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  • Author or Editor: D. Gawlik x
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Abstract  

The possibilities of using hafnium irradiation filters for reactor fast neutron activation analysis have been evaluated. The filter characteristics of hafnium for this application are discussed and compared with some traditional filter materials. The main advantage for hafnium is its ability to remove a great portion of the slowing down neutrons, which may enhance the sensitivity of determination via threshold reactions.

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Abstract  

With the use of the pneumatic tube system of the BER II reactor, the irradiation position of which is equipped with a movable cadmium shield, the aluminium and phosphorus levels in bone powder and in human bone biopsies were determined. The contribution of aluminium and phosphorus to the28Al activity could be separated mathematically after the samples had been irradiated with and without cadmium shielding. The sensitivity and limit of quantitative determination of the analytical procedure were determined using the addition method and the fact that the levels of each element measured was independent of the amount of the other element was proved.

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Abstract  

Boron carbide (B4C) and boron nitride (BN) irradiation filters have been constructed and used for epithermal neutron activation analysis of biological materials. The major advantage offered by these filters in this application is the substantial reduction of interfering matrix activities. Consequently some trace elements of interest can be determined instrumentally with minimum delay. The filters are particulary beneficial if utilized in short reactor irradiations for rapid analysis of biological materials.

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Abstract  

The radiation heating caused by the10B(n, )7Li-reaction in boron carbide (B4 C) neutron filters used for epithermal neutron activation analysis has been examined by measuring rates of temperature rise and steady-state temperatures of sintered and powdered B4C filters placed in dry air and reactor pool-water during irradiation, respectively. Maximum equilibrium temperatures of 195°C for air-cooled sintered, and 50°C for water-cooled powdered B4C were observed, confirming the necessity for efficient cooling of the filter during irradiation. It is noted that the accumulation of the10B(n, )7Li-reaction products in B4C and other boron compounds may severely limit the reuse of the filters in subsequent irradiations.

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Abstract  

The suitability of graphite of spectral quality as a sample container in short irradiations for neutron activation analysis has been investigated. The material is found to be a viable alternative to polyethylene containers especially in high flux irradiation positions where the properties of the latter deteriorate as a result of high neutron and gamma dose rates. Examples of application are demonstrated in epithermal neutron irradiations of biological materials and the accuracy and precision of the determinations were assessed.

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Abstract  

A new application of neutron transmutation doping is described. The method is useful to prepare graded zinc contents in highly pure copper materials. The research reactor BER II at the Hahn-Meitner-Institute, Berlin served as a neutron source. The zinc content produced in the samples was analyzed by determining the 65Zn-activity via gamma-spectrometry. Simultaneously irradiated flux monitors were used to determine the neutron flux density. Since cylindrical sample geometries are favorable for a reference material application in optical emission (OE) spectroscopy, the spatial distribution of the induced activity in a cylinder with a diameter of 8 mm and a length of 35 mm was investigated.

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Abstract  

Trace elements and major constituents are analyzed in solid biological material and body fluids in order to compare the range of application of instrumental neutron activation analysis and plasma emission spectroscopic techniques. It is demonstrated that both methods should be regarded as complementary analytical techniques. In separate or sequential combination of both techniques the elemental coverage in the analysis of biological material is extended.

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Abstract  

Over the past few years an irradiation and measuring system has been developed for the reactor BER II at the Hahn-Meitner-Institut. It was to be suited in particular to the neutron activation analysis of biological material via short lived radionuclides. The general characteristics of this equipment and some experimental details as the recycling facility and the device used for measuring the irradiation time, the waiting time and the neutron fluence are described. This equipment was used to determine physiological concentrations of the elements sodium, chlorine, aluminium, phosphorus, fluorine, calcium, copper and selenium in biological material. The results have been compared with those obtained by photon activation analysis or ion sensitive electrode. We report on the clinical analysis of Ca, F, P and Al in the control of the treatment of osteoporosis patients and of patients undergoing haemodialysis over long periods as an example of the application of the apparatus.

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Abstract  

We have developed an irradiation facility by means of which samples can be irradiated near the core edge of the reactor BER II in liquid nitrogen at a thermal-neutron flux of 1.5.1013 n·cm–2·s–1 for a maximum of 14 days. We present the technique of neutron activation analysis in which biological samples enclosed in thin-walled quartz ampoules are irradiated and measured directly without pretreatment. Using this method, losses of iron, zinc and selenium during pretreatment procedures (freeze-drying and oven-drying at 30, 60, and 90°C) for the analysis of plasma, erythrocytes and liver were studied.

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Abstract  

Instrumental neutron activation analysis and flameless atomic absorption spectrometry have been used to study the occurence and distribution with a maximum of 25 elements in multiple sites of a skeleton and in the iliac crest of 69 ancient human skeletons. To study the distribution of trace elements between the different bone fractions the material of each sampling site was chemically treated to separate the collagen and the mineral from one another. Losses or contamination during the extraction procedure have been controled in detail by balance calculations. The elements can be subdivided into several groups due to the balance calculation and their association with the mineral. The analysis of the skeleton showed that the trace elements are distributed in varying degrees within a bone and throughout the skeleton their variation seems to be related to functional and structural conditions of the sampling site. The element content was observed to be higher at epiphyseal areas of long bones than in the shaft and higher in trabecular than in cortical bones. It was found that the element content of a single bone sample depends largely on the mass ratio spongiosa/compacta at the sampling site. By investigating an ancient population group, information about the “natural levels” and biological variation of trace elements was obtained. The results for F, Pb, Sr, and Zn in particular suggest that these elements could be useful in the study of health problems in man which involves the bone tissue.

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