CIRCEE v1 A versatile tool for criticality accident dose assesment
Résumé
CIRCEE is a calculation code developed by the French Atomic Energy Commission (CEA), allowing fast assessment of operational dose over complex geometries. It is used to assess dosimetric consequences of a criticality accident. More specifically, it can be used both during the preliminary studies phase (isodoses curves for safety report preparation or emergency response planning, CAAS implementation and validation) and during crisis management (effective dose estimation, intervention planning).An early development stage of CIRCEE has been presented in a talk at the 2009 NCSD edition [1]. Since then, a heavy code rewriting increased its reliability and maintainability while keeping its performance at an excellent level. Now in a stable production version, and following the grant of several international patents, it's aiming to short term availability to the industry.CIRCEE is based on the straight-line attenuation method. However giving correct dose estimates in some configurations (non-lacunar geometries, no highly diffusive material), this method by itself is not suitable to estimate doses inside buildings. CIRCEE circumvents these limitations by using simple corrections, which allow it to consider diffusion inside shielding materials and reflection inside rooms. This results in a prompt assessment of dose or dose rate within complex geometries directly imported from CAD models (as built), while limiting the calculation time to a few minutes for entire facilities.Even if Monte Carlo calculation codes can give much more precise results than simple deterministic codes such as CIRCEE, there are drawbacks to their use reliable estimation of dose over the whole floor surface of a building is not straightforward (homogeneous convergence in space for both neutrons and gammas), and the calculation is very resource-intensive and time-consuming. However, these methods give a reference point against which codes like CIRCEE can be validated. Within this context, a comparison has been performed against TRIPOLI 4, the CEA reference Monte Carlo code for neutron and gamma transport, on several simplified geometric models, each one of which designed to test an identified potential weakness.A concrete use case illustrating CIRCEE capabilities and potentialities will also be presented.