Gaseous products generated by radiation degradation of N,N-diethylhydroxylamine aqueous solution

In this paper, gaseous products generated by radiation degradation of N,N-diethylhydroxylamine (DEHA)in aqueous solution are studied. The results show that by 10～1000 kGy irradiation of the solution in DEHA volume fraction of hydrogen did not change much with different concentrations of DEHA. The volume fraction of methane and ethane decreased, but that of ethene increased, with increasing DEHA concentration. The volume fraction of hydrogen, methane and ethane increased with the dose. The relationship of the volume fraction of ethene with the dose had something to do with the DEHA concentration.     

EM>N/EM>，EM>N-/EM>二乙基

研究了N,N-二乙基羟胺(DEHA)水溶液辐解产生的气态烃。当DEHA浓度为0.1~0.5 mol/L,剂量为10~1 000 kGy时,甲烷、乙烷、丙烷和正丁烷的体积分数随剂量的增加而增加,但随DEHA浓度的增加而减少。乙烯和丙烯的体积分数随DEHA浓度的增加而增大,它们与剂量的关系与DEHA浓度有关。     

Gaseous products of aqueous N,N-dimethyl hydroxylamine degraded by radiation

In this work,the 0.1-0.5 mol·L-1 N,N-dimethylhydroxylamine(DMHA) were irradiated to 5-25 kGy,and gaseous products of mainly hydrogen,methane,ethane and n-butane were measured by gas chromatography.The results show that the volume fraction of hydrogen and methane increases with the concentration of DMHA and dose,and the latter does not change markedly at high doses.     

羟胺衍生物的辐解研究Ⅱ.N,N-二乙基羟胺辐解产物中气态烃类的定性定量分析

用三氧化二铝毛细柱与氢火焰离子化检测器联用的气相色谱法,定性定量分析了N,N-二乙基羟胺水溶液辐解产生的气态烃类。结果表明：当吸收剂量为10～1000kGy时,N,N-二乙基羟胺水溶液辐解产生的气态烃类主要有甲烷、乙烷、乙烯、丙烷和正丁烷。甲烷、乙烷、丙烷和正丁烷的体积分数都随吸收剂量的增加而增加;而乙烯的体积分数先是随剂量的增加而增加,当剂量大于500kGy时,其体积分数则随剂量的增加而明显减少。     

喇曼光谱法研究辐照聚合物的气体产值

本文研究了两种典型交联型聚合物在~(60)Coγ射线辐照条件下放出的气体的激光喇曼光谱,通过波数2917cm~(-1),2954cm~(-1)和4157cm~(-1)三处特征谱峰高度与标准谱图的比较,测得辐照聚二甲基硅氧烷放出的各种气体产值:G_(CH_4)=1.05,G_(C_2H_6)=0.23,G_(H_2)=0.58,气体总产值:G_(CH_4-C_2H_6+H_2)=1.86,实验结果表明,在500Mrad剂量以下,辐照样品放出气体的总产值和各种气体的分产值不随剂量而变化,从而给予交联度与剂量成正比以直接证明。用同样方法测得辐照聚乙烯放出的气体产值(G_(CH_2)=2.7),也与辐照剂量无关。     

N,N-二甲基羟胺辐解产生的氢气和一氧化碳的研究

With the development of nuclear power industry, more attentions have been paid on reprocessing power reactor spent fuel. Up to now, PUREX process is the only process available commercially. The process achieves uranium and plutonium separation by means of quick and quantitative reduction of Pu (Ⅳ) to Pu (Ⅲ). Therefore the reductant is very important in PUREX process. Preliminary experiment results[1] show that N, N-dimethyl hydroxylamine not only reduces rapidly Np (Ⅵ) and Pu (Ⅳ) to Np (V) and Pu (Ⅲ), but also stabilizes the Np (V)and Pu (Ⅲ) in acid solution. It may become a salt-free reductant with promising future for applications in the area[2]. However, organics decompose under intense radiation environment, and this affects its reduction efficiency,and products from the degradation may affect separation of the radioactive elements.This paper reports the qualitative and quantitative analysis of hydrogen and carbon monoxide produced by 60Co y-ray degradation of N, N-dimethyl hydroxylamine. The analyses of hydrogen and carbon monoxide were performed by gas chromatography, in which a 2m column packed with 5A molecular sieve and thermal conduc tivity detector[3] were used. The analysis of hydrogen employed argon as carrier gas, the column temperature was 80℃ and the detector temperature was 110℃. The analysis of carbon monoxide used hydrogen as carrier gas, the column temperature was 50℃ and the detector temperature was 80 ℃. The results show that when the concentration of N, N-dimethyl hydroxylamine was between 0.1 mol/L and 0.5 mol/L and the dose delivered by the irradiation was 10-1000 kGy, the volume fraction of hydrogen was (8.0-303.9)× 10-3; and the volume fraction of carbon monoxide is (0-1.7)× 10-3. The volume fraction of hydrogen increased with increasing dose, and it has little relationship with concentration change of N, N-dimethyl hydroxylamine when the irradiation dose was bellow 500 kGy, whereas it increased with the increasing concentration of N, N-dimethyl hydroxylamine when the dose was higher than 500 kGy. The volume fraction of carbon monoxide has little relationship with both the irradiation dose and N, N-dimethyl hydroxylamine concentration.     

Analyses of organics in irradiated aqueous N, N-diettiyihydroxylamine solution

The organics in γ-ray irradiated aqueous N, N-diethylhydroxylamine （DEHA） solution, which is used as a reducing agent in reprocessing spent nuclear fuel, were analyzed with gas chromatography equipped with FFAP capii- lary colunm and flame-ionization detector. It was found that irradiated DEHA solutions contained acetaldehyde, ethanol, and acetic acid. For DEHA of 0.2 mol/L irradiated to 10-1000 kGy, the concents of acetaldehyde, ethanol and acetic acid are （9.7-18.7）×10^3, （0.4-23.4）×10^3 and （6.5-11.7）×10^3 mol/L, respectively. The concentration of DEHA decreases obviously with the dose.     

Radiolytic organics in γ-ray irradiated aqueous solution of N,N-diethylhydroxylamine

N,N-diethylhydroxylamine (DEHA) is a novel salt-free reducing agent used in separating Pu and Np from U in the reprocessing of spent nuclear fuel.In this paper,we report the study on γ-radiolysis of DEHA in water and its radiolytic liquid organics by gas chromatography.The radiolysis rate of DEHA increases with the absorbed dose,but decreases with the primary DEHA concentration at 0.1-0.5 mol?L-1 irradiated to 10-1000 kGy.The main organics produced in radiolysis of DEHA are acetaldehyde,acetic acid and ethanol.The concentration of acetaldehyde increases with the primary DEHA concentration and the absorbed dose at ≤500 kGy,but over 500 kGy it decreases with increasing dose.The dependence of the concentration of acetic acid on the absorbed dose is similar to that of acetaldehyde,with a lower turning point of the dose,though.The ethanol concentration changes differently among the irradiated samples of different primary DEHA concentrations,and this is discussed.The maximum concentrations of acetaldehyde,acetic acid and ethanol are 0.029,0.014 and 0.028 mol·L-1,respectively.     

Analyses of organics in irradiated aqueous N,N-diethylhydroxylamine solution

The organics in γ-ray irradiated aqueous N, N-diethylhydroxylamine (DEHA) solution, which is used as a reducing agent in reprocessing spent nuclear fuel, were analyzed with gas chromatography equipped with FFAP capil-lary column and flame-ionization detector. It was found that irradiated DEHA solutions contained acetaldehyde, ethanol, and acetic acid. For DEHA of 0.2 mol/L irradiated to 10～1000 kGy, the concents of acetaldehyde, ethanol and acetic acid are (9.7～18.7)×10-3, (0.4～23.4)×10-3 and (6.5～11.7)×10-3 mol/L, respectively. The concentration of DEHA decreases obviously with the dose.     

Effect of Hydrogen Atmosphere on Radiation- Induced Gas Evolution from Polyisoprene

Polyisoprene was irradiated in hydrogen atmosphere by ⁶⁰Co γ-rays. The evolved gases were methane, ethane, ethylene, propane, propylene and butane. With respect to saturated hydrocarbons, the yields increased with increasing pressure of hydrogen. On the contrary, the yields of unsaturated hydrocarbons decreased. The G-value of methane in hydrogen of 1 MPa was about four times larger than that in vacuum for irradiation of cis-polyisoprene (Cis) at 160 kGy. The gas evolution from trans-isomer (Trans) was about the same as that from Cis. The yields of gases from gloves made of natural rubber were smaller than those from Cis or Trans.     

Reaction of atomic hydrogen with chemisorbed species: C2H4 on W

Atomic hydrogen produced in controlled thermonuclear reactors is capable of very rapid reaction with both the material of the first wall and with adsorbed species. We have been investigating the reactions of thermal atomic hydrogen with ethylene adsorbed on a tungsten film. When adsorbed at room temperature ethylene reacts to yield gaseous hydrogen and a carbonaceous residue which reacts with incident atomic hydrogen to yield methane along with minor amounts of ethane. This product distribution, however, depends on the chemical nature of the adsorbed species. Adsorption at 178K, a temperature at which the ethylene molecule is stable, inverts this distribution with ethane now being the major product. Analysis of the system dynamics shows that the rate of production of each product is proportional to the product of the steady state increase in the product pressure and the pumping time constant of the vacuum system. For the case of methane production following room temperature adsorption of ethylene, the reaction probability for the production of methane for the reaction C + 4H → CH₄is ~0.001 and arguments are given for a larger value.     

甲异羟肟酸-硝酸辐解产生的H2和CO

甲异羟肟酸(FHA)是有望用于乏燃料后处理的新型无盐络合剂.用5(A)分子筛填充柱与热导池检测器(TCD)联用的气相色谱法研究了HNO_3-0.2 mol/L FHA辐解产生的H_2和CO.H_2的分析是以Ar作载气,柱温为85 ℃,TCD温度为120 ℃; CO的分析是以H_2作载气,柱温为50 ℃, TCD温度为80 ℃.研究结果表明,H_2的体积分数随剂量的增加而增大,随HNO_3浓度的增大而减小;CO只有在剂量很高时才产生,且其体积分数远比H_2低,CO的体积分数随剂量的增加而增加.当c(HNO_3)≤0.5 mol/L时,CO体积分数低于0.2 mol/L FHA水溶液辐解产生的CO,但当c(HNO_3)≥1.0 mol/L时,CO的体积分数大于0.2 mol/L FHA水溶液辐解产生的CO, 且CO体积分数随c(HNO_3)的增大而增大.     

Numerical modelling of a low power non-transferred arc plasma reactor for methane conversion

Thermal flow characteristics and the methane conversion reaction in a low power arc plasma reactor for efficient storage and transport of methane, which is the main component of shale gas, were simulated. The temperature and velocity distributions were calculated according to the type of discharge gases and arc current level by a self-developed magnetohydrodynamics (MHD) code and a commercial ANSYS-FLUENT code; the transport of chemical species was analyzed as including the chemical reactions of methane conversion. The simulated results were verified by the comparison of calculated and measured arc voltages with permissible low error as under 4%. Three C₂ hydrocarbon gases with ethane (C₂H₆), ethylene (C₂H₄), and acetylene (C₂H₂) were selected as the converted species of methane from experimental data. The mass fraction of C₂ hydrocarbons and hydrogen as the product of the conversion reaction at the reactor was also calculated. Those values show good agreement with the actual experimental results in that the major conversion reaction occurred in C₂H₂ and hydrogen, and the conversions to C₂H₆, C₂H₄, and hydrogen were minor reactions of methane pyrolysis conversion.     

Non-equilibrium Plasma Dehydrogenation Coupling of Methane

1. IntroductionDirect conversion of methane is an important subiect in the field of research and application of natural gas. Methane coupling into CZ hydrocarbonsis of great significance in both the science and national economy. Some interesting results have beenobtained from the research on the oxidative couplingof methane. It has been generally agreed that themechanism of oxidative coupling of methane is asfollowsi The C--H bonds of molecular methane areactivated first, and then broken to …     

Dimensional Changes in Irradiated (Th,U)O2

Effects of irradiation on the dimension and microstructure in (Th,U)O₂ pellets were examined by measurements of lattice parameter and bulk density changes, and observations of pore structures. The concentrations of fission-induced defects and the damage volume were estimated by a simple model. Both macroscopic and microscopic dimensional changes were found to increase initially with fission dose and then fall off. The difference between macroscopic and microscopic ingrowths increased with dose, suggesting that fission-induced interstitials would cluster or go to sinks and the concentration of vacancies would be in excess of that of interstititials. The damage volume for vacancies was estimated to be about 1x10^?22m³·fiss.^?1, and almost agreed with that for fission Xe release. Observations of the pore structure indicated that the volume fraction of pores smaller than 2–3 μm decreases with irradiation and the distribution of pore size shifts toward the larger side.     

Chemical Dosimeters for Mixed Radiations in a Nuclear Reactor

The dose rates due to mixed reactor radiations were measured by five gaseous chemical dosimeters – nitrous oxide (natural), ¹⁵N-enriched nitrous oxide, ethylene, ethane and carbon dioxide. The observed dose rates for these gases at the same irradiation position in a nuclear reactor were, 1.8×10⁸, 1.5×l0⁸, 1.9×10⁸, 2.5×l0⁸ and 1.0×10⁸ rad/hr, respectively. These values were compared with those calculated from the mass stopping power of the gases for secondary electrons produced by γ-rays and those from thermal and fast neutron fluxes. No contradiction was found among them. A method of analysis of the reactor radiation dose rates into γ, thermal and fast neutron components is proposed, which is based solely on chemical dosimetry.     

Increasing 129I Transmutation Efficiency

The special features of ¹²⁹I transmutation are discussed. The changes in content and equilibrium concentration of ¹²⁷I in a target under recycling are calculated, and the conditions for decreasing the required radiochemical capacity in reprocessing of iodine are found. It is shown on the basis of an analysis of the neutron consumption in targets and estimates of the pressure of daughter xenon under the casing that the gaseous products of transmutation must be removed during the irradiation process along a loop channel. To increase the effectiveness and safety of ¹²⁹I burnup, it is recommended that ¹²⁹I be included in the volume of the gas permeable porous nuclear-inert targets by permeation with melts of iodine compounds.     

89Sr production in a reactor with solution fuel

The experimental results for the validation of a technology for producing ⁸⁹Sr in a reactor with solution fuel are presented. The aggregate state of the fuel-a water solution of uranyl sulfate UO₂SO₄-opens up a unique possibility of acting not only on the target radionuclide but also on its genetic precursors, produced as a result of nuclear transformations of the fission products as a whole in the decay chain ⁸⁹Se→⁸⁹Br→ ⁸⁹Kr→⁸⁹Rb→⁸⁹Sr. The half-life of ⁸⁹Kr (T_1/2 = 190 sec)-a gaseous precursor of ⁸⁹Sr-is sufficient for it to leave the fuel solution and migrate into the gaseous medium. A series of experiments is performed on obtaining gas samples from the free volume of the solution of the 20 kW Argus minireactor. It is shown that the mechanism of delivery of ⁸⁹Sr into the sorption volume of the experimental loop of the Argus reactor system is based on transport along the ⁸⁹Kr loop. Measurements of the content of the radioactive impurities in a solution of ⁸⁹SrCl₂ showed that the purification of the gas flow by metal-ceramic filters and purification of the solution on DOWEX-50×8 or crown ehter Sr-Resin yields medical quality ⁸⁹Sr. The productivity of the new technology, which is many-fold greater than that of the modern industrial methods for producing ⁸⁹Sr, is assessed on the basis of experimental data. __________ Translated from Atomnaya énergiya, Vol. 100, No. 5, pp. 372–382, May, 2006.     

Precipitation Formation of Zirconium-Dibutyl Phosphate Complex in Purex Process

Dibutyl phosphate (DBP) was added to 30% TBP-70% dodecane solvent (DBP concentration, 30–1,150mg/l). These samples were used to investigate distribution behavior of Zr from a 3 M nitric acid solution (Zr concentration, 60–4,000 mg/l). The experimental results show that the Zr distribution depended mainly on the total DBP/Zr mole ratio. Below DBP/Zr=2, the Zr distribution to the organic phase became larger as the DBP/Zr mole ratio increased. Above DBP/Zr=2, the Zr distribution factor was saturated. Moreover, colloidal precipitation at the interface between organic and aqueous phases was observed above DBP/Zr=2.

Then in order to characterize the precipitation, 3 M nitric acid solution containing Zr ion was directly reacted with DBP and the obtained products were analyzed by ¹³C, ³¹P and ¹⁴N NMR spectroscopy. The measured NMR spectra indicated that the products were polymers having four kinds of bonding structures. One was a hydrogen bonded structure and the others were Zr bridged structures with two to four DBP molecules coordinated per Zr atom. The Zr bridged structure with four DBP molecules was thought to make the biggest contribution to precipitate formation.     

化学气相沉积法制备ZrC涂层的热力学分析

ZrC涂层可能在新一代TRISO包覆颗粒上被用作阻挡裂变产物和承受主要载荷的关键层，是先进高温气冷堆燃料元件研究的一个重要方向。文章利用HSC-CHEMISTRY4.1软件分析化学气相沉积工艺参数对所制备的ZrC涂层的影响。分析结果表明，在载气中加入足够的氢气对制备单一ZrC涂层很有必要。ZrCl₄的转化率随着沉积温度的升高而增加，当温度过高时，其影响不明显；较佳的沉积温度范围为1400~1600℃。随着反应物浓度的增加，获得单一ZrC涂层对应的最低ZrCl₄与CH₄的摩尔分数比增加；反应物摩尔分数的最佳范围可选为：甲烷，1.0%～2.0%；ZrCl₄，为甲烷的1.5倍。