ML20247F120

Forwards 30 Day Event Rept Re Discovery That Some Autoclave Ci Valves Were Not Capable of Closing When Relying on Safety Related Backup Air Supply Reservoirs.Revised Rept Scheduled for 980617

ML20247F120
Person / Time
Site:	Portsmouth Gaseous Diffusion Plant
Issue date:	05/07/1998
From:	Jonathan Brown UNITED STATES ENRICHMENT CORP. (USEC)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GDP-98-2020, NUDOCS 9805190153
Download: ML20247F120 (3)

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A om so.rsy comp.ny May 7,1998 '

GDP-98-2020 -

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' United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-001 l

Portsmouth Gaseous Diffusion Plant (PORTS)

Docket No. 70-7002 Event Report 98-05

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l Pursuant to the 10CFR 76.120(d)(2), Enclosure 1 provides the required 30-day Event Report for an event that resulted from the discovery that some autoclave containment isolation valves were not capable of closing when relying on their safety related backup air supply reservoirs. Investigation and testing activities are continuing to determine the root cause and corrective actions for this event.

This report will be revised following completion of these activities. The revised report is scheduled j

' for June 17,1998. There are no new commitments contained in the report.

Should you require additional information regarding this event, please contact Scott Schoil at (740) 897.2373.

1 Sincerely, f?cr7F Z w

. Morris Brown General Manager Portsmouth Gaseous Diffusion Plant Enc:osures: As Stated cc:

NRC Region III, Regional Administrator E

NRC Resident Inspector, PORTS 9905190153 990507 PDR ADOCK 07007002

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W P.O. Box 800, Ponsmouth. OH 45661 4

Telephone 614-897-2255 Fax 614-897-2644 http://www.usec.com

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p-Omces in Livermore. CA Paducah. KY Ponsmouth, OH Washington. DC L-_-____-___:-

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L GDP 98-2020 Page 1 of 2 p

l Event Report 98-05 l

Description of Event f

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On -April 9,1998, at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br />, while in Mode Vll Shutdown, Operations personnel wer..

performing a functional check on Autoclaves #1 and #2 in the X-342 facility. In response to'a NRC inquiry conceming the adequacy of containment valve surveillance testing, the operator performed

a containment isolation valve closure test with the normal plant air supply isolated. The purpose of l

this test was to verify that containment isolation valves were capable of closing with the safety l

related backup air supply. The testing demonstrated that several valves on Autoclave #1 and #2 -

failed to close as designed when the normal plant air supply was valved off. At the time of this l;

discovery, it was not known if the redundant containment isolation valves in the affected l

' penetrations were operable during the time period that the backup air supply was degraded. As a result, the failure of the containment isolation valves to close on demand under a simulated loss of the non-safety related plant air supply was reported in accordance with 10CFR76.120 (c)(2)(i).

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The containment valves that failed to close are valves having air-to-close actuators that are connected to air reservoirs that supply closing air pressure if the normal plant air supply is lost. Air leaks within the containment valve air reservoir systems allowed the backup air pressure to fall below the

. pressure required to close the valves. Both of these autoclaves were inoperable at the time of' L

discovery. All autoclaves on plantsite were declared inoperable until Operations could determine whether this condition existed on other autoclaves in the X-343 and X-344 Buildings.

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Cause of Event.

The direct cause of the event was leaking autoclave backup air reservoir systems. When the plant

air supply was valved off during testing, leaks in the air reservoir systems allowed the air pressure to drop on some systems to the point where the valves would no longer close.

L Investigation and testing activities are continuing to determine the root cause and corrective actions for this event. This report will be revised following completion of these activities.

A review of testing performed on air-to-close containment isolation valves indicated that quarterly j

. surveillance testing only verified that containment valves close upon receipt of a containment signal 1

at normal air pressure. The simulated loss of the non-safety related plant air system was not included in post maintenance or quarterly surveillance testing.

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GDP 98-2020 Page 2 of 2 Event Report 98-05 i

i A testing program was initiated to determine if any other air-to-close autoclave containment valves would fail to close without normal plant air pressure available. Out of the 48 valves that have been tested,15 failures were identified. The backup air systems have been repaired and the failed valves have been tested satisfactorily for all autoclaves which have been returned to service. The backup air systems will be tested and repaired prior to returning the remaining autoclaves to service.

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' Engineering performed a review to determine if there were any other plant systent which utilize the air-to-close valve design in "Q" safety system applications. The review identified that similar air

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to close valves were installed in the ERP, LAW and Tails Withdrawal stations. Testing was H

conducted on these valves and all passed satisfactorily. Several additional valves were identified in the X-705 calciner system. Since the calciners are currently shutdown, these valves will be tested

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. prior to returning the calciner to service.

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Engineering has also initiated a review to verify that other TSR safety systems and their supporting systems are adequately tested to verify performance of their intended safety function.

A review of similar events found that on January 23,1996, two Parent Cylinder Safety Valves (PCSV) failed to close during an inadvertent containmem actuation on Autoclaves #2 and #3 in X-344. Building. The corrective actions for that event included actions to initiate periodic testing of the PCSV air supply panels to ensure they maintained an acceptable leak rate. However, these actions.were not extended to include other autoclave air-to-close valves and did not include requirements to verify that containment isolation valves would close on demand with a simmated loss of plant air.

1 Corrective Actions 1

The corrective actions will be provided with the revised report.

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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Lessons Learned

'Ib Lessons Leamed will be provided with the revised report.

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