1.1 本试验方法描述了反应堆容器监视中子注量剂量测定中氦积累的概念和用途。尽管该试验方法是针对船舶监视的应用，但其概念和技术同样适用于中子剂量测定的一般领域。该试验方法在反应堆容器监视中的各种应用如下: 1.1.1 氦累积通量监测器（HAFM）胶囊， 1.1.2 用于氦分析的未封装或镉或钆覆盖的辐射监测器（RM）和HAFM导线， 1.1.3 氦气积聚的夏比试块样品，以及 1.1.4 氦气积聚的反应堆容器（RV）壁样品。 1.2 本标准并不旨在解决与其使用相关的所有安全问题（如有）。 本标准的使用者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。 1.3 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 5.1 HAFM试验方法是几种可用的被动中子剂量测定技术之一（例如，参见试验方法 E854 和 E1005 ). 该试验方法可与其他剂量测定方法结合使用，或者，如果不同HAFM传感器材料有足够的数据可用，则可作为替代剂量测定试验方法。 HAFM方法可直接测量辐照样品中的总氦生成量。然后，可以根据这一点推断出绝对中子注量，假设有适当的光谱积分总氦产生横截面。或者，HAFM方法的复合中子探测效率的校准可以通过暴露在基准中子场中获得，其中通量和光谱平均横截面都是已知的（见指南 E2005 ). 5.2 HAFM的优点是产生稳定的最终产物氦，这使得HAFM方法对于短期和长期通量测量都非常有吸引力，而不需要对衰变进行时间相关的校正。因此，HAFM是理想的被动、时间- 积分通量监测器。此外，子产品氦气的燃尽可以忽略不计。 5.2.1 许多HAFM材料可以以未封装线束段的形式进行辐照（参见 1.1.2 ). 这些节段可以很容易地通过从标准库存材料批次进行切割来制造。优点是封装及其相关成本是不必要的。在某些情况下，未封装的导线，如Fe、Ni、Al/Co和Cu，已包含在标准辐射（RM）剂量测定装置中( 表1 )，可用于辐射剂量测定和氦累积剂量测定。在辐射计数之后，样品随后被蒸发用于氦测量。 A. 评价的 235 U裂变中子谱- 90%反应发生的平均氦气产生横截面和能量范围，即5%至95%的响应极限。大多数横截面是通过使用ENDF/B-VIII.0库进行同位素评估获得的 ( 7. ) .NJOY-2016代码 ( 8. ) 用于根据ENDF/B-VIII.0核数据生成天然气生产横截面。这个 235 U裂变谱来自最新推荐的IRDFF-II库 ( 9 ) 使用MANIPULATE-2010代码将频谱和响应函数折叠在一起。横截面用于剂量计材料内的指示同位素。热中子横截面表示在0.0253eV的入射中子能量下的氦产生横截面。 B 通常包括在剂量测定装置中，作为辐射监测器，或者作为纯元素箔或金属丝，或者在铝的情况下，作为其他元素的减轻材料。 C 一些 4. He气体生产文件例如直接来自IRDFF-II库， 6, 7 李和 10, 11 B.这些IRDFF-II评估包括天然气产量计算中的以下反应通道: 6. Li[MT207=MT24+MT32+MT105]； 10 B[MT207=MT22+2*MT35+2*MT106+MT107+2*MT155]； 7. Li[MT207=MT24+MT25+MT33+2*MT102]； 11 B[MT207=2*MT11+MT22+MT24+2*MT33+3*MT107+MT117]。 D 所显示的位数并不表示重要性；它们只是为了提供对源核数据评估的可追溯性。 E 该材料用作封装，而非HAFM剂量计。 看见 11.1.3 和 14.2.5 . 5.3 HAFM方法是对RM和固态轨道记录器（SSTR）箔片的补充，并已被用作多箔片方法的一个组成部分。HAFM方法遵循与RM箔技术基本相同的原理，RM箔技术已成功用于精确的中子剂量测定。存在具有彼此显著不同的中子能量灵敏度的各种HAFM传感器材料。HAFM包含 10 B和 6. Li已与RM箔一起常规用于液态金属快中子增殖反应堆（LMFBR）应用 ( 10 ) 所得数据与辐射箔中子剂量测定的现有调整方法完全兼容（参考指南 E944 ). 5.4 HAFM方法的一个应用是直接分析压力容器壁面擦伤或夏比试块监测样品。测量这些材料中的氦产量可以提供 原位 中子注量谱的积分信息。该应用可以在传统剂量计放置困难（如果不是不可能的话）的关键位置提供剂量测定信息。必须首先进行分析，以确定硼、锂和其他成分的浓度及其均匀性，从而确定它们对总氦产量的可能贡献。硼（和锂）可以通过在已知的热中子暴露下将一部分硼转化为氦来测定。 在暴露前后对材料中氦气的测量将能够确定硼含量 ( 11 ) 以这种方式可以获得低至小于1wtppm的硼水平。 5.5 通过仔细选择合适的HAFM传感器材料及其质量，氦气浓度范围从 ∼ 10 −14 至10 −1 可以生成并测量原子分数。就通量而言，这表示大约10 12 至10 27 n/cm 2. 在常规监测测试过程中可能遇到的通量（>1 MeV）值预计范围为 ∼ 3 × 10 14 至2×10 20 n/cm 2. ，这完全在HAFM技术的范围内。 5.6 HAFM的分析需要对氦含量进行绝对测定。 本试验方法中规定的分析系统包括一个专门的质谱仪和一个精确校准的氦加标系统。氦的测定是通过同位素稀释和随后的同位素比率测量进行的。氦是稳定的，这一事实使监测器具有永久性，氦分析能够在以后的时间进行，通常不会因感应放射性而带来不便。存在这样的分析系统，如果需要，可以复制额外的分析设施。因此，在这方面，分析要求与其他ASTM测试方法类似。

1.1 This test method describes the concept and use of helium accumulation for neutron fluence dosimetry for reactor vessel surveillance. Although this test method is directed toward applications in vessel surveillance, the concepts and techniques are equally applicable to the general field of neutron dosimetry. The various applications of this test method for reactor vessel surveillance are as follows: 1.1.1 Helium accumulation fluence monitor (HAFM) capsules, 1.1.2 Unencapsulated, or cadmium or gadolinium covered, radiometric monitors (RM) and HAFM wires for helium analysis, 1.1.3 Charpy test block samples for helium accumulation, and 1.1.4 Reactor vessel (RV) wall samples for helium accumulation. 1.2 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. 1.3 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 The HAFM test method is one of several available passive neutron dosimetry techniques (see, for example, Test Methods E854 and E1005 ). This test method can be used in combination with other dosimetry methods, or, if sufficient data are available from different HAFM sensor materials, as an alternative dosimetry test method. The HAFM method yields a direct measurement of total helium production in an irradiated sample. Absolute neutron fluence can then be inferred from this, assuming the appropriate spectrum integrated total helium production cross section. Alternatively, a calibration of the composite neutron detection efficiency for the HAFM method may be obtained by exposure in a benchmark neutron field where the fluence and spectrum averaged cross section are both known (see Guide E2005 ). 5.2 HAFMs have the advantage of producing an end product, helium, which is stable, making the HAFM method very attractive for both short-term and long-term fluence measurements without requiring time-dependent corrections for decay. HAFMs are therefore ideal passive, time-integrating fluence monitors. Additionally, the burnout of the daughter product, helium, is negligible. 5.2.1 Many of the HAFM materials can be irradiated in the form of unencapsulated wire segments (see 1.1.2 ). These segments can easily be fabricated by cutting from a standard inventoried material lot. The advantage is that encapsulation, with its associated costs, is not necessary. In several cases, unencapsulated wires such as Fe, Ni, Al/Co, and Cu, which are already included in the standard radiometric (RM) dosimetry sets ( Table 1 ), can be used for both radiometric and helium accumulation dosimetry. After radiometric counting, the samples are later vaporized for helium measurement. (A) Evaluated 235 U fission neutron spectrum-averaged helium production cross section and energy range in which 90 % of the reactions occur, that is, the 5 % to 95 % response limits. Most cross sections are obtained from isotopic evaluations using the ENDF/B-VIII.0 library ( 7 ) . The NJOY-2016 code ( 8 ) was used to generate the gas production cross sections from the ENDF/B-VIII.0 nuclear data. The 235 U fission spectrum came from the latest recommended IRDFF-II library ( 9 ) . The spectrum and response function were folded together using the MANIPULATE-2010 code. Cross sections are for the indicated isotope within the dosimeter material. The thermal neutron cross section represents the helium production cross section at an incident neutron energy of 0.0253 eV. (B) Often included in dosimetry sets as a radiometric monitor, either as a pure element foil or wire or, in the case of aluminum, as an allaying material for other elements. (C) Some of the 4 He gas production files come directly from the IRDFF-II library, for example, 6,7 Li and 10,11 B. These IRDFF-II evaluations include the following reaction channels in the gas production calculation: 6 Li [MT207=MT24+MT32+MT105]; 10 B [MT207=MT22+2*MT35+2*MT106+MT107+2*MT155]; 7 Li [MT207=MT24+MT25+MT33+2*MT102]; 11 B [MT207=2*MT11+MT22+MT24+2*MT33+3*MT107+MT117]. (D) The number of digits shown do not indicate significance; they are only included to provide traceability to the source nuclear data evaluation. (E) This material is used as an encapsulate and not as a HAFM dosimeter. See 11.1.3 and 14.2.5 . 5.3 The HAFM method is complementary to RM and solid state track recorder (SSTR) foils, and has been used as an integral part of the multiple foil method. The HAFM method follows essentially the same principle as the RM foil technique, which has been used successfully for accurate neutron dosimetry. Various HAFM sensor materials exist which have significantly different neutron energy sensitivities from each other. HAFMs containing 10 B and 6 Li have been used routinely in Liquid Metal Fast Breeder Reactor (LMFBR) applications in conjunction with RM foils ( 10 ) . The resulting data are entirely compatible with existing adjustment methods for radiometric foil neutron dosimetry (refer to Guide E944 ). 5.4 An application for the HAFM method lies in the direct analysis of pressure vessel wall scrapings or Charpy block surveillance samples. Measurements of the helium production in these materials can provide in situ integral information on the neutron fluence spectrum. This application can provide dosimetry information at critical positions where conventional dosimeter placement is difficult if not impossible. Analyses must first be conducted to determine the boron, lithium, and other component concentrations, and their homogeneities, so that their possible contributions to the total helium production can be determined. Boron (and lithium) can be determined by converting a fraction of the boron to helium with a known thermal neutron exposure. Measurements of the helium in the material before and after the exposure will enable a determination of the boron content ( 11 ) . Boron level down to less than 1 wt. ppm can be obtained in this manner. 5.5 By careful selection of the appropriate HAFM sensor material and its mass, helium concentrations ranging from ∼ 10 −14 to 10 −1 atom fraction can be generated and measured. In terms of fluence, this represents a range of roughly 10 12 to 10 27 n/cm 2 . Fluence (>1 MeV) values that may be encountered during routine surveillance testing are expected to range from ∼ 3 × 10 14 to 2 × 10 20 n/cm 2 , which is well within the range of the HAFM technique. 5.6 The analysis of HAFMs requires an absolute determination of the helium content. The analysis system specified in this test method incorporates a specialized mass spectrometer in conjunction with an accurately calibrated helium spiking system. Helium determination is by isotope dilution with subsequent isotope ratio measurement. The fact that the helium is stable makes the monitors permanent with the helium analysis able to be conducted at a later time, often without the inconvenience in handling caused by induced radioactivity. Such systems for analysis exist, and additional analysis facilities could be reproduced, should that be required. In this respect, therefore, the analytical requirements are similar to other ASTM test methods.