ML20198K041
| ML20198K041 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 12/21/1998 |
| From: | Gore P, Langdon J, Yemma L CAROLINA POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML20198K030 | List: |
| References | |
| PROC-981221, NUDOCS 9812300327 | |
| Download: ML20198K041 (10) | |
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l Core Shroud Inspection Plan Unit 2 B214R1 Outage April 1999 Revision 1 Prepared by:
Phil Gore John Langdon Larry Yemma December 1,1998 Recommended by: Date:
Approved by:
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bNe & mB.w Date: /#/h//98
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9812300327 981221 PDR ADOCK 05000324 P PM li
, Core Shroud Inspection Plan Brunswick Steam Electric Plant, Unit No. 2 Refueling Outage 13 (B214RI), April 1999
SUMMARY
OF B214R1 INSPECTION PLANS The scope ofinspections for the Brunswick Steam Electric Plant (BSEP), Unit No. 2 Refueling Outage 13 (i.e., B214Rl) core shroud includes baseline inspections as well as reinspections.
Several factors were used to determine the scope: results of previous inspections performed on both BSEP units, results within the industry, and follow-up actions and commitments from previous inspections. Guidance on shroud inspection and flaw evaluation contained in the Boiling Water Reactor Vessel and Internals Program (BWRVIP) documents BWRVIP-01, " Core Shroud Inspection and Flaw Evaluation Guideline," Revision 2, and BWRVIP-07, " Guidelines for Reinspection of BWR Core Shrouds," were also used. The NRC Safety Evaluation on BWRVIP-07 was also used in determining the reinspection frequency of the core shroud welds.
A discussion of the inspection plans for each weld or component is provided in detail herein, and includes inspection history, results, and analytical conclusions.
Weld 111 will be re-inspected in 100 percent of the accessible areas using ultrasonic examinations (i.e., UT). Since the shroud head bolt lugs limit access of the inspection tooling to less than 20 percent of the upper side of the weld, Carolina Power & Light (CP&L) Company is having the inspection tooling modified to permit increased coverage of this weld. It is expected that the new technique will allow increasing the inspection coverage of this weld to over 75 percent. The inspection technique will be qualified in accordance with BWRVIP guidelines.
Welds 112 and 113 were structurally replaced with twelve clamps during the Refueling Outage 10 (i.e., B211RI), so these welds no longer require inspection. Five of the clamps will be visually inspected, which will complete the baseline inspection of the twelve clamps installed.
Weld 114 will be reinspected in 100 percent of the accessible area using UT.
Weld 115 will not be inspected. Analysis of the Refueling Outage 12 (i.e., B213RI) UT results concluded that the weld has sufficient structural margin to operate until Refueling Outage 15 (i.e., B216RI) before reinspection is necessary.
l Welds ll6A and 117 will not be inspected. Analysis of the B212R1 UT results concluded that these welds have sufficient structural margin to orerate until Refueling Outage 14 (i.e., B215RI) before reinspection is necessary.
( Weld Il6B will be reinspected in 100 percent of the accessible area using UT.
No inspections are planned for weld H8 orshroud support leg welds since inspection tooling and techniques have not been fully developed that will work on the BSEP type shroud.
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Since no flaws were found on weld H9 during the UT inspections performed in the B211R1 outage, no inspections are planned.
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l INSPECTION HISTORY AND PLANS FOR B214R1 For discussion purposes, coverage addresses the total amount of the welds' circumference that was inspected by the specified inspection technique (i.e., if 78 percent of the weld was inspected, this means 78 percent of the circumference was inspected). The amount of cracking discussed is l in reference to the amount of the inspected area that was found to be cracked (i.e., of the l 78 percent inspected,15 percent was cracked).
In the B211R1 outage,11.1 percent of the outside surface was visually (i.e., VT) inspected with i no cracking found.
In the B212R1 outage, the baseline inspection was completed using UT on 100 percent of the i accessible areas. This weld presents unique challenges to UT inspection since the shroud head hold down bolt lugs prevent access to most of the upper side of the weld. UT was performed on i 24 uniformly distributed locations representing 23.1 percent of the weld. A total of 3.6 percen*
cracking was found, with crack depths ranging from 0.22 to 0.27 inches. All of the cracking was located on the outer ring surface side of the weld. On the lower side of the weld,83.3 percent was UT inspected with 38.5 percent cracked. The crack depths were from 0.06 to 0.53 inches.
The guide rod brackets and core spray piping prevented access to the remaining areas of the weld. Analysis of the UT data showed the weld had sufficient structural margin to operate until the B214R1 outage before reinspection was necessary.
Welds H2, H3. and the Structural Clamos Welds H2 and H3 were structurally replaced with twelve clamps during the B211R1 outage; therefore, no inspection of these welds is required. Four of the clamps were VT inspected during the B212R1 outage, and three were inspected in the B213R1 outage. No indications were noted in either inspection. The five remaining clamps will be VT inspected during the B214R1 outage, thereby completing the baseline inspection of the twelve clamps.
Weld H4 In the B211R1 outage, the baseline inspection was completed using UT on 100 percent of the accessible areas. A total of 78 percent was inspected with 26.1 percent cracked. Jet pumps, guide rod brackets, and core spray piping prevented inspection of the remaining areas.
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,. Although analysis showed the weld to have sufficient structural margin to operate until the l
B214RI outage before reinspection would be necessary, CP&L elected to monitor selected areas
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4 of the cracking for growth. Select areas were reinspected during the B212R1 and B213R1 l
' outages, with no measurable growth noted.
In the B211R1 outage,100 percent of the accessible areas of the weld were inspected. Attempts
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were made to perform UT on this weld, but the inspection tooling would not pass by thejet pump riser brace arms. A total of 4.6 percent of the weld was inspected using UT, with no crack.ing identified. CP&L finished the inspections using VT. A more recent review of the inspection I tapes, indicates that the previously reported findings were very conservative. On the inside surface,100 percent of the area was inspected versus the 92.8 percent previously reported and 7.1 percent of the inspected area was cracked versus the 11.3 percent previously reported. On the outside surfaces,30.6 percent of the area was inspected with no cracking identified versus the 6.4 percent of the inspected area that was previously identified as cracked.
In the B213R1 outage, the baseline inspection was completed using UT on 100 percent of the accessible areas. The inspection tooling had been modified for the installed clamps and the clearance issues associated with the jet pump riser brace arms. A total of 83.6 percent of the lower side of the weld was inspected with no cracking identified. On the upper, outside diameter side of the weld, the riser brace arms again prevented transducer package access to 34.9 percent of the weld. No cracking was identified in the inspected area. The guide rod brackets, core spray piping, and jet pumps also limited access to areas on both sides of the weld.
Using the UT inspection results from the B213R1 outage,it has been shown that over 50 percent of the weld was inspected, which permits entry into BWRVIP-07, Table 1. Since 7.1 percent was found cracked, the reinspection frequency designated in Table 1 is 6 years. Therefore, reinspection is due during the B216R1 outage. A plant-specific analysis was performed which confirms that the weld has sufficient structural margin to operate until reinspection during the B216R) outage and substantiates the conclusions of BWRVIP-07, Table 1.
Details of the analysis and the revised VT inspection results are included in Attachment 1 of this enclosure.
Weld H6A In the B211R1 outage, over 11 percent of the outside surfaces were VT inspected with no circumferential cracking noted. Inaccessibility prevented inspections on the inside surfaces.
In the B212R' outage, the baseline inspection was completed using UT on 100 percent of the accessible areas. A total of 79 percent of the weld was inspected with 5.3 percent cracked. The cracking was located exclusively on the ring side of the weld, with crack depths ranging from 0.08 to 0.27 inches. Analysis showed the weld has sufficient structural margin to operate until the B215R1 outage before reinspection is necessary.
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Weld II6B i in the B211R1 outage, over 11 percent of the outside surfaces were VT inspected with one, 1.5 inch circumferential crack noted. Inaccessibility prevented inspections on the inside surfaces.
In the B212R1 outage, UT was performed on 100 percent of the accessible areas of the weld.
78.4 percent was inspected with 69.3 percent cracked. The cracking initiated exclusively from the inner plate-side heat affected zone of the weld, with crack depths ranging from 0.10 to
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0.79 inches. l In the B213R1 outage, UT was used to re-inspect 100 percent of the accessible areas. Using modified tooling, CP&L increased the coverage to 84.3 percent with 73 percent found cracked.
No significant growth was noted in the previously inspected areas. The crack depths ranged from 0.05 to 0.75 inches. Jet pumps, guide rod brackets, and core spray down comers prevented inspection of additional areas. Analysis showed the weld had sufficient structural margin to operate until the B214R1 outage before reinspection is necessary.
Weld 117 In the B211R1 outage, over 1I percent of the outside surfaces were VT inspected with no circumferential cracks noted. Inaccessibility prevented inspections of the inside surfaces.
In the B212R1 outage, the baseline inspection was completed using UT on 100 percent of the accessible neas. A total of 75.6 percent was inspected with 10.9 percent cracked. The cracking initiated exclusively from the 304 stainless steel side of the weld on the inner surface. The crack depths were from 0.06 to 0.52 inches. Analysis showed the weld had sufficient structural margin to operate until the B215R1 outage before reinspection is necessary.
Weld IIS No previous inspections have been performed, or are planned during the B214R1 outage, for this weld. This weld presents significant accessibility challenges since access to the upper side of the weld is very restricted due to the jet pump diffusers, core spray piping, and guide rod brackets.
CP&L estimates that less than 40 percent of the weld is accessible for UT from the annulus area due to the clearance between the jet pump diffusers and the shroud support plate (i.e., less than 2 inches) and the openings for the jet pump diffusers in the jet pump baffle plate.
Access to the weld from beneath the baffle plate is even more restrictive due to the openings in thejet pump baffle plate for thejet pump diffusers and the core shroud support legs. Total coverage is estimated to be less than 30 percent of the weld from this side of the weld. The most l coverage for this weld can be obtained from the fuel side of the shroud support; however, a l considerable number of fuel cells will require vacating to gain access.
No inspection techniques or tooling have been completely developed and tested that will inspect in excess of 50 percent of this weld. While some inspection tooling is available in the industry,it l
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will not provide complete coverage of all areas ofinterest on the weld, nor will it cover at least
- 50 percent of the weld circumference. When inspection tooling and techniques are available and tested that will provide at least the minimum required inspections, CP&L plans to inspect this weld consistent with BWRVIP guidance.
Weld H9 During the B212R1 outage, the baseline inspection was completed using UT on 100 percent of the accessible areas. Over 99 percent of the weld was inspected with no cracking noted. Based on the current BWRVIP-38 guidelines, reinspection is not necessary until the B217R1 outage.
Core Shroud Sunnort Lees There currently are no inspection equipment, techniques, or approved BWRVIP inspection and evaluation guidelines available for inspecting the core shroud :;upport legs. When these become available, CP&L will inspect these areas consistent with BWRVIP guidance.
Vertical Welds VI and V2 (located between welds H1 and H2)
These welds were visually inspected on the outside diameter surfaces in 1991 with no indications found. Since these welds are outside the beltline region as defined by the current BWRVIP-07 guidelines, no inspections are planned.
Vertical Welds V3 and V4 (located between welds H3 and H4)
These welds were VT inspected during the B210R1 outage on the inside and outside surfaces with no indications noted. These welds will be baseline inspected using UT on 100 percent of the accessible areas during the B214R1 outage.
Vertical Welds V5 and V6 (located between welds H4 and 115)
Weld V5 was VT inspected during the B210R1 outage on the inside and outside surfaces with no indications noted. Weld V6 was VT inspected during the B210R1 outage on the outside surface only with no indications noted. These welds will be baseline inspected using UT on 100 percent of the accessible areas during the B214R1 outage.
Vertical Welds V7 and V8 (located between welds H5 and H6)
These welds were VT inspected during the B210R1 outage on the outside surface with no indications noted. Since the cracking on welds H5 and Il6A is less than the current BWRVIP guidelines, no inspections are planned during the B214R1 outage.
r Vertical Welds V9. V10 and Vil (located between welds II6B and 117)
These welds were VT inspected during the B210R1 outage on the outside surfaces with no indications noted. Since these welds are outside the beltline region, as defined by the current BWRVIP-07 guidelines, no inspections are planned.
Rine Seement Welds (H1 rine. H2/II3 rine, and H6A/H6H rine)
Welds H1, H6A, and H6B are not repaired; therefore, no inspections are required by the current BWRVIP-07 guidelines. The clamps installed on the Il2/H3 welds replace the H2/H3 ring segment welds; therefore, no inspections are necessary.
INSPECTION SCOPE EXPANSION Scope expansions will be performed dependent on inspection results on a component-by-component basis in accordance with BWRVIP guidance.
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, Attachment 1 ;
To i Core Shroud Inspection Plan For Brunswick Steam Electric Plant, Unit No. 2 Refueling Outage 13 (B214RI), April 1999 Core Shroud Weld H5 Inspection and Evaluation Summary VISUAL INSPECTION - 1994:
During the B211 R1 outage, visual examinations (i.e., VT) were performed on the inside (i.e., ID) ;
and outside (i.e., OD) surfaces of the H5 core shroud weld. The VT results were documented in Engineering Evaluation Report (EER) 94-0077 and are summarized below:
. 92.8 percent of the inside surface was inspected,62.8 inches of circumferential cracks and three short axial cracks were identified
. 30.6 percent of the outside surface was inspected,11 inches of circumferential cracks and two short axial cracks were identified ULTRASONIC INSPECTION - 1997:
During the B213R1 outage, ultrasonic examination (UT) was performed on OD of core shroud weld H5. The UT results were documented in Engineering Service Request (ESR) 97-00034. No indications were noted using this technique. The following areas of the weld were inspected:
. 34.9 percent of the upper side of the weld, with no indications
. 83.6 percent of the lower side of the weld, with no indications It was understood at that time that the previous visual irapection findings were not reproduced in the areas where the VT and UT overlapped. Since the cracking percentage of the VT examination was small compared to the inspected length, it was determined that an acceptable analysis would be obtained by using the current UT data only.
' REVIEW OF TIIE 1994 VT INSPECTION TAPES:
In the effort to resolve the differences between the 1994 and 1997 data, a review of the VT inspection tapes from 1994 was performed. All areas were closely reviewed. This review yielded the following conclusions:
. Verified that 100 percent versus 92.8 percent of the inside surface of weld H5 was VT inspected.
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- Each previously reported indication was reviewed. Of the 27 indications reported on I
the inside surface,10 were axially and 17 were circumferentially oriented. The review concluded that eight of the axially oriented indications were cracks. The !
remaining two indications are non-relevant; both being the edges of oxide scale on the shroud plate, e : Of the 17 circumferential indications reported, the review concluded eight were cracks. The remaining nine indications were either non-relevant or axially oriented.
- On the outside surface, one 11 inch long circumferential crack was reported. The review of the tape revealed this to be a non-relevant indication associated with grinding marks and pitting.
The conclusion of this review of the 1994 VT inspection is that 100 percent of the inside surface was inspected with 39.5 inches (7.1 percent) of total cracking. 'Of that cracking,16.5 inches (3 percent) was UT inspected from the OD of the weld (lower side of the weld) and 14.0 inches (2.5 percent) was UT inspected from the OD of the weld (both the upper and lower sides). Based on this data, Carolina Power & Light Company concluded these cracks are very shallow and have experienced little to no crack growth over the period from 1994 to 1997.
ANALYSIS VERIFICATION:
To substantiate the applicability of BWRVIP-07, Table 1, two distributed ligament length models of the combination of the VT and UT data were generated. The first model is based on the original IM4 VT data and the 1997 UT data. The second model is based on the revised 1994 VT data and the 1997 UT data. The conservative assumptions used in these analyses are stated below:
- A crack growth rate of 5.0E-5 inches / hour was used.
. The evaluation duration was 3,200 days (1994 until 2003).
- Used a size uncertainty of 2t (i.e.,3 inches) at each crack tip.
- All areas not VT inspected from both ID and OD or UT inspected from above and below the wcld were considered fully cracked.
- The area where the confirmed ID crack that was not picked up by UT was considered fully cracked.
l The results of the analyses agree with Table 1 of BWRVIP-07 that the next inspection is due L within six years from 1997 (i.e., by 2003). This also confinns that BWRVIP-07 is conservative since the analyses used very conservative assumptions as design inputs.
SUMMARY
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i The coverage of weld H5, using UT technique, is conservatively computed to be 59.3 percent of the weld. No cracking was observed. The method used to compute this value is as follows:
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l 125.8 inches was inspected from both sides, and 175.2 inches was inspected from the
! lower side only. A two-sided inspection fully interrogates all four weld toes while a one-sided inspection fully interrogates two weld toes. Therefor _e, [(125.8 x 4) +
i (175.2 x 2)] / (360 x 4) represents the coverage of weld H5.
I Additional coverage of weld H5 was obtained which was not considered in the equation above.
Specifically, a one-sided UT does interrogate a third weld toe with some limitation. A crack l greater than 0.24 inches in depth can be seen on the upper ID using a UT from the lower OD.
This additional coverage was considered in our previous submittal. Recomputing the inspection coverage to include the additional coverage of the third weld toe yields 71.5 percent, which was reported in a submittal dated November 10,1997 (Serial: BSEI' 97-0489).
l Visual 100 percent of the ID and 30.6 percent of the OD was inspected which equates to 65.3 percent of ,
the weld as follows:
[(360 x 2) + (110 x 2)] /(360 x 4)
The total length of cracking was computed to be 39.5 inches, which equates to 25.5 degrees or -
7.1 percent (i.e.,25.5/360).
CONCLUSIONS:
The reassessment of core shroud weld 115 adequately demonstrates that this weld is structurally sound and capable of performing its function through the next inspection interval as outlined in BWRVIP-07.
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