Masroor Ahmad

Study of gamma irradiation effects on coaxial cables

In nuclear industry, RG58C/U cables are widely used in high radiation environments. The incident gamma rays knock out electrons from cable core to the outer shield and hence, results in flow of current. Moreover, radiations also induce conductivity in the dielectric resulting in an increase in the leakage current. The two processes cause a steady state radiation induced current in the coaxial cable. This radiation induced current degrades the actual signal from the detector. In this paper, the initial experimental results performed at Pakistan Institute of Nuclear Science and Technology (PINSTECH) and Nuclear Medicine Oncology and Radiotherapy Institute (NORI) are presented. It is observed that radiation induced current has a prompt jump and then raises slowly to a saturation value around 35 pA. RG58C/U coaxial cable was exposed to different dose rates and the normalization factors were determined to be 4.66×10-14 Coul/rad.cm and 2.52×10-14 Coul/rad.cm for spent fuel element and Co-60 sources respectively.

Development of reactor physics Monte Carlo model for MIT BEAVRS

Computer simulations play a very important role in the fields of science, engineering and technology. In the field of nuclear engineering, computer simulations help save tremendous amount of time, money and reduce unnecessary exposure to radiations. Development of new tools and methodologies need to be verified against trusted benchmarks. Benchmarks not only validate the tools but help users gain confidence of using those tools to obtain accurate results. In this study, Benchmark for Evaluation And Validation of Reactor Simulations (BEAVRS) set up by Computational Reactor Physics Group (CRPG) of Massachusetts Institute of Technology (MIT) is modelled using open source Monte Carlo based code OpenMC. Monte Carlo based reactor physics code offer the benefit of exact 3D geometry along with continuous energy treatment as compared to homogenized geometry and multi-group treatment used in deterministic transport theory and diffusion theory based codes. Integral reactor physics parameters are calculated and compared with the reported benchmark values. This academic exercise will help gain expertise and confidence in the use of OpenMC code and also help to analyse/forecast the computational resources for such calculations.