Some effects of self-shielding of neutron flux in neutron activation analysis have been investigated. Induced specific activities in dilute samples were compared with those in solid elements irradiated under the same conditions. Two factors affecting the neutron flux were investigated: thermal neutron self-shielding and epithermal neutron self-shielding The former effect can be computed reasonably accurately, using a well-known approximation.Self shielding of epithermal neutrons cannot be calculated rigorously, so an empirical approach was used. The self-shielding effects of neutron flux were evaluated for uranium and a maximum permissible weight has been calculated by assuming that the product of the maximum permissible weight and the atom density is a function of the ratio of the resonance integral of the absorbing element to that of uranium.
A method for the systematic activation analysis of seven noble metals—ruthenium, silver, rhenium, osmium, iridium, platinum and gold—in rocks were developed and examined with radiotracers and irradiated rock samples. After the fusion of the irradiated rock sample with sodium hydroxide and sodium peroxide, 10% sodium sulfide solution is added and rhenium is extracted with pyridine-benzene mixture from 6N sodium hydroxide solution. From the hydroxide-sulfide precipitate fraction, ruthenium and osmium are distilled as tetroxides, silver is precipitated as chloride, gold is extracted with ethyl acetate, and iridium and platinum are extracted with diantipyrylmethane. Each fraction is purified and subjected to the γ-ray spectrometry. Chemical yields for the elements are more than 60%. Determination limits are given for the seven elements.
The sublimatographic separation of volatile β-diketonate complexes of fission products produced directly by the recoil atoms of fission products under exposure of a mixture of M (β-diketone) nand U3O8 on neutron, was carried out. When Fe (dpm) 3and Fe (pta) 3were used as the catcher chelates, both samples, the subli mated radioactive chelates located at the one zone, and the positions agreed with the deposited position of inactive each catcher chelate. The unclides presented in the zone were almost97Zr-97Nb, 105Ru and99Mo-99mTc. When Y (dpm) 3was used as the catcher chelates, the sublimated radioactive chelates located at the one zone, and the zone agreed with the deposited position of inactive catcher chelates, the presented nuclides in the zone were mainly97Zr-97Nb, 95Zr-95Nb, 105Ru, 103Ru, 143Ce, 141Ce, 93Y, 92Y and147Nd. In the case of Y (pta) 3, the sublimated radioactive chelates located at the two zones. The zone at higher temperature side agreed with the deposited position of inactive catcher chelates, and the nuclides presented in this zone were the same as in the case of Y (dpm) 3. On the other hand, it was observed that mainly carrier free states of97Zr-97Nb were deposited at the zone of lower temperature side.When Ni (acac) 2was used as the catcher chelates, the sublimated radioactive chelates located at the same pattern as Y (pta) 3, but the amount of deposited zones of activity was quite low. As a U3O8target was diluted with Fe (dpm) 3catcher chelates, the yield of deposited97Zr and95Zr nuclides was enhanced, to about 50%.
This experiment was to study the radiolysis of CoIII-EDTA solution in 0.8N H2SO4saturated with air by charged particles produced through6Li (n, a) 3H reaction. The experimental results show that the G (-CoIII-EDTA) decreases as the absorbed dose rate increases. For the same absorbed dose rate, the values of G (-CoIII-EDTA) are practically independent of absorbed dose. The effects of concentration and temperature are also studied.