Sheltering--a protective measure following an accidental atmospheric release from a nuclear power plant.

The effectiveness of sheltering the population for reducing radiological effects following an accidental release of radioactivity at a nuclear power plant was investigated. Different levels of respiratory protection and the administration of a thyroid blocking agent were also studied as possible complements to sheltering. Specific conditions were assumed, concerning the high protection factors of regular buildings and the high availability of civil defense shelters. Computations were performed by means of a probabilistic consequence model, which allows a comprehensive description of exposure modes and processes dealing with the implementation of sheltering and which takes into account a broad range of radiological effects. Sheltering, even in regular buildings, was found to be efficient in reducing early fatalities and other non-stochastic effects. However, it was shown that respiratory protection is also needed in order to alleviate stochastic effects and that, for this purpose, expedient individual filtration methods may be satisfactory. Under the conditions studied, sheltering was found to be preferable in most cases over evacuation, as the main immediate protective measure, unless evacuation can be carried out before the radioactive cloud reaches the populated area.

Sensitivity analysis of the influence of source-term and environmental parameters on the radiological risk of coal-fired plants.

A sensitivity analysis was undertaken to determine the influence of different source-term and environmental parameters on the radiological risks from a coal-fired plant (CFP). It was found that the release rate of radionuclides and the effective release height most significantly influence radiological risk. Site characteristics, such as rain scavenging coefficients and food acquirement habits, have a lesser influence, and some parameters, such as time delay before ingestion of contaminated food, have practically no influence on the radiological impact of a CFP. The contribution to radiation risks of different exposure modes (i.e. inhalation, ingestion and contact with ground surface) were also analyzed, as well as of specific radionuclides and human body organs. Results of the sensitivity analysis were interpreted in terms of the characteristics of the fuel, facilities and site of a CFP. It is concluded that by proper choice of coal, furnace, ash filtration and stack height, as well as by proper siting, the radiological impact of a CFP can be drastically reduced.

RADFOOD--a dynamic model for radioactivity transfer through the human food chain.

Radioactive fallout presents a short-term risk due to its direct deposition on agricultural crops, as well as a long-term risk resulting from its deposition on soil and subsequent uptake by crops. A dynamic model, RADFOOD, was developed, based on different existing models. It simulates transport of fallout radionuclides through agricultural food chains to man and evaluates the radiation doses resulting from consumption of contaminated food. Transport was modeled through compartments representing various environmental elements of food products. Internal radiation doses (whole-body weighted doses) following ingestion of contaminated foodstuffs were then estimated. Specific types of crops, soils and diet of man and livestock were considered. A sample calculation was performed in which individual and collective radiation doses, as well as associated health effects, resulting from fallout contamination were evaluated. They were estimated for food consumption beginning at various times after the fallout deposition and for different consumption durations. A sensitivity analysis, performed for the main model parameters, showed that the radiation dose is sensitive, for the short-term period, to changes in initial deposition levels and in the parameters characterizing initial fallout interception and resuspension.

Die-away kinetics of aerosolized bacteria from sprinkler application of wastewater.

A methodology for estimating, under field conditions, the microbial die-away constant (lambda) is presented. This constant may be used in predicting the aerosolized pathogenic microorganism concentrations downwind from a wastewater spray or aeration site by means of modified atmospheric diffusion equations. The mean lambda of Escherichia coli for very early morning runs was 8.8 X 10(-3)s-1, and that for afternoon runs was 6.6 X 10(-2)s-1.