[en] This paper provides the update of the reference dose distribution proposed by G.A.M. Web and D. Beninson in Annex E to the UNSCEAR 1977 Report. To demonstrate compliance with regulatory obligations regarding doses to individuals, they defined it with the following properties: 1) The distribution of annual doses is log-normal; 2) The mean of the annual dose distribution is 5 m Gy (10% of the ICRP 1977 dose limit); 3) The proportion of workers exceeding 50 m Gy is 0.1%. The concept of the reference dose distribution is still important to understand the inherent variation of individual doses to workers controlled by source-related and individual-related efforts of best dose reduction. In the commercial nuclear power plant, the dose distribution becomes the more apart from the log-normal due to the stronger ALARA efforts and the revised dose limits. The monitored workers show about 1 m Sv of annual mean and far less than 0.1% of workers above 20 m Sv. The updated models of dose distribution consist of log-normal (no feedback on dose X) ln(X)∼N(μ,σ²), hybrid log-normal (feedback on higher X by ρ) hyb(ρX)=ρX+ln(ρX)∼N(μ,σ²), hybrid S_B (feedback on higher dose quotient X/(D-X) not close to D by ρ) hyb[ρX/(D.X)]∼N(μ,σ²) and Johnson's S_B (limit to D) ln[X/(D-X)]∼N(μ,σ²). These models afford interpreting the degree of dose control including dose constraint/limit to the reference distribution. Some of distributions are examined to characterize the variation of doses to members of the public with uncertainty. (author)

[en] A statistical reappraisal of models is presented for the prediction of resuspension with the assessment of uncertainty, using the historical data reported by Maxwell and Anspaugh (2011). A model, conveniently called 'hybrid scale model', was applied to unify the power law and the exponential function, which are often used in conventional predictive models of resuspension factor (S_f), and also to reflect the bounded data of S_f. The hybrid scale model has been proven to be well fitted to the data of resuspension factor with the improved assessment of uncertainty as a linearized model between observation time and resuspension factor. (author)

[en] This paper presents a feasible analysis of the distribution of doses to residents evacuated after the Fukushima NPP accident. Data for analysis are obtained from the reports of the Fukushima Health Management Survey. The hybrid lognormal distribution, which is a skewed lognormal including the parameter of protection feedback, best describes the dose distribution. The distribution of doses to residents in Fukushima Prefecture is also provided for comparison with that of the evacuated residents; this comparison is made by examining the dose distributions based on the monitoring data obtained for Fukushima. The paper also shows a method for improving data homogeneity in the relevant analysis. (author)

[en] This paper presents a feasible analysis of the distribution of doses to residents evacuated after the Fukushima NPP accident. Data for analysis are obtained from the reports of the Fukushima Health Management Survey. The hybrid lognormal distribution, which is a skewed lognormal including the parameter of protection feedback, best describes the dose distribution. The distribution of doses to residents in Fukushima Prefecture is also provided for comparison with that of the evacuated residents; this comparison is made by examining the dose distributions based on the monitoring data obtained for Fukushima. The paper also shows a method for improving data homogeneity in the relevant analysis. (author)

[en] A new type of hybrid distribution proposed by Uppuluri in 1986 was reviewed and studied on some features of the distribution and applied to actual data for the purpose of health risk assessment to low-level ionizing radiation. This hybrid distribution F(w) was derived from the exponential distribution Z∼Ex(λ) by the transformation of variate Z=-lnW-(1-W), 0< w<1, in analogy with the hybrid lognormal distribution Z∼N(0, 1) by the transformation of variate Z=(lnρX+ρX-μ)/σ. In this memorandum we present the definition of this hybrid distribution, its main statistical properties, a mechanism of generating the distribution proposed by Uppuluri and Groeer, maximum likelihood estimation of the parameters, figures and tables of features of the distribution, and some applications to data of breeding values by selection and of latent period of leukemias and bone cancers to ionizing radiation. (author)

[en] A method is presented for extracting thin segments of tracks from a gray-level digital picture of NTA film in automatic counting system. To extract thin segments of tracks despite drifting gray level of pixels (picture elements) in the background, the method performs a sequence of local operations involving every element and its 16 neighbors except those immediately outside, determining the class of the element concerning segment and non-segment. The method is able to extract pixels in the track, scarcely those in the background, in a digitized picture (364 x 323 pixels with 7 bits/pixel) of the microphotograph. It extracts pixels of tracks embedded both in the dark and bright backgrounds. (author)

[en] A method is presented for synthesizing track segments extracted from a gray-level digital picture of NTA film in automatic counting system. In order to detect each track in an arbitrary direction, even if it has some gaps, as a set of the track segments, the method links extracted segments along the track, in succession, to the linked track segments, according to whether each extracted segment bears a similarity of direction to the track or not and whether it is connected with the linked track segments or not. In the case of a large digital picture, the method is applied to each subpicture, which is a strip of the picture, and then concatenates subsets of track segments linked at each subpicture as a set of track segments belonging to a track. The method was applied to detecting tracks in various directions over the eight 364 x 40-pixel subpictures with the gray scale of 127/pixel (picture element) of the microphotograph of NTA film. It was proved to be able to synthesize track segments correctly for every track in the picture. (author)

[en] The present report deals with models of dose distribution among workers. The lognormal distribution, which has been recommended by the International Committee of Radiation Protection since 1977, is currently used most widely as a dose distribution model for workers. This is effective when used as an annual dose distribution model for a small group of workers exposed to low-level radiations. When the exposure approaches the permissible dose limits, however, the frequency of exposure to high dose becomes much smaller than the value given by the lognormal distribution. To allow for this, the use of other models, including the hybrid lognormal distribution, superimposed lognormal distributions, Johnson S_B distribution and Weibull distribution, has been proposed. It is suggested in this report that the hybrid lognormal distribution model is the most desirable in terms of 1. easy interpretation from the viewpoint of exposure control, 2. fitness, 3. easy operation and 4. simplicity. Discussions are made to identify the relations of the hybrid lognormal distribution model proposed here with the lognormal distribution model recommended by ICRP. (Nogami, K.)

[en] The analyses of occupational exposure in U.S., made for the federal guidance of radiation protection by the U.S. Environmental Protection Agency, are described as follows: the legal authority of occupational exposure protection and its standard, the procedure of occupational exposure analyses, occupational exposure in 1980s, and the trend of occupational exposure. The number of exposed occupational persons has been increasing with the expanded use of radiation sources in the industries. Then, with the advance in radiation protection techniques, the yearly average dose decreased, and the increase in the yearly collective dose has been limited. However, considerable efforts are necessary to meet the level of 5 rem planned as a new standard. To suppress the increase in yearly collective dose in the future, the practice of ALARA (as low as reasonably achievable) in nuclear power and industrial fields is required. (Mori, K.)

[en] A new type of models of dose-response relationships has been studied as an initial stage to explore a reliable extrapolation of the relationships decided by high dose data to the range of low dose covered by radiation protection. The approach is to use a 'hybrid scale' of linear and logarithmic scales; the first model is that the normalized surviving fraction (ρ S > 0) in a hybrid scale decreases linearly with dose in a linear scale, and the second is that the induction in a log scale increases linearly with the normalized dose (τ D > 0) in a hybrid scale. The hybrid scale may reflect an overall effectiveness of a complex system against adverse events caused by various agents. Some data of leukemia in the atomic bomb survivors and of rodent experiments were used to show the applicability of hybrid scale models. The results proved that proposed models fit these data not less than the popular linear-quadratic models, providing the possible interpretation of shapes of dose-response curves, e.g. shouldered survival curves varied by recovery time. (author)