ML20032B896
| ML20032B896 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 10/23/1981 |
| From: | Sargent C COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20032B893 | List: |
| References | |
| NUDOCS 8111060493 | |
| Download: ML20032B896 (7) | |
Text
/nN Commonwe:lth Edison
) One Fast National Plaza. Chicago, lilinois (Q Chicago, Illinois 60690 7 Address Rep!y to: Post Office Box 767 v
October 23, 1981 Mr. James G. Keppler, Director Directorate of Inspection and Enforcement - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137
Subject:
Response to Mr.
I.
T.
Yin's Questions on Large Bore Hangers
Dear Mr. Keppler:
The purpose of this letter is to provide Commonwealth Edison Company's response to Mr.
I. Yin's questions concerning the adequacy of Morrison Construction Co. Q.C.
inspections performed on large bore hangers.
It is our understanding that this information will be included in the inspection report ano that no further response may be required for this issue.
In response to the questions, the Project Construction Department initiated a reinspection program.
These reinspections were performed by Morrison Construction Co. Q.C.
inspectors.
This activity was monitored by CECO. Q.A. Department concurrently and independently from the MCCo. Q.C inspections to insure the accuracy of the reinspection program.
The independent Q.A. check wa s com-pared with the inspection results o f MCCo. Q. A.
Based on this type o f review, we are confident in the accuracy of the reinspections performed both inside and outside the suppression pool.
Samples were taken from inside and outside the suppression pool and are as follows:
1.
All 162 safety related large bore hangers inside the Unit 1 suppression pool were reinspected.
- 2. A sample of 119 safety-related large bore hangers outside of the suppression pool in the Unit 1 drywell and Reactor Building were reinspected.
The results of reinspection of the above samples individu-ally and combined have been tabulated into the following four categories.
- 1. Hanger was elected in accordance with the design drawing.
8111060493 e gDR ADOCK 05dochf3 0tz g 6 $$
Mr. J. G. Keppler October 23, 1981 II. Hanger has minor discrepancies with the design drawing which would not affect its load carrying ability.
III. Hanger has discrepancies which were submitted to the AE for formal re-review and determined to be acceptable for carrying the required hanger design load.
IV. Hangers with discrepancies which have been reviewed by the AE and found to be unacceptable for carrying the required hanger design load.
Attachment B combines and summarizes the results of both inspection programs.
As indicated, 4.9% of the total hangers had minor discrepancies which would not affect the load carrying capability of the hanger.
Examples of this type of discrepancy would be:
- 1. Variations from standard work practice, such as tightening of nuts.
- 2. Missing washer plates.
- 3. Gaps at ball bushings larger than installation tolerance, but less than the maximum valve given to the designer by the manufacturer.
In addition, 6.4% of the total hangers were submitted to the Architect and Engineer for formal review and calculations.
Examples of the type of problems submitted to the AE for review would be:
- 1. Welds slightly undersized or not the total length specified on the design drawing.
- 2. Hanger components which had minor deviations from the weight per foot or dimensions of the specified member.
- 3. Welding which did not comply with the welding detail as specified on the design drawing.
- 4. Hangers that were missing a single item, such as a stiffner, which was specified on the design drawing.
Based on the AE review of the discrepancies identified, no hangers were deficient to an extent that prevented the hanger from carrying its analyzed design load.
The results of this review are tabulated as Item S, Exhibit B.
Since each hanger has a large number of inspection points, the relatively small number of discrepancies do not indicate a major breakdown in the contractors inspection program.
In addition, the engineering review of the more serious discrepancies has substanti-ated the position that no hanger would fail due to these discrepan-cies when subjected to the design loads.
Although we believe steps should be taken to improve the contractors Q.C.
inspection program, we do not believe the deficiencies, if left undetected, institute a major concern.
J. G. Keppler October 23, 1981 It may be interesting to compare the results of this sample program if it had been conducted on a statistical analysis basis.
(The sample program conducted cannot qualify because of sample size requirements for random selection, and similar preprogram qualifica-tions.)
Utilizing a statistical review based on Military Standard 105-D and a Sargent & Lundy recommended requirements of a 95%
confidence level, and a 95% reliability level, the required sample size would be 240 hangers ( Al less than actually sampled).
To achieve the 95% levels, no more than 6 hangers could be proven to have problems which resulted in reducing the hanger capability below that required to support the design loads.
Based on the fact that no hangers fall into this category, the large bore sample program would appear to have easily surpassed the 95% confidence level and 95% reliability level.
Based on the review of the deficienices noted as a result o f the sample reinspection program, we are confident that we do not have a significant problem.
However, we do agree that our future inspection efforts should be upgraded to achieve the highest level of confidence and reliability attainable.
I CORRECTIVE ACTION In order to upgrade the Q.C. hanger inspection program, the following 5 steps will be taken.
1.
The discrepancies noted during the reinspection program will be documented on MCCo. nonconformance reports.
The disposition will be one of the following:
a)
Minor rework of the hanger to comply with the l
design drawing.
l b)
Revision of the design drawings to reflect the as-installed hanger condition where i
determined appropriate during the Sargent &
Lundy review.
- 2. Morrison inspection and erection supervisory personnel will be retrained.
This retraining will address all hanger erection and inspection criteria.
To improve the ef fectiveness of the training, detailed flow charts will be utllized detailing interrelationships between procedures, inspections, and the Morrison Q.A. manual.
Additional emphasis will be placed on documenting minor discrepancies and generic problems discovered during hanger inspections.
This retraining will be completed by November 2, 1981.
- 3. Morrison will develop and implement a work instruction to clarify inspection and documentation requirements contained in their hanger inspection form.
The issuance of this work instruction and associated training will be completed by November 2, 1981.
J. G. Keppler October 23, 1981 4.
Morrison will modify their line walk package assembly process so that inspectors performing future line walks will also be required to document current correctness of past Q.C. inspections or reperform the total detailed hanger inspection.
This will provide a complete review of the hanger installation at the time of line walk.
This program will be implemented on October 26, 1981.
5.
In addition to the corrective actions taken by Morrison, Commonwealth Edison will increase their Quality Assurance coverage of Morrison Quality Control inspection activities.
Site Quality Assurance will insure the following:
a)
That the re-training to be provided tc Morrison production and quality control personnel is adequate and consistent with identified objectives.
b)
Acceptable close-out of each identified deficiency during the course of the recently concluded support / restraint reinspection effort.
Also, CECO. Quality Assurance will increase its surveillance of Morrison's Q.C. inspections of support /
restraints and Q.C.
final line walk activities.
This coverage by Ccco. Quality Assurance will be maintained until a sufficient confidence level had been established in the completeness of MCCo. Q.C. Inspections.
If there are any questions in this regard, please direct them to this office.
Very truly yours, (b
C. E.
Sargent Nuclear Licensing Administrator cc:
NRC Resident Inspectnr 1m Attachmente 2731N
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ATTACHMENT A-1 INSPECTION
SUMMARY
UNIT #1 SUPPRESSION POOL I.
Number of Large Bore Hangers Inspected.
162 (All Large Bore Suppression Pool Hangers)
II.
Number of Large Bore Hangers erected in 139 accordance with the design drawings.
III.
Number of Large Bore Hangers having minor 12(1) discrepancies with the design drawing which would not affect hanger load carrying capability.
IV.
Number of Large Bore Hangers having 11 discrepancies which were submitted to the AE for formal review ano determined to be acceptable for carrying the required hanger cesign load i
V.
Hangers with discrepancies which have been 0
reviewed by the AE and found to be unacceptable for carrying the required hanger design load.
f i
L f
i i
i (1)
Seven similar hangers, designed for same service, were determineo to have identical washer problem.
Tnese were i
determined to be acceptable based on previous AE review.
2731N I
i ATTACHMENT A-2 INSPECTION
SUMMARY
UNIT #1 OUTSIDE SUPPRESSION PGOL I.
Number of Large. Bore Hangers Inspected 119 II.
Number of Large Bore Hangers erected in 110 accordance with the design drawing.
III.
Number of Large Bore Hangers having minor 6(1) discrepancies with the design drawing which l
would not affect hanger load carrying capability.
IV.
Number of Large Bore Hangers having discre-3 pancies which were submitted to the AE for formal review and determined to be acceptable for carrying the required hanger design load.
V.
Hangers with discrepancies which have been 0
reviewed by the AE and found to be unacceptable for carrying the required hanger design load.
(1) 2 hangers were determined to have acceptable gaps at ball bushings based on previous AE review.
2731N
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ATTACHMENT B INSPECTION
SUMMARY
UNIT #1 SUPPRESSION POOL AND UNIT #1 OUTSIDE SUPPRESSION POOL I.
Number of Large Bore Hangers Inspected 281 II.
Number of Large Bore Hangers erected in 249 accordance with the design drawing.
III.
Number of Large Bore Hangers having minor 81 discrepancies with the design drawing which would not af fect the hanger load carrying capability.
IV.
Number of Large Bore Hangers having discre-14 pancies which were submitted to the AE for formal review and determined to be acceptable for carrying the hanger design load.
V.
Hangers with discrepancies which have been 0
reviewed by the AE and found to be unacceptable for carrying the hanger design load.
2731N m
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