Andrzej G. Chmielewski

Membrane processes in nuclear technology-application for liquid radioactive waste treatment

Membrane methods can be considered as the most energy-saving separation techniques. Separation abilities of membranes allow the elimination of many non-effective and energy consuming methods and their replacement by new, modern technologies, friendly environment friendly. An application of membrane methods for liquid radioactive wastes treatment requires solving many problems connected with the proper selection of the membranes, membrane modules and other equipment according local conditions: chemical and radiochemical composition of the effluents treated, their activity and total salinity. The installations working in nuclear industry have to fulfil very strict requirements. They ought to be reliable, constructed from special materials defined by separate regulations. Only small number of manufacturers of membrane devices has for their products the certificates of International Atomic Energy Agency. Reverse osmosis (RO) as a method for liquid waste treatment has been examined at laboratory and pilot plant installations. The experience with the process led to design and construction of the industrial plant, 1 m3 capacity, composed of three RO stages. The plant will be included into the system for liquid radioactive wastes purification operating at Institute of Atomic Energy in Swierk near Warsaw, treating the liquid waste from all of Poland. Membrane distillation (MD) can be an alternative for liquid radioactive waste concentration. On the basis of previous laboratory tests a pilot plant for liquid radioactive wastes concentration employing direct contact MD was constructed. Pilot plant experiments showed MD is interesting solution for liquid low-level radioactive waste treatment. As MD is characterised by high retention, large decontamination factors were obtained in separation of radionuclides, which are present in liquid low-level radioactive wastes mainly in an ionic form. The RO and MD plants for liquid low level radioactive wastes treatment are presented in the paper and the evaluation of both methods, as well.

Reduction of VOCs in flue gas from coal combustion by electron beam treatment

Abstract Coal combustion is one of the biggest sources of VOCs, which are emitted with various concentrations, polynuclear aromatic hydrocarbons (PAH) are known as the most dangerous, and among them, e.g. benzo(a)pyrene C 20 H 12 , benzo(g,h,I)perylene C 22 H 12 or dibenzo(a,h)anthracene C 22 H 14 are the most toxic according to EPA. Recent years have brought new regulations concerning PAH emission, and European countries have signed an international treaty, covering PAH emission. Tests at the pilot plant constructed at a coal-fired power station were performed with the purpose of estimating the influence of electron beam on VOCs present in flue gas, during SO 2 and NO x removal. The influence of electron beam on the global toxicity factor of flue gas has been analysed. In the presence of ammonia, the concentrations of some PAHs were lower than that without ammonia. The removal efficiencies have been ranged from 40% up to 98%.

Pilot plant for flue gas treatment with electron beam -start up and two stage irradiation tests

Abstract The pilot plant for flue gas treatment with electron beam has been built at Power Plant Kaweczyn, near Warsaw. The irradiation part of the pilot plant has been put in operation in 1991 whereas the complete installation including bag filter started to work in spring 1992. The starting tests consisted of studying the components reliability and influence of the two-stage irradiation process on efficiency of NO x removal. The results have shown that the two- stage irradiation leads to remarkable energy savings and retains high NO x removal. The mathematical models of the double and triple irradiation process are discussed.

Industrial demonstration plant for electron beam flue gas treatment

Abstract The positive results of the tests performed on laboratory and pilot installations in Poland, Japan, USA and Germany have led to decision concerning design and construction of the industrial demonstration plant for electron beam flue gas treatment. The planned flue gas purification installation will treat tlue gases from a block which consists of two Benson type boilers of power 56 MW e each supplying additional steam for heating purposes up to 40 MW th each. The 270 000 Nm 3 /h tlue gases (half of produced by the block) will be treated with efficiency of 90% for SO 2 and 70% for NO x . This meets Polish regulations which will be imposed in 1997. The technical and economical description of the project is presented in the paper.

CONCENTRATION OF LOW- AND MEDIUM-LEVEL RADIOACTIVE WASTES WITH THREE-STAGE REVERSE OSMOSIS PILOT PLANT

A study of the application of different membrane processes to nuclear technology has been conducted at the Institute of Nuclear Chemistry and Technology (INCT) for many years. One application of membrane methods involves the purification and concentration of liquid low- and medium-level radioactive wastes (LLLRWs and LMLRWs). The separation of radioactive model solutions as well as LLLRW and LMLRW samples has been examined with various reverse osmotic modules equipped with thin-composite polymeric membranes. On the basis of these investigations, membrane modules were selected for the pilot plant processing of liquid wastes from nuclear centers. A three-stage JP3RO reverse osmosis unit was constructed. The installation is described in this paper, and the results of preliminary pilot plant experiments are presented.

Technological development of eb flue gas treatment based on physics and chemistry of the process

Abstract Technological and engineering solutions of the process are based on the knowledge of the most important physical and chemical mechanism of SO 2 and NO x transformation due to radiation and thermal induced reactions, and aerosol formation. The data for process upscaling can be obtained on big industrial pilot plants; four of them for coal fired boilers have been constructed all over the world The feasibility studies for industrial installations have been already prepared.

A theoretical study on decomposition of carbon tetrachloride, trichloroethylene and ethyl chloride in dry air under the influence of an electron beam

Abstract New experimental data were published in literature regarding CCl 4 , C 2 HCl 3 and C 2 H 5 Cl decomposition in dry air under electron beam influence. Taking into account experimental data theoretical models of those species decomposition were established and computer simulations were performed by the authors of this work to find the kinetics of such processes. The results of the calculations and experimental data show that CCl 4 decomposition depends on delivered dose and initial CCl 4 concentrations. The calculation revealed that recombination of CCl + 4 and Cl − is the source of CCl 3 radicals and that reaction may have an important role in the process of CCl 4 decomposition. A theoretical model of C 2 HCl 3 decomposition in dry air under electron beam influence describes the decay of C 2 HCl 3 and the formation of several products such as Cl 2 , CCl 2 O, CO, CO 2 , HCl and C 2 HCl 3 O. The detailed comparison of experimental and theoretical data shows relatively good agreement in efficiency of C 2 HCl 3 decomposition process, but it can be achieved only with an assumption that the relation between rate constants of C 2 HCl 4 O intermediate product decomposition (C 2 HCl 3 O+Cl and COCl 2 +CHCl 2 ) should be around 20 and C 2 HCl 3 O oxidation rate should be not lower than 7.5×10 −11 cm 3 /mols. All those rate constants are not yet established experimentally. The results of the calculation of C 2 H 5 Cl decomposition and the data obtained experimentally were compared. The temperature, gas pressure, initial C 2 H 5 Cl concentration and dose range were equal in both cases. An elaborated model allow us to obtain quantitatively similar results as the experiments, but the degree of C 2 H 5 Cl decomposition for certain dose levels is significantly higher in experimental data. It is quite probable that some important processes have not been included to the theoretical model.

Pilot plant for flue gas treatment-continuous operation tests

Abstract Tests of continous operation have been performed on pilot plant at EPS Kaweczyn in the wide range of SO 2 concentration (500–3000 ppm).The bag filter has been applied for aerosol separation. The high efficiences of SO 2 and NO X removal, approximately 90% were obtained and influenced by such process parameters as: dose, gas temperature and ammonia stoichiometry. The main apparatus of the pilot plant (e.g. both accelerators) have proved their reliability in hard industrial conditions.

Pilot plant for electron beam flue gas treatment

Double stage gas irradiation (2 electron accelerators, 50 kW700 keV each) is the main technological principle employed in the Polish pilot plant (20,000 Nm3/h) constructed at EPS Kawȩczyn (low/medium sulphur coal). The pilot plant design is described in the paper.

Mechanism of 1,1-dichloroethylene decomposition in humid air under electron beam irradiation

Abstract Decomposition of 1,1-dichloroethylene (DCE) in humid air under electron beam irradiation has been investigated in the experiment. Inorganic compounds (CO, CO 2 ) and chloroacetyl chloride (CH 2 ClCOCl) were observed as main products. Modeling simulation was carried out by using computer code Kinetic (Bugaenko and Grichkin, Report ITEP 50, (1980) 1–19) and Gear method. 80 different species and 319 relevant reactions were considered. Calculation results agree well with the experiment. A possible reaction mechanism is proposed in this work. Cl − dissociative secondary electron attachment, oxygen negative ions and fast charge transfer of ionized carrier gas ions predominate in the initial stage of 1,1-DCE decomposition, while Cl radicals become significant after milliseconds’ irradiation.