正电子发射成像回旋加速器屏蔽材料防护性能

Protection characteristic of shielding materials towards radiation of an 11MeV positron emission tomography cyclotron

计算了11MeV正电子发射成像回旋加速器18 O(p,n)18 F反应的双微分截面数据,并采用蒙特卡罗模拟计算方法,分析了单一材料及复合结构对特定辐射源的防护性能。采用单一材料,质量分数为73.8%的重混凝土的防护效果最佳,经过90cm厚屏蔽层的衰减,距离辐射源正前方1m处的总剂量降低约5个量级;复合结构采用多层结构,材料选用铁及硼酸溶液,同样厚度即可达到与重混凝土相同的防护效果,密度可降低至少20%。

An 11 MeV cyclotron used for production of positron emission radionuclide aiming at positron emission tomography （PET） imaging produces a huge quantity of instant neutron and gamma ray radiation.For shielding this kind of accelerator,a self-shielding bunker-like structure is employed,which can be designed with Monte Carlo method.The discrete dual-differential section data are calculated first to obtain the input data for Monte Carlo code,with which the protection characteristics with a single layer and composite structure of various materials are simulated next.The results show that with a single layer,the heavy concrete which has 73.8% iron content brings greatest protection characteristic among all of the materials included in this paper and attenuates the total dose rate about 100 kilo times at the position of 1 m far away from the radiation source with 0° emission angle with thickness of 90 cm.With materials of iron and boracic acid liquor,a particular composite structure can bring the same characteristic with the same thickness and reduce the total density about 20 % at least.