ML20248M180
| ML20248M180 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 06/10/1998 |
| From: | Pulley H UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-98-1040, NUDOCS 9806150116 | |
| Download: ML20248M180 (5) | |
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USEC A Global Energy Company 1
June l'0,1998 GDP 98-1040 United States ' Nuclear Regulatory Commission.
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Attention: Document Control Desk
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Washington, D.C. 20555-0001 Paducah Gaseous Diffusion Plant (PGDP)
Docket No. 70-7001 Event Report ER-98-11 Pursuant to 10 CFR 76.120(d)(2), enclosed is the required 30-day written report for the loss of air capacity required for Criticality Accident Alarm System (CAAS) audibility. This was initially
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reported on May 12,1998 (NRC No. 34212).
Commitments contained in this submittal are identified in Enclosure 2. Any questions regarding this matter should be directed to Larry Jackson at (502) 441-6796.
Sincerely, r
,41 ard > ey General Manager Paducah Gaseous Diffusion Plant
Enclosures:
As Stated
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cc:
NRC Region 111 Office NRC Resident Inspector - PGDP
.9906150116 980610
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PDR ADOCK 07007001 c
PDR g
- " ' ' % +. I3 P.O. Box 1410, Paducah, KY 42001 Telephone 502-441-5803 Fax 502-441-5801 http://www.usec.com j
Offices in Livermore, CA ' Paducah, KY Portsmouth, OH Washington, DC
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Docket No. 70-7001 GDP 98-1040 Page1of3 EVENT REPORT ER-98-11 l.
DESCRIPTION OF EVENT-
. On May 11,1998, at 1245 hours0.0144 days <br />0.346 hours <br />0.00206 weeks <br />4.737225e-4 months <br />, a partial failure of the plant air system occurred when the No.1
. Worthington air compressor at C-620 tripped due to a high discharge air temperature. The compressor was off-line for approximately five minutes and was restarted. A second trip occurred l[
at 1256 hours0.0145 days <br />0.349 hours <br />0.00208 weeks <br />4.77908e-4 months <br />. The compressor was restarted, after being off-line for approximately 30 seconds.
The partial failure of the plant air system caused all Criticality Accident Alarm Systems (CAAS) whose alarms are supplied by plant air to be declared inoperable. The inoperability of the CAAS was E
based on inaudibility, due to inadequate plant air capacity to the CAAS building horns. CAAS
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detectability was not affected. On May 12,.1998, at 1239 hours0.0143 days <br />0.344 hours <br />0.00205 weeks <br />4.714395e-4 months <br />, the Nuclear Regulatory Commission Headquarters office was notified of this event in accordance with 10 CFR 76.120 (c)(2)
. (Reference NRC Event Notification 34212).
- Dry compressed air is used at the Paducah Gaseous Diffusion Plant (PGDP) to operate pneumatic instruments, controllers, and valves for plant processes. Air is also used for plant support production operations, steam plant operations, test facilities, and maintenance functions. Dry compressed air is supplied from three buildings (C-600, C-620, and Cf 35) and an auxiliary supply is located in C-607. The air compressor facilities may be operated separately or together to maintain air supply
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to the distribution headers. Dry compressed air is used as the primary motive force to sound i
~ building horns associated with the CAAS. The requirements for compressed air capacity relative to the CAAS has been assessed in Engineering Notice (EN) EN-C-822-98-027, Rev. O, effective
' April 3,1998. Plant Utilities Operations issued Long Term Order (LTO) C600-98-01, Rev.2, dated May 5,1998, to assure the initial conditions of the EN, including CAAS operability, are maintained.
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Historically, trips of this type were not unusual during high ambient temperature. Prior to the completion of the above EN, which defined the air supply capacity required to maintain CAAS audibility, the response to a compressor trip was simply to restart it, without adequate awareness of the potential impact on CAAS audibility during the trip. The plant is taking aggressive actions to restore to service air compressors currently not available, i
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CAUSES OF EVENT a
. A.. Direct Cause -
The direct cause of.the loss of air capacity to the CAAS horns was the tripping of the 1
.Worthington air compressor due to high discharge air temperature. The equipment operated j
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i Docket No. 70-7001 l
GDP 98-1040 Page 2 0f 3 as designed, tripping after reaching the established trip point due to load and high ambient temperature.
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Root Cause j
The root cause of the trip was a temperature trip point for discharge air that was set too conservatively, considering the load, the demand to be on-line to meet air capacity requirements, and the ambient air temperature. About three years ago, the trip point for this compressor was lowered approximately twenty degrees. Prior to that time, the compressor had
. operated at the higher trip point with no observable adverse impact to the equipment. This change in trip point was made during the plant-wide equipment calibration initiative. During j
the calibration initiative, the blind switch which controls the compressor discharge temperature
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trip point was calibrated to trip at a discharge temperature of 344 F. Prior to this time, the i
I blind switch was adjusted until associated monitoring : instrumentation indicated 344 F during a trip. A reading of 344*F on the monitoring instrumentation corresponds to an actual compmssor discharge temperature approximately twenty degrees higher. Corrective Action No.
I will have Engineering provide a technical basis for the high discharge air temperature trip point value for the Worthington compressor to Operations. Based on the results of Corrective Action No.1, Operations will adjust the high discharge air temperature trip point of this compmssor to reduce the risk of the Worthington compressor tripping prematurely (Corrective Action No. 2).
Reliance on the air plant for CAAS audibility will be reduced in the future by the installation of air accumulators and air distribution piping that will be dedicated to supplying compressed air to the CAAS homs.
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CORRECTIVE ACTIONS j
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By June 18,1998, Engineering will provide to Operations a technical basis for an increased value for the Worthington compressor high discharge air temperature trip point.
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By July 20,1998, Operations will adjust the Worthington compressor high discharge air temperature trip point based on the technical basis provided by Engineering in Corrective Action No.1.
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EXTENT OF EXPOSURE OF INDIVIDUALS TO RADIATION OR TO RADIOACTIVE MATERIALS None
Docket No. 70-7001 GDP 98-1040 Page 3 of 3 LESSONS LEARNED To maintain the required air capacity for safety systems such as CAAS, trip points should be
. determined with a sound technical basis and should consider load, demand to be on-line, and
- ambient air temperature, i
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Docket No. 70-7001 GDP 98-1040 Page1of1 List of Commitments Event Report ER-98-11
- 1. By June 15,1998, Engineering will provide to. Operations a technical basis for an increased value for the Worthington compressor high discharge air temperature trip point.
- 2. By July 20,1998, Operations will adjust the Worthington compressor high discharge air temperature trip point based on the technical basis provided by Engineering in Corrective Action No.1.
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