Inhalation Of Radioactive Aerosols Research Articles

Applicability of an Ionising Radiation Measuring System for Real-Time Effective-Dose-Optimised Route Finding Solution during Nuclear Accidents

The reduction in the effective dose of evacuated injured persons through contaminated areas of nuclear accidents is an essential emergency services requirement. In this context, there appeared a need to develop a dose-optimised route finding method for firefighting rescue vehicles, which includes the development of a real-time decision support measurement and evaluation system. This determines and visualises the radiation exposure of possible routes in a tested area. The system inside and outside of the vehicle measures the ambient dose equivalent rate, the gamma spectra, and also the airborne radioactive aerosol and iodine levels. The method uses gamma radiation measuring NaI(Tl) scintillation detectors mounted on the outside of the vehicle, to determine the dose rate inside the vehicle using the previously recorded attenuation conversation function, while continuously collecting the air through a filter and using an alpha, beta, and gamma radiation measuring NaI(Tl)+ PVT + ZnS(Ag) scintillator to determine the activity concentration in the air, using these measured values to determine the effective dose for all routes and all kinds of vehicles. The energy-dependent shielding effect of the vehicle, the filtering efficiency of the collective protection equipment, and the vehicle’s speed and travel time were taken into account. The results were validated by using gamma point sources with different activity and energy levels. The measurement results under real conditions and available real accident data used in our simulations for three different vehicles and pedestrians proved the applicability of the system. During a nuclear accident based on our model calculations, the inhalation of radioactive aerosols causes a dose almost an order of magnitude higher than the external gamma radiation caused by the fallout contamination. The selection of the appropriate vehicle and its route is determined by the spectrum that can be measured at the accident site but especially by the radioactive aerosol concentration in the air that can be measured in the area. In the case of radiation measuring detectors, the shielding effect of the carrier vehicle must be taken into account, especially in the case of heavy shielding vehicles. The method provides an excellent opportunity to reduce the damage to the health of accident victims and first responders during rescue operations.

Importance of Uranium Recovery Facility Product Characteristics for Dose Assessment and Assignment.

Two traditional methods are used, often in combination, for assessing the intake and resulting dose from the inhalation of radioactive aerosols. The first calculates the intake based on air sampling programs and assessing and assigning dose using published dose conversion factors. The second approach assigns dose from the results of bioassay programs using measurements of radionuclides in human excreta (ex vivo, sometimes referred to as "in vitro") or via direct measurements of radionuclides in the body (in vivo) in combination with metabolic models. This paper describes standard practices using each of these methods to assess and assign worker dose from inhalation of uranium products produced at natural uranium processing facilities, namely uranium mills and in-situ uranium recovery facilities (ISRs). Chemical speciation is an important consideration, which relates directly to solubility in body fluids and associated metabolic behavior. The concepts are illustrated by specific examples applicable to the products to which workers can be exposed at natural uranium processing facilities.

Estimates of radiological risk from depleted uranium weapons in war scenarios.

Several weapons used during the recent conflict in Yugoslavia contain depleted uranium, including missiles and armor-piercing incendiary rounds. Health concern is related to the use of these weapons, because of the heavy-metal toxicity and radioactivity of uranium. Although chemical toxicity is considered the more important source of health risk related to uranium, radiation exposure has been allegedly related to cancers among veterans of the Balkan conflict, and uranium munitions are a possible source of contamination in the environment. Actual measurements of radioactive contamination are needed to assess the risk. In this paper, a computer simulation is proposed to estimate radiological risk related to different exposure scenarios. Dose caused by inhalation of radioactive aerosols and ground contamination induced by Tomahawk missile impact are simulated using a Gaussian plume model (HOTSPOT code). Environmental contamination and committed dose to the population resident in contaminated areas are predicted by a food-web model (RESRAD code). Small values of committed effective dose equivalent appear to be associated with missile impacts (50-y CEDE < 5 mSv), or population exposure by water-independent pathways (50-y CEDE < 80 mSv). The greatest hazard is related to the water contamination in conditions of effective leaching of uranium in the groundwater (50-y CEDE < 400 mSv). Even in this worst case scenario, the chemical toxicity largely predominates over radiological risk. These computer simulations suggest that little radiological risk is associated to the use of depleted uranium weapons.

Analyses of radioactive aerosols to support accurate internal dose assessments at Chin-Shan nuclear power plant.

Studies of the physical and chemical properties of radioactive aerosols produced in different work environments were made at Chin-Shan nuclear power plant in Taiwan. These properties, including particle mass- and activity-size distributions, elemental and radionuclide compositions, and solubility lung class, are essential for the assessment of internal dose equivalents from the inhalation of radioactive aerosols. Several practices and environments studied include thermal arc cutting, grinding, sandblasting, and noble gas progeny. For physical analyses, cascade impactors, scanning electron microscopy with energy-dispersive x-ray analysis, inductively coupled plasma atomic emission spectrometry, and neutron activation analysis were applied. For chemical analyses, the solubility lung class was determined, in vitro, with the measurement of aerosol dissolution rates in simulated biological fluids. Results of these analyses were used to calculate the annual limit on intake, the derived air concentration, and committed dose equivalents for radiological protection against radioactive aerosols produced at Chin-Shan nuclear power plant.

Microdosimetry of Rat Alveolar Type II Cells Irradiated with a Particles from 239 PuO 2

The alveolar type II cell is one of the critical cells for radiation damage in the lungs after inhalation of radioactive aerosols. With the aid of a Quantimet-970 image analyzer and a VAX-11/780 computer, we calculated the radiation dose to rat alveolar type II cells from alpha particles emitted by 239PuO2. A series of dosimetric parameters for type II cells, including track length distribution, linear energy transfer (LET), values of the specific energy for a single hit of a spherical target (z1), cellular dose, hit number, and their spatial distributions were calculated. By comparing the volume density of type II cells and lung tissue with energy deposited in alveolar type II cells, we found that the energy deposited per unit volume of type II cells was larger than that of lung tissue excluding type II cells. The z1 for spherical targets and the LET across type II cells were less than those in lung tissue excluding type II cells. The age of the rat and damage to lung by inhalation may significantly influence some of the parameters. The neoplastic transformation probability for type II cells is also discussed. The results suggest that the type II cell is an important target cell in the rat lung for exposure to inhaled 239PuO2.

Clinical ventilation-perfusion scintigraphy.

Ventilation-perfusion scintigraphy is an established procedure for the investigation of lung disease. Perfusion scans are commonly obtained with a gamma-camera following injection of 99mTc-labelled microspheres. For the assessment of regional lung ventilation, a number of techniques are now being employed, i.e. 133Xe and 127Xe single breath/washout studies, continuous inhalation of 81mKr and inhalation of radioactive aerosols. The latter two methods are now gaining consideration in clinical practice. Lung perfusion scanning is highly sensitive for detection of regional abnormalities of blood flow; the diagnosis of pulmonary embolism remains the most important clinical application of the technique. In this context, the use of a ventilation scan is required in order to increase the specificity of the procedure. In general, lung ventilation-perfusion scintigraphy is of great value for the management of patients with both primary lung disease and heart disease, by providing pathophysiological information of importance for the diagnosis, follow up and the functional evaluation of the patient.