ML20198D135
| ML20198D135 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 05/11/1992 |
| From: | Schrage J COMMONWEALTH EDISON CO. |
| To: | Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9205180132 | |
| Download: ML20198D135 (4) | |
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i Commonwealth Edison 1400 Opus Place Downers Grove, Illinois 60515 9
May 11, 1992 Dr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 ATTH:
Document Control Desk
SUBJECT:
Quad Cities Station Units 1 and 2 Results of Reactor Head Inspection; Future Reactor Head Examination Plan MRC_DoctetJoL_50:25 Land _50:265
REFERENCES:
(a)
J.L. Schrage (CECO) to T.E. Murley letter dated September 30, 1991.
(b)
Teleconference between CECO (J.L. Schrage et al) and NRC (L.N. 01shan et al) on March 5, 1992.
(c) Conference between CECO (J.L. Schrage) and NRC (L.N. Olshan, H. Koo, B. Elliott) on March 19, 1992.
Dear Dr. Murley:
On April 19, 1990 members of the Nuclear Reactor Regulation's (NRR) and Commonwealth Edison Company's (CECO's) staff conducted a technical meeting to discuss the cracks identified in the Quad Cities Unit 2 Reactor Vessel Head. During that meeting, CECO committed to perform inspections of the Reactor Vessel Heads at each of its Boiling Water Reactor (BWR) Plants.
In Reference (a), CECO described the Reactor Head and Upper Shell Inspection Plan for Quad Cities Station Unit 2 for the winter refuel outage (Q2011). This inspection plan was implemented during the outage.
The purpose of this letter is to describe the results of that inspection and provide the Quad Cities Unit 2 Reactor Head and Upper Shell Inspection Plan for future refuel outages.
The results of the inspection were discussed with your staff in a teleconference on March 5, 1992 (Reference (b)), and are described in.
The inspection resulted in the following conclusions:
There were no new flaws detected in the cladding and base metal.
There were no apparent changes in length and depth of the existing flaws.
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' Dr. Murley May 11, 1992 There was no pitting in cavities where base metal was exposed.
There were no apparent changes in length and depth of flaws which were associated with cavities.
The proposed Reactor Head and Upper Shell Inspection Plan for future Unit 2 refuel outages was also presented to your staff during the March 5, 1992 teleconference (Reference (b)).
The staff raised questions during that teleconference regarding the proposed UT sizing of existing cracks.
CECO revised the proposed inspection plan to address these questions, and presented this revision to your staff during a conference on March 19, 1992 (Reference (c)).
The revised plan required UT sizing of three surface penetrating cracks and three embedded cracks, including the deepest crack.
During the March 19, 1992 conference, the staff Indicated that the revised inspection plan adequately addressed the questions which were raised during the March 5, 1992 teleconference.
Therefore, the final Reactor Head and Upper Shell Inspection Plan for future Quad Cities Unit 2 refuel outages is submitted for your staff's review (Attachment 2).
If there are any questions or comments on either the results of the recent inspection, or the Reactor llead and Upper Shell Inspection Plan for future Unit 2 outages, please contact John L. Schrage at 708-515-7283.
YY
/ ohn L. Schrage Nucia r Licensing Administrator Attachment cc:
A. Bart Davis, Regional Administrator - RIII L. N. Olshan, Project Manager - NRR-T. E. Taylor, Sen10r Resident Inspector - Quad Cities B. J. Elliot, NRR Technical S' aff i
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ATTACHMENT 1 QUAD CITIES UNIT-2 RPV HEAD EXAMINA110N RESULTS (Q2Ril) 1.
VT-3 100% OF RP'l HEAD ID, OUTSIDE THE 12" HIDE BAND CENTERED ON THE RPV HEAD-TO-FLANGE HELD.
Result:
A Section from 100* to 125* on the ID of the RPV Head Dollar weld had heavier rust appearance.
2.
VT-1 0F ALL EXCAVATED CAVITIES (WHERE BASE METAL EXPOSED).
Result:
No pitting, insignificant rust spots in base metal.
3.
- a. SECTION FROM 100' to 125' 0F RPV HEAD DOLLAR HELD ID, Resplf:
No relevant indications.
- b. 12" HIDE BAND CENTERED ON 10 0F RPV HEAD-TO-FLANGE, INCLUDING EXCAVATED LOCATIONS WITHIN THE BAND AND AT 60" & 25" AB0VE FLANGE SURFACE.
Resylf:
No apparent increases in number of flaws or in length of existing flaws.
4.
UT FROM OD OF RPV HEAD-TO-FLANGE USING ENHANCED TECHNIQUE.
Re_s ylt : UT detected 20 crack-like indications that resulted in app;oximately 197" total flaw length or 25% of weld length using OD measurements.
In 1990, similar UT detected 21 crack-like indications that resulted in approximately 255" total flaw length or 32% of weld length.
Ch&nges in the evaluation of clad roll and crack signals account for the majority of the difference in total flaw length.
5.
UT SIZING FROM 10 (14 FLAHS AT 18 LOCATIONS).
Resu.I t :
Maximum flaw depth is 0,.24" into base metal.
Maximum flaw depth in 1990 was 0.22" into base metal.
6.
CONCLUSION:
- a. No new flaws detected in cladding and base metal.
- b. No apparent changes in length and depth observed on existing /old flaws.
- c. No pitting observed in cavities where base metal is exposed.
No apparent changes in length and depth of flaws that are associated with cavities.
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ATTACHMENT 2 QUAD CIllES UNIT-2 IUTURE RPV llEAD EXAMINAIION PLAN 1he following examination plan will be implemented in lieu of the successive examination requirements of ASME Section XI IWB-2420 (b) on the Quad Cities Unit 2 RPV head every other scheduled refueling outage, beginning with Q2R13 which is currently scheduled for September 1994:
1.
Visually examine (VT-3) 100% the inside surface of the Reactor Pressure Vessel (RPV) Head. Conditions to be examined for and recorded:
I a.
New cracks and linear-indications.
b.
Existing cracks that show a definite increase in length.
c.
Heavy / unusual rust streaks.
2.
Visually examine-(VT-1) all excavated cavities, where base metal is exposed, for pitting and cracking of the low alloy steel material.
3.
If necessary, liquid dye penetrant test (PT) may supplement the visual examinations of activities 1 and/or 2.
4.
Ultrasonically test (OT), from the ID and/or ! J as allowed by surf ace condition to determine flaw depth, the following:
a.
All cracks found by activities 1 and 2.
b.
Six locations (stamped with low stress markers) with existing cracks which are in the 12 inch wide band centered (nominally) on the ID of the RPV head-to-flange weld.
At least three of the six locations to be monitored are associated with ID surface penetrating cracks as determined by PT.
5.
The flaw characteristics found by activity 4.b. will be compared to the 1992 as-left flaw characteristics to determine crack growth.
Modification to this examination plan may be necessary if significant l
cract initiation or significant cract growth is observed during future RPV head examination.
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