Absolute determination of 79Se/80Se with AMS

Selenium-79 measurement with accelerator mass spectrometry (AMS) is increasingly being used for the determinations of ⁷⁹Se relevant nuclear data. Furthermore, ⁷⁹Se was deemed to be an ideal tracer nuclide for long-period and non-intrusive biological studies on selenium. An ultra-sensitive AMS measurement method of ⁷⁹Se has been established at the CIAE-AMS system. For further applications of ⁷⁹Se-AMS, reference standards were requested. ⁷⁹Se can be derived from the ⁷⁸Se(n, γ)⁷⁹Se reaction but cannot be accurately quantified by theoretical calculation owing to the small and dubious cross section and other relevant parameters. In this paper, an AMS method has been developed for the absolute determination of the ⁷⁹Se/⁸⁰Se ratio in a ⁷⁹Se sample with relatively high ⁷⁹Se content. The relative standard uncertainty of ⁷⁹Se/⁸⁰Se ratio is 4.7% and a reference standard is thus acquired. The results are favourable for further applications of ⁷⁹Se-AMS.     

中国原子能科学研究院的PX-AMS系统及其应用(英文)

加速器质谱(AMS)中的入射离子X射线方法是为解决AMS测量中重核同量异位素而发展的一种方法(PX AMS),在中国原子能科学研究院建立了PX AMS方法之后,利用这套系统开展了79Se,75Se,64Cu等核素的PX AMS方法测量,基于此技术实现了79Se,75Se半衰期的测量和64Cu放射性核束强度及库仑激发截面的测量。     

Nuclear data sheets for A = 79

The 1975 version of Nuclear Data Sheets (75Ur03) has been revised. Nuclear spectroscopic information for known nuclides of mass number 79 (Zn, Ga, Ge, As, Se, Br, Kr, Rb, Sr) has been evaluated and presented together with adopted level energies, level Jπ's and γ-rays in these nuclei. No data are yet available for excited states in ⁷⁹Zn and ⁷⁹Ga.     

Actinides AMS at CIRCE in Caserta (Italy)

The operation of Nuclear Power Plants and atmospheric tests of nuclear weapons performed in the past, together with production, transport and reprocessing of nuclear fuel, lead to the release into the environment of a wide range of radioactive nuclides, such as uranium, plutonium, fission and activation products. These nuclides are present in the environment at ultra trace levels. Their detection requires sensitive techniques like AMS (Accelerator Mass Spectrometry). In order to perform isotopic ratio measurements of the longer-lived actinides, e.g., of ²³⁶U relative to the primary ²³⁸U and various Pu isotopes relative to ²³⁹Pu, an upgrade of the CIRCE accelerator (Center for Isotopic Research on Cultural and Environmental Heritage) in Caserta, Italy, is underway. In this paper we report on the results of simulations aiming to define the best ion optics and to understand the origin of possible measurement background. The design of a high resolution TOF-E (Time of Flight-Energy) detector system is described, which will be used to identify the rare isotopes among interfering background signals.     

Nuclear Data Sheets for A = 65

The evaluators present in this publication spectroscopic data and level schemes from radioactive decay and nuclear reactions studies for all isobars with mass number A=65. Not much is known experimentally about ⁶⁵V and ⁶⁵Cr, although they are expected to decay by β-emission. Spin/parity assignments for ⁶⁵Mn, ⁶⁵Fe, ⁶⁵As, and ⁶⁵Se are not firmly established.     

Measurement of 79Se by accelerator mass spectrometry using projectile X-ray technique

1IntroductionInacceleratormassspectrometry(AMS)measurementsoflong-livedradioisotopes,stableisobarsarethedominantbackground.FortheradioisotopesofatomicnumberZ520,theisobarsbackgroundcanbeeliminatedbymeansofthedifferentenergylossofisobarinmatterduetotherateofenergylossisafunctionofZ.Butwithincreasingatomicnumber,theenergystragglingincreasesrelativetotheenergylossdifference,sothatisobarseparationbecomesprogressivelylesseffective.Inordertoseparatetheisobarswithhigheratomicnumberstheionenergyhast…     

Manganese-53: Development of the AMS technique for exposure-age dating applications

The cosmogenic isotope ⁵³Mn is produced by spallation of iron in surface rocks. The long half life of this isotope makes it attractive for use in erosion rate studies in slowly eroding landscapes such as Australia. We describe the development of AMS methods for detection of ⁵³Mn using the 14UD accelerator at the Australian National University. The first step of this development involved the production of ⁵³Mn using a heavy-ion fusion–evaporation reaction to make test standards. Then, the chemistry protocol for isolating ⁵³Mn and reducing the Cr levels, of which ⁵³Cr is a serious interfering isobar, was developed. Lastly we employed a gas-filled magnet which was used to discriminate ⁵³Mn from the intense ⁵³Cr background.     

Si AMS measurement with ΔE-Q3D method

Accelerator mass spectrometry (AMS) is one of the most promising methods for the measurement of trace amount of ³²Si for its advantages of small sample size, short measurement time and extremely high sensitivity. However, the isobaric interference from ³²S often badly hinders the AMS measurement of ³²Si. The ΔE-Q3D detection technique established in this work brought about an overall suppression factor of larger than 10¹² for ³²S. As a result, a sensitivity of better than 1 × 10⁻¹⁴ (³²Si/Si) has been achieved, based on the measurement of a blank sample.     

First results from the nuclear astrophysics AMS program at the NSL using the MANTIS system in gas-filled mode

The Magnet for Astrophysical Nucleosynthesis studies Through Isobar Separation (MANTIS) system is the new Accelerator Mass Spectrometry (AMS) set-up created during recent upgrades of the Browne-Buechner spectrograph at the University of Notre Dame. Commissioning measurements performed on the separation of ⁵⁸Fe-⁵⁸Ni isobars at 114 MeV out of the FN tandem accelerator have shown clear separation, opening the door for a number of future measurements in nuclear astrophysics. The separation of mass-58 isobars has made this system the first in the world to utilise a Browne-Buechner spectrograph in gas-filled mode for AMS measurements with a special focus on nuclear astrophysics.     

Simulation of experimental spectra for medium-heavy nuclides in accelerator mass spectrometry

Some interferences are often encountered in accelerator mass spectrometry （AMS） measurements, especially for medium-heavy nuclide measurement, It is difficult for online discrimination of the nuclide of interest from the interfering ones. In order to solve this problem, we developed a method to simulate the experimental spectra of medium-heavy nuclides in AMS measurements. The results obtained from this method are in good agreement with experimental values.     

Highly sensitive AMS measurements of 53Mn

Our AMS system, with the gas-filled detector system GAMS, has been optimized for measurements with ⁵³Mn. A high sensitivity has been achieved. A newly installed cesium sputter ion source yields an improved emittance, and thus a higher mass resolution. By the extraction of the manganese molecule MnF^? instead of MnO^? we can suppress the isobaric chromium background in the ion source by more than a factor of three. The GAMS system achieves an isobaric suppression factor of about 3 × 10⁸. Measurements on blank samples yielded upper limits for the ⁵³Mn/⁵⁵Mn ratios of 7 × 10^?15.     

Feasibility of Fast Fission System Confining Long-Lived Nuclides

The feasibility of fast fission system confining long-lived nuclides without other supporting system as synergetics for fuel sustainment and waste incineration was studied from the aspects of nuclear material balance and neutron economy. The continuous utilization of fast fission system which confines all actinides in the reactor but discharges all FP will lead to huge accumulation of radioactive wastes such as ¹²⁹I, ¹³⁵Cs, ¹⁰⁷Pd, ⁹³Zr, ⁹⁹Tc, ¹²⁶Sn and ⁷⁹Se in the far future. Then we studied the feasibility of the system that these long-lived seven FP are also confined in the reactor with actinides. In this scheme, all the long-lived nuclides to be disposed of were exposed with neutrons in the reactor and removed as different nuclides after nuclear transmutation. As the wastes stored in the repository was composed of only shorter-lived nuclides, total amount of radioactive wastes in the repository was suppressed to be less than a few tons per 3 GWt reactor.     

Basis for developing samarium AMS for fuel cycle analysis

Modeling of nuclear reactor fuel burnup indicates that the production of samarium isotopes can vary significantly with reactor type and fuel cycle. The isotopic concentrations of ¹⁴⁶Sm, ¹⁴⁹Sm, and ¹⁵¹Sm are potential signatures of fuel reprocessing, if analytical techniques can overcome the inherent challenges of lanthanide chemistry, isobaric interferences, and mass/charge interferences. We review the current limitations in measurement of the target samarium isotopes and describe potential approaches for developing Sm-AMS. AMS sample form and preparation chemistry will be discussed as well as possible spectrometer operating conditions.     

79Se的AMS测量方法研究

测定⁷⁹Se时由于⁷⁹Se尚无标准样品,需要建立⁷⁹Se/Se（⁷⁹Se、Se原子个数比,余同）的AMS测量方法。在⁷⁹Se/Se的绝对测定中,为尽可能避免测量Se的同位素之间的差异,通常利用探测器测量⁷⁹Se离子,本文用法拉第筒对⁷⁸Se和⁸⁰Se进行测量,但这造成两个测量系统之间的系统误差。为避免这种系统误差,利用同一探测器测定⁷⁹Se、⁷⁸Se和⁸⁰Se。考虑到⁷⁸Se和⁸⁰Se的计数率非常高,在CIAE-AMS系统中的静电分析器前和靶室内安装衰减片以降低⁷⁸Se和⁸⁰Se的计数率。实验结果表明：通过两个衰减片的衰减作用,能将⁷⁸Se和⁸⁰Se的束流降低到半导体探测器的检测范围内,实现了样品中⁷⁹Se/Se的绝对测定,得到⁷⁹Se/Se为(2.08±0.10)×10^-7,为准确测定⁷⁹Se半衰期奠定了基础。     

A method for analysis and profiling of boron,carbon and oxygen impurities in semiconductor wafers by recoil atoms in heavy ion beams

A method based on identification of recoil atoms in heavy ion beams, by using a (ΔE, E) measuring system, is described. The two parameter (ΔE, E) spectra, obtained with the aid of a computer, shows a good separation between carbon and oxygen recoils originating from a 300 μ;m thick silicon wafer bombarded with a 70 MeV sulphur beam. Profiling depths 10–20 μm and sensitivities close to 10¹⁶ atoms/cm are estimated.     

Nuclear Data Sheets for A = 80

Nuclear spectroscopic information for known nuclides of mass number 80 (Zn, Ga, Ge, As, Se, Br, Kr, Rb, Sr, Y) have been evaluated and presented together with adopted energies and Jπ of levels in these nuclei. No data are yet available for excited states in ⁸⁰Zn, ⁸⁰Ga and ⁸⁰Y.     

Nuclear data sheets for A = 79

The 1966 version of Nuclear Data Sheets for A = 79 has been revised on the basis of experimental data received prior to December 1, 1974. Information from approximately 85 papers and communications has been included in the present evaluation.Data on eight A = 79 nuclei are presented. The half-life and decay energy for ⁷⁹Ga have been proposed, but the compilers do not regard the nuclidic assignment as firmly established. The existence of two isomers in ⁷⁹Ge has recently been proposed. The compilers tentatively assign a 42-s activity to the ⁷⁹Ge ground state, and a partial decay scheme is given. The compilers do not regard the assignment of a 19.1-s activity to ⁷⁹Ge as firmly established. The spin of the ⁷⁹As ground state is known from its decay to levels in ⁷⁹Se. Many levels from ⁷⁹Se are known from ⁷⁹As decay, single-nucleon transfer, and a level scheme for ⁷⁸Se(th n,γ) proposed by the compilers. Only an upper limit for the half-life of long-lived ⁷⁹Se has been determined; this nucleus decays directly to the ⁷⁹Br ground state. Levels in stable ⁷⁹Br up to 2 MeV are known from ⁷⁹Kr decay, Coulomb excitation and resonance fluorescence, and (n,n′γ). Most of the information on excited levels in ⁷⁹Kr is regarded by the compilers as tentative, since the ⁷⁹Rb decay scheme is not well established and all reaction studies are unpublished. Only the ground state of ⁷⁹Rb is known, and its spin cannot be determined since the intensity of the decay to the ⁷⁹Kr ground state is not accurately known. The compilers tentatively assign as 8.1-m activity to the ⁷⁹Sr ground state, but no decay scheme has been proposed. The compilers regard the assignment of a 4.4-m activity to ⁷⁹Sr as not firmly established. The only data on excited levels of ⁷⁹Sr are unpublished.     

Nuclear Data Sheets for A = 71

The evaluated spectroscopic data are presented for experimentally known nuclides of mass 71 (Mn,Fe,Co,Ni,Cu,Zn,Ga,Ge,As,Se,Br,Kr). Excited-state data are nonexistent for ⁷¹Mn, ⁷¹Fe, ⁷¹Co and ⁷¹Kr. Significant new data have been added since the last evaluation of A=71 nuclides by M. Bhat (1993Bh02). Excited states are now known in ⁷¹Ni and ⁷¹Cu, and enhanced information about high-spin excitations is available for ⁷¹Ga, ⁷¹As and ⁷¹Br. The decay schemes of radioactive isotopes ⁷¹Mn and ⁷¹Fe are not known at all, and those for ⁷¹Co, ^71mNi and ⁷¹Kr are not known well. For the decay of ⁷¹Cu, ^71gNi, and ⁷¹Br, extensive data are available, but in the opinion of the evaluators the decay schemes still seem incomplete.This work supersedes earlier full evaluations of A=71 published by 1988Bh01, 1979Ke06 and 1973Al33, and the last one published in ‘update’ mode by 1993Bh02.     

Radiochemical analysis of rubble and trees collected from Fukushima Daiichi Nuclear Power Station

To characterize the rubble and trees contaminated by radionuclides released by the recent accident at the Fukushima Daiichi Nuclear Power Station, the radiochemical analysis protocols were modified using those developed by the Japan Atomic Energy Agency for the waste generated by research, industrial, and medical facilities. The radioactivity concentrations of gamma-ray-emitting nuclides ⁶⁰Co, ⁹⁴Nb, ¹⁵²Eu, and ¹⁵⁴Eu, and beta-particle-emitting nuclides ¹⁴C, ¹²⁹I, ³⁶Cl, ⁷⁹Se, and ⁹⁹Tc were successfully applied by the modified analytical method. In contrast, the radioactivity concentrations of ³H, ⁹⁰Sr, ¹³⁷Cs, and alpha-particle-emitting nuclides were applied by the conventional method. Unfortunately, ³⁶Cl, ⁹⁴Nb, ¹²⁹I, ¹⁵²Eu, ¹⁵⁴Eu, and alpha-particle-emitting nuclides were below the detection limit of the conventional method. The measured radioactivity concentrations, except for that of ³H, were not uniform in the area but depended on the reactor unit. Although the radioactivity concentrations were varied widely, this analysis successfully clarified the characteristics of the radioactivity concentrations of the rubble and trees.     

Determination of the detection limit of Ni at the Lund AMS facility by using characteristic projectile X-rays

Accelerator mass spectrometry (AMS) is an ultra-sensitive method for counting atoms, both radionuclides and stable nuclides. When using small tandem accelerators to measure heavy isotopes, interfering isobars are often troublesome. One way to reduce this interference is to combine AMS with the detection of characteristic X-rays of the projectile. After analysis in the AMS system it is possible to identify ions of different atomic number by their characteristic X-rays, by slowing down the ions in a suitable target. In this paper, the detection limit of ⁵⁹Ni at the Lund AMS facility is reported. A method for the chemical extraction of nickel from stainless steel, combined with a purification step to reduce the cobalt content in the sample by several orders of magnitude, is also described.