Environmental protection is one of the key issues in the prospective policy and strategy of radiation protection. In this context, numerous efforts have been made for developing the framework for the protection of non-human species from ionizing radiation, especially in European countries and Unite States. The present report summarizes knowledge so far attained on the assessment of doses and radiation impact on marine organisms. Special attention was directed to the methodology for calculating absorbed doses of marine organisms, based on which a case study was also carried out for estimating absorbed dose rate of several species of marine organisms inhabiting in the coastal sea off Rokkasho-Mura, Aomori Prefecture where a spent nuclear fuel reprocessing plant came into operation.

View full abstract

Entrance skin dose, organ dose, and the effective dose of patients undergoing coronary angiography (CAG) and percutaneous coronary intervention (PCI) were evaluated based on the dosimetry in an anthropomorphic phantom. Tiny photodiode dosimeters embedded in various organ sites in the phantom were used to measure exposure doses. Dosimeter signals acquired on a personal computer directly were converted into absorbed doses, from which organ and the effective doses were evaluated by using the computer. Dose measurement were carried out for two types of current x-ray imager—i. e. image intensifier and flat panel detector—in fluoroscopy and in cine angiography separately for every projection of routine CAG and PCI procedure used in Nagoya Daini Red cross Hospital. Dose-area product (DAP) was also measured to examine the relations between entrance skin dose, the effective dose and the DAP. Entrance skin dose observed in PCI was in a range of 1.3-1.4Gy, the values which were less than a threshold value of 2Gy at which erythema could occur. High organ doses were observed in lung, bone surface, liver and esophagus, where the doses for lung were the highest with a value of 47mGy for CAG and 222mGy for PCI. Effective doses were evaluated to be around 10mSv for CAG, and 13-44mSv for PCI. Entrance skin dose and the effective dose were found to be independent on the types of x-ray imager, and reduced exposure doses expected for the flat panel detector could not be observed. Dose ratio of cine angiography to fluoroscopy was lower for the effective dose than for entrance skin dose. DAP to effective dose conversion coefficients were widely ranged between 0.17 and 0.52mSv/(Gy·cm²). By using the coefficient assigned for each procedure of CAG, PCI-L and PCI-R, effective doses were possible to be estimated from measured values of DAP.

View full abstract

To investigate the energy response of an optically stimulated luminescence dosemeter (OSLD) with low energy photons, OSLDs were irradiated by low energy continuous X-rays which have various energy distributions. The effective energy of the X-ray was in the range 10.0-14.5keV, and homogeneity factor was in the range 0.5-0.9. As a result, at 11.0keV, the OSLD-to-ionization chamber ratio was maintained at almost a constant level from 1.03 at a 0.5 to 1.08 at a 0.7 homogeneity factor. However, the OSLD tended to overestimate measured value with an increase of effective energy. Probably, this error can be eliminated by calculating an appropriate correction factor.

View full abstract

From 1987 through the late 1990s, thermal neutron activation measurements of materials exposed to the atomic bomb in Hiroshima appeared to show a different distance trend than estimates from dosimetry system DS86, calling into question the accuracy of DS86 and ultimately resulting in the formation of a joint US-Japan scientific working group to develop an improved system, DS02. DS02 recalculates both the source term and radiation transport using the newest methods and input data, with new estimates of explosive yield (15kt→16kt) and height of detonation (580m→600m) of the Hiroshima bomb, but no similar change in Nagasaki. DS02 developers evaluated new measurements in all previous categories and two new categories, made designed measurement inter-comparisons on split samples, and achieved a resolution of the apparent neutron discrepancy. DS02 free-in-air gamma kerma is about 10%>DS86 at distances>1km where almost all survivors were located; neutron kerma ranges from about 10%>DS86 at 1km to 15%<DS86 at 2.5km in Hiroshima, but is<DS86 by 15% or more at all distances in Nagasaki. DS02 neutrons are less energetic than DS86 overall in both cities, resulting in slightly decreased transmission factors, particularly for body self shielding of deeper organs. Shielding modules were also updated for DS02, resulting in fairly large changes in estimated shielding for some individuals but little change in averages except for the effect of Kompira-san on a large group at distances>2km in Nagasaki. Average changes in shielded kerma and representative organ doses vs. distance are reviewed, concluding with a discussion of plans to improve dosimetry implementation at the Radiation Effects Research Foundation (RERF) by using tools such as the Geographical Information System (GIS).

View full abstract