Event Notification Report for October 31, 2000
U.S. Nuclear Regulatory Commission
Operations Center
EVENT REPORTS FOR
10/30/2000 - 10/31/2000
EVENT NUMBERS
37477
Fuel Cycle Facility
Event Number: 37477
Facility: PADUCAH GASEOUS DIFFUSION PLANT
Region: 3 State: KY
Unit: [] [] []
RX Type: URANIUM ENRICHMENT FACILITY
Comments: 2 DEMOCRACY CENTER
6903 ROCKLEDGE DRIVE
BETHESDA, MD 20817 (301)564-3200
NRC Notified By: K. BEASLEY
HQ OPS Officer: BOB STRANSKY
Region: 3 State: KY
Unit: [] [] []
RX Type: URANIUM ENRICHMENT FACILITY
Comments: 2 DEMOCRACY CENTER
6903 ROCKLEDGE DRIVE
BETHESDA, MD 20817 (301)564-3200
NRC Notified By: K. BEASLEY
HQ OPS Officer: BOB STRANSKY
Notification Date: 10/31/2000
Notification Time: 22:40 [ET]
Event Date: 10/31/2000
Event Time: 17:15 [CST]
Last Update Date: 10/31/2000
Notification Time: 22:40 [ET]
Event Date: 10/31/2000
Event Time: 17:15 [CST]
Last Update Date: 10/31/2000
Emergency Class: NON EMERGENCY
10 CFR Section:
10 CFR Section:
Person (Organization):
DAVID HILLS (R3)
C.W. (BILL) REAMER (NMSS)
DAVID HILLS (R3)
C.W. (BILL) REAMER (NMSS)
24-HOUR NRC BULLETIN 91-01 REPORT
"At 1715 CST on 10-31-00, the Plant Shift Superintendent (PSS) was notified of a violation of an NCSA In the C-400 building. A negative air machine (NAM) was operated in the C-400 Sear Disassembly Area with an expired calibration date on the magnehelic gauge in violation of NCSE GEN-09. The magnehelic gauge is a safety related item relied on to measure differential pressure across each filter bank to ensure that uranium is not excessively loaded onto filters and to prevent fissile material accumulating in the NAM in quantities grater than a maximum subcritical mass.
"SAFETY SIGNIFICANCE OF EVENTS:
"The NAM was operated with an expired calibration date on the magnehelic delta pressure gauge, The system design limits the ability to accumulate a critical mass, however, a control for double contingency was lost.
"POTENTIAL CRITICALITY PATHWAYS INVOLVED (BRIEF SCENARIO(S) OF HOW CRITICALITY COULD OCCUR:
"In order for a criticality to be possible, the NAM would have to be operated with a differential pressure above 20 In. WG. The filters would have to be fully loaded with fissile/potentially fissile material and dislodged from the filters more than two times, accumulating in the bottom of the NAM.
"CONTROLLED PARAMETERS (MASS, MODERATION, GEOMETRY CONCENTRATION ETC.):
"Double contingency for this scenario is established by Implementing two controls on mass.
"ESTIMATED AMOUNT, ENRICHMENT, FORM OF LICENSED MATERIAL (INCLUDE PROCESS LIMIT AND %WORST CASE CRITICAL MASS):
"The assay of any material is less than 2.75 wt. % U235.
"NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES:
"Double contingency for this scenario is established by implementing two controls on mass.
"The first leg of double contingency is an administrative control to limit the delta pressure across the prefilter to a maximum of 12 in. WG or an increase across the HEPA filter to 2 in. WG by using calibrated instrumentation, This will limit the filter loading to less than a subcritical mass. Since the instrumentation was outside the calibration date, this control must be assumed to be violated.
"The second leg of double contingency is a safety-related Item, which limits the ability of the NAM to exceed a differential pressure of 20 In. WG. This is accomplished by limiting the motor power rating. This prevents an accumulation of more than the subcritical mass. This control was not violated.
"Since double contingency is based on two controls on mass and the differential pressure control was lost, double contingency was not maintained.
"CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEMS AND WHEN EACH WAS IMPLEMENTED:
"Access to the area has been controlled by ropes and signs and the NAM unit has been tagged to prevent use. The NAM will not be operated until inspection, filter change, and replacement of the magnehelic gauge is performed."
The NRC Senior Resident Inspector has been notified of this event.
"At 1715 CST on 10-31-00, the Plant Shift Superintendent (PSS) was notified of a violation of an NCSA In the C-400 building. A negative air machine (NAM) was operated in the C-400 Sear Disassembly Area with an expired calibration date on the magnehelic gauge in violation of NCSE GEN-09. The magnehelic gauge is a safety related item relied on to measure differential pressure across each filter bank to ensure that uranium is not excessively loaded onto filters and to prevent fissile material accumulating in the NAM in quantities grater than a maximum subcritical mass.
"SAFETY SIGNIFICANCE OF EVENTS:
"The NAM was operated with an expired calibration date on the magnehelic delta pressure gauge, The system design limits the ability to accumulate a critical mass, however, a control for double contingency was lost.
"POTENTIAL CRITICALITY PATHWAYS INVOLVED (BRIEF SCENARIO(S) OF HOW CRITICALITY COULD OCCUR:
"In order for a criticality to be possible, the NAM would have to be operated with a differential pressure above 20 In. WG. The filters would have to be fully loaded with fissile/potentially fissile material and dislodged from the filters more than two times, accumulating in the bottom of the NAM.
"CONTROLLED PARAMETERS (MASS, MODERATION, GEOMETRY CONCENTRATION ETC.):
"Double contingency for this scenario is established by Implementing two controls on mass.
"ESTIMATED AMOUNT, ENRICHMENT, FORM OF LICENSED MATERIAL (INCLUDE PROCESS LIMIT AND %WORST CASE CRITICAL MASS):
"The assay of any material is less than 2.75 wt. % U235.
"NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES:
"Double contingency for this scenario is established by implementing two controls on mass.
"The first leg of double contingency is an administrative control to limit the delta pressure across the prefilter to a maximum of 12 in. WG or an increase across the HEPA filter to 2 in. WG by using calibrated instrumentation, This will limit the filter loading to less than a subcritical mass. Since the instrumentation was outside the calibration date, this control must be assumed to be violated.
"The second leg of double contingency is a safety-related Item, which limits the ability of the NAM to exceed a differential pressure of 20 In. WG. This is accomplished by limiting the motor power rating. This prevents an accumulation of more than the subcritical mass. This control was not violated.
"Since double contingency is based on two controls on mass and the differential pressure control was lost, double contingency was not maintained.
"CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEMS AND WHEN EACH WAS IMPLEMENTED:
"Access to the area has been controlled by ropes and signs and the NAM unit has been tagged to prevent use. The NAM will not be operated until inspection, filter change, and replacement of the magnehelic gauge is performed."
The NRC Senior Resident Inspector has been notified of this event.