ML17296A673
| ML17296A673 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 03/05/1980 |
| From: | ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | |
| Shared Package | |
| ML17296A669 | List: |
| References | |
| NUDOCS 8004070258 | |
| Download: ML17296A673 (6) | |
Text
REPORTABLE DEFICIENCY 50.55 (e)
ARIZONA PUBLIC SERVICE COMPANY (APS)
PVNGS UNIT i/I Harch 5, 1980 I.
~Pur ose The purpose of this report is to provide the information required by 10CFR50.55(e) concerning deficient welds on safety-related (Quality Class Q) pipe hanger assemblies.
These pipe hangers were installed in Palo Ver'de Nuclear Generating Station, Unit }/1, with certain fillet welds not in conformance with project drawings.
As the result of a joint APS/Bechtel unscheduled
- audit, completed on June 29, 1979, of installed pipe hangers in Unit /!1, it was determined that out of the forty-seven
., (47) pipe hangers installed and inspected, some seventeen (17) were found to have fillet welds that were 1/16" too small in width and up to 3/4" short as required 'by the design drawings.
A Corrective Action Request (CAR), UA-79-S-35A, and three (3) Nonconformance Reports (NCR's), P-A-566, 567 and 568, were written to initiate appropriate action and to identify the discrepant welds requiring Engineering disposition and reinspection.
In addition, a Deficiency Evaluation Report (DER) was initiated to evaluate these
-deficiencies to determine if they were reportable under the requirements of 10CFR50.55(e).
A review of the information at this time indicated that this noncompliance did not represent a safety significant situation.
- However, on January 31,
- 1980, APS was informed that during the final resolution of NCR P-A-566, an analysis on some of the subject welds indicated in certain cases; (1) that weld failures could have occurred if the unacceptable welds were not corrected, (2) that pipe support weld failure could potentially have caused a safety-related piping system failure, and (3) this sequence of events could have resulted in a significant safety event.
III.
Descri tion of Deficienc The inspection and audit of these pipe hanger assemblies determined that some fillet welds were up to 1/16" under-sized and were up to 3/4" too short.
Some of the welds were improperly placed and some welds had excessive weld slag and spatter.
IV.
Cause of the Deficienc The cause of the deficiency can be attributed to (1) a visual acceptance of weld lengths and fillet size rather than dimensional inspection with inspection tools, (2) unclear understanding of the miscellaneous steel weld symbol drawing, (3) insufficient inspection by suppliers, and (4) the lack of appropriate inspection before instal-lation.
V.
Anal sis of Safet Im lications
'k Due to the many combinations of configurations of the pipe supports involved in the original nonconformance and subse-quent nonconformances identified, a safety evaluation has not been performed on each pipe hanger assembly.
- However, specific analysis on some of the pipe supports determined that (1) weld failures could have occurred under the maxi-mum possible load conditions if the unacceptable welds were not corrected, (2) the subsequent pipe support failure could potentially have caused a safety-related piping system fail-
- ure, and (3) this'sequence of events could have resulted in a safety significant event.
VI.
Corrective Action A complete reinspection program of safety-related pipe hanger assemblies was initiated.
The deficiencies dis-covered have been and are being documented on Nonconfor-mance Reports and appropriately dispositioned to assure conformance with design requirements.
The disposition of these NCR's consisted of an Engineering analysis of each individual supports as required.
The criteria for accep-tance of the nonconforming welds was whether the "as-built" weld stress allowable was adequate to meet the design loads.
If acceptable, the weld was accepted "as-is". If not, the welds are repaired per the original design requirement.
Training sessions covering inspection and acceptance criteria were held with the piping and welding field engineers and
ta
the quality control personnel.
Changes to the Woik Plan and Procedures/Quality Control Instruction were made to include the inspection of welds made in the field, as well as the welds made in the suppliers'hop.
Fillet weld gauges have been supplied to pipe support field engineers and weld quality control engineers so that weld inspection can be accomplished by physical measurement.
Written instructions have been given to appropriate Supplier Quality Represe'ntatives and Area Supervisors reiterating the necessity to increase surveillance activities or in-process and final inspection of pipe support assemblies at supplier shops.
The suppliers, Pul'lman Power Products and Harathon Steel, have (1) initiated additional training to their shop super-vision and quality control personnel, (2) emphasized proper inspection methods and measurement criteria of pipe support assemblies, (3) issued'illet weld gauges and instructions for their use, and (4) increased surveillances of their 100%
inspection program.
APS/Bechtel meetings were held November 29 and December 20, 1979 with appropriate Quality Assurance and Supplier Quality personnel to follow-up on certain actions, including supplier
" performance.
A Bechtel audit was conducted January 29, 1980 by Quality Assurance to verify that Bechtel Supplier Quality Repre-sentatives and the suppliers have adequately implemented their corrective action.
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