title: Fission, critical mass and safety--a historical review.
abstract: Since the discovery of fission, the notion of a chain reaction in a critical mass releasing massive amounts of energy has haunted physicists. The possibility of a bomb or a reactor prompted much of the early work on determining a critical mass, but the need to avoid an accidental critical excursion during processing or transport of fissile material drove much that took place subsequently. Because of the variety of possible situations that might arise, it took some time to develop adequate theoretical tools for criticality safety and the early assessments were based on direct experiment. Some extension of these experiments to closely similar situations proved possible, but it was not until the 1960s that theoretical methods (and computers to run them) developed enough for them to become reliable assessment tools. Validating such theoretical methods remained a concern, but by the end of the century they formed the backbone of criticality safety assessment. This paper traces the evolution of these methods, principally in the UK and USA, and summarises some related work concerned with the nature of criticality accidents and their radiological consequences. It also indicates how the results have been communicated and used in ensuring nuclear safety.
authors.affiliation: geoff567@tiscali.co.uk
authors.forename: Geoff
authors.initials: G
authors.lastname: Meggitt
mesh_terms: D049673:History, 20th Century; D049674:History, 21st Century; D038622:Internationality; D008956:Models, Chemical; D009680:Nuclear Fission; D009686:Nuclear Physics / Q000266:history*; D011835:Radiation Protection / Q000266:history; D018788:Radioactive Hazard Release / Q000517:prevention & control*; D011874:Radiometry / Q000266:history*; D018570:Risk Assessment / Q000266:history*; D017751:Safety Management / Q000266:history*