In this paper a new method is described for estimating the age of a given radio-active fallout by a Ge (Li) γ-ray detector with high resolution. The age is calculated by this method from the two measured values of the activity of95Nb at a given time interval in the hot particles due to the 7th Chinese nuclear test explosion carried out on December 24, 1967. The results are in fairly good agreement with the actual values of the ages, and also with the estimated ones by the activity ratios of95Zr to95Nb. The expected errors for the results and the necessary measurement accuracies for the number of the atoms of95Nb and the time intervals to estimate the age within the errors 1 to 2 days, are given in the tables.
Simultaneous determination of cadmium and some other elements in unpolished rice by non-destructive and destructive activation analysis using a high resolution Ge (Li) detector was investigated. The samples were irradiated in a thermal neutron flux of 1-2×1012n⋅cm-2⋅sec-1and the irradiation times were 10 hours for long life nuclides and 10 minutes for short life nuclides, respectively. In the destructive method, column isotopic exchange technique by sodium bromide and potassium bromide mixture was tried for the removal of24Na, 42K and82Br which were the most interfering elements in activation analysis of unpolished rice. It allowed us to remove24Na, 42K and almost all82Br simultaneously. In the analysis of unpolished rice samples produced around Fuchu City, Tokyo, Cd, Cr, Zn, Sb, Mn, Na, K, Cl and Br were determined by non-destructive method and Cu, As and low content of Cd were detected only by the above-mentioned destructive method. From these results, it was found that the several samples are polluted with Cd and the other elements such as Sb, Cr and Br.
The effects of60Co-γ irradiation on benzyl thiocyanate (BTC) and benzyl isothiocyanate (BIT) have been investigated by gas chromatography and mass spectrometry. The degradation of BTC were 8.8%, 17.4% and 29.3% and those of BIT were 4.7%, 12.7% and 16.2% for the irradiation with 1.1×108rad, 2.0×108rad and 3.1×108rad, respectively. γ-Induced isomerization was observed in both BTC and BIT. In the case of 3.1×108rad irradiation isomerization yield of BIT from BTC was 8.3% and that of BTC from BIT was 1.7%, respectively. Benzene, toluene, benzyl mercaptan, benzyl cyanide, dibenzyl, dibenzyl sulfide and dibenzyl disulfide were identified and determined, among radiolysis products of BTC and BIT. On the other hand, the presence of trimer in both irradiated samples was identified by mass spectrometry.
To enlarge scintillation image, to take transmission scintiphoto, and to take X-photo exactly superimposable onto the image for its localization in relation to the internal organs, a converging collimator having 1260 holes and 56 cm focus was produced. The characteristics of the collimator in magnification, resolution, sensitivity and the effect on gamma-ray spectrum were tested with the collimator placing203Hg enclosed line and area source in air and water at various collimator to source distance. The test results were as follows; Scintillation image was recorded in detail by magnification with the converging collimator. Resolution was better than the image with parallel and diverging collimator, except pin-hole. Sensitivity was best among these collimators. With the converging collimator, count rate was highest at photopeak area, and the count rate ratio of photopeak to Compton area was largest both in air and ater.