ML20093K183
| 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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cy.
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