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
Sub-category
Sub-category of FEP
Ondraf Niras FEP Number
Ondraf Niras FEP Number
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]