Analytical results of uranium concentration in rocks and soils collected in the area of Lolodorf of South Cameroon where a radiometric anomaly had been found by previous investigation are reported. The analysis has been carried out by γ-ray spectrometry using a Ge detector. Radioactivity concentration of 235U was determined by comparing peak count rates of samples with those of natural uranium standard sample. Radioactivity concentration of 238U was calculated from the 235U radioactivity concentration by assuming that the isotopic composition of 235U is 0.7200% of natural abundance. Difference of γ-ray self-absorption between the samples and uranium standard was accurately corrected by using a mass attenuation coefficient of samples and standard measured by using an external γ-ray source. The radioactivity concentrations in rocks ranged from 0.92±0.02 to 228±14Bq/kg(235U) and 20±5 to 4868±307Bq/kg(238U), while radioactivity concentrations in soils ranged from 3±1 to 63±2 Bq/kg(235U) and 71±19 to 1346±38 Bq/kg(238U). The γ-ray dose rates in air at 1m above the ground surface due to the high uranium concentration in soil samples were ranged from 33±9 to 622±18 nGy/h. The highest uranium concentration of about 0.04% in rock was found in the analysis. These results show that the uranium content in the studied areas is significantly high and the studied areas have a potential for uranium mining.
For determining radioactivity of waste drums using γ ray measurement, we showed a new analysis method deriving the linear relation between radiation source distribution and γ ray count rate under the homogeneous waste density. On the other hand, there was a problem applying the linear relation to the case of inhomogeneous waste density. We calculate the geometric mean of measurements at various positions on spherical surface surrounding the waste drum to create the approximately homogeneous waste density. As a result, we derived the relation between radiation source distribution and γ ray count rate by 1/(ln(k/R))2 and n. R is the geometric mean of two γ ray (766keV and 1001 keV) ratios. k is the ratio of two γ ray emission rate. n is the geometric mean of γ ray (1001 keV) count rates. We calculated the several model by Monte Carlo simulation code to evaluate the validity of this method. The calculation results showed linearity between 1/(ln(k/R))2 and n.
Elementary particle physics is outlined plainly in the three-part tutorial. In this second part, gauge particles are explained such as photon, which intermediate the electromagnetic force. The essence of the gauge particles lies in their gauge symmetry hence the difference in the gauge symmetries implies varying nature of the interaction mediated by each gauge particle. The gauge particles that mediate the weak interaction and the strong interaction and their importance in elementary particle physics are explained. An important concept called “breaking of symmetry” is introduced and the significance of Higgs boson is narrated.
Recently radiotherapy is making a great advancement in the field of cancer treatment in Japan. Physical and technological achievement by concentrating radiation to tumor tissues has been a major reason for the advancement. On the other hand, biological approach has also been thought to be important. Especially, recent progress on molecular biology is providing an innovative changes in the field of radiobilogy. Many phenomenological findings accumulated in this field are going to be resolved from a view of molecular mechanisms. I will review a recent trend of radiobiology in addition to historically important events discovered in the classic radiobiology.