Design of fast neutron channels for topaz irradiation

• Published in: Nuclear engineering and design 2016-12, Vol.310, p.429-437
• Main Authors: Mohamed, Nader M.A., Gaheen, M.A.
• Format: Article
• Language: English
• Subjects: Aluminum; Boron; Boron carbide; Boxes; Channels; Irradiation; Neutron flux; Neutron irradiation; Neutrons; Occupational exposure; Radiation shielding; Radioactivity; Reactors; Simulation; Studies; Thermal neutrons; Topaz
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2016.11.001

•This work aims to design fast neutron irradiation channels for topaz irradiation.•The irradiation boxes are shielded using a martial contains B-10.•Calculations of neutron flux and heat generation were carried out using the MCNPX code and the effect on the reactor reactivity has been considered.•Experimentally, the worker exposure has been reduced to less than one-tenth and a decrease of 12months in the release time of the treated topaz has been achieved. The aim of this work is to design fast neutron irradiation channels for topaz irradiation at Egypt Second Research Reactor (ETRR-2) by shielding the aluminum boxes, used for topaz irradiation, with B4C (boron carbide) or manufacturing the irradiation boxes from aluminum contains boron. This in turn suppresses the thermal neutrons inside the box resulting in reduction of the residual radioactivity in topaz which decreases the worker exposure and release time. Simulation of the fast irradiation channels using the code: MCNPX showed that the thermal neutron component can be suppressed to less than one-tenth. ETRR-2 has many irradiation positions. The fast neutron flux distributions along the irradiation positions and the required irradiation times were calculated. The limiting conditions for safe operation of movable experiments are considered in the selection of the irradiation positions. That is the change in reactor reactivity due to the B-10 shield is below the reactivity limit for safe irradiation experiments. Heat generated during irradiation in topaz and in the material that contains boron was considered, as well. Experimentally, the worker exposure has been reduced to less than one-tenth and a decrease of 12months in the release time of the irradiated topaz has been achieved. Also adequate cooling of the shielded box during irradiation has been demonstrated.