Konheiser J, Naumann B, Ferrari A, Brachem C, Müller S E
Helmholtz-Zentrum Dresden-Rossendorf, Postfach 510119, 01314 Dresden, Germany.
J Radiol Prot. 2016 Dec;36(4):819-831. doi: 10.1088/0952-4746/36/4/819. Epub 2016 Oct 11.
Calculations of the shielding and estimates of soil activation for a medical cyclotron are presented in this work. Based on the neutron source term from the O(p,n)F reaction produced by a 28 MeV proton beam, neutron and gamma dose rates outside the building were estimated with the Monte Carlo code MCNP6 (Goorley et al 2012 Nucl. Technol. 180 298-315). The neutron source term was calculated with the MCNP6 code and FLUKA (Ferrari et al 2005 INFN/TC_05/11, SLAC-R-773) code as well as with supplied data by the manufacturer. MCNP and FLUKA calculations yielded comparable results, while the neutron yield obtained using the manufacturer-supplied information is about a factor of 5 smaller. The difference is attributed to the missing channels in the manufacturer-supplied neutron source terms which considers only the O(p,n)F reaction, whereas the MCNP and FLUKA calculations include additional neutron reaction channels. Soil activation was performed using the FLUKA code. The estimated dose rate based on MCNP6 calculations in the public area is about 0.035 µSv h and thus significantly below the reference value of 0.5 µSv h (2011 Strahlenschutzverordnung, 9 Auflage vom 01.11.2011, Bundesanzeiger Verlag). After 5 years of continuous beam operation and a subsequent decay time of 30 d, the activity concentration of the soil is about 0.34 Bq g.
本文介绍了医用回旋加速器的屏蔽计算和土壤活化估算。基于28 MeV质子束产生的O(p,n)F反应的中子源项，使用蒙特卡罗代码MCNP6（Goorley等人，2012年，《核技术》，第180卷，第298 - 315页）估算了建筑物外的中子和伽马剂量率。中子源项使用MCNP6代码、FLUKA（Ferrari等人，2005年，INFN/TC_05/11，SLAC - R - 773）代码以及制造商提供的数据进行计算。MCNP和FLUKA计算得出了可比的结果，而使用制造商提供的信息获得的中子产额约小5倍。差异归因于制造商提供的中子源项中缺少的通道，该源项仅考虑了O(p,n)F反应，而MCNP和FLUKA计算包括了额外的中子反应通道。使用FLUKA代码进行土壤活化计算。基于MCNP6计算的公共区域估计剂量率约为0.035 μSv/h，因此显著低于0.5 μSv/h的参考值（2011年《辐射防护条例》，2011年11月1日第9版，联邦公报出版社）。在连续束流运行5年并随后衰变30天后，土壤的活度浓度约为0.34 Bq/g。
