ML20059A012
| ML20059A012 | |
| Person / Time | |
|---|---|
| Site: | Westinghouse |
| Issue date: | 12/08/1993 |
| From: | Goodwin W WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| EKR93172, NUDOCS 9312290140 | |
| Download: ML20059A012 (4) | |
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Westinghouse-Commercial Nuclear orawer n Electric Corporation Fuel Division fgj$'32eE s'
EKR93172 y
December 8, 1993 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555
Dear Sir:
Westinghouse Electric Corporation hereby provides a 30 day _ followup l
report in accordance with the reporting requirements
_of 10CFR70. 50 (c) (2 ). The initial report was made by telephone and FAX in accordance with the requirements of 10CFR70.50(b) (4).
A description of the event,
- cause, location, date,- time-and-
]
exposure information are contained in the attachment to this letter.
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The material involved was uranium dioxide powder enriched to less than 5 weight percent in the U-235 isotope.
l A Root Cause Analysis Team was formed to investigate the event and l
to identify Causal Factors.
As indicated in the attachment, i
initial indications pointed to an oxidation of uranium dioxide powder as the cause of the event.
However, the Root Cause Analysis Team identified hydrogen as'an additional contributing factor in-the fire.
Although the event is' still under investigation, the following probable Causal Factors have been identified:
1.
ADU Conversion Line 4 began producing low bulk-density powder l
shortly before the fire.
.l 2.
The Calciner Discharge Powder Sensor failed to stop the first discharge screw when there was an absence of powder, thus
-i breaking the powder seal. This is attributed to the low bulk -
-i density. powder in the system._ The sensor is a paddle-type i
torque-sensing device which stops operatio'n of - the first l
discharge screw in the absence of powder.
However, it is j
somewhat sensitive to changes in powder characteristics.
Low j
-bulk-density powder tends to be less flowable and will adhere
-l to.the paddles.. When this occurred, the probe l sensed that:
powder was present and allowed the_first discharge screw 1to continue operation, eventually breaking the seal.
3.
.The high-l'evel probe for the powder-receiving polypack did.not activate, allowing'the polypack to overfill into the chute.
j his ultimately allowed UO2 to oxidize to U308 because more 1
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powder was exposed to the air that leaked into the system (see Item 4 below).
4.
The gasket seal for the polypack did not seal properly, allowing air to enter the system.
5.
The suction produced in the Fitzmill Product Hood by the ventilation system helped to move hydrogen through the opening
-1 in the powder seal to the opening of the Fitzmill discharge chute.
The hydrogen, and oxygen from the air, ignited upon contact with the hot UO2/U308 powder.
The ADU Conversion Quality Action Group was tasked to. review the report from the Root Cause Analysis Team and to develop corrective actions based upon the Causal Factors.
The line is currently shut down until the Team's recommended restart actions are completed, including (1) Developing and implementing a plan to correct the low bulk-density powder
- problem, (2)
Changing out the Calciner Discharge Powder Sensor and adding an interlock to stop the first discharge screw after one minute of continuous operation and an audible alarm to signal the operator to check the powder seal, (3) i Replacing the existing polypack level probe, (4) Replacing the polypack gasket with a new prototype seal, and (5) Reducing the ventilation on the system.
Additional corrective actions will be pursued, as appropriate, and documented for review by NRC Region II inspectors during routine compliance inspections.
An inspection was also performed for similar conditions on the other operating ADU Conversion lines.
This evaluation confirmed that the low bulk-density problem was not a problem for the other l
lines, and the polypack probes and polypack seals were operating as designed.
i If you have any questions, please contact me at (803) 776-2610, Extension 3282, or write me at the above address.
i Sincerely,
[
WESTINGHOUSE ELECTRIC CORPORATION J
Lct.Lcw
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W.
L. Goodwin, Manager Regulatory Affairs j
cc:
USNRC Region II t
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10CFR70.50 NOTIFIABLE EVENT WESTINGHOUSE COLUMBIA PLANT (SNM-1107)
NOVEMBER 11,1993 The Westinghouse low enriched uranium Commercial Nuclear Fuel Fabrication Facility, Columbia, S.C., is hereby providing notification to the Nuclear Regulatory Commission (NRC) in accordance with reporting requirements under NRC Regulation 10CFR70.50(b)(4). The Columbia Plant is a facility that manufactures nuclear fuel T
enriched to no greater than 5 weight percent U-235, for use in commercial light water reactors.
At approximately 4:00 PM, November 10, 1993, a minor fire occurred in the ADU Conversion Line 4 Fitzmill Product IIood.
The Line 4 Fitzmill system consists of a hammermill to mill uranium dioxide powder from the calciner. Milled powder is collected in polypacks in the ventilated stainless steel Product Ilood.
Initialindications are that heat caused by oxidation of the uranium dioxide powder partially melted the polypack, and caused the plastic seal against which the pack is pressed to burn very briefly. The fire was extinguished immediately using a portable fire extinguisher.
There was no need to activate the Site Emergency Plan or the Emergency Brigade, as determined by the Emergency Coordinator. Fire damage was limited to the polypack and the plastic seal. At no time was there a loss of ventilated containment. - The air sample located at this equipment indicated a concentration less than 20% of the Maximum i
Permissible Concentration, which verifies that containment was maintained. There were no personnel exposures and no releases of radioactive materials to the environment from this event and no other outside agencies required notification.
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' Repairs were implemented and processing was resumed by approximately 7:00 PM that evening.
1 An investigation is underway to determine root causes and corrective actions necessary to prevent recurrence.
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