ML062220594
| ML062220594 | |
| Person / Time | |
|---|---|
| Issue date: | 08/09/2006 |
| From: | Grobe J NRC/NRR/ADES/DCI |
| To: | Jeffrey Riley Nuclear Energy Institute |
| References | |
| EA-03-009, N-729-1 | |
| Download: ML062220594 (6) | |
Text
August 9, 2006 Mr. James H. Riley Nuclear Energy Institute 1776 I Street, NW, Suite 400 Washington, D.C. 20006-3708
SUBJECT:
NRC Staff Position on Use of ASME Code Case N-729-1 in Lieu of First Revised NRC Order EA-03-009
Dear Mr. Riley:
On February 11, 2003, the Nuclear Regulatory Commission (NRC) issued Order EA-03-009, Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors. This order modified licensees licenses to require specific inspections of the reactor pressure vessel (RPV) upper head and associated penetration nozzles at pressurized water reactors. In response to internal review and stakeholder input, the NRC issued First Revised Order EA-03-009 (Order), on February 20, 2004, which refined the inspection requirements of NRC Order EA-03-009 by taking into account lessons learned from inspections performed from February 2003 to January 2004. The requirements of the Order currently remain in effect.
In February 2006, American Society of Mechanical Engineers (ASME),Section XI, Code Case N-729-1, Alternative Examination Requirements for Pressurized-Water Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds, was approved by the ASME for use as an alternative to current ASME Code inspection requirements for RPV upper head penetrations.
The NRC staff has reviewed the ASME-approved version of Code Case N-729-1 and finds it to be acceptable for use, subject to certain limitations and conditions. These limitations and conditions are enclosed, and involve aspects of inspection requirements which the NRC has expressed in past ASME Code Section XI Subcommittee and Task Group meetings and in a letter from the NRC to Mr. Gary C. Park, dated April 26, 2005 [ADAMS Accession Number ML051110358]. The NRC staff concludes that implementation of ASME Code Case N-729-1, subject to the enclosed limitations and conditions, in lieu of the requirements of the Order, provides an acceptable level of quality and safety.
The NRC expects that the requirements of Code Case N-729-1 will eventually be reflected in a future edition of the ASME Code. We also anticipate that the acceptability of the Code Case will be reflected in a future revision of Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1. However, to expedite its implementation, the NRC staff is pursuing a rulemaking to incorporate by reference, the inspection requirements of Code Case N-729-1, with the stated limitations and conditions, into Title 10 Code of Federal Regulation Part 50.55a. In the interim until these activities are complete, the staff recognizes that some licensees may wish to implement Code Case N-729-1, as conditioned, in lieu of the requirements of the Order. The NRC staff advises that licensees which choose this option, submit to the NRC a relaxation request from the requirements of the Order in accordance with
J. Riley Paragraph IV.F of the Order. As part of their supporting discussion, licensees should verify the applicability of the technical basis upon which any previously approved Order relaxations were based when requesting the use of Code Case N-729-1 since certain requirements in Code Case N-729-1 are less restrictive than those in the Order, and identify those conditions or issues which may impact conformance with the Code Case. For example, flaw evaluations performed to justify the acceptability of not inspecting an uninspectible zone within the reinspection frequency of the Order must also show that the results remain valid for the longer reinspection interval permitted by N-729-1. Furthermore, for those provisions of the Code Case (including NRC conditions) that cannot be met, technical justification supporting the acceptability of the deviations needs to be included as part of the Order relaxation request.
NRC approval of a licensees request to implement code case N-729-1 will supersede all previously authorized relaxation requests for subsequent inspections effective the date of issuance of the safety evaluation.
Should you have any questions on this matter, please contact Mr. Terence Chan at (301) 415-2768 or TLC@nrc.gov.
Sincerely,
/RA/
John A. Grobe, Director Division of Component Integrity Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission
Enclosure:
NRC Staff Position on ASME Code Case N-729-1 cc: See next page
ML062220594 OFFICE DCI/CPNB DCI/CPNB DD/DCI D/DCI NAME JCollins TChan WBateman JGrobe DATE 07/21/2006 07/21/2006 07/28/2006 08/09/2006 cc:
Mr. Gary C. Park, Chairman ASME Subcommittee on Nuclear Inservice Inspection Monticello Nuclear Generating Facility 2807 W. County Rd 75 Monticello, MN 55362-9601 Mr. Robin L. Dyle Southern Nuclear Co.
42 Inverness Center Pkwy Birmingham, AL 35242 Ms. Viki Armentrout Dominion Energy 5000 Dominion Blvd. - 3SE Glen Allen, VA 23060 Mr. Richard W. Swayne Reedy Engineering 3425 S. Bascom Ave., Suite E Campbell, CA 95008-7300
NRC Staff Position on ASME Code Case N-729-1, Alternative Examination Requirements for Pressurized-Water Reactor Closure Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds In February 2006, the American Society of Mechanical Engineers (ASME) approved Section XI Code Case N-729-1, Alternative Examination Requirements for Pressurized-Water Reactor (PWR) Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds, as an alternative to current ASME Code inspection requirements for the reactor pressure vessel (RPV) upper head and associated penetration nozzles. The Nuclear Regulatory Commission (NRC) staff has reviewed the ASME-approved version of Code Case N-729-1 and finds it provides an acceptable level of quality and safety for use in lieu of the First Revised NRC Order EA-03-009 (Order), subject to certain limitations and conditions.
The Code Case N-729-1 inspection plan for RPV upper heads with Alloy 600/182/82 penetration nozzles and welds requires periodic bare metal visual (BMV) examinations and periodic nonvisual examinations using ultrasonic testing, eddy current testing, or dye penetrant testing of the penetration nozzle base metal. BMV examinations are performed in order to provide indication of any primary coolant leakage based on the presence of boric acid deposit accumulations. Nonvisual examinations are performed in order to identify flaws which could lead to leakage or failure of the penetration nozzle.
Such inspections are also required to be performed for RPV upper heads with Alloy 690/152/52 penetration nozzles and welds, but the frequency of inspection is reduced. This reduction is due to the enhanced resistance of these materials against primary water stress corrosion cracking (PWSCC).
The NRC staff concludes that ASME Section XI Code Case N-729-1 provides an acceptable level of quality and safety as a long-term inspection plan in lieu of the requirements of the Order, subject to the following limitations and conditions.
- 1. Item B4.40 of Code Case N-729-1, Table 1, shall be inspected at least every fourth refueling outage or at least every seven calender years, whichever occurs first, after the first ten-year inspection interval.
- 2. If flaws attributed to PWSCC have been detected, whether acceptable or not for continued service under Paragraphs -3130 or -3140, the reinspection interval shall be each outage instead of the reinspection intervals required by Table 1, Note (8).
- 3. Instead of the specified examination method requirements for volumetric and surface examinations of Note 6 in Table 1, the licensee shall perform volumetric and/or surface examination of essentially 100% of the required volume or equivalent surfaces of the nozzle tube, as identified by Fig. 2 of ASME Code Case N-729-1. A surface examination shall be performed on all J-groove welds. If a surface examination is being substituted for a volumetric examination on a portion of a penetration nozzle that is below the toe of the J-groove weld [Point E on Fig. 2 of ASME Code Case N-729-1], the surface examination shall be of the inside and outside wetted surface of the penetration nozzle not examined volumetrically.
- 4. Appendix A of ASME Code Case N-729-1 shall not be implemented without prior NRC approval.
- 5. After December 31, 2007, ultrasonic examinations shall be performed using personnel, procedures and equipment that have been qualified by blind demonstration on representative mockups using a methodology that meets the conditions specified in 5.a through 5.d instead of the qualification requirements of Paragraph -2500 of ASME Code Case N-729-1.
- a. The specimen set shall have pipe diameters within 1/2 in. (13 mm) of the nominal diameter of the qualification pipe size and a thickness tolerance of +/- 25% of the nominal through-wall depth of the qualification pipe thickness. The specimen set shall include geometric and material conditions that normally require discrimination from primary water stress corrosion cracking (PWSCC) flaws.
- b. The specimen set shall have a minimum of ten (10) flaws which provide an acoustic response similar to PWSCC indications. All flaws shall be greater than 10% of the nominal pipe wall thickness. A minimum number of 30% of the total flaws shall be outside diameter initiated and 30% of the total flaws shall be inside diameter initiated. Further, at least 30% of the total flaws are at each of the depth ranges of 10%-30% and 31%-50% from the inside or outside diameter, as applicable. At least 30% and no more than 60% of the flaws shall be oriented axially.
- c. Procedures shall identify the equipment and essential variable settings used for the qualification. An essential variable is any variable that has an effect on the results of the examination. The procedure shall be requalified when an essential variable is changed outside the demonstration range. Procedure qualification shall include the equivalent of at least three personnel performance demonstration test sets. Procedure qualification requires at least one successful personnel performance demonstration.
- d. Personnel performance demonstration test acceptance criteria will meet the personnel performance demonstration detection test acceptance criteria of Table VIII-S10-1 of Section XI, Appendix VIII, Supplement 10. Examination procedures, equipment, and personnel are qualified for depth sizing and length sizing when the RMS error of the flaw depth measurements, as compared to the true flaw depths, do not exceed 1/32-inch (0.8 mm) and the RMS error of the flaw length measurements, as compared to the true flaw lengths, do not exceed 1/16-inch (1.6 mm), respectfully.