ML20217E988
| ML20217E988 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 03/24/1998 |
| From: | Morgan J UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-98-2015, NUDOCS 9803310233 | |
| Download: ML20217E988 (5) | |
Text
{{#Wiki_filter:- - _ - - _ - - - _ _ _ - USEC . A Global energy Company March 24,1998 GDP 98-2015 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Portsmouth Gaseous Diffusion Plant (PORTS) Docket No. 70-7002 Event Report 98-04 Pursuant to Safety Analysis Report (SAR), Section 6.9, Table 6.9-1, J (2), Enclosure 1 provides the required 30 day written Event Report for an event involving a high condensate level shutoff actuation at the Portsmouth Gaseous Diffusion Plant. Enclosure 2 is a list of commitments made in the report. Should you require additional information regarding this event, please contact Scott Scholl at (740) 897-2373. Sincerely, an Acting General Manager Portsmouth Oaseous Diffusion Plant
Enclosures:
(2) \\ cc: NRC Region 111 Office D}l , (' NRC Resident Inspector-PORTS / 9003310233 900324 ADOCK 0700 2 -{DR !!O. Box 800, Ibrtsmouth, OH 45661 - Telephone 614-897-2255 Fax 614-897-2644 http://www.usec.com Ofkes in Livermore, CA Paducah, KY lbrtsmouth, OH Washington DC
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n y j ? Encl'osure 1 - GDP 98-2015 - Page1of2 1 Event Report 98-04 ' Description of Event ' l. L l On February 24,' 1998, at 1700 hours,-X-343 Autoclave (AC) #2 was in Mode II heating a 48-inch - . Uranium Hexafluoride (UF ) cylinder when the audible alarm for steam shutdown was received.
- Operators responding;to the alarm found the "A" and "B" condensate level probe lights on,.
indicating the high condensate level shutoff (HCLS) safety system had actuated. The autoclave local
- alarm panel indicated that steam supply block valve FV-213 was closed, stopping steam flow to the.
L autoclave as designed. A HCLS actuation is reportable in accordance with the Safety Analysis -Report (SAR), Table 6.9-1, J(2). ! The condensate level shutoff system is provided to prevent over pressurization or a nuclear criticality in an autoclave following a postulated UF release. Excess water is undesirable in the event of a UF 6 6 l release from the cylinder that could cause either high hydrogen fluoride pressure as the result of the reaction between UF and water or the excessive moderation of an unsafe mass of uranium thereby 6 causing a criticality within the autoclave. The system function is to detect either a drain line plug or restriction and to shutoff the steam flow to the autoclave. . Cause of Event . The direct cause for the HCLS safety system actuation was that condensate drain valve V-256-2 was l closed. Operators discovered the closed valve while performing troubleshooting checks in response L to the HCLS actuation. Because the valve was in the closed position, condensate was prevented from draining to the main condensate drain line. This caused condensate to backup in the piping and i actuate the "A" and "B" condensate level probes. Autoclave #2 had been operating for approximately 35 minutes when the HCLS actuation occurred. F ' Prior to this actuation the autoclave had been removed from service for condensate strainer cleaning ' and repair of the locking ring limit switch. These maintenance activities did not involve operation
- of valve V-256 2. It is believed the inadvertent closure of valve V-256-2 occurred during or after one of the maintenance evolutions prior to AC #2 being retumed to service. The Group Manager s for Feed & Transfer Operations conducted critiques and personal interviews with operations and
! maintenance personnel but was unable to determine how or when the valve was closed. iThe root cause for the event was that autoclave operating procedures do not require valve lineup
- verification following maintenance activities that could result in valves being in abnormal positions.
Operating practices only required valves which were manipulated as part of the maintenance activity to be checked before retuming an autoclave to service. Valves that were not operated as part of the i /I ____.___.__-_..-m_____________
j ' - s GDP 98-2015 Page 2 of 2 Event Report 98-04 maintenance activity were not checked and were assumed to be in the normal as left position. This practice allowed the inadvertent closure of condensate drain valve V-256-2 to go undetected until the autoclave was operated on February 24,1998. l Autoclave safety system actuation event reports were reviewed back to January 1,1995. No safety system actuation events were discovered where a valve mis-alignment was determined to be the cause of an actuation. Corrective Actions 1. On February 24,1998, daily operating instructions were issued requiring verification of correct valve lineup prior to each autoclave startup. 2. By May 15,1998, X-342, X-343 and X-344 Autoclave Operating Procedures will be revised to require valve alignment verification following maintenance, after extended periods of an autoclave being out of service or after other activities that could result in valves being in abnormal positions. 1 Extent of Exposure ofIndividuals to Radiation or Radioactive Materials i There were no exposures to individuals from this incident to radiation or radioactive materials. Lessons Learned 'Ihis event demonstrates the importance of valve lineup verificatiori following maintenance activities and prior to autoclave startup. L i Um.._ _ _ _ _.
/:... *.
- j.., f. *.: 8 GDP 98-2015 Page1of1 Event Report 98-04 List of Commitments
- 1. -
By May 15,1998, X-342, X-343 and X-344' Autoclave Operating Procedures will be revised
- to require valve alignment verification following maintenance, after extended periods of an autoclave being out of service or after other activities that could result in valves being in abnormal positions.
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