ML20203D329
| ML20203D329 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 02/20/1998 |
| From: | Polston S UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-98-1012, NUDOCS 9802260025 | |
| Download: ML20203D329 (3) | |
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y w-USEC A Global Energy Company February 20,1998
- GDP 981012 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Paducah Gascous Dihsion Plant (PGDP)
Docket No. 70-7001 Event Report ER-98-03 Pursuant to 10 CFR 76.120(d)(2), enclosed is the required 30-day written report for the C-333 CAAS inoperability event, which resulted from the inadvertent continuous sounding of the C-333 building howlers. This was initially reported on January 23,1998 (NRC No. 33591). Trouble shooting is continuing and a revised report will be issued by March 20,1998, to include the root cause and currective actions to prevent recurrence.
Any questions regarding this matter should be directed to Larry Jackson at (502) 441-6796.
Sincerely, Steve Polston General Manager Paducah Gaseous Diffusion Plant Enclosures I
cc:
NRC Region 111 Office g'y ';
NRC Resident Inspector-PGDP (Elll[lN[h, 9002260023 990220 sull d
PDR ADOCK 07007001
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P.O. Box 1410. Paducah, KY 42001
_ Telephonc $M-4415803 Fax 502-441-5801 http://www.usec.com s
Offices in IJvermore, CA Paducah, KY Portsmouth ""i Washington, DC u.
I Docket No. 70 7001 GDP 981012 Page 1 of 2 EVENT REPORT ER 98-03 DESCRIPTION OF EVENT On January 23,1998, at 0900 the C-333 area control room (ACR) attempted to signal operators in b
the building to call the ACR by sounding a thort blast on the building howlers. This is a rout method of sign 9 ling building personnel to come to, or call the ACR When the ACR ope.ator pressed the howler actuator button, the button stuck in the "on" position and the howler sounded continuously. The Plant Shift Superintendent (PSS) was immediately notified and electrical maintenance was called to respond to the building to stop the howler's sounding. The PSS became concerned about the audibility of the building Criticality Accident Alarm System (CAAS) and declared the building CAAS inoperable at 0917. The general Limiting Conditions for Operation (LCO) actions under Technical Safety Requirements (TSR) 2.4.4.2b and 2.2.4.3b were taken, as required.
At 0925, Electrical Maintenance personnel silenced the howlers and at 0942 the CAAS was declared operable by the PSS and the LCO actions lifted. The building howler system is an "AQ" system.
Its safety function is to provide notification ofincidents requiring evacuation of personnel.
At approximately 1100 on January 23,1998, the PSS requested the CAAS system engineer to initiats an operability evaluation on the howler failure. This evaluation (No. OE-C-822-98-001) concluded that the continuous sounding of the building howler system provided a significant increase in the background sound pressure levels on the C-333 cell floor for approximately 25 minutes. During this period, the ability of the CAAS horns located on the C-333 cell floor to meet requirement 4.4.1 of ANSI /ANS-8.3-1986, would be significantly degraded and thus, the ability of the system to perform its intended safety function (to alert building personnel of a criticality) would be marginal. The OE stated that the ability of the C-333 ground floor CAAS horn system was not adversely affected by the cell floor building howler sounding. Ability of the CAAS to detect a radiation event and sound local horns was not affected by this event.
On January 24,1998, at 0241 CST the PSS notified the NRC licadquarters operation office of the event in accordance with 10CFR76.120(c)(2) and NRC No. 33591 was assigned t'
- vent.
The process building howlers are used te initiate evacuations of building personnel, in the event of a criticality accident, the building howlers would be actuated by the building ACR operator to augment the audibility ftmetion of the CAAS local horns to ensure that all building personnel are alerted and can evacuate in a timely manner. The continuous sounding of the howlers is the " alert sigmtl," which directs personnel to evacuate the building immediately and to listen to the plant public
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4 Docket No. 70-7001 GDP 98-1012 Page 2 of 2 address system for further instructions. The operability of the howlers is verified at least semi-annually. During the investigation of this event, a search of the problem reporting data base was conducted to determine if similar events had occurred in the past. A problem report (PR-CO 97-5034) described the same situation in C-333 on September 8,1997, where the cell floor howlers stuck on for approximately three hours. The proper LCOs were entered due to concerns about CAAS audibility, but the event was not reported to NRC, as required. This discovery was discussed with the NRC Resident. This issue will be corrected through the implementation of SCAQ Action Plan No. PR CO 97-6836. This SCAQ addresses previous failures to make notifications to NRC.
CAUSE OF EVENT A. Direct Cause The direct cause is attributed to the failure of the building howler system. This failure caused the howlers to sound continuously for 25 minutes, which degraded the audibility ftmetion of the building CAAS.
During trouble shooting of the howler electrical system, a light bulb on the evacuation system electrical control panel (attack and alert signaling system) had come loose from its st :ket and was laying such as to make contact with the socket base and ground. This ground by itself would not cause the failure, since the system is isolated from ground. Additional electrical trouble shcoting is continuing to locate the additional ground and determine the cause of the failure.
- 13. Root Cause The root cause of this failure cannot be determined until the electrical system trouble shooting is completed and analyzed. A revised report will be issued by March 20,1998, to include the root cause and corrective actions to prevent recurrence.