ML20031F203
| ML20031F203 | |
| Person / Time | |
|---|---|
| Site: | Oconee, Pilgrim, Yankee Rowe |
| Issue date: | 12/15/1978 |
| From: | Noonan V Office of Nuclear Reactor Regulation |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML13319A640 | List:
|
| References | |
| FOIA-81-313 TAC-12237, NUDOCS 8110190351 | |
| Download: ML20031F203 (8) | |
Text
6 f * ** 04 UNIT E D STAT [S
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. I, NUCLEAR REGULATORY COMMisslON
$ Y.,.. t[.' ?
WASHINGTON, D. C. 20555 E.
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j EC 1 5 1978 I
MEMORANDUM FOR:
D. Eisenhut, Deputy Director Division of Operating Reactors FROM:
V. Noonan, Chief. Engineering Branch Division of Operating Reactors THRU:
B. Grimes, Assistant Director for Engineering and Projects -
Division of Operating Reactors
SUBJECT:
SUMMARY
OF RECENT ADVERSE STEAM l
GENERATOR OPERATING EXPERIENCE l
In accordance with your request, the Engineering Branch, Division of Operating Reactors, has made a summary of recent adverse steam generator operating experience at Point Beach Unit 1 Yankee Rowe, and Oconee Unit 1.
Also included in the summary is our assessment of each event and its safety significance.
N 4.g b
Vincent S. Noo an, Chief I
Engineering Branch Division of Operating Reactors
Contact:
J. Strosnider 49-28060
Attachment:
As state'd cc:
V. Stello, Jr.
B. Grimes l
l G. Knighton l
P. Check A. Schwencer l
D. Ziemann R. Reid-B. D. Li j
F. Almeter R. LaGrange C. Trammell M. Fairtile F. Burger J. Strosnider j
J. P. Knight R. Bosnak S. Pawlicki y
4DDELLaz-313 PDR
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POIfiT BEACH UNIT 1
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I A.1, May 24, 1978, Tube Leak Indication of a primary to secondary leak was noted on May 24,'
l 1978 in the Unit 1. A steam generator.
The initial leak rate e
of 8 gpd increased to almost 90 gpd by May 25 and the plant was shut down to perform stea'm gen 2rator repairs in conjunction l
with a maintenance outag'c originally scheduled for the Memorial Day weekend.
The leak test revealed one leaking tu' be originally reported as tube R44C58. An October 23, 1978 licensee event
_ update report indicated that the leaking tube had been mis-identiftad and was actually located at R44C35.
The mode of tube degradation was not conclusively determined.
Because of the originally indicated tube location, the Engineering Branch re-quested information regarding the possible relation of the leak to denting and requested the licensee to submit their S.G. ISI program planned for the September 29, 1978 refueling outage.
The licensee's response established that the leak was not' dent-ing related since the tube defei:t was located just above the ;
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tubesheet.
A.2.
_ September, 1978 Tube Leak.
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The Unit was shut down again on Septenber' 20, 1978 when a primary to secondary leak increased from 116 gpd 'to 500 gpd, exceeding the unit's 500 gpd technical specification leakage rate limit.
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The plant was shut down and the licensee began a refueling outage originally scheduled for September 29, 1978. Steam Senerator inspections and repairs were conducted during the shutdown.
l On October 5, members of the Engineering Branch along with Mr. C.
Trammell, the Project Manager, had a conference call with Point Beach to learn the specifics of the S.G. leak. The source of the leak was determined to be two tubes with cracks located within the thickness of the tubesheet.
In addition to the two leaking tubes, eddy current testing revealed four tubes in steam generator B with " deep crevice cracking" in excess of 50%. All of these tubes were plugged. All of the cracks were located approximately 17 inches from the top of the 23 inch tubesheet.
Early generation steam generators in which the tubes were not full depth expanded in the tubesheet may be susceptible to this '
type of cracking, tentatively attributed to caustic stress corrosinn cracking. Because of the constraint provided by the i
tubesheet; the deep crevice cracks are not considered a signif--
icant -safety concern during normal operation or postulated accident conditions.
l Table I outlines the sequence of the above events at Point Beach Unit 1.
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' k-TABLE I POINT BEACH UNIT NO. 1
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6/10/78 LER 3 1 Plant shutdown on 5/25/78 due to leak in S.G. A.
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- 2. Leaking tube incorrectly reported as R44C58.
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7/13/78, EB requested information regarding leak:
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.'l, 1.
Was 'the leak denting related?
I 2.
Submit 9/29/78 refueling outage S.G. ISI program for NRC comment.,
C.
8/18/78.Poin't Beach response to EB request 1.
Leak not denting related.
- 2., Proposed ISI program submitted.
I D.
9/20/78 LER 3
l 1.
L Plant shutdown 9/20/78 beca'use of leak in S.G. A.
2.
Plant started refueling previously scheduled for 9/29/78 1
3.
S.G. ISI performed
" Deep crevice" cracks detected.
E.
10/23/78 Updated LER - leaking tube plugged in 5/78 was actually tube R44C35.
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YANKEE R0WE i
During their November,1978 refueling outage Yankee Rowe performed 100% ECT inspections of steam generators No.1 and No.
4.
On
- Hovember 7 members of the Engineering Branch along with Mr. F. Burger had a conference call with Yankee Rowe to discuss their proposed 0
technical specifications. governing steam generator inspection and results of the inspections of steam generators 1 and 4.
The unit c
I was operating with a 125 gpd priAary to secondary leak in steam I
generator No.1 prior to the shutdown.
Results of the inspection revealed two tubes (N41 and N44) with through wall defects originating l
from the outside tube diameter (OD) approximately one half inch above 1
the tubesheet.
An additional 13 tubes in steam generator No.1 had j.
OD defects greater than 40% through wall. All of these defects were located 0.5 to 3.0 inches above the tubesheet.
Two tubes in steam generator 1 had OD degradation greater than 20% but less than 40%
through wall.
Twelve tubes with defects greater than 40% and 8 tubes with degradation -greater than 20% but less than 40% were reported in steam generator No. 4.
All defects were located within 0.5 inch to 4.0 inches of the tubesheet except one tube with a 67% through wall defect 27.0 incher above tha tubesheet and one tube with an inside surface ECT indication less than 20% through wall and 25.0 inches above the first support plate. The 67% through wall defect was believed.
to be a manufacturing defect. The inside surface degradation was un-
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explained but represents an isolated case. A 100% inspection of steam generators No. 2 and No. 3 was performed in July 1977 and resulted in the plugging of approximately 5 or 6 tubes in each steam generator.
No denting was observed in any of the steam generators. These inspac-tion results represent excellent baseline data for the plant and provide useful insight to the conditions existing in steam generators which have had relatively good operating experience. Results of these inspections were discQssed in the Engir eering Branch safety evaluation regarding Yankee Rowe technical specifi cations governing steam gener-ator inservice inspections dated December 5,1978. Table II and Tabic III summarize the results of the inspections in steam generators No.1 and No. 4.
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TABLE II 4
YANKEE ROWE Eddy Current Test Results
- 1 Steam Generator i
140 KHz test frequency November, 1978 y
ZETEC Inc, Inlet ROW COLUMN
% DEFECT-ORIGIN' LOCATION K
21 57
- OD 2" above tube sheet (ts) l l
J 24 54
- OD 3" above ts F
25 42
- OD 2" above ts l'
N 25 37 OD 2" above ts M
32 f:
OD 2" above ts
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t H
33 64 '
OD 1" above ts H
34 45
- OD 2" above ts i
l M
35 29 OD 2" above ts t
8 J
39 46
- OD 2" above ts L
41 44
- OD 1" above ts N
41 100 * /
OD 1/2" above ts t
O 43 51
- OD 1/ !" above ts J
- OD ~
1/2" above ts M
44 71
- OD 1/2" above ts 100*l s
l N
44 l
OD 1/2" above ts L
45 70
- OD 1/2" above ts l
- OD 1/2" above ts j
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- plugged any defect over 40%
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Eddy Current Test Results
- 4 Steam Generator 140 Kilz Test Frequency Noveraber, 1978 ZETEC Inc. '
Inlet ROW COLINN
% DEFECT ORIGIN LOCATION J
2 "
67 OD 27" above tube sheet (ts)
G 19 67
- OD 2" above ts I
22 under 20 OD 3" above ts K
23 48
- OD 3" above ts f
L 23 none (38% defect in 1975)
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26 none (34% defect in 1975) i I
27 under 20 ID 25" above first support j
J 27 under 20 OD 4" above ts l
K 27 32 OD 4" above ts L
28 under 20 CD 2" above ts I
K 29 under 20 OD 4" above ts 4
. OD 4" above is O
29 91 */
OD 2" above ts N
30 31
. OD 2" above ts i
l N
31 31 OD 2" above ts s
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35 29 OD 3" above ts f
K 35 37 OD 3" above ts
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L 36 under 20 OD 3 " above ts G
37 83 *'/
%" above ts
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J 37 63
- OD 3 " above ts G
38 21 OD 3" above ts
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OD 2 " above ts
'M 38 84 i
K 38 27 OD 4 " above ts L
38 51
- OD 4" above ts L
39 67
- OD 4" above ts O
41 75
- OD 2" above ts N
43 66 */
OD 2" above ts N
45 75
- OD 1" above ts plugged any defect over 40%
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- suspect manufacturer's defect l
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. C.
OCONEE UNIT 1 By letter dated October 19, 1978 Duke Power Company informed the
'NRC that two steam generator tube plugs had been lost at the Oconee Unit 1 Nuclear Power Plant and were possibly loose in the primary coolant system.
Details of the lost tube plugs incident are dis-cussed in a November 1,1978 safety evaluation.
i In addition to the lost plugs incident licensee event report number R0-269/78-24 from Duke Power Company, dated November 15, 1978, informed the NRC of the discovery of a large number of misplugged i
tubes at Oconee Unit 1.
The errors in tube plugging were discovered as a resul.t of leakage from a supposedly plugged tube during hydro-testing on October 3,1978, following the inservice inspection conducted during the refueling outage. The report indicated a total of 7 misplugged tubes.
The Engineering Branch has learned the following information by j
conference calls placed through Mr. M. Fairtile the Oconee Unit 1 4
Project Manager.
As a result'of the loose tube and mis-plugging incidents Duke Power 3
Company implemented the following QA improvements:
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.1.
All procedures improved in program.
2.
Use of standard techniques in tooling fixtures for tube identi-fication - this will eliminate tube plugging errors.
3.
Use of ECT template for identification of tubes to be plugged.
I 4.
Installation of ECT template on lower head tubesheet when necessary (not complete).
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Es'tablish better communication between upper and lower head crews I
and with outside of S.G. personnel.
6.
Build and OTSG mockup to facilitate training (not complete).
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7.
Expand personnel training.
8.
Clearly define role of first line supervisors in S.G. work.
J 9.
Improve management of vendor related activitic.
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10.
Improve health physics activities to keep down occupational exposure and reduce dose per man by better planning of work.
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-1 The NRC Office of Inspection and Enforcement (I&E) reviewed the QA changes and was dissatisfied with items 1 and 4.
Duke modified these j
items to incorporate I&E's comments.
The Office of 18E plans to audit the modified QA program at Oconee Unit 1 on December 7.1978 The results of this audit are to be foniarded to DDR in an I&E report as soon as they are available.
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