Determination of the neutron and gamma ray dose rates of the irradiating beam tubes of a pool-type research reactor by using Monte Carlo simulation and experimental detectors regarding radiation protection issues

In this paper, the reactor core, irradiating beam tubes, and radiological shields of a 5 MW open pool type Material Testing Reactor (MTR) are simulated in detail by using the MCNPX 2.6 code and its default library (i.e. mostly made of ENDF/B VI and VII). A safety assessment is performed and discussed based on the related health physics issues. Independently, dosimetry parameters are measured by using the Berthold LB 6411 neutron dose rate monitor and Berthold LB 123 Gamma dose rate monitor. Experimental results are used to benchmark the modeling and calculations especially regarding dosimetry, shielding, and health physics problems. Results are fairly appropriate for further calculations to be validated but some aging problems could be raised for a 50 years old research reactor particularly due to secondary gamma rate of the activated components. Then major beam tubes are characterized for high qualified irradiating applications. Moreover, external dose rates are estimated for empty beam tubes whenever radiological shields fail such as large break of beam tubes, hazardous seismic conditions, or any accident that can remove the plugs. Then, results are very important for the safety of the reactor operator to determine and establish emergency zones (i.e. yellow zones) and planning, respectively.