Determination of halogen content in glass for assessment of melter decontamination factors

Melter decontamination factor (DF) values for the halogens (fluorine, chlorine, and iodine) are important to the Hanford Waste Vitrification Plant (HWVP) process because of the potential influence of DF on secondary-waste recycle strategies (fluorine and chlorine) as well as its impact on off-gas emissions (iodine). This study directly establishes the concentrations of halides-in HWVP simulated reference glasses rather than relying on indirect off-gas data. For fluorine and chlorine, pyrohydrolysis coupled with halide (ion chromatographic) detection has proven to be a useful analytical approach suitable for glass matrices, sensitive enough for the range of halogens encountered, and compatible with remote process support applications. Results obtained from pyrohydrolytic analysis of pilot-scale ceramic melter (PSCM) -22 and -23 glasses indicate that the processing behavior of fluorine and chlorine is quite variable even under similar processing conditions. Specifically, PSCM-23 glass exhibited a {approximately}90% halogen (F and Cl) retention efficiency, while only 20% was incorporated in PSCM-22 glass. These two sets of very dissimilar test results clearly do not form a sufficient basis for establishing design DF values for fluorine and chlorine. Because the present data do not provide any new halogen volatility information, but instead reconfirm the validity of previously obtained offgas derived values, melter DF values of 4, 2, and 1 for fluorine, chlorine, and iodine, respectively, are recommended for adoption; these values were conservatively established by a team of responsible engineers at Westinghouse Hanford Company (WHC) and Pacific Northwest Laboratory (PNL) on the basis of average behavior for many comparable melter tests. In the absence of further HWVP process data, these average melter DFs are the best values currently available

Critique of Hanford Waste Vitrification Plant off-gas sampling requirements

Off-gas sampling and monitoring activities needed to support operations safety, process control, waste form qualification, and environmental protection requirements of the Hanford Waste Vitrification Plant (HWVP) have been evaluated. The locations of necessary sampling sites have been identified on the basis of plant requirements, and the applicability of Defense Waste Processing Facility (DWPF) reference sampling equipment to these HWVP requirements has been assessed for all sampling sites. Equipment deficiencies, if present, have been described and the bases for modifications and/or alternative approaches have been developed

Automated krypton-85 gamma ray stack monitor

A Ge(Li) ..gamma..-ray detector, housed in a lead cave, was used in conjunction with a six-liter pressurized (60 psia) well spectroscopy cell to selectively detect /sup 85/Kr stack emissions. This system was calibrated so as to relate the 514 keV ..gamma..-ray counting rate to /sup 85/Kr concentration. Counting rate, or concentration, was continuously recorded using a count rate meter/strip chart recorder combination and was also time averaged over 15 minute intervals using a programmable multi-channel analyzer system with cassette readout. Being completely automated, this ..gamma..-analysis system required little more than liquid nitrogen service and data record retrieval throughout a four-month long sampling period. The sensitivity of this ..gamma..-ray analytical system was such as to achieve a minimum detectable /sup 85/Kr stack concentration of 2 ..mu..Ci/m/sup 3/ for 15 minute counting intervals

Off-gas characteristics of liquid-fed joule-heated ceramic melters

The off-gas characteristics of liquid-fed joule-heated ceramic melters have been investigated as a function of melter operational condition and simulated waste feed composition. The results of these studies have established the identity and behavior patterns of gaseous emissions, the characteristics of melter-generated aerosols, the nature and magnitude of melter effluent losses and the factors affecting melter operational performance. 8 figures, 16 tables

Off-gas characteristics of defense waste vitrification using liquid-fed Joule-heated ceramic melters

Off-gas and effluent characterization studies have been established as part of a PNL Liquid-Fed Ceramic Melter development program supporting the Savannah River Laboratory Defense Waste Processing Facility (SRL-DWPF). The objectives of these studies were to characterize the gaseous and airborne emission properties of liquid-fed joule-heated melters as a function of melter operational parameters and feed composition. All areas of off-gas interest and concern including effluent characterization, emission control, flow rate behavior and corrosion effects have been studied using alkaline and formic-acid based feed compositions. In addition, the behavioral patterns of gaseous emissions, the characteristics of melter-generated aerosols and the nature and magnitude of melter effluent losses have been established under a variety of feeding conditions with and without the use of auxiliary plenum heaters. The results of these studies have shown that particulate emissions are responsible for most radiologically important melter effluent losses. Melter-generated gases have been found to be potentially flammable as well as corrosive. Hydrogen and carbon monoxide present the greatest flammability hazard of the combustibles produced. Melter emissions of acidic volatile compounds of sulfur and the halogens have been responsible for extensive corrosion observed in melter plenums and in associated off-gas lines and processing equipment. The use of auxiliary plenum heating has had little effect upon melter off-gas characteristics other than reducing the concentrations of combustibles

Differential monitoring of tritium and carbon-14 compounds

A gaseous sampling system was developed to differentially collect all major volatile forms of tritium and carbon-14 according to chemical class. These chemical forms include: tritiated forms of water, hydrogen and organics; as well as /sup 14/C-containing carbon monoxide, carbon dioxide and organics. Sampling campaigns involving the use of this differential /sup 3/H and /sup 14/C collection system have been successfully conducted at a high level liquid waste solidification plant, at a spent fuel storage facility and in the vicinity of power reactors

LFCM (liquid-fed ceramic melter) processing characteristics of mercury

An experimental-scale liquid-fed ceramic melter was used in a series of tests to evaluate the processing characteristics of mercury in simulated defense waste under various melter operating conditions. This solidification technology had no detectable capacity for incorporating mercury into its borosilicate, vitreous, product, and essentially all the mercury fed to the melter was lost to the off-gas system as gaseous effluent. An ejector venturi scrubber condensed and collected 97% of the mercury evolved from the melter. Chemically the condensed mercury effluent was composed entirely of chlorides, and except in a low-temperature test, mercury chlorides (Hg{sub 2}Cl{sub 2}) was the primary chloride formed. As a result, combined mercury accounted for most of the insoluble mass collected by the process quench scrubber. Although macroscopic quantities of elemental mercury were never observed in process secondary waste streams, finely divided and dispersed mercury that blackened all condensed Hg{sub 2}Cl{sub 2} residues was capable of saturating the quenched process exhaust with mercury vapor. However, the vapor pressure of mercury in the quenched melter exhaust was easily and predictably controlled with an off-gas stream chiller. 5 refs., 4 figs., 12 tabs

Technology of off-gas treatment for liquid-fed ceramic melters

The technology for treating off gas from liquid-fed ceramic melters (LFCMs) has been under development at the Pacific Northwest Laboratory since 1977. This report presents the off-gas technology as developed at PNL and by others to establish a benchmark of development and to identify technical issues. Tests conducted on simulated (nonradioactive) wastes have provided data that allow estimation of melter off-gas composition for a given waste. Mechanisms controlling volatilization of radionuclides and noxious gases are postulated, and correlations between melter operation and emissions are presented. This report is directed to those familiar with LFCM operation. Off-gas treatment systems always require primary quench scrubbers, aerosol scrubbers, and final particulate filters. Depending on the composition of the off gas, equipment for removal of ruthenium, iodine, tritium, and noxious gases may also be needed. Nitrogen oxides are the most common noxious gases requiring treatment, and can be controlled by aqueous absorption or catalytic conversion with ammonia. High efficiency particulate air (HEPA) filters should be used for final filtration. The design criteria needed for an off-gas system can be derived from emission regulations and composition of the melter feed. Conservative values for melter off-gas composition can be specified by statistical treatment of reported off-gas data. Statistical evaluation can also be used to predict the frequency and magnitude of normal surge events that occur in the melter. 44 refs., 28 figs., 17 tabs

Minimum detectable activities of contamination control survey equipment

The Instrumentation External Dosimetry (I ED) Section of the Health Physics Department at the Pacific Northwest Laboratory (PNL) has performed a series of tests to determine the ability of portable survey instruments used at Hanford to detect radioactive contamination at levels required by DOE 5480.11. This semi-empirical study combines instrumental, statistical, and human factors as necessary to derive operational detection limits. These threshold detection values have been compared to existing contamination control requirements, and detection deficiencies have been identified when present. Portable survey instruments used on the Hanford Site identify the presence of radioactive surface contamination based on the detection of {alpha}-, {beta}-, {gamma}-, and/or x-radiation. However, except in some unique circumstances, most contamination monitors in use at Hanford are configured to detect either {alpha}-radiation alone or {beta}- and {gamma}-radiation together. Testing was therefore conducted on only these two categories of radiation detection devices. Nevertheless, many of the results obtained are generally applicable to all survey instruments, allowing performance evaluations to be extended to monitoring devices which are exclusively {gamma}- and/or x-ray- sensitive. 6 figs., 2 tabs