Optimization of a measurement facility for radioactive waste free release by Monte Carlo simulation

A novel free release measurement facility (FRMF) was developed within the joint research project "Metrology for Radioactive Waste Management" of the European Metrology Research Programme. Before and during FRMF design and construction, Monte Carlo calculations with MCNPX and PENELOPE codes were used to optimize the thickness of the shielding, the dimensions of the container, and the shape of detector collimators. Validation of the numerical models of the FRMF detectors and the results of the optimization are discussed in the paper. - Highlights: • Monte Carlo simulations utilized for optimization of a novel free release facility. • Cosmic radiation and chamber walls contribute most to the background. • H⁎(10) rate inside the optimized facility decreased to 33% of the outside value