ML040440457
| ML040440457 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 10/30/2002 |
| From: | Gray B, Robert Lewis Entergy Operations |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| 51-5012789-00 86-E-0074-164, Rev 0 | |
| Download: ML040440457 (6) | |
Text
ENCLOSURE 2 CNRO-2002-00054 ANO CALCULATION 86-E-0074-164 (FRAMATOME DOCUMENT 51-5012789-00)
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ARKANSAS NUCLEAR ONE Page I
E-DOCTITLE:
E-DOC NO.
CHANGE NO.
CALCULATION SUBMITTAL SHEET 5010.015-ATT 002-00-0 This Document Contains I Page(s)
Arkansas Nuclear One CALCULATION SUBMITTAL SHEET TO: ADMINISTRATIVE SERVICES DATE:
1012812002
- FROM, Ryan Linebarger CALCULATION NO.:
86-E0074-164 REV. NO.:
0 The urpse o His sbmittal Is t dentify thstatus of the STATUS:
A Remarks: Thanks!
Status Codes p
(Pending)
Not Currently Installed, awaiting a Technical Specification change or design change implementation A
(Active)
Qualified Existing Installed Condition H
(Historical)
Historical Record, not replaced with a revised or new calculation and can be used as a reference.
Provide remarks If dassification of the calculation Into one of these status codes needs further darificaton. Also, for status of P provide remarks that Identify when calculation status is expected to change (i e what actions are planned-design change package number, Condition Report and Action Item number etc.). It should be understood that any schedule Information provided wUIl be preliminary.
cc: Calc File
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11 ARKANSAS I
OM E-DOC ITLE:
CALCULATION COVER AND REVISION SHEET I EDOC NO.
CHANGE NO.
6010.01 -ATT-2 002-00-0 I
ARKANSAS NUCLEAR ONE CALCULATION COVER SHEET CaIc. No.: 85-E-0074-164 Rev. No.: 0 Calc.
Title:
B&WIfl "Evaluation of Potential for Unit:
1 Category:
Q Loose Parts In the RCS from the CRDM IDTB System(s):
RCS Repair" CaIc. Type:
BW Components:
Topic(s):
STRU ComoTag Suffix Comp Code PitArea:
Bldg.
IRB Elev.
376' R-1 Vessel Room Wall
-._..Coordinates:
Config. Checklist (per 5010.004) completed? YV N 0 Document CornmentfResolution Form completed? Y 0 N 3 Abstract (included PurposelResults):
Determine If the remnant of the J-groove weld will crack and create debris that would effect operation of the CRDM.
Pages Revised andlor Added:
All New Pages 14 I
Purpose of Revision:
Initial Issue Initiating Document Resulting Document Key Design Input Document ER-ANO-2001.0230-020 Framatome Calc: 61-501278900 Verification Method:
Design Review X Alternate Calculation Qualification Testing Amends Calc(s):
None Supersedes Calc(s)/CRN (s):
None
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Approver: Raymond S Lewis e'I
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2D448 (12oo1) 2RAMATOME ANP ENGINEERING INFORMATION RECORD Document Identifier 51-5012789 - 00 Tite Evaluation of Potential for Loose Parts in the RCS from the CRDM DTB Repair PREPARED BY:
- Name H.W. Behnke Signature' Techical Manager Statement Intials Reviewer is Independen REVIEWED BY:
Name B.L Boman J
Signature 2v Date Date
_o, Rearks:
This document presents a qualitative assessment of the potential for loose parts to be generated as a result of the CRDM ID Temper Bead Weld Repair.
Initial Issue Document 88 E-0074-164 Number
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51-5012789-00 Page 2 of 3
Background
One of the repair methods for leaking CRDM nozzles is to remove the flawed portion of
-the CRDM nozzle and reattach t no e to the ID of the penetration at a higher elevation. The boring process to remove the nozzle will leave most of the original partial-penetration weld Intact. A question has arisen as to whether or not the remaining material w'll experience cracking sufficient to form debri that results in a safety issue.
Summary The potential for the remaining CRDM nozzle weld material (i.e., post-repair) to present a safety concern is considered extremely unlikely. This is based on a qualitative assessment of the degree and orientation of cracking required to generate weld debris of sufficient size to interfere with control rod Insertion and field observations from weld material cracks.
Basis of Assessment In FRA-ANP Document 51-5012057-00, the safety impact of CRDM nozzle debris was assessed. It was determined that of the potential locations in the upper plenum for this debris to settle, only e column weidment locations posed a safety risk. If the debris were to enter the column weldments, pieces on the order of 0.75 inches or larger (for at least one of the dimensions) could preclude complete control rod nsertion. Pieces smaller than this size are unlikely to Interfere with rod nsertion.
One of the repair methods for leaking CRDM nozzles Is to remove the flawed portion of the CRDM nozzle and reattach the nozzle to the ID of the penetration at a higher elevation. The boring process to remove e nozzle will leave most of the original partial penetration weld. The weld ID will be enlarged to at least 4-1/16 Inches and the ID comers will be chamfered to remove sharp edges and possible slivers generated by boring operation.
It is postulated that the as-left weld will contain defects possibly as deep as the partial penetration weld groove. These defects are assumed to be radial with respect to the nozzle bore which is the conservative orientation to address flaw stability in the given stress field.
The question that was raised was the impact of also assuming a transverse crack was present which would eventually bridge two radial cracks and therefore creates a loose part. The credibility would then be addressed regarding the possibility of increased likelihood of a forced plant shutdown.
The scenario for a loose part Is considered to be a very low probability event for the following reasons:
Document 88-E-0074-16s4 Number Page 3 OF 4
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- 1) Observed flaws n the welds to date have been generally radial with respect to the nozzle centerline.
- 2) Transverse-oriented flaws have been associated with original weld defects..
Flaws at the weld root or in the weld along the weld beads are circumferentially oriented with respect to the penetration but have a small planar depth normal to the penetration.
- 3) Driving force to grow transverse flaws without the nozzle would be associated with weld residual stress and exposure of the flaw to the primary coolant Restraining forces on the weld could drive a transverse flaw If It Is normal to the ID head surface. There are virtually no driving forces while the plane of the flaw is in the plane of the head. This latter condition is the orientation of the transverse flaws at the root of the weld. Operating thermal stresses would have the same general pattern as the weld shrinkage stresses but lower in magnitude.
Operating pressure stresses would not drive a transverse crack.
- 4) The residual and thermal stress values are self-limited by the radial cracks. If two radial cracks exist In close proximity to each other then there is no hoop restraint between the cracks and the crack driving force for a transverse at either orientation mentioned above goes to essentially zero.
It is concluded that there are no known service conditions that could drive radial cracks and transverse cracks to Intersect and produce a loose part. In particular the portion of the transverse crack, which would lie In the plane of the head (in the laminar direction),
has virtually no driving stress. The possibility of this event would have to be enhanced by the presence of a significant manufacturing flaw. It has been determined In the prior loose part assessment that the size of a fragment to potentially hinder control rod insertion would be on the order of I"x I x %' or larger. The 1-radial dimension is feasible due to the depth of the partial penetration groove could exceed one Inch.
However a %/-Inch transverse defect Is highly unlikely due to the nature of the welding process and the non-destructive testing performed during fabrication.
Since the plant safety analyses include consideration of one stuck control rod, the likelihood of weld material debris to result in more than one control rod to Insert Is judged to be of such low probability that the proposed repair technique does not pose a safety risk.
Document 88E-0074-164 Number P
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