铀污染的不锈钢表面去污方法研究

随着一批核设施陆续服役期满 ,其退役问题已成为核废物管理中的重要内容[1 ] 。退役物件要求去污后能满足一般场合使用。目前去污是以化学方法为主 ,辅之以机械和熔炼方法。若污染物质沉积较厚 ,表面腐蚀严重的部件 ,则先用器械初步去污 ,然后再用化学方法去污 ;具有光洁或轻微污染的表面 ,用蘸有酸碱去污剂的棉纱反复擦试 ,即可取得良好效果 ;污染严重或几何形状复杂的部件 ,用酸碱溶液浸泡后 ,高压水冲洗即可。大部分部件的污染形式呈现为表面污染 ,依靠不同浓度的酸碱去污剂 ,即可取得满意的效果[2 ] 。цамерян等[3] 研究了涂料表…     

NaF+HNO3浸泡法去除金属部件表面241Am污染

241Am是极毒、亲骨超钚核素,主要发射5.49MeVα粒子和59.6keV的γ射线,半衰期为423年。曾经作为烟雾探测器广泛地应用于火灾报警器生产中,长期的生产造成了生产线各个部位,尤其是金属部件表面存在较为严重的放射性污染。在其生产线退役过程中,需要对这些污染表面进行去污以减少操作人员受照剂量和退役过程废物产生量。放射性污染的去污按去污机理可分为机械法、化学法、物理法和电化学法等[1]。其中化学浸泡去污在核设施退役中应用较为广泛[2]。NaF HNO3浸泡去污工艺早期由前苏联开发,针对的去污对象主要为不锈钢,开始采用的试剂组成为3…     

反应堆一回路不锈钢管道沉积物制备及去污的模拟研究

反应堆一回路管道通常以不锈钢为基材,长期运行中面临沉积物的产生及大量积累的问题。本文通过溶液反应模拟沉积物的产生,采用的水溶液中含有Ca²⁺、Mg²⁺,以及裂片核素¹³⁷Cs和活化核素⁶⁰Co的稳定同位素阳离子¹³³Cs+和⁵⁹Co²⁺,CO₃^2-、SO₄^2-等阴离子,以及基材氧化物Fe₂O₃等;开展了沉积物化学溶解去污处理技术研究。实验结果表明,沉积物中含钙、镁、钴、铯及铁等元素;采用苹果酸+柠檬酸双组份的去污体系,沉积物的溶解率可达98.44%,且该弱酸复配体系去污液对不锈钢基体的腐蚀作用较小。     

涂膜超声及涂膜电解对固体表面铀的去污研究

制备了高分子可剥离去污膜液，确定了涂膜液中各组分最佳含量，对固体表面核素的去除研究结果表明：在金属表面采用涂膜电解去污、非金属光滑固体表面采用直接涂膜去污、非金属粗糙固体表面采用涂膜超声去污工艺，其去污率均可达99％以上，优于其他方法。     

铀的复合吸附材料

铀是重要核燃料资源,也是放射性废液中主要的污染元素之一。铀的吸附涉及到溶液中铀的提取、含铀废水的处理和铀元素化学分析的预富集等。本文从有机官能团化学键合修饰基体的复合材料出发,从基体和有机官能团两方面对溶液中的铀的吸附行为进行了综述,分析了各种官能团所适用的水相pH值、对铀的吸附量和选择性。含有机磷类官能团的复合材料具有pH适用范围广、吸附量和选择性较好的优点,是一种具有良好发展前景的铀复合吸附剂。     

炭材料对铀的吸附

铀既是核燃料的主要成分又是乏燃料后处理的关键核素。将铀从乏燃料后处理流程中的高放射性料液或者其他含铀废水中分离出来既可以将此宝贵的核燃料回收使用,又有利于降低乏燃料处理后期的处置费用,以及减少铀对环境的污染。而从海水、盐湖水、尾矿废水等贫铀水体中提取铀则可能是解决将来铀资源匮乏的主要方法。炭质材料具有较大的比表面积、较高的孔隙率,耐高温,抗辐射,对各种酸碱环境有很高稳定性,而且本身无毒,环境友好,有望作为吸附剂或固相萃取材料用于从水体中吸附分离铀。本文介绍了活性炭、介孔炭、碳纳米管等材料对铀的吸附研究进展。表面功能化可以提高炭材料对铀酰离子的吸附容量与选择性,对炭材料功能化的方法主要有表面氧化、浸渍、负载和接枝等手段。由于化学稳定性高,采用化学方法在炭材料表面接枝功能分子是具有应用前景的研究方向。采用碳纤维作电极,电吸附铀的方法可以大量地从水溶液中将铀吸附到电极表面,再通过电脱附回收铀,具有工业化应用前景。     

模拟氧化凝胶去污废液的预处理初步研究

为了探索氧化凝胶二次废液的预处理方法,了解二次废液的基本特征,开展了模拟氧化凝胶去污废液的预处理初步研究。采用过氧化氢处理模拟氧化凝胶废液中残余Ce(Ⅳ),以中和、过滤法对废液进行处理,并对模拟废液中沉淀物及其粒径分布进行测定。结果表明:利用过氧化氢处理模拟氧化凝胶去污废液中残余的Ce(Ⅳ),其反应迅速、完全;当调节模拟废液pH为9时,模拟废液中湿沉淀量为88.4 g/L,干沉淀量为18.8g/L,沉淀物的粒径主要集中在1.783～10μm。     

有机废液实现无害化处理

哈尔滨工业大学为解决实验室有机废液的污染问题,成功研制了电加热流化床废液焚烧炉及尾气净化装置。经有关专家监定,用该装置处理后的实验室废液,其各项指标均远低于环保排放标准,并具有操作简便、造价低、运行费用低等优点。 国家环保总局要求实验室废液必须经无害化处理后方可排放。而目前全国各大学、科研院所和中学在做化学实验     

壳聚糖与壳寡糖结构及其对放射性核素铀吸附性能

采用酸碱滴定法测定壳聚糖和壳寡糖脱乙酰度分别为90.9%和90.1%,用IR方法表征了壳糖中乙酰基和氨基。 MALDI-FT-MS进一步给出了经葡聚糖凝胶柱纯化后壳寡糖脱乙酰度和聚合度的信息。 通过壳聚糖吸附性能的研究发现,壳聚糖对放射性核素铀具有较强的吸附能力,吸附率达96%以上,即使在大量Cu2+存在情况下,也可高效吸附放射性核素铀,说明壳聚糖有望成为一种新型的放射性核素吸附去污材料。     

成膜溶剂与氟化嵌段共聚物膜的表面富集行为

利用接触角、XPS、SFG、AFM等技术研究了环己酮、甲苯和三氟甲苯为成膜溶剂所得聚甲基丙烯酸甲酯-b-聚（甲基丙烯酸-2-全氟辛基乙酯）（PMMA—b—PFMA）嵌段共聚物膜的表面结构与性能．发现浇铸成膜时成膜溶剂对聚合物氟化组分向表面富集程度的影响相对较小,而旋涂成膜时溶剂的影响很大．不管以何种形式成膜,三氟甲苯溶剂最有利于氟化组分向表面富集,甲苯次之,环己酮最差．这一现象与溶剂的挥发速度无关．聚合物在溶液中的聚集结构、气／液界面结构是造成成膜方式对聚合物表面结构与性能产生巨大影响的主要原因．当聚合物在溶液中形成以PFMA为核、PMMA为冠的胶束结构时,在溶液固化过程中氟化组分向表面富集需要较长的时间,这时由于成膜方法直接影响溶液的固化速度,造成其对氟化组分向表面富集的程度影响很大．当聚合物在溶液中以单分子或松散聚集体存在,在溶液固化过程中氟化组分向表面富集的速度很快,这时成膜方法对氟化组分向表面富集的程度影响很小．以上结果无论对理论研究还是应用研究都具有重要意义．     

Decontamination of chemical warfare agents using perchloroethylene–Marlowet IHF–H2O-based microemulsions: wetting and extraction properties on realistic surfaces

At the present time, considerable efforts are being made to develop new media for the decontamination of a variety of toxic compounds. In the present contribution, new microemulsions with promising properties are presented. Moreover, the decontamination of surfaces, with an emphasis on varnished metal surfaces of exterior and interior equipment, is investigated using these microemulsions. Studies of the phase behavior of the system water–perchloroethylene–IHF–2-propanol are reported and the microemulsion phases are recognized. The wetting behavior on contaminated surfaces and the extraction capabilities with respect to contaminants are essential for an efficient decontamination. Hence, suitable microemulsions are identified on the basis of these properties. The decontamination efficiency of these microemulsions is first estimated on the basis of the ability to wet typical chemical nonresistant varnished steel sheets, which are authentic model systems for real surfaces. Afterwards, promising microemulsions and, as reference, different solvents are tested with respect to their capability to solubilize sulfur-mustard agent, again using realistic surfaces contaminated with this chemical warfare agent. Several microemulsions are found, which have the desired properties.     

Hydrodynamics of the effectiveness of the AP-CITROX decontamination technology

During the optimization of the AP-CITROX decontamination technology the effect of the different flow rates of the decontamination solutions on the radioactive contamination and corrosion state of stainless steel tube samples originating from steam generators of Paks NPP were studied by a pilot-plant circulation system. The results have proved that a significant increase (up to 2.89 m/s) in the flow rate of the decontamination solution in the 1-5 steps is highly recommended and in order to improve the passivity of the surfaces it should be kept as low as possible (0.5 m/s) during the passivation.     

Selective separations via recrystallization

The principles of selective separations by recrystallization are explained and formulae for the calculation of decontamination factors are presented. Experiments with strontium sulfate and radioactive strontium ions demonstrate the validity of the theoretical considerations. Similar or higher decontamination factors are found than those calculated for a uniform distribution of the radioactive strontium ions between crystals and solution. The high values are explained by assuming a recrystallization mechanism which consists of dissolution and redeposition of crystal layers. The half-times of recrystallization increase sharply with Sr²⁺ or SO ₄ ²⁻ concentration in the solution. In nitric acid solutions as well as in mixtures containing nitrates and nitric acid the solubility of strontium sulfate is rather high, accordingly the decontamination factors are low under these conditions and furthermore the recrystallization half-times are long.     

Comparative study of the corrosion and surface chemical effects of the decontamination technologies

Decontamination technologies are generally developed to reduce the collective dose of the maintenance and operation personnel at nuclear power plants (NPP). The highest efficiency (i.e., the highest decontamination factors) available without detrimental modification of the treated surface of structural material is the most important goal in the course of the application of a decontamination technology. At the Paks NPP the AP-CITROX procedure has been utilized for the decontamination of the primary coolant circuit’s components (e.g., main circulating pump (MCP) and steam generators (SGs)). Our previous studies have revealed that a ‘hybrid’ structure of the amorphous and crystalline phases was formed in the outermost surface region of the austenitic stainless steel tubes of SGs as an undesired consequence of the industrial application of the AP-CITROX decontamination technology during the period of 1993–2001. In this paper, we report some comparative findings on the corrosion and surface chemical effects of the AP-CITROX procedure and the novel decontamination technology elaborated at our institution. On optimizing the operational parameters the latter technology may become suitable for the effective decontamination of both dismountable (e.g., MCP swivel) and separable (e.g., SGs) equipments. For this purpose experiments were performed. In this laboratory scale experiments, the passivity, morphology and chemical compositions of the treated surfaces of tube specimens were investigated by voltammetry, and SEM–EDX methods, respectively. The SEM–EDX results have revealed that the oxide removal is surprisingly uniform even after 2 or 3 consecutive cycles. The electrochemical studies have provided evidences that no unfavorable tendencies in the general corrosion state of the tube samples can be detected in the course of the chemical treatments.     

化学事故处置中的洗消现状及发展

介绍了目前我国化学事故处置中洗消的定义、洗消剂的种类、洗消方法及洗消的发展,以增强人们对化学事故处置中洗消的认识和了解。     

Chemical analysis of bleach and hydroxide-based solutions after decontamination of the chemical warfare agent O-ethyl S-2-diisopropylaminoethyl methylphosphonothiolate (VX)

Detailed chemical analysis of solutions used to decontaminate chemical warfare agents can be used to support verification and forensic attribution. Decontamination solutions are amongst the most difficult matrices for chemical analysis because of their corrosive and potentially emulsion-based nature. Consequently, there are relatively few publications that report their detailed chemical analysis. This paper describes the application of modern analytical techniques to the analysis of decontamination solutions following decontamination of the chemical warfare agent O-ethyl S-2-diisopropylaminoethyl methylphosphonothiolate (VX). We confirm the formation of N,N-diisopropylformamide and N,N-diisopropylamine following decontamination of VX with hypochlorite-based solution, whereas they were not detected in extracts of hydroxide-based decontamination solutions by nuclear magnetic resonance (NMR) spectroscopy or gas chromatography-mass spectrometry. We report the electron ionisation and chemical ionisation mass spectroscopic details, retention indices, and NMR spectra of N,N-diisopropylformamide and N,N-diisopropylamine, as well as analytical methods suitable for their analysis and identification in solvent extracts and decontamination residues.     

Decontamination of radionuclides on construction materials

A wide variety of materials can become contaminated by radionuclides, either from a terrorist attack or an industrial or nuclear accident. The final disposition of these materials depends, in large part, on the effectiveness of decontamination measures. This study reports on investigations into the decontamination of a selection of building materials. The aim has been to find an effective, easy-to-use and inexpensive decontamination system for radionuclides of cesium and cobalt, considering both the chemical and physical nature of these potential contaminants. The basic method investigated was surface washing, due to its ease and simplicity. In the present study, a basic decontamination formulation was modified by adding isotope-specific sequestering agents, to enhance the removal of cesium(I) and cobalt(II) from such construction materials as concrete, marble, aluminum and painted steel. Spiking solutions contained ¹³⁴Cs or ⁶⁰Co, which were prepared by neutron activation in the SLOWPOKE-2 nuclear reactor facility at the Royal Military College of Canada. Gamma spectroscopy was used to determine the decontamination efficiency. The results showed that the addition of sequestering agents generally improved the radiological decontamination. Although the washing of both cesium and cobalt from non-porous materials, such as aluminum and painted steel, achieved a 90–95 % removal, the decontamination of concrete and marble was more challenging, due to the porous nature of the materials. Nevertheless, the removal efficiency from 6-year-old concrete increased from 10 % to approximately 50 % for cobalt(II), and from 18 to 55 % for cesium(I), with the use of isotope binding agents, as opposed to a simple water wash.     

A rapid solvent extraction method for the determination of caesium-137 in environmental materials

A solvent extraction method for the quantitative determination of caesium-137 in environmental samples is described. Caesium carrier is added to the ashed sample, which is dissolved with hydrochloric acid. The solution is filtered to remove any carbon and the pH is adjusted to 2.0. Sodium dodecylbenzene sulphonate is added and the extraction is done with phenol-nitrobenzene mixture. The organic phase is washed with EDTA solution and the caesium is stripped from the washed solvent with 6 M hydrochloric acid. The caesium is precipitated as caesium chlorostannate to ensure absolute decontamination from potassium-40. Recovery from standard solution is about 85% and from vegetation, rainwater and effluent samples about 80%. The method is applicable in the presence of large quantities of interfering ions, and decontamination factors for many nuclides are greater than 10³.     

Synthesis and characterization of zeolite Linde Type W and its metal oxide composite Ag-O-LTW used for the decontamination of chemical warfare agent simulant

Abstract

In this study, we have evaluated the performance of novel adsorbent zeolite Linde Type W and modified LTW with AgO metal oxide composite for the decontamination of chemical warfare agent simulant 2-chloroethylphenylsulphide (CEPS). Zeolites are nanoporous aluminosilicate minerals composed of silicon, aluminum and oxygen framework with cations and water molecules within the pores. The synthesized zeolite LTW and its composites Ag-O-LTW was characterized by XRD, FTIR, SEM-EDS and BET analytical techniques. The decontamination study of CWA simulant, CEPS was monitored by using GC-FID technique. The nanocrystalline zeolite LTW and Ag-O-LTW composites were found powerful adsorbents and showed great decontamination potential toward CWA simulant CEPS. The Ag-O-LTW showed better results (～98 % decontamination in 7?hours) than LTW zeolite.