The application of mathematical modeling for commercial nuclear instrument design, development, and calibration

Mathematical modeling of nuclear instruments has evolved over the last 40 years. First came simple curve fitting operations; then Monte Carlo processes were made available to large research facilities; and then, due to the power of the computer, became widely available to normal radiation instrumentation users. Canberra has been extensively using MCNP for design and calibration of large and complicated instrumentation to create and optimize designs that would be prohibitively expensive with radioactive sources. For gamma spectroscopy applications we have developed a software application called ISOCS that combines MCNP pre-calculations and ray-tracing operations for speed. Examples of the use of these tools are presented including the design of a neutron dose-rate survey probe, the design of the optimum shield around Ge detector, the computation of the optimum counting time for moving source, the design of neutron counting safeguards systems, the design of neutron and gamma assay systems or determining the optimum source-detector geometry for waste drum assay