12-15 July 2011
Saint George Hotel
Africa/Johannesburg timezone
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Radiation Shielding calculations using MCNPX transport code for cost optimization of the shielding material to be used in the new cyclotron vault at iThemba Labs

Presented by Mr. Zipho NGCOBO on 14 Jul 2011 from 17:00 to 19:00
Type: Poster Presentation
Session: Poster2
Track: Track F - Applied and Industrial Physics


<p>Ion Beam Applications (IBA) commercial cyclotron (IBA Cyclone 70) with capability of accelerating protons up to 70MeV and 350µA of current is to be constructed at iThemba Labs to increase the capacity of the current facility. The two opposite simultaneous extraction of beams using the Carbon foil stripper, enable for the concurrent production of radioactive ion beam (RIB) for nuclear research and isotope production. This high energy beam is expected to have losses of about 10% in total meaning 70µA of the total beam will interact with surrounding materials during acceleration. Thus this proton beam is a possible radiation source, presenting a threat of ionising radiation. The cyclotron is mainly made of magnetic steel which is rather stable provinding local shielding inside the vault. There are not many significant openings for the radiation to rather escape in the less dense media to the surrounding other than in the extraction sides. Between the two poles of the cyclotron, the strip made of steel, which seals the two poles, is thick enough to shield radiation. Considering efficiencies at the extraction side of the cyclotron, it is expected that radiation contamination will accumulate and be transported to the vault and surroundings during cyclotron operations. Particles of concern are neutrons and photons formed during proton beam interaction. Bremstrahlung x-rays (photons) could be from proton acceleration and neutrons could be produced by (p, n) reactions. Photons and neutrons are not easy to shield. There is a need to simulate the radiation transport using MCNPX transport code so that the levels of doses can be investigated to provide extra safety cautions and adequate selection of materials and correct dimensions for shielding walls to keep the dose rates at acceptable levels. Additionally, water in the cooling system as it consists of Hydrogen isotopes that can react with protons to produce neutrons will also be investigated as it will increase the neutron flux into the vault.

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Room: Asteria

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