In order to investigate in more detail on the137Csconcentration in pond sediments, we have carried out analysis on the bonding forms of137Csin pond sediments. The existing rate of different bonding forms of137Csin pond sediments was found to be below 5% for F1: exchangeable and F2: bound to carbonates, 18-24% for F3: bound to iron and manganese oxides, 14-17% for F4: bound to organic matter and 54-60% for F5: residual (mainly, bound to silicate minerals) . Furthermore, we have investigated the relations among the137Csconcentration in each place, the ignition loss, the total carbon and the cation exchange capacity of pond sediment, respectively. We have found a tendency that the larger the ignition loss, the total carbon and the cation exchange capacity are, the higher the137Csconcentration is. On the other hand, about 90% of40Kin pond sediments is in the form of F5, and the bonding forms of137Csand40Kare obviously different regardless of the fact that both are alkaline metals.
Electronic Personal Dosemeter (EPD) was examined for effectiveness in cosmic radiation dosimetry at aircraft altitude through the measurements in a Japan-US round trip. The EPD value (Hepd) of individual dose equivalent, penetrating, Hp (10), was considered to be almost equal the deep absorbed dose attributed to electrons at the aircraft altitude. By assuming the fractions and the effective quality factors for other components (muons, protons, and neutrons) based on model-calculation data, an empirical equation to estimate a conservative deep dose-equivalent at 5 cm-tissue depth, H (50), was given as H (50) =3.1×HepdEstimated H (50) values in the international flights were 4.9μSvh-1from Tokyo to New York and 3.6μSvh-1from Los Angeles to Tokyo. These values agreed well with the predicted values presented by NCRP.
A criticality accident occurred at the JCO nuclear fuel processing plant in Tokai-mura, Japan at 10 : 35am on September 30, 1999. Three workers while working nearby were exposed to high doses of radiation, especially rich in neutron. They suffered from the acute radiation syndrome and two of them were still under medical treatment. This criticality accident taught us significant lessons of radiation protection for the personneles, e.g. physicians, nurses and firemen who are expected to rescue radiation-exposed patients in radiation accidents. In this article, medical management of radiation accident, e.g. treatment of patient, with high-dosed radiation-exposure and with internal contamination of radioactive nuclides and estimation of individual radiation dose, were briefly explained. The Japanese Association for Medical Management of Radiation Accident was founded on August 29, 1997, in order to promote the mutual communication of physicians who have to be engaged in treatment of radiation-exposed patients.