The MERCURAD dose rate modeling software for D and D operations in nuclear facilities

A thorough knowledge of both the structures to be dismantled and their environment is a prerequisite for optimising operations of dismantling. This allows to guarantee a safe, economical and in limited time dismantling. From this approach, the use of a modeling software like MERCURAD is particularly indicated. Indeed, from measurements of dose rates, from the use of a tool like CARTOGAM for gamma cartography and from the standard spectra of the different areas in the installation which can be characterized with ISOCS, it is possible to define the radiological characteristics of the radioactive sources present on the site. This knowledge, preliminary to dismantling work, allows, on one hand to optimize the work according to the dose rate amounts during the operations of dismantling, and on the other hand to optimize the dismantling costs. With these objectives in mind, during the past two years, Canberra Eurisys, in co-operation with the CEA and COGEMA, has been developing the MERCURAD tool. This software uses the results of MERCURE 6.3 dose rate calculation software developed by the CEA; it makes the most of a powerful and user-friendly man-machine interface. The display of the 3D scenes and the calculation speed offer new possibilities to people competent in health physics, to engineers and to service companies specialized in the nuclear sector. The calculated quantities are the dose rates, the H*(10) ICRP74 equivalent dose rates, the overheating and the direct photonic fluence. The last 6.3 release of MERCURE integrates a new methodology for the calculation of the build-up factors for the multiple screens. These new algorithms developed by the CEA use of neural networks technique and make it possible to obtain a better accuracy of calculations. The present communication develops the principles of design of this tool, its use and the first on-site experience obtained. (authors)