Activation analysis radionuclide formation

In 14 MeV neutron activation analysis the four principal nuclear reactions leading to the formation of indicator radionuclides are as follows ... 

There are two ways to produce a pure radionuclide not contaminated with any other radioactivity. An extremely pure target can be used with a reaction path which is unique. Alternatively, the radioactive products can be purified after the end of the bombardment. For example, a 10 g sample of zinc irradiated for one week with 10 n cm s yields a sample of Zn (ti 244 d) with 7.1 X 10 Bq. If, however, the zinc target is contaminated with 0.1% of copper, in addition to the zinc activity, 3.0 x 10 Bq of Cu (ti 12.7 h) is formed. In another example element 102 believed to be discovered initially in a bombardment of a target of curium by carbon ions. The observed activity, however, was later found to be due to products formed due to the small amount of lead inq)urity in the target. Similarly, in neutron activation of samarium it must be very free of europium contamination because of the larger europium reaction cross-sections. Handbooks of activation analysis oftra contain information on the formation of interfering activities from impurities. 

The production of a radionuclide becomes the basis of activation analysis methodology. In effect, a radioisotope is formed when the nuclei of any stable isotope is exposed to a source of neutrons or any other particle. The thermal neutron reaction upon Na-23 can be used to illustrate this mode of formation ... 

Neutron activation analysis Thermal neutron activation of Cr leads to two radionuclides of which the short-lived radionuclide Cr has a low abundance compared to the parent isotope (2.36%), a relatively small cross-section for formation (0.36 barn), and, most significantly, it is almost a pure S-emitter and emits very few y-rays (0.043%). The lower limit of detection using this radionuclide is very high and measurement of chromium by neutron activation analysis (NAA) is carried out using the long-lived radionuclide Cr. The half-life of Cr is within a range of 27.8 days, allowing sufficient time for sample manipulations. 

Basically, the I content in the purified iodine fraction can be measured by different techniques. Due to the low specific activity of this long-lived radionuclide, direct 3 , y and X-ray measurement techniques show only a moderate detection capability better detection limits can be obtained by determination of the I mass present in the sample. Here, laser-induced fluorescence spectrometry offers in principle favorable results however, when this technique is applied, the difficulties associated with the preparation of the h chemical species at very low iodine concentrations have to be taken into consideration. The most sensitive I determination technique is neutron activation analysis, which leads to the formation of the... 

The sample being analyzed in this experiment contains fissionable material that had been sealed in a quartz tube and irradiated with neutrons. The material was dissolved in strong mineral acid to prepare it for radiochemical analysis of fission products. You will be informed of the date and time of the end of bombardment (EOB), the type of material, the amount of fissionable material in your sample, and the acid type and strength. You can assume that the person who prepared the sample based the amount of fissile material to be irradiated and the period of irradiation on the available neutron flux and the desired amounts of fission product radionuclides. You should estimate the activities of the major fission products that remain after the time interval between formation and analysis. 

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