，小迫 和明Takuma Noto, Kazuaki Kosako清水建設株式会社 Institute of Technology, Shimizu Corporation
医療用リニアック施設の遮蔽設計における照射室直下の免震層の実効線量計算について，「放射線施設のしゃへい計算実務マニュアル」に記載の迷路散乱X線の計算法を転用する場合の適用検証を行った。散乱比に十分大きい値を使用することで，詳細計算や実測値に比べ安全側の線量が得られ，遮蔽設計に適用可能であることを確認した。一方で，計算条件によっては詳細計算より1桁以上過大になるため，本手法を用いた遮蔽設計は過剰な遮蔽となる可能性がある。
This study verifies the applicability of a calculation method for estimating the effective dose in the seismic isolation layer directly under the irradiation room of a medical linac facility, by applying a simple calculation method for maze-scattered X-rays described in the “Practical Manual for Shielding Calculation of Radiation Facilities.” A sufficiently large scattering ratio value can be used to obtain a dose on the safe side compared with detailed calculations and measured values, thereby making it possible to apply this method to shielding design. On the other hand, depending on the calculation conditions, the dose exceeds the detailed calculation by more than one order of magnitude, which indicates that the shielding design may require excessive shielding.
Key words: shielding design; effective dose; calculation method; X-ray; linac; seismic isolation layer
© Japan Radioisotope Association 2026. This is an open access article distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) License (https://creativecommons.org/licenses/by/4.0/)© Japan Radioisotope Association 2026. This is an open access article distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) License (https://creativecommons.org/licenses/by/4.0/)
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