Description

A self-sustaining process of nuclear fission in which each neutron released from fission triggers, on average, at least one other nuclear fission. Nuclear criticality requires a sufficient concentration and localised mass (critical mass) of fissile isotopes (e.g. U-235, Pu-239) and the presence of neutron-moderating materials in a suitable geometry. Includes both in-package criticality owing to the arrival of water and mechanical alterations, and out-of-package criticality as a result of chemical processes such as degradation and accumulation of uranium and/or plutonium as a result of dissolution and segregation.

Category

Category of FEP

Supercontainer EBS

Sub-category

Sub-category of FEP

Radiological processes

Ondraf Niras FEP Number

Ondraf Niras FEP Number

14

FEP Effects

Description of FEP Effects

Criticality may affect the thermal profile around the criticality event.

NEA TN2 IFEP Reference(s)

Related IFEPs from the NEA TN2 List of Proposed IFEP Revisions [NEA/RWM/R(2013)8]

3.2.6.5 Criticality.