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[en] In previous report, a potential flow model was developed to predict wind fields in complex terrain. In the potential flow model, wind vectors and air flows are estimated from a velocity potential function obtained by combining two or three-dimensional doublets and a uniform stream. In this report, we examined the potential flow model for its validity. The wind directions calculated by the potential flow model are compared with the results of field experiments in presence of double Gaussian form models. The overall agreement of the calculated wind directions with the experimental measurements is good. The wind profiles calculated by the potential flow model are compared with three different experiments; wind tunnel experiment in presence of a two-dimensional triangular hill, field experiment in presence of double Gaussian form models, and field experiment in presence of a real terrain form model. The potential flow model overestimate the wind velocities near ground, because the potential flow cannot provide viscous effects. To introduce viscous effects, the definition of the velocity potential is modified to include height-dependent coefficient determined by an inflow velocity profile. The wind profiles calculated by the revised model are in much better agreement with measurements. (author)

[en] Emergency assessment and response systems for prediction of the consequences of an accidental atmospheric release from a nuclear power plant have been reviewed. At present, several organizations in the U.S. have the emergency assessment and response systems. They are used to provide responses to actual accidents and exercises and post-accident assessments. They should be composed of a prediction system for concentration and dose, an acquis ition system for meteorological data, a monitoring system for radioactive effuluent gas and radiological environmental data, a management system for regional data and so on. However, the monitoring system and the regional management system has not been developed completely. This report describes the prediction system for concentration and dose and the meteorological data acquisition system. In the emergency assessment and response systems currently in operation, the prediction of concentration and dose are generally carried out by using a simple atmospheric transport and diffusion model, which dose not take account of topographical effects. Besides, these systems often assume the release rate to be unity, since it is difficult to obtain information on release rate in case of accidents. These systems have therefore following problems: 1. these systems are not applicable to prediction of atmospheric diffusion phenomena in complex terrain. 2. obtaining absolute values of concentration and dose in case of accidents is difficult. (author)

[en] This report proposes a calculation model to estimate the gamma exposure rate due to radioactive clouds released from a nuclear power plant under an accident condition. This method is based on a plume segment atmospheric transport model. A plume segment is considered to be a sequence of puffs. The gamma exposure rate from a puff is assumed to be a function of σsub(z), the ratio σsub(y)/σsub(z) (= β) and r. Here, σsub(y), and σsub(z) are standard deviations of a single isotropic puff, in the crosswind, and vertical directions, respectively, and r is the distance from an evaluation point to the center of the puff. The standard exposure rate, namely, the exposure rate from the puff that has standard values for σsub(z) and β, is estimated from the predetermined approximate polynominal equations. These equations describe the relation between the exposure rate of a single puff and r. The exposure rate of a puff that has an arbitrary values for σsub(z) and β is calculated by interpolating the standard exposure rate. The exposure rates at an evaluation point are calculated by summing up the exposure rate from each puff which forms plume segment. The features of the model proposed in this report are as follows; 1) The exposure rate at the evaluation point within a perimeter about 10 km from a nuclear power plant, where the submersion model is not effective, can be calculated. 2) By incorporating a three-dimensional wind field model into this model, we can take account of spatial variations in the wind field. 3) The exposure rates can be calculated every 10 mins to 1 h in response to temporal changes of meteorological conditions and release rates. (author)

[en] The measured γ-exposure rate around nuclear power plants is due mainly to natural causes and radioactive clouds emitted from the plants. An exposure calculation method based on puff model has been already proposed to identify the plant contributions and to estimate values in response to short-term fluctuations of meteorological condition and the release rate. However, the calculation method by this model consumes a lot of computer time, since the calculation requires a three-dimensional integration of the distribution of the concentration from each puff. Hence, we propose a simplified method using approximate polynominal equations and interpolations. The computer time needed for the calculation with the simplified method is reduced to 1/30 of that required by the previous method. The calculation results by simplified method are compared with those by the previous method and with the measured exposure rate less natural background. The results of two different methods are in good agreement. The calculated exposure rate is within the range from half to twice as much as the measured exposure rate less background. (author)

[en] A Gaussian trajectory model was developed to predict atmospheric diffusion phenomena in complex terrain. In this model, the plume trajectories are estimated from the potential flow model or quasi-potential flow model previously developed by CRIEPI. As for the standard deviation of the plume width, the parameters including terrain effects, which have been estimated by wind tunnel experiments, are used. The validity of the calculation results by the Gaussian trajectory model was confirmed through comparisons against outdoor experimental results and calculation results by finite difference method. A comparative study of the Gaussian trajectory model and other diffusion models was made from the view point of practicalities. The result shows that the model proposed in this report is almost free from computer restrictions and easy to use. It may be safely said that this model is useful in concentration and dose estimation in case of accidental atmospheric release from nuclear facilities. (author)

[en] Assessment of environmental effect originating from natural radionuclides contained in fly ash released from a coal-fired power plant was carried out and the following results were obtained. 1) Mean concentrations of U, Th and K of 28 kinds of coals produced in Japan or in abroad were 1.0 ppm, 3.3 ppm and 2300 ppm, respectively. There is a good correlation between U and Th concentrations. 2) Natural radionuclides concentrations of both bottom and fly ashes were approximately equal in both ashes, and the value were the same as the value of the radionuclide concentration in coal divided by ash. 3) Natural radionuclide quantities of 40 K and of each decay chain of U or Th was evaluated as 2 -- 40000 pCi/sec for model coal-fired power plants of 1,000 and 250 MW. 4) Natural radionuclide concentration in air due to the plume at the maximum concentration point were 5 x 10^-9 -- 5 x 10^-5 pCi/m³, and these values were lower than 1/200 of those of the natural origin. 5) Radiation from fly ash at the maximum concentration point was about 0.01 mrem/yr in each case-study and these values were below 1/10⁴ of those from natural radiation sources. (author)

[en] The applicability, problems of measurement and present status of the radioreceptor assay of ACTH were examined, and it was compared with the radioimmunoassay of ACTH. The molecular and receptor combination site, the biologically active site and the character of the ACTH receptor were outlined. Methods for the separation and purification of the ACTH receptor, a method for the labelling of ACTH, and a radioreceptor assay of ACTH in blood were mentioned. The radioreceptor assay was found to be more useful than the radioimmunoassay. (Kanao, N.)

[en] Because effluent gas is sometimes released from low positions, viz., near the ground surface and around buildings, the effects caused by buildings within the site area are not negligible for gas diffusion predictions. For these reasons, the effects caused by buildings for gas diffusion are considered under the terrain following calculation coordinate system in this report. Numerical calculation meshes on the ground surface are treated as the building with the adaptation of wall function techniques of turbulent quantities in the flow calculations using a turbulence closure model. The reflection conditions of released particles on building surfaces are taken into consideration in the diffusion calculation using the Lagrangian particle model. Obtained flow and diffusion calculation results are compared with those of wind tunnel experiments around the building. It was apparent that features observed in a wind tunnel, viz., the formation of cavity regions behind the building and the gas diffusion to the ground surface behind the building, are also obtained by numerical calculation. (author)

[en] A system is presented for the prediction of the consequences of an accidental atmospheric release from a nuclear power plants. In this system, concentration calculations are performed with a three-dimensional Gaussian plume trajectory model. The potential flow model or quasi-potential flow model developed in our laboratory is used to provide the three-dimensional space- and time-varying advection field to the trajectory diffusion model. The meteorological data required by those wind field models are observed or forecasted winds at a certain point typical of inflow boundary condition. The forecasted winds are calculated from a statistical model using principal component analysis and maximum entropy method. The diffusion parameters are estimated from the concentration distributions measured with wind tunnel experiments for the topographical models of a site of interest and its surroundings. The gamma exposure rates due to radioactive plumes are calculated from a simplified exposure model based on plume segment model. The dose assessment method described in this report is useful in real-time estimation of the behavior of radioactive plumes released from nuclear facilities located in complex terrain. (author)