ML20038A667

Responds to IE Bulletin 81-01, Surveillance of Mechanical Snubbers. Problems W/Three Snubbers Were Resolved W/O Replacement.Sixteen Snubbers Were Repaired or Replaced & Reinspected

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

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October 20, 1981

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Mr. R. H. Engelken, Director N' -

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1450 Maria Lane, Suite 210 L cdN[v 49g'4 Walnut Creek, CA 94596 C "e f;g't Re: Docket No. 50-275 N'(<,\, h Diablo Canyon Unit 1 N'Q/ 4-; 6 b, f

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 l 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 p ,

[\ . 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 MODEL j QUANTITIES 350 25 PSA-1/4 (NF)*

250 288 PSA-1/4 (PRE-NF) 650 18 PSA-1/2 (NF) 500 67 PSA-1/2 (PRE-NF) 1500 62 PSA-1 (NF) ,

1000 65 PSA-1 (PRE-NF) 6000 86 PSA-3 (NF) 3000 56 PSA-3 (PRE-NF) 15,000 4 PSA-10 (NF) 10,000 29 PSA-10 (PRE-NF) 50,000 10 PSA-35 (NF) 50,000 2 PSA-35 (PRE-NF) 120,000 5 PSA-100 (NF)

PSA-100 (PRE-NF) 100,000 1 718 TOTAL l

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TABLE 2 StMMARY OF SfiUBBFRS REPAIRED BY PSA PROBABLE CORRECTIVE SERIAL LOCATION CAllSE OF FAILURE ACTION ITEM MFG-MODEL NO. MODE OF FAllllRE Snubber ends rotated in Damaged parts were 22-315SL 1 PSA-1/4 185 frozen due to twisted Rod & Bearing Assy. & opposite directions replaced.

(PRE-NF) bent screw shaft. during installation.

I:aplaced damaged 22-395L 2 PSA-1/4 249 Stroke limited to 2 inches Damaged by unrelated due to two dents on outer construction activity. outer tube.

(PRE-NF) tube. ___

Snubber ends rotated Replaced damaged 22-10SL 3 PSA-1/4 341 frozen due to bent Rod &

(PRE-NF) Brg. Assy. during installation. parts.

Snubber ends rotated Replaced damaged 16-25SL 4 PSA-1/4 353 frozen due to bent Rod

& Brg. Assy. & bent Screw during installation. parts.

(PRE-NF)

Shaft.

frozen due to damaged Snubber ends rotated Replaced damaged 22-275l 5 PSA-1/4 356 (PRE-NF) anti-rotation key, bent during installation. parts.

screw shaft & rust.

394 NA. Snubber was operable. Unknown Replaced outer tube.12-110SL 6 PSA-1/4 (PRE-NF) indicator tube flared.

Rod pulled out of Brg. Snubber ends rotated Replaced damaged 10-75SL 7 PSA-1/4 399 (PRE-NF) Bent screw shart. Damaged during installation / parts, I

anti-rotation key, subsequent load applied.

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Snubber ends rotated Replaced damaged 22-276SL 8 PSA-1/4 444 Frozen due to bent Rod &

(PRE-NF) Brg. Assy., bent Screw during installation. parts-Shaft & damaged Anti-Rotation key. ,

734 frozen due to bent Rod & Snobber ends rotated Replaced damaged 22-2185L 9 PSA-1/4 damaged parts.

(PRE-NF) Brg. Assy., bent Screw during installation.

Shaft, damage to Torque Carrier & Capstan Spring.

1ABLE 2 (Continued) 1-S1MfiARY OF StillBBERS REPAIRED BY PSA .

PR0llABI E CORRECTlVE SERIAL ACT10N LOCATION MFG-MODEL f10. MODE OF FAltllRE CAllSE Of FAltllRE ITEM Snubber struck with a Replaced Screw 22-240SL 10 PSA-1/4 761 Frozen due to bent screw Shaft & Capstan shaft. blow such as dropping (PRE-NF) Spring.

prior to installation.

Possibly subjected to Replaced Insert 22-301SL PSA-1/4 1035 lli drag force due to 11 brinnelling of bearing sharp impact load during Bearing.

(PRE-NF) handling or installation.

insert.

Subjected to sharp impact Replaced damaged 12-84SL 12 PSA-1/4 1373 ili drag force due to bent screw shaft and arc load. Welding arc had parts.

(NF) passed thru unit.

strike.

Snubber ends rotated Replaced Rod & Brg. 12-22SL 13 PSA-1/2 110 Frozen due to a bent Rod

& Bearing Assy. during installation. Assy.

(PRE-NF)

Forcing pin into place Replaced spherical 10-91SL 14 PSA-1 127 Eye Bearing frozen.

during installation, brg.

(PRE-NF) forcing pin into place Replaced spherical 10-30SL 15 PSA-3 412 Spherical Bearing pushed out of position. during installation. brg.

(PRE-NF)

Rust present throughout floisture intrusion. Replaced entire unit, 4-175L 16 PSA-3 986 snubber. Beyond economical (NF) repair.

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