January 3, 1961, Idaho Falls, Idaho, USA: Reactor goes out of control.

Acute Radiation Death Resulting from an Accidental Nuclear Critical Excursion on 30 December 1958

Acute Radiation Death Resulting from an Accidental Nuclear Critical Excursion on 30 December 1958

January 3, 1961, Idaho Falls, Idaho, USA: Reactor goes out of control.

A criticality accident is an uncontrolled nuclear fission chain reaction.

Criticality accident shall refer to an accident caused by an uncontrolled chain reaction of nuclear fissions.

September 23, 1983 – Buenos Aires, Argentina A criticality accident took place at the RA-2 facility in an experimental test reactor.

September 23, 1983 – Buenos Aires, Argentina A criticality accident took place at the RA-2 facility in an experimental test reactor.

The nuclear fuel may be any one of the following U235, U233, Pu239.

Tellurium-132 and its daughter 132I are important in the first few days after a criticality.

It has been designed expressly for the evaluation of criticality risk in nuclear installations, i.e. the occurrence of an uncontrolled chain reaction outside an operational reactor core (reactivity accident).

In the latest case at the Fukushima Daiichi nuclear plant, such a criticality accident has yet to happen.

ISO 16117:2013 provides a methodology to estimate a reasonably maximal value of the number of fissions of a postulated criticality accident.

The Chernobyl accident is not universally regarded an example of a criticality accident, because it occurred in an operating reactor at a power plant.

The void coefficient was negative, so the reactivity of nuclear fission was suddenly heightened, resulting in a nuclear explosion from the prompt criticality.