1994 Page 3 of 4 b. more than one controlled parameter is used for a given criticality pathway, and the control systems for more than one controlled parameter have been replaced or modified. The occurrence of any unanticipated or unanalyzed event for which the safety significance of the event or corrective actions to re-establish the double contingency principle are not readily identifiable. Any case where it is determined that a criticality safety analysis was deficient and where the necessary controlled parameters were not established or maintained. Any event involving a controlled parameter previously identified by NRC or the licensee as requiring immediate reporting to NRC, and where the double contingency principle cannot be re-established within 4 hours after the initial observation of the event. Controlled parameter means a measurable variable whose value is maintained within established limits, to ensure the safety of an operation.
Control system means a collection of restrictions that effectively functions as a single control.
Double contingency means, for each criticality pathway, the use of control systems in such a way that two unlikely, concurrent, independent control system failures would have to occur before an inadvertent criticality would be possible. It is expected that criticality safety events will be promptly evaluated and that appropriate management and technical personnel will be available 24 hours a day to perform such evaluations. It should be emphasized that it is important that NRC be notified of events related to criticality safety and that if there is any doubt as to whether an event should be reported, the NRC should be contacted. Information Notice Treatment Addressees may wish to review their criticality safety reporting procedures to ensure that they meet or exceed the reporting criteria described in this information notice. If you have any questions about the information in this notice, please contact the technical contact listed below or the appropriate regional office.