Search Results

You are looking at 1 - 10 of 17 items for

  • Author or Editor: I. Cohen x
  • All content x
Clear All Modify Search

Abstract  

The feasibility of threshold and secondary reactions as analytical alternatives for some special elements is discussed. Examples of applications, at the author's laboratory for determination of lithium, fluorine, titanium and thallium are presented. The importance of threshold reactions as interferences of capture reactions is also discussed. The pairs of elements where the interference was experimentally evaluated were calcium and titanium, scandium and titanium; manganese and iron; copper and zinc.

Restricted access

The transition economies of Eastern Europe and the former Soviet Union have implemented at the eve of the transition public measures to promote economic growth and income protection. The success of the policies is very much dependent on the availability of external finance. By calibrating for a country like Poland CGE models for 1987 and 1990 and simulating such measures it is possible to explore likely changes over these years and the effects of these measures on the sectoral and total levels of production, prices, as well as factor remuneration and use. The analysis is complemented with applications for Hungary in 1988 and 1990. The results show commonalties but also differences between the two countries in their dependence on foreign financial resources necessary for the transition.

Restricted access

Abstract  

The instrumental determination of the103Rh/n, 2n/102Rh and103Rh/n, 2n/102mRh reaction cross-sections was carried out averaged over a fission spectrum. The experimental procedure is described and the results are discussed, in comparison with previous published data.

Restricted access

Abstract  

The possibilities of reactor induced (n, p) reactions as a tool for neutron activation analysis of titanium in geological samples are discussed. The interference of calcium and scandium is experimentally evaluated. Results for Ti, Ca and Sc in GSP-1 and PCC-1 standard rocks are presented. On the basis of the experimental values, it is concluded that the47Ti(n, p)47Sc reaction is the most favourable for titanium determination.

Restricted access

Abstract  

The theoretical and practical aspects of the use of radioactive daughters originated from the decay of longer-lived radioactive mothers in parametric activation analysis, when the ratio: mother half-life to daughter half-life is less than 10, are discussed. The mother-daughter relationships: 47Ca/47Sc; 95Zr/95Nb; 140Ba/140La; 99Mo/99mTc and 115Cd/115mIn are selected as models for the study. The cases when the radionuclide of interest is formed through both direct and indirect routes are also analyzed. As illustrative example, the direct reaction and the reaction chain: 47Ti(n,p)47Sc/46Ca(n,γ)47Ca(β)47Sc are evaluated with respect to the determination of the elements involved and their reciprocal interferences.

Restricted access

Abstract  

The occurrence, in a nuclear reactor, of the reaction chain:6Li(n,t)4He;32S(t,n)34mCl has been experimentally established. Experimentation for its application to the activation analysis determination of lithium has been carried out, and a radiochemical method for separation of34mCl is presented. The sensitivity is 0.4 g for the following conditions; 15 min irradiation (thermal flux: 1.5·1013 n·cm–2·s–1); 30 min decay; 2,000 s measurement (semiconductor detector).

Restricted access

Abstract  

The co-precipitation of tungsten and molybdenum by α-benzoinoxime has been studied. Comparison of relative yields for both elements is made. Results showed coincidence and let conclude that molybdenum can be used as tracer to calculate sample to standard relative yield for tungsten. Analyses of water samples for tungsten were made and results were also presented.

Restricted access

Abstract  

A procedure is described for neutron activation analysis of chlorine in zirconium and zirconium alloys. Calculation of chlorine concentration is performed relative to zirconium concentration in the matrix in order to minimize effects of differences in irradiation and counting geometry. Principles of the method, and the results obtained are discussed.

Restricted access

Summary  

The evolution of radiochemistry at the National Atomic Energy Commission (CNEA) in Argentina is analyzed. The antecedents of the establishment, in 1998, of the Master Programme in Radiochemistry, jointly organized by CNEA and the Buenos Aires Regional Faculty of the National Technological University are revised, and the structure of the Programme is described. On the basis of the thesis works, the initial trends are discussed. Finally, the institutional results of the Programme are described.

Restricted access

Abstract  

The errors occurred when α, the parameter that accounts for the non-ideal behavior of the epithermal flux, are neglected, have been evaluated for the determination of twenty elements in biological materials, using. gold and sodium comparators, and zirconium to measure the thermal to epithermal flux ratio (f). Sodium allows the determination of 15 elements, and up to 18 elements can be determined in positions relatively well thermalized by the simultaneous use of gold and sodium comparators, in all the cases with errors ≦2%, when α is not considered. Results obtained for reference materials are presented.

Restricted access