ML20247E119
| ML20247E119 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 05/06/1998 |
| From: | Polston S UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-98-1032, NUDOCS 9805180220 | |
| Download: ML20247E119 (5) | |
Text
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d o USEC A Global Energy Company -
May 6,1998 GDP 98-1032 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Paducah Gaseous Diffusion Plant (PGDP)
Docket No. 70-7001 Event Report ER-98-07 Pursuant to 10CFR76.120(c)(2), enclosed is the required 30-day written Event Report (ER-98-07) covering the failure of a 10 milliroentgen per hour (mR/hr) alarm in the C-300 Central Control Facility. The Nuclear Regulatory Commission (NRC) was notified of the event on April 7,1998.
Should you require further information on this subject, please contaci Larry Jackson at (502) 441-6796.
Sincerely, QI l
QI l
Steve Polston General Manager Paducah Gaseous Diffusion Plant
Enclosure:
As Stated l-cc:
NRC Region 111 Office NRC Senior Resident Inspector, PGDP 1
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l P.O. Box 1410, Paducah, KY 42001 45000y Telephone 502-441-5803 Fax 502-441580I hup #
.usu.com Offices in Livermore, CA Paducah, KY Portsmouth, OH Washington, DC ggy 11 S
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Docket No. 70-7001
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GDP 98-1032 Page1of4 i
EVENT REPORT ER-98-07 DESCRIPTION OF EVENT On April 6,1998, at approximately 1800 hrs., while conducting a quarterly test of the Criticality Accident Alann System (CAAS) for Building C-720, as required by Tecimical Safety Requirements (TSR) 2.6.4.1b-1, it was discovered that the 10 milliroentgen per hour (mR/hr) alarm (bell and light) located in the C-300 Central Control Facility (CCF) did not function as designed. On April 7,1998, at 2352 hrs., the Nuclear Regulatory Commission Headquarters office was notified of this event in accordance with 10CFR76.120(c)(2). (NRC Event 34034)
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On April 6,1998, troubleshooting was initiated to determine the cause for the 10mR/hr alarm failure.
It was determined that a J7 Amphenol connector, model number MS-3106A-24-19S, was missing a retaining ring which allowed connector pins responsible for transmitting the 10mR/hr alarm signal to break the required circuit. The purpose of the J7 Amphenol connector is to provide an electrical disconnect between the replaceable CAAS cluster and the fixed CAAS alarm circuit wiring. Without the retaining ring the plastic insert on the Amphenol connector slipped back into its holder, which precluded the connector from providing a reliable electrical connection. The relay responsible for initiating the C-720 CAAS cluster 10mR/hr alarm in the CCF, delivers a local 48-volt direct current (VDC) supply to detect a contact closure on the AL cluster. The failure of the J7 Amphenol to complete the circuit resulted in the failure of the 10mR/hr alarm in the CCF to function. During previous quarterly surveillance tests the 10mR/hr alarm in the CCF, functioned properly.
l Malfunctioning of the 10mR/hr alarm will prevent the CCF personnel from detecting when the CAAS cluster in C-720 is in alarm. However, local alarms would still alert workers of a criticality in the area being monitored by the C-720 CAAS cluster.
The C-720, J7 Amphenol connector was installed in 1995. When the Amphenol connector is attached to the CAAS cluster assembly the retaining ring is not visible without removing and disassembling the connector. Therefore, the presence of a retaining ring should be determined prior to installation. In this instance, this was not accomplished.
During the period July 1997 to November 1997, the Amphenol connector cables were changed on 31 of 33 CAAS clusters (three cables on each cluster) located throughout the plant due to heat related 1
deterioration of older cables.
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Enclosure i Docket No. 70-7001 GDP 98-1032 Page 2 of 4 During the cable assembly replacement, it was determined that cluster AL in C-720 and PORTA #1 in C-710 did not need replacement because the cables had been installed within the previous five years. To date, no other CAAS cluster Amphenol connectors have failed to maintain electricai continuity and the 10mR/hr alarms in the CCF have performed as designed during quarterly surveillance testing for all other CAAS clusters.
The criticality alarm homs and lights within the CAAS-alarmed area of Building C-720 performed their safety function, as required, at the time of this event. However, failure of the 10mR/hr alarm on the CCF console could have led to a noncompliance with the provisions ofIssue 50 of the " Plan for Achieving Compliance with NRC Regulation at the Paducah Gaseous DifYusion Plant (Compliance Plan)." This Compliance Plan issue contains justification for continued operation (JCO) without certain criticality alarms present provided personnel entering unalarmed buildings located in the evacuation area of an alarmed facility have a radio capable of receiving emergency information. In the event of a facility alarm, such as a CAAS alarm, a notification via all plant radio frequencies originates from the CCF. Without actuation of the 10mR/hr alarm CCF permnnel would be unaware of the CAAS cluster actuation and, thus, would not make the required notification by radio to personnel in adjacent, unalarmed, buildings. On April 6,1998, during the quarterly C-720 CAAS testing, the required plant announcements were made, including notification via all plant radio frequencies. Additionally, all employees within the 12-rad boundary area were required to wear a personal alarming dosimeter and would, therefore, have been alerted in the event of a criticality accident.
In 1995, the Amphenol connectors on the CAAS AL cluster, Building C-720, were the only CAAS associated connectors installed by a subcontractor. The rigors associated with work control, Engineering Specification Data Sheets (ESDS), Safety System inspection Plans, and the process of control of contractors performing nuclear services for Gaseous Diffusion Plants, were not in place.
Currently, all Amphenol connectors associated with the CAAS are being assembled and inspected by Plant Maintenance prior to installation by subcontractors.
The CAAS associated cables that were changed during the period July 1997 and November 1997, were constructed and assembled by Plant Maintenance and were subjected to the rigor, including inspections, currently required of safety systems and safety system component installation. On April 28,1998, all CAAS associated Amphenol connectors contained in the Plant Stores were inspected and it was determined that all connectors contained retaining rings. Therefore, the cable inspections conducted in 1997 and the recent Stores inspection provide valid sampling of the cables assembled by Plant Maintenance and provide a high degree of assurance that CAAS associated cables currently installed contained the retaining ring.
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Docket No. 70-7001 GDP 98-1032 Page 3 of 4 CAUSE OF THE EVENT A. Direct Cause The direct cause of this event was the failure of the C-300, CCF,10mR/hr alarm to actuate as a result of the J7 Amphenol connector's inability to maintain electrical continuity for those connector pins responsible for actuating the 10mR/hr alarm. The failure to maintain electrical continuity disrupted the electrical path to the 10mR/hr alarm in C-300.
B. Root Cause The root cause for this event was the failure to install a retaining ring on the Amphenol l
connector. The absence of the retaining ring led to an inability to maintain electrical continuity for those connector pins responsible for actuating the 10mR/hr alann.
C. Contributing Cause A contributing cause for this event was a failure to perform an inspection of the Amphenol connector at the time ofinstallation to ensure the presence of the retaining ring. If an inspection requirement had existed the probability for not recognizing the absence of the retainer ring is considered low.
CORRECTIVE ACTIONS A. Completed Corrective Actions i
- 1. On April 28,1998, all the Amphenol connectors associated with the CAAS contained in the l
Plant Store were inspected and it was determined that all contained a retaining ring.
l B. Planned Corrective Actions The failure of the Amphenol connector to maintain electrical continuity due to the absence of a retaining ring was determined to be an isolated occurrence. As a result, no further corrective actions are required.
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I Enclosure i Docket No. 70-7001 GDP 98-1032 Page 4 of 4 EXTENT EXPOSURE OF INDIVIDUALS TO RADIATION OR RADIOACTIVE MATERIALS None LESSONS LEARNED Although te 10mR/hr alann failure in this event was determined to be an i.solated occun'ence, any further 10mR/hr alarm failures will be evaluated to determine whether an adverse trend is developing.
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