Authors:K. Hirose, T. Miyao, M. Aoyama, and Y. Igarashisnm>
Plutonium isotopes in the Sea of Japan were determined to assess radioactive contamination. Concentrations of 239,240Pu in surface water of the Sea of Japan were maintained at a constant level over the past two decades in contrast to 137Cs. A median value of surface 239,240Pu in the Sea of Japan in this period was 5.6 mBq/m3 with the range between 2.1 and 14.0 mBq/m3, which is slightly higher than that in the western North Pacific. The vertical distribution of 239,240Pu showed a surface minimum, a subsurface maximum and gradual decrease with increasing depth. The 241Pu/239,240Pu activity ratios in water columns were almost constant except for surface water. In regard to 239,240Pu in surface water of the Sea of Japan, these findings suggest that rapid recycling of deeper plutonium occurs in the Sea of Japan due to deep convection in winter and biogeochemical processes such as particle scavenging and remineralization.
The progress of forensic neutron activation analysis (FNAA) in Japan is described. FNAA began in 1965 and during the past 20 years many cases have been handled; these include determination of toxic materials, comparison examination of physical evidences (e.g., paints, metal fragments, plastics and inks) and drug sample differentiation. Neutron activation analysis is applied routinely to the scientific criminal investigation as one of multielement analytical techniques. This paper also discusses these routine works.
The amount of long-lived radioiodine, 129I (half-life 1.57·107 y) in the Japanese environment has been studied by measuring thyroids of humans and animals. The collected samples were thyroids of (1) humans in Ibaraki Prefecture, in Kanto district, the central part of Japan, (2) cattle in Aomori Prefecture, north part of Japan, and (3) wild deer in Chiba Prefecture, in Kanto district. The measured mean isotopic ratio 129I/127I for thyroids of cattle in Aomori Prefecture is 3.5±1.8·10-9. A higher value of 14±5·10-9 has been obtained for thyroids of wild deer in Kanto district. On the other hand, the measured ratio for human thyroids in Kanto district is 1±0.2·10-9. This value is significantly lower than that of cattle thyroids in Aomori and also those reported for human thyroids in Europe and USA. The higher mean ratio for cattle thyroid in Kanto district is possibly explained by the influence of nuclear reprocessing plant. Lower mean ratio for human thyroid might be due to higher dietary intake of algae.
Thermoanalytical studies on specialty polymers in Japan are reviewed. The basic and applied researches for the developments
of new specialty polymers such as high-performance polymers, liquid crystalline polymers, and biodegradable polymers during
the 1990's are introduced from the standpoint of thermal analysis. Many studies were performed for the improvements of durability
and thermal stability of engineering polymers, biodegradable polymers and so on. A special topic of researches on the thermal
behavior of polymers by high-pressure differential thermal analysis is included in this review.
Authors:N. Momoshima, T. Toyoshima, R. Matsushita, A. Fukuda, and K. Hibino
Elemental concentrations in Japanese medaka and mosquitofish collected from uncontaminated rivers in Kumamoto, Japan were
analyzed by instrumental neutron activation analysis with k0 standardization method to know the background levels. A statistical analysis indicated the difference in metal concentrations
among rivers and species. Background levels of elemental concentrations in some aquatic insect larvae were analyzed and metal
concentrations were different among species, though they were collected at the same point. Enrichment factors of heavy metals
in insect larvae were in the order of 103−104 suggesting effectiveness of insect larvae as bioindicator.
To satisfy the needs for industrial standards for thermal analysis in the Japanese polymer industry, round-robin tests of
differential scanning calorimetry (DSC), thermogravimetry (TG), thermomechanical analysis (TMA) and thermodilatometry (TD)
have been carried out recently. The results are discussed in this short review.
The DSC applications tested were not only for determination of transition temperature but also for measurements of the transition
heat and heat capacity. The TG task group did not aim at longterm thermal endurance studies, but relative thermal stability
in molding and estimation of filler content, residual solvent content, etc. TMA was found to be a useful tool for measuring
softening temperature and heat distortion temperature, especially for high-temperature engineering plastics, instead of the
Vicat test which has temperature limitations. For temperature calibration of DSC and TG, ICTA-NIST certified reference materials
were used together with other potential temperature standards; some inorganic substances and alloys were not found to be preferable
to pure metals. For TMA and TD metal plates were found to be very useful for temperature calibration. Analysis of the round-robin
test results also clarified present status of practical applications of thermal analysis, such as reproducibility and causes
Authors:H. Oda, T. Masuda, E. Niu, and T. Nakamura
Radiocarbon ages of 17 ancient Japanese documents of known age and 3 unknown samples were measured by AMS. Radiocarbon dating on the known documents concluded that the Japanese paper is a suitable sample for radiocarbon dating because of small discrepancy between the calibrated radiocarbon age and the historical age due to the characteristics of Japanese paper. From the dating of the paper samples of unknown age, the wood-block prints, it was clarified that they had been produced between the 11th century and the first half of the 12th century as the historical information suggested.
Although there are 430 govemment and private universities in Japan, only a limited number of them have departments associated with nuclear science education. Moreover, mainly because of financial pressures, this association is often limited to government universities. Nuclear engineering departments are incorporated with only seven of the larger universities, and there are three institutes with nuclear reactors. In these facilities, education in reactor physics, radiation measurements, electromagnetic and material sciences, are conducted. In terms of radiation safety and radiological health physics, tem radioisotope centers and seven radiochemistry laboratories in universities play an important role. Virtually all of the financial support for nuclear education comes from the Japanese Govemment via the Ministry of Education, Science, and Culture. These are supplemented via private and corporate grants to various university faculty members. In addition to these universities, and private/corporate research institutes, The Japan Atomic Energy Research Institute teaches a short lecture course in nuclear science on a regular basis.
Authors:Y. Narazaki, K. Fujitaka, S. Igarashi, Y. Ishikawa, and N. Fujinami
Seasonal variations of 7Be deposition in regions throughout Japan (26°18'N-43°05'N, 127°54'E-141°27'E) were observed during the period of 1989-1995. The observation indicated that 7Be deposition peaked in spring all over Japan except in the inland central basin. However, spring peak was not always the annual maximum. Along the coastal side of the Japan Sea, especially around Hokuriku region, 7Be deposition was at its maximum in winter. In addition, September peak also was observed in some regions, which was presumably caused by high precipitation or blowing in of northern air stream. Variations were classified into 4 types according to meteorological factors and local geographical conditions: winter peak, double peaks (spring and September peaks), spring peak and non-peak. A correlation between 7Be deposition and precipitation was observed in winter.
Concentrations of cesium isotopes and plutonium in river water samples in Japan, collected during the period from June 1985 to February 1987, have been measured. The total137Cs concentrations in the Japanese river waters ranged from 0.063 to 1.89 mBq·l–1. The portion of particulate137Cs to total was observed to be less than 10 to 35%. The total239,240Pu concentrations ranged from 0.56 to 1.93 Bq·l–1. Particulate239,240Pu occupied 13 to 95% of the total. After the Chernobyl fallout, elevated137Cs concentrations were observed in the Japanese river waters as well as the detection of134Cs, whereas there was no effect on the river plutonium from the Chernobyl fallout. The partition coefficients of137Cs and plutonium between suspended particulate and dissolved phases in the Japanese rivers were determined: from 1.0·104 to 3.2·105 and from 4.1·104 to 2.3·106 for137Cs and plutonium, respectively. The result suggests that these radionuclides, especially plutonium, are tightly associated with soil particles and/or suspended matter.