The Use of Monte Carlo techniques for the calibration of IAEA safeguards instrumentation

As computing power has become more affordable, the use of Monte Carlo radiation transport techniques for determining the response of safeguards instrumentation has become more widespread. At the International Atomic Energy Agency (IAEA) this trend is also evident. This paper will detail some of the efforts to determine absolute calibrations for nuclear material mass verification as well as relative detector responses in order to establish corrections for materials that are not well represented by calibration standards. In particular the paper will discuss the methodology used to absolutely calibrate a Uranium Neutron Collar for LWR-fuel (UNCL) for measuring WWER-1000 fuel assemblies and to determine burnable poison correction parameters for fuel with added boron. The verification of ²³⁵U enrichment in fresh fuel pellets using low resolution gamma ray detectors is currently based on predictive count rates derived from Monte Carlo simulations. This is being routinely applied by the IAEA through the use of automatically generated input files from sample information input by the user.