ML18066A377
| ML18066A377 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 06/19/1989 |
| From: | William Jones NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Rosenthal J NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| References | |
| AEOD-T910, NUDOCS 9901260464 | |
| Download: ML18066A377 (6) | |
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.__pFt MEMORANDUM FOR:
Jack E. Rosenthal, Chief Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Evaluation of Operational Data THRU:
George F. Lanik, Chief FROM:
SL'EJECT:
Reactor Systems Section GE and CE Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis ~nd Ev~luation of Operational Data William R. Jones
,r Reactor Systems *section GE and CE Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Evaluation of Operational Data INVESTIGATION OF CRACKED CONTROL ROD DRIVE SEAL HOUSING AT PALISADES Enclosed is my review of a series of operating events at Palisades Nuclear Plant involving cracked control rod drive seal housings occurfing between 1986 and 1988.
While the cause of the cracking is not completely understood, based on the uniqueness of the component involved in the failure and the lack of similar events, no additional AEOD action is recommended at this time.
Enclosure:
As stated cc w/enclosure
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William R. Jones*
Reactor Systems Section GE and CE Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Evaluation of Operational Data WLannina JRosenthal MTaylor ROAB R/F TNovals_ *~
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SUBJECT:
SUMMARY
AEOD TECHNICAL REVIEW REPORT Palisades 50-255 Consumers Power Co.
Combustion Engineering/Bechtel TR REPORT NO.:
AEOD/T910 DATE:
June 19, 1989 EVALUATOR/CONTACT:
W. R. Jones INVESTIGATION OF CRACKED CONTROL ROD DRIVE SEAL HOUSINGS AT PALISADES This technical review documents the results of an evaluation of events at Palisades involving control rod drive (CRD) seal housing cracking occurring between 1986 and 1988.
The seal housing is located near the top of each of the 45 Palisades CRDs and contains the seal through which the CRD drive shaft penetrates the reactor coolant system (RCS) pressure boundary.
It thus forms part of the RCS boundary.
During the interval from 1986 to 1988, several of' these housings developed indications of cracks.
In addition to Palisades, CRD seal housings of this type are used only at Ft.
Calhoun.
Sequence Codin~ and Search System (SCSS) and Nuclear Plant Reliability Data System (NPRDS) searches were performed for CRD housing leaks.
No si~ilar events were found for any pressurized water reactor.
In addition, discussions have been held with NRR personnel and NRC correspondence relative to this issue has been reviewed.
It has been determined that the events are limited to Palisades. While the root cause is not completely understood, it is believed to be plant specific.
Based on this review, no additional AEOD action is recommended at this time.'
DISCUSSION In December, 1986, an small (appr~ximately 0.12 gallon per minute) RCS leak developed at Palisades. A control rod drive was observed leaking* during containment entry. Subsequently, dye penetrant inspection identified positive circumferential crack indications around the inner dia~eter of a seal housing where the motor tube sleeve enters the housing.
(See Figure 1 - CRD mechanism.)
Becau.se of this positive indication, an additiona 1-six sea 1 housings were tested and no crack indications were found.
The failed housing was sent tc the vendor, Combustion Engineering (CE), for examination~ The seal housing was one of a total of three 3 housings which made up a single manufacturing lot.
In January 1987, the two other seal housings in the same manufacturing lot as the failed housing were dye penetrant tested. Both housings showed indications similar to the housing which had failed on the reactor in December, 1986.
Based on these results, an additional five housings were removed from the reactor and tested with no crack indications found.
During September of 1988, six housings were removed from the reactor and examined.
Test results indicated that five of these six showed positive indications similar to those previously found.
One of these exhibited a
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PALISADES CONTROL ROD DRIVE MECHANISM po~~tive 360 degree crack indication. Because of these findings all remaining (39 of a total of 45) CRD drive seal housings on the reactor at that time were tested. Six of these remaining 39 housings showed positive indications.
Thus, in September, 1988, a total of 11 of the total 45 housings showed indications of cracks. During the period between the event in 1986 and that of 1988, 13 housing had been tested with negative results. The re~test of 10 these housings in 1988 showed no indications of cracking.
The other 3 were not in service and were not re-tested.
CE determined the cause of the cracking to be transgranular stress corrosion cracking.
The initiating factor could not be determined.
There was evidence of a contaminate being present on the cracks: The specific contaminant could not be determined.
Reference 3 points out that although no traces of corrosive contaminant were found, the vendor believes that the cause of the cracks is a contaminant that was probably introduced during prior CRD maintenance.
The licensee performed complete repair of the housings with crack indicatio~s.
In addition to complete repair of CRD seal housings with indications, the licensee developed an inspection program to inspect housings in the future to ensure that any cracks which propagated would be detected in a timely manner.
Based on the licensee's assessment of the safety impact of these events, a complete failure of a single housing would result in a small break.LOCA equivalent to a 2.25 inch diameter pipe. Multiple failures, although unhkely, are bounded by the plant's LOCA analysis.
Searches of both the SCSS and NPRDS databases were conducted.
Onl~ Palisades events were found.
Only one other plant, Ft Calhoun, has this type CRD seal housing.
No events of this type have occurred at Ft Calhoun.
FINDINGS
- 1.
The cracked CRD seal housings which occurred at Palisades were due to transgranular stress corrosion cr~cking, possibly caused by a contaminate introduced during maintenance.
- 2.
Only one other site (Ft. Cahlhoun) has the type of CRD housing used at Palisades.
No similar e~ents have occurred at Ft Calhoun.
3 The propagation mechanism appears slow and the litensee has a program to inspect CRD seal housing in order to detect crack indications early.
CONCLUSION Based on finding no simtlar events at other PWRs, the uniqueness of the component which developed cracks at Palisades (only used at Palisades and Ft Calhoun with no similar events at Ft Calhoun), and the thorough evaluation by the licensee and the vendor and the NRR efforts outlined in reference 3 regarding the specific Palisades events, it is concluded that no additional
- AEOD action is required at this time.
_.,/ References
- 1.
Palisades LER 255/86-040, Rev.03, Crackling of Cpntrol Rod Drive Seal Housing, December 2, 1988.
- 2.
Region III Morning Report item October 31, 1988
- 3.
NRC memorandum, Jaime Guillen to Carl H. Berlinger,
Subject:
CROM Seal Housing Cracks at Palisades (OGCB 88-102), March 2, 1989
.Ii MEMORANDUM FOR:
Jack E. Rosenthal, Chief Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Evaluation of Operational Data THRU:
George F. Lanik, Chief Reactor Systems Section GE and CE Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Ev~luation of Operational Data FROM:
William R. Jones Reactor Systems Section GE and CE Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Evaluation of Operational Data SUEJECT:
INVESTIGATION OF CRACKED CONTROL ROD DRIVE SEAL HOUSING AT PALISADES Enclosed is my review of a series of operating events at Palisades Nuclear Plant involving cracked control rod drive seal housings occurring between 1986 and 1988.
While the cause of the cracking is not completely understood, based on the uniqueness of the component involved in the failure and the lack of similar events, no additional AEOD action is recommended at this time.
Enclosure:
As stated cc w/enclosure T. Novak E. Jordan Distribution:
Central File:s MWilliams VBenaroya EJordan GLanik KB lack SEE PREVIOUS CONCURRENCE*
William R. Jones Reactor Systems Section GE and CE Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Evaluation of Operational Data WLannino JRosenthal MTaylor ROAB R/F TNova Is.*~
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