S. Risica

Radioactivity in building materials: room model analysis and experimental methods.

First, models (room models) published in the international literature allowing the exposure to gamma radiation indoors due to building materials to be assessed are reviewed and discussed. For one of them, a sensitivity analysis concerning the effect of changing the parameters (e.g. dimensions of the room, thickness and density of the walls, etc.) used in calculations is performed. Second, a method is proposed for calculating the activity concentration in the walls of a room using: (a) the measured absorbed dose rate in air in the room; (b) the contributions of natural radionuclides (238U, 232Th and 40K) to the absorbed dose rate in air assessed by means of gamma spectrometry indoors; and (c) the specific dose rate (nGy h(-1) per Bq kg(-1)) of natural radionuclides, for the chosen room geometry, calculated with the room model.

Prenatal exposure to ionizing radiation : Sources, effects and regulatory aspects

Knowledge and awareness of physicians and the general public concerning the risks of prenatal exposure to ionizing radiation are important when developing a correct attitude to ionizing radiation. This is particularly important in the justification of medical diagnostic exposure of pregnant women and in case of possible accidents. The present paper reviews the most recent data on the effects of prenatal exposure to ionizing radiation reported in the scientific literature and in documents of international organizations dealing with this subject. Potentially significant exposure for women of childbearing age in medical diagnostics, working conditions and environmental contamination following the Chernobyl accident are reported. Some examples of doses associated with medical exposure in the course of diagnostic examinations with X‐rays and radiopharmaceuticals, and occupational exposure in workplaces are given. Lastly, the regulatory aspects of the European Union directives and the Italian legislation on medical and occupational exposure of women during pregnancy or in reproductive age are reviewed. □Foetal, in utero, ionizing radiation, radiation protection

INDOOR MEASUREMENTS OF 220Rn AND 222Rn AND THEIR DECAY PRODUCTS IN A MEDITERRANEAN CLIMATE AREA

A research program on characteristics of radon exposure in dwellings in Rome was executed. The results of measurements of 220Rn gas concentration, besides 222Rn and their decay product concentrations, are reported. These measurements were carried out in the sitting-room of six dwellings, for 2-d periods in spring 1995, under normal living conditions. The 220Rn concentration was measured at about 1 cm from the wall, using the method of delayed coincidences between 220Rn and 216Po decays. The average value in the dwellings ranged from 5 Bq/m3 to about 1100 Bq/m3. The average 222Rn and 220Rn equivalent equilibrium concentrations, measured in the middle of the room, were within 8–43 Bq/m3 and 0.5–9.5 Bq/m3, respectively. The average potential alpha energy concentration ratio between 220Rn and 222Rn was within 0.9-4.6. The average equilibrium factor of 222Rn ranged from 0.42 to 0.55. The estimate of effective doses is also discussed. These results confirm the significant presence of 220Rn (thoron) and its decay products and the role of certain natural building materials used in some Italian Regions, not only as gamma and 222Rn sources, but also as 220Rn sources.

Caesium contamination in human milk and transfer factor from diet

A study on caesium contamination in human milk, as a consequence of the Chernobyl fallout, was conducted in 1989 on a group of women from one of the areas of northern Italy most heavily affected by the radioactive fallout. Their diet was studied, and the caesium intake was calculated by using the mean food activity concentration in that area. The caesium transfer factor was evaluated both as the ratio of caesium concentration in mothers milk to the daily intake, and by using a simplified milk compartment model.

Feasibility study of radiation protection guidelines in the use of building materials in the Italian dwellings

The Italian situation concerning the indoor radiation exposure is examined. A tentative comparison of the risk connected with radon and radon daughter indoor exposures and other every day life risks is made. The social economic impact of imposing possible constraints on home building industry is also discussed.

Radioactivity connected with coal burning

The enhanced environmental radioactivity resulting from the operation of a 72 MWe brown coal-fired power plant in central Italy is considered. A source-related control procedure is suggested. The calculated values for the atmospheric dispersion of radioactive effluents and the results of some measurements on brown coals, ash, environmental samples and gamma-exposure levels performed at representative points are reported.

Radon and radon daughter evaluation in a natural radioactivity survey indoors

An indoor survey in order to estimate the population exposure in five towns of an Italian Region is presented. A particular methodology for the campaign was planned and is being applied. Gamma spectrometry of building materials, exposure rate measurements indoors and outdoors and radon concentration measurements indoors were taken with different techniques. A correlation was found between mean gamma exposure rate and mean radon concentration in the houses investigated. An evaluation of mean effective dose equivalents for the inhabitants of the five towns is reported.

Use of an interactive image analysis system (IBAS) to analyze α-particle track energies in cellulose nitrate nuclear track detectors

Abstract An Interactive Automatic Image Analyzer (IBAS) was used to measure α-particle track areas and elliptical factors on LR115 cellulose nitrate detectors. The experiment was conducted with a mixed Pu-239, Am-241 and Cm-244 α-source attenuated in air at different distances and several incidence angles. Energy resolution was estimated for detectors etched in 2.5N NaOH solution at 60 °C and for different times. Track diameter energy dependence results and IBAS image acquisition limits indicate that an α-spectrometer based on this technique may only be constructed under particular conditions.

Radionuclides in pregnancy and breast-feeding

The paper is devoted to the incorporation of radionuclides by pregnant or nursing women, as a consequence of both environmental contamination and diagnostic administration of radiopharmaceuticals, and the transfer of these radionuclides from the mothers body to the embryo or foetus and from the mothers diet to her milk. International knowledge on these issues is reviewed. Furthermore, some calculations carried out by the authors, estimating the activity of some typical radionuclides and the depleted uranium needed to expose the embryo/foetus to a 1-mSv equivalent dose, are reported.

An automatic device for counting a large number of tracks in CR39

Abstract In order to perform an indoor survey of internal exposure to radon and its short life daughters using track etching passive detectors, it is necessary to analyze a large amount of information without spending a lot of time and manual work. For this purpose, the possibility of utilizing PEPR (Precision Encoding and Pattern Recognition) normally used in the digitization of low energy particle tracks recorded on Bubble Chamber film has been studied. A special subroutine has been set up for a PDP 11/45 Computer to guide PEPR in studying the tracks of α-particles in CR39.