ML20217H171
| ML20217H171 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 08/04/1997 |
| From: | Allen D UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-97-2016, NUDOCS 9708110032 | |
| Download: ML20217H171 (5) | |
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United States Ennchment Corporation
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2 Democracy Center 6903 Rockledge Dnvo Dethesda. MD 20817 l
Tel- (301) 564-3200 Uttilnl Slalem Fax'(301) 564-3201 f.firielitiielit Corlwiratioli August 4,1997 GDP-97-2016 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 97-10, Revision 1 i
Pursuant to Safety Analysis Report (SAR), Section 6.9, Table 6.9-1, J (2), Enclosure 1 provides Event Report 97-10, Revision 1, for an event involving a UF. cylinder high pressure alarm actuation at the Portsmouth Gaseous Diffusion Plant. The revised event report is being submitted to provide additional information regarding this event. Changes from the previous report are marked with a vertical line. Investigation activities are continuing to determine the roet cause and corrective actions for this event. This event report will be revised ic' sowing completion of these activities. The revised report is scheduled for November 6,199;.
Should you require additional it formation regarding this event, please contact Scott Scholl at (614) 897-2373.
Sincerely, o
Dale Allen General Manager Portsmouth Gaseous Diffusion Plant DIA:SScholl:cw i
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NRC Region III C. Cox/D. Hartland, NRC Resident Inspectors, PORTS 9708110032 970804 PDR ADOCK 07007002 C
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33-Offices in Paducah. Kentuck y Portsmouth. Ohio Washington DC
e United States Nuclear Regulatory Commission August 4,1997 Page 'Iwo Distribution Robert L. Woolley
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J, Adkins,'HQ
-J.- Anzelmo, PORTS
.: Ri-Boelens, PORTS
- J. Bolling, PORTS M. Boren, PGDP S Brawner, PGDP L. Cutilp, PORTS
-J. Dietrich, LMUS L.- Fink, PORTS R. Gaston, PORTS M. Hasty, PORTS P. Hopkins, PORTS J, Hutsebant, PORTS J. Labarraque, PGDP
- B, Lantz, PORTS R. Lipfert, PORTS R. McDermott, PORTS-J. Miller, HQ J. Mize, PGDP J. Morgan; PORTS
- J. Oppy, PORTS G. Price, PORTS ~
S. Polston, PGDP
' H. Pulley, PGDP
. A. Rebuck-Main, HQ R. Robinson, PORTS S. Routh, HQ.
S. Scholl, PORTS B. Sykes, PGDP
- D. Thompson; PORTS D. Towne, PORTS M. Valentine, PORTS R'.__ Wells, HQ -
' Plant Shift Superintendenta PORTS Record Management odusers\\nra ports \\97-10-er.r1 t
- Docket No. 70-7002 Page 1 of 3 Event Report 97-10 Revision 1 Description of Event On May 23,1997, at 0125 hours0.00145 days <br />0.0347 hours <br />2.066799e-4 weeks <br />4.75625e-5 months <br />, X-343 Autoclave (AC) #5 was in Mode II, heating 30 inch (2.5 ton) Russian Uranium IlexaDuoride (UF ) cylinder #LUO705 when the audible alarm for 6
UF cylinder high pressure autoclave steam shutoff was received. Operators responding to 6
the alarm observed that the internal cylinder pressure was 115 psia, which was also the alarm setpoint. Steam supply valve FV-513 was verified closed as designed. Five minutes later at 0130 hours0.0015 days <br />0.0361 hours <br />2.149471e-4 weeks <br />4.9465e-5 months <br />, while in Mode VII and with the steam supply valve still closed, AC #5 alarmed a second time when the cylinder pressure reached 130 psia. The actuation of the UF6 cylinder high pressure autoclave steam shutoff is reportable in accordance with the Safety Analysis Report (SAR), Table 6.9-1, J (2).
At 0105 hours0.00122 days <br />0.0292 hours <br />1.736111e-4 weeks <br />3.99525e-5 months <br />, at the start of the cylinder heating process the cylinder cold pressure reading was 6.0 psia. At 0124 hours0.00144 days <br />0.0344 hours <br />2.050265e-4 weeks <br />4.7182e-5 months <br />, during the heating process the operator observed the cylinder pressure at 45.0 psia, which was higher than what is normally expected after 19 minutes of heating. In accordance with procedure XP4-TE-FD2701, "X-343 and X-342 Autoclave
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Operation," the operator prepared to hot burp (vent to the cascade) enough UF to reduce 6
cylinder pressure. One minute later, at 0125 hours0.00145 days <br />0.0347 hours <br />2.066799e-4 weeks <br />4.75625e-5 months <br />, before the operator could hot burp the cylinder the autoclave alanned at 115 psia due to cylinder high pressure. The operator responded according to procedure and immediately hot burped the cylinder. The cylinder pressure following the hot burp was 9,0 psia. At 0130 hours0.0015 days <br />0.0361 hours <br />2.149471e-4 weeks <br />4.9465e-5 months <br />, although the steam supply was isolated from the autoclave, the operator noticed the cylinder pressure had increased to 70 psia and rising. While the operator was proceeding to hot burp the cylinder for the second time the autoclave alarmed again due to high cylinder pressure. The operator responded and immediately hot burped the cylinder reducing the pressure to approximately 50 psia. The cylinder pressure then dropped to approximately 20.0 psia and stabilized. The highest pressure observed during this event was approximately 130 psia which is less than the 214.4 psia maximum allowable working pressure (MAWP) of 2.5-ton cylinders. Approximately thirty-three Ibs. of material was removed from the cylinder during the two burps.
The UF cylinder high pressure autoclave steam shutoff system is provided to prevent 6
internal cylinder over pressurization caused by nonrul heating of a UF cylinder containing 6
excessive amounts of light" gases, in addition, in the event an over filled cylinder is heated in an autoclave the UF cylinder high pressure autoclave steam shutoff system prevents the 6
internal cylinder pressure from exceeding the hydrostatic test pressure of the cylinder.
Cause of Event The direct cause of the UF cylinder high pressure alarm is believed to be the unequal 6
distribution of UF behind the cylinder valve or trapped gases being released from withir, 6
Docket No. 70-7002 Page 2 of 3 Event Report 97-10 Revision 1 solid UF.
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Similar pressure increases have occurred previously while heating 2.5-ton cylinders. One event occurred September 9,1995 while heating two Commonwealth Edison cylinders filled in Russia and other occurred October 24,1996, while heating three cylinders containing blended UF filled in Russia. These pressure increases were similar to pressure increases 6
experienced when heating 14-ton Tails cylinders filled at PORTS and cylinders filled at PGDP during cold weather. It is believed that rapid cylinder cooling causes a build-up of solid UF to form near the valve, separating it from the larger cylinder void votume.
6 Corrective actions resulti am these previous events included revising operating procedures to give the opeiator the authority to hot burp a cylinder when cylinder pressure is rising rapidly or has exceeded 90 psia. Ilowever, in this event the pressure rise occurred more rapidly than expected, preventing the operator from relieving the cylinder pressure before the 115 psia set point was exceeded.
Other factors that could have produced the type of pressure increase were eliminated by weight data and the analysis of laboratory samples following the event. Weight data showed that the cylinder was filled to 4994 pounds, which was below the 5020 pound maximum cylinder fill limit.. The amount of weight lost during the two hot burps indicates that liquid UF was evacuated from the cylinder and not " light" gases. The laboratory samples taken y
6 following hot burping indicate that no excessive " light" gas were present in the cylinder.
3 On May 23,1997, Customer Services and Product Scheduling put a hold on heating 2.5-ton Russian cylinders until an engineering evaluation could be completed to determine corrective actions to prevent a recurrence of thh event. On May 29,1997 the cylinder hold was modified to allow heating of the Russian cylinders that have previously been through a heating cycle at PORTS.
On July 9,1997, heating of Russian cylinders was resumed following implementation of temporary procedural controls. The procedural controls include an enhanced valve clarity check to identify if unequal distribution of UF exists behind the cylinder valve. The new 6
controls also provide a modified heating process that will reduce the rate that heat is added to the cylinders and an alternate valving configuration that reduces the time needed to burp cylinders to avoid cylinder high pressure alarms. Additional cylinder void space gas samples will also be taken after modified le,ating to allow analysis of trapped gases. These actions will reduce the probability of a recurrence of this event and allow additional data to be gathered to determine the root cause of the pressure spikes. These temporary procedural controls will remain in effect until a long term corrective action plan can be implemented.
This event report will be revised when the root cause and corrective actions have been
Dopket No.-_70 7002 Page 3 of 3 Event Report 97-10 Revision 1 determined. A revised event report is scheduled for November 6,1997.
l Corrective Actions 1.
On July 8,1997, temporary procedure XP4-TE-FD-2791-TEMP was implemented to provide; 1) a new method of identifying the existence of unequal distribution of UF.
behind the cylinder valves, 2) a modification to the cylinder heating process, reducing the rate of heat applied to the cylinders,3) an alternate valving configuration reducing the time required to burp cylinders to an evacuation header and 4) collection of cylinder void space gas samples after modified heating for analysis of trapped gases.
Ex'.ent 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 The event demonstrated that pressure rises experienced while heating Russian cylinders can occur more rapidly than previously believed. Cylinder heating procedures need to be strengthened to improve operator ability to control pressure increases and provide a means to detect an unequal distribution of UF..
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