05000317/LER-2002-004, Calver Cliffs Unit 1 Post-Accident Monitoring Instrumentation Not Seismically Connected
| ML023050015 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 10/28/2002 |
| From: | Nietmann K Constellation Energy Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER-02-004-00 | |
| Download: ML023050015 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3172002004R00 - NRC Website | |
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Kevin J. Nietmann Plant General Manager Calvert Cliffs Nuclear Power Plant Constellation Generation Group, LLC 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 410 495-4101 410 495-4787 Fax Constellation I
Energy Group October 28, 2002 U.S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
SUBJECT:
Document Control Desk Calvert Cliffs Nuclear Power Plant Unit Nos. 1 and 2; Docket Nos. 50-317 and 50-318; License Nos. DPR 53 and DPR 69 Licensee Event Report 2002-004 Post-Accident Monitoring Instrumentation Not Seismically Connected The attached report is being sent to you as required under 10 CFR 50.73 guidelines. Should you have questions regarding this report, we will be pleased to discuss them with you.
Very truly yours, KJN/ALS/bjd Attachment cc:
J. Petro, Esquire J. E. Silberg, Esquire Director, Project Directorate I-1, NRC D. M. Skay, NRC H. J. Miller, NRC Resident Inspector, NRC R. I. McLean, DNR
Abstract
On August 27, 2002 while reviewing a causal analysis, a condition was identified at Calvert Cliffs that could have prevented the Post-Accident Monitoring System from fulfilling its safety function.
Specifically, the review identified that loose pins on the cable connectors for the containment area radiation high range indicators could cause the channels to fail during a seismic event. This could result in the loss of Control Room indication of containment area radiation levels, required by Control Room Operators during accident situations, and could also have prevented the hydrogen purge isolation valves from shutting on a containment radiation signal. Evidence suggests that the condition existed during the time period from April 14, 2000 through May 20, 2002 when the connector pins were replaced and equipment tested satisfactorily. Failure of the connectors was attributed to inconsistent use of a connector extraction tool and approximately 20 years of unmonitored mechanical wear. Issue reports were initiated to periodically inspect the connectors for wear, and to ensure connectors are installed and maintained properly in the future. Several sets of connector extraction tools were purchased and made available for use. All instrumentation with this style connector was identified and repaired. Corrective Actions were established to address human performance errors.
NRC FORM 366 (7-2001)
(If more space is required, use additional copies of (If more space Is required, use addibonal copies of NRC Forn 366A) that the retention springs were missing. The associated vendor technical manual indicates that retention springs are to be used. Since the connector retention springs were missing, the engineering evaluation concluded that the connector for 2RI5317A/B would most likely become dislodged and the signal would be lost during a seismic event. The engineering evaluation only addressed Unit 2 since the issue with Unit 1 had not been identified at the time. Review of the Unit 1 repair maintenance order indicates that 1 R15317A was not damaged and 1 R15317B had a damaged retention spring. Since the retention spring for 1 R15317B was damaged, most likely the connector would become dislodged and the signal would be lost during a seismic event.
During review of the maintenance history for the subject instruments, evidence was discovered that suggests the condition existed as early as April 14, 2000. Specifically, on April 14, 2000 while Unit 1 was in a scheduled refueling outage, an issue was identified with unexpected Control Room alarms on 1 R15317B. During performance of troubleshooting on April 18, 2000, the associated maintenance order documents that the signal cable for 1 R15317B was loose, thus causing the alarms to come in. The maintenance order further states that the Unit 2 cable came out, causing Unit 2 alarms to come in. Unit 2 was operating in Mode 1 at the time.
Based on the above, the condition most likely existed from April 14, 2000 until May 2002 for Unit 1 and from April 14, 2000 until April 11, 2002 for Unit 2.
II.
CAUSE OF EVENT
The problem with the connectors was originally noted and documented on an issue report in April 2000. The causal analysis identified that the cables had become loose in their connectors due to approximately 20 years of unmonitored mechanical wear. The mechanical wear resulted from repeated disengagement/engagement operations performed to support maintenance and performance of periodic surveillance tests. The causal analysis also identified that the proper extraction tool, which is used to remove the connector pins, was not always used, increasing the wear on the connectors. Based on a review of the repair maintenance orders, the connectors became loose due to damage to and/or loss of the connector retention springs. The vendor's design qualification test for the instrumentation includes a discussion regarding aging of various components including the connectors. It notes that mechanical wear is the failure mechanism for connectors that will experience a large number of engagement/disengagement operations.
Therefore, the cause for failure of the connectors can be attributed to inconsistent use of a connector extraction tool and approximately 20 years of unmonitored mechanical wear.
Human performance errors also contributed to this event.
Specifically, personnel did not understand the importance of ensuring proper installation of the connectors with regards to satisfying full design requirements, e.g., seismic design requirements. As a result, the equipment was returned to service in a functional, but not operable condition.
During the 2001-01 audit period, assessors identified that human performance errors introduced during the performance of maintenance challenge the reliability and operability of plant systems and equipment. A root cause analysis was performed to address the issue. The root cause
(If more space is required, use additional copies of (if more space Is required, use additional copies of NRC Forn 366A) issue is "low" or "green" in accordance with Calvert Cliffs Nuclear Power Plant's Issue Reporting and Assessment procedure.
During the time period from April 14, 2000 through May 20, 2002 Channel B of the Unit 1 containment area radiation high range instrumentation should have been declared out-of-service and the associated Technical Specification action statement should have been entered, when the Unit was in the applicable modes.
During the time period from April 14, 2000 through April 11, 2002, Channels A and B of the Unit 2 containment area radiation high range instrumentation should have been declared out-of-service and the associated Technical Specification action statement should have been entered, when the Unit was in the applicable modes.
The subject event describes a condition prohibited by the plant's Technical Specifications. The condition existed for a time longer than permitted by the Technical Specifications required action completion time. Therefore, this event is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B) as a condition, which was prohibited by the plant's Technical Specifications.
IV.
CORRECTIVE ACTIONS
A.
All instrumentation with this style connector was identified and repaired.
B.
Four sets of extraction tools were purchased and made available for shop use.
C.
An issue report was initiated to create a preventative maintenance task to periodically inspect the connectors for wear.
D.
An issue report was initiated to ensure connectors are installed and maintained properly in the future.
E.
As the result of an audit, a root cause analysis was performed to address the human performance issues relative to this event.
V.
ADDITIONAL INFORMATION
A.
Affected Component Identification:
IEEE 803 IEEE 805 Component or System EIIS Funct System ID Post Accident Monitoring IP IP Radiation Indicator RI IP
(If more space is required, use additional copies of NRC Form 366A)
B.
Previous Similar Events
A review of Calvert Cliffs' licensee event reports over the past several years was performed.
The review did not identify any similar reportable events where the operability of the PAM instrumentation was challenged due to connector failures.