ML20198S534
| ML20198S534 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 01/20/1998 |
| From: | Morgan J UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-98-2003, NUDOCS 9801260213 | |
| Download: ML20198S534 (5) | |
Text
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3 USEC A GW Energy Company.
January 20,1998 4
United States Nuclear Regulatory Commission GDP 98-2003 Attention: Document Control Desk
' Washington, D.C. 20555-0001 Portsmouth Gaseous Diffusion Plant (PORTS) - Docket No. 70-7002 - Event Report 97-23 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 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 diis event, please contact Scott Scholl at (614) 897-2373.
'h x erely,
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Si aV
&W Acting General Manager
$T Portsmo.ah Gaseous Diffusion Plant
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JBM:Scholl:me Enclosures (2)
( D. Hart'and, NRC Resident Inspcetor cc:
NRC Region III
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- PDR ADOCK 0700700Ei-C.
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PO. Box 800, Portsmouth, OH 45661 -
- Telephone 614 897-2255 Fax 614-897-2644 http://www.usec.com Offices in Livermore, CA Paducah, KY - Porumouth, Of EWashington, IL
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Docket No. 70-7002 Ehclosur' 1 e
Page1of3 Event Report 97-23 Description of Event On December 19,1997, at 0233 hours0.0027 days <br />0.0647 hours <br />3.852513e-4 weeks <br />8.86565e-5 months <br />, X-343 Autoclave (AC) #1 was in Mode 11 heating a 48-inch Uranium llexafluoride (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 ala m panel indicated that steam supply block valve FV-113 was closed, stopping steam flow to the autoclave as designed. A 11CLS 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, 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 urenium thereby causing e 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 the accumulation of debris on the interior surface of the condensate strainer. Maintenance inspected the in-line strainer and discovered that the interior of the strainer screen was coated with a film consisting of small particulate matter. The AC #1 condensate line was also borescoped to_ identify any other potential blockages in the line that could have caused water to backup and actuate the HCLS safety system. No blockages or foreign material were found.
The Root Cause for the event was the design of the condensate strainer. The strainer installed on X 343 AC #1 has a double screen. This double screen consists of a 16 wire mesh (Imm) screen inside a perforated support shield with 4mm holes. The double screen construction allowed very fine particulate matter to accumulate on the interior of the screen restricting flow enough to cause water to back up and actuate the "A" and "B" condensate level probes.
An engineering evabation determined that the installed strainer screen mesh size was too small
. for this application. A composition analysis of the de'oris collected from the AC #1 strainer screen determined that the debris consisted of agglomerations of particles, metal flakes, paint chips, insect parts, fibers and Teflon gasket material. The agglomerations contcibuted to the particles collecting on the screen instead of passi.;g throgh.
The X-343 Autoclave strainers are currently on a quarterly inspection ano cieaning schedule. The r
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Docket No. 70-7002 Ehclosur'e 1 Page 2 of 3 Event Report 97-23 Autoclave.#1 strainer was last inspecte> and cleaned approximately 82 days befare the llCLS actuation eccurred. A review of the maintenance history for the previous eight months indicates that the particulate film buildup has been observed on other X-343 autoclaves. Ilowever, the film buildup has not previously been enough to cause an liCLS actuation.
Since the December 19,1997, llCLS actuation, approximately 25 cylinders have been heated in Autoclave #1. The condensate strainer has been inspected three times and no significt.nt debris accumulation has been observed.
An Er:gineering review of %dustry standard practices and industry information on particulate removal requirements for steam condensate lines do not specify protection requirements for the temperature control valves, containment valves or steam traps that are located downstream of the stminer. Review of team trap manufacturer data and discussions with a manufacturer representative inoLate that the inverted bucket used on the autoclave condensate lines do not necessarily require a strainer and that they have good dirt handling ability. As a result, Engineering concluded that the condensate system design should be modified so that small particles cannot collect and restrict condensate flow.
j The condensate strainers in the X-344 building autoclaves have been previously modified to compensate for debris accumulation and are currently being inspected at weekly iatervals. As a result, no further actions are currently planned for the X-344 building autoclaves.
A possible contributing factor was that th-sclave had been shutdown for approximately two days before the llCLS actuation occurred. 71 ne cooler autoclave would have caused increased condensate production during initial heating. The HCLS actuation occurred approximately ten minutes into the heating cycle.
Corrective Actions 1.-
By April 30,1998, the X-342 & X-343 building condensate systems will be modified to prevent small particles from accumulating and rettricting condensate flow.
2.
By February 15,1998, an inspection of all X-342 and X-343 building autoclave strainers which have not been inspected and cleaned within the last 30 days will be completed.
3.
- On January 20,1998, the inspection and cleaning interval for all X-342 and X-343 building autoclave strainers was decreased to 30 days. This action will remain in place until modifications to the condensate system can be completed or an evaluation of inspection results indicate that the interval between strainer cleaning can be increased.
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Docket No. 70 7002 Ehclosur*e 1 Page 3 of 3 -
Event Report 97-23 Extent of Exposure ofInd!viduals to Radiation or Radioactive Materials Titere were no exposures to individuals from this incident to radiation or radioactive materials.
Lessons Learned This event demonstrated the strainer design allows fine particles to accumulate and eventually block condensate flew.
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. Docket No. 70-7002 E'nclosuic 21 Page1of1 Event Report 97-23.
List of Commitments.
.i 1.
By; April 30,1998, the X-342 & X 343 huilding condensate systems will be modified to prevent small particles from accumulating and restricting condensate flow.
2.-
13y February 15,1998, an inspection of all X-342 and X-343 building autoclave strainers
- i which have not been inspected and cleaned within the last 30 days will be completed.
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