Accuracy improvement of MCNP simulation model by correcting counting-loss and proposal of a methodology of alarm-threshold optimization for radiation portal monitors

Abstract

Thousands of radiation portal monitors (RPMs) have been deployed worldwide to detect and deter the smuggling of nuclear and radiological materials. To optimize the operational capabilities of RPMs, tests with various sources should be conducted and Monte Carlo N-Particle (MCNP) transport code can be one of the alternatives. To use MCNP for the test, the developed simulation model should be validated with experimental results and phenomena, which are not simulated in MCNP code, should also be corrected. In this study, we precisely measure the dead time of the RPM counting system by using a proposed new method. And, we developed an MCNP-based RPM simulation model and the accuracy of the simulation model was improved by correcting counting-loss based on the dead time. In addition, we proposed a methodology of alarm-threshold optimization for RPMs operated in Rep. of Korea.