ML20038A667
| ML20038A667 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 10/20/1981 |
| From: | Crane P, Schuyler J PACIFIC GAS & ELECTRIC CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| 8111020, IEB-81-01, IEB-81-1, NUDOCS 8111160138 | |
| Download: ML20038A667 (6) | |
Text
Docke t I:o. 50-?75 nullet in I!o. E1-01 PACIFIC GAS AND E LE C T RIC CCMPANY 7 ' 6'sLC 7 :. F F T,
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October 20, 1981 f.
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q Mr. R. H. Engelken, Director 3
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U. S. Nuclear Regulatory Commission
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Docket No. 50-275 N'Q/ 4-; 6 b, f Diablo Canyon Unit 1
Dear Mr. Engelken:
Our letter to yor dated September 8, 1981 reported the completion of the inspection and testing of all (708 in total) safety-related mechanical snubbers. Sicce then ten new snubbers were added (total now 718) and, after related w rk by a contractor, a number of additional snubbers were reinspected. This letter transmits the final report and completes the requirecrents of IE Bulletin 81-01.
I am authorized to sign ara file this submittal with the NRC, and the matters set forth herein are true and correct to the best of my knowledge and belief.
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I Mr. R. H. Engelken October 20, 1981 Approximately 2400 manhours were expended in preparing this response.
Very tr'ly
- urs, J.
SCHUYLER Subscribed and sworn to before me this 20th day of October, 1981 6SPAL)
'Theodora Cooke, Notary Public in and for the City and County of San Francisco, State of California My Commission expires January 28, 1985 Robert Ohlbach Philip A. Crane, Jr.
Attorneys for Pacific Gas and Electric Company c
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t Phi ip AT/CP'ane, Jr.
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Attachments cc: Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission h shington, D. C. 20555 Service List (w/ attachment)
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DEPARTMENT OF NUCLEAR PLANT OPERATIONS DIABLO CANYON POWER PLANT i
Results of Inspection Required by IE Bulletin 81-01 CISCUSSION:
US NRC IE Bulletin No. 81-01 required that all mechanical snub-bers installed on safety-related systems at the Diablo Canyon Unit 1 Power Plant be visually examined and tested according to the Bulletin's requirements.
Each snubber was visually examined for damage and manually stroked over its full range in both compression and tension. The proce-dure involved removing either one bracket pin or the transition tube-to-snubber bolting in order to stroke each snubber. Following stroking, the bracket pin was carefully replaced or transition tube-tc-soulber bolting was reinstalled, retorqued and safety wired as applicable. The results of this inspection / stroking are individually documented for each snubber and filed in each snubber's equipment history jacket on file with the Maintenance Department at DCPP.
Table I summarizes all mechanical snubbers inspected. Nineteen reports were written identifying problems with individual snubbers that could not be easily resolved without replacement. Three of the above problems have been resolved without replacement. The remaining sixteen snubbers were repaired or replaced and reinspected.
Table 2 is a summary of the comprehensive report submitted to PGandE by Pacific Scientific Company on the work done on the sixteen snubbers repaired or replaced.
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TABLE 1 MECHANICAL SNUBBERS INSPECTED IN UNIT 1 Manufacturer & Supplier: PACIFIC SCIENTIFIC COMPANY j
QUANTITIES MODEL PSA-1/4 (NF)*
350 25 PSA-1/4 (PRE-NF) 250 288 PSA-1/2 (NF) 650 18 PSA-1/2 (PRE-NF) 500 67 PSA-1 (NF) 1500 62 PSA-1 (PRE-NF) 1000 65 PSA-3 (NF) 6000 86 PSA-3 (PRE-NF) 3000 56 4
PSA-10 (NF) 15,000 PSA-10 (PRE-NF) 10,000 29 PSA-35 (NF) 50,000 10 PSA-35 (PRE-NF) 50,000 2
PSA-100 (NF) 120,000 5
PSA-100 (PRE-NF) 100,000 1
718 TOTAL l
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TABLE 2 StMMARY OF SfiUBBFRS REPAIRED BY PSA SERIAL PROBABLE CORRECTIVE ITEM MFG-MODEL NO.
MODE OF FAllllRE CAllSE OF FAILURE ACTION LOCATION 1
PSA-1/4 185 frozen due to twisted Snubber ends rotated in Damaged parts were 22-315SL (PRE-NF)
Rod & Bearing Assy. &
opposite directions replaced.
bent screw shaft.
during installation.
2 PSA-1/4 249 Stroke limited to 2 inches Damaged by unrelated I:aplaced damaged 22-395L (PRE-NF) due to two dents on outer construction activity.
outer tube.
tube.
3 PSA-1/4 341 frozen due to bent Rod &
Snubber ends rotated Replaced damaged 22-10SL (PRE-NF)
Brg. Assy.
during installation.
parts.
4 PSA-1/4 353 frozen due to bent Rod Snubber ends rotated Replaced damaged 16-25SL (PRE-NF)
& Brg. Assy. & bent Screw during installation.
parts.
Shaft.
5 PSA-1/4 356 frozen due to damaged Snubber ends rotated Replaced damaged 22-275l (PRE-NF) anti-rotation key, bent during installation.
parts.
screw shaft & rust.
6 PSA-1/4 394 NA.
Unknown Replaced outer tube.12-110SL (PRE-NF) indicator tube flared.
7 PSA-1/4 399 Rod pulled out of Brg.
Snubber ends rotated Replaced damaged 10-75SL (PRE-NF)
Bent screw shart. Damaged during installation /
- parts, I
anti-rotation key, subsequent load applied.
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8 PSA-1/4 444 Frozen due to bent Rod &
Snubber ends rotated Replaced damaged 22-276SL (PRE-NF)
Brg. Assy., bent Screw during installation.
parts-Shaft & damaged Anti-Rotation key.
9 PSA-1/4 734 frozen due to bent Rod &
Snobber ends rotated Replaced damaged 22-2185L (PRE-NF)
Brg. Assy., bent Screw during installation.
damaged parts.
Shaft, damage to Torque Carrier & Capstan Spring.
1ABLE 2 (Continued) 1-S1MfiARY OF StillBBERS REPAIRED BY PSA SERIAL PR0llABI E CORRECTlVE ITEM MFG-MODEL f10.
MODE OF FAltllRE CAllSE Of FAltllRE ACT10N LOCATION 10 PSA-1/4 761 Frozen due to bent screw Snubber struck with a Replaced Screw 22-240SL (PRE-NF) shaft.
blow such as dropping Shaft & Capstan prior to installation.
Spring.
11 PSA-1/4 1035 lli drag force due to Possibly subjected to Replaced Insert 22-301SL (PRE-NF) brinnelling of bearing sharp impact load during Bearing.
insert.
handling or installation.
12 PSA-1/4 1373 ili drag force due to Subjected to sharp impact Replaced damaged 12-84SL (NF) bent screw shaft and arc load. Welding arc had parts.
strike.
passed thru unit.
13 PSA-1/2 110 Frozen due to a bent Rod Snubber ends rotated Replaced Rod & Brg.
12-22SL (PRE-NF)
& Bearing Assy.
during installation.
Assy.
14 PSA-1 127 Eye Bearing frozen.
Forcing pin into place Replaced spherical 10-91SL (PRE-NF) during installation, brg.
15 PSA-3 412 Spherical Bearing pushed forcing pin into place Replaced spherical 10-30SL (PRE-NF) out of position.
during installation.
brg.
16 PSA-3 986 Rust present throughout floisture intrusion.
Replaced entire unit, 4-175L Beyond economical (NF) snubber.
repair.
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