同位旋相关的Boltzmann-Langevin方程及新核素19Na产生截面的研究

介绍了一种同位旋相关的输运方程,研究了在入射能量为28.7和6 0. 0MeV/u时 12C+ 12C的反应,对模型进行检验,发现计算结果较好地符合实验结果,说明了方程的可靠性. 利用该模型研究了在入射能量为28.7MeV/u下反应系统 17 -20,22Ne+ 12C中核素 19Na的产生截面,发现缺中子核引起的反应,具有更大 19Na的产生截面,为新核素的探测找到了理论依据.     

Decay Experiments on N∼Z nuclei: The role of Masses, Q Values and Separation Energies

By using heavy-ion induced fusion-evaporation reactions at the on-line mass separator of GSI, decay properties of neutron-deficient isotopes between ⁵⁶Ni and ¹⁰⁰Sn were investigated. Recent experimental results will be presented and discussed, with particular emphasis on the role of masses, Q values and separation energies. This revised version was published online in July 2006 with corrections to the Cover Date.     

原子能院的核天体物理研究和串列升级工程进展(英文)

在北京串列实验室建立了次级束流实验装置 ,用于放射性核束物理和核天体物理研究 .先后开展了7Be(d ,n) 8B ,11C(d ,n) 12 N ,8Li(d ,p) 9Li和6 He(p ,n) 6 Li核天体物理重要反应的研究 .介绍了串列加速器升级工程的进展情况 .该工程在现有串列加速器的基础上 ,将建立 10 0MeV/ 2 0 0 μA的质子回旋加速器、在线同位素分离器和超导加速段 .在此装置上 ,将可以产生质量数最高为 12 0 ,强度最高为 10 9particles/s的放射性束流 . A secondary beam line (GIRAFFE) at the Beijing Tandem accelerator lab was constructed for yielding low energy secondary beams. The current progress on the study of nuclear astrophysics and nuclear structure is presented. Up to now, We have carried out measurement of~(7)Be(d, n)~( 8)B,~(11)C(d, n)~(12)N,~(8)Li(d, p)~(9)Li, and~(6)He(p, n)~(6)Li reactions. The proposed Beijing radioactive nuclear beam facility (BRIF ) and its current R&D progress are briefly introduced. This facility is based on...     

Penning trap mass spectrometry for nuclear structure studies

High-precision mass measurements as performed at the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN are an important contribution to the investigation of nuclear structure. Precise nuclear masses with less than 0.1 ppm relative mass uncertainty allow stringent tests of mass models and formulae that are used to predict mass values of nuclides far from the valley of stability. Furthermore, an investigation of nuclear structure effects like shell or sub-shell closures, deformations, and halos is possible. In addition to a sophisticated experimental setup for precise mass measurements, a radioactive ion-beam facility that delivers a large variety of short-lived nuclides with sufficient yield is required. An overview of the results from the mass spectrometer ISOLTRAP is given and its limits and possibilities are described.      

Recent advances in exotic nuclear beams

Not intended to be a review of the field, the present paper is the written version of a talk given at the APAC 1999 conference. It only aims at an outline of the important effort nowadays made for experiments with exotic beams. A comparatively long list of references is given where more complete information can be found. This revised version was published online in August 2006 with corrections to the Cover Date.     

Kinetics of FeSe2 oxidation by ferric iron and its reactivity compared with FeS2

The mobility and bioavailability of selenium is a major health and environmental issue and a main concern for geological disposal of high-level radioactive waste. Chemically and/or microbially mediated oxidation of insoluble Se-bearing particulate, such as iron selenides, to dissolved and mobile phases controls the transport and distribution of Se in the environment. The oxidation of ferroselite(FeSe2) by ferric iron was investigated in anoxic conditions. The redox reaction can be represented by: FeSe2 + 2Fe3+ = 2Se0 + 3Fe2+. Kinetic studies indicated that the reaction can be described by second-order rate law, with rate constants of 0.49±0.01, 0.85±0.02, 1.84±0.04, and 3.29±0.13 L mol-1 s-1 at pH 1.62, 1.87, 2.23, and 2.49, respectively. The positive correlation between reaction rate and pH implies that diffusion of Fe3+ oxidant to the mineral surface is the rate-determining step. The strong reactivity of FeSe2 towards Fe3+ suggests that ferric iron may play a significant role in FeSe2 oxidation process(e.g., by Se4+, O2, etc.) and Se0 should be the first reaction product. Also, it was shown that the reduction rate of Fe3+ or Se4+ by pyrite(FeS2) can be significantly increased in the presence of FeSe2, suggesting a stronger reactivity of FeSe2 compared with pyrite. The results obtained extend our knowledge about the subtle interaction between Se, pyrite and iron selenides in the environment, and give insight into the transfer of selenium from iron selenides to bio-available selenium(i.e., selenite and selenate) in the Se-rich environment.     

A Novel Vanadosilicate with Hexadeca‐Coordinated Cs+ Ions as a Highly Effective Cs+ Remover

The effective removal of ¹³⁷Cs⁺ ions from contaminated groundwater and seawater and from radioactive nuclear waste solutions is crucial for public health and for the continuous operation of nuclear power plants. Various ¹³⁷Cs⁺ removers have been developed, but more effective ¹³⁷Cs⁺ removers are still needed. A novel microporous vanadosilicate with mixed‐valence vanadium (V⁴⁺ and V⁵⁺) ions is now reported, which shows an excellent ability for Cs⁺ capture and immobilization from groundwater, seawater, and nuclear waste solutions. This material is superior to other known materials in terms of selectivity, capacity, and kinetics, and at very low Cs⁺ concentrations, it was found to be the most effective material for the removal of radioactive Cs⁺ ions under the test conditions. This novel vanadosilicate also contains hexadeca‐coordinated Cs⁺ ions, which corresponds to the highest coordination number ever described.     

New Calix[4]arene-monobenzo- and -dibenzo-crown-6 as Cesium Selective Ionophores in the Radioactive Waste Treatment: Synthesis, Complexation and Extraction Properties

Cesium possesses two long lived isotopes ¹³⁵Cs and ¹³⁷Cs and the first one has a very long (2.3 × 10⁶ y) half life and is one of the most mobile nuclides in a repository.Calix[4]arene-crowns-6 in the 1,3-alternate conformation areemerging as a new class of ionophores exhibiting a very high efficiency and selectivity in the complexation of cesium ion and itsremoval from highly acidic ([HNO₃] = 3–4 M) radioactive waste having also high sodium nitrate concentration ([NaNO₃] = 2–4 M). In order to improve both efficiency and cesium selectivity we have synthesised the novel calix[4]arene dibenzo-crowns-6 1 and 2 and thecalix[4]arene-monobenzocrown-6 3 in 1,3-alternate conformationand evaluated their complexation properties towards alkali metal cations in homogeneous solution and in two phase systems, togetherwith their performance in radioactive waste treatment. All data confirm the higher Cs/Na selectivity of the 1,3-alternate calix[4]crown-6 1–3 containing aromatic rings in the polyether loop, in comparison to previously synthesised compounds of the same series.     

Investigation of vertical migration of alpha-emitting nuclides in soils for southern regions of the republic of Belarus

An investigation of vertical distribution of alpha-emitting nuclides for various types of soils using solid state nuclear track detectors (SSNTD) has been carried out. As SSNTD the DNC-film was used. Experimental system for measurement of total alpha activity in the samples of soils, including devices and equipment for selection of probes, exposition, chemical etching of detectors, automated accounting of tracks has been developed. The method of determination of specific activity of alpha emitting nuclides has been created. A comparison results of measurements with the method pointed out and radiochemical method as well as x-y-spectrometry method has been carried out.     

Accelerator-driven sub-critical reactor system (ADS) for nuclear energy generation

In this talk we present an overview of accelerator-driven sub-critical reactor systems (ADS), and bring out their attractive features for the elimination of troublesome long-lived components of the spent fuel, as well as for nuclear energy generation utilizing thorium as fuel. In India, there is an interest in the programmes of development of high-energy and high-current accelerators due to the potential of ADS in utilizing the vast resources of thorium in the country for nuclear power generation. The accelerator related activities planned in this direction will be outlined.