ASTM E704-13由美国材料与试验协会 US-ASTM 发布于 2013。
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ASTM E704-13 用铀的放射性活化测量反应速度的标准试验方法的最新版本是哪一版?
最新版本是 ASTM E704-19 。
5.1 Refer to Practice E261 for a general discussion of the determination of fast-neutron fluence rate with fission detectors.
5.2 238U is available as metal foil, wire, or oxide powder (see Guide E844). It is usually encapsulated in a suitable container to prevent loss of, and contamination by, the8201;238U and its fission products.
5.3 One or more fission products can be assayed. Pertinent data for relevant fission products are given in Table 1 and Table 2.
5.3.1 137Cs-137mBa is chosen frequently for long irradiations. Radioactive products8201;134Cs and8201;136Cs may be present, which can interfere with the counting of the 0.662 MeV8201; 137Cs-137mBa gamma rays (see Test Methods E320).
5.3.2 140Ba-140La is chosen frequently for short irradiations (see Test Method E393).
5.3.3 95Zr can be counted directly, following chemical separation, or with its daughter8201;95Nb using a high-resolution gamma detector system.
5.3.4 144Ce is a high-yield fission product applicable to 2- to 3-year irradiations.
5.4 It is necessary to surround the8201;238U monitor with a thermal neutron absorber to minimize fission product production from a quantity of8201;235U in the8201;238U target and from8201; 239Pu from (n,γ) reactions in the8201;238U material. Assay of the8201;239Pu concentration when a significant contribution is expected.
5.4.1 Fission product production in a light-water reactor by neutron activation product8201;239Pu has been calculated to be insignificant (lt;28201;%), compared to that from8201;238U(n,f), for an irradiation period of 12 years at a fast-neutron (E gt; 1 MeV) fluence rate of 18201;×8201;1011 cm−2 · s−1 provided the8201;238U is shielded from thermal neutrons (see Fig. 2 of Guide E844).
5.4.2 Fission product production from photonuclear reactions, that is, (γ,f) reactions, while negligible near-power and research-reactor cores, can be large for deep-water penetrations
测量 在测量之前,使用标准校准溶液对分析仪进行校准,检查校准特性的测量范围和稳定性, 用加标回收法测定样品中的铀浓度。 分析实例更多精彩推荐,请关注我们 ▼...
他们需要新的实验来说明游离的质子轰击铀原子核时究竟发生了什么。 最后,奥多想到了一个办法:用非放射性的钡作标记,不断地探测和测量放射性的镭的存在。如果铀衰变为镭,钡就会探测到。 他们先进行前期实验,确定在铀存在的条件下钡对放射性镭的反应,还重新测量了镭的确切衰变速度和衰变模式。这花了他们三个月的时间。 没等他们进行实质性的实验,莉泽就不得不逃往瑞典,躲避上台的希特勒纳粹党。...
选择水深大于1.5 m,水面直径大于2 m,无放射性污染的水域,将γ辐射仪用塑料布密封好,置于水下50 cm处,此时取得的读数即为自然底数。岩石中正常含量的放射性核素产生的仪器读数叫做岩石底数或背景值。各种岩石有不同的底数,可按统计法求取,作为正常场值。野外工作中,凡γ射线照射量率高于围岩底数三倍以上,受一定岩性或构造控制,性质为铀或铀钍混合者,该处称为异常点。...
Materials运用欧易/鹿明生物技术:UPLC-MS普筛、GC-MS普筛、转录组测序研究背景铀(U)是一种具有高放射性和长半衰期的典型工业污染物。...
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