Effects of secondary electron emission from a floating surface on the plasma sheath

The paper describes the region between a Maxwellian plasma source and a floating surface by a 1D-3 V fully kinetic, electrostatic particle simulation. The electric field is self-consistently computed from the Poisson equation. The secondary electron emission is modelled by considering an expression for the secondary emission coefficient dependent on the primary electron energy and surface materials and a realistic secondary electron distribution function is introduced at the collector surface. The model is able to simulate the space-charge-limited conditions as well as the positively charged wall cases.     

稳定同位素法在追踪地下水污染源中的应用

地下水是人类最洁净的饮用水源,由于其自净能力较弱,一旦受到污染,极难治理.查清污染源是地下水污染防治的前提,而稳定同位素法在判断地下水的补给来源、地下水与地表水之间的联系,以及确定各种污染水源在地下水中的混合比例方面的应用比较成熟,因此在寻找地下水污染源方面有广阔的应用前景.     

Sliding wear behaviour of ZrN and (Zr, 12 wt% Hf)N coatings

In the present study, the sliding wear resistances of ZrN and (Zr, 12 wt% Hf)N coatings deposited on a hardened AISI D2 tool steel by arc-physical vapor deposition (PVD) technique were examined by a ball-on-disc wear tester. Alloying of ZrN coating with 12 wt% Hf did not change the hardness significantly, but achieved an improvement on adhesion strength and dry sliding wear resistance against steel (AISI 52100-55HRC) and Al₂O₃ balls.     

用放射性甲基碘做示踪剂测量核通风系统除碘效率不同试验方法的比较研究

研究了硫酸二甲酯法、三甲基氯硅烷-磷酰基乙酸三甲酯法和同位素交换法在碘吸附器性能试验及核通风系统除碘效率试验中应用的优缺点。对三种方法的试验产率、试剂及残液毒性、试验可靠性及设备稳定性等方面进行了综合研究。研究结果表明:硫酸二甲酯法由于试剂毒性而在应用上受到一定限制;三甲基氯硅烷-磷酰基乙酸三甲酯法作为低毒性试验方法总体满足现场试验要求,但由于该方法所用试剂对试验设备会造成一定侵蚀,因此需要作一些改进;同位素交换法作为一种新颖的试验方法具有毒性低、产率高、操控简单稳定、风险较低等优点,推荐使用。     

同位素释放器与氧活化仪器组合测井的应用

文章介绍了同位素五参数测井和氧活化测井的测井原理，分析了它们各自的优势与不足，采用同位素释放器和氧活化仪器组合的方式，使一次下井可以同时完成同位素、氧活化两种工艺方法，为提高吸水剖面测井质量提供了新的手段。     

Measurement of Tritiated Moisture in Gas Stream by Collection Method Using P2O5 Desiccant

A measurement method of tritiated moisture in gas stream has been developed by taking advantage of the high hygroscopic and deliquescent performances of phosphorus pentoxide P₂O₅. The method includes two techniques; one is of collecting moisture from gas stream using the desiccant, the other is of preparing homogeneous liquid scintillation cocktails containing the phosphide and the collected moisture. By introducing an idea of common use of standard vials as the collector cells disposable and the scintillation cocktail containers, the treatment process has been simplified and the chances of error arising in process for subsequent tritium analysis have been decreased. From results of a typical experiment, a relationship between the collection efficiencies and the moisture contents of P₂O₅ has been obtained and the isotope effect on the moisture collection has been elucidated. The collecting performance and the isotope effect are discussed here considering the mass transport phenomena in collector cell.     

Protium removal from deuterium-tritium mixture with displacement chromatography method: Experiments and simulations

The displacement chromatography technique with a tri-column system was used to reduce the protium (H) in the deuterium-tritium (D-T) mixture, and the separation performance was studied numerically by ANSYS FLUENT. The experimental results showed that the isotopic abundance of H in the D-T mixture dropped from 2.7% to an acceptable level of 0.88%. The simulation results showed that a lower porosity (θ) of the filling material made a higher separation factor, but a lower separation efficiency. The velocity of the product gas at the outlet of the separation column approximately had a linear relationship with θ^5/3/(1-θ)², which partly indicated the pore diffusion resistance. The mixed gas could contact the filling materials more sufficiently under a lower flow rate resulting in a lower protium concentration in the product gas. The separation column with a thin and long shape had a better separation performance and a lower product gas loss.     

Asymmetric Autocatalysis Triggered by Chiral Crystals Formed from Achiral Compounds and Chiral Isotopomers

Asymmetric autocatalysis with amplification of enantiomeric excess is found in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde using pyrimidyl alkanol as an asymmetric autocatalyst. Asymmetric autocatalysis has been employed as a method for clarifying the origin of homochirality. Circularly polarized light, inorganic chiral crystals and statistical fluctuation of enantiomeric imbalance act as chiral initiators in asymmetric autocatalysis to afford highly enantioenriched products. We have investigated asymmetric autocatalysis using chiral crystals formed from achiral and racemic compounds as an origin of chirality. Absolute control of the crystal chirality of cytosine was achieved by the removal of crystal water. Enantioselective carbon-carbon bond formation at the enantiotopic crystal face of aldehydes was established using diisopropylzinc vapor. In addition, asymmetric autocatalysis triggered by chiral compounds arising from H, C and O isotope substitution has been achieved.     

Soil-to-Plant Transfer Factors of Stable Elements and Naturally Occurring Radionuclides (1) Upland Field Crops Collected in Japan

In long-term dose assessment models for radioactive waste disposal, an important exposure pathway to humans is via ingestion of contaminated foods. In order to obtain soil-to-plant transfer factors (TFs) of radionuclides under equilibrium conditions, naturally existing elements were measured as analogues of radionuclides. Crops grown in upland fields and associated soil samples were collected from 62 sampling sites throughout Japan. The total concentrations of 52 elements in the crops and 54 elements in the soil samples were measured. The TFs of 40 elements (Li, Na, Mg, Al, Si, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Y, Mo, Cd, Sn, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Pb, Th and U) were calculated on a dry weight basis.

Among all the TF data, K showed the highest TF with a geometric mean (GM) of 2.1, followed by P. The GMs of TFs for rare earth elements, Th and U were on the order of 10^?4. Most of the TF-GMs for green vegetables were higher than GMs of all crops for the elements. The obtained TFs of some elements for green vegetables and potatoes were compared with those in the technical report series-364 (TRS-364) compiled by IAEA in 1994. The TF-GMs were usually lower than the best estimates (expected values) listed in TRS-364; however, the GMs of TF for La and TF for Th observed for potatoes were slightly higher than the expected values.     

Tritium Isotope Separation by Multiphoton Dissociation of CF3CTCIF

A conception of the advanced water chemistry diagnosis system for detection of anomalies and preventive maintenance of system components is proposed. Extension of anomaly diagnosis knowledge and more reliable water chemistry data are indispensable to the advanced system. Then, correlations between water chemistry (conductivity and pH) change in reactor water and anomaly occurrence in the components of the feed water line are analyzed theoretically. These correlations are verified as applicable to extension of the diagnosis knowledge for anomalies in the components of the feed water line, such as resin intrusion, sea water Leakage at the condenser, and a breakdown in ion exchange capacity of resin at the condensate demineralizer.