Lawrence Livermore National Laboratory, Livermore, CA 94551-9900, USA.
Health Phys. 2013 Jun;104(6):580-8. doi: 10.1097/HP.0b013e31828d0134.
A detailed model of the Target Bay (TB) at the National Ignition Facility (NIF) has been developed to estimate the post-shot radiation environment inside the facility. The model includes the large number of structures and diagnostic instruments present inside the TB. These structures and instruments are activated by neutrons generated during a shot, and the resultant gamma dose rates are estimated at various decay times following the shot. A set of computational tools was developed to help in estimating potential radiation exposure to TB workers. The results presented in this paper describe the expected radiation environment inside the TB following a low-yield DT shot of 10(16) neutrons. General environment dose rates drop below 30 μSv h(-1) within 3 h following a shot, with higher dose rates observed in the vicinity (~30 cm) of few components. The dose rates drop by more than a factor of two at 1 d following the shot. Dose rate maps of the different TB levels were generated to aid in estimating worker stay-out times following a shot before entry is permitted into the TB. Primary components, including the Target Chamber and diagnostic and beam line components, are constructed of aluminum. Near-term TB accessibility is driven by the decay of the aluminum activation product, 24Na. Worker dose is managed using electronic dosimeters (EDs) self-issued at kiosks using commercial dose management software. The software programs the ED dose and dose rate alarms based on the Radiological Work Permit (RWP) and tracks dose by individual, task, and work group.
已开发出一个详细的国家点火装置（NIF）靶场（TB）模型，用于估算设施内部的后射击辐射环境。该模型包括 TB 内部存在的大量结构和诊断仪器。这些结构和仪器由射击过程中产生的中子激活，在射击后不同的衰减时间内估计其产生的伽马剂量率。开发了一组计算工具来帮助估算 TB 工人的潜在辐射暴露。本文介绍了在 10(16)中子低产 DT 射击后 TB 内部预期的辐射环境。一般环境剂量率在射击后 3 小时内降至 30μSv h(-1)以下，在少数组件附近（约 30cm）观察到更高的剂量率。在射击后 1 天，剂量率下降了两倍多。生成了不同 TB 级别的剂量率图，以帮助估算允许进入 TB 之前的射击后工人停留时间。主要组件包括靶室和诊断及光束线组件，由铝制成。TB 的近期可接近性由铝激活产物 24Na 的衰减驱动。使用商业剂量管理软件在 kiosk 上自行发放电子剂量计（ED）来管理工人剂量。该软件根据辐射工作许可证（RWP）对 ED 剂量和剂量率报警进行编程，并按个人、任务和工作组跟踪剂量。
