Uranyl fluoride (UO_2F_2) is the most common form of holdup in uranium enrichment facilities. Quantitative measurement of UO_2F_2 is necessary for the purposes of safeguards, nuclear criticality safety evaluations and for nuclear material control and accounting. Because UO_2F_2 is a dense material that severely attenuates gamma rays, neutron measurements are often the method of choice for performing quantitative measurements. UO_2F_2 produces neutrons via~19F(α,n)~22Na reactions and by spontaneous fission, with almost all of the neutrons produced from ~234U and ~238U. Estimates of thick target yields and ~19F(α,n)~22Na cross sections have been previously made, and subsequent calculations performed to estimate neutron specific activity for UO_2F_2. Literature searches revealed no prior studies that involved the direct measurement of neutrons produced by uranium in the form of UO_2F_2. Neutron specific activity estimates from thick target yields and ~19F(α,n)~22Na cross sections vary widely, from 257.8 n/s/g ~234U to 183.8 n/s/g ~234U. An additional complication is that UO_2F_2 exposed to moist air readily forms hydrates, with the commonly accepted upper bound being UO_2F_2 ● 2H_2O. The presence of H_2O affects neutron production via the ~19F(α,n)~22Na reaction. The purpose of this study was to perform measurements on items containing UO_2F_2 to determine the neutron specific activity of ~234U and ~238U in both dry and hydrated UO_2F_2.
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机译：铀酰氟（UO_2F_2）是铀浓缩设施中最常见的滞留形式。为了保障措施，核临界安全性评估以及核材料控制和核算，必须对UO_2F_2进行定量测量。由于UO_2F_2是一种致密材料，会严重衰减γ射线，因此中子测量通常是进行定量测量的首选方法。 UO_2F_2通过〜19F（α，n）〜22Na反应并通过自发裂变产生中子，几乎所有中子都由〜234U和〜238U产生。先前已经进行了厚靶材产率和〜19F（α，n）〜22Na截面的估算，并进行了后续计算以估算UO_2F_2的中子比活度。文献检索显示，以前没有研究涉及直接测量铀以UO_2F_2形式产生的中子。根据厚靶材产量和〜19F（α，n）〜22Na截面估算的中子比活变化很大，从257.8 n / s / g〜234U到183.8 n / s / g〜234U。另一个复杂因素是，暴露于潮湿空气中的UO_2F_2容易形成水合物，通常公认的上限为UO_2F_2●2H_2O。 H_2O的存在通过〜19F（α，n）〜22Na反应影响中子产生。这项研究的目的是对包含UO_2F_2的物品进行测量，以确定在干燥和水合UO_2F_2中〜234U和〜238U的中子比活。
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