Online ISSN: 1884-4111 Print ISSN: 0033-8303
Radioisotopes 69(12): 365-373 (2020)


放射化した加速器室コンクリートに対する除染計画とその実施先端医学薬学研究センターにおけるPETデリバリー製造用サイクロトロン加速器室の廃止措置の研究事例Decontamination Plan for the Concrete of the Activated Accelerator Room and Its Implementation: A Case Study in the Decommissioning of the PET Cyclotron Room at the Medical and Pharmacological Research Center Foundation

1一般財団法人先端医学薬学研究センター臨床研究開発部Department of Clinical Research and Development, The Medical and Pharmacological Research Center Foundation

2高エネルギー加速器研究機構放射線科学センターRadiation Science Center, High Energy Accelerator Research Organization (KEK)

3JFEエンジニアリング株式会社JFE Engineering Co., Ltd.

受付日:2019年3月29日Received: March 29, 2019
受理日:2020年8月6日Accepted: August 6, 2020
発行日:2020年12月15日Published: December 15, 2020

本報は強く放射化した加速器室コンクリートに対する除染の実施例である。先端医学薬学研究センターの加速器室の除染を行った。コンクリートの表面線量率はサーベイメータを用いて50 cmメッシュで測定した。放射能濃度の深度分布はコアボーリングにより7か所で得た。これらから詳細に放射化領域を見積もり,斫り除去した。表面線量率は検出限界以下になった。細かなメッシュでの除去深度の決定は,放射性廃棄物の削減に貢献した。

Herein, we present the case study of the decontamination of highly activated concrete in the accelerator room. The activated cyclotron room for pharmaceutical for the positron emission tomography (PET) in the Medical and Pharmacological Research Center Foundation (Ishikawa, Japan) was decontaminated. The contact dose rates of the concrete walls, floor, and ceiling were measured at 50 cm mesh using a NaI survey meter. The depth profiles of specific activity in the concretes were obtained by core boring at seven different places. The activated concrete regions were estimated in detail based on the relationship between the measured contact dose rates and depth profiles of the specific activity. The activated concrete was chipped and removed based on the estimated activated region. Then, through remeasurement, it was confirmed that the removal of the activated concrete was completed. The measurement of the contact dose rate using the NaI survey meter could determine the removal depths of the concrete at short range mesh. This contributed to the reduction of radioactive waste.

Key words: activated concrete; decommissioning; decontamination; accelerator room; Cyclotron

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