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Radiation Protection and Safety in Radiotherapy
Published in Kwan Hoong Ng, Ngie Min Ung, Robin Hill, Problems and Solutions in Medical Physics, 2023
Kwan Hoong Ng, Ngie Min Ung, Robin Hill
Solution:The photonuclear interaction (gamma, n).Since practical therapy rooms need concrete walls at least two X-ray tenth value layers thick, adequate concrete shielding for the photons will always be adequate for the neutrons as well. However, great care should be taken if iron or lead is used for part of the shielding. Not only the attenuation of neutrons is poorer but interactions in iron or lead can create problem. Hydrogenous material provides best shielding for neutrons. In general, sandwich arrangements of lead, steel and polyethylene or concrete (hydrogenous material) are needed to provide adequate shielding for neutron.The maze must be sufficiently long and appropriately designed to reduce neutron flux. A neutron door including paraffin wax (which is a good neutron moderator) and boron (which is a good absorber of thermal neutrons) may be required.Neutrons can result in activation products. These are typically short-lived with half-life of the order of minutes. They mostly occur in the treatment head and closing the collimators prior to entering the room can reduce dose to staff. It is also advisable to let activation products decay prior to entering the room (>10 min) after prolonged use of high-energy photons (e.g., for commissioning).
Ionizing Radiation
Published in Martin B., S.Z., of Industrial Hygiene, 2018
When neutrons are absorbed by stable matter, they result in radioactive matter called activation products. Many commercially available radionuclides (e.g., C-14, P-32,1-125, Co-60) are activation products made by neutron activation of stable isotopes in a nuclear reactor.
Reactor Physics Analysis Assessment of Feasibility of Using Advanced, Nonconventional Fuels in a Pressure Tube Heavy Water Reactor to Destroy Long-Lived Fission Products
Published in Nuclear Technology, 2021
While the focus of this study is on the transmutation/consumption/destruction of seven key LLFP isotopes, it is also recognized that minor actinides and various neutron activation products are of concern for long-term storage in DGRs since they will also contribute to long-term radiation dose and radiotoxicity. Activation products are those radioactive isotopes produced by neutron activation of different elements and isotopes found in reactor structural components and coolant during reactor operations. Some of the long-lived activation products are produced by the irradiation of trace impurities of certain elements. Examples of such long-lived activation products include 36Cl (Thalf-life = 301 000 years), 14C (Thalf-life = 5730 years), and 41Ca (Thalf-life = 103 000 years) (Refs. 5 and 6).
Development of Tracer Particles for Positron Emission Particle Tracking
Published in Nuclear Science and Engineering, 2023
Thomas Leadbeater, Andy Buffler, Michael van Heerden, Ameerah Camroodien, Deon Steyn
An alternative labeling technique is to use physical activation processes. Provided that suitable reactions can be found for activating naturally occurring materials, ion irradiation produces positron-emitting species via nuclear capture and transmutation within the material of interest. In this case the activation products are formed directly from the material atoms and remain tightly bound within the particle used as the target. For sufficient activity (100 μCi to 2 mCi), the number of atoms transformed is minute compared to the number composing a macroscopic particle. Disregarding any physical changes caused by the process itself (the most significant being damage caused by heating), the direct activation process can be regarded as noninvasive.