ML20199G901
| ML20199G901 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 11/19/1997 |
| From: | Morgan J UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-97-2034, NUDOCS 9711250331 | |
| Download: ML20199G901 (3) | |
Text
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. United Sttes A
- Enrichment Corporation 2 Democracy Center L*
6903 Rockledge Dove-Bethesda, MD 20817
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Tel: (301)564 3200 Fax:(301) 564-3201 Usulivl N.alen l',ntirlnncent Curjueratloti November 19,1997 United States Nuclear Regulatory Commission GDP-97-2034 Attention: Document Con.ol Desk o
Washington, D.C. 20555-0001 Portsmouth Gaseous Diffusion Plant (PORTS)- Docket No. 70-7002 - Event Report 97-21 Pursuant to 10 CFR 76.120 (d)(2), Ecclosure i provides the required 30 day written Event Report (ER) for an event involving a failure of the UF Cylinder High Pressure Autoclave Steam Shutoff safety system at the Portsmouth Gaseous Diffusion Plant, investigation activities are continuing to determine the root cause and corrective actions for this event. This report will be revised following completion of these activities. The revised report is scheduled fc: Febmary 14,1998. There are no new commitments contained in the report.
Should you require additional information regarding this event, please contact Scott Scholl at (614) 897-2373.
Sincerely,
/
Jim Morgan f-Acting General Manager y
i{b Portsmouth Gaseous Diffusion Plant
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NRC Region III
- D. Hartland, NRC Resident Inspector, PORTS li!EEEIN ElBllR fkd $g9' PDR
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Offices in Paducah, Kentucky Portsmouth, Ohio Washington.DC
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- p l Docket N6i70-7002 i
^ Enclosure i s y
-Page1of2?
i Event Report.97-21 x
1 L Description of Event
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"On October 22,1997, at 0635 hours0.00735 days <br />0.176 hours <br />0.00105 weeks <br />2.416175e-4 months <br />, X-343 Autoclave (AC) #7 was in M6de 11, heating a 14 ton i
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- Uranium;Hexafluoride (UF.) Tails cylinder when the audible alarm for steam shutdown was
-l received.ine cylinder had been heating for approximately one hour when the actuation occurred..
The Operator responding to the alarm noticed the Low Cylinder Pressure Shutoff (LCPS) safety ~
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= system had actuated, causing the steam' supply valves to AC_ #7 to close. The operator also' noted that PI 705A indicated an intemal UF. cylinder pressure of-50 psia. The LCPS is designed to-x actuate if the internal cylinder pressure has not reached 20 psia after one hour of heating.. Since a Treading of -50 psia indicated the' instrument had malfunctioned, the operator opened the local :
4 (instrument cabinet to investigate the failure. When the door to the cabinet was opened, the door movement caused the instrument reading to change to 61.7 psia, which was the expected cylinder -
pressure. The steam supply valves to the autoclave then opened and cylinder heating resumed automatically as designed. The operator immediately initiated steam shutdown utilizing the local steam isolation controls to place the autoclave in a shutdown condition until the cause of the
' actuation could be determined. -
The initial engineering review of the actuation concluded that the LCPS actuation was caused by un
. invalid low pressure signal _and was not reportable. Further investigation into the cause of the failure 1
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'of PI-705A revealed that the prest.ure transducer providing the signal to PI-705A had failedi (Engineering determined that the failed pressure transducer also rendered the UF. Cylinder High Pressure Autoclave. Steam-Shutoff (CHPASS) safety system inoperable, since the pressure
-transducer also provides the signal for this safety 'systen,. Following the discovery of this
. information, it was determined that the faihire of the AC #7 CHPASS safety system was reportable in accordance with 10 CFR 76.120 (c) (2). The event notificatior, was made on Octobei 24,1997, t
. at 1735 hours0.0201 days <br />0.482 hours <br />0.00287 weeks <br />6.601675e-4 months <br />. The pressure transducer is a 24-VDC instmment, manufactured by Moore Industries, n
'. model number PIT /3-15PSIG/4-20MA/12-42DC.
^The CHPASS system is a single channel system. The heating of a ufo ylinder containing an c
. excessive ~ amount of' light' gases at. normal heating 'c iperatures could r:.sult in the internal cylinder pressure exceeding the. hydrostatic test pressure and possibly create a UF. release in the autoclave.
The safety system function of the CHPASS ensures the pressure in the cylinder does not exceed the maximum allowable working pressure of the lowest rated cylinder that could be heated in the
! autoclave.4The UF. cylirider pressure instrument loop is required to alarm if the cylinder pressure
~.' at any time reaches 115 psia with a tolerance of + 5 psia.
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Docket No. 70-7002 ~
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' Enclosure 1 Page 2 of 2' Event Report 97-21 Cause of Event '
5'Ibe direct cause of the event was a failed pressure transducer. The pressure transducer converts a
- pneumatic signal of 3-15 psia to a current signal of 4-20 mA, Since the loop is wired in series, when the 4-20 mA current from the pressure transducer is lost, it renders the loop inoperable.-
The root cause of the failed pressure transducer has not been determined. Engineering will perform a failure analysis and root cause determination of the failed pressure transducer. This event report
. will be revised when the root cause and corrective actions have been determined. A revised report iis scheduled for February 14,1998.
Corrective Actions-1.
On October 28,1997, the pressure transducer was replaced and the loop calibrated.
Extent of Exposure ofIndividuals to Radiation or Radioactive Materials There were no exposures to individuals from this incident to radiation or radioactive materials.
Lessons Learned
- Lessons learned will be provided with the revised event report.
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