A small and compact AMS facility for tritium depth profiling

Depth profiling measurements of tritium in carbon samples have been performed during the past seven years at the AMS facility installed at the Rossendorf 3 MV Tandetron. The samples have been cut from the inner walls of the fusion experiments ASDEX-upgrade/Garching and JET/Culham. The tritium content of the samples from JET required a dedicated AMS facility to prevent any contamination of the versatile 3 MV Tandetron. On the basis of an air-insulated 100 kV tandem accelerator equipped with a gas stripper an AMS facility exclusively devoted to tritium depth profiling was installed, tested and used for routine measurements. After additional successful tests employing diamond-like carbon (DLC) stripper foils at this accelerator, another small and compact 100 kV tandem accelerator with SF₆ insulation and a DLC stripper has been installed at the AMS facility. Results obtained with the different tandem accelerators are presented.     

基于运行反馈的压水堆氚排放量研究北大核心CSCD

以压水堆核电厂中氚的产生机理和氚源项计算模型为基础,结合对国内外大量压水堆核电厂的氚排放运行数据的系统性分析,识别出冷却剂硼酸活化和次级中子源活化是压水堆氚排放量的主要来源,其中对中国广核集团运行机组,锑铍中子活化后的产氚量对氚年排放量的贡献可达到40%,而氚从完整的锆合金包壳的燃料棒中的释放是可以忽略不计的。由于优化次级中子源是降低压水堆氚排放量的唯一有效措施,通过分析建议压水堆核电厂采用双层不锈钢包壳的次级中子源或者取消次级中子源以降低压水堆氚排放。     

Seasonal and Annual Tritium Variations in Belgrade Natural Waters

Characteristics of seasonal and annual variations of tritium concentration completed with hydrological long-term data from 1976–1989 for the Belgrade alluvial aquifer are presented. The highest tritium concentration in precipitation of an average year appears at the beginning of summer with a maximum in June (9 Bq/l) when the amount of precipitation is also high (102 l/m²). The quantity of tritium precipitating in this area was also the largest in the summer, especially in June (922 Bq/M²). Similar variations of tritium concentration was found in the waters of the Danube and the Sava with maxima 11.3 Bq/l (July) and 9 Bq/l (June) respectively. Tritium concentrations orginated from snowmelt influence to the occurrence of higher values during that period which is more distinct in the Sava. The groundwaters and particularly ones in the Ranney wells follow changes of levels, temperature and tritium content in the alluvial of Sava with a time lag from a few days to a month. During the period of observation tritium content was decreasing in all studied waters. The decrease was faster in precipitation (11.2 to 3.0 Bq/l) and the Sava and Renney wells (10.6 to 3.0 Bq/l) than in the Danube (13.1 to 5.2 Bq/l).     

A Concept and Isotope Method for Groundwater Vulnerability Assessment

Early assessment of groundwater vulnerability during groundwater exploration is an important precondition for effective protection. Any attempt to assess the “vulnerability” is confronted with the very different factors influencing this property. In this paper we present a new concept to combine different factors on an objective basis. A protection index γ is defined and it is shown that this index can be obtained by the additative combination of a self-cleaning index (γ_s), a retardation index (γ_R) and a dilution index (γ_v). For the estimation of the latter one, isotope techniques are suitable. With lumped-parameter models, easy formulae are derived for the calculation of γ_v from tritium data. The applicability of this approach was tested with data from two field studies. The results obtained show that a reasonable assessment of groundwater vulnerability can be achieved. However, a lot of problems and questions remains to be solved by further investigation.     

Isotope and Trace Gas Analyses as Tools to Assess Water Protection Zones in a Rural Area

Abstract

An example is presented for the application of groundwater age dating by tritium and chlorofluorocarbon (CFC) measurements to assess water protection zones. The investigation area is located in a rural area close to Osnabrück (Lower Saxony, Germany). Samples from 13 drinking water supply wells were collected in November 1995.

By using an exponential model, groundwater residence times were calculated for the wells. The tritium and CFC data showed comparable residence times with slightly higher values derived from the CFCs (especially F113). Most of the wells showed residence times around or below 10 years indicating a rather high vulnerability with respect to anthropogenic contaminations.     

Zur Reindarstellung von tritiummarkierten Pyrimidinderivaten 3. Mitteilung: Darstellung von 5-Brom-[6-3H]uracil und [6-3H]Uracil

Das Phanomen der Lyolumineszenz wurde erstmuls 1895 von Wiedemann und Schmidt an Alkalihalogeniden nach Bestrahlung mit Katodenstrahlcn beobachtet. In ihrer Arbeit “Uber Luminescenz", die in den ”Annalen der Physik und Chemie" erschien, schreiben sie [24]:

“Ferner haben wir eine weitero Art der Luminescenz aufgefunden, welche man mit dem Namen Lyoluininescenz belegen konnto. In gewissen Fallen tritt beim Losen von Substanzen eine Lichtentwicklung auf, nnchdem sie vorher bestrablt worden sind, wahrend sie eine solche ohne Bestrahlung nicht zeigen“.     

Ultra low-level tritium measurement using electrolytic enrichment and LSC†

We describe an advanced methodology for low-level tritium measurement in regard to calibration, electrolytic tritium enrichment, liquid scintillation counting (LSC) measurement, and prevention of sample contamination. Details are given on enrichment parameters and electrode processes for optimisation of enrichment reproducibility and on optimisation of LSC stability. Intercomparison results demonstrate high accuracy of the tritium measurement system. The use of accurate tritium data for groundwater dating in the southern hemisphere is demonstrated with data from several groundwater systems of New Zealand.     

Wasserstoff-Tritium-Austausch im dynamischen Impulsregime an Oberflächenhydroxylgruppen des Systems Pt/Al2O3

Es gilt als gesichert, daß die Brönsted-Acidität von Al₂O₃-Trägertnaterialien die Aktivität der Katalysatoren des Typs Pt/Al₂O₃ beeinflußt. Es wird eine H₂-T₂-Austauschmethode zur Erfassung der Oberflächenhydroxylgruppen von Al₂O₃-Trägern und Pt-Trägerkatalysatoren beschrieben, deren Ergebnisse eine Charahterisierung der Brönsted-Acidität der untersuchten Katalysatoren ermöglicht. Der Isotopenaustausch erfolgt im Inertgasslrom bei impulsförmiger Dosierung des Tritiumgases. Zur Tritiummessung dient ein Proportionalgasdurchflußzählrohr.

Die Interpretation und Wertung der erzielten Ergebnisse wird abschließend an ausgewählten Beispiclen vorgenommen.     

Eine Gaszählrohr-Apparatur zum Nachweis von Tritium

Für die Bestimmung von tritiummarkiertem Wasserstoff wird eine Gaszählrohr-Apparatur beschrieben, die aus einer Vakuumanlage und einer Antikoinzidenz-Zähleinrichtung besteht. Mit der vorgestellten Anlage können bei einer spezifischen ³H-Aktivität der Lösung von A₈ = 25 mCi/ml 1,5 · 10^?11 mol Wasserstoff nachgewiesen werden. Die Anlage läβt sich auβer füH^* ₂ und andere tritiumhaltige Verindungen auch zur Untersuchung von ¹⁴C- bzw. ³⁵S-markierten Gasen einsetzen.     

Tritium and helium analyses in thin films by enhanced proton backscattering

In order to study how to reliably perform quantitative tritium and helium analyses in thin film samples using enhanced proton backscattering(EPBS),several EPBS spectra for some samples consisting of non-RBS light elements(i.e.,T,4He,12C,16O,natSi),medium and heavy elements have been measured and analyzed using analytical SIMNRA and Monte Carlo-based CORTEO codes.The non-RBS cross sections needed in the CORTEO code are taken from the ENDF/B-Ⅶ.1 database and the calculations of SigmaCalc code and are incorporated into the CORTEO code.All non-RBS cross section data over the entire proton incident energy-scattering angle plane are obtained by interpolation.It is quantitatively observed that in EPBS analysis the multiple and plural scattering effects have little impact on the energy spectra for light elements and the RBS cross sections of light elements can be used in the SIMNRA code for dual scattering calculations.It is also observed that the results given by the CORTEO code are higher than the results of the SIMNRA code in the low energy part of EPBS spectra,and are in better agreement with the experimental data.Tritium and helium analyses in thin film samples using EPBS can be performed reliably when the multiple and plural scattering contributions are completely accounted.