ML20212C750

Interim Deficiency Rept CDR 86-00-08 Re Cable Tray Hold Down Clamps.Initially Reported on 860716.Program to Retorque All Cable Tray Hold Down Clamps in safety-related Areas Implemented.Next Rept by 860815

ML20212C750
Person / Time
Site:	Seabrook
Issue date:	07/18/1986
From:	Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:	Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
CDR-86--8, CDR-86-00-08, SBN-1163, NUDOCS 8608120126
Download: ML20212C750 (4)

Text

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'D SEABROOK STATION Engineering Office July 18, 1986 Put2c Service of New Hampshire SBN- 1163 NEW HAMPSHIRE YANKEE DIVISION United States Nuclear Regulatory Connaission Region I 631 Park Avenue King of Prussia, PA 19406 Attention: Mr. Richard W. Starostecki, Director Division of Project and Resident Programs

References:

(a) Construction Permits CPPR-133 and CPPR-136, Docket Nos. 50-443 and 50-444 (b) Telecon of July 16, 1986, D. A. Maidrand to D.

Havercamp (Region I)

Subject:

Interim 10CFR50.55(e) Report: Cable Tray Hold Down Clamps (CDR 86-00-08)

Dear Sir:

In reference (b), we reported a 10CFR50.55(e) deficiency regarding the cable tray hold down clamps.

Description of Deficiency This deficiency involves the failure to ensure vendor torque require-ments were met for the cable tray hold down clamps. The clamps are used to secure the cable tray to the cable tray support.

The omission of adequate torquing of the clamps was a result of the failure to eltarly translate the design torquing requirements of the electrical notes and details into installation and inspection criteria.

The deficiency was identified during completion of the final torque i verification program.

l Safety Implication i

Loss of pre-torque can result in tray slippage in the horizontal plane ]

during a postulated seismic event. The slippage would result in increased deflection of attached conduit and wireway and could impact cable termina-tions.

l 8608120126 860718 PDR ADOCK 05000443 S PDR 2 Seabrook Station Construction Field Office . P.O. Box 700 Seabrook NH O3874 -

TV ' ) 1

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United States Nuclear Regulatory Commission SBN-ll63 i Attention: Mr. Richard W. Starostecki Page 2 1

i Corrective Action We have implemented a program to re-torque all cable tray hold down clamps in safety-related areas. Furthermore, we will revise the installation and inspection criteria to assure the torquing requirement for the clamps is clearly identified.

The schedule for completion of the program is provided as Attachment 1 to this letter. All cable tray hold down clamps will be pre-torqued to the specified value prior to the movement of fuel.

The following information is provided as justification for allowing this work to be completed in the time period from the granting of the low I power license to the movement of fuel.  ;

The acceptance of bolt torque less than specified values for interim operation is based on two considerations:

1. The suppor t structural integrity is not dependent on the function of hold down clamps. The tray clamp / bolt assembly provides a secondary function with respect to support performance.

2. The tray clamp / bolt assembly presently exhibits, on an average, a torque value which can resist design level seismic loading.

A discussian of these two considerations follows:

1. Trsy Clamp / Bolt Assembly Function:

The tray clarp/ bolt assembly serves no function during normal operation.

During a seismic event, the tray clamp / bolt assembly provides the following two second try functions:

a. They transmit load from tray to support and

b. They limit tray and support displacements.

The overall integrity of the support system is not primarily depend-ent oa the tray clamps. The ANCO Dynamic Testing Program demonstrated that support integrity is dependent on the primary connections (connections tc the building). In addition, if the tray clamps did not function, the affect on the structural integrity of the support system would result in less sustained load transmitted to the support. l The inability of the tray clamps to limit displacements is not a major concern. Proximity surveys which were a part of our seismic interaction program revealed that the number of plant hardware items located close (within 4") to supports and trays is not significant. In addition, i flexible connections and some degree of cable slack exists at cable j termination points providing additional flexibility for termination protection. )

l i

. c United States Nuclear Regulatory Commission SBN-1163 Attention: Mr. Richard W. Starostecki Page 3

2. Tray Clamps Have Partial Design Torque Based on random site-wide sampling, the tray clamps presently exhibit an average torque value of approximately 25ft-lbs, The following evaluation demonstrates that a torque lower than the design value could resist design level seismic loading. This discussion applies to both support integrity and support / tray displacements.

a. The amount of resisting clamping force that the clamp pro ides is directly proportional to the amount of applied torque.

b. The applied force to the clamp is a product of applied seismic accelerations and the mass of the cable tray (with cables) i (F=ma).

c. The ANCO dynamic testing ef fort demonstrated that no slippage of tray clamps occurred at site envelope SSE loading, with torque equal to 50ft-lbs and trays fully loaded.

d. The required torque for each plant area can be computed by ratioing the average tray weight and envelope seismic spectra of that area to the same parameters for the ANCO test.

e. A survey of plant areas working with the average tray weights and seismic spectra revealed that the maximum average torque value required was 22f t-lbs. This value was computed for the Contain-ment Building which does exhibit relatively large seismic accel-eration.

We will submit an additional report to Region I by August 15, 1986.

Very truly yours, in John DeVincentis 4 Director of Engineering Attachment cc: Atomic Safety and Licensing Board Service List Director, Office of Inspection and Enforcement

! United States Nuclear Regulatory Commission Washington, DC 20555 l

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