ML20236V665
| ML20236V665 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 07/31/1998 |
| From: | Pulley H UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-98-1057, NUDOCS 9808040126 | |
| Download: ML20236V665 (4) | |
Text
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! L USEC r
. A Global Energy Company l
July 31,1998 l
GDP 98-1057 United States Nuclear Regulatory Commission l
Attention: Document Control Desk Washington, D.C. 20555-0001
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Paducah Gaseous Diffusion Plant (PGDP)
Docket No. 70-7001 Event Report ER-93-19 i
Pursuant to SAR Section 6.9, Table 1, Criteria J2, enclosed is the required 30-day written event report covering the actuation of the water inventory control system (WICS) in Building C-337-A.
l The Nuclear Regulatory Commission (NRC) was notified of the event on July 6,1998 (NRC No.
l 34483). This was considered an isolated incident; therefore, a list of commitments are not included in this report.
Any questions regarding this matter should be directed to Larry Jackson at (502) 441-6796, l
Sincerely, I
I I
loward Pulley y General Manager Paducah Gaseous Diffusion Plant i
Enclosure:
As Stated f
cc: NRC Region 111 Office NRC Resident Inspector-PGDP I
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9000040126 990731
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,o P.O. Box 1410, Paducah, KY 42001 Telephone 502-441-5803 Fax 502-441-5801 http://www.usec.com Offices in Livermore, CA Paducah, KY Portsmouth, OH Washington, DC
l Docket No. 70-7001 l
GDP 98-1057 Page1of3 l
EVENT REPORT ER-98-19 DESCRIPTION OF EVENT On July 6,1998, at approximately 1015 hrs., a high primary condensate alarm (water inventory control system [WICS]) was received in the operations monitoring room (OMR) on autoclave position 1 East, Building C-337-A. The operators responded in accordance with applicable procedures, jetted and opened the autoclave, and placed the autoclave into a safe condition. All safety systems performed, as designed. At approximately 1017 hrs., the Plant Shift Superintendent (PSS) declared autoclave position 1 East inoperable. On July 6,1998, at 2200 hrs., the Nuclear Regulatory Commission Headquarters (NRC-HQ) office was notified of the event in accordance with Safety Analysis Report, Section 6.9, Table 1, Criteria J.2.
I An investigation team was established to determine the cause for the event. Autoclave position 1 East hadjust concluded a feed cycle and was between feedings when the steam controller operational settings were reconfigure by the Systems Engineer (SE). The autoclave was reloaded with a cylinder and prepared for another feed cycle. The SE was obsuving cylinder heating by viewing the autoclave pressure and temperature recorded in the OMR to assure new operational settings on i
the steam controller did not negatively impact operation of the autoclave. The SE observed that the autoclave steam pressure was slightly different from the optimum or ideal. The differing autoclave f
pressure indicated the need for a steam controller gain adjustment, which is an operational setting.
l The SE, with permission of the Operations personnel, queried the steam controller by placing the i
controller in the " read" mode to determine whether the gain value was adequate. Querying the steam
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controller is not considered operating equipment, but is deemed to be monitoring the equipment because this activity does not effect the controller's operation. While in the " read" mode, the controller continues to monitor input signals and controls the output signals. However, no values can be adjusted while in this mode. While exiting the " read" mode, the SE unknowingly and inadvertently depressed the " automatic / manual" button, one of six T u: tons located on the steam controller keypad. This placed the steam controller in " manual" mode. vvhen in the " manual" mode steam input into the autoclave is limited to a constant rate.
l Steam input into the autoclave is dependent upon cylinder heating demand and varies throughout the heating cycle. Initially the heat demand is great, consistently requiring 100 percent or 4 psig steam pressure. As the cylinder begins to heat up, the demand for heat begins to slightly decay until the melting point of uranium hexafluoride (UF ) is approached. The heat demand increases 6
significantly as the melting point is approached, and is required for the phase change from solid to liquid UF.. While approaching the melting point, the steam control system requires the capability I
of rapid change to provide a large amount of steam to drive the phase change of UF. from solid to l
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Docket No. 70-7001 1
GDP 98-1057 Page 2 of 3 1
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liquid. Beyond the melting point, the demand for heat decays to a constant rate while UF. remains in the liquid state.
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The steam controller was inadvertently placed in " manual" mode between initial heat-up and melting point; therefore, when the melting point was approached the control system was unable to provide sufficient steam pressure and heat load to the cylinder. The insufficient heat and steam pressure in l
l the autoclave resulted in the loss of motive force (positive pressure) which helps expel condensate out the autoclave drain. The assistance from the steam pressure to expel condensate from the autoclave is an intrinsic feature of the autoclave. The condensate accumulated to the point where the WICS actuated, performed as designed, isolating the autoclave from additional introduction of water.
This event demonstrates a broad, plant-wide issue concerning " management oversight and control of work." This issue is also a factor in Notice of Violation (NOV) 98009-02, PGDP NRC Inspection l
Report 98011 - Exit Meeting Summary, and is a recurring concern from previous plant issues. Plant management recognizes this plant-wide concem and has formed a management team to investigate the root cause and develop corrective actions to prevent recurrence. Plant management has characterized this issue as a Site-Wide Significant Condition Adverse to Quality (SCAQ-S). The I
investigation and corrective action plan will address Potential Notice of Violation (POV) contained in PGDP NRC Inspection Report 98011 - Exit Meeting Summary, including concerns with conduct l
of Operations control of work.
The safety significance of this event is negligible because the function of the safety systems was met.
However, ongoing concerns with oversight and control of operations will be expeditiously addressed. The safety system performed as designed.
1 CAUSE OF EVENT i
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A. Direct Cause I
The direct cause for the WICS actuation was the presence of condensate due to the loss of steam pressure. The lack of heat and steam pressure in the autoclave resulted in loss of motive force (positive pressure), which is an intrinsic feature of the autoclave that helps expel condensate from the autoclave drain.
Docket No. 70-7001 GDP 98-1057 Page 3 of 3 B. Root Cause The root cause for this event was the accidental depressing of an incorrect control button located on the steam controller keypad. The size of the buttons on the keypad are smaller than those on a touch-tone telephone which led to depressing the incorrect button.
CORRECTIVE ACTIONS A. Completed Corrective Actions
- 1. On July 8,1998, Commitment Management published a synopsis of this event in a plant-wide, electronic media (InsideP) to emphasize the consequences of human error.
- 2. On July 10,1998, Engineering issued interim guidance p.chibiting Systems Engineers having contact with autoclave facilities from querying steam controllers while the autoclave is operating.
- 3. On July 29,1998, Operations enhanced the awareness of Operations oversight / control of activities and issues in the Daily Communication and Teamwork (DC&T) meeting.
B. Planned Corrective Actions
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None. This is an isolated incident involving a WICS actuation as a result of accidentally
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depressing an incorrect button on an autoclave steam controller keypad.
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EXTENT EXPOSURE OF INDIVIDUALS TO RADIATION OR RADIOACTIVE MATEllI ALS None LESSONS LEARNED Prompt investigations, as in this event, led to a self-identif'ied human error.
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