Radioactive Plume Research Articles

The chernobyl accident: Modelling of dispersion over europe of the radioactive plume and comparison with air activity measurements

Following the release of radionuclides from the Chernobyl power plant accident, a long-range transport and deposition model is used to describe the plume dispersion over Europe. The aim of this study is the validation of a fast Lagrangjan model and a better understanding of the relative impact of some mechanisms, such as the initial plume rise. Comparisons between results and 137Cs measurement activity are discussed according to spatial and temporal variations. It is shown that many measurements can be explained only if the initial plume rise taken at 925, 850 and 700mb is considered.

Study of the medium- and long-range transport analysing the data of the Chernobyl accident

In the present work we analyse the meteorological factors that characterized the transport and deposition on the ground of the radionuclides from the Chernobyl nuclear power station over Northern Italy during the accident in April–May 1986. The aim of our study is to test some computational procedures and meteorological analyses specific for a comprehensive study of long-range pollution transport problem. By reconstructing the particle trajectories of the radioactive Chernobyl plume, we determined the most probable starting and arrival date of the plume and the level over the source. Moreover, analysis of the meteorological configuration up-and downwind the Alps permitted us to explain the temporal displacement between different kinds of measured fall-out.

A sensitive method for quantitative measurements of the concentration of various gamma-emitting radionuclides in reactor plumes using a germanium detector

The Gaussian plume model has been adapted to calculate the primary photon fluence rate for a given release rate, height and distance over long periods and during different types of weather conditions. Corrections due to the varying efficiency of a Ge detector for different photon energies, angle of incidence and plume configuration have been developed. Using these, together with background measurements, minimum detectable release rates from nuclear power stations during normal operation have been estimated for radioactive inert gases. A carefully calibrated Ge detector, with proper lead shielding, is a sensitive instrument for long-term average measurements of radioactive plumes and is far superior to GM counters and ionizing chambers.The release rate may be evaluated more accurately than before by means of different dispersion models.

放射性雲からのガンマ線体外被曝線量計算における核種放出光子エネルギーの扱い

A simple method that uses effective energy and average energy has been used for calculating gamma doses from radioactive plumes. Although the additive method, in which the contributions to gamma doseS due to the photons released from a noble nuclide are added together, should be used for this purpose, the computation is very time-consuming, so that a simplemethod is desirable in emergencies. The relationship between the calculated doses and the photon energy is complicated and no linear expression holds good. Thus, when the photon energy is widely dispersed, the simple method is not appropriate, We cornpared the results of the simple method with those of the additive method, and examined the applications of both am the limitations of the simple method. It was found that for most nuclides the simple method gave overestimates of within 20% for doses on downwind axis, and for a few nuclides, under. estimates by more than 90% were seen for doses apart from the downwind axis near a stack. We suggest a method of correction in which the photons released from a nuclide are grouped into two categories: those with an energy of less than 50keV and those with a higher energy. When the sum of the doses due to these two groups of photons was obtained, the errors were within 5%.

Approximations to evaluate the external dose integral for reactor accidents

The external exposure from the radioactive plume is one of the most important routes of radiation burden in the early phase of a reactor accident. To estimate the external radiation dose to the population around the nuclear facilities the three dimensional dose rate integral must be evaluated. Introducing spherical coordinates the integration by the variable R can be approximated by an asymptotic expansion in series of the integral for large distances and by Taylor’s expansion of the integrand for small distances. So we have to evaluate the integral by a numerical method only for two variables instead of three.

Estimation of Embryonic and Fetal Doses from Accidentally Released Radioactive Plumes

Estimation of Embryonic and Fetal Doses from Accidentally Released Radioactive Plumes

A Three-Dimensional Potential Flow Model for the Prediction of the Behavior of Radioactive Plumes

A potential flow model was developed to predict wind fields in complex terrain. In this model, wind vectors and airflows are estimated from a velocity potential function. It was found that the velocity potential function is obtained by combining threedimensional doublets at each grid point on a horizontal plane and a uniform stream parallel to the surface of the earth. The strengths of the doublets were expressed as a function of the terrain height at each grid point. Wind components at an arbitrary point were easily calculated from the potential flow model proposed. Consequently, this potential flow model is useful in estimating airflows, the convergence and divergence of the distances between streamlines, and the trajectories of radioactive plumes.

Measurement of distribution coefficients using a radial injection dual‐tracer test

The dispersive and adsorptive properties of a sandy aquifer were evaluated by using a radial injection dual‐tracer test with 131I as the nonreactive tracer and 85Sr as the reactive tracer. The tracer migration was monitored by using multilevel point‐sampling devices located at various radial distances and depths. Nonequilibrium physical and chemical adsorption effects for 85Sr were treated as a spreading or dispersion mechanism in the breakthrough curve analysis. The resulting effective dispersivity values for 85Sr (range of 0.7–3.3 cm; mean of 1.9 cm) were typically a factor of 2–5 larger than those obtained for 131I (range of 0.4–1.5 cm; mean of 0.8). The distribution coefficient values obtained from analysis of the breakthrough curves at three depths and two radial distances ranged from 2.6 to 4.5 ml/g. These compare favorably with values obtained by separation of fluids from solids in sediment cores (4.3–11.7 ml/g), by batch experiments on core sediments (2.8–10.8 ml/g), and by analysis of a 25‐year‐old radioactive waste plume (mean of ≃10 ml/g) in another part of the same aquifer. Correlations of adsorbed 85Sr radioactivity with grain size fractions demonstrated preferential adsorption to the coarsest fraction (associated with micaceous minerals) and to the finest fraction. The relative amounts of electrostatically and specifically adsorbed 85Sr on the aquifer sediments were determined with desorption experiments on core sediments using selective chemical extradants. The withdrawal phase breakthrough curves for the well, obtained immediately following the injection phase, showed essentially full tracer recoveries for both 131I and 85Sr. Relatively slow desorption Of 85Sr, indicated by extreme tailing of the return break‐through curve and analysis of residual radioactivity on sediment cores, provided further indication of the nonequilibrium nature of the adsorption‐desorption phenomena.

Real-Time Simulation of Gamma Exposure Rate by Puff Model

The measured gamma exposure rate around nuclear power plants is due mainly to natural causes and radioactive plumes emitted from the plants. A calculation method based on a puff model has been proposed to identify the latter contribution and evaluate quantities in response to short-term fluctuations of meteorological conditions and the release rate. The calculation results have been compared with the measured exposure rate less the natural background. In general, the calculation exposure rate is one-half to twice as much as the measured exposure rate less the background. 12 refs.

Radioactive plume from the Three Mile Island accident: xenon-133 in air at a distance of 375 kilometers.

The transit of an air mass containing radioactive gas released from the Three Mile Island reactor was recorded in Albany, New York, by measuring xenon-133. These measurements provide an evaluation of Three Mile Island effluents to distances greater than 100 kilometers. Two independent techniques identified xenon-133 in ambient air at concentrations as high as 3900 picocuries per cubic meter. The local gamma-ray whole-body dose from the passing radioactivity amounted to 0.004 millirem, or 0.004 percent of the annual dose from natural sources.

Atmospheric Electrical Plume Detection: Theory and Field Measurements

Abstract Airborne atmospheric electrical measurements may be useful in studies of air pollution, turbulence, and aerosol distributions. A short summary of the electrical nature and behavior of the atmosphere is given relative to the atmospheric electrical detection of aerosol plumes. An example of the efficacy of this approach is illustrated through an experiment in which an aircraft equipped with atmospheric electrical instruments flew side by side with another aircraft equipped to measure particles and gases while tracking a plume out to 90 km. The approach described would be equally viable for the detection of exhaust tracks from ships and submarines and for detecting and monitoring radioactive plumes.

Calculation of the depletion of a radioactive plume in the atmosphere and subsequent exposure due to deposited activity

An efficient method has been developed for calculating the depletion, by dry deposition and washout to the ground, from a plume of fission products in the atmosphere, and for determining the isotopic composition of resulting gamma and beta activities in the ground deposit at any selected point downwind. By integration over the pattern of material on the ground, gamma and beta exposure rates may be derived as a function of the ageing time of the deposit. Elements in the plume are assigned to one of up to four ‘groups’; elements within each group being assigned a particular deposition velocity and washout coefficient. Calculations have been performed, for a notional MAGNOX depressurization accident, which illustrate the sensitivity of ground gamma spectra and exposure rate to the use of isotope-dependent deposition velocities. Circumstances under which it may be necessary to perform a full two-dimensional integration over the pattern of material on the ground are discussed.

The Rise of Strongly Radioactive Plumes

Abstract The presence of radioactive gases in a plume, such as could occur in the event of a nuclear reactor accident, leads to the addition of buoyancy to the plume at an approximately linear rate. Buoyancy might also be added to plumes by chemical reactions, radiation, or latent heat exchange. The resulting plume rise is calculated by a model similar to that used to calculate the rise of ordinary plumes. The case of a radioactive plume is examined in some detail. For the slow leakage of radioactive gases assumed to occur under postulated reactor accident conditions, plume rise due to radioactivity can be neglected. For more rapid leakage rates or for larger reactors, plume radioactivity leads to significant rises.