草酸体系中镎、钚的阴离子交换分离

用阴离子交换法研究了TRPO流程中镎和钚的浓缩和分离。在适宜条件下,Np、Pu以草酸络阴离子被阴离子交换树脂吸附。用稀硝酸将镎、钚同时洗脱后,调节洗脱液为8mol/LHNO3,使镎和钚转成硝酸络阴离子,再用一阴离子交换柱吸附镎和钚后,用氨基磺酸亚铁-硝酸溶液还原解吸钚,最后用稀硝酸洗脱镎。在实验基础上,建立了镎、钚的离子交换分离流程。本流程的镎、钚浓缩倍数为840,它们的浓度达到约20g/L,镎和钚的分离系数βPu/Np＞100;βNp/Pu＞300;Np和Pu的回收率分别为97.6％和97.4％。     

离子交换法在核燃料方面的应用

目前离子交换法广泛应用于回收铀矿浸出液中的铀,可与溶剂萃取法相媲美。离子交换法对分离和纯化小量原子序数比较高的锕系元素,例如镅、锔、锫、锎、锿和镄也是一种很好的方法。然而这种方法对初级分离高辐射核燃料中的铀、钚和镎却不如溶剂萃取法。     

萃取色层法测定水样中的镎-237

一、前言钚-238作为核电池广泛运用于宇航及其他领域中,而采用中子法生产钚-238时,则他用镎-237作为靶材材。镎-237系亲骨性剧毒核素,在核工业后处理厂及核爆后均有可能排放至环境中,污染周围环境。因此定时监测水样及其他环境样品对于监督安全生产是十分有意义的。测定低水平的镎-237常用的方法有离子交换法,萃取法,萃取色层法。萃取色层法有回收率高,去污好省试剂等优点。我们用廉价的硅藻土作支持体,     

镎的恒流库仑法测定

本文提供了一个测定镎的方法。在1.5N硫酸溶液中,用氧化银(Ⅱ)将镎氧化至镎(Ⅵ),再于8N硫酸-0.06N硫酸铁(Ⅲ)介质中,以电解产生的铁(Ⅱ)滴定镎(Ⅵ)至镎(Ⅳ),用双铂电极安培法确定终点。研究了镎的氧化和测定的适宜条件。测定1～3毫克镎时,相对标准偏差均在0.2%以内。本法与安培法进行了方法核对,并与电位法测定二氧化镎中镎的含量进行了核对。     

Purex过程镎分离和纯化的研究

本文报道了用串级萃取方法研究普勒克斯过程铀线镎的走向的控制,并推荐了从铀线2DW中定量回收、分离、纯化镎的合适工艺条件。讨论了影响因素。按所推荐工艺条件,2D槽2DW中镎回收率达97.3—99.9％,铀损失小于160毫克/升。3D镎萃取槽中,镎回收率可以达到约99—99.6％。镎中钚分离系数达(1.4～3.5)×10~3。2N镎反萃槽中,镎回收率可达99.3—99.5％,镎中去铀分离系数为2×10~2—1.7×10~3,镎中钍分离系数40—5.4×10~2,镎中钚分离系数仅为2.3—5.3左右。     

~(60)Co γ辐照场中镎价态变化的研究

本文研究了含镎的硝酸-硝酸铀酰溶液在~(60)Coγ辐照场中镎价态变化的规律。观察了硝酸浓度、硝酸铀酰浓度及辐照剂量对镎价态变化的影响。结果表明:起始价态以镎(Ⅴ)为主的溶液经辐照后发生了辐射氧化-还原反应而生成镎(Ⅳ)和镎(Ⅵ),其生成量的多寡取决于溶液成份及辐照条件,起始价态以镎(Ⅵ)为主的溶液在辐照场中镎被还原;起始价态以镎(Ⅳ)为主的溶液在辐照场中镎被氧化。本文也对~(60)Coγ辐照场中镎价态变化的反应机理进行了一些讨论。     

高效离子交换树脂

【美国《化学工程》1983年12月26日第51页报道】美国道化学公司已生产出一种粒度均匀的新离子交换树脂,即所谓道韦克斯单球树脂。该公司说,颗粒粒度均匀的树脂能提高混合床(阳离子和阴离子交换树脂的混合床)离子交换设备的有效离子交换容量。这种树脂在价格上可与普通型树脂竞争。离子交换树脂运转一个周期后必须进行     

分子筛床对氚化水气体过滤效能的研究

为了准确掌握分子筛床在现场的实际防护效果,需要进行含氚(氚化水,HTO)空气穿透实验。将露点一定、氚浓度一定的普通氮气以稳定的流速通过分子筛床,并连续测量气体通过分子筛床前后氚浓度的变化和分子筛床穿透前后的质量变化,从而确定分子筛床在现场实际环境中的防氚效果。实验结果表明,无水分子筛床的氚化水吸附效果最好,4 h之内的过滤效率保持在95%以上,过滤效率高,使用时间长;1/3吸水的分子筛床的吸附效果较好,3 h之内过滤效率保持在90%以上。综合考虑使用舒适度和过滤效能,1/3吸水的分子筛床更适合用于现场的实际氚防护。     

基于球床密实实验装置的熔盐堆分流板设计

在熔盐球床堆设计中,为实现堆芯内部燃料球堆积结构的稳定性,需保证堆芯内部的流场均匀分布。研究基于模拟熔盐球床堆堆芯水力特性的球床密实实验装置(Pebble bed dense experiment facility,PBDE),通过设计不同形状和不同孔道分布的分流板,运用计算流体力学(Computational fluid dynamics,CFD)方法使用FLUENT软件对其堆芯内部的流场分布进行数值模拟,目的是保证实验中堆芯的流场分布均匀稳定。模拟结果表明,平板形分流板较锥形分流板能更好地使堆芯内流场均匀分布;且增加分流板的孔道数目或减小孔径能使堆芯内部的流场更加均匀稳定;比较设计的6种分流板模拟结果,最终给出满足PBDE堆芯流场均匀分布的分流板,为PBDE实验提供了基础,也为熔盐球床堆的堆芯流量分配设计提供技术方案与选型参考。     

从Purex流程中放废液中回收和纯化镎、钚、铀的研究

本文报道了用逆流萃取串级实验方法研究Purex过程钚线2 A槽镎走向控制的实验结果。研究了从Purex过程中放废液(2AW 2DW)中用过氧化氢,硝酸肼-亚硝酸钠、硝酸肼-硝酸羟胺-发烟硝酸作氧化还原剂,定量共萃镎、钚、铀的工艺条件。还研究了定量反萃镎和分离钚、铀的工艺条件。按所推荐的工艺条件,钚线2 AW中镎回收率可达92-95%。2 M共萃槽中镎与钚的回收率均大于99%,铀回收率大于99.99%。2 N反萃槽中镎反萃率可达99.5—99.9%。镎铀分离系数达1.4×10~4—1.6×10~4,镎钚分离系数达1.5—13。     

Systematic study of anomalous fragment anisotropies in subbarrier complete fusion—fission reactions

The complete fusion-fission is separated from the transter-induced-fission with the fragment folding angle technique.The cross sections and fragment angular distributions for the complete fusion-fission reactions of 11B 238U(237Np),237NP,16O 232Th(238U) and 19F 232Th at near-and sub-barrier energies have been measured.The present fusion and fission standard models can reproduces both the excitation functions and the fragment anisotropies for the systems of 11B 238U(237Np)and 12C 237Np;but fail to explain both the experimental data for the other 3 systems simultaneously,The evidence of the entrance-channel dependence of fission-fragment anisotropies is revealsed by comparison of the 11B 237NP and ^16O 232Th data.Based on the observations a new version model of preequilibrium fission is put forward to explain the anomaly.     

Comparison of Four Bidentate Phosphoric and Diamide Compounds for the Extractability of Actinides

Using four bidentate phosphonate and diamide ligands (L), the extraction of Am(III), Th(IV), Np(V) and U(VI) was studied and their extraction species and extractability in these extractants were discussed. The extractant containing the phosphoric oxygen has stronger chelation than that with the carbonyl oxygen atoms. The molar ratios in the main chemical forms extracted are 1:3 for Am:L, 1:1 for Th:L and Np:L and 1:2 for U:L from the relationship between log D(An) and log[L]. The order of D in actinides with the different oxidation states is U(VI)>Th(IV)> Am(III)>Np(V), which shows the different order from that for HDEHP and HTTA, namely Th(IV)>U(VI)> Am(III)>Np(V). It is clear that BDPPM, a diphosphoric dioxide extractant, has high extractability towards all An used here.     

Purex流程铀钚分离工艺中锝对镎走向的影响

在HNO3-U(Ⅳ)-N2H4-Tc(Ⅶ)-Np(Ⅴ)体系中,Np(Ⅴ)迅速还原为Np(Ⅳ)。对比研究表明,Tc是该体系中Np(Ⅴ)迅速还原的主要原因。该体系中的主要反应是U(Ⅳ)将Tc(Ⅶ)还原为Tc(Ⅳ),进而Tc(Ⅳ)将Np(Ⅴ)还原为Np(Ⅳ)。本文通过串级和台架实验研究了该体系中锝对镎走向的影响。结果表明,Np(Ⅴ)的还原速度随HNO3浓度、初始Tc浓度的增大和温度的升高而加快。在模拟Purex流程铀钚分离工艺的条件下,试管串级和微型混合澄清槽台架实验结果表明,提高1AP料液中Tc(Ⅶ)的浓度、升高反应温度,Np进入1BU中的百分含量增加。     

30%TBP/煤油-硝酸溶液体系中镎的化学行为

为了解镎在萃取过程中的化学行为,采用单级萃取研究了硝酸溶液中Np(Ⅴ)氧化为Np(Ⅵ)的行为和此过程中TBP萃取Np(Ⅵ)的性能。实验结果表明,提高硝酸浓度有利于Np(Ⅴ)的氧化,提高了萃取体系对Np(Ⅵ)的萃取;提高亚硝酸浓度加快了Np(Ⅵ)和Np(Ⅴ)之间氧化还原反应的进行,但是会降低平衡后萃取系统中Np(Ⅵ)的比例;升高温度可以提高Np(Ⅴ)转化为Np(Ⅵ)的速率。通过模拟1AF料液的混合澄清槽台架实验表明,自1AX中引入0.01 mol/L HNO2,同时将萃取温度升高到45℃,在1AF硝酸浓度为3.5mol/L的条件下,1A槽镎的萃取率可以达到80%。     

腐殖酸对Np胶体行为的影响

在模拟高放废物深地质处置的低氧低浓条件下,探讨用膜过滤法研究Np胶体行为的可行性。实验研究结果表明:无腐殖酸存在时,在pH=1～13条件下,无机离子对237Np的测定无明显影响,237Np的液闪探测效率可达100%;增加闪烁液用量可消除腐殖酸对237Np的淬灭效应,过滤器对237Np的吸附可忽略不计,说明将过滤法应用于Np的胶体行为研究准确、可靠,操作简便。应用该方法对Np的不同价态和腐殖酸存在下的胶体行为进行了研究。Np(Ⅴ)无明显胶体行为,Np(Ⅳ)以真胶体形态存在,其浓度显著影响胶体行为;腐殖酸与Np(Ⅳ)能形成假胶体,从而提高了Np(Ⅳ)在溶液中的含量,有利于Np的迁移。腐殖酸是核素迁移研究必须考虑的重要影响因素。     

The chemical reduction of neptunium to the trivalent state

It was established spectrometrically that 1–1.5 M nitric and hydrochloric acid solutions of sodium formaldehyde sulfoxylate (rongalite) reduce Np (IV) to Np (III). The reduction proceeds both in an atmosphere of nitrogen and in air, but the degree of reduction and the stability of Np (III) are increased in an atmosphere of nitrogen. It is known that an increase in the total amount of the reducing agent in the solution (hydrazine + rongalite) promotes the reduction of neptunium to the trivalent state; neptunium is reduced on the average by 70% in nitric acid solutions and by 95% in hydrochloric acid solutions.It was found that reduction of Np (V) with rongalite gave a mixture of Np (III) and Np (IV). In the Np (IV) and Np (III) mixture, the latter shows a noticeable stability to oxidation with aerobic oxygen.     

Absolute Fission-Rate Distributions in Lithium and Hybrid Fusion Blanket Assemblies, (II)

The absolute fission rates of ²³⁵U, ²³⁷Np, ²³⁸U and ²³²Th were measured in four types of spherical blanket assemblies containing lithium and/or natural uranium and/or graphite. The results of measurement are compared with those of one-dimensional transport calculations employing 100-group neutron cross-sections obtained from the ENDF/B-IV data file. It is shown that the ratios between calculated and experimental values of ²³²Th, ²³⁸U and ²³⁷Np fission rates decrease with distance from the assembly center, where D-T neutrons are generated. An overestimation of about 50% is observed in the calculated ²³⁵U fission rate for the graphite reflector region.

One of the main sources of the disagreement proves to lie in the inability of the codes adopted for generating the multi-group cross-section to take account of the angular distributions of the secondary neutrons emanating from nonelastic reactions. The results of the analysis indicate that the method of calculation currently employed in fusion reactor neutronics overestimates the reflection of neutrons and underestimates the penetration of fast neutrons when a graphite reflector is used.     

用于核电站放射性惰性气体处理的常温活性炭滞留床研究

本文介绍了用于核电站放射性惰性气体处理的常温活性炭滞留床，试验结果表明，１１种市售国产活性炭大多数可用于常温活性炭滞留床，其中椰壳０１、０２炭，果壳１１、１２炭较好，滞留床吸附性能的主要影响因素包括：气流比速、压力、温度、活性炭含水量。设计的滞留床具有以下特点；常温操作，设备与操作过程较简单，操作压力低，比较安全；炭床体积小，活性炭更换次数少。     

Numerical Simulation of Neptunium Extraction Behavior in Co-decontamination Stage for Late Split Purex System

Numerical simulation of neptunium concentration profiles is carried out in order to understand the extraction behavior of neptunium in the co-decontanimation stage which decontaminates through two extraction banks before the uranium and plutonium partitioning steps. Simulation results show that leaking of neptunium to the waste stream at the second extraction bank is caused by reduction from Np(VI) to Np(V) unextracted by TBP in the presence of nitrous acid of 10^?3 mol/l. It is found that the prevention of the reduction reaction from Np(VI) to Np(V) is effective for the recovery of neptunium with uranium and plutonium into the product stream. Two methods for the recovery of neptunium are suggested; i) to decrease residence time in the acid adjustment vessel located between first and second extraction banks, ii) to diminish nitrous acid in the aqueous phase by hydrazine. Simulation results show that the recovery of neptunium with uranium and plutonium is improved from 40 to 60% and kom 40 to 70% by the first and the second methods, respectively.     

球床结构对PB-FHR中子物理特性的影响研究

氟盐冷却高温球床堆（PB-FHR）中燃料球的装卸依靠浮力完成。球床结构受堆芯几何、装卸料速度、熔盐密度、熔盐流动等诸多因素的影响,其不确定性是反应堆物理设计和安全分析中重点考虑的内容。参考装卸料实验台架（PRED）的实验结果,采用蒙特卡罗程序（MCNP）完成了固态燃料钍基熔盐实验堆（TMSR-SF1）球床堆积密度、球床底部形状、冷却剂泄漏导致的液位下降等因素对中子物理关键参数的影响分析。结果表明,堆积密度的增加（50%~64%）导致燃料球装载量的增加、有效增殖因数的增加、温度系数的增加和控制棒价值的减小;相对于平坦型球床底部结构,外锥型结构会随着锥角的增加导致反应性先增加后减小,内锥型和斜面型结构则会引入负反应性;冷却剂泄漏事故引起的堆芯冷却剂液位大幅降低会导致堆积密实并引入负反应性。