ML19254F016
| ML19254F016 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 10/31/1979 |
| From: | Bixel D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19254F017 | List: |
| References | |
| NUDOCS 7911050354 | |
| Download: ML19254F016 (5) | |
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General Offeces: 212 West Machigan Avenue, Jackson, Michigan 49201 e Area Code 511788-0550 October 31, 1979 Director, Nuclear Reactor Regulation Att Mr Dennis L Ziemann, Chief Operating Reactors Branch No 2 US Huclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - REPORT OF INVESTIGATION AND REPAIR OF REACTOR VESSEL CONTROL ROD DRIVE PENETRATION Leakage of several milliliters per minute was identified during a Big Rock Point hydrostatic test on April, 20, 1979.
The leakage was located where one control rod drive (CRD) housing penetrates the bottoni head of the reactor vessel. This leakage was reported in Licensee Event Report 79-18 submitted May 2, 1979. A report describing the investigation and repair efforts associated with this leakage wac submitted August 79, 1979.
Fors,arded as Attachment I to this letter is a change to the August 29, 1979 report. Attachment II to this letter provides Consumers Power Company's response to questions regarding the repart which were raised during an Octcher 18, 1979 telephone conversation.
David A Bixel (Signed)
David A Bixel Nuclear Licensing Administrator CC JGKeppler, USNRC 1267 265 5e 4"y 3
7911050
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ATTACHMENT I Revision to " Report of Investigation and Repair of Reactor Vessel Control Rod Drive Penetration - Big Rock Point Plant" submitted August 29, 1979.
Section II.J.2 of the subject report describes a high amplitude reflector in the Incenel inlay at approximately the 280 to 290* azimuth position.
Additional preservice examination, performed subsequent to report preparation, places this reflector above the weld-to-Inconel inlay weld material approximately 0.2 inch from the weld OD.
The disposition of this reflector remains as a slag inclusion.
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2 ATTACHNENT II Consumers Power Company responses to NRC requests for additional information pertaining to " Report of Investigation and Repair of Reactor Vessel Control Rod Drive Penetration - Big Rock Point Plant" submitted August 29, 1979.
NRC Request -1 Provide a summary of the ultrasonic examination procedures to be used in future ISI for vessel wall and housing.
Consumers Power Company Response The ultrasonic examination procedures which currently exist for these inspections are:
1.
SWRI-NDT-600-17 Revision 2 - Manual Ultrasonic Examination for Thickness and Laminar Type Defects in Pressure Vessel Material.
2.
SWRI-NDT-800-66 Revision 0 - Manual Ultrasonic Examination of Big Rock Point Reactor Vessel Control Rod Drive Housing.
3.
SWRI-NDT-800-67 Revision 0 - Manual Ultrasonic Examination of Big Rock Point Stub Tube-to-Lower Head Weld.
Copies of these procedures are attached for information.
These procedures represent state-of-the-art techniques for 'rforming the required ultrasonic examinations.
Improvements in nondestructive axamination technology would, of course, be incorporated into revisions to these procedures. These procedures, or their equivalent, will be used for the examinations to be conducted during future inservice inspections.
NRC Request - 2 Define size and orientation of the smallest crack in the vessel wall which can be seen and the same for the largest crack which cannot be seen using planned procedures / techniques.
Consumers Power Company Response SWRI-NLT-600-l', SWRI-NDT-800-66, and SWRI-NDT-800-67 or equivalent current
" state-of-the -art" ultrasonic examination procedures will produce data from any of the eflectors normally anticipated during Section XI - type work within the limitations normally experienced with Section XI examinations.
Reflectors oriented perpendicular to the incident ultrasonic beam within approx: =tely 5' to 10* will be favorably oriented for easy. detection.
Likewise, corner-like reflectors favorably oriented or rough surfaced reflectors with plate facets favorably oriented will tend to be easily detectable. Metal path attenuation will, of course, affect detectability as will surface roughness and couplant integrity. These procedures quite easily
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3 produced the anticipated signals from artificial reflectors placed in the vessel shell, Inconel inlay, various portions of the stub tube weld, and the stub tube directly above tne upper stub tube weld interface in the mock-up fabricated for UT calibration. The reflectors in the stub tube and stub tube weld had various orientations corresponding to what might be considered the most probable directions <f flaw propagation. The reflectors in the vessel shell were placed to determine examination capabilities with shadowing effects.
It is considere.1 that successful qualification of the procedures on the detailed mock-up provides adequate assurance that examination of the F-2 housing penetration area of the vessel shell and stub tube will provide data within the expected accuracy of Section XI examinations which can be readily evaluated by Section XI acceptance criteria.
NRC Request - 3 Specify the flaw size which would require repair per Section XI of ASME code and specify whether planned exams could detect it (vessel wall).
Consumers Power Company Response Flaw size which would require repair per Section XI is derived from the 1977 edition, Paragraph IWB-3510. Limits are obtained from Tables IWB-3510-1:
Allowable Planar Indications, and IWB-3510-2: Allowable Laminar Indications.
Using Table IWB-3510-1:
Known 1) t = 6.2 Inches (Measured)
- 2) Total allowable depth of subsurface indication is 2a.
Unknowns a & 1; therefore assume the smallest value of a/t to be conservative.
This value is 2.3% so a/t = 2.3% a = (.023)(6.2 In) a =.14 In Total allowable depth of subsurface indication is.28 in.
Detection would be accomplished as described in response to Request Number 2.
NRC Request - 4 Commit to monitor at least one inch above and below the rolled zone during housing UT.
Consumers Power Company Response As stated in the present examination procedure, angle beam examination shall be conducted on the accessible portions of the CRD housing. The thermal sleeve is intended to be removed for inspection; therefore, the one: inch above and below limit is satisfied.
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4 NRC Request - 5 P.19 of Consumers Power Company report cites a code requirement for either volumetric or surface exams. Commit to using volumetric for all areas accessible with volumetric equipment; ie, a surface exam will not be substituted for a volumetric which could be done.
Consumers Power Company Response Volumetric examination shall be done wherever possible.
NRC Request - 6 "crify that leakage from the housing would be considered part of " unidentified leakage" per Technical Specifications.
Consuma's Power Company Response No technique is currently available to quantify any leakage from CRD F-2 housing at operating conditions. Thus, this leakage will be included as part of " unidentified leakage." If methods can be developed to quantify any such leakage, it may be considered part of " identified" leakage. Any leakage fro, CRD F-2 housing will be handled under existing Technical Specifications leakage requirements, and no specific report of leakage will be made unless the appropriate " unidentified" or " identified" specification is exceeded.
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