Since the development of positron emission tomography in 1937, the number of medical cyclotrons used in producing radioisotopes (RI) has risen sharply. In its operation, the structural materials of a medical cyclotron...
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Since the development of positron emission tomography in 1937, the number of medical cyclotrons used in producing radioisotopes (RI) has risen sharply. In its operation, the structural materials of a medical cyclotron and the concrete shielding of its vault are activated by neutrons. In analyzing domestic and international decommissioning practices, the dismantling characteristics of medical cyclotrons result in a large amount of radioactive wastes, such as concrete, although their activity level is very low. In the United States, the dismantling plan must be established by the applicant. The decommissioning funding plan (DFP) is a financial assurance demonstration based on a site-specific cost estimate of decommissioning the facility. In 10 CFR 30.35, NRC requires the submission of DFP in the case of the possession and use of unsealed byproduct materials with a half-life of greater than 120 days and in quantities exceeding 10(5) times that of the applicable quantities. The dismanding of the Seoul National University Hospital (SNUH) cyclotron (TR-13) was performed in December 2012. Some of the risks resulting from this dismantling are related to radioactive wastes, as well as issues concerning dismantling costs. Hence, we propose introducing the DFP at the authorization stage. DFP will be helpful in preparing reliable decommissioning plans for safe decommissioning and unexpected early decommissioning in the future. DFP can also contribute in reducing radioactive waste and in decreasing the decommissioning cost by preventing excessive establishments. This study provided an overview of the decommissioning aspects of the SNUH cyclotron and the necessity of adopting the DFP for decommissioning medical cyclotrons.
根据医用回旋加速器的物理要求,确定了医用回旋高频腔的具体结构设计方案。在加速电压较高、空间有限的情况下提升高频腔的品质因数,结构设计为1/2波长线的竖腔。为避免腔体在实际工作中由发热变形引起频率漂移,本次设计中采用微调环调谐结构来保证频率稳定度的要求。本文利用Microwave Studio CST程序对腔体的电磁场分布、品质因数Q_0、表面电流分布、耦合电容、微调环进行了详细的分析与仿真计算。与实际测量值进行对比,两者比较吻合,并对产生的误差进行了分析讨论。
Co-55 (t1/2=17.53 h) was produced by 150 μA irradiation of a natural nickel target using 15 MeV protons. It was separated from the irradiated target material by two ion exchange chromatography steps with a radiochemi...
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Co-55 (t1/2=17.53 h) was produced by 150 μA irradiation of a natural nickel target using 15 MeV protons. It was separated from the irradiated target material by two ion exchange chromatography steps with a radiochemical yield of >95% and was used for the preparation of [55Co]vancomycin ([55Co]VAN). Optimization studies were per- formed using Co-57 due to its longer half-life. Cobalt-57 (t1/2=271.79 d) was produced by irradiation of a natural nickel target with 150 μA current of 22 MeV protons. The 57Co was separated from the irradiated target material using a no-carrier-added method with a radiochemical yield of >97%. Both products were controlled for radionuclide and chemical purity. The solutions of [55Co]VAN were prepared (radiochemical yield>80%) starting with 55Co acetate and vancomycin at room temperature after 30 min. A precise solid phrase extraction (SPE) method was developed using Si Sep-Pak in order to purify/reconstitute the final formulation for animal studies. [55Co]VAN showed a radiochemical purity of more than 99%. The resultant specific activity was about 1.15 TBq/mmol. It is proved that the tracer is stable in the final product and in presence of human serum at 37°C up to 24 h. Biodistribution study of [55Co]VAN in normal rats was undertaken for up to 72 h.
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