ML060950645

GALL AMP: XI.M37, Flux Thimble Tube Inspection (Audit Worksheet GALL Report AMP)

ML060950645
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	03/22/2006
From:	Morgan M NRC/NRR/ADRO/DLR/RLRC
To:	Office of Nuclear Reactor Regulation
morgan M NRR/NRC/DLR/RLRC, 415-2232
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References
%dam200611, TAC MC9668
Download: ML060950645 (5)

Text

AUDIT WORKSHEET GALL REPORT AMP PLANT: ______________________________

LRA AMP: __________________________ REVIEWER: ______________________

GALL AMP: XI.M37, Flux Thimble Tube Inspection DATE: __________________________

Program Auditable GALL Criteria Documentation of Audit Finding Element Program A. The Flux Thimble Tube Inspection is an inspection program Consistent with GALL AMP: Yes No Description used to monitor for thinning of the flux thimble tube wall, which Document(s) used to confirm Criteria:

provides a path for the incore neutron flux monitoring system detectors and forms part of the RCS pressure boundary. Flux thimble tubes are subject to loss of material at certain locations in the reactor vessel where flow-induced fretting causes wear at Comment:

discontinuities in the path from the reactor vessel instrument nozzle to the fuel assembly instrument guide tube. An NDE methodology, such as eddy current testing (ECT), or other applicant-justified and NRC-accepted inspection method is used to monitor for wear of the flux thimble tubes. This program implements the recommendations of NRC Bulletin 88-09, Thimble Tube Thinning in Westinghouse Reactors, as described below.

1. Scope of A. The flux thimble tube Inspection encompasses all of the flux Consistent with GALL AMP: Yes No Program thimble tubes that form part of the reactor coolant system Document(s) used to confirm Criteria:

pressure boundary. The flux thimble guide tubes are not in the scope of this program. Within scope are the licensee responses to Bulletin 88-09, as accepted by the staff in its closure letters on the Bulletin, and any amendments to the licensee responses Comment as approved by the staff.

XI.M37 Flux Thimble Tube Inspection 1

Program Auditable GALL Criteria Documentation of Audit Finding Element

2. Preventive A. The program consists of inspection and evaluation and Consistent with GALL AMP: Yes No Actions provides no guidance on preventive actions. Document(s) used to confirm Criteria:

Comment:

3. Parameters A. Flux thimble tube wall thickness will be monitored to detect Consistent with GALL AMP: Yes No Monitored/ loss of material from the flux thimble tubes during the period of Document(s) used to confirm Criteria:

Inspected extended operation.

Comment:

4. Detection of A. An inspection methodology (such as ECT) that has been Consistent with GALL AMP: Yes No Aging Effects demonstrated to be capable of adequately detecting wear of the Document(s) used to confirm Criteria:

flux thimble tubes will be employed to detect loss of material during the period of extended operation. Justification for methods other than ECT should be provided unless use of the alternative method has been previously accepted by the Nuclear Comment:

Regulatory Commission (NRC). The inspection results will be evaluated and compared with the acceptance criteria established as discussed in element 6 below.

5. Monitoring A. The wall thickness measurements will be trended and wear Consistent with GALL AMP: Yes No and Trending rates will be calculated. Examination frequency will be based Document(s) used to confirm Criteria:

upon wear predictions that have been technically justified as providing conservative estimates of flux thimble tube wear. The interval between inspections will be established such that no flux thimble tube is predicted to incur wear that exceeds the Comment:

established acceptance criteria before the next inspection. The examination frequency may be adjusted based on plant-specific wear projections. Re-baselining of the examination frequency should be justified using plant-specific wear-rate data unless prior plant-specific NRC acceptance for the re-baselining was received. If design changes are made to use more wear-resistant thimble tube materials (e.g., chrome-plated stainless XI.M37 Flux Thimble Tube Inspection 2

Program Auditable GALL Criteria Documentation of Audit Finding Element steel) sufficient inspections will be conducted at an adequate inspection frequency, as described above, for the new materials.

6. Acceptance A. Appropriate acceptance criteria such as percent through-wall Consistent with GALL AMP: Yes No Criteria wear will be established. The acceptance criteria will be Document(s) used to confirm Criteria:

technically justified to provide an adequate margin of safety to ensure that the integrity of the reactor coolant system pressure boundary is maintained. The acceptance criteria will include allowances for factors such as instrument uncertainty, Comment:

uncertainties in wear scar geometry, and other potential inaccuracies, as applicable, to the inspection methodology chosen for use in the program. Acceptance criteria different from those previously documented in NRC acceptance letters for the applicants response to Bulletin 88-09 and amendments thereto should be justified..

7. Corrective A. Flux thimble tube wall thickness which do not meet the Consistent with GALL AMP: Yes No Actions established acceptance criteria must be isolated, capped, Document(s) used to confirm Criteria:

plugged, withdrawn, replaced, or otherwise removed from service in a manner that ensures the integrity of the reactor coolant system pressure boundary is maintained. Analyses may allow repositioning of flux thimble tubes that are approaching Comment:

the acceptance criteria limit. Repositioning of a tube exposes a different portion of the tube to the discontinuity that is causing the wear.

Flux thimble tubes that cannot be inspected over the tube length, that are subject to wear due to restriction or other defect, and that cannot be shown by analysis to be satisfactory for continued service, must be removed from service to ensure the integrity of the reactor coolant system pressure boundary.

The site corrective actions program, quality assurance (QA) procedures, site review and approval process, and administrative controls are implemented in accordance with XI.M37 Flux Thimble Tube Inspection 3

Program Auditable GALL Criteria Documentation of Audit Finding Element 10 CFR Part 50, Appendix B. As discussed in the appendix to this report, the staff finds the requirements of 10 CFR Part 50, Appendix B, acceptable to address the corrective actions, confirmation process, and administrative controls.

8. A. See Item 7, above. Consistent with GALL AMP: Yes No Confirmation Document(s) used to confirm Criteria:

Process Comment:

9. A. See Item 7, above. Consistent with GALL AMP: Yes No Administrative Document(s) used to confirm Criteria:

Controls Comment:

10. Operating A. In IE Bulletin 88-09, Thimble Tube Thinning in Westinghouse Consistent with GALL AMP: Yes No Experience Reactors, the NRC requested that licensees implement a flux Document(s) used to confirm Criteria:

thimble tube inspection program due to several instances of leaks, and due to licensees identifying wear. Utilities established inspection programs in accordance with IE Bulletin 88-09 which have shown excellent results in identifying and managing wear Comment:

of flux thimble tubes.

As discussed in IE Bulletin 88-09, the amount of vibration the thimble tubes experience is determined by many plant-specific factors. Therefore, the only effective method for determining thimble tube integrity is through inspections which are adjusted to account for plant-specific wear patterns and history.

XI.M37 Flux Thimble Tube Inspection 4

EXCEPTIONS Item Program Elements LRA Exception Description Basis for Accepting Exception Documents Reviewed Number (Identifier, Para.# and/or Page #)

1.

2.

ENHANCEMENTS Item Program Elements LRA Enhancement Description Basis for Accepting Enhancement Documents Reviewed Number (Identifier, Para.# and/or Page #)

1.

2.

DOCUMENT REVIEWED DURING AUDIT Document Number Identifier (number) Title Revision and/or Date 1.

2.

3.

4.

XI.M37 Flux Thimble Tube Inspection 5