RADIOACTIVITY.EU.COM

icon THE PHENOMENON

THE PHENOMENON

icon IN DAILY LIFE

IN DAILY LIFE

icon QUESTION OF DOSES

QUESTION OF DOSES

icon AT THE DOCTOR’S

AT THE DOCTOR’S

icon At the laboratory

At the laboratory

icon At the museum

At the museum

icon NUCLEAR ENERGY

NUCLEAR ENERGY

icon RADIOACTIVE WASTE

RADIOACTIVE WASTE

The aim of this web site is to explain radioactivity and its applications to the general public.

Criticality and reactivity of a reactor

In a reactor or an atomic bomb, the criticality factor k is, for each fission, the average number of secondary neutrons causing in turn a fission. The value of k determines whether the chain reaction become explosive (k greater than 1) or not (k less than 1). Criticality should remain equal to 1 in a reactor. Criticality excursions above this value are tolerated only if they are brief and do not exceed a few per thousand. The difference (k-1) to the unit value is called reactivity.

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