ML20197H626

Forwards Event Rept 97-01,rev 1,providing Notification of Change to Corrective Action Completion Date Re Installation of Upgraded Tails Withdrawal Variable Buffer Sys.List of Commitments,Including Revised C/A Date Also Encl

ML20197H626
Person / Time
Site:	Portsmouth Gaseous Diffusion Plant
Issue date:	12/23/1997
From:	Morgan J UNITED STATES ENRICHMENT CORP. (USEC)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GDP-97-2042, NUDOCS 9712310334
Download: ML20197H626 (6)

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Uniini.%m CnrichthenI Corp ration Decenber 23.1997 Umted States Noclear Regulatory Commission GDP 97-2042 Attention: Document Control Desk LWashington, D.C. 20555-0001 l

Portsmouth Gaseous Diffusion Plant (PORTS)- Docket No. 70-7002 - Event Report 97-01, Revision 1 -

Pursuant to the Safety Analysis Report (SAR), Section 6.9, Table 6.9-1, J (2), Enclosure I provides Event Report 97 01, Revision 1. The revised event report provides notification of a change to a corrective action completion date regarding the installation of an upgraded Tails Withdrawal variable buffer system. Changes fmm the previous report are marked with a vertical line in the right

- margin. Enclosure 2 is a list of con mitments made in the report, including the revised correctiv.:

action date.

Should you require additional information regarding this event, please contact Scott Scholl at (614) 897-2373.

Sincerely, e

.tmes B. M Acting Genera Manager Portsmouth Gaseous Diffusion Plant JBM:SScholl:kpb b d b A "

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,,,o Enclosures cc:

- NRC Resident inspector, PORTS

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- NRC Region lil, Regional Administrator

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United States Nuclear Regulatory Commission

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L'. Fink, PORTS J -D Fosson, PORTSL L R. Gaston, PORTS '-

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R. Lipfert, PORTS R. McDermott, PORTS L J. Miller, ifQL J. Mize, PGDP --

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B. Sykes; PGDP S. Toelle, HQ -

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Page1of3 Event Report 9741 i

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Description of Event '

L,On. March 20,i 1997, at 1409. hours lwhile performing withdrawal operations at the Tails Sides Withdrawal Station, the Cascade Automatic Data Processing (CADP) smoke detector, designated l

as SSWL, alarmed in Arca Control Room (ACR)_#2 in the X-330 Process Building. ' Operations f j

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personnel investigated the alarm and observed smoke emanating from the area of compressor 30

WB-1, which had been operating in the withdrawal mode. Operations personnel in the ama followed the "Sec & Flee" policy and evacuated the allbeted areaJ Building recall was sounded to have all tpersonnel report to their respective areas.'

{According to the Technical Safety Requireme 4ts for the Portsmouth Gaseous Diffusion Plant, the CADP smoke. detectors are required to be operable when the Tails Withdrawal Station is operating in Modes II, Ill, or IV. In this instance, the Tails Side Withdrawal was operating in Mode Ill, which would make the actuation of this' smoke detector n! arm reportable in accordance with the Safety

. Analysis Report, Section 6.9, Table 6.9-1, J (2)..

q Prior to initiating the withdrawal, the compressor was out of senice for repair of a leak at the compressor flange. At 1755 hours0.0203 days <br />0.488 hours <br />0.0029 weeks <br />6.677775e-4 months <br /> on March 19,1997, compressor 30 WB-1 was started. At 2330

' hours, compressor 30 WB-1 was charged with UF. and valved into service. On March 20,1997 at

- 1315 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />5.003575e-4 months <br />, the Tails Side Withdrawal was started. Within 54 minutes, at 1409 hours0.0163 days <br />0.391 hours <br />0.00233 weeks <br />5.361245e-4 months <br />, CADP smoke detector SSWL, located above compressor 30 WB-1, actuated. At 1412 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.37266e-4 months <br />, the Pyrotromes F

.smokehead XAH300B1, which provides a redundant smoke detection system in Tails, also fired.

At 1417 hours0.0164 days <br />0.394 hours <br />0.00234 weeks <br />5.391685e-4 months <br />, the compressor was shut down from the ACR and the alarm on SSWL cleared ' At

- 1419 hours0.0164 days <br />0.394 hours <br />0.00235 weeks <br />5.399295e-4 months <br />, an Operator wearing proper personnel protective equipment responded to the area and 7 found smoke emanating from the area of compressor 30 WB 1.

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. Additional emergency personnel were called and responded to the area. Emergency responders t

monitoring the area did not detect airborne contaminants. Health Physics reported all air samples s

and radiological surveys as less than detectable and no evidence of an UF. release. An "All Clear" was given on the building reca'l at 1506 hours0.0174 days <br />0.418 hours <br />0.00249 weeks <br />5.73033e-4 months <br />;

Following the All Clear, Operations and Maintenance personnel imestigated the affected equipment h

and found no evidence of a failed compmssor seal, which was considered the most likely source of b

J a'UF leak in this area.3Since there was no evidence indicating that the smoke originated from a UF 6

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( telease, plant personnel initiated an investigation to determine the source of the smoke.

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~ lDocket No. 70-7002?

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}Page 2 of 31 Enclosure lj

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Event Report 97-01<

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J On March 23,1997, maintenance removed a housing panel and found residue indicating that UF.

j l outgassing hr.d occurred. Visible contamination was found on and around the WWB-27 compressor _

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" discharge block valve. A leak check performed on the valve bellows at 1715 hours0.0198 days <br />0.476 hours <br />0.00284 weeks <br />6.525575e-4 months <br /> determined there

was a leak. On March 24,1997, following confirmation of an UF. outgassing as'the cause of the CADP alarm it was determined the~' occurrence was reportable 'o NRC.

! The valve with the failed bellows which caused the outgassing was a 4-inch, model G-17 gate valve,

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manufactured by the Crane Company.

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? The material that outgassed was enriched UF. at approximately 3.0% U-235.

Cause of Event :

2 The direct cause of the UF. release was failure of the aellows on the WWB 27 compressor discharge block: valve. The leaking bellows allowed the process gas to escape which set off the smoke detectors above the nearby compressor. The CADP UF Smoke Detection System SSWL-6 d'

smokehead and Pyrotronics smokehead XAll300B1 actuated in the Tails Withdrawal Area.

' The root cause of the outgassing was the design of the valve bufTer system. The purpose of the valve buffer is to prevent the buildup of UFiln the valve stem cavities by keeping the buffer pressure approximately 5 psi above the maximum process gas pressure. The valve bufTer system was designed to au omatically switch from a low pressure (10 psig) to a high pressure (25 psig) buffer supply as the process gas pressure increases. The high pressure supply flows through an orifice which limits'the buffer air flow rate. The bellows leak caused the buffer pressure to _ drop low enough, allo ~ wing the process gas to escape. To improve the ability of the butter system to prevent i

a UF. release, an enhancement to the system design has been identified - A new design will provide -

- a variable pressure buffer system which will maintain the bufTer air supply at a constant differential

- above the process pressure. -

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-l-The existing valve buffer system has operated without incident. in excess of 8 months, due in part 1

to the mutine integrity checks by Operatio'n's personnel. In addition,25% of the G-17 valve bellows I

<have recentlylbeen replaced;.'thus enhancing system reliability and reducing the probability of -l Loutgassing through a failed valve bellows.' The design of the enhanced variable buffer system is 1

complete and awaiting final appmval and preliminary field installation began December 15,1997.

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6-iDocket No. 70 7002

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Event Report 97.

Corrective Actions By March 1,1998, installation of a new, upgraded variable bufTer system which will maintain a il bufTer pressure above the process pressure at the Tails Withdrawal Station will be completed.

I Extent of Exposure ofIndividuals to Radiation or Radioactive Materials

- There were no significant exposures to individuals from this incident'to radiation or radioactive i

materials.' The operator who investigated the smoke alarm' submitted a sample for urinalysis. The l-bioassay results were below 5 ug/ liter for soluble uranium (flag level). ' he calculated intake w~as i

1.25 micrograms _of uranium. The limit for occupational workers is 10,000 micrograms of soluble I

uranium per week.

-l Lessons Learned Personnel responded appropriately to this event in accordance with the "See and Flee" policy.

A correctly operating buffer air system is necessary to mitigate the effects of small bellows leaks and

_ prevent releases from occurring.

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Docket No. 70-7002 -

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. Enclosure 2 '

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-i Event Report 97-01 i List of Commitments

.i By-March 1,1998, installation of a new, upgraded variable buffer system which will I

maintain a buffer pressure above the process pressure at the Tails Withdrawal Station will be 1

- completed.

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