During the afternoon of March 7, 2016, UUSA [Urenco USA] operators moved drums containing uranic material into an
IROFS [Items Relied On For Safety] controlled array. This
IROFS requires initial and independent operator verification to ensure a subcritical geometry exists prior to adding any new material to the array. The operators moving the drums did not perform the administrative
IROFS; that is, neither an initial nor an independent
verification were completed prior to adding five additional drums to the array.
UUSA management and nuclear criticality staff have ensured the drums are in a safe and subcritical configuration.
The drums contain clean up materials contaminated with UF6 at unknown levels of enrichment. A nuclear criticality did not occur. The array is in a subcritical geometry. No external events are affecting this event. No emergencies have been, nor will any be declared.
No state or other federal agencies will be notified. No press releases are planned.
Number and types of controls necessary under normal operating conditions: One enhanced sole IROFS. The enhancement is an initial verification and an independent verification of geometry prior to movement of material into the area.
Number and types of controls which functioned properly under upset conditions: Neither the IROFS initial verification, nor the independent verification of geometry were performed before movement occurred.
Number and types of controls necessary to restore a safe situation: A member of operations management passed through during a routine plant tour, questioned the operators, and determined that the drums had been placed in a safe geometry in the array without performing the required IROFS surveillance.
Safety significance of events: Loss of geometry controls preventing criticality.
Safety equipment status: The array is in a subcritical geometry.
Status of corrective actions: Corrective actions to be developed.
- * * UPDATE FROM SLAMA TO SHOEMAKER ON 4/13/16 AT 1542 EDT * * *
Isotopic analysis has been conducted for the material in the stored drums; the uranium enrichment is characterized as depleted. As such, criticality was not possible during the operations and the as-found configuration reported in Event Notification 51776 on March 7, 2016. However, the required IROFS was not implemented. The event is hereby being reclassified as a 24-Hour Event Notification in accordance with 10 CFR 70 Appendix A (b)(2).
The previously reported IROFS was available and should have been implemented at the point of storage to ensure safe storage array configuration, thus meeting 10 CFR 70.61 performance requirements. During the ongoing Root Cause Evaluation for this event, it was discovered and documented that an additional IROFS was not implemented during the March 7, 2016 movement evolution. This additional IROFS requires the use of a transfer cart for movement from the point of generation to the point of storage. This cart is to ensure proper spacing between the container and any materials which may be passed during movement. This is a sole administrative IROFS enhanced with initial and independent verifications.
As stated above, analysis has been completed which characterizes the material as depleted UF6. As such, during the movement of the drums, criticality was not possible. The required IROFS was available, however the failure to implement applicable controls resulted in a situation in which no reliable barrier was in place to provide assurance that interaction control would be maintained during movement. The failure to implement this additional IROFS during movement is hereby classified as a 24-Hour report in accordance with 10 CFR 70 Appendix A (b)(2). The information required per 10 CFR 70.50 (c)(1) is same as that contained in the event description [of the original notification].
Notified the R2DO(Bonser) and the
NMSS Events Notification Group via email.