Design criteria and the principles underlying the UKAEA code of practice on the provision of criticality alarm systems

Design principles and criteria for criticality detection and alarm systems are given based on the requirement to detect different types of criticality excursion and the need to take account of the developments in radiation detectors. The characteristics of a criticality incident are described in terms of the minimum incident of concern (1015 fissions occurring in a duration between 1 ms and 1 minute) and the radiation field. Criteria for the threshold of detection are derived for integrating and rate-of-change systems employing gamma-ray or neutron detectors. General guidance is given on the principles to apply in the selection and siting of criticality detectors