N(~(231)Pa)/N(~(235)U)γ谱法测定高浓铀年龄研究

测定高浓铀(HEU)的年龄在军控中具有重要意义,它可以获得HEU活动的相关信息。通过测量HEU中235U发出的多条γ射线,进行相对效率刻度曲线的拟合,并将曲线延长至邻近的231Pa发出的γ射线能量点,从而得到231Pa/235U的比,即可求出HEU的年龄。分别利用231Pa发出的302.65 keV与330.06 keVγ射线对大质量的高浓铀样品年龄进行测定,其结果与参考值的偏差分别为-11%和+86%。     

电感耦合等离子体质谱测定铀样品年龄方法研究

铀样品年龄与生产时间密切相关,是核法证学调查核材料来源属性的一个重要参数。本文研究建立了利用~(230)Th/~(234)U原子数比测定铀样品年龄的分析方法。分别用~(229)Th和~(233)U稀释剂进行铀样品同位素稀释,利用TEVA树脂对样品中的铀和钍进行分离处理,用多接收电感耦合等离子体质谱测量~(229)Th/~(230)Th和~(233)U/~(234)U原子数比,根据铀年龄计算公式通过~(230)Th/~(234)U原子数比可得到样品的铀年龄。采用该方法对CRM U850和U010标准样品进行了年龄测定,结果与美国劳伦斯·利弗莫尔国家实验室的测量结果一致,但较实际年龄偏大,可能是由于生产时纯化过程不完全,导致有残留的~(230)Th在样品中。本文所建立的方法可用于铀样品~(230)Th-~(234)U模型年龄的测定,为核法证学调查提供重要信息。     

从~(237)Np中分离高纯度的~(233)Pa的新方法

一、引言~(231)Pa是AcU(~(235)U)天然放射系的一个重要成员。在海洋地球化学和地质年代学研究中,它是一个非常重要的核素。但可作为~(231)Pa分离用的产额示踪剂的核素只有~(233)Pa,它是β-γ发射体,半衰期短(27.0 d)。因此如果能够简便地制得示踪剂~(233)Pa,对~(231)Pa年代学的研究和应用以及对镤化学和放射化学的研究无疑是个促进。     

高浓铀年龄的测定

基于高浓铀中^235U的衰变子体^231Pa的数量随时间而增加,且在一定时间内与高浓铀年龄有很好的线性关系这一原理,用溶剂萃取法从高浓铀中分离出^231Pa,回收率达到67．1％以上;用高纯Geγ谱仪测量^235U,用α谱仪测量^231Pa,并分别计算出^235U和^231Pa的含量,由此推算出高浓铀的年龄,其结果的不确定度为8％。     

一种用~(235)U作单内标的同位素稀释质谱法

建立了一种用~(233)U作单内标的同位素稀释质谱法。它可准确测定铀样品中的丰度比,这是一种基于重量法的绝对测量方法。~(233)U和被测铀样品按不同重量比被混合,然后,同时测量混合样中R_(58)(~(235)U/~(238)U)和R_(38)(~(233)U/~(238)U),而R_(38)可被看作是内参照标准。藉助迭代运算,R_(58)逐步逼近它的真值。使用该法,R_(58)的测量总不确定度可达到0.15%。并且,这个方法具有显著的优点,例如:测量的外精度可好于0.02％。     

用中子活化分析法测定~(238)U/~(235)U同位素丰度比

本文论述了用中子活化分析法测定含微量铀的样品中~(238)U/~(235)U同位素丰度比的原理及方法。样品在反应堆中接受短时间照射后,用Ge(Li)探头或高纯锗探头-多道能谱分析仪-计算机系统测量射线的能谱.可以分辨出~(238)U和~(235)U的许多监测峰。利用这两种监测峰计数之比与这两种同位素丰度比成正比的关系,分析铀的同位素丰度比,在~(235)U丰度为0.6％-18％范围时精密度为1％-2％,在贫化铀和18％-60％丰度~(235)U时,精密度为2％-3％。     

固体核径迹探测器在核物理中的应用

1.中子物理方面 用于测量快中子、堆中子注量率和高能中子谱,如根据~(12)C(n,n′)3α测量快中子能谱;定量地测量堆中子注量(其测量范围为 10~(14)～10~(21)n/cm~2);使用CR-39测量14.7MeV中子引起~(51)V(n,p)和~(51)V(n,a)反应截面。为了给快中子堆设计提供核数据,在13.5-14.8Mev中子能量范围内,已经测量~(233)U/~(235)U、~(233)U/~(237)Np、~(235)U/~(237)Np、~(235)U/ 237/Np和~(239)Pu/~(235)U的裂变截面比以及~(237)Pu、~(238)Pu、~(242)Pu、~(244)Pu和~(241)Am的裂变截面。     

THE EVALUATIONS AND THEORETICAL CALCULATIONS OF ~(235)U(p,n)~(235)Np,~(235)U(p,2n)~(234)Np AND ~(235)U(d,2n)~(235)Np REACTION CROSS SECTIONS

The excitation functions of ~(235)U(p,n)~(235)Np,~(235)U(p,2n)~(234)Np and~(235)U(d,2n)~(235)Np reactions were calculated and evaluated respectively. Up to now,the experimental data for ~(235)U(p,n)and(p,2n)reactions in theenergy region from threshold to 25 MeV have not been found;Argonne Na-tional Lab.(ANL)and Lawrence Radiation Lab.at Berkeley(BRK)havemeasured the excitation function of~(235)U(d,2n)~(235)Np reaction respectively;buttheir data appear in great difference. New experimental data have to wait for being measured for unpredictabletime delays.In order to meet the practical requirements,the theoretical calcula-tion and experimental evaluation are carried out.     

~(233)U,~(235)U和~(239)Pu在热中子能区裂变截面的测量

热中子能区~(233)U,~(235)U和~(239)Pu的裂变截面常被用作参考标准,其中~(235)U和~(239)Pu的裂变截面在中子能量E_n～0.25电子伏以上有共振现象出现,而~(233)U的裂变截面曾被认为其1/v特性维持的能区较宽,可达1电子伏以上。但近年来发现~(233)U的裂变截面在0.1电子     

~(233)U,~(235)U热中子裂变截面比值测量

在中子晶体谱仪上利用背靠背裂变室测量中子能量为0.0253电子伏时的~(233)U,~(235)U裂变截面比值,得到的结果是σ_f(~(233)U)/σ_f(~(235)U)=0.916±0.018;同时根据已知的~(235)U热中子裂变截面值推算出~(233)的热中子裂变截面。σ_f(~(233)U)=536±11靶。所得结果与国外结果进行了比较。     

电感耦合等离子体质谱测定铀样品年龄方法研究

铀样品年龄与生产时间密切相关，是核法证学调查核材料来源属性的一个重要参数。本文研究建立了利用²³⁰Th/²³⁴U原子数比测定铀样品年龄的分析方法。分别用²²⁹Th和²³³U稀释剂进行铀样品同位素稀释，利用TEVA树脂对样品中的铀和钍进行分离处理，用多接收电感耦合等离子体质谱测量²²⁹Th/²³⁰Th和²³³U/²³⁴U原子数比，根据铀年龄计算公式通过²³⁰Th/²³⁴U原子数比可得到样品的铀年龄。采用该方法对CRM U850和U010标准样品进行了年龄测定，结果与美国劳伦斯·利弗莫尔国家实验室的测量结果一致，但较实际年龄偏大，可能是由于生产时纯化过程不完全，导致有残留的²³⁰Th在样品中。本文所建立的方法可用于铀样品²³⁰Th-²³⁴U模型年龄的测定，为核法证学调查提供重要信息。     

The jackknife as an approach for uncertainty assessment in gamma spectrometric measurements of uranium isotope ratios

The jackknife as an approach for uncertainty estimation in gamma spectrometric uranium isotope ratio measurements was evaluated. Five different materials ranging from depleted uranium (DU) to high enriched uranium (HEU) were measured using gamma spectrometry. High resolution inductively coupled plasma mass spectrometry (ICP-SFMS) was used as a reference method for comparing the results obtained with the gamma spectrometric method. The relative combined uncertainty in the gamma spectrometric measurements of the ²³⁸U/²³⁵U isotope ratio using the jackknife was about 10-20% (k = 2), which proved to be fit-for-purpose in order to distinguish between different uranium categories. Moreover, the enrichment of ²³⁵U in HEU could be measured with an uncertainty of 1-2%.     

Fission-product yields from neutron-induced fission

Exsting experimental thermal, fast, and 14-MeV neutron-induced fission-product cumulative and independent yieds have been compiled, corrected to common reference values, and listed in tabular form for the following fissile nuclides:Thermal-neutron fission: cumulative yields for ²²⁷Th, ²²⁹Th, ²³³U, ²³⁵U, ²³⁹Pu, ²⁴¹Pu, ²⁴¹Am, ²⁴²Am, ²⁴⁵Cm, ²⁴⁹Cf, ²⁵¹Cf, ²⁵⁴Es, and ²⁵⁵Fm; independent yieds for ²³³U, ²³⁵U, ²³⁷Np, ²³⁸U, and ²³⁹Pu.Fast-neutron fission: cumulativ yields for ²²⁷Ac, ²³¹Pa, ²³²Th, ²³³U, ²³⁵U, ²³⁷Np, ²³⁸U, and ²³⁹Pu; independent yields for ²³⁵U and ²³⁸U.14-MeV-neutron fission: cumulative yields for ²³¹Pa, ²³²Th, ²³³U, ²³⁵U, ²³⁷Np, ²³⁸U, and ²³⁹Pu; independent yields for ²³²Th, ²³³U, ²³⁵U, ²³⁸U, and ²³⁹Pu.11-MeV-neutron fission: cumulative yields for ²³²Th.3-MeV-neutron fission: cumulative yields for ²³¹Pa, ²³²Th, and ²³⁸U.1.1-MeV-neutron fission: cumulative yields for ²³⁷Np.From these experimental values the unknown independent yields are deduced empirically for thermal-neutron fission of ²³³U, ²³⁵U, ²³⁹Pu, and ²⁴¹Pu; the fast fission of ²³²Th, ²³³U, ²³⁵U, ²³⁸U, ²³⁹Pu, ²⁴⁰Pu, and ²⁴¹Pu (the chain yields for ²⁴⁰Pu and ²⁴¹Pu used at this energy being predictions); and the 14-MeV-neutron fission of ²³²Th, ²³³U, ²³⁵U, and ²³⁸U.Finally, by the fitting of the preceding information to condition equations derived from the conservation laws, adjusted sets of chain and independent yields are calculated for thermal fission of ²³³U, ²³⁵U, ²³⁹Pu, and ²⁴¹Pu; fast fission of ²³²Th, ²³³U, ²³⁵U, ²³⁸U, ²³⁹Pu, and ²⁴¹Pu; and 14-MeV fission of ²³²Th, ²³³U, ²³⁵U, and ²³⁸U. The literature search is probably complete to the end of 1975; some 1976 results are included.This paper replaces and makes obsolete the following UKAEA reports: AERE-R7209, AERE-R7394, AERE-R7680, and AERE-R8152.     

锕系可燃毒物板状燃料组件燃耗特性研究

为研究锕系可燃毒物在板状燃料组件的燃耗特性和延长寿期的适用性，本研究以不同富集度的板状燃料为对象，计算分析了相同初始组件无限增殖因数（kinf）情况下的锕系可燃毒物装载量、燃耗深度、235U利用率等。结果表明，在低富集度（4%~7%）情况下，240Pu可燃毒物在寿期内表现出较好的转换效应，235U利用率高，可起到延长堆芯寿期的作用；在中等富集度（25%~40%）情况下，240Pu可燃毒物的转换效应减弱，而231Pa可燃毒物表现出较好的转换效应；在高富集度（70%~97%）情况下， 231Pa可燃毒物的转换效应减弱，但含231Pa组件的235U利用率和达到的燃耗深度在所选锕系核素中最大；240Pu可作为长寿期低富集度燃料可燃毒物的选择，231Pa可作为长寿期中等、高富集度燃料可燃毒物的选择。      

NMIS plus gamma spectroscopy for attributes of HEU,PU and HE detection

A combined nuclear materials identification system–gamma ray spectrometry system can be used passively to obtain the following attributes of Pu: presence, fissile mass, 240/239 ratio and metal versus oxide. This system can also be used with a small, portable, DT neutron generator to measure the attributes of highly enriched uranium (HEU): presence, fissile mass, enrichment, metal versus oxide; and detect the presence of high explosives (HE). For the passive system, time-dependent coincidence distributions can be used for the presence, fissile mass, metal versus oxide for Pu, 240/239 ratio, and gamma ray spectrometry can also be used for 240/239 ratio and presence, allowing presence and 240/239 ratio to be confirmed by two methods. For the active system with a DT neutron generator, all relevant attributes for both Pu and HEU can be determined from various features of the time-dependent coincidence distribution measurements. Active gamma ray spectrometry would determine the presence of HE. The various features of time-dependent coincidence distributions and gamma ray spectrometry that determine these attributes are discussed with some examples from previous determinations.     

237Np与233Pa的分离和测定

采用多孔高硅氧玻璃作吸附柱 ,研究了在 8mol/LHNO3介质中2 37Np与子体2 33Pa的分离和测定。研究结果表明 ,用H2 SO4 解吸2 33Pa ,能使2 37Np与2 33Pa定量分离。2 37Np和2 33Pa的放化回收率分别为 99%～ 10 1%和 99%～ 10 3% ,方法的相对标准偏差分别为 2 %和 3%     

砂岩铀矿地质样品中铀含量仲裁分析方法——同位素稀释电感耦合等离子体质谱法

本工作研究铀矿地质样品中铀含量仲裁分析方法——同位素稀释电感耦合等离子体质谱法。样品经混酸密闭消解溶矿,采用浓缩铀为稀释剂,使用高分辨电感耦合等离子体质谱测定铀同位素比值,进而计算样品中的铀含量。本方法具有明晰的计量溯源特性,铀的测量范围为1～10000μg/g,对于铀含量约为4μg/g的砂岩样品,相对扩展不确定度小于4.0%（扩展因子K=2.57）,可满足砂岩铀矿地质样品中铀含量仲裁分析要求。     

Basic characterization of U: Determination of age and U content using sector field ICP-MS, gamma spectrometry and alpha spectrometry

The possibility to determine the age, i.e. the time since the last chemical separation, of ²³³U was studied using two fundamentally different measurement techniques: inductively coupled plasma mass spectrometry (ICP-MS) and gamma spectrometry. Moreover, the isotope ratio ²³²U/²³³U was measured using both alpha spectrometry and gamma spectrometry. For the two materials analysed, all measurement results were in agreement, i.e. consistent within the combined uncertainties. One of the materials was also measured using gamma spectrometry under field conditions. This measurement was also in agreement with the other results on this material.     

基于NPL-NMC系统的γ测量子系统的建模与优化

在军控核查中,核部件的质量、丰度、年龄属性需采用无损方法进行核查,NPL-NMC系统是一套利用中子多重性测量核部件质量属性的装置,为建立完善的属性测量系统,还需在NPL-NMC系统的基础上建立γ测量子系统。本文通过设计γ测量子系统在NPL-NMC系统上的布局及对中子屏蔽的优化,使系统能对铀部件的丰度、年龄属性进行测量。模拟计算结果表明,该γ测量子系统能很好地满足军控核查对铀部件丰度、年龄属性测量的要求。     

加速器质谱法测量含铀微粒中铀同位素比的方法研究

准确测定含铀微粒同位素比在核保障中有重要的应用价值。本文采用将含铀微粒溶解并加入高纯Fe粉烘干的方法制样,采用中国原子能科学研究院的HI-13串列加速器质谱测量靶样中的同位素比。通过对CRM铀系列同位素标准样品的分析表明,该方法可测定高于10^-5的²³⁶U/²³⁸U同位素比;对于²³⁵U/²³⁸U同位素比在10^-4～10^-1范围内的含铀微粒,²³⁵U/²³⁸U同位素比相对扩展不确定度均小于10%。