ML20112D503

Applicant Exhibit A-R-5,consisting of June 1984 Suppl to Rept on Bryon QC Inspector Reinsp Program

ML20112D503
Person / Time
Site:	Byron
Issue date:	08/24/1984
From:	COMMONWEALTH EDISON CO.
To:
References
OL-A-R-005, OL-A-R-5, NUDOCS 8501140326
Download: ML20112D503 (18)

Text

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Supplement to Report on the Byron QC Inspector Reinspection Program Docket No. 50-454 and 50-455

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l SUPPLEMENT TO REPORT ON THE BYRON QC INSPECTOR REINSPECTION PROGRAM CONTENTS Page I. INTRODUCTION SI-l

11. SUPPLEMENTAL INSPECTIONS AND EVALUATIONS S 11- 1 FOR SUBJECTIVE WELD ATTRIBUTES FOR HATFIELD ELECTRIC AND PITTSBURGH TESTING III. SUPPLEMENTAL INSPECTIONS AND EVALUATIONS FOR Sill-1 OBJECTIVE ATTRIBUTES FOR HATFIELD ELECTRIC i

51-1 I. INTRODUCTION The Byron QC Inspector Reinspection Program was established to verify the effectiveness of former certification practices and QC Inspector Qualification programs by reexamining, on a sampling basis, inspections performed by QC Inspectors certified prior to September,1982. The Reinspection Program was completed and confirmed the adequacy of inspector activities at the Byron Station.

Although the Reinspection Program focused on an assessment of individual inspector qualifications and contractor certification practices, a significant amount of work quality data was accumulated. Observed discrepancies were evaluated for their significance to the design and the quality of construction work at Byron was determined to be adequate.

This supplement provides the results of supplemental inspections and evaluations which Commonwealth Edison committed to in the Report on the Byron QC Inspector Reinspection Program, Feburary 1984 (hereinaf ter referred to as the Reinspection Program Report). These supplemental inspections and evaluations covered subjective weld attributes for Hatfield Electric Company and Pittsburgh Testing Laboratory and objective attributes for Hatfield Electric Company.

Sil-1 II. SUPPLEMENTAL INSPECTIONS AND EVALUATIONS FOR SUBJECTIVE WELD ATTRIBUTES FOR HATFIELD ELECTRIC AND PITTSBURGH TESTING A. INTRODUCTION Appendix C to the Reinspection Program Report included commitments to perform supplemental inspections and evaluations (see Exhibit C-2, pages 10 and 13). These supplemental inspections included highly stressed welds for Hatfield Electric and Pittsburgh Testing and welds with overlap for welds inspected by Pittsburgh Testing. The engineering evaluation of weld discrepancies noted in these supplemental inspections and evaluations followed the same process described in Exhibit C-2 of Appendix C in the Reinspection Program Report.

B. HATFIELD ELECTRIC Two sets of supplemental inspections were performed. One set of evaluations involved identifying highly stressed welds from the population of Hatfield Electric subjective weld discrepancies identified in the Reinspection Program. The other set of inspections involved highly stressed welds inspected by inspectors whose work was not reinspected in the Reinspection Program. The supplemental inspections and evaluations completed for Hatfield Electric show that the highly stressed welds are capable of carrying the design loads even with the presence of weld discrepancies.

1. Highly Stressed Welds Within Reinspection Program This evaluation considered the highly stressed connection welds from the entire population of Hatfield Electric weld discrepancies in the Reinspection l Program. The type of supports which have the highest stressed welds are cable tray supports. Cable tray support connections fall into four basic groups:

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S 11- 2 e auxiliary steel connections to in-place building steel, e top connections for supports to auxiliary or in-place building steel, e internal connections for support members to vertical members, and e cable tray hold down connections to horizontal support members.

The cable tray supports associated with the discrepant welds shown in Table C-1 of Appendix C to the Reinspection Program Report were identified. The design margins for the connections in each group were then tabulated. Then at least 15 supports having highly stressed connections from each of the four groups were selected for weld mapping and evaluation. The weld maps were used to determine the reduction in weld strength based on the mapped weld discrepancy. The results of the engineering evaluation are shown in Table SCE-9.

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Table SCE-9 Results of AWS Weld Discrepancy Evaluation for Highly Stressed Cable Tray Welds - Hatfield Electric Weld Discrepancy Category 2 A B1 B2 C Weld Weld No Strength Strength Weld No. of Weld Structural Reduced Reduced Rejected Weld Type Discrepancies Impact by < 10% by 210% (Cracks)

Auxiliary steel connections 21 0 4 17 0 Top connections for supports 16 0 3 13 0 Internal connec-tions for supports 17 0 4 13 0 Cable tray hold-down 15 0 8 7 0 TOTAL 69 0 19 50 0 i Notes for Table SCE-9 1

1. The format of Table SCE-9 corresponds to Table CE-9 in Exhibit C-2 of Apoendix C of the Reinspection Program Report.

l 2. For definition, refer to page 1 in Exhibit C-2 of Appendix C of the Reinspection Program Report.

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SII-4 The results of the engineering evaluation showed that each weld is capable of carrying the design loads; thus, structural integrity is not impaired.

.This evaluation demonstrates that 69 highly stressed cable tray connections with weld discrepancies are capable of carrying the design loads.

2. Highly Stressed Welds Outside the Reinspection Program This inspection addressed highly stressed welds for the 10 Hatfield weld inspectors whose work was not reinspected during the Reinspection Program.

Approximately 60 highly stressed welded connections from the four groups of cable tray support welds were reinspected for the 10 Hatfield inspectors' work. A total of 187 welds were mapped. The types of weld discrepancies identified were similar to the discrepancies in the welds identified in the Reinspection Program.

The results of the engineering evaluation of these connections are shown in Table SCE-9A.

S11-5 Table SCE-9A Results of AWS Weld Discrepancy Evaluation for Highly Stressed Cable Tray Welds Outside the Reinspection Program - Hatfield Electric Weld Discrepancy Category A B1 B2 C Weld Weld No. No Strength Strength Weld of Weld Structural Reduce < Reduced Rejected Weld Type Discrepancies impact by < 10% by 210% (Cracks)

, Auxiliary steel connections 40 0 19 21 0 Top connections for supports 29 0 11 18 0 Internal connect-tions for supports 30 0 12 18 0 Cable tray hold-down 88 0 48 39 1 TOTAL 187 0 90 96 1 In the case where a cracked cable tray hold-down weld was found during these additional inspections, the other welds in the connection were capable of carrying the load. The engineering evaluation of these highly stressed welds showed that each weldment is capable of carrying the design loads even with the presence of weld discrepancies.

3. Conclusion The results of the supplementary evaluations complement the results of the Reinspection Program and give a total of 356 weld maps of discrepant welds which have been evaluated (50 randomly selected weld maps and 50

5 11- 6 weld maps containing the most weld discrepancies from the Reinspection

-Program; 69. weld maps from highly stressed cable tray support welds; and

- 187 weld maps for highly stressed welds for weld inspecto.s not included in the Reinspection Program). These evaluations, which revealed no design significance, result in a reliability of better than 99% which is consistent with the previous conclusions reached concerning the quality of Hatfield Electric's work.

4. Additional Inspections and Evaluations As noted previously, none of the weld discrepancies in the Reinspection Program or in the supplemental inspections and evaluations described herein impair the structural integrity of any structure or component.

However, there were three types of discrepancies which resulted in a considerable reduction in load-carrying capacity. Even though these conditions were found to be acceptable for the highly stressed elements reviewed in the program, additional inspections and evaluations were performed to provide assurance of the adequacy of the entire plant. The three types of discrepancies for which additional inspections were undertaken are categorized as follows:

e Conduit support weldments e Cable tray support connections with fit-up gap e Cable tray support internal diagonal member connection

a. Conduit Support Weldment The Reinspection Program identified two cases where a portion of the

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weld was omitted from a weldment for a conduit support connection.

The weldment consisted of four individual welds of which two welds were omitted. In order to assess the effect of su'ch an omission

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anywhere in the plant, a sampling plan was developed to inspect this type of weldment. A randomly selected sample of 489 of these weldments out of an approximate total population of 3,000 were examined to determine if all required welds had been made. In this examination, two supports were identified where the specified welds had been omitted. Based on the as-built conditions of these supports, an evaluation wa= made and it was determined that the conduit loads could be accommodated by the discrepant supports or by redistribution of loading to adjacent supports. Therefore, it has been demonstrated, with greater than 99% reliability at a 95% confidence level, that the

, structural integrity of the conduit system is adequate.

These favorable engineering evaluation results are due to the fact that the original conduit and conduit support design have design margins.

Conduit supports are generally spaced closer than the maximum conduit span requirements because of physical limitations in the plant.

Furthermore, the supports are initially selected from typical details.

The typical details are designed using peak seismic responses for a given area of the plant. Support selection is also based on loads which assume maximum cable loads in each conduit. When individual supports are reviewed using actual cable loads and more exact seismic analysis, there is sufficient design margin available to accommodate the weld discrepancy.

b. Cable Tray Support Connections with Fit-Up Cap The supplemental Hatfield Electric inspections identified recurring cases of welds with a fit-up gap. The engineering evaluations of these discrepancies conservatively assumed a considerable reduction in the load-carrying capacities of these connections. To assess the actual effect on weld capacity due to a fit-up gap, a supplemental test program was established. Ten fillet welded specimens with representative fit-up gap were prepared using the applicable Hatfield

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SII-8 Electric weld procedure. These specimens were strength tested, and the test results indicated that there-was no reduction in strength of

the weld due to the fit-up gap. Therefore, it was concluded that the

. fit-up gap that was identified in the_ Reinspection Program bad no effect on the capacity of similar cable tray connections in the plant.

c. Cable Tray Support Internal Diagonal Member Connection In the Reinspection Program and the supplemental Hatfield inspections, some of the connections for cable tray support diagonal member connections did not conform to the design configuration. In the worst case, a partial penetration weld was used instead of the specified fillet weld. The engineering evaluation of this case assumed that this diagonal did not carry any load and demonstrated that the support could still accommodate the design loads. Although the support was adequate, in order to address the effect of this type of discrepancy on the entire plant, the actual strength of this weld was investigated. The diagonal member with the welds in question was removed from the cable tray support and cross-sections of the welds were macroetched to determine the depth of weld penetration. Based on the results of this supplemental test, it was determined that the as-built welds had less than a 10% reduction in capacity from that calculated for the original fillet welds. Therefore, this type of discrepancy has no design significance and can be accepted for other such cases in the plant.

C. PITTSBURGH TESTING The supplemental evaluations and inspections completed for Pittsburgh Testing show that: (1) highly stressed welds inspected by Pittsburgh Testing are capable of carrying the design loads and (2) weld discrepancies involving overlap do not mask other discontinuities or reduce the weld capacity.

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1. Highly Stressed Welds This evaluation considered the highly stressed connection welds from the entire population of welds inspected by Pittsburgh Testing with weld discrepancies in the Reinspection Program.

The cesign margin for each of the 905 welds shown in Table C-1 of Appendix C of the Reinspection Program Report was determined using the design loads and weld properties. Forty-three highly stressed welds were identified, and detailed weld map were prepared showing all weld discrepancies. The results of the evaluations for the discrepant welds in the highly stressed connections are shown in Table SCE-II.

Table SCE-II Results of AWS Weld Discrepancy Evaluation for Highly Stressed Welds Inspected by Pittsburgh Testing Weld Discrepancy Category A B1 B2 C Weld Weld No Strength Strength Weld No. of Weld Structural Reduced Reduced Rejected Discrepancies impact by < 10% by 210% (Cracks) 0 28 15 0 43

• Note: The format of this table corresponds to Table CE 11 in Exhibit C-2 of Appendix C of the Reinspection Program Report.

The results of the engineering evaluation showed that each weld is capable of carrying its design load. The results of this evaluation complement the results of the Reinspection Program and give a total of 107 weld maps of discrepant welds inspected by Pittsburgh Testing which have been

S 11- 1 0 evaluated (14 randomly selected weld maps and 50 weld maps containing the most weld discrepancies and 43 highly stressed welds). None of the discrepancies had design significance.

2. Welds with Overlap These supplemental inspections were initiated to address Pittsburgh Testing's failure rate for the inspection of welds with overlap. The presence of overlap may make visual weld quality inspection more difficult since overlap can mask other discontinuities. The third-party inspector identified the 51 welds from the 905 weld discrepancies which had the most severe cases of overlap. The overlapped portion of these welds was removed by grinding and the weld was then reinspected. In all cases, the remaining weld was at least the size specified by the design.

These welds revealed no other discrepancies.

Because it was found after grinding that no other discontinuities were masked by overlap and that the weld size remained within the specified limit, it is concluded that the amount of overlap present on welds inspected by Pittsburgh Testing has no impact on the capacity of the we!ds.

5 111 - 1 III. SUPPLEMENTAL INSPECTIONS AND EVALUATIONS FOR OBJECTIVE ATTRIBUTES FOR HATFIELD ELECTRIC A. INTRODUCTION Appendix D to the Reinspection Program Report included commitments to do additional inspections for Hatfield Electric objective attributes where the sample size was not statistically significant. These supplemental inspections are described in Note 5 to Table DE-5, in Exhibit D-1 of Appendix D of the Reinspection Program Report, and include equipment setting, equipment modifications, A325 bolting, and conduit support botting.

B. EQUIPMENT SETTING The work reinspected at part of the Reinspection Program did not include any reinspection of equipment setting. In order to complete the data base, the setting of 50 randomly selected pieces of safety-related electrical equipment from a total population of approximately 250 have been reinspected. A total of 778 items were inspected and 34 discrepancies were identified. An evaluation was made to determine whether or not the observed discrepancies have any design significance. The result of this evaluation is that none of the observed discrepancies has design significance. The majority of the discrepancies consist of equipment anchoring details with weld length and weld spacing deviations. 'Ihe equipment anchoring details were determined to be adequate because of the conservatism which was used in the determination of design anchorage ioads.

The only deviation which resulted in a significant reduction of strength was a hold-down weld detail for 4160 volt switchgear. In this detail, welds on the two short sides of a four-sided weld were omitted. In order to evaluate the overall effect of this discrepancy it was assumed that all of the 4160 voit switchgear had this discrepancy. Because of the conservatism in the original equipment anchorage loads, it was determined that the as-built condition was adequate to support the required loads.

Sill-2 A few discrepancies involved discontinuities in the equipment grounding connection. The discontinuities were determined to be acceptable because of the presence of an alternate grounding connection in each case.

C. EQUIPMENT MODIFICATION The work reinspected as part of the Reinspection Program included reinspection of 27 items associated with equipment modification. This sample was too small to permit meaningful reliability calculations. In order to expand the data base, an additional random teple of 50 pieces of safety-related electrical equipment out of a total population of 250 have been reinspected. Equipment modification work is, in large part, not recreatable. Several modifications may be made to the same equipment. A subsequent modification may alter a previous modification.

Modifications may be made by the electrical contractor, the equipment supplier, Commonwealth Edison Operational Analysis Department, or Commonwealth Edison Byron Station personnel.

To accomplish the supplemental reinspection of equipment modification, a 100%

wiring inspection was made. A total of 1,850 items covering a considerably larger number of inspection points were inspected and 44 discrepancies were identified.

An evaluation was made to determine whether or not the observed discrepancies had any design significance. The result of the evaluation is that ncne of the observed discrepancies has design significance. The discrepancies are primarily minor wiring variations that do not affect the functioning of the equipment.

D. A325 BOLTING in the Reinspection Program only eight cases of A325 bolting in electrical supports were reinspected. In order to expand this data base, an additional random sample of 51 supports out of a total population of 169 supports using A325 bolted connections were reinspected. The engineering evaluation established an acceptance criteria taking into account bolt relaxation and measurement accuracy. Of the 295 bolts which were reinspected on these supports,46 bolts did

Sill-3 not meet this acceptance criteria. The design of the associated connections was reviewed, and it was determined that these connections are adequate as bearing rather than friction type connections. Although these discrepancies have no design significance, because of the number of discrepancies found, a retorquing of all Hatfield A325 botting installation has been initiated. Any discrepant conditions will be corrected.

E. CONDUlT SUPPORT BOLTING The work reinspected as part of the Reinspection Program did not include checking the torque level of conduit support bolting. Conduit support bolt torque was deemed not recreatable because it could not be associated with an individual inspector. In order to resolve questions concerning conduit support botting, 305 randomly selected supports were reinspected from a total of approximately 25,000. A total of 1,008 bolts were inspected. Torque values were recorded for any bolt with torque less than the minimum installation criteria. The engineering evaluation established an acceptance criteria taking into account bolt relaxation and measurement accuracy. Thirty-four bolts did not meet this acceptance criteria. These conditions were evaluated and found to have no design significance because the loads would be carried by the adjacent supports.

In this process of inspecting conduit support bolt torques, two clamps with four bolts were found missing. Based on our concern for missing clamps and bolts, a walkdown of the critical clamps was undertaken. A critical clamp is typically located where a conduit terminates. There were 8,532 cases included in this initial walkdown and ten cases were found with missing bolts or clamps. The walkdown of the remaining accessible conduit is continuing to ensure that conduit clamps and bolts are in place. Any missing bolts or clamps will be restored.

Sill-4 F. CONCLUSION The supplemental inspections and evaluations which have been conducted for

- Hatfield Electric objective attributes confirra the adequacy of the quality of work.

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