ML19247A615
| ML19247A615 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 07/26/1979 |
| From: | Broehl D PORTLAND GENERAL ELECTRIC CO. |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7908010492 | |
| Download: ML19247A615 (4) | |
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July 26, 1979 Trojan Nuclear Plant Docket 30-344 License WPF-1 Director of Nuclear Reactor Regulation ATTN:
Mr. A. Schwencer, Chief Operating Reactors Branch #1 Division of Operating Reactors U.S. Nuclear Regulatory Commission Washington, D. C. 20555
Dear Sir:
In your letter of June 15, 1979l you requested additional information on three items relating to the Trojan Nuclear Plant Containment Tendon Surveillance Program. Our response to Ite_2 1 and 2 are attached per the requested schedule. The response to Ites 3 will follow with our upcoming revision to License Change Application 15.
Sincerely, c:
H.. Lynn Frank, Director State of Oregon Depsrtment of Energy Mr. 3. H. rugelken, Director 490 315 Nuclear Regulatory Comaission Region V
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PORTLAND GENERAL ELECTRIC RESPONSE TO NRC COMMENTS Item 1 - Response to NRC Comment No. 1 As stated in our letter of April 25, 1979, the intended exclusion of surveillance tendons which anchor on the north face of the 240' buttress above the main stream relief valves is based on personnel safety considerations. During plant operation, surveillance personnel could be subjected to ateam and extreme noise if actuation of the relief valves were to occur while tendons passing through the 0* to 120* sector between Elevations 126'-8" and 168'-11" were being inspected.
It should be noted that the tendons anchored on the north face of the 240* buttress do not pass through the sector of the Containnent adjacent to the relief valves.
Both horizcntal and vertical tendons which traverse the sector adjacent to the main steam line relief valves have been covered in the tendon sample population for surveillance operations performed. To date, seven hoop tendons above the relief valves and three inverted U tendons in the vicintly of the relief valves have been inspected in the surveillance programs with acceptable results.
In addition, the Containment concrete above the exhaust s*acks has been visually inspected with the aid of binoculars, and no evidence of concrete surface degradation was detected.
The absence of any visually detectable deg adation of the Containment, together with successful testing of tendons passing above the exhaust stacks leads to the conclusion that the conditions of tendons excluded from surveillance are adequately represented by the tendons that have been inspected.
As stated in our inital response, we believe that the selected surveillance tendons provide a reasonably random and represencative sampling of tendon performance throughout the Containment for the surveillance time in te rval. We also consider that the intent of regulatory position C.2.4 t.as b.en met.
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Page Two Item 2 - Response to NRC Comment No. 2 As reported on Page 5-1 of the report, all 13 tendons were inspected for discontinuous or missing wires. Wire-by-wire continuity checks were made on all wires for eight of the tendons. This method of observing movement of the individual wire at the end opposite to the ead being moved provides positive assurance that all discontinuous wires are detected.
For five of the 13 tendons, the inspection was made by visual otser'. tion during complete tendon relaxation and during efforts to move the stressing washer. We also believe that visual observation of the tendon daring complete detensioning, without moving individual wires, provides reasonable assurance that all discontinuous wires are detected.
Both the Trojan surveillance experience and Bechtel experience on other surveillances indicate that discontinous wires are visually detected during the detensioning operations.
As shown in Table 6.1 of the report, a total of 2,333 wires, out of a possible 2,340 wires, for the 13 surveillance tendons were determined to be effective during the retensioning stage of the surveillance.
Of the seven missing or discontinuous w;res, two wires (one each from V126 and 32H014) were removed for surveillance test eamples, and two wires were docuum.ced as misri'g in the original quality control records (one each f roc V110 and V201).
The discontinuous wire documented during this surveillance in tendon 32H023 is very likely the same wire 1 sted as kinked in the original quality control records, since 179 wires in this tendon were determined to be Ef fective both originally and during the first y3ar surveillance.
- Finally, both the wire not buttonheaded and the protruding wire in tendon 21H109 appear to have been installed that way initially, although not listed as such in the original quality control documentation.
In summary, the results indicate that only two wires were discovered to be inef fective which were not so listed in the original quality control documentation, and even these two appear to be unchanged since initial installation. Hence, all of the apparent originally ef fective wires in the 13 tendons remained effective during the surveillance time interval.
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Page Three The integrity of tensions, for which the stressing washers could not be moved, Las not been compromised.
Loads applied to the stressing washers in an attempt to move them were not recorded, but were applied with equipment considered standard and were not of a magnitude which would cause damage to the stressing washers or to the tendon wires.
The reason the stressing washers could not be moved was not specifically determined during the surveillance. A possible reason could be a alight bindir.g of wires with the washer due to misalignment of individual wires from their position in the tendon to their position in the stressing washer.
Another possib.e reason could be a small amount of local yuiding of the stressing washer at the interface with the buttonhead. Neither of these conditions would deg aae the capacity of the tendons.
490 7a18 MRG/3rg55.23A20