ML20138A663
| ML20138A663 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 04/21/1997 |
| From: | Allen D UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9704280152 | |
| Download: ML20138A663 (6) | |
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United States Ennchment Corporation 2 Democracy Center L-6903 Rockledge Dnve Bethesda, MD 20817 Tel: (301)564-3200 frtiteel States
}{nrichinertl GerJM>nitioti April 21,1997 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 j
Portsmouth Gaseous Diffusion Plant (PORTS)- Docket No. 70-7002 - Event Report 97-01 l
Pursuant to the Safety Analysis Report (SAR), Section 6.9, Table 6.9-1, J (2), Enclosure 1 is the required 45 day written Event Report for an occurrence involving an actuation of the Cascade Automatic Data Processing (CADP) smoke detection system at the Portsmouth Gaseous Diffusion Plant. Enclosure 2 is a list of commitments made in the report.
Should you require additior.al information regarding this event, please contact Scott Scholl at (614) 897-2373.
Sincerely, Dale Allen General Manager Portsmouth Gaseous Diffusion Plant DIA:SScholl:kpb Enclosures I
cc:
C. Cox/D. Hartland, NRC Resident Inspectors, PORTS NRC Region III 9704280152 970421 h
PDR ADOCK 07007002 C
PDR Llll$lll15Illllll)ll!IIIII.II Offices in Paducah. Kentucky Portsmouth. Ohio Washington, DC
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_ United States Nuclear Regulatory Commission
- April 21,1997 Page Two Distribution Robert L. Woolley bec:
- J. Adkins, HQ.
J. Anzelmo, PORTS ;
M. Boren, PGDP -
J. Dietrich, LMUS L. Fink, PORTS
- R. Gaston, PORTS
' M.~ Hasty, PORTS.
- J. Labarraque, PGDP B. Lantz, PORTS R. Larson, PORTS R. Lipfert, PORTS J. Miller, HQ J. Mize, PGDP '
R. McDermott, PORTS EJ. Morgan, PORTS
- A. Rebuck-Main, HQ S. Routh, HQ S. Scholl, PORTS B. Sykes, PGDP
' R. Wells, HQ PORTS Records Management RM: PORTS 97-890-080 r
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- Docket No. 70-7002 Page1of3 Event Report 97-01 Description of Event
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On March 20,1997, at 1409 hours0.0163 days <br />0.391 hours <br />0.00233 weeks <br />5.361245e-4 months <br /> while performing withdrawal operations at the Tails Side Withdrawal Station, the Cascade Automatic Data Processing (CADP) smoke detector, designated -
as SSWL, alarmed in Area Control Room (ACR) #2 in the X-330 Process Building. Operations
. personnel investigated the alarm and observed smoke emanating from the area of compressor 30 l
WB-1, which had been operating in the withdrawal mode. Operations personnel in the area followed j
the "See & Flee" policy and evacuated the affected area. Building recall was sounded to have all 1
personnel report to their respective areas.
According to the Technical Safety Requirements for the Portsmouth Gaseous Diffusion Plant, the CADP smoke detectors are required to be operable when the Tails Withdrawal Station is operating in Modes II, HI, or IV. In this instance, the Tails Side Withdrawal was operating in Mode III, which
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would make the actuation of this smoke detector alarm reportable in accordance with the Safety 1
Analysis Report, Section 6.9, Table 6.9-1, J(2).
Prior to initiating the withdrawal, the compressor was out of service for repair of a leak at the compressor flange. At 1755 hours0.0203 days <br />0.488 hours <br />0.0029 weeks <br />6.677775e-4 months <br /> on March 19,1997, compressor 30 WB-1 was started. At 2330
'1 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, compressor 30 WB-1 was charged with UF and valved into service. On March 20,1997 at j
6 1315 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />5.003575e-4 months <br />, the Tails Side Withdrawal was started. Within 54 minutes, at 1409 hours0.0163 days <br />0.391 hours <br />0.00233 weeks <br />5.361245e-4 months <br />, CADP moke
' detector SSWL, located above compressor 30 WB-1, actuated. At 1412 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.37266e-4 months <br />, the Pyrotronics smokehead XAH300B1, which provides a redundant smoke detection system in Tails, also fired.
At 1417 hours0.0164 days <br />0.394 hours <br />0.00234 weeks <br />5.391685e-4 months <br />, the compressor was shut down from the ACR and the alarm on SSWL cleared. At 1419 hours0.0164 days <br />0.394 hours <br />0.00235 weeks <br />5.399295e-4 months <br />, an Operator wearing proper personnel protective equipment responded to the area and found smoke emanating from the area of compressor 30 WB-1.
Additional emergency personnel were called and responded to the area. Emergency responders monitoring the area did not detect airborne contaminants. IIcalth Physics reported all air samples and radiological surveys as less than detectacle and no evidence of an UF release. An "All Clear" 6
was given on the building recall at 1506 hours0.0174 days <br />0.418 hours <br />0.00249 weeks <br />5.73033e-4 months <br />.
. Following the All Clear, Operations and Maintenance personnel investigated the affected equipment and found no evidence of a failed compressor seal, which was considered the most likely source of L
~a UFg leak in this area. Since there was no evidence indicating that the smoke originated from a UF
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6 frelease, plant personnel initiated an investigation to determine the source of the smoke.
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Docket No. 70-7002 Page 2 of 3 Event Report 97-01:
On March 23,1997, maintenance removed a housing panel and found residue indicating that UF 6
outgassing had occurred. Visible contamination was found on and around the WWB-27 compressor discharge block valve. A leak check performed on the valve bellows at 1715 hours0.0198 days <br />0.476 hours <br />0.00284 weeks <br />6.525575e-4 months <br /> determined there was a leak. On March 24,1997, following confirmation of an UF outgassing as the cause of the l
6 CADP alarm, it was determined the occurrence was reportable to NRC.
The valve with the failed bellows which caused the outgassing was a 4-inch, model G-17 gate valve, manufactured by the Crane Company.
The material that outgassed was enriched UF at approximately 3.0% U-235.
6 Cause of Event The direct cause of the UF release was failure of the bellows on the WWB-27 compressor discharge i
6 block valve. The leaking bellows allowed the process gas to escape which set off the smoke 5
detectors above the nearby compressor. The CADP UF Smoke Detection System SSWL 6
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smokehead and Pyrotronics smokehead XAH300B1 actuated in the Tails Withdrawal Area.
The root cause of the outgassing was the design of the valve buffer system. The purpose of the valve buffer is to prevent the buildup of UF in the valve stem cavities by keeping the buffer pressure 6
approximatly 5 psi above the maxi. mum process gas pressure. The valve buffer system was desi;ned to automatically switch from a low pressure (10 psig) to a high pressure (25 psig) buffer supply as
.I the process gas pressure increases. The high pressure supply flows through an orifice which limits the buffer air flow rate. The bellows leak caused the buffer pressure to drop low enough, allowing the process gas to escape. To improve the ability of the buffer system to prevent a UF release, an 6
enhancement to the system design has been identified. A new design will provide a variable pressure buffer system which will maintain the buffer air supply at a constant differential above the process pressure. Installation of the new design is scheduled to be completed in 1997.
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The Tails Side Withdrawal Station remains out of service pending completion of repairs to the G-17 i
valve bellows.
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Docket No. 70-7002 Page 3 of 3 Event Report 97 Corrective Actions By December 31,1997, installation of a new, upgraded variable buffer system which will maintain a buffer pressure above the process pressure at the Tails Withdrawal Station will be completed.
Extent of Exposure ofIndividuals to Radiation or Radioactive Materials There were no exposures to individuals from this incident to radiation or radioactive materials. The operator who investigated the smoke alarm submitted a sample for urinalysis. The results were
- below 5 ug/ liter for soluble uranium (flag level). The calculated intake was 1.25 micrograms of uranium. The limit for occupational workers is 10,000 micrograms of uranium.
Lessons Learned Personnel responded appropriately to this event in accordance with the "See and Flee" policy.
A correctly operating buffer air system is necessary to mitigate the effects of small bellows leaks and prevent releases from occurring.
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' Docket No. 70-7002 '
Page1of1 Event Report 97-01 List of Commitments -
By December 31,1997, installation of a new, upgraded variable buffer system which will maintain a buffer pressure above the process pressure at the Tails Withdrawal Station will be completed.
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