Barros Sílvia, Gallego Eduardo, Lorente Alfredo, Gonçalves Isabel F, Vaz Pedro, Vega-Carrillo Héctor René
Instituto Superior Técnico, Instituto Tecnológico e Nuclear, Universidade Técnica de Lisboa, Estrada Nacional 10, Sacavém 2686-953, Portugal.
Radiat Prot Dosimetry. 2013;154(3):346-55. doi: 10.1093/rpd/ncs246. Epub 2012 Sep 18.
The Neutron Measurements Laboratory at the Nuclear Engineering Department of the Polytechnic University of Madrid consists of a bunker-like room and was built for neutron dosimetry research purposes and measurements. The facility includes a 74-GBq ²⁴¹Am-Be neutron source placed inside a neutron Howitzer container. The source can be moved to the irradiation or to the storage position. In this work, a Bonner sphere spectrometer (BSS) was used to measure the neutron fluence spectra with the source in both positions. Ambient dose equivalent rates, *(10), were measured using a calibrated neutron area monitor LB6411 (Berthold). The measured count rates were used as input to the NSDann and NSDUAZ unfolding programs to obtain the neutron fluence spectra and *(10). Monte Carlo (MC) simulation methods were used to model the system and to calculate the neutron fluence rate and the ambient dose equivalent rate at the measurement points. The comparison between NSDUAZ and NSDann resulted in relative deviations up to 6.87 % in the total neutron fluence rate and 7.18 % in *(10) values, despite the differences in the shape of the spectra obtained for the irradiation position. Comparing with the measured values, the *(10) values obtained with the unfolding programs exhibit a maximum relative deviation of 12.19 %. Taking into account the associated uncertainties, MC simulations seem to be in reasonable agreement with measurements. A maximum relative deviation of 15.65 % between computed and measured *(10) values was obtained. The computed count rates were applied to the unfolding programs to calculate the total neutron fluence rate and a maximum deviation of 12.83 % was obtained between the original values calculated by NSDann. A sensitivity test showed that the NSDann unfolding program is very sensitive to the uncertainties of the BSS count rates.
马德里理工大学核工程系的中子测量实验室由一个类似掩体的房间组成，建造该实验室的目的是用于中子剂量学研究和测量。该设施包括一个放置在中子榴弹炮容器内的74GBq的²⁴¹Am-Be中子源。该源可移动至辐照位置或储存位置。在这项工作中，使用了一个邦纳球谱仪（BSS）来测量源在两个位置时的中子注量谱。使用经过校准的中子区域监测仪LB6411（伯托尔德公司）测量环境剂量当量率*(10)。将测量的计数率用作NSDann和NSDUAZ解卷积程序的输入，以获得中子注量谱和*(10)。使用蒙特卡罗（MC）模拟方法对系统进行建模，并计算测量点处的中子注量率和环境剂量当量率。尽管辐照位置获得的谱形状存在差异，但NSDUAZ和NSDann之间的比较导致总中子注量率的相对偏差高达6.87%，(10)值的相对偏差高达7.18%。与测量值相比，通过解卷积程序获得的(10)值的最大相对偏差为12.19%。考虑到相关的不确定性，MC模拟似乎与测量结果合理吻合。计算值与测量的*(10)值之间的最大相对偏差为15.65%。将计算的计数率应用于解卷积程序以计算总中子注量率，NSDann计算的原始值之间的最大偏差为12.83%。灵敏度测试表明，NSDann解卷积程序对BSS计数率的不确定性非常敏感。
