The purpose is to calculate the flux of the gamma radiation outside the steel box. The flux can then be used to determine how much heat in the form of gamma-ray energy that escapes the container. This implies that the shape, composing material and dimensions of the container must be known since the energy spectrum of the escaping gamma-rays depend strongly on it. The gamma flux clients currently contain the dimensions of a container that have been used to measure the heat of spent fuel assemblies and it is the heat loss from that particular container that is the goal.
The ultimate goal is to have an approximation to the distribution of this heat generation, and use that information when designing a safe encapsulation for final storage of spent nuclear fuel. With the heat loss determined, it is possible to measure the residual thermal power of the spent fuel more accurately. This is needed to be able to more optimally pack the assemblies in a possible final storage of the spent fuel.