不同级钚材料的衰变放热功率计算分析

钚材料中放射性核素会不断衰变并释放能量,改变钚材料及周围部件的温度。为研究不同级钚材料在其整装存储及运输过程中衰变放热功率随时间的变化规律,依据不同级钚材料的放射性核素组分,在分析核素级联衰变规律的基础上,并在物理模型中考虑衰变时的能量分支比,计算得到了武器级钚、反应堆级和混合级钚材料中各核素的衰变放热功率和总热功率随时间的演变规律。计算结果表明,1 kg不同级的钚材料,其衰变放热功率最大的是混合级钚,放热最少的是武器级钚;武器级钚材料衰变放热功率主要来自于~(239)Pu,而反应堆级与混合级钚材料的衰变放热功率主要来自于~(241)Pu和~(238)Pu。三种不同级钚材料中,~(242)Pu的衰变放热功率均很小。考虑能量分支比后,可更准确地计算给出钚材料的衰变热功率。     

含铀材料化学爆炸事故后果预测与分析

含铀材料化学爆炸事故会产生放射性气溶胶危害人体健康.探讨了铀气溶胶的形成及危害,针对不同风速、天气因素和地貌状况,应用Hotspot核事故后果评价模型定量计算了有关辐射特征量,结合相关文献记录,对其进行比较和分析.计算结果显示,不同的风速、天气因素和地貌状况都会对应着相应不同的辐射特征量,并具有一定的规律性,对辐射危害防护及处置有着明显的影响.     

钚气溶胶的形成机理

核科学研究、核电站事故与核恐怖袭击释放的钚气溶胶,是一种危害公众与环境安全的毒性材料。掌握钚气溶胶的形成机理,不仅是评估和预防其辐射影响的理论基础,而且是钚气溶胶采样、特性分析等工作的重要前提。本文依据气溶胶粒子三种模态分布理论,总结了钚气溶胶形成过程中的气相成核与凝结凝聚两个控制步骤,综述了氧化、燃烧、高能事件等不同场景下的钚材料气溶胶化的形成机理,包括钚气溶胶形成时的化学过程研究进展,以期对后续的相关研究工作有帮助。     

钚

在多数核电厂产生的能量中,有三分之一以上来自钚。在此,钚是作为副产品产生的。 钚曾经是天然存在的,但除痕量外,在地壳中现在已找不到这种元素。 在我们的生物圈里,有几吨钚,这些钚是20世纪50～60年代大气层武器试验的遗留物。 钚,尤其在吸入体内后会产生放射危害。因此操作时,必须采取适当的防护措施。 将反应堆以及拆卸核武器产生的钚加入核燃料循环,便成为一种宝贵的能源。 钚的同位素主要有: 钚-238(半衰期88年) 钚-239,易裂变(半衰期24000年) 钚-240,易裂变(半衰期6500年) 钚-241,易裂变(半衰期14年) 钚-242(半衰期37600年)…     

某污染区含钚再悬浮气溶胶的粒度特征

实验采集了某污染区的土壤和分级气溶胶样品,分析了其中239Pu的含量,研究了含钚再悬浮气溶胶的粒度特征,并结合土壤风蚀机理对核素再悬浮的过程进行了讨论。研究表明:在未扰动情况下,239Pu的活度中值空气动力学直径均值为3.1μm;在扰动情况下,大颗粒的浓度显著增加,而小颗粒中的239Pu的比例明显下降;239Pu的典型粒度分布样式基本符合文献提出的137Cs的部分粒度分布样式;再悬浮气溶胶中的239Pu的富集因子在0.002~0.2,与粒径的关系不显著。     

燃钚反应堆

【法国《研究》1999年第325期和法国《科学与生活》2000年第988期报道】 80年代放弃的高温核反应堆再次研究用于销毁俄罗斯军用钚以及用于发电和供热。为了销毁裁军协议中规定的50吨钚,美国议会计划在2000年向GT-MHR反应堆(燃汽轮机模块氦反应堆)提供1000万美元。由美国通用原子能公司于1993年倡议的该计划,1996年得到法国FRAMATOME的支持,1997年又得到日本FUJI电力公司的支持。2009年将在俄罗斯的托木斯克建造一座原型堆。这种类型的反应堆只能燃烧钚。 对于该项目,俄罗斯的专家保证,在相等的电功率上,该反应堆的有效性将比其目前…     

P_(301)型天然无机材料处理含钚、镅废水的研究

本文报道了用加工处理后的 P_(301)型天然无机材料处理含钚、镅废水的研究。对国内不同地区的样品进行了筛选,并对料液中钠、钙离子浓度,酸碱度及络合剂浓度等影响因素进行了试验。结果表明,在弱酸性介质中,对钚、镅的分配比(K_d)可达10~3—10~4,而较大量的钠盐和一定量的钙盐存在对分配比的影响较小。用模拟含钚、镅废水(~(239)Pu 比放为5.2×10~(-5)Ci/L,~(241)Am 比放为8.3×10~(-6)Ci/L)通过填装 P_(301)型天然无机材料的柱子,钚和镅的穿透床体积数分别为1100、1500时,其去污因数均大于10~4。     

用于钚污染物处置的钚清除限值

近来全球政策的变化使得美国削减了核武器并中止了钚的生产，但以前在钚的生产、核弹头的拆除、一些设施的去污和退役中已经产生了一些钚污染物，而这些污染物必须进行进一步的管理。在处理每批污染物时，处理者必须面临的问题是该污染物在废弃之前是将钚清除还是不进行清除而直接作废弃处理。美国能源部（ＤＯＥ）目前已制定出了一种称作钚清除限值系统（ＰＲＬＳ）的新方法，可用此方法对上述选择作出决定。该方法的基础是定义了一     

辐照元件中钚及钚同位素含量的核物理测定方法

本工作研究了通过钚的α放射性和同位素组成而确定堆照元件中钚量及其各同位素含量的一般原理及方法。井以一种辐照元件的样品为例进行了具体应用。测定了一块元件中的9个切片的样品,获得了该元件中钚及各同位素含量的数据。实验结果与库仑滴定法测定的总钚量及同位素稀释质谱法测定的各切片相对燃耗值的变化的结果是一致的。本方法目前测定辐照元件中总钚量的不确定度约为±2.0%;对于一般的钚样品不确定度约为±1.5%。     

英国民用钚的生产和去向

【英国《自然》1988年6月23日刊第709页报道】 1985年我们公布了对英国民用钚贮存量的计算结果,我们判断至少有2.3±0.8吨钚(足够400枚弹头所用)未被计入贮存量。现在,通过与官方数据进行比较,进一步证实了我们对民用钚总存量的计算多半是准确的。我们认为前政府对民用钚去向所     

Fuel cycle strategies and plutonium management in Europe

An overview of current nuclear power generation and fuel cycle strategies in Europe is presented, with an emphasis on options for the management of separated plutonium in the medium to long term. Countries which have opted for reprocessing of spent fuel have had to contend with increasing inventories of separated plutonium. Of the various potential options for utilisation or disposition of these stockpiles, only light water reactor (LWR) mixed-oxide (MOX) fuel programmes are sufficiently technologically mature to be fully operational in several European countries at present. Such reprocessing-recycling programmes allow for a stabilisation of the overall separated plutonium stocks, but not for a significant reduction in the stockpile. Moreover, the quality of recycled plutonium decreases at each potential step of re-irradiation. Therefore, optimised or new ways of managing the plutonium stocks in the medium to long term are required. In the present overview we consider the most promising options for reactor utilisation of plutonium in both near-term future reactor and Generation IV systems.     

Dynamics aspects of plutonium burning in an inert matrix

Burnup calculations have been performed on a mini fuel assembly containing 21 fuel rods and four water holes at the corners. The fuel rod positions were filled with 4% enriched UO₂ fuel and with either reactor grade or weapons grade plutonium mixed in an inert matrix. The ratio between the UO₂ and the IMF rods was varied to investigate the influence of the UO₂ fuel on the dynamics of the assembly. From a simple reactor model with one delayed neutron group and first-order fuel and temperature feedback mechanisms, the linear transfer function from reactivity to reactor power was calculated that was subsequently used in a root-locus analysis. From this, it is concluded that only 20% of the fuel rods need to be made of UO₂ to have a fuel that is linearly stable up to 1000 days of irradiation.     

钚作业人群流行病学研究进展

随着核技术的发展,钚逐渐成为核燃料系统中的主要核素,从事钚作业的人员逐年增加。但钚的健康效应尚需要进一步的明确。世界上一些核大国针对钚接触的工作人员的健康效应做了一些流行病学研究。不同设施的钚作业人员的研究结果不尽相同。前苏联Mayak工作人员的钚内照射剂量相对较高,其队列研究具有足够的统计能力;而美国、英国低水平钚辐射暴露的队列研究尚未确认剂量与效应的关系。钚作业人群的流行病学研究的可靠性取决于器官剂量估算的准确性。我国关于钚作业人员的健康效应的研究与世界上其他核大国还有一定的差距。本文就国外核大国关于钚作业人群的流行病学研究进展进行综述,期望为我国开展钚作业人员的远后健康效应研究提供思路。     

Inert matrix and thoria fuels for plutonium elimination

In our previous studies we analysed the plutonium burning performance of various kinds of fuel, based on mixing plutonium oxide with thorium oxide (TOX), or with inert matrix (IMF), or with inert matrix plus a limited addition (doping) of thorium oxide (TD-IMF). The present paper includes the neutronic analysis of a metal-based fuel variant and of fissile material recycling in TOX fuels. If the recycled fuel is topped with weapons grade plutonium (WG-Pu) as fissile material, it is possible to sustain indefinitely a closed cycle.     

Re-evaluation of the phase relationship between plutonium and zirconium dioxides

The phase relationship between ZrO₂ and PuO₂ was examined in a low PuO₂ content region, from 3.1 to 11.2 mol% PuO₂, at temperatures between 1273 K and 1473 K, by high temperature X-ray diffractometry. The measurements were carried out in air. At 1273 K, the samples in this composition range consisted of two phases, monoclinic and cubic. Another phase, tetragonal, was observed at 1373 K. The low temperature monoclinic phase disappeared at 1473 K. It was confirmed that the monoclinic phase disappears around 1463 K; the disappearance temperature does not depend on the composition of the sample. It was, thus, inferred that there should be a eutectoid line in the phase diagram. Though the eutectoid point is not clear, the PuO₂ content at the point should be less than 3.1 mol%.     

Monte Carlo calculations on transmutation of plutonium and minor actinides of pebble bed high temperature reactor

The paper aimed to maximize the fuel burnup performance of plutonium and minor actinides fueled pebble bed high temperature reactor (PBMR-400). The PBMR-400 was designed as a reference core. The neutronic calculations were performed by the code combination MCNP-ORIGEN-MONTEBURNS. In this study, neutronic performances of three different types of nuclear fuels (Reactor Grade Plutonium – RGPu; Weapon Grade Plutonium – WGPu and Minor Actinides – MAs) combined with natural uranium were conducted in a PBMR-400 full core. The neutronic performances were compared with the original uranium fuel designed for this reactor. Neutronic calculations showed that 9.6 wt % enriched uranium has a core effective multiplication factor (k_eff) of 1.2395. Corresponding to this k_eff values the natural UO₂/RG-PuO₂; natural UO₂/WG-PuO₂ and natural UO₂/MAO₂ mixture were found 70%/30%, 76%/24% and 63%/37%, respectively. The operation times were computed as ∼2000, ∼2500 and 1400 days whereas, the corresponding burnup values were obtained as ∼163 000, ∼194 000 and ∼116 000 MWD/T, respectively, for end of life k_eff set equal to 1.08.     

氧化钚属性测量技术研究

利用高分辨高纯锗γ谱仪,在铅屏蔽室内,对100 g回收氧化钚粉末样品和8 g纯氧化钚粉末样品分别进行了长时间测量,在自然环境,对200 g回收氧化钚粉末样品进行了现场探测.在三个样品的能谱中均观察到871 keV特征γ射线,除此之外,没有观察到其它与氧的存在相关的特征射线.同过去所测的金属钚谱相比较,在金属钚谱中未曾发现871 keV特征γ射线.因此,就核查区分封闭容器罐中的钚材料是金属钚还是化合钚而言,可以用871 keV来旁证"金属钚的不存在".对200 g氧化钚样品的现场探测表明,871 keV能峰是明显存在的,而且自编的丰度和年龄分析软件能从10 min测量能谱中识别出871 keV能峰.如果将属性测量系统的分析软件和控制部分进行适当改进,该系统就具备通过监测871 keV能峰确定氧化钚属性的能力.     

Inert matrix fuel for the utilisation of plutonium

Utilising fuel resources responsibly, reducing waste volume and emissions as well as conflict potentials within the international community (non-proliferation, energy demand) are among the principles for the judgment of sustainable development. Utilising and burning plutonium in a light water reactor has been shown to be feasible for the disposition of the large amount of excess plutonium produced in today's power reactors and resulting from the disarmament efforts of the super powers. With regard to material technology aspects, efforts have concentrated on the evaluation of fabrication feasibility and on the determination of the physicochemical properties of a single phase zirconium/erbium/plutonium oxide material stabilised as a cubic solution by yttrium for plutonium and minor actinide incineration and transmutation. Due to the absence of uranium as origin for plutonium build-up, such a nuclear fuel is called Inert Matrix Fuel. Irradiation testing with a dedicated experiment in the material test reactor in Halden, Norway, is underway within the framework of the OECD-Halden Reactor Project.     

Current status of researches on the plutonium rock-like oxide fuel and its burning in light water reactors

Intention of the ROX-LWR system research is to provide an option for utilization or disposition of surplus plutonium. Researches on inert matrix materials and irradiation performance shows that the most favorable candidate for the ROX fuel is a particle dispersed fuel where small particles consisted of yttria stabilized zirconia, PuO₂ and some additives are homogeneously dispersed in spinel matrix. Reactor safety analyses show that the ROX fueled PWR core has nearly the same performability as the existing UO₂ fueled PWR under both reactivity initiated accidents and loss of coolant accidents.