[ RadSafe ] Article: Fission, critical mass and safety—a historical review

John Jacobus crispy_bird at yahoo.com
Fri May 4 14:51:39 CDT 2007

An interesting article if you into fission and safety,
which are not mutually exclusive.

Found in J. Radiol. Prot. 26 (2006) 141–159

Fission, critical mass and safety—a historical review
Geoff Meggitt

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.

What are the facts? Again and again and again – what are the facts? Shun wishful thinking,. . . avoid opinion, [and] care not what the neighbors think, . . .what are the facts, and to how many decimal places? You pilot always into an unknown future; facts are your single clue. Get the facts!” 
 "Time Enough for Love," Robert Heinlein, 1973

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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