[en] This report documents the construction of a 0.914-m (36-in.)-dia. shock tube on the New Mexico State University caompus. Highly variable low-grade explosions can be simulated with the shock tube. We plan to investigate the response of nuclear facility ventilation system components to low-grade explosions. Components of particular interest are high-capacity, high efficiency paticulate air (HEPA) filters. Shock tube construction details, operating principles, firing sequence, and preliminary results are reported

[en] The charging of 10-nm-class nanoparticles in an electrostatic precipitator (ESP) according to particle charging ratio has been investigated and compared to the diffusion effect of the nanoparticles. The competition between the charging probability and the diffusion loss effect determines the collection efficiency of nanoparticles in the ESP. The collection efficiency of nanoparticles decreased continuously with decreasing particle diameter. This indicates that the partial charging effect of 10-nm-class nanoparticles is more dominant than their diffusion loss effect in the ESP for nanoparticles in the particle size range of less than 10 nm. The charging ratios based on unipolar diffusion charging calculations were in good agreement with the experimental collection efficiencies for nanoparticles less than 10 nm in diameter

[en] As the parameters of expressing the severity of back discharge, the degraded value of the field intensity, E, and the positive and negative ionic current densities, J+ and J-, are proposed, based on the charging and charge-neutralization processes in the bi-ionized field. Then, a bipolar current probe for measuring J+ and J- is described with its probe theory and some of the measuring results. Finally, the experimental verifications of the relationships holding between the charge and performance degradation factors and the probe-measured values of J+ and J- are presented. Although the laboratory results cannot immediately be extended to the practical plants, the bipolar current probe seems to provide one of the useful means for diagnosis of back discharge severity. (orig.)

[en] Problems associated with the removal of dust in working environments include the access of air to a suction plant, the ducting to a central pumping unit, filtering out of toxic constituents and the discharge to the atmosphere. With large installations, sound proofing, heat emission and cost effectiveness are additional factors. In the course of time, filters become clogged which reduces their effectiveness and increases the power requirements. A pressure manometer method is illustrated which enables an electrical contact to be activated to signal when filters need cleaning. For effective suction, the pipe entry must be as near as possible to the source of the dust. Some concentration and flow direction isometric patterns are illustrated to show the effect of distance on suction effects. (G.C.)

[en] Process for changing the filters of ventilation systems in a radioactive substances processing plant, by means of an ensemble comprising (a) a filtration chamber with an opening that can be closed by a first removable cover, (b) a box with an opening and a second removable cover, (c) a device for overlapping the first and second cover, (d) a device placed in the box for holding the overlapping covers when removed from the corresponding openings and (e) a mobile stand, in the box moving from a first position in which it can house a filter from the filtration chamber and transferred to the case, to a second position in which the overlapping covers can be placed back over the openings when a filter is in position

[en] The aim of the present work is to investigate the capability of a Wire-to-Square Tube Electrostatic Precipitator (or WST-ESP) to collect submicron particles using a Dielectric Barrier Discharge (DBD). A parametric study is carried out to evaluate the effects of four control variables that might affect the collection efficiency of the WST-ESP: diameter of the corona wire electrode, width of the ground electrode and the area of the tube section. The experimental data show that the wire diameter has a negligible effect on the WST-ESP collection characteristics. However, better overall performances can be obtained by putting in parallel several WST-ESPs with reduced section. The extension of the ground electrode and its discretization increase the collection efficiency.

[en] A method is described in which the essential characteristics of the removal of dust particles from an air stream are combined according to the electrostatic principle with a dust precipitator method based on mechanical filtration. The gas is passed through an electrostatic charger zone and then through a fibre filter (electrically neutral). The filter is cleaned by temporarily introducing a gas flow under high pressure in the opposite flow direction. Equipment to perform the method is described in great detail. (HP)

[en] Fibrous prefilters extend the service life of HEPA filters by removing most of the larger airborne particles. Such prefilters, however, are less effective in removing submicron particles until they are well loaded and a substantial pressure drop exists. We propose for HEPA prefilter service a radically new design of two-stage electrostatic precipitator (ESP) which is under development in our laboratory. It has the advantages of washability, efficiency largely independent of aerosol particle size, and very low pressure drop, all of which are common to conventional ESP's. In addition, however, the efficiency of the new design is improved by an order of magnitude or more over conventional ESP's. Moreover, the new design appears to be largely or entirely sparkproof, an important consideration in the filtration of combustible aerosols

[en] The collection efficiency of electrostatic precipitators for the submicron particles ranging from 0.1 to 1 μm and ultrafine particles smaller than 0. lμm is below the requirements of new PM2.5 emission regulations. In this work, numerical and experimental studies were conducted to examine the effect of discharge and collecting electrode geometries on the ion density and electric field profiles and consequently their effect on the particle surface charge and collection efficiency. The collection efficiency prediction was based on a modified Deutsche's equation after calculation of three dimensional electric field and ion density profiles. Whereas, the particle surface charge was obtained from diffusion and field charging models. Results show that the collection efficiency of fine particles for the spike-type discharge electrode when compared to the conventional wire-type was improved. Experimental validations were conducted on a bench scale electrostatic precipitator for total and partial collection efficiency of particles ranging in size from 0.01 to 20 μm and the results indicated that the model can be effectively applied for prototype design, modification, and scale-up of collecting and discharge electrodes.

[en] Document available in abstract form only. Full text of publication follows: A major component has failed in an active vessel ventilation system, which has been running successfully for the last 25 years or so. The failed component is one of two Electrostatic Precipitators housed in a sealed concrete cell. The remaining running ESP could fail at any time. The systems overall clean-up capability has to be restored. A solution has been determined by the use of a bespoke metal filter unit. The discussion presents the issues and challenges associated with the solution. (author)