ML20066D963
| ML20066D963 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 01/11/1991 |
| From: | Creel G BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9101170178 | |
| Download: ML20066D963 (6) | |
Text
13 ALTIMORE O AS AND ELECTRIC CHARLES CENTER e P.O. BOX 1475
- BALTIMORE, MARYt.AND 21203 1475 GroRot C CRtto Vics Pma siot 41 NvCg tasi r htmov (300(*0 44BS January 11,1991 U S. Nelear Reguhtory Commission Washbypon, DC 20535 ATTENTION:
Document Control Desk S1111 JECT:
Calvert Cliffs Nuclear Power Plant Unit Nos,1 & 2; Docket Nos 50-317 & 50 318 Report of Steam Generator Tube Plugeine
REFERENCE:
(a)
Calvert Cilffs Unit 1 Technical Specification 4.4.5.5.a (b)
Calvert Climi Unit 2 Technical Specification 4.4.5,5.a Gentlemen:
As required by References (a) and (b), this letter reports the numb:.r of tubes plugged in the Calvert Cliffs Unit 1 and Unit 2 Steam Generators. Unit I has recently completed a five month maintenance outage. Unit 2 Steam Generators have recently undergone their second inservice inspection during the cuirent outag :. The previous examint.,m was completed in April 1989, and the results reported to the NRC.
LINIT 1
- For Unit 1, seven tubes were found to have indications which exceeded the Technical Specification plugging limit and were plugged. An additional five tubes were plugged as a preventive measure. Of the twelve tubes plugged during this inservice Inspection, nine tubes were plugged in Steam Generator No. I1 and three tubes were plugged in Steam Generator No.12.
Attachments (1) and (2) list the tubes plugged during the 1990 Unit 1 Testing and Maintenance Outage along wiih the reason for plugging each tube. Attachment (3) is a sketch indicating Steam Generator support locations and nomeractature.
All of the tuba in service in eac'. Stcom Generator were examined. The 100% standard Bobbin Coil inspection required a total of 16,874 tubes to be examined. Of the 16,874 tubes examined,222 tubes had indications of 20% or greater through wall degradation. As stated above. seven of these indications exceeded the plugging limit. Five tubes were plugged in Steam Generator No.1I and two tubes were plugged in Steam Generator No.12 for this reason.
POR ADOCK 0500031,7 g\\kg0N 9101170178 91011'.
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i Documeni Control Desk
' January ll,1991 Pa;c 2 In addition to the Bobbin Coil Examination, opproximately 2S00 tubes per Steam Generator were examined with a motorized rotating pancake coil in the area of the roll transition at the top of the -
tubeshect. This examination was performed to verify the absence of circumferential cracking in this region that has been identified at other plants.
As a preventive measure, Hvc additional tubes with distorted Eddy Current testing indications in the r.ludge pile were plugged. Of these additional five tubes taken out of service, four were in Steam Generator No.11 and one was in Stearn Generator No.12. Previous metallurgical examination of Unit 1 tubing has shown degradation in the sludge pile area was caused ( Intergranular Attack (lGA). These five tubes in the sludge pile region with distorted indications were plugged because of the potential for a local active IG A mechanism.
I EIT 2 During this inspection of Unit 2 Steam Generators, na tubes were found to exceed the Technical Specification Plugging limit, therefore, no tubes were plugged. The standard Bobbin Coil inspection included 1,422 tubes in Steam Generator No. 21 and 1,246 in Steam Generator No. 22. Of the 2,668 tubes examined,158 tubes had Eddy Current Indications of wallloss between 20% and 39% of the nominal wall thickness. However, only 20 of these tubes exhibited greater than 10% further wall penetrations from previous outages and were classified as degradcd tubes for this inspection. The results of the examination were therefore classified as Category C4 in accordance with Technical Specification 4.4.5.2.
In addition to the Bobbin Coil Exam:aation, approximately 3,000 tubes per Steam Generator were examined with a Motorized Rotating Pancake Coilin the area of the roll transition at the top of the tubesheet. This examination
.is performed to verify the absence of circumferential cracking in this region that has been identified at other plants.
During the preparation of this report, it was discovered that we had not met the schedule requirements of Technical Specification 4.4.5.5.a. for submitting this Unit I report. This Technical Specification requires that:
"Following each inservice inspection of steam generator tubes, the number of tubes plugged in each steam generator shall be reported to the Commission within 15 days pursuant to Specification 6.9.2,"
Review also showed that the Unit 11982 report had been submitted late and that we had typically not submitted reports unless tubes had been plugged. Annual reports have been filed each year which describe the Steam Generator inspection activity for the previous year. This ensures that the NRCis int' armed of the status of each Steam Generator, including any tubes plugged.
The root cause of this problem was personnel error due to inadequate definition of the reporting requirements. The tube inspection procedure (STP M-574) and the tube plugging procedure (SG-
- 13) will be changed prior to their next use to clearly establish the reporting requirements in order to prevent recurrence.
i I
Document Control Desk
' January 11,1991 Page 3 should you have any further questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours, W
/
/
GCC/ PSF /dtm Attachments: (1)
Steam Generator No.11 Tubes Plugged During the 1990 Outuge (2)
Steam Generator No. 21 Tubes Plugged During the 1990 Outage (3)
Cutaway View, Steam Generator cc:
D.,.. Brune, Esquire J. E Silberg, Esquire R. A. Capra, NRC D. G. Mcdonald, Jr., NRC T. T. Martin, NRC L E Nicholson, NRC R. I. McLean, DNR l
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-.... ~. - -. -
I 7
' EITACllhtENT m :
STEAM GENERATOR No. Il TULLES FI,UGGED DURING Tile 1990 OUTAGE l
-j 4-(_
ROW LINE REASON FOR' PLUGGING 10 24 Eddy Current testing distorted indication j
at HTS SF + 0.0 inches j
60 60 Eddy Current testing indication of 63% wallloss 1
originating on the outside diameter of the tube -
at HTS-SF + 0.80 inches 13
- 61 '
- Eddy Current testing distorted indication i
at HTS SF + 0.0 inches 113 81 Eddy Current testing distorted indication 1
at HTS-SF + 0.0 inches
!q 139 83 Eddy Current testin'g indications c,f 67% and 53%
wall loss originating on the outside diameter of the tube at HTS-PF + 20.00 inches and
. HTS PF + 19.60 inches respectively 90 Eddy Current testing indication of 59% wallloss originating on the outside diameter of the tube at IITS SF + 1.10 inches
-129 71 Eddy Current testing distorted indication
-at C4 '+ 6.6 inches 51 113 Eddy Current testing indication of 62% wall loss a
originating on'the outside diameter of the tube at HTS SF + 0.90 inches 1
o
- 53 113' Eddy Current testing indication of 48% wallloss originating on the outside diameter of the tube -
- 4 at IITS SF + 0.70 inches '
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A'I'I'AClIMENT (2)
STEAM GENERATOR No.12 TULLES l'i,UGGEI)_DURING TIIE 1990 OUTAGE i
ROW LINE REASON FOR PLUGGING 72 78 Eddy Current testing indication of 45% wall loss originating on the outside diameter of the tube at HTS SF + 0.90 inches 74 80 Eddy Current testing indication of 48% wallloss originating on the outside dianicter of the tube at IITS-SF + 1.00 inches 123 93 Eddy Current testing distorted indication at HTS-SF + 8.8 inches 1
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