ML20198N242

Forwards Rev 1 to Event Rept Er 98-13,for Event Resulting from Actuation of Cadp Smokeheads in X-333 Process Building. Caused by Unplanned Release of UF6.Compressor & Seals Were Replaced & Cell 33-3-3 Was Placed Back in Operation

ML20198N242
Person / Time
Site:	Portsmouth Gaseous Diffusion Plant
Issue date:	12/30/1998
From:	Jonathan Brown UNITED STATES ENRICHMENT CORP. (USEC)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GDP-98-2055, NUDOCS 9901060063
Download: ML20198N242 (4)

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CSEC A Global Energy Company December 30,1998 GDP 98-2055 United States Nuclear Reguletory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Portsmouth Gaseous Diffusion Plant (PORTS)

Docket No. 70-7002 Event Report 98-13, Revision 1 Pursuant to the Safety Analysis Report Section 6.9, Table 6.9-1, J(2), Enclosure 1 provides a revised Event Report for an event that resulted from the actuation of CADP smokeheads in the X-333 Process Building due to an unplanned release of UF. The revised event report contains the root 6

cause and corrective actions for this event. Changes from the previous report are marked with a vertical line in the right margin.

1 Should you require additional information regarding this event, please contact Scott Scholl at (740)897 2373.

Sincerely, h

J. Morris Brown General Manager I

Portsmouth Gaseous Diffusion Plant I

Enclosures:

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P.O. E,ox 800, Portsmouth, OH 45661 Telephone 614-897-2255 Fax 614-897-2644 http://www.usec.com Offices in Livermore, CA Paducah, KY Portsmouth,011 Washington, DC

6 GDP 98-2055 Page1of3 Event Report 98-13, Revision 1 Description of Event At 0848 hours0.00981 days <br />0.236 hours <br />0.0014 weeks <br />3.22664e-4 months <br /> on September 6,1998, a process operator in the X-333 Process Building reported to l

the Area Control Room (ACR-1) an observation /- A : in Unit 33-3. At 0850 hours0.00984 days <br />0.236 hours <br />0.00141 weeks <br />3.23425e-4 months <br />, CADP 1

smokehead S-31, ~which provides coverage for w8 %

u. age 1 and 2, actuated. At 0853 hours0.00987 days <br />0.237 hours <br />0.00141 weeks <br />3.245665e-4 months <br />, l

the ACR-1 personnel implemented "See and Flee" meanes by sounding the building recall horns l

and calling the Plant Shift Superintendent's (PSS) office.

l At 0857 hours0.00992 days <br />0.238 hours <br />0.00142 weeks <br />3.260885e-4 months <br />, fire department personnel arrived at X-333 and entered the building wearing required personal protective equipment. Personnel monitoring the area detennined smoke was coming from j

the X-33-3-3 stage 1 compressor seal. At 0945 hours0.0109 days <br />0.263 hours <br />0.00156 weeks <br />3.595725e-4 months <br />, cell 33-3-3 was taken off-stream and the cell 1

pressure was reduced below atmospheric. At 0959 hours0.0111 days <br />0.266 hours <br />0.00159 weeks <br />3.648995e-4 months <br />, cell 33-3-3 motors were shut down due to compressor surging caused by air inleakage. At 1145 hours0.0133 days <br />0.318 hours <br />0.00189 weeks <br />4.356725e-4 months <br />, an "All Clear" was granted.

According to the Technical Safety Requirements for the Portsmouth Gaseous Diffusion Plant, the j

CADP smoke detectors are required to be operable when a cell is operating above atmospheric 1

pressure. In this instance, cell 33-3-3 B-line pressure was above atmospheric, which makes the l-actuation of this smoke detector alarm reportable in accordance with the Safety Analysis Report, Section 6.9, Table 6.9-1, J(2).

The material that outgassed was low-enriched UF at approximately 0.92% U-235.

6 Cause of Event The direct cause of the CADP actuation was a UF release from the cell 33-3-3 stage 1B compressor 6

seal. The stage 1B seal was installed on October 25,1997, and cell 33-3-3 was placed in service on i

December 24,1997. During the preparation to place the cell on-stream, personnel determined the

. stage 1B seal was allowing ambient air to leak through the atmospheric side of the seal and into the seal cavity. In accordance with procedure XP4-CO-CA2125, " Cell Compressor Seal Operation in X-333," the seal feed and seal' exhaust were valved off and a 1 psig seal air pressure was applied to the atmospheric gland to prevent wet air inleakage and to allow the "B" seal system to remain in control.

The compressor shaft seals are designed to avoid the loss of UF and to minimize inleakage of other l

6 gasses to the cascade. In the event of a seal failure, nitrogen and dry air will leak into the process l

l system rather than process gas leaking out. When a seal is valved off, the. seal feed is no longer I

applied to the seal cavity. The seal cavity pressure will remain at subatmospheric pressure via the vented cavity line.

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GDP 98-2055 Page 2 of 3 Event Report 98-13, Revision 1 Cell 33-3-3 operated at below atmospheric pressure from December 24,1997, to approximately

- September 3,1998. The cell pressure rose above atmospheric pressure on September 3,1998, as a result of a planned cascade power load increase. Cell 33-3-3 operated above atmospheric pressure until September 6,1998, when the seal failure caused the cell to be taken off-stream. An inspection i

of the seal following this event determined that a groove had been worn in the compressor shaft l

during operation, causing the gap between the compressor shaft and the seal labyrinth to become.

l greater than specification. Due to the damaged shaft, the cell 33-3-3 stage 1 compressor was I

replaced with a new compressor.

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The root cause of the seal outgassing was failure of the stage 1 B seal labyrinth. It was determined l

= that during operation the labyrinth lost its ability to reduce laminar flow at e' <ated high-side l

pressures, thereby increasing the seal cavity pressure faster than it could be exhausted. When the l

' internal seal cavity pressure exceeded atmospheric pressure, it caused the seal to outgas. A UF.

l outgassing can occur on a seal, whether ' alved in or valved off, when the vented cavity line is -

v obstructed or the seal labyrinth fails to perform its design ftmetion.

- Seals may be damaged during normal operations by surging, or during compressor start-up or shut-l down. This type of seal failure is an expected consequence of normal plant operations..The accident l

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' analysis'for " Compressor Seal Failure" in the Safety Analysis Report states: "A release of UF could l

6 occur as a result of a seal failure. The probability of occurrence is high. The consequence is l

negligible and the risk is extremely low."

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Corrective Actions I

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. Due to the groove in the compressor shaft, the compressor and seals were replaced and cell 33 l 3 was placed back in operation on November 16,1998.

l Extent of Exposure ofIndividuals to Radiation or Radioactive Materials There were no significant exposures to individuals from this incident to radiation or radioactive L

materials. The two operators who witnessed the outgassing submitted urine samples for analysis.

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The bioassay results were less than the urinalysis program flag action levels (5pg/l) specified in SAR l

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Table 5.3-4.

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GDP 98-2055 Page 3 of 3 Event Report 98-13, Revision 1 Lessons Learned The problem of seal outgassings is being investigated through a Quality of Operations committee.

l The committee has developed a plan to initiate maintenance and operational improvements and to l

perform trending of seal pressures to determine whether a seal would be likely to fail. The trending 1

- will help the committee propose future improvements to seal operations and maintenance activities j

that could lead to a reduction in minor seal outgassings.

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