Tracer techniques have proven to be one of the most powerful tools to characterize the movement of air mass and pollutant transport in hydrological systems. In order to clarify the behavior of low-level tritium in the rain water, we have employed the measuring method of tritium applying a distillation process and an electrolytic enrichment process. The activity of tritium (T specific activity) in the obtained water was measured by liquid scintillation counter. This procedure was applied to bulk precipitation, imitative ground infiltrated precipitation and short term precipitation collected in Niigata City. Moreover, we investigated the concentrations of cations (Na+, K+, Ca2+, and Mg2+) in the precipitation to associate with air mass transport patterns arriving at the place. From the above mentioned, next matters have been clarified:(1) T specific activity in precipitation was found to have a strong dependence on location and season. (2) The chemical components in precipitation during typhoon have notable character of marine air mass. (3) Associated ions in monthly precipitation showed seasonal variation, in fact, the seasonal variation of Ca2+ and tritium were very similar. (4) Backward trajectory analysis method is useful for the analysis of the behavior of T specific activity and several ions in short-term precipitation.
The impact of revisions of nuclear decay data on internal dose coefficients for workers was studied using revised data of ICRP Publication 107(ICRP107) and existing data of ICRP Publication 38(ICRP38). At first, two sets of ingestion dose coefficients for workers based on ICRP107 and ICRP38 were calculated using the dose and risk calculation software DCAL for 876 chemical forms of 774 nuclides. Ingestion dose coefficients based on ICRP107 increased by over 10% compared with those based on ICRP38 in 61 chemical forms, and decreased by over 10% in 28 chemical forms. It was revealed that the differences in ingestion dose coefficients mainly originated from the revision of energy data as is the case reported previously in inhalation dose coefficients. And, the revisions of the proportion of energy of electrons to that of photons, decay modes and half-lives also resulted in changes in the dose coefficients. Then, the extent and causes of changes in ingestion and inhalation dose coefficients were also compared with each other in light of our previous work concerning inhalation dose coefficients. As a result of comparing the dose coefficients for ingestion and inhalation, it was found that the change in proportion of energy of electrons to that of photons impacted on dose coefficients in ingestion more significantly than in inhalation. On the other hand, the change in shape of β energy spectrum, which was one of the causes of change in inhalation dose coefficients, did not impact on ingestion dose coefficients.
More than 100years have passed since the discovery of X-Strahlen by Roentgen. The history of radiation therapy has evolved under mutual stimulating relationships of the external beam radiation therapy by X-ray tubes and accelerators, and the internal radiation therapy employing radium and other radionuclides. The currently employed technologies in radiation therapy have its origin already till nineteen sixties and the development of physics and engineering have realized the original concept.
The radioactivity of 131I, 134Cs and 137Cs in soil, milk as well as pasture (Italian ryegrass) and well water supplied to the cows was measured. The samples were collected from Animal resource science center located at Ibaraki-prefecture, about 130km south of Fukushima nuclear power plant, 3 and 12 weeks after the accident. It was found that the radioactive nuclides included in meadow grass were promptly transferred to the milk. But the radioactivity of these nuclides were lower than the provisional government regulated value, 300 and 200Bq/kg for radioactive I and Cs, respectively.