M'SONE MSc Abstract - 2011

Supervisor : Mr Mr Zukilie Zibi : NECSA and Prof SH Connell : UJ

The schematic diagram of the Mineral-PET method.

Radiological Analysis by Monte Carlo Simulation of the Mineral-PET Activation System

MineralPET is a Research & Development project aimed at applying Nuclear Medicine techniques, like Positron Emission Tomography, to the identification and sorting of diamond-bearing kimberlite rocks. The “PET” acronym is derived from Positron Emission Tomography, the well know application of nuclear imaging techniques in diagnostic medicine. As positron emission by natural carbon does not occur spontaneously, it is necessary to produce the positron emitting 11C PET isotope by the photon induced 12C(γ,n)11C reaction. In the Mineral-PET system, there is therefore an activation stage using photons of 20-30 MeV which are generated by bremsstrahlung of electrons on a high-Z material. This process is carried out on the kimberlite feed rock stream which has been coarse crushed to a diameter of about 10 cm. The amount of positron emission signatures from the highly localised activated 11C in the diamonds is in very strong contrast to that of non-diamond sources of carbon which are dilutely and homogenously distributed in the kimberlite. The dominant background is from the oxygen present in the kimberlite which leads to the PET isotope 15O. The lifetime of 15O is 2 minutes compared to that of 11C which is 20 minutes, and so it is allowed to decay out in a hold hopper. The resulting rock stream can then be passed through a PET imaging system, with a modified PET algorithm optimised for on-line and real-time mineral applications. A graded high resolution ejection system can select out the diamondiferous kimberlite rocks.

This project will use both MCNP and GEANT4 to perform the Radiological Analysis of the radiation environment. This involves the simulation of the production of the high energy photon beam by bremsstrahlung from 40 MeV electrons on a tungsten target and the subsequent irradiation of the kimberlite rock stream in the irradiation hopper. The simulation will evaluate the primary sources of radiation (electrons, photons) as well as the secondary photo-induced radiation (γ,n), (γ,p), (γ,2n), (γ,ά) and the effects of the activation of the isotopic residues.