ML20247E209
| ML20247E209 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 05/17/1989 |
| From: | Trevors G NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CNSS897239, NUDOCS 8905260168 | |
| Download: ML20247E209 (3) | |
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CNSS897239 May 17, 1989' U.S. Nuclear Regulatory Commissiua Attention: Document Control Desk Washington, DC 20555 Subj ect:
NPPD Response to Notice of Violation - NRC Inspection Report No. 89-09 Gentlemen:
This.1 etter is written. in response to your letter dated April 25, 1989, transmitting. Inspection Report 50-298/89-09.
Therein you indicated that certain of our activities were in violation of NRC requirements.
Following is a' statement of the violations and our response in accordance with 10CFR2.201.
Statement of Violation 10CFR Part 50, Appendix B, Criterion XVI, requires that measures be established to assure that conditions adverse to quality, such as failures, malfunctions, deficiencies, deviations, defective material and equipment, and nonconformances are promptly identified and corrected.
In the case of significant conditions adverse to quality, the measures shall assure that the cause of the condition is determined and corrective action taken to preclude repetition.
Contrary to the above, Emergency Diesel Generator (EDG) No. 1 at Cooper Nuclear Station failed on January 17, 1989, due to a cracked fitting in the control air system, and the licensee did not take adequate corrective action to preclude repetition. EDG No. 1 failed again on February 13, 1989 when the replacement fitting, a thinner walled component than that which g
&4) had been repisaed, was found cracked during an operational test of the M$
diesel.
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&n Reason For The Violation (Do jld The reason for the violation was an inadequate root cause evaluation of the
-o January 17 failure in that vibration resistance was not recognized as a
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critical characteristic of the replacement control air system fitting.
The I
y January 17 failure was attributed to interferences between the tubing attached otr -
to the failed fitting which had eventually caused it to become overstressed.
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-The interferences were removed, the fitting was replaced, and the EDG was I
returned to an operable status.
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e CNSS897239 May 17, 1989 l
Page'2 l
The original installation of the failed fitting, and its function related to vibration resistance, were the subject of a Nonconformance Report (NCR) issued in 1974.
However, the event associated with the 1974 NCR was not discovered during the root cause analysis performed as a result of the January 17 l
failure.
Since the selection of the replacement fitting overlooked vibration l
resistance as a critical characteristic, the second failure occurred.
Corrective Steps Which Have Been Taken And The Results Achieved 1.
Subsequent to the February 13, 1989, fitting failure, immediate corrective actions included modifying the tubing configuration to eliminate the need for the fitting, change out of tubing in the critical air header, and implementing other modifications to increase the vibration resistance of the control air system tubing on both EDGs.
These modifications provided for reliable EDG operation for the remainder of the operating cycle.
2.
During the period of March 15 through March 17, 1989, station engineering and management personnel attended training on technical root cause and failure analysis.
The training was presented on site by Failure Prevention, Inc.
This training discussed depth of root cause analyses, common failure mechanisms, and failures which have recently been of primary concern at nuclear power generating facilities.
For the short term, the EDG failure and the training provided have increased the awareness of station engineering personnel as to the information required to adequately identify failure mechanisms and to better evaluate failure modes.
Corrective Steps Which Will Be Taken To Avoid Further V!olation 1.-
As a planned part of the current (1989) refueling outage, the following EDG tubing and control component modifications are currently in progress:
- 1) Critical components and instrumentation for EDG support systems are bcing moved from the EDGs to seismically qualified floor-mounted panels,
- 2) All critical stainless steel, copper, er carbon steel tubing is being replaced with stainless steel tubing, 3) Tubing supports are being replaced with supports which are more resistant to fretting interaction with the tubes, and 4) The new tubing spans will be verified to be within pre-determined specifications for required seismic and engine vibration constraints. These modifications will be completed on both EDGs prior to plant startup from the 1989 Outage.
2.
Contract engineering services have been obtained to reformat and enhance the computerized NCR database. This effort includes a detailed review of the data for all NCR records to ensure that it accurately reflects the system or component which was effected, as well as the required failure and root cause information.
In addition, the information will be revised, as required, to conform to a set of standard guidelines.
This will allow station engineers to manipulate the data more efficiently and effectively during future root cause analyses.
The scheduled completion date for this task is September, 1989.
m l-CNSS897239-May 17, 1989 l:
Page'3 l
l; 3.
Parallel to the NCR database upgrade effort, an Engineering Department Instruction'for document-research.will be issued.
This instruction will-
. provide general search methods'and guidelines for the review of industry l
experience databast.9 and station computer files..The NCR database document research methodology will be incorporated into the instruction.
by September, 1989..
4 The root cause' analysis program will-be revised to include requirements for. evidence. preservation, guidelines for failure mode identification, instructions for root cause determination, and additional training for engineering and management personnel.
In addition, Cooper: Nuclear' Station Engineering will: purchase and maintain investigative tools to support these activities. The scheduled completion date for this task is October, 1989.
Date When Full Compliance Will Be Achieved
- The corrective' steps noted will be implemented on the dates specified herein, with full compliance, achieved by October,.1989.
If you have any questions regarding this response, please contact me or G. R. Horn at the site.
Sincerely, G. A. Trevors Division Manager Nuclear Support GAT:kg cc:
U.S. Nuclear Regulatory Commission Region IV Arlington, TX NRC Resident Inspector Cooper Nuclear Station ir
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