钚及其裂变产物钯 、银 、镉 、锡 、锑 、锆的系统分离方法

描述了钚及其6种裂变产物钯、银、镉、锡、锑、锆的系统分离方法：在强碱性阴离子交换树脂柱上将盐酸介质的辐照靶溶解液中的这些元素分为5组，然后再针对各组目标元素进行分离和纯化，可简便快速地从同一份靶溶解液中分离以上7种元素。采用辐照铀靶对分离方法进行了验证，结果表明，分离流程对6种裂变产物的化学回收率均大于70%，对γ谱仪测量干扰的主要核素去污因子均大于1.0×10³，可满足²³⁹Pu裂变谷区核素裂变产额测量对化学分离的要求。     

基于衰变链计算的裂变产物缓发γ能谱分析

在军控核查技术中，缓发γ能谱是核材料的“指纹”。为计算和分析铀裂变产物的缓发γ能谱，本文将各种类型的衰变链简化为基态线性链和激发态线性链，推导了零时前后各级核素数目的变化公式，建构了计算缓发γ射线能谱的C语言程序代码，并通过实验对理论推导进行了验证。通过分析几种核素的缓发γ射线计数发现，计算结果与实验数据吻合较好。     

Ab initio calculations of the NO2 fission for CL-20 conformers

NO₂ fission is regarded to be the most important initial decomposition process of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20). In this study, four CL-20 conformers based on the ε-CL-20 were obtained after the optimization at m062x/cc-pvtz level, and the bond length, bond order and bond dissociation energy of the N-N bonds were examined to investigate the stability of these bonds. In addition, the rate constants and activation energy of the NO₂ fission were evaluated using the microcanonical variational transition state theory (μVT). The calculation results have shown that N-N bonds in the case of pseudo-equatorial and axial of nitro groups are the most stable and the least stable, respectively, by evaluating the bond length, bond order and minimum energy path (MEP). The NO₂ fission rate constants are affected by not only the stability of N-N bonds but also the repulsion forces from the other nitro groups, and the fission process for pseudo-equatorial positioning of nitro groups is easier to be accelerated due to the increase of the repulsion forces. The decomposition of CL-20 conformer may mainly originate from the fission of the pseudo-equatorial positioning of nitro groups, especially for CL-20 III conformer because of the significant low activation energy.     

Tuneable Singlet Exciton Fission and Triplet–Triplet Annihilation in an Orthogonal Pentacene Dimer

Fast and highly efficient intramolecular singlet exciton fission in a pentacene dimer, consisting of two covalently attached, nearly orthogonal pentacene units is reported. Fission to triplet excitons from this ground state geometry occurs within 1 ps in isolated molecules in solution and dispersed solid matrices. The process exhibits a sensitivity to environmental polarity and competes with geometric relaxation in the singlet state, while subsequent triplet decay is strongly dependent on conformational freedom. The near orthogonal arrangement of the pentacene units is unlike any structure currently proposed for efficient singlet exciton fission and may lead to new molecular design rules.     

Chemical reaction kinetics dataset of Cs-I-B-Mo-O-H system for evaluation of fission product chemistry under LWR severe accident conditions

In order to improve LWR source term under severe accident conditions, the first version of a fission product chemistry database named ‘ECUME’ was developed. The ECUME is intended to include several datasets of major chemical reactions and their effective kinetic constants for representative severe accident sequences. It is expected that the ECUME can serve as a fundamental basis from which fission product chemical models can be elaborated for use in the severe accident analysis codes. The implemented chemical reactions in the first version were those for representative gas species in Cs-I-B-Mo-O-H system from 300 to 3000 K. The chemical reaction kinetic constants were evaluated from either literature data or calculated values using ab-initio calculations. The sample chemical reaction calculation using the presently constructed dataset showed meaningful kinetics effects at 1000 K. Comparison of the chemical equilibrium compositions by using the dataset with those by chemical equilibrium calculations has shown rather good consistency for the representative Cs-I-B-Mo-O-H species. From these results, it was concluded that the present dataset should be useful to evaluate fission product chemistry in Cs-I-B-Mo-O-H system under LWR severe accident conditions, where kinetics effects should be considered.     

P204树脂和阳离子交换树脂分离Sc与裂变产物

P204对Sc有很好的分离选择性和分离能力，但由于反萃困难限制了其在Sc纯化中的应用。本工作研究了从裂变产物中分离纯化Sc的方法，建立流程如下：首先利用P204树脂对Sc的强萃取能力，将Sc与大量裂变产物分离，再通过灰化方法破坏树脂官能团，解决了吸附在P204树脂上的Sc难以解吸的问题，最后通过阳离子交换树脂实现Sc与残留Zr和Mo的分离，从而实现了Sc与裂变产物的分离。该方法对样品体积和酸度要求低，流程步骤操作简单。通过对模拟样品进行分析，Sc的回收率大于65%，对主要裂变产物的去污因子大于10³，适用于Sc与裂变产物的分离。     

UMo/Zr单片式燃料板起泡行为数值模拟

燃料板的鼓泡临界温度是制定研究试验堆安全系数的标准之一，通常由鼓泡退火实验确定。针对鼓泡退火实验，本研究发展了一种对UMo/Zr单片式燃料板宏观起泡行为进行计算模拟的方法，并计算分析了气腔内裂变气体原子数对鼓泡高度的影响，获得了包壳内的Mises应力和等效塑性应变随温度升高而演化的规律。研究发现，气腔周围包壳产生塑性变形是起泡的一个关键原因。此研究为燃料板起泡机理和关键影响因素分析打下了基础。     

240Pu自发裂变气体产物产额的唯像模型研究

基于裂变多模式无规颈断裂物理思想，建立了中子诱发²³⁹Pu裂变、²⁴⁰Pu自发裂变系统裂变产额计算的唯像模型。以实验数据为基础，利用最小二乘法确定了唯像模型参数。基于唯像模型计算的产额，结合实验数据系统规律进行分析和再评价，给出²⁴⁰Pu自发裂变气体产物^87,88Kr和^133,135Xe的累积产额推荐值。     

Spatial distribution of thorium fission rate in a fast spallation and fission neutron field: An experimental and Monte Carlo study

The Energy plus Transmutation (EpT) set-up of the Joint Institute for Nuclear Research (JINR), Dubna, Russia is composed of a lead spallation target surrounded by a blanket of natural uranium. The resultant neutron spectrum is a combination of spallation and fission spectra, modified by a reflective external layer of polyethylene and an internal absorbing layer of cadmium. The EpT set-up was irradiated with a beam of 4 GeV deuterons from the Nuclotron Accelerator at JINR. The spatial distribution of thorium fission rate within the assembly was determined experimentally, using a fission track detector technique, and compared with Monte Carlo predictions of the MCNPX code. Contributions of neutrons, protons, deuterons, photons and pions to total fission were taken into account. Close agreement between the experimental and calculated results was found.     

Neutron energy dependence of delayed neutron yields and its assessments

Incident neutron energy dependence of delayed neutron yields of uranium and plutonium isotopes is investigated. A summation calculation of decay and fission yield data is employed, and the energy dependence of the latter part is considered in a phenomenological way. Our calculation systematically reproduces the energy dependence of delayed neutron yields by introducing an energy dependence of the most probable charge and the odd–even e?ect. The calculated fission yields are assessed by comparison with JENDL/FPY-2011, delayed neutron activities, and decay heats. Although the fission yields in this work are optimized to delayed neutron yields, the calculated decay heats are in good agreement with the experimental data. Comparison of the fission yields calculated in this work and JENDL/FPY-2011 gave an important insight for the evaluation of the next Japanese evaluated nuclear data library (JENDL) .