ML20138J466
| ML20138J466 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 05/01/1997 |
| From: | Allen D UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-97-2003, NUDOCS 9705080225 | |
| Download: ML20138J466 (5) | |
Text
~
United Statzs Enrichment Corporation 2 Democracy Center 6903 nockledge Dave Bethesda, MD 20817 l
Tet, (301) S64-3200 liileulStilles Fax: (301) 564-3201 li lSirirliment Corporatient May 1,1997 GDP 97-2003 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Portsmouth Gascous Diffusion Plant (PORTS)- Docket No. 70-7002 - Preliminary Event Report 97-03 Pursuant to Safety Analysis Report (SAR), Section 6.9, Table 6.9-1, J (2), Enclosure 1 provides the required 30 day written Preliminary Event Report (ER) for an event involving a high condensate level shutoff actuation at the Portsmouth Gaseous Diffusion Plant. Investigation activities are continuing with a fmal report targeted for June 12,1997. There are no new commitments contained in this preliminary report.
Should you require additional information regarding this event, please contact Scott Scholl at (614) 897-2373.
Sincerely, 4
Dale Allen General Manager Portsmouth Gaseous Diffusion Plant DIA:Schell:me
/
Enclosure l
I l
cc:
C. Cox/D. Ilartland, NRC Resident Inspectors
[
nRC Regie-iii F.
l
!F 288n usum "
lliIlllllil!I,1 Illl PDR Offices in Paducah. Kentucky Portsmouth, Ohio Washington, DC
o United States Nuclear Regulatory Comraission i
May 1,1997 Page Two t
Distribution Robert L. 'Woolley 1.j bec:
1
' J. Adkins, HQ J. Anzelmo, PORTS j
J. Bolling, PORTS l
'I 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 3
R. Lipfert, PORTS A. Rebuck-Main, HQ R. D. McDermott PORTS J. Miller, HQ.
J. Mize, PGDP J. Morgan PORTS J. Oppy, PORTS It Robinson, PORTS
]
S. Routh, HQ S. Scholl, PORTS B. Sykes, PGDP D. Thompson, PORTS j
R. Wells, HQ l
PORTS Re::ords Management RM: PORTS 97-890-090 l
o Docket No. 70-7002 I
Page1of3 Event Report 97.03 Preliminary Report Description of Event On April 3,1997, at 1750 Autoclave (AC) #2 in the X-342 was in Mode II heating a 48 inch Uranium Hexafluoride (UF ) cylinder when the audible alarm for steam shutdown was received.
6 Operators located ut the AC #2 control panel observed that both the "A" and "B" condensate probe lights were on, indicating the high condensate level shutoff (HCLS) safety system had actuated. Steam supply block valve FV-1613 was verified to be in the closed position, stopping steam flow to the autoclave as designed. This actuation occurred approximately one hoc.r and twenty five minutes into the heating cycle. A HCLS actuation is reporwble in accordance with the Safety Analysis Report (SAR) Table 6.9-1, J (2).
Prior to the initiation of this heating cycle, AC #2 had been shutdown as a result of a HCLS actuation that occurred on March 25,1997. The direct cause of this previous HCLS actuation was determined to be a low pressure condition in the roll motor buffer air pressure system. At the time of the April 3,1997, HCLS actuation, operators noted that the buffer air light was on before and after the actuation occurred. This indicated that buffer air pressure was adequate and was not the cause of this event.
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 6
event of a UF release from the cylinder that could cause either high Hydrogen Fluoride pressure 6
as the result of the reaction between UF and water or the excessive moderation of an unsafe 6
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.
Cause of Event The direct cause of the HCLS actuation was a failed steam trap which prevented condensate from draining from the autoclave. Condensate subsequently accumulated in the drain line causing the condensate level probes to actuate. The failed steam trap was an Armstrong Steam Trap Model No. 814T, inverted bucket type trap.
Following the HCLS actuation the condensate drain was inspected and no debris er restrictions were found.
I Maintenance disassembled the steam trap for inspection and found the steam trap bucket had I
fallen offits hook. The bucket hook attaches to a lever assembly that opens and closes the steam j
J
Docket No. 70-7002 Page 2 of 3 Event Report 97-03 Preliminary Report trap discharge valve. The mechanical steam trap operates on the difference in density between steam and water. Steam entering the inverted and submerged bucket causes the bucket to float, which removes the weight otrof the lever assembly and closes the discharge valve. Condensate entering the steam trap changes the bucket to a weight, wtich pulls the lever assembly down and opens the discharge valve. The lever assembly and the bucket are the only two moving parts in the steam trap.
Engineering personnel familiar with the autoclave operating history indicated that a similar steam trap failure was experienced by AC #2 on September 9,1996. At that time AC #2 was being returned to service following maintenance on the steam trap. The autoclave had been operating for approximately 15 minutes when a HCLS actuation occurred. The cause of the actuation was determined to be incorrect steam trap assembly that resulted in the bucket not being connected to the !cver assembly.
As a result of the September 9,1996, incident, additional post maintenance testing to verify proper steam trap operation was implemented. This testing requires operating an empty autoclave for approximately 30 minutes to ensure the steam trap cycles properly to expel condensate. This testing was performed successfully on the AC #2 steam trapjust prior to the April 3,1997, HCLS actuation. Since the autoclave operated for approximately one hour and twenty five minutes before the actuation occurred, it is believed that the steam trap was initially functioning correctly.
The root cause for the steam trap failure has not been determined at this time. Further engineering analysis is required to determine the steam trap failure mechanism. This event report will be revised when the root cause has been determined. The target date for submitting the revised report is June 12,1997.
Following replacement of the steam trap on April 10,1997, AC #2 was returned to service. The autoclave successfully completed four heating cycles without experiencing additional condensate level problems.
Corrective Actions The steam trap was replaced on April 10,1997, following verification that the AC #2 condensate system was free of debris or restrictions.
a
.... ~ _... _. _ _ _..__. _. _ _
i i
ei I
1 l
i DockeiNo. 70-7002 j
Page 3 of 3 j.
Event Report 97-03 j
Preliminary Report 1
Extent of Exposure ofIndividuals to Radiation or Radioactive Materials.
1 i-I There were no exposures crindividuals to radiation or radioactive rnaterials from this incident.
4 h
Lessons Learned j
i f'
Lessons learned wili be provided with the final event report.
)
\\
4 l-i 4
e 1
j 4
d 4
1, 2
i i
1
,m--
,_ _