1.1 本试验方法描述了通过活化反应测量反应速率的程序 54 Fe（n，p） 54 Mn。 1.2 该活化反应可用于测量能量高于约2.2 MeV的中子，以及长达约三年的辐照时间，前提是实践中描述的分析方法 E261 遵循。如果在超过三年的辐照期后对剂量计进行分析，则在没有先前撤回的剂量计的支持数据的情况下，不应依赖于在辐照结束前三年以上的辐照期内推断出的关于注量的信息。 1.3 采用合适的技术，裂变中子注量率大于10 8. 厘米 −2. ·s −1. 可以确定。然而，在存在高热中子注量率的情况下（例如，>2×10 14 厘米 −2. ·s −1. ) 54 应调查锰的损耗。 1.4 实践中参考了描述其他快中子探测器使用的详细程序 E261 . 1.5 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.6 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.7 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 请参阅指南 E844 用于指导中子剂量计的选择、辐照和质量控制。 5.2 参考实践 E261 关于用阈值探测器测定快中子注量率的一般性讨论。 5.3 金属箔或金属丝形式的纯铁易于获得和处理。 5.4 图1 显示了快中子反应的横截面与中子能量的函数关系图 54 Fe（n，p） 54 Mn公司 ( 1. ) . 3. 该图仅用于说明目的，以指示 54 Fe（n，p） 54 Mn反应。请参阅指南 E1018 用于推荐的列表剂量测定横截面。 图1 54 Fe（n，p） 54 Mn横截面 5.5 54 锰的半衰期为312.19（3）天 4. ( 2. ) 并发射能量为834.855（3）keV的伽马射线 ( 2. ) . 5.6 热中子或快中子相互作用引起的中子活化产生的干扰活动为2。 57878（46）-小时 56 Mn，44.494（12）天 59 Fe和5.2711（8）年 60 有限公司 ( 2. , 3. ) . （请参阅Ref的最新版本 ( 2. ) 对于目前接受的半衰期的更精确值。）来自的干扰 56 计数前等待48小时可以消除锰。虽然化学分离 54 从辐照铁中提取锰是消除锰的最有效方法 59 Fe和 60 Co，铁的直接计数 54 Mn可以使用高分辨率探测器系统或展开或剥离技术，尤其是在辐射期间剂量计被镉或硼覆盖的情况下。 当采用直接样品计数时，改变铁剂量计的同位素组成是消除外来活动干扰的另一种有用技术。 5.7 锰和铁的蒸汽压使得铁的锰扩散损失在700°C以上的温度下变得显著。因此，必须采取预防措施，避免锰的扩散损失 54 高温下铁剂量计中的锰。将铁剂量计封装在石英或钒中，将在高达约900°C的温度下含有锰。 5.8 小节 6. , 7. 和 8. 以下内容专门用于描述化学分离方法和随后的细菌计数 54 Mn活性。当选择直接计算铁剂量计时，这些部分 6. , 7. 和 8. 与放射化学分离有关的问题应忽略不计。 注1: 本试验方法的以下部分也适用于直接样品计数方法: 6.1 – 6.3 , 7.4 , 7.9 , 7.10 , 8.1 – 8.5 , 8.18 , 8.19 和 9 – 12 .

1.1 This test method describes procedures for measuring reaction rates by the activation reaction 54 Fe(n,p) 54 Mn. 1.2 This activation reaction is useful for measuring neutrons with energies above approximately 2.2 MeV and for irradiation times up to about three years, provided that the analysis methods described in Practice E261 are followed. If dosimeters are analyzed after irradiation periods longer than three years, the information inferred about the fluence during irradiation periods more than three years before the end of the irradiation should not be relied upon without supporting data from dosimeters withdrawn earlier. 1.3 With suitable techniques, fission-neutron fluence rates above 10 8 cm −2 ·s −1 can be determined. However, in the presence of a high thermal-neutron fluence rate (for example, >2 × 10 14 cm −2 ·s −1 ) 54 Mn depletion should be investigated. 1.4 Detailed procedures describing the use of other fast-neutron detectors are referenced in Practice E261 . 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Refer to Guide E844 for guidance on the selection, irradiation, and quality control of neutron dosimeters. 5.2 Refer to Practice E261 for a general discussion of the determination of fast-neutron fluence rate with threshold detectors. 5.3 Pure iron in the form of foil or wire is readily available and easily handled. 5.4 Fig. 1 shows a plot of cross section as a function of neutron energy for the fast-neutron reaction 54 Fe(n,p) 54 Mn ( 1 ) . 3 This figure is for illustrative purposes only to indicate the range of response of the 54 Fe(n,p) 54 Mn reaction. Refer to Guide E1018 for recommended tabulated dosimetry cross sections. FIG. 1 54 Fe(n,p) 54 Mn Cross Section 5.5 54 Mn has a half-life of 312.19 (3) days 4 ( 2 ) and emits a gamma ray with an energy of 834.855 (3) keV ( 2 ) . 5.6 Interfering activities generated by neutron activation arising from thermal or fast neutron interactions are 2.57878 (46)-h 56 Mn, 44.494 (12) days 59 Fe, and 5.2711 (8) years 60 Co ( 2 , 3 ) . (Consult the latest version of Ref ( 2 ) for more precise values currently accepted for the half-lives.) Interference from 56 Mn can be eliminated by waiting 48 h before counting. Although chemical separation of 54 Mn from the irradiated iron is the most effective method for eliminating 59 Fe and 60 Co, direct counting of iron for 54 Mn is possible using high-resolution detector systems or unfolding or stripping techniques, especially if the dosimeter was covered with cadmium or boron during irradiation. Altering the isotopic composition of the iron dosimeter is another useful technique for eliminating interference from extraneous activities when direct sample counting is to be employed. 5.7 The vapor pressures of manganese and iron are such that manganese diffusion losses from iron can become significant at temperatures above about 700°C. Therefore, precautions must be taken to avoid the diffusion loss of 54 Mn from iron dosimeters at high temperature. Encapsulating the iron dosimeter in quartz or vanadium will contain the manganese at temperatures up to about 900°C. 5.8 Sections 6 , 7 and 8 that follow were specifically written to describe the method of chemical separation and subsequent counting of the 54 Mn activity. When one elects to count the iron dosimeters directly, those portions of Sections 6 , 7 and 8 that pertain to radiochemical separation should be disregarded. Note 1: The following portions of this test method apply also to direct sample-counting methods: 6.1 – 6.3 , 7.4 , 7.9 , 7.10 , 8.1 – 8.5 , 8.18 , 8.19 , and 9 – 12 .