Nuclear Criticality Safety

From AMCGMedia

The FETCH code allows modelling of the transient behaviour of fissile solutions, with sloshing and pressure feedback. It is therefore of great use in nuclear criticality safety cases, and is here applied to fissile solutions in tanks with both continuous filling and step reactivity insertion.

About FETCH

FETCH is a general geometry finite element transient coupled criticality/multiphase CFD code. It has been benchmarked against CRAC, SILENE and TRACY experiments and has the unique capability (based on detailed gas/bubble modelling) to calculate pressure waves. There is more information available about FETCH...

The radiation transport sub-model treats the whole containment structure (which includes the water jacket in the case of the JCO accident and the dilute Pu simulations), while the multi-phase CFD module treats only the tank contents.

Simulation Animations

Below are animations of simulations performed using FETCH. These include:

Initial modelling of accident at the JCO company
Fissile Uranium solution in a drum (CRAC, SILENE & TRACY experiments)
Fissile Plutonium in a tank
More examples of coupled Neutron Radiation & Multiphase flow (2D & 3D)

Initial modelling of accident at JCO company

Two preliminary cases have been modelled: continuous filling at a rate of 1 l/s (to simulate the pouring of the 'last bucket') and, for comparison, the addition as a step reactivity change. The solution concentration is 370 g/l with 18.8% enrichment.

Continuous filling

Step reactivity