ML20141A430
| ML20141A430 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 06/16/1997 |
| From: | Allen D UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-97-2009, NUDOCS 9706200274 | |
| Download: ML20141A430 (7) | |
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i United Stitis
.e Enrichment Corporation 2 0ernocracy Center.
6903 Rockledge Drive
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Bethesda, MD 20817 Tel: (301)564-3200 Fax: (301) 564-3201 Untileul Statew Eierichmerit Corp >ratiori June 16,1997
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GDP 97-2009 1
United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Portsmouth Gaseous Diffusion Plant (PORTS) - Docket No. 70-7002 - Event Report 97-08 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 (ER) for an event involving a high 1
condensate level shutoff actuation at the Portsmouth Caseous 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 (614) 897-2373.
Sincerely, g[f h Dale Allen General Manager Portsmouth Gaseous Diffusion Plant
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DIA:Scholl:me l
l Enclosures cc:
C. Cox/D. Hartland, NRC Resident Inspectors NRC Region III llh h !I,!
i 9706200274 970616 PDR ADOCK 07007002 C
PDR u Offices in Paducah. Kentucky Portsmouth, Ohio Washington. DC
i kJnited States Nuclear Regulatory Conunission June 16,1997 '
Page Two.
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Distribution Robert L. Woolley bec:
- J. Adkins, HQ J. Anzelmo, PORTS J. Bolling, PORTS M. Boren, PGDP S. Brawner, PGDP
- D. Davidson, PORTS
'J. Dietrich, LMUS L. Fink, PORTS R. Gaston, PORTS M. Hasty, PORTS J. Labarraque, PGDP B. Lantz, PORTS R. Lipfert, PORTS A. Rebuck-Main, HQ R. D. McDennott, PORTS J. Miller, HQ J. Mize, PGDP J. Morgan, PORTS J. Oppy, PORTS R. Robinson, PORTS S. Routh, HQ S. Scholl, PORTS B. Sykes, PGDP D. Thompson, PORTS R. Wells, HQ '
PORTS Records Management 5
d' Docket No,70-7002
- Enclosure 1
- Page 1 of 4 Event Report 97-08 Description of Event
'On May 18,1997, at 1420 hours0.0164 days <br />0.394 hours <br />0.00235 weeks <br />5.4031e-4 months <br />, X-344 AC #1 was in Mode H heating ten 2S (UF ) sample j
6 containers 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. : Steam supply block valve i
. PSV-103 was verified to be in the closed position, stopping steam flow to the autoclave as
.j 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 j
6 the event of a UF release from the cylinder that could cause either high Hydrogen Fluoride 6
pressure as the result of the reaction between UF and water or the excessive moderation of an 6
- unsafe mass of uranium thereby 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.
i Cause of Event i
The direct cause for the HCLS safety system actuation was the accumulation of debris in the condensate strainer. Maintenance inspected the in-line strainer and discovered that the strainer was restricted with debris.
The root cause for the event was that an abnormal amount of rust accumulated within AC #1 I
causing the condensate strainer to become rapidly plugged. In the past the accumulation of rust 'on the autoclave strainers was observed to be a gradual process. Normally an autoclave can be expected to operate for at least six months before strainer cleaning would be required, t
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However, in this event the AC #1 strainer became restricted after approximately one hour and twenty-eight minutes of heating. This event is similar to a previous event (Portsmouth Event Report 97-04) where the X-344 AC #3 strainer became restricted with rust after approximately one month of operation and to Event Report 97-07.
~ Autoclave #1 was out of service for approximately a year for maintenance.. Since the j
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- autoclave was out of service for so long a time, all TSR surveillance tests were completed
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before placing the autoclave back in service. The autoclave shell and head were cleaned on l
l April 9, and 21,' 1997.'~ On May 6,' 1997 Maintenance inspected the AC # 1 in-line strainer L
' and found it to be 80% restricted.' On May 7,1997,'a Post Maintenance Test (PMT) was 1
. performed on AC #1, in which the empty autoclave was heated with steam for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. ' Oa
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- Docket' No. '70-7002 -
- Enclosure 1.
Page 2 of 4 Event Report 97-08.
May 9,1997, the interior head and shell of Autoclave #1 were swept out to remove loose
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debris.
On May 13,1997,' the HCLS safety system actuated on AC #1 after heating a 48-inch UF6 cylinder for an hour and twenty-five minutes. Maintenance inspected the strainer after the 3
actuation and found the strainer volume was completely full of debris. Operations then -
performed condensate strainer PMT in which the autoclave was heated to check for steam leaks and proper steam trap operation. On May 14,1997, maintenance again removed the strainer and found it one third restricted with debris. Maintenance then flushed the condensate line and strainer with water. On May 15,1997, accessible areas of the AC #1 interior shell were cleaned. A PMT was run where the autoclave was heated with steam for approximately four hours. After the PMT was completed, the strainer was removed and inspected for any I
i debris. Maintenance found a very small amount of debris. At this point the debris was thought to have been removed so the autoclave was then put back into service.
On May 16,1997, the head of AC #1 was swept out, because it had not been swept when the shell was cleaned on May 15,1997. AC #1 ran for approximately three cycles before the HCLS actuation on May 18, 1997. Maintenance inspected the strainer after the actuation and found the strainer volume was completely full of debris. The condensate lines were borescoped to determine if there was any other debris. No other debris was found.
Since the autoclave head was swept out the day after the sheh and strainer were cleaned, it is i
believed the cleaning of the head contributed to the accumulation of debris in the strainer.
Previous HCLS actuations caused by restricted strainers resulted in the implementation of an L
autoclave interior shell cleaning program. Interior shell cleaning was considered as a way to reduce the amount of rust that could accumulate in the strainers. Because of the autoclave design, interior shell cleaning is limited to accessible surfaces. Autoclave shell and head cleaning methods have been changed as a result of this event. Now autoclave shell and head cleaning will be followed by a PMT, in which the autoclave is steam heated to wash any residual debris into the in-line strainer. After the PMT has been completed the in-line strainers will be inspected for debris accumulation and cleaned if necessary. In addition, thoroughly cleaning UF cylinders is not considered practical. As a result, cleaning operations 6
are not completely effective at limiting rust accumulation from all sources.
The autoclave interior and UF cylinders are made of steel which provides the source of rust within the autoclave. When rust flakes offit accumulates in the autoclave and eventually
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l collects in the condensate strainer. The. amount of rust within an autoclave is a function of the autoclave age and operational history. AC #1 has been in service for approximately twelve years. 'In addition, AC #1'was out of service for an extended period of time prior to this f
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Docket' No. 70-7002.
-Page 3 of 4 Event Report 97-08 event. This HCLS actuation occurred on the fourth cylinder heated in the autoclave in i
Lapproximately one year. Both of these factors would increase the amount of internal surface -
corrosion and contribute to an increase in rust accumulation.
Since the accumulation of rust within the autoclave cannot be readily controlled, Engineering i
has determined that the strainer design should be changed to accommodate the increased 1
amount of rust. The engineering investigation in response to Event Report 97-04 identified that the X-344 autoclaves have one-inch diameter drain lines. This is different from the two-inch drain lines incorporated into the other nine autoclaves. The condensate strainers in the
. one inch drain lines have a smaller surface area than the strainers in the two-inch lines. The smaller surface area will cause the strainers to become restricted more rapidly. The X-344 1
strainers will be increased in size to present fewer challenges to safety systems and allow longer run times between strainer cleaning.
A particle size analysis for debris typically collected in the strainer was performed. The analysis determined that most of the debris collecting on the strainer was two millimeters or less in size. Since the purpose of the strainer is to prevent large particles from fouling downstream equipment, Engineering determined that the strainer mesh size could be increased without any adverse effects to downstream equipment. As a result, the strainer mesh size will also be increased as part of the design change that will increase the strainer surface area.
The above design change will be implemented prior to the restart of AC #1. As part of the evaluation of the new design, the strainer will be inspected to ensure the new design is effective at preventing rapid strainer plugging. Weekly inspections of the X-344 autoclave strainers will also be implemented and will continue until an appropriate inspection frequency i
can be determined based on the rate of debris accumulation. A policy has been instituted for Maintenance to check / clean strainers after weekly cleaning of autoclave shells until the j
Computer Maintenance Management System (CMMS) has been updated.
l Corrective Actions 1.
On hm 4,1997, a new condensate strainer incorporating a larger surface area arxi mesh size was installed in X-344 AC #1 (Duplicate of corrective action #1 from Event
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Report 97-07)..
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- By July 16,1997, weekly condensate in-line strainer cleaning for the X-344 building Lautoclaves will be included on the PM Master portion of the Computer Maintenance Management System (CMMS). ' This frequency will continue until an appropriate 1
Docket No. 70-7002 -
- Page 4 of 4 Event Report 97-08 inspection frequency can be determined based on the rate of debris accumulation.
- (Duplicate of corrective action #2 from Event Report 97-07).
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Work instructions were revised on June 2,1997 for the Front Line Managers to issue
- weekly work requests for in-line strainer cleaning, after shell cleaning, prior to returning an autoclave to service. (Duplicate of corrective action #3 from Event Report 97-07).
Extent of Exposure of Individuals to Radiation or Radioactive Materials There were no exposures to individuals from this incident to radiation or radioactive materials.
Lessons Learned Cleaning of autoclave interior surfaces was originally considered as a way to reduce the amount of rust that could accumulate in the strainers. However, experience has proven that cleaning operations are not effective at limiting rust accumulation for all sources.
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.; Docket No. 70-7002' Page1 of1 Event Report 97-08 List of Commitments 1.
By July 16,1997, weekly condensate in-line strainer cleaning for the X-344 building autoclaves will be included on the PM Master portion of the Computer Maintenance Management System (CMMS). This frequency will continue until an appropriate inspection frequency can be determined based on the rate of debris accumulation.
(Duplicate of commitment #1 from Event Report 97-07).
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