共查询到18条相似文献,搜索用时 171 毫秒
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测量了中国原子能科学研究院研究性重水反应堆厂房外周围环境中的中子、γ剂量当量率分布。反应堆在13MW热功率下运行时,其厂房外周围马路的平均中子剂量当量率达5.2nSv·h~(-1),约为天然中子本底的1.6倍;平均γ剂量当量率(不包括高剂量区的西马路数据)达124nSv·h~(-1),约为γ本底的1.3倍。还分析了反应堆厂房外西马路γ剂量率偏高的原因。 相似文献
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混合辐射场中子剂量、剂量当量的测量需进行中子、γ分辨。依据各种辐射沉积线能的不同,组织等效正比计数器(TEPC)具有一定的中子、γ分辨能力。本文采用自制的圆柱形TEPC在5SDH-2加速器单能中子辐射场进行了微剂量谱测量,对其中子、γ分辨技术进行了探讨分析。采用137Cs纯γ辐射微剂量谱匹配法,在252Cf、241Am-Be中子辐射场进行了中子、γ分辨研究。分辨后的中子剂量当量与约定真值一致性较好,表明TEPC用于中子、γ混合辐射场的吸收剂量、剂量当量测量是可行的。 相似文献
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目的选用一个合适的计算方法对X射线能量大于10 MV的工业探伤用直线加速器机房进行屏蔽计算,确定屏蔽厚度。方法以一台DZ-12/5500型工业探伤用直线加速器机房为研究对象,参考NCRP 151号报告、GBZ/T220.2—2009等资料中提供的计算方法进行计算和分析。结果该加速器机房有用线束方向混凝土屏蔽墙厚度需278 cm,其它三面墙分别需要182、195、204 cm;顶盖厚度为110 cm混凝土时,天空反散射在距机头20 m处造成的剂量当量率非常小;"Z"字型迷道入口处总周剂量当量为115.69μSv,其中X射线的散射和泄漏辐射总剂量当量为2.43μSv/周,中子辐射剂量当量为102.96μSv/周,中子俘获γ射线剂量当量为10.30μSv/周。结论对实际建成运行的机房检测结果的分析后发现,上述计算值与检测值比较吻合,说明本文选用的计算方法和选取的参数可行。 相似文献
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为了准确刻度中子剂量当量仪的性能参数以及验证中子剂量当量仪设计的准确性,在252Cf(D2O)源实验室进行实验校准之前,先采用MCNP5分别模拟分析实验室中空气、墙壁以及石蜡桶对探头中子计数的影响。模拟实验表明,在理想条件下,随着源与探头距离的增大,中子计数率越来越小;空气对中子计数的影响呈先增加后减小再增加的趋势,中子散射率不超过10%,且距离越近,空气散射的中子对探头计数的影响越小;当探头与源距离260cm左右时,石蜡桶对探头计数的影响最小,达到1%;墙壁对中子计数的影响随着探头与源距离增大而逐渐增大,当探头与源距离为360cm时,墙壁散射的中子是源中子计数的2倍;当源与探头距离为175cm时,空气、墙壁以及石蜡桶对源中子的散射最小,测量数据最精确。并通过实验与模拟数据对比表明,源与探头距离在125–300cm之间,计数率误差不超过30%,符合中子剂量测量的技术要求,从而验证了此中子剂量当量仪设计的准确性。 相似文献
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10—in单球rem计测量中能重离子反应中子剂量当量的理论修正 总被引:1,自引:0,他引:1
中能重离子反应出射的中子具有较复杂的能谱,在穿过混凝土屏蔽层后,其能谱发生显著的变化。考虑到中子rem计的能量响应,在中能重离子反应出射中子理论计算能谱和角分布的基础上,估算了屏蔽层外中子能谱的变化和用10-in单球rem计在屏蔽层外测量中能重离子反应中子剂量当量时的理论修正系数。 相似文献
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采用蒙特卡罗方法研究了脉冲中子地层元素测井仪闪烁晶体材料、井眼屏蔽体厚度、硼套表面密度等设计参数对仪器测井响应的影响。结果表明:LaBr3晶体的测井响应特性优于BGO晶体;高矿化度盐水对测量结果影响很大,井眼屏蔽体厚度为1.2 cm时,可屏蔽60%以上井眼γ射线;硼套中10B表面密度达到0.065 g/cm2时,可消除仪器外壳材料产生的俘获γ本底;俘获能谱的探测深度随孔隙度的增加而减小,非弹性散射能谱对不同孔隙度地层的探测深度基本一致,约为14 cm。 相似文献
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241Am-Be中子源被广泛用于实验研究,为保护实验人员免受中子及γ射线照射,需要设计适当的屏蔽。利用蒙特卡罗方法计算中子透射不同材料后的能谱分布与剂量,优选各层屏蔽材料种类与厚度,设计一套241Am-Be中子源紧凑型屏蔽装置。装置由内而外采用钨+聚乙烯+含硼聚乙烯+不锈钢进行防护,外表面周围剂量当量率H*(10)低于10μSv/h,满足辐射防护要求。同时对装置内部热中子、超热中子和快中子注量分布进行研究,确定装置快中子和热中子输出通道最佳位置。在辐照装置同时开放快中子和热中子通道进行实验测试时,需要设置距离大于130 cm的控制区,以保障操作人员安全。 相似文献
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Kazuaki Kosako Koji Oishi Takashi Nakamura Kouichi Sato Takashi Kamiyama Yoshiaki Kiyanagi 《Journal of Nuclear Science and Technology》2013,50(12):1188-1197
Following the angular distribution measurements of bremsstrahlung photons and photoneutrons, we measured the distributions of photon and neutron dose rates in the iron and concrete assemblies using a copper target bombarded by 18, 28 and 38 MeV electrons at the electron linear accelerator (linac) of Hokkaido University. In this experiment, seven types of shielding assemblies of iron and concrete layers were used and the photon and neutron dosemeters were inserted into the assemblies to get the depth–dose distribution. The measured results were compared with the results calculated using the Monte Carlo code MCNP5 to verify the calculated results. The calculated results of the ambient dose equivalent rates were in agreement with the measured results within 30% accuracy. Since no work on the radiation behavior in the shielding wall of medical linac room has ever been reported, this work gives valuable benchmark data for the detailed shielding design with high accuracy. 相似文献
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LiGui-Sheng 《核技术(英文版)》1998,9(2):109-112
Correction factors of both Rem-meters,the 10 inch diameter sigle-sphere Remmeter and the standard A-B Rem-meter,were estimated for measuring high energy neutron dose equivalent outside a concrete shielding wall and the effects that the emitted neutron spectra become remarkably“Harder“ peneetrated through a concrete shielding wall,and the energy response of the Rem-meter were taken in account.The estimated results could be applied in the measurement of neutron dose equivalent for the intermediate energy heavy ion reactions to avoid the difficulty induced by the energy response of the Rem-meters. 相似文献
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基于强流氘氚中子源科学装置HINEG设计了一套快中子照相准直屏蔽系统。采用中子输运设计与安全评价软件系统SuperMC和ENDF/B-Ⅶ.0数据库计算了准直中子束的中子能谱及注量率、γ射线能谱及注量率、直射中子注量率与γ射线注量率比值(φd/φγ)、直射与散射中子注量率比值(φd/φs)、准直束中子注量率的不均匀度等特性参数,并采用MCNP5程序进行了对比验证。研究了准直屏蔽系统的内衬材料、尺寸等对特性参数的影响规律,并通过优化获取了最优设计方案。计算结果显示,在同等计算条件下,SuperMC计算结果与MCNP计算结果相对偏差小于1%,准直屏蔽系统的φd/φγ为50.1,φd/φs为5.7,在Φ30 cm视野范围内的中子注量率为4.80×107 cm-2•s-1,其中直射中子注量率为4.09×107 cm-2•s-1,中子注量率不均匀度为5.8%,满足快中子照相对准直束特性参数的要求。 相似文献
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Medical accelerators operating above 10 MV are a source of undesirable neutron radiations which contaminate the therapeutic photon beam. These photoneutrons can also generate secondary gamma rays which increases undesirable dose to the patient body and to personnel and general public. In this study, the Monte Carlo N-Particle MCNP5 code has been used to model the radiotherapy room of a medical linear accelerator operating at 18 MV and to calculate the neutron and the secondary gamma ray energy spectra and the dose equivalents at various points inside the treatment room and along the maze. To validate our Monte Carlo simulation we compared our results with those evaluated by the recommended analytical methods of IAEA Report No. 47, and with experimental and simulated values published in the literature. After validation, the Monte Carlo simulation has been used to evaluate the shielding performance of the radiotherapy room. The obtained results showed that the use of paraffin wax containing boron carbide, in the lining of the radiotherapy room walls, presents enough effectiveness to reduce both neutron and gamma ray doses inside the treatment room and at the maze entrance. Such evaluation cannot be performed by the analytical methods since room material and wall surface lining are not taken into consideration. 相似文献