Calculation methods of Radon-222 radiological activity for NORM plant with ventilation

A procedure is proposed to determine the radiological activity of air present in the working area of a NORM (Naturally-Occurring Radioactive Materials) plant. This NORM plant is located in the United Arab Emirates and is dedicated to the recycling of material and equipment used in oil extraction facilities. Substantial quantities of NORM waste will be present inside the enclosed plant facilities and will exhale significant amounts of Radon-222 into the working environment. The continued inhalation of this gas and its progeny has been shown to cause lung cancer. In order to reduce the concentration level of the aforementioned gas to an acceptable regulatory value, the best solution is by means of mechanical ventilation. The two calculation methods used to analysis the relationship between the ventilation rate and the degree of radioactive contamination are considered. The first being ventilation by perfect dilution, commonly employed in industrial environments with radiological contamination. The second method of analysis is by means of a CFD (Computational Fluid Dynamics) which permits a more precise calculation of the required fresh air quantity and spatial concentrations. Validation was carried out in a small experimental plant space, obtaining results reasonable approximate to those predicted by the computational analysis. The similarities and differences between the respective calculation methods and their respective fields of application are analyzed. It is concluded that for lower air change rates, less than five air changes per hour, the CFD analysis is the most appropriate method. By contrast, when using a higher rate of outside air changes in the plant, the perfect dilution method should be sufficient enough to control the presence of radon and its progeny. Both calculation methods consider the activity of radon and the activity of the most significant radioisotopes of its progeny

Air diffusion system design in large assembly halls. Case study of the Congress of Deputies parliament building, Madrid, Spain

The paper describes and analyses the air distribution solution adopted in the refurbishment of the Spanish Congress of Deputies assembly hall. A new approach is proposed for the design of displacement ventilation systems. The system performance is methodically validated both with laboratory tests, computational fluid dynamics analysis and experimental field measurements related to the environmental performance of the built environment. In assembly halls, microclimate and displacement ventilation systems, which supply air by means of floor mounted outlets, have been shown to perform adequately. In this case study floor air supply is not feasible. The solution adapted uses parapet mounted diffusers, using a confluent jet flow parallel to the floor plane above the occupied area. All the tools used to analyse the performance of this system showed that the admixing overhead supply, with ceiling return, and flowing parallel to and above the occupied zone is drawn back into the occupied zone, creating a plume effect similar to that of floor mounted displacement outlets. Thus, this confirms that the displacement effect can be accomplished using a high induction turbulent overhead supply with ceiling return. Therefore supplying air directly into the occupied zone, at or near to floor level, is not a prerequisite to achieve the desired displacement effect. This report concludes that, using the correct design parameters, as set out in this paper, the displacement ventilation effect is independent of the plane of air supply. The conclusions suggest that accepted criteria for the definition and design of displacement systems should be redefined