Predicting accident characteristics by calculation

A set of convenient articulated calculations can enable the criticality safety specialist to predict the characteristics of a possible nuclear criticality accident. These calculations are tools that can be used efficiently in routine assessments without the need for detailed codes, which are best suited for retrospective interpretations of previous excursions. With these calculations, the criticality safety specialist can obtain an estimate of credible (as opposed to worst case) consequences, an understanding of the important controls to prevent inadvertent criticality, and an evaluation of the effectiveness of prompt evacuation. A set of calculations known as the Trombay criticality formula (TCF) can be used to calculate rates of reactivity insertion. The TCF is a set of computations that enables us to predict changes in either the critical size of k/sub eff/ following alternations in the geometrical or physical parameters. Changes in size, shape, density of the core, diluent concentration of the core, density of the reflector, and thickness of the reflector can be considered. To illustrate how these tools are used, the authors consider the assessment of a metallic plutonium system and an enriched uranium solution