ML20078P673

Core Shroud Reinsp Plan Unit 1 B110R1 Outage,Apr 1995

ML20078P673
Person / Time
Site:	Brunswick
Issue date:	02/09/1995
From:	Langdon J, Wagoner V, Wilton B CAROLINA POWER & LIGHT CO.
To:
Shared Package
ML20078P661	List: BSEP-95-0080, Forwards Core Shroud Reinsp Plan Unit 1 B110R1 Outage,Apr 1995, in Response to GL 94-03, IGSCC of Core Shrouds in Bwrs. Reinsp Plan & Plans for Evaluation/Repair of Facility Core Shroud Discussed W/Nrc During Cp&L/Nrc 950117 Meeting ML20078P673
References
PROC-950209, NUDOCS 9502170173
Download: ML20078P673 (6)

Text

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Core Shroud Reinspection Plan Unit 1 B110R1 Outage April,1995 ,

Prepared hv:

Vaughn Wagoner John Langdon Blane Wilton Itecommended by: ( dhi i bt Date: J/S,/9[

Approved by: i J. M Date:%/f/95' l

PR P

bC 0 000 56 PDR

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. i Core Shroud Reinspection Plan ,

Unit i B110R1 Outage i April,1995 l

EXECUTIVE

SUMMARY

The scope of reinspection fbr the Unit 1 Core Shroud is based on the results of previous inspections performed on both Unit 1 and Unit 2, ibliowup actions and commitments established from the last inspection in Engineering Evaluation 93-0536, and guidance on i shroud inspections contained in NRC Generic Letter 94-03. I The inspections perfbrmed in Unit I during the Summer and Fall of 1993 meet the current 'I requirements of NRC Generic Letter 94-03 for core shroud inspections, and meet the J requirement ofinspecting essentially 100% of accessible areas of the shroud circumferential  !

welds. In addition, vertical welds and several attachment welds, and other parts of the core ,

support structure were examined during these inspections. Specific areas on several  !

circumferential welds were marked, so that they could be re-examined to determine the ,

extent of crack growth during the last cycle.  !

1 The reinspection scope is structured to meet the intent of NRC Generic Letter 94-03, and l fbcuses on three objectives: re-examination of selected areas to determine crack growth,  ;

examination of some of the installed clamps to verify no inservice degradation, and utilization of specifically developed tooling to examine accessible portions of certain welds i that could nu be accessed before. Specifically, UT measurements will be repeated at j selected areas on 111 and 115. and VT measurements will be repeated on H5. Two of the  !

12 clamps will be examined for degradation. CP&L is also developing UT techniques to i inspect the ID surface of the core support ring welds H6a and H6b and associated fillet  !

welds. The automated UT scanner commonly being used for shroud inspections will not l work on the Brunswick shrouds, because ofinterference with the clamps. Specialized l tooling is under development to perform these inspections. .

Ultrasonic inspections will be conducted using " phased array" technology. This technology I allows electronic manipulation of the ultrasonic sound beam without hardware changes. It i has been successfully used Ihr a number of years both domestically and abroad. The equipment and procedures Ihr UT. as well as Ihr VT, will be qualified in accordance with  ;

the guidelines of the BWRVIP. l l

An engineering evaluation of the results of the inspection will be performed, using the flaw .

evaluation guidance contained in the " Core Shroud Inspection and Evaluation Guidelines," j issued by the BWRVIP. CP&L is developing a contingency shroud repair plan.

CP&L is working closely with the BWRVIP to evaluate industry information and incorporate " lessons learned" into the overall inspection program. Inspection of areas Page 1 l

below the core support plate and other vessel attachments and internals will be perfbrmed consistent with the guidance provided by the BWRVIP.

UNIT 1 CORE SIIROUD REINSPECTION PLAN The scope of this reinspection plan meets the intent of requested licensee action item 3 of Generic 1.etter 94-03, fbr a reinspection of the shroud. This action item requires an inspection plan for all shroud welds or justification for not inspecting certain welds, and requires use of technology and industry experience to perfbrm inspections that will consistently detect IGSCC.

The reinspection plan fbr the core shroud fbcuses on reinspecting specific areas inspected last outage to determine crack growth rates, and to examine the inside areas of core support ring welds ll6a and ll6b. Visual inspections of the OD were conducted on these welds, since tooling did not exist at the time to examine the inside areas. The tooling commonly being used in industry, the General Electric Company "OD tracker," will not work on the BNP shroud due to interference from the installed clamps. Specialized tooling is being developed to inspect these welds.

Weld lil will be re-examined in 4 places ultrasonically, at the 30",140", 259", and 330" azimuths. This is a ring weld, with the "end grain" exposure and significant cold work. It was evaluated fbr one cycle, and must be reevaluated this outage. Other locations that were previously ultrasonically examined may be substituted, if required. Welds 112 and 113 will not be inspected because they have been structurally replaced by the clamps. Weld 114 will not be reinspected since only relatively minor axial cracking was seen at this weld, and areas on a similar weld (115) will be examined to determine crack growth. Two circumferential indications on weld 115 at 169" and 264" will be re-examined both visually and ultrasonically. This plate-to-plate weld area experiences harsher environment and more fluence than other welds. The data from this weld examination will be used to benchmark the GE PLEDGE Crack Growth Model for the Brunswick Plant and allow accurate prediction of crack growth rates. l Specialized tooling will be used to examine accessible portions of welds ll6a and il6b.

Access is limited to 6 areas between jet pump pairs fbr each of these welds. No further inspections of Weld 117, Weld 118, and areas below the core plate will be performed this outage because equipment and techniques are still being developed fbr these inspections. j Future inspection plans for these areas will be developed consistent with guidance provided by the llWRVIP. Portions of the OD of117 and 118 were examined last outage using enhanced VT, and no indications were found. j 1

The BWRVIP is currently developing guidance ihr qualification of the 119 shroud weld examinations. The 119 weld is located directly behind one of the vessel beltline welds that 1 will be examined this outage. Interrogation of the 119 weld will occur during the vessel beltline weld examination; however, since the BWRVIP has not completed development of Page 2

qualification criteria for the 119 weld inspection technique, the results of the H9 weld examinations can not be appropriately evaluated. CP&L will address the status of the core shroud 119 weld examination / evaluation in the post-outage inspection results submittal.

Two of the 12 repair clamps will be visually inspected to ensure no degradation during the last cycle of operation.

Details of the scope of inspection for each weld, and for the clamps, are summarized in Table 1.

INSPECTION SCOPE EXPANSION llased on the results of the Brunswick Plant Unit 1 Core Shroud Reinspection Plan, additional inspections of the core shroud (including repair clamps) may be necessary to support an engineering evaluation to demonstrate core shroud integrity. CP&L will address any scope expansion in our submittal of the inspection results to the NRC staff.

EVALUATION OF INSPECTION RESULTS An engineering evaluation will be perfbrmed on the inspection results, using the flaw evaluation guidance of the BWRVIP " Core Shroud Inspection and Evaluation Guidelines."

No significant changes from the last inspection results are expected. No repairs are anticipated ihr this outage. CP&L will submit the inspection results in accordance with the guidance of NRC Generic Letter 94-03.

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TAllLE 1 Unit 1 Outage - Core Shroud Reinspection Scope WELD PREVIOUS INSPECTION REINSPECTION COhlh1ENTS RESULTS h1ETilOD*

Ill VT of 100% of ID & OD. UT UT from OD 4 of 8 areas previously UT'ed.

App. 74% of OD cracked.

UT at 8 locations, <0.3" to 0.7" 112 VT of 100% of OD. App. N/A Replaced by clamps. See clamp inspection below.

62% cracked in ring. UT at 4 locations, <0.3" to 0.75" 113 VT of 100% of ID & OD. N/A Same as 112.

Near continuous cracking on ID in ring. UT at 11 locations. 0.95" to 1.71" II4 VT of 100% of ID & 45% of Nonc planned No circumferential indications identified last time, so sufficient OD (100% of accessible OD). structural margins exist. Any anticipated growth of axial Several small axial cracks. indications would not impact structural margins. 115 is a similar No circumferential cracks. weld, and is being inspected.

115 VT of 100% of ID & 45% of Partial VT plus UT VT of " punch marked" cracks for length on the ID. UT of 2 OD (100% of accessible OD). previous areas to determine crack growth.

Circumferential cracks passed screening criteria. UT at 2 locations, with depths <0.3" to 0.6" Page 4

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