section 2 to ASME Section III, 1974 Edition including Summer 1974 Addendum. The remainder of the 10 CFR 50.55a Request is unchanged from the version previously approved by the NRC.
WCNOC requests approval of the attached revised 10 CFR 50.55a Request to support work that will be performed during Refueling Outage 18, which is scheduled to begin on March 19, 2011.
There are no commitments contained within this letter.
If you have any questions, please contact me at (620) 364-4084 or Mr. Gautam Sen at (620) 364-4175.
Sincerely, Terry J. Garrett TJG/rlt Attachment cc:
E. E. Collins (NRC), w/a G. B. Miller (NRC), w/a B. K. Singal (NRC), w/a Senior Resident Inspector (NRC), w/a
Attachment to ET 11-0003 Page 1 of 3 Wolf Creek Nuclear Operating Corporation 10 CFR 50.55a Request (Revised)
Alternative to the requirements of ASME Boiler and Pressure Vessel Code,Section III, Code Case N-579
Attachment to ET 11-0003 Page 2 of 3 10 CFR 50.55a Request (Revised)
Proposed Alternative In Accordance with 10 CFR 50.55a(a)(3)(i)
Alternative Provides Acceptable Level of Quality and Safety
- 1.
ASME Code Components Affected The Excess Letdown Heat Exchanger (EBG02) channel head joint flange-bolting replacement (ASME Class 2).
- 2.
Applicable Code Edition and Addenda
The bolting replacement will be performed as a repair/replacement activity under the jurisdiction of the ASME Boiler and Pressure Vessel Code, Section Xl. The 1998 Edition through the 2000 Addenda is the applicable Section XI edition and addenda for Wolf Creek Nuclear Operating Corporation's (WCNOC's) third inservice inspection interval.
Section Xl IWA-4000 requires use of portions of the original Construction Code and allows use of Construction Code, Code Cases.
For the Excess Letdown Heat Exchanger, the applicable Construction Code is ASME Section III, 1974 Edition including Summer 1974 Addendum.
Code Case N-579, "Use of Nonstandard Nuts, Class 1, 2, and 3, MC, CS Components and Supports Construction Section III, Division 1," is approved for use by the Nuclear Regulatory Commission (NRC) as documented in Regulatory Guide 1.84, "Design, Fabrication, and Materials Code Case Acceptability, ASME Section III," Revision 34, dated October 2007.
- 3.
Applicable Code Requirement
Relief is requested from the ASME Section Xl repair/replacement activity requirements for the replacement bolting in accordance with Code Case N-579.
The specific requirements in Code Case N-579 for which relief is requested are the use of SA-194 material specified in Code Case N-579 for the nonstandard hydraulic nuts and conformance of thread configuration to ASME B1.1.
- 4.
Reason for Request
The excess letdown heat exchanger flange is located in a high radiation area in the reactor coolant loop 4 area inside the secondary shield wall of the reactor building. The excess letdown heat exchanger flange has had chronic boric acid leakage at various times.
Prior efforts to stop the leakage with gasket replacement and bolt torquing adjustments have not been successful and have caused unnecessary radiation exposure to maintenance personnel. The joint is being redesigned to use hydraulic tensioning nuts (HydraNuts) to assure consistent loading around the joint as well as to reduce personnel exposure by reducing maintenance time in the area.
Attachment to ET 11-0003 Page 3 of 3
- 5.
Proposed Alternative and Basis for Use SA-540 Grade B23 material meeting the requirements for bolting material in Section III, paragraph NC-2127(a), will be used to fabricate the hydraulic nuts for the excess letdown heat exchanger flange instead of the SA-1 94 material specified in Code Case N-579.
No torque wrench is required for installation since HydraNuts employ a stud tensioning process that tensions all twelve (12) studs simultaneously.
The hydraulic nuts will incorporate a proprietary outside thread design providing minimized thread deflection to maximize retained load and allow lower preload to be used in contrast to standard threads manufactured in accordance with ASME B1. 1.
ASME SA-540 Grade B23 material, which is an approved Section III material for Class 2 bolting and has sufficient strength for the application, will be used instead of SA-194 for manufacture of the hydraulic nuts.
Code Case N-579 requires the screw threads of nonstandard nuts be manufactured to meet the requirements for threads in ASME B1.1.
While the inside threads of the hydraulic nuts conform to ASME B13.1, the outside threads have a proprietary thread design developed by the vendor, Nova-Technofast, which minimizes thread deflection between the nut and lock ring and thereby minimizes loss of pre-load.
Basis for Use Use of Section III approved SA-540 Grade B23 material in lieu of the SA-194 material specified in Code Case N-579 will assure adequate strength in the joint. The special thread design of the outside threads of the hydraulic nuts minimizes thread deflection and loss of preload. Use of these nonstandard nuts is expected to eliminate leakage from the joint while reducing radiation exposure to maintenance personnel by reducing maintenance time in the area. These advantages provide an equivalent level of quality and safety in accordance with 10CFR50.55a(a)(3)(i).
- 6.
Duration of Proposed Alternative This relief request will be implemented during the Wolf Creek Generating Station (WCGS) refueling outage number 18 and will remain permanently installed in the plant.
This is a new request based on approved Code Case N-579.
- 7.
Precedents A similar request was granted for Diablo Canyon Power Plant (ML040560538). PG&E Letter DCL-04-016, Dated February 12, 2004, to USNRC: Docket Nos. 50-275 and 50-323, Diablo Canyon Units 1 and 2, "Inservice Inspection Relief Request for ASME Code Case N-579," and the associated NRC Safety Evaluation (SE) dated July 29, 2004. The PG&E Relief Request asked for approval to use hydraulic nuts developed by Nova-Technofast for their excess letdown heat exchanger. The NRC SE found the use of SA-540 Grade B23 material acceptable because it is listed as an acceptable material for Class 2 bolting in Section III of the Code. The NRC also found the use of the proprietary outside thread design acceptable because the design minimizes thread deflection between the nut and lock ring and thus the loss of pre-load is minimized.