ML20211D931
| ML20211D931 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 08/23/1999 |
| From: | Jonathan Brown UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-99-2047, NUDOCS 9908270168 | |
| Download: ML20211D931 (5) | |
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USEC A Global Energy Company August 23,1999 GDP 99-2047 U, S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Portsmouth Gaseous Diffusion Plant (PORTS)
Docket No. 70-7002 Event Report 99-16 i
l Pursuant to Safety Analysis Report, Section 6.9, Table 6.9-1, J.2, Enclosure I provides the required J
30-day written Event Report for an event involving an autoclave high condensate level shutoff actuation at the Portsmouth Gaseous Diffurion 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, h
J. Morris Brown General Manager Portsmouth Gaseous Diffusion Plant
Enclosures:
As Stated I
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NRC Region 11I Office j
NRC Resident Inspectors - PORTS 9908270168 990823 PDR ADOCK 07007002 C
PDR United States Enrichment Corporation Portsmouth Gaseous Diffusion Plani P.O.11ox 628, Pileton,01! 45661 L_
GDP 99-2047 Page1of3 Event Report 99-16 Description of Event On July 23,1999, at approximately 0320 hours0.0037 days <br />0.0889 hours <br />5.291005e-4 weeks <br />1.2176e-4 months <br />, X-344 autoclave (AC) #2 was in Mode 11 heating a 48" uranium hexaflouride (UF ) cylinder when the audible alarm for steam shutdown was received.
6 Operators responding to the alarm found the."A" and "B" condensate level probe lights illeminated indicating the high condensate level shutoff (HCLS) safety system had actuated. Steam supply block valve PSV-133 was veriGed to be in the closed position, stopping steam flow to the autoclave as designed. A HCLS actuation is reportable in accordance with the Safety Analysis Report, Table 6.9-1, J.2.
The condensate shutoff system is provided to prevent over pressurization or a nuclear criticality in an autoclave following a postukted UF release. Excess water is undesirable in the event of a UF 6
6 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 On October 14,1997, a modification of the AC #2 condensate piping was completed by maintenance i
personnel. This modification installed new piping and replaced the existing one inch strainer with a new two inch condensate strainer which incorporated a larger surface area and mesh size. The two inch strainer was installed to handle increased amounts of rust accumulation and to decrease the likelihood that the strainer would plug. The autoclave remained out of service until approximately September 18,1998. Since the return of AC #2 to service there have been two HCLS actuations.
One occurring on April 12,1999, resulted from inadequate shell cleaning and foreign material and the other on May 17,1999, resulted from cyclic application of steam without allowing suflicient time for the remaining condensate to drain (Reference Event Reports 99-07 and 99-11).
The direct cause for the actuation of the HCLS safety system was that the slope of the condensate drain line did not allow correct condensate drainage. One section of pipe exhibited an one-halfinch rise over 18 inches in the reverse direction for proper drainage. Borescopic examination of the condensate piping on AC #2 indicated that scaling circumscribed the entire pipe wall, which indicates the incorrect drain slope was causing plug flow. Scaling doubles the Fanning Friction Factor, and will cause condensate to back up an additional three inches toward the level probes. As a comparison, the X-344 AC #4 condensate piping was also borscoped. Scaling inside the pipe was confined to about the bottom third of the pipe, indicating the expected channel type Gov.
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J GDP 99-2047 Page 2 0f 3 Event Report 99-16 The root cause for the event was the condensate drain piping was not installed per the engineering drawing. The installation work package and work instructions were reviewed. The work package contained a drawing which showed the existing piping to be removed and the new configuration to be installed. The requirement for the piping slope to be a minimum slope ofone-fourth inch per ten feet was clearly noticeable on the drawing. The work instructions required installation to be performed in accordance with the drawing.
A contributing cause for the event was that the final walkdown required to confirm that installation was complete and in accordance with the drawing was inadequate. The walkdown of the system was performed on January 29, 1998. Procedure UE2-TO-EG1031 " Nuclear Modification Design Control" requires walkdowns to be performed to ensure strict alignment between associated accompanying drawings and the physical condition before returning the modified equipment to service.
Corrective Actions 1.
On July 29,1999, the incorrect slope on X-344 AC #2 condensate piping was corrected.
2.
On August 20,1999, a walkdown was completed on the remaining autoclaves in the X-342, X-343 and X-344 to establish that the slope of their condensate drain lines was correct. No other problems were found.
3.
On August 23,1999, a daily operating instruction was issued to maintenance management to inform them of this event and to emphasize the importance of performing modifications in accordance with approved engineering drawings and the need for continued attention to i
detail while performing such modifications.
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By September 24, 1999, a lessons learned will be created and a briefing held with maintenance personnel who perform modifications. The lessons leamed will emphasize the installation error that led to this event and the need to closely follow drawings when installing modifications.
5.
By October 24,1999, appropriate engineering design control procedures will be revised to incorporate documentation and verification of required modification activities such as walkdowns.
Extent of Exposure ofIndividuals to Radiation or Radioactive Materials There were no exposures to individuals from this incident to radiation or radioactive materials.
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l GDP 99-2047
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Event Report 99-16 Lessons Learned This event demonstrated the importance of rigorously following installation and inspection procedures when performing plant modifications.
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GDP 99-2047 l
Page1of1 Event Report 99-16 List of Commitments.
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By September 24, 1999, a lessons learned will be created and a briefing held with maintenance personnel who perform modifications. The lessons learned will emphasize the g
installation error that led to this event and the need to closely follow drawings when l
installing modifications.
l 2.
By October 24,1999, appropriate engineering design control procedures will be revised to l
j incorporate documentation and verification of required modification activities such as walkdowns.
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- Regulatory commitments contained in this document are listed here. Other actions listed in this submittal are not considered regulatory commitments in that they are either statements or actions completed, or they are considered enhancements to USEC's investigation, procedures, or operations.
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