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Zeolites Filters for Aerosols Decontamination

#A-1377


Preparation of Highly Effective Filtering Materials for Decontamination of Aerosols Based on Zeolites and Development of a Work Cycle for their Manufacture

Tech Area / Field

  • BIO-RAD/Radiobiology/Biotechnology
  • MAN-MAT/Engineering Materials/Manufacturing Technology

Status
3 Approved without Funding

Registration date
07.12.2005

Leading Institute
Institute of Radiophysics and Electronics, Armenia, Ashtarak-2

Collaborators

  • University of Pennsylvania / School of Arts and Sciences, USA, PA, Philadelphia\nNew Mexico Tech, USA, NM, Socorro\nUniversity of Thessaloniki / Department of Chemistry, Greece, Thessaloniki\nTohoku University / Graduate School of Engineering / Department of Quantum Science & Energy Engineering, Japan, Sendai\nNational and Kapodistrian University of Athens / Department of Mineralogy and Petrology, Greece, Athens\nEngineering Planning and Management, Inc., USA, MA, Framingham\nSouthwest Research Institute / Geoscience and Engineering Division, USA, TX, San Antonio

Project summary

Development of the nuclear power industry in the third millennium will require extensive research and practical works aimed at improvement of radiological safety measures, and first of all air contamination control, both inside the NPP premises and in the open areas. Special attention is paid lately to the safety of personnel and population in course of NPP running.

It is the major purpose of this Project to analyze the efficiency and determine the optimal parameters of systems filtering the NPP releases in the atmosphere of radioactive aerosols, with the systems using zeolite as a filtering material. We also plan to develop an experimental air-purification system and test it in real conditions of NPP work.

Selection of zeolite is explained by the fact that rich deposits of this rock are present in many regions of Armenia. A filter filled with grains of chemically and thermally treated modified zeolite, mechanically activated in the optimal conditions, is able to capture 85 to 98 % of radioactive aerosols. Such a high sorption activity of the filter is explained by physical, physical/chemical and chemical processes originating in the zeolite due to its mechanical and chemical treatment and resulting from relaxation of the stress field in the material after such treatment.

Capture of radio isotopes, 0.01 to 10 m in diameter suspended in the air, is necessary due to their high activity and pathogenic effect on the human organism after penetration, mostly through inhaling.

The works under this Project shall be performed along the following main directions:

  1. Using the results of general filtration theory for aerosols, we suggest to analyze the dependence of effects given below on the grain-size of zeolite filters:
  • inertial effect;
  • diffusion effect;
  • sedimentation effect;
  • sieve effect;
  • hooking effect;
  • electrostatic effect;
  • magnetic fields effect
2. We shall select the optimal size of the filtering grains and parameters of filtering units, providing maximal filtering efficiency for the given values of air pressure at the input and output of the filtering units.
3. Optimal regimes of mechanical and chemical activation of the natural zeolite will be determined, providing high capturing capacity of radioactive aerosols.
4. The obtained results of analysis will be used in manufacturing of experimental air-purification system.
5. The developed filters unit will be tested in the real conditions.
6. We shall develop a technological cycle for production of filtering materials based on the Armenian zeolites and designed for removal of man-made aerosols from the air, including radioactive aerosols.

In order to reach these objectives, we shall carry out the following works:


1. Using the known models adapted to the real conditions of the NPP ventilation systems work and providing their maximal efficiency
  • to analyze the dependence of filtering efficiency on parameters of the porous materials used in the filtering systems (particularly of zeolites);
  • to determine the optimal parameters of the porous materials used by the filtering systems, providing maximal filtering efficiency;
  • to determine the optimal air-flow velocity providing maximal filtering efficiency;
  • to find the optimal relation between the grain size and air-flow velocity.
2. To determine the optimal conditions for mechanical activation of the natural zeolite providing a maximally narrow fraction with minimal size of the grains and maximal surface adsorption activity for high degree of trapping of radioactive aerosols.
3. To perform mechanical/chemical surface activation jointly with treatment of crushed-active zeolite with modifier inside the mill.
4. To choose a binding material for deposition of the modified zeolite on the fabric substrate, which would not deteriorate the filtering qualities of zeolite.
5. To manufacture an experimental filtering unit in order to test the developed material in real operation conditions.
6. To investigate the electrostatic and magnetic fields effect on the filtering characteristics of the air-purification system.
7. To develop a technological cycle for production of cost-effective and highly efficient filtering materials on basis of the Armenian zeolites, designed to trap man-made, including radioactive, aerosols.

Implementation of the project would solve the following tasks meeting the ISTC objectives:

  • to switch the character and provide a long-term professional activity of scientists and specialists earlier engaged in defense developments to urgent peaceful tasks;
  • the project allows the specialists in arms to alter their activity and gain skills in the area of environment protection. The latter is very significant for Armenia where an NPP is currently running and its shut-down is planned in course of several years. During the halt period, a significant increase of radioactive releases in the atmosphere is expected, making the task of their effective purification vitally important. The Armenian NPP is also known to economic difficulties, so that introduction of a more efficient and cost-saving filtering is able to reduce the shut-down costs. The information gained in process of closing the Armenian NPP may be useful to many organizations, power plants, and specialists, since there is almost no experience in stopping NPPs with ВВЭР-440 reactors;
  • integration of scientists and specialists in the international research programs concerning environment protection from radioactive emissions of NPPs is extremely important for population safety;
  • support and development of fundamental and applied researches for peaceful purposes, in the area of environment protection.

The list of the project participants suggests that the stated objectives can be successfully reached. The group of radiological measurements has over 25 years of experience of aerosols trapping from the NPP emissions in the atmosphere, as well as in the NPP premises. It has a significant database for that period and is well familiar with the state of the art in selection, preparation and analysis of samples.

In course of many years the group collaborated with the USSR Public Health Ministry Institute of Biophysics and the Institute of Applied Geophysics in the area of radiological monitoring. This group was the first to detect the man-made radio nuclides in the atmosphere created by the emissions from NPPs. Concentration of radioactive aerosols was estimated as a function of technological operations at NPPs and state of their filtering systems [3]. Project participants long deal with zeolites [4-10] and have a significant experience in application of zeolitesin various filtering systems. Particularly in course of the ISTC Project A-485 the specialists have developed highly efficient filters for purification of radioactive effluents on basis of a modified zeolite.

The project team also includes persons well familiar with data processing methods and simulation of filtering processes.

All teams possess the major part of equipment required for implementation of project, including the equipment gained under the ISTC Project A-773.

Technical approach and methodology consists in combination of many experimental methods (spectrometry, radiometry, etc.) with theoretical modeling (both analytic and numerical). This combination will allow obtaining unambiguous characteristics for fillers of the filtering systems, their parameters, and development of recommendations for optimal air-purification systems manufacturing, which along with their high filtering efficiency would be also cost-saving.

The project results promise to be fairly interesting for the organizations running the nuclear power plants, as well as for companies dealing with:

  • research and developments in the area of people and environment protection in process of NPP construction, running, and shutting down;
  • research and developments in the area of NPP ventilation air purification, as well as air cleaning inside the NPP premises;
  • research and developments in the area of trapping non-radioactive aerosols at various production facilities.


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