This paper presents an extension to a point kinetics model of fissile solution undergoing a
transient through the development and addition of correlations which describe neutronics
and thermal parameters and physical models. These correlations allow relevant parameters
to be modelled as a function of time as the composition of the solution changes over
time due to the addition of material and the evaporation of water from the surface of the
solution. This allows the simulation of two scenarios. In the first scenario a critical system
eventually becomes subcritical through under-moderation as its water content evaporates.
In the second scenario an under-moderated system becomes critical as water is added before
becoming subcritical as it becomes over-moderated. The models and correlations used
in this paper are relatively idealised and are limited to a particular geometry and fissile solution
composition. However, the results produced appear physically plausible and demonstrate
that simulation of these processes are important to the long term development of
transients in fissile solutions and provide a qualitative indication of the types of behaviour
that may result in such situations.