10MV医療用直線加速器からの漏洩放射線について : 第1報使用室迷路からの異常漏洩とその原因

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As the result of the survey of leakage X-ray from the treatment room, unusual high leakage value is found at the entrance to the treatment room. The leakage values at the other measurement locations are less than those expected from a shielding calculation. Layout of the treatment room is an ordinary construction, and no constructional defects are found. As a consequence of tracing the origin of this unusual leakage, it is concluded that neutrons produced in Linac leak from the treatment room through that the maze, and that the main contribution to the measured leakage radiation is that from neutron capture γ-ray in materials composing the maze, the door etc.. For the purpose of reducing the unusual leakage, a reconstruction of the room is performed by reducing an open area at the part of the entrance from the main room to the maze. At the entrance to the treatment room, initial measured X-ray dose equivalent rate is 5.8 mrem/h in the condition of the beam direction vertically downward, the fully closed field and output 4.65 Gy/min, but, after the reconstruction, its value reduces to 1.8 merm/h and measured neutron dose equivalent rate is 3.9 mrem/h in the same condition. The X-ray and neutron leakage values in the fully opened field are less than the above values. From X-ray leakage values before and after the reconstruction, it is deduced that initial neutron leakage dose equivalent rate is about 12 mrem/h in the fully closed field. When a treatment room to set up a Linac with the accelerative energy exceeding 10 MV is designed, it is suggested from the above facts that some plans to reduce neutron leakage through the maze must be taken into consideration. Also, in survey of leakage radiation from the treatment room, not only X or γ-ray but neutron survey is demanded.
公益社団法人日本放射線技術学会の論文
1982-03-01

10MV医療用直線加速器からの漏洩放射線について : 第1報使用室迷路からの異常漏洩とその原因

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10MV医療用直線加速器からの漏洩放射線について : 第1報 使用室迷路からの異常漏洩とその原因

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10MV医療用直線加速器からの漏洩放射線について : 第1報使用室迷路からの異常漏洩とその原因