ML20004E361

RO 81-018/03L-0:insp of safety-related Pipe Hangers Inside Containment Containing Mechanical Snubbers Revealed Snubbers Installed on Small Diameter Piping.Caused by Listing Not Including Review of Diameter Piping

ML20004E361
Person / Time
Site:	Millstone
Issue date:	06/05/1981
From:	Mroczka E NORTHEAST NUCLEAR ENERGY CO.
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
MP-2-4804, NUDOCS 8106120078
Download: ML20004E361 (9)

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June 5, 1981 MP-2-4804

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Mr. Boyce H. Grier f/d G G l! JUtl 11 ;gg4 1 Director, Region I - -

Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission

%>iu. D . W~ AU 631 Park Avenue ' Q'b /

King of Prussia, Pennsylvania 19406

Reference:

Facility Operating License No. DPR-65 .

Docket No. 50-336 Reportable Occurrence R0-50-336/81-018/3L-0

Dear Mr. Grier:

This letter forwards Licensee Event Report 81-018/3L-0 required to be submitted within thirty days pursuant to Millstone Unit 2 Appendix A Technical Specifications, Section 6.9.1.9.b, conditions leading to operation in a degraded mode permitted by a limiting condition for operation. An additional three copies of the report are enclosed.

Yours truly, NORTHEAST NUCLEAR ENERGY COMPAN

/ W E. . Mroczka Station Superintendent -

Millstone Nuclear Power Station EJM/SS:ws

Attachment:

LER 81-018/3L-0 cc: Director, Office of Inspection and Enforcement, Washir.gton, D. C. (30)

Director, Office of Management Information and Program Control, Washington, D. C. (3) ,

U. S. Nuclear Regulatory Commission, c/o Document Management Branch, Washington, D. C. 20555 81061200M S

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Page :1 of 2 ATTACHMENT TO LER #81-018/3L-0 Event description and probable consequences: i t

During a plant " Hot Standby" condition, dimensional inspection of safety related pipe hangers inside containment containing International Nuclear Safeguards Co. mechanical snubbers was being performed to obtain information for snubber changeout at the next cold shutdown. l This inspection revealed several INC mechanical snubbers installed on small diameter piping. These snubbers were determined to be safety related and had not previously been identified. Refer to Table I attached.  !

Further review revealed that other mechanical snubbers, previously identified as seismic Class II, were safety related. Refer to Table II attached. A cold shutdown was initiated to allow snubber stroke testing and replacement as required. Refer to Tables I, II and III attached for a listing of snubbers 1 tested, test results and piping systems affected. No technical specification action statements were entered as a result of snubber testing and replacement.

Table IV attached is a summary of all the INC mechanical snubbers tested during this outage.

Discovery of the " Frozen" snubber condition questions the ability of the snubber to perform its design function, i.e. Allow pipe movement during changing thermal conditions and provide a restraining force during a seismic event. Also, the " Frozen" snubber may have produced unexpected loads on their respective piping systems during changing thermal conditions.

Cause description and corrective actions:

The previous listing of mechanical snubbers did not include a review of small diameter piping. Small diameter pipe was originally determined to be " Chart Hung" pipe, therefore, no snubbers would be installed. A review of safety related pipe stress problems indicates that several small diameter pipe systems were " Analyzed" designs containing snubbers. This review also revealed that other portions of piping systems containing mechanical snubbers previously determined to be non-safety related were in fact safety related.

All safety related piping stress problems were reviewed for mechanical snubber identification and listing. Most mechanical snubbers previously classified as non-safety related were reclassified as safety related. The plant was placed in a cold shutdown and all safety related mechanical snubbers inside and outside containment were stroke tested.

All snubbers that failed to stroke were replaced with mechanical snubbers manufactured by Pacific Scientific Company. Each piping system containing a frozen snubber was stress analyzed to determine the loads produced by the frozen snubber on the piping system as the system expanded or contracted due to -

changing thermal conditions. Several areas of possible overstress were identified. Subsequent inspection of these areas did not reveal any detrimental effects due to the frozen snubbers.

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. o Page 2 of 2 ATTACHMENT TO LER #81-010/3L-0 Long term corrective action includes replacement of all INC mechanical snubbers i installed on hangers that support safety related piping systems.

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. I Page 1 of 1 ATTACHMENT TO LER #81-018/3L-0 ,

TABLE I SMALL DIAMETER PIPE MECllANICAL SNUBBERS i INC ,

MODEL TEST DATE PIPING SNVBBER IDENT. * # RESULT SYSTEM FSK-M-02-024 DP.23 1 5/6/81 ACC Main Steam FSK-M-02-025 DP.125 1 5/6/81 ACC Main Steam FSK-M-02-025 DP.125 1 5/6/81 ACC Main Steam FSK-M-02-027 DP.190 1 5/6/81 ACC Main Steam FSK-M-02-026 DP.307 1 5/6/81 REJ Main Steam FSK-M-02-023 DP.158 1 5/6/81 ACC Main Steam FSK-M-02-022 DP.109 1 5/6/81 ACC Main Steam FSK-M-02-030 DP.253 1 5/6/81 ACC Main Steam FSK-M-02-022 DP.107 1 5/7/81 ACC Main Steam SK-M-1016 DP.215 1 5/7/61 ACC Main Steam SK-M-1016 DP.208 1 5/7/81 REJ Main Steam FSK-M-02-097 DP.402 1 5/13/81 REJ Main Steam FSK-M-17-095 DP.501 1 5/7/82 REJ CVCS FSK-M-17-095 DP.34 2 5/7/81 REJ CVCS ,

FSK-M-17-103 DP.411 1 5/6/81 ACC CVCS FSK-M-17-013 DP.38 1 5/11/81 ACC CVCS I

FSK-M-15-029 DP.537 1 5/7/81 ACC HPSI FSK-M-15-021 DP.781 1 5/7/81 ACC HPSI FSK-M-32-012 DP.152 1 5/7/81 REJ Reactor Coolant

• Snubbers S/N cre not available - Snubbers are identified by piping dwg. and data point.

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ATTACHMENT TO LER #81-018/3L-0

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TABLE II I

"NEW" SAFETY RELATED MECHANICAL SNUBBERS ,

INC '

HANGER INC MODEL TEST DATE

1. S/N # RESULT PIPING SYSTEM 414001 002262 3 5/10/81 ACC Reactor Coolant Sys.

414001 002289 3 5/10/81 ACC Reactor' Coolant Sys.

414002 002271 3 5/10/81 ACC Reactor Coolant Sys. .

414002 002259 3 5/10/81 ACC Reactor Coolant Sys.

414006 61 2 5/10/81 ACC Reactor Coolant Sys.

414006 67 2. 5/10/81 ACC Reactor Coolant Sys.

414009 18229 3 5/10/81 ACC Reactor Coolant Sys.

414009 002251 3 5/10/81 ACC- Reactor Coolant Sys.

414016 59 2 5/10/81 REJ Reactor Coolant Sys.

414016 66 2 5/10/81 ACC Reactor Coolant Sys.

414018 270 1 5/10/81 ACC Reactor Coolant Sys.

414018 274 1 5/10/81 ACC Reactor Coolant Sys. ,

414021 88 2 5/10/81 ACC Reactor Coolant Sys.

414021 103 2 5/10/81 REJ Reactor Coolant Sys.

414024 68 2 5/10/81 REJ Reactor Coolant Sys.

414024 102 2 5/10/81 ACC Reactor Coolant Sys.

414025 415 2 5/10/81 ACC Reactor Coolant Sys.

414025 416 2 5/10/81 ACC Reactor Coolant Sys.

414027 81 2 5/10/81 ACC Reactor Coolant Sys.

414027 100 2 5/10/81 ACC Reactor Coolant Sys.

414029 76 2 5/9/81 ACC Reactor Coolant Sys.

414029 87 2 5/9/81 ACC Reactor Coolant Sys.

414029 88 2 5/9/81 ACC Reactor Coolant Sys.

414029 109 2 5/9/81 ACC Reactor Coolant Sys.

414032 80 2 5/9/81 REJ Reactor Coolant Sys. -

414032 101 2 5/9/81 ACC Reactor Coolant Sys.

414033 138 2 5/10/81 REJ Reactor Coolaat Sys.

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Page.? of 2 ATTACHMENT TO LER #81-018/3L-0 TABLE II "NEW" SAFETY RELATED MECHANICAL SNUBBERS INC HANGER INC MODEL TEST DATE i

1. S/N # RESULT PIPING, SYSTEM 414033 N/A 2 5/30/81 REJ Reactor Coolant Sys.

414035 176 1 5/11/81 REJ Reactor Coolant Sys.

514001 002152 4 5/10/81 ACC Reactor Coolant Sys.

411003 002272 3 5/11/81 REJ Feedwater 411009 60 2 5/11/81 REJ Feedwater 411009 104 2 5/11/81 REJ Feedwater 411016 002264 3 5/11/81 REJ Feedwater 411045 54 2 5/11/81 REJ Feedwater - - - --

411045 64 2 5/11/81 ACC Feedwater 411062 105 2 5/11/81 REJ Feedwater 411062 72 2 5/11/81 REJ Feedwater 513008 147 1 5/11/81 REJ Main Steam 513036 625 1 5/11/81 REJ Main Steam 513040 .

141 2 5/11/81 ACC Main Steam 513041 272- 1 5/11/81 ACC Main Steam 513042 None 1 5/11/81 ACC Main Steam 60026 1502 2 5/11/81 REJ Feedwater 60025 001627 2 5/11/81 REJ Feedwater

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Page 1 of 2 ATTACHMENT TO LER #81-018/3L-0 TABLE III "0LD" SAFETY RELATED MECHANICAL SNUBBERS

. INC HANGER INC' ' MODEL TEST DATE  :

1. S/N # RESULT PIPING SYSTEM 310022 44 2 5/9/81 REJ Safety Injection 410007 42 2 5/9/81 ACC Safety Injection 410092 36 2 5/8/81 REJ Safety Injection 510004 107 2 5/9/81 REJ Safety Injection 507002 002257 3 5/9/81 REJ Safety Injection 507002 002253 3 5/9/81 REJ Safety Injection 408001 32 2 5/9/81 REJ Reactor Coolant Sys 408002 24 2 5/9/81 ACC Reactor Coolant Sys i 408002 33 2 5/9/81 ACC Reactor Coolant Sys 408003 22 2 5/9/81 ACC Reactor Coolant Sys 408003 19 2 5/9/81 ACC Reactor Coolant Sys 408004 2 5/9/81 REJ Reactor Coolant Sys 408004 1. L 1 5/9/81 REJ Reactor Coolant Sys 408005 83 2 5/9/81 ACC Reactor Coolant Sys

, 408005 94 2 5/9/81 ACC Reactor Coolant Sys 408009 21 2 5/10/81 ACC Reactor Coolant Sys 408009 20 2 5/10/81 ACC Reactor Coolant Sys 408009 140 2 5/10/81 ACC Reactor Coolant Sys 408010 38 2 5/10/81 ACC Reactor Coolant Sys 408010 47 2 5/10/81 ACC Reactor Coolant Sys 408010 48 2 5/10/81 ACC Reactor Coolant Sys 408010 120 2 5/10/81 ACC Reactor Coolant Sys 408011 28 2 5/10/81 ACC Reactor Coolant Sys 408011 30 2 5/10/81 ACC Reactor Coolant Sys 408012 40 2 5/10/81 ACC Reactor Coolant Sys 408012 46 2 5/10/81 ACC Reactor Coolant Sys 410037 37 2 5/8/81 ACC Reactor Coolant Sys

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l Page 2 of 2 ATTACHMENT TO LER #81-0183L-0 TABLE III .

"OLD" SAFETY HELATED MECHANICAL SNUBBERS INC HANGER INC MODEL TEST DATE

1. S/N # RESULT PIPING SYSTEM i

410037 41 2 5/8/81 ACC React r Coolant Sys 410040 39 2 5/8/81 ACC Reactcc Coolant Sys 410046 27 2 5/8/81 REJ Reactor Coolant Sys 410049 45 2 5/8/81 ACC Reactor Coolant Sys 410054 34 3 5/8/81 ACC Reactor Coolant Sys 410059 002819 2 5/8/81 REJ Reactor Coolant Sys 410062 002260 3 5/7/81 REJ Shutdown Cooling 5/7/81. Shutdown Cooling 410062 002258 REJ 416016 160 1 5/9/81 ACC Containment Spray 416016 161 1 5/9/81 ACC Containment Spray 416021 162 1 5/9/81 ACC 3 Containment Spray 416022 165 1 5/9/81 ACC Containment Spray 416032 90 2 5/8/81 ACC Containment Spray 416032 71 2 5/8/81 .ACC Containment Spray 502035 002294 3 4/28/81 REJ LPSI/CS Common 502026 411 1 4/28/81 REJ LPSI/CS Common 402090 149 M 4/30/81 REJ LPSI/CS Common 402090 159 M 4/30/81 ACC LPSI/CS Common 402107 53 2 4/30/81 ACC LPSI/CS Common A

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, ATTACHMENT TO LER #81-018/3L-0 TABLE IV

SUMMARY

OF MECHANICAL. SNUBBER TESTING Total # of snubbers tested = 110 Total # of failures = 39 1 of 2 INC Model "M" failed to stroke 10 of 31 INC Model "1" failed to stroke 21 of 62 INC Model "2" failed to stroke 7 of 14 INC Model "3" failed to stroke 0 of 1 INC Model "4" failed to stroke ,

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