Nuclear criticality safety for fissile materials outside reactors - Safety controls in conducting subcritical neutron multiplication measurements in situ
1 Subject content and application scope
This standard specifies the safety requirements and implementation rules for neutron multiplication measurements in situ of subcritical fissile assembly.
This standard is applicable to the neutron multiplication measurements in situ of subcritical fissile assembly; it shall also be used for reference purpose for measurements in situ of other reactivity indexes of subcritical fissile assembly.
2 Terms
2.1
fissile assembly (assembly)
system consisting of fissile material and other components that influence the reactivity
2.2
reactivity
quantity that characterizes the degree to which a fissile assembly deviates from a critical state, which is proportional to (keff-1)/keff, where keff is the effective multiplication factor for the assembly; the reactivity of a critical assembly is zero; the reactivity of a subcritical assembly is a negative quantity indicating the degree of subcriticality
2.3
neutron multiplication (multiplication)
for the purpose of this standard, it signifies a neutron counting rate that is sensitive to reactivity change of a fissile assembly and often normalized (or corrected) to the counting rate that would result if there were no fissions
2.4
reactivity index
parameter (such as the prompt neutron decay constant) that can characterize the reactivity of an assembly or from which the reactivity of the assembly can be deduced
