ML20084N293
| ML20084N293 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 06/02/1995 |
| From: | Schrage J COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-94-03, GL-94-3, NUDOCS 9506070697 | |
| Download: ML20084N293 (4) | |
Text
n Commonw cahh ihm Company 5
I 4G Opm Place Downers Grove, ItlD515
,j e
June 2,1995
~ U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attn: Document Control Desk
Subject:
Quad Cities Nuclear Station Unit 2 Core Shroud Examination Final Results NRC Docket No. 50-265
References:
1.
NRC Generic Letter 94-03, "Intergranular Stress Corrosion Cracking of Core Shrouds in Boiling Water Reactors".
2.
BWRVIP document GENE-523-113-0894, BWR Core Shroud Inspection and Evaluation Guidelines, dated September 1994.
3.
BWRVIP Core Shroud NDE Uncertainty and Procedure Standard, dated November 21,1994.
4.
J.L. Schrage (Comed) to USNRC letter, Quad Cities Station Unit 2 Core Shroud Inspection Plan, dated January 16, 1995.
The purpose of this letter is to provide the final results of the subject core shroud examinations.
The examinations were performed in conjunction with the comprehensive shroud repair to assure that structural integrity of the core shroud is maintained. The examinations of the reactor core shroud were performed in accordance with Comed's commitment to NRC Generic Letter 94-03 (references 1 and 4) and BWRVIP guidelines (references 2 and 3). The results of these examinations indicate that the observed stress corrosion cracking (SCC) at Quad Cities Unit 2 is substantially less than that observed at other similar units. The examinations were performed April 13 through April 20,1995 and May 16 through May 21,1995.
The core shroud examinations consisted of performing ultrasonic examination (UT) of the vertical shroud welds which were accessible to the scanner system. In addition, visual examinations were performed on the accessible surfaces of the shroud head flange ring, the top guide suppon ring, the core plate support ring and shroud vertical welds which were not UT examined.
It should be noted that the ring segment welds associated with the shroud head flange ring, the top guide support ring and the core plate suppon ring were not visually located due to machining of the rings / welds during original fabrication. Therefore, all accessible surfaces of the rings were visually examined.
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r U.S. NRC June 2,1995 The scope of the examinations and results were as follows:
Ultrasonic examination of the shroud vertical welds (V14 through V19) located between o
horizontal welds H3/H4 and H4/H5 (i.e. beltline region). The examinations resulted in no reportable indications.
Enhanced visual examination of the shroud head flange ring, top guide support ring, core plate o
support ring, shroud vertical welds (V5-V7 and V26-V28, inclusive) and the shroud repair hardware attachment sites at the jet pump support plate. The examinations resulted in a total combined crack length of 51" with the longest observed crack 24" in length.
In conclusion, the indications observed on the core plate support ring vertical (OD) surface result in a total combined crack length of 51" or approximately 15% of the area examined. The observed SCC is considerably less than that observed at other units of this vintage. As expected, the indications are associated with the heat affected zone (HAZ) of horizontal weld H5. The installed shroud repair has been designed to structurally replace the shroud horizontal welds.
The attached table and sketch provide specific details of the areas examined and the results of the examinations.
To the best of my knowledge and belief, the analyses and evaluations contained in these documents are true and correct. In some respects these documents are not based on my personal knowledge, but on information furnished by other Commonwealth Edison employees, contractor employees, and/or consultants. Such information has been reviewed in accordance with company practice, and I believe it to be reliable.
If there are any questions concerning this matter, or need for further clarification, please contact this office.
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Attachment Figure J. B. Martin, Regional Administrator. RIII cc:
R. M. Pulsifer, Project Manager - NRR C. G. Miller, Senior Resident Inspector - Quad Cities Office of Nuclear Facility Safety - IDNS kAnh\\ quad \\ shroud \\q2,,shrdyf
ATTACHMENT Core Shmud Fumination Summary Component Area inspected Inspection Results Shroud llead Visually examined 100% of accessible 3/4" long indication at 290" in Flange Ring surfaces or 72% (499") of OD,100%
steam dam to ring fillet weld.
111 (665") of ID and 100% (690") of Top of ring.
Top Guide Visually examined 100% of accessible No Reportable Indications Support Ring surfaces or 100% (690") of OD and 100%
112-113 (690") of Bottom of ring.
Core Plate Visually examined 100% of accessible 2" long cire. indication at 20" Support Ring surfaces or 55% (356") of OD and 55%
24" long cire. indication at 45'
!!5-116 (356") of Bottom of ring.
10" long cire. indication at 80*
6" long cire. indication it 143' Approximately 15% (51") of area 1" long cire. indication at 200*
examined has indications in the 11AZ 8" long cire. indication at 350" associated with the 115 horizontal weld.
3 axial indications at 163*,1/4" to 1/2" in length at toe of 115 Vertical Welds Visually examined at least 12" or 36% of No Reportable Indications VS, V6 and V7 each weld, inspected OD surface, ID not accessible.
Vertical Welds Ultrasonically examined 27" or greater than No Reportable Indications Vl4,V15, 30% of each weld.
V16,V17,V18 and Vl9.
Vertical Welds Visually examined at least 12" or 22% of No Reportable Indications V26, V27 and each weld, inspected OD surface, ID not V28 accessible.
Shroud Ledge 10" of weld in area of repair attachments at No Reportable Indications to Shroud 4 locations; 20,110", 200",290" azimuths.
118 Weld Shroud Ledge 12" of weld in area of repair attachments at No Reportable Indications to RPV 4 locations; 20",110, 200",290* azimuths.
119 Weld Shroud Ledge Examined face of plate in area of repair No Reportable Indications in Area of attachments; approximately 150 square Repair inches at 4 locations; 20*,110, 200*,290*
Attachments azimuths.
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