[en] The Submerged-Bed Scrubber (SBS) is a novel air cleaning device that has been investigated by Pacific Northwest Laboratory (PNL) for scrubbing off gases from liquid-fed ceramic melters used to vitrify high-level waste (HLW). The concept for the SBS was originally conceived at Hanford for emergency venting of a reactor containment building. The SBS was adapted for use as a quenching scrubber at PNL because it can cool the hot melter off gas as well as remove over 90% of the airborne particles, thus meeting the minimum particulate decontamination factor (DF) of 10 required of a primary scrubber. The experiments in this study showed that the submicron aerosol DF for the SBS can exceed 100 under certain conditions. A conventional device, the ejector-venturi scrubber (EVS), has been previously used in this application. The EVS also adequately cools the hot gases from the melter while exhibiting aerosol removal DFs in the range of 5 to 30. In addition to achieving higher DFs than the EVS, however, the SBS has the advantage of being a passive system, better suited to the remote environment of an HLW processing system. The objective of this study was to characterize the performance of the SBS and to improve the aerosol capture efficiency by modifying the operating procedure or the design. A partial factorial experimental matrix was completed to determine the main effects of aerosol solubility, inlet off-gas temperature, inlet off-gas flow rate, steam-to-air ratio, bed diameter and packing diameter on the particulate removal efficiency of the SBS. Several additional experiments were conducted to measure the influence of the inlet aerosol concentration and scrubbing-water concentration on aerosol-removal performance. 33 refs., 17 figs., 14 tabs

[en] Performance correlations to design and operate the submerged bed scrubber were developed for various applications. Structural design procedure outlined in this report focuses on off-gas scrubbing for HLW vitrification applications; however, the method is appropriate for other applications

[en] Operation of a submerged bed scrubber has been characterized well enough to accurately estimate the collection efficiency for aerosols in an off-gas treatment system. The device has the advantages of a high degree of reliability and minimal control requirements. Correlations have been developed that allow direct specification of the design variables that are required to achieve a desire collection efficiency. The decontamination factors achievable through proper design and efficient operation are well within the acceptable range for a primary scrubber in nuclear off-gas treatment systems

[en] A major mission of the Hanford Defense Waste Program is to achieve permanent disposal of Hanford defense wastes with safe, environmentally acceptable, and cost-effective disposal methods which meet applicable regulations. To achieve this mission, the Defense Waste Management Plan (DWMP) establishes, as an objective, that the high-level waste be immobilized prior to shipment to a geologic repository. The Hanford Waste Vitrification Plant (HWVP) Program has been established to accomplish this objective. The goal of the HWVP is to vitrify pretreated waste in borosilicate glass, cast the glass into stainless steel canisters, and store the canisters at Hanford until they are shipped to a Federal Geologic Repository. This document contains the results of research activities conducted by Pacific Northwest Laboratory (PNL) during fiscal year 1986 that pertain to the preparation of feed for the vitrification process. The ultimate goal of this work is to establish a feed preparation procedure that will result in melter feeds with acceptable chemical and rheological properties. The high-level waste slurry received at the HWVP facility will undergo several processing steps before it can be fed to the ceramic melter. These steps include slurry concentration, treatment with formic acid (to improve slurry rheology), and the addition of glass frit. Additional feed concentration may also be required following addition of the frit. The laboratory experiments that were conducted during FY 1986 included three single-variable scoping studies and three larger, multivariable tests. These tests are described. 40 refs., 59 figs., 41 tabs