ML20083E756
| ML20083E756 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 09/30/1991 |
| From: | Schrage J COMMONWEALTH EDISON CO. |
| To: | Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9110030160 | |
| Download: ML20083E756 (3) | |
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September 30,1991 Dr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 Attn: Document Control Desk
Subject:
Ouad Cities Nuclear Station Unit 2 Reactor Head and Upper Shell Inspection Plan NRCEocket NoJ0:265
References:
(a) R. Stols to T.E. Murley letter dated May 4,1990 (b) R. Stols to T.E. Murley letter dated January 3,1991
Dear Dr. Murley:
On April 19,1990, members of the Nuclear Reactor Regulation's (NRR) and Commonwealth Edison Company's (CECO's) staff conducted a technical meeting to discuss the cracks identitled in the Quad Cities Unit 2 Reactor Vessel Head. During that meeting, CECO committed to perform inspections of the reactor vessel heads at each of its Bolling Water Reactor (BWR) Plants.
In Referenca (a). CECO committed to review the fabrication records for the upper vessel structure for each DWR unit and provide this information to your office.
This information was provided in Reference (b). Attached for your staff's review is the Reactor Head and Upper Shell Inspection Plan for Quad Cities Unit 2 for the upcoming refuel outage (O2R11) which is scheduled to begir, on December 28,1991.
The cracks found in the Quad Cities Unit 2 reactor vessel head were located mainly in the back-clad region of the head to flange weld. The apparent primaiy cause of these cracks appeared to be fabrication related.. The f abrication history of the Quad Cities Unit 2 U pper Vessel revealed major f abrication mismatches with manual back clad welds at t1e head to-flange area. The inspection therefore will concentrato upon this area. No inspection is recommended for the reactor vessel upper shell to flange weld since no major f abrication mismatch was identified for this wold.
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D'r, Thomas E. Murley September 30,1991 The inspection plan door, not encompass the uppermost shell to shell weld due to technological limitations. Remoto automated ultrasonic oxamination technology for BWR vessel welds is underway; however, the technology cannot be utilized reliably at this time. Examination of the uppermost shell-to shell weld cannot be achieved by examination of the outer diameter due to inaccessibility, and manualliquid penotrant and/or manual ultrasonic examination from the inner diamotor cannot be accomplished due to the radiation doses anticipated at that area. Commonwealth Edison, however, will perform the inspections when the technology is better developed.
The plan rec uires visual examinations (VT 3 and VT 1) of the huad to-flange weld to identify any ev dence of potential cracks. These techniques will be followed by a liquid dyo penetrant (PT) examination and an ultrasonic (UT examination. Finally UT sizing will be used to map all crack indications as well as the Iighest PT Indications All flaw characteristics identiflod by the above examination techniques will be compared to the 1990 as-lef t flaw characteristics. Any apparent crack Orowth data will be resolved prior to unit start-up.
If there are any questions or comments on this plan, pleass direct them to Respectfully, f
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v John L. Schra Nuclear Licensing Adke inistrator Attachment ec: A. Bert Davis, Regional Administrator, Rlli L.N. Olshan, Project Manager, Quad Cities T.E. Taylor, Senior Resident inspector, Quad Cities B.J. Elliot, NRR Technical Staff I
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PROPOSED REACTOR HEAD AND UPPER SHELL INSPECTION PLAN OUAD CITIES UNIT 2 1.
Visual Examination (VT 3) on 100% of the Reactor Pressure Vessel (HPV) Head ID outside of the 12 Inch wide band which is centered on the RPV head to flange weld.
Lighting adequacy should be verified with a 1/32 inch black line on a 18% neutral gray card. Conditions to be examined for and recorded are:
a.
Cracks b.
Linear Indications c.
Heavy / unusual rust streaks 2.
Direct Visual Examination (VT.1) of all excavated cavities for pitting and cracking of the low alloy steel material. Lighting adequacy must be verified with a 1/32 inch black line on a 18% neutral gray card.
3.-
Liquid dye penetrant test (PT) on the followlag:
a.
All recordable Indications found by activity 1 above.
b.
The complete 12 Inch band centered on the ID of the RPV head to flange weld and areas surrounding the PT Indication
. (approximately 3 inch radius found in 1990 around the 25 Inch evaluation). All PT indications shall be recorded.
4.
Ultrasonically test (UT), from the OD,100% of the RPV head to flange weld using the enhanced UT technique (45 dooreelm recorded. The examination coverage roll response ratio of 2:1 or better shall shall be the same coverage achieved in 1990.
5.
UT sizing, from the ID, the following:
a.
All cracks found by activity 3.a.
b.
All cracks located in and/or associated with all e.
ivated cavities, c.
The three PT indications with the heaviest penetrant bleed out found by activity 3.b outside the cavity areas The flaw characteristics found by activities 3.b.,4, and 5.b. shall be compared to the 1990 as left flaw characteristics,if available, to determine crack growth. Any apparent crack growth data will be reviewed by Commonwealth Edisrin for resolution prior :o unit start-up.
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