ML20093K183

Interim Deficiency Rept 55-84-19 Re Nelson Studs on Embedment Plates Parting from Back of Plate.Initially Reported on 840828.Investigation Continuing.Final Rept Due in Approx 90 Days

ML20093K183
Person / Time
Site:	Clinton
Issue date:	10/01/1984
From:	Hall D ILLINOIS POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
55-84-19, U-10204, NUDOCS 8410170211
Download: ML20093K183 (3)

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- 130 ILLIN0/S POWER COMPANY l9,94 CLINTON POWER STATION. P.O. BOX 678. CLINTON. ILLINOIS 61727 October 1, 1984 Docket No. 50-461 Mr. James G. Keppler Regional Administrator Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137

Subject:

Potential 10CFR50.55(e) Deficiency 55-84-19:

Nelson Studs On Embedment Plates

Dear Mr. Keppler:

On August 28, 1984, Illinois Power Company notified Mr. F.

Jablonski, NRC Region III, (Ref:

IP Memorandum Y-20790, dated August 28, 1984) of a potentially reportable deficiency concern-ing Nelson Studs on embedmant plates which have parted from the back of the plate.

Our investigation of this issue is continu-ing, and this letter is submitted as an interim report in accor-dance with the requirements of 10CFR50.55(e) (3).

Attachment A provides the details of our investigation to date.

We trust that this interim report provides you sufficient background information to perform a general assessment of this potentially reportable deficiency and adequately describes our overall approach to resolve the issue.

Sincerely yours, D.

. Hall Vice President RLC/cbs (NRC) cc:

NRC Resident Office, V-690 Director - Office of I&E, US NRC, Washington, DC 20555 Illinois Department of Nuclear Safety INPO Records. Center

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'55TTICHMENT A'

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Ut Illinois Power Company LClintonRPower Station

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Docket 4No.'50-461~

PotentiAll0CFR5b.5'5(e) Defic'iency 55-84-19

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Nelson Studs on'Embedment' Plates-Interim' Report; Statementiof Potentially Reportable Deficiency / Background Nonconformance' Report (NCR) No. 2dO311was written to docu-ment a condition 1where aniembedment plate on.the outside of the

'drywell. wall had pulled away'from-the concrete 1(Az 128* el. 753',

S&L dwg.-S27-1002-03A).

To aid in dispositioning of thisicondi-ei tion,'the concrete was excavated along the edges of;thesplateLto:

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expose the embedded Nelson studs ~behind'the' plate..All seven-(7) studs in the outer row-were exposed.

Six-(6).of-the seven-(7) studs were found detached from the back of the' plate.

A second platelat1Az 140' was also excavated and'found with two (2) of' four (4) exposed studs parted from:the back of~the. plate (NCR 21516).

An. investigation and evaluation of this issue is being performed to determine the extent of this, problem, affect on.

installed hardware, and significance to the safety;of operation'-

of CPS.

Investigation Results/ Corrective Action:

There are five (5) enbedment plates in the drywell exterior wall with similar design.

Each'of these plates.have four (4):

vertical rows, each with 7 studs which are attached:to the back of the plate.

The original design for the beam end. connections t

requiredEclip angles to be welded to'the embedment plates..

Later it becane necessary to modify the end-connections..'The connections on the embedment plates at azimuth.174*, 157",1140",

128* for beam' numbers 101, 102, 103 and 104 respectively, were-modified per detail 27-290 on drawing S27-1436.- This detail' requires a 1" x 7 3/4" x l' - 9" long plate to be welded vertically to the embedment plate using 7/8" fillet welds.

In-addition a second plate 1".x-l'

- 9" long was to be.added near the bottom of the embedment' plate using a full penetration single.

beve1~ weld in the horizontal direction.

Nonconformance report 18722 now becomes relevant in'this investigation-in'that it !

documents that the.embedments for beams 101, 102, 103 are out of design' location.

The locations are off in elevation'alightly, and'off:in azimuth.

It was noted from fieldiinspection.that the attachments for each of the 4 beams are eccentric to the centerline-of the embedment plate.

This fact is' pertinent.when.

trying to' establish the stud failure mechanism.

It is postulated that the cause of. failure was assymetrical heating: causing 1 thermal stress development:and plate distortion.due to shrinkage of the heavy welds described.

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ATTACHMENT A (continued)'

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-Sargent & Lundy (S&L) has been requested to investigate this-

' hypothesis:and estimate the. thermal stress levels.

This may give

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i insight-to the failure mechanism and could establish the bounds of,the problem.

5 The embedment plate at AZ 315 has also been modified from

-the original detail.which_ required 7" x 4" x %" clip angles,-l' -

L 7%" long.

The new detail 27-596A on drawing S27-1458 requires 7" r

x 4" x 3/4" angles with a 11/16" fillet weld.

This welding and the configuration generally will not cause the weld shrinkage problems postulated on the four previously mentioned plates.

It should be noted. that general note 4 int drawing S27-1436 requires that the interpass temperature.be limited-to 350 F when welding.

to the embedment plates.

I The complete scope and root cause(s) of this issue'have not yet been identified, such that a determination of remedial and generic corrective action can be made.

Identified discrepancies are-being documented on NCRs and~

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1 will be resolved in accordance with approved site procedures.

Safety Implications / Significance Illinois Power's investigation of this potentially report-able deficiency is continuing.

The-safety implications and significance will be acsessed after further background informa-

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tion is evaluated.

Approximately ninety'(90) days.will be j

required to complete the investigation, determine reportability, and file a final report on this potentially' reportable deficien-

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