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[en] The major emphasis of this report is to describe what has been learned about the generation, retention, and release of flammable gas mixtures in high-level waste tanks. A brief overview of efforts to characterize the gas composition will be provided. The report also discusses what needs to be learned about the phenomena, how the Unreviewed Safety Question will be closed, and the approach for removing tanks from the Watch List
[en] Fluor Daniel Northwest was authorized to address flammable gas issues by reconciling the unexplained surface level increases in Tank 241-SX-105 (SX-105, typical). The trapped gas evaluation document states that Tank SX-105 exceeds the 25% of the lower flammable limit criterion, based on a surface level rise evaluation. The Waste Storage Tank Status and Leak Detection Criteria document, commonly referred to as the Welty Report is the basis for this letter report. The Welty Report is also a part of the trapped gas evaluation document criteria. The Welty Report contains various tank information, including: physical information, status, levels, and dry wells. The unexplained waste level rises were attributed to the production and retention of gas in the column of waste corresponding to the unaccounted for surface level rise. From 1973 through 1980, the Welty Report tracked Tank SX-105 transfers and reported a net cumulative change of 20.75 in. This surface level increase is from an unknown source or is unaccounted for. Duke Engineering and Services Hanford and Lockheed Martin Hanford Corporation are interested in determining the validity of unexplained surface level changes reported in the Welty Report based upon other corroborative sources of data. The purpose of this letter report is to assemble detailed surface level and waste addition data from daily tank records, logbooks, and other corroborative data that indicate surface levels, and to reconcile the cumulative unaccounted for surface level changes as shown in the Welty Report from 1973 through 1980. Tank SX-105 initially received waste from REDOX starting the second quarter of 1955. After June 1975, the tank primarily received processed waste (slurry) from the 242-S Evaporator/Crystallizer and transferred supernate waste to Tanks S-102 and SX-102. The Welty Report shows a cumulative change of 20.75 in. from June 1973 through December 1980
[en] Different scale tests to explore the influence of fiberglass mesh on the fire behavior of expanded polystyrene (EPS) have been conducted. Micro scale combustion calorimeter to measure the heat release rate per unit mass, heat release capacity, and the total heat release of EPS and as well as the fiberglass for milligram specimen mass has been used. Cone colorimeter bench scale burning tests with the EPS specimens and EPS-fiberglass compound specimens have been carried out. The heat release rate per unit area, ignition times, and the derived minimum igniting heat fluxes were determined. Comparative burning tests on the fire spread tendency of EPS and EPS-fiberglass compound specimens have been carried out. It was established that the fiberglass mesh stabilizes the EPS fire as a wick fire due to the adherence of the melting polystyrene adheres to the fiberglass mesh and this causes an upwards fire spread.
[en] After the law by decree of the 12. June 2003, N 233 (ATEX Directive) and REACH regulation (Regulation EC n. 2907/2006 of the European Parliament), several industrial fields, also not chemical, need the flammability data for the substances used. Perhaps, many of these data, especially for compounds with not common uses, are not easy to collect. It would be helpful to provide prediction methods in order to calculate these data without any experimentation that sometimes results time consuming, expensive and practically impossible for all the commercial compounds. In this research the ASTM software CHETAH (CHEmical Thermodynamic And Hazard evaluation) has been used in order to compute the lower flammability limit (Li), the limiting oxygen concentration (LOC, using nitrogen as inert gas) as a function of temperature, the adiabatic flame temperature Tflame, the fundamental burning velocity (Su), the quenching distance (Qd), the minimum ignition energy (MIE) for esters and ethers, substances highly used in industry.
[it]Con il recepimento del Decreto Legislativo 12 giugno 2003, N. 233 (Direttiva ATEX) e del regolamento REACH (Regolamento CE n. 1907/2006 del Parlamento Europeo) e sorta la necessita per i responsabili di molte attivita industriali, anche non chimiche, di disporre dei dati di infiammabilita per le sostanze utilizzate. Purtroppo, molti di questi dati, soprattutto per i composti d'impiego non comunissimo, non sono facilmente reperibili. Sarebbe quindi auspicabile poter disporre di idonei metodi previsionali per ricavare, gia sulla carta, questi dati senza ricorrere necessariamente alla sperimentazione, talvolta lunga e costosa e praticamente irrealizzabile per tutte le sostanze in commercio. In questo lavoro e stata utilizzata la versione 8 del software CHETAH (CHEmical Thermodynamic And Hazard evaluation) comercializzato dall'ASTM per calcolare il limite inferiore di infiammabilita Li dell'ossigeno di sicurezza MOC (con azoto come gas inerte) in funzione della temperatura, la temperatura adiabatica di fiamma Tfiamma, la velocita di propagazione della fiamma Su, la distanza di estinzione Qd, l'energia minima di innesco MIE di esteri ed eteri, importanti sostanze di notevole interesse industriale.
[en] The release of a certain mass of fuel gas into the ambient atmosphere with negligible pressure difference whether deliberately or inadvertently results in the transient formation of flammable mixture zones for a period of time that represent a potential fire and explosion hazard. A numerical model based on the simultaneous solution of the equations of conservation of mass, momentum and energy has been developed to describe the development of such flammable zones when a finite quantity of fuel is released into the overlaying air within cylindrical vertical enclosures open to the outside atmosphere. Hydrogen disperses into the air extremely quickly with a strong temporal dependency on both horizontal and vertical directions. Comparison of the typical behavior of hydrogen dispersion with that of the lighter than air methane, the nearly buoyancy neutral ethylene and the much heavier than air propane is made. Some guidelines for reducing the fire and explosion hazards in such situations are presented. (authors)
[en] Available data on the ignition temperatures of magnesium and the Magnox alloys of interest in CEGB Magnox reactor operations have been reviewed. Two basic ignition modes, instantaneous where a continuing and high rate of temperature rise is applied to the metal and delayed where the metal is held at a predetermined ambient temperature until ignition occurs, are identified. (author)
[en] Flammability limits were measured for a number of olefinic and saturated fluoro-compounds in a 12 l spherical glass vessel. The obtained data together with the ones of previous studies have been analyzed based on the F-number scheme of flammability limits. The flammability limits of these compounds have been found to be explained very well by the present scheme of interpretation. The flammability limits are dependent upon distribution of F atoms in a molecule as well as upon F-substitution rate itself. It has been found that -O-CF3 group in a molecule conspicuously decreases the flammability of the compound, while -C-CF3 group does not much. For olefinic compounds, distribution of F atoms around double bonds markedly diminishes the flammability of the molecule.
[en] Radioactive waste solids can trap bubbles containing hydrogen that may pose a flammability risk if they are disturbed and hydrogen is released. Whether a release is a problem or not depends, among other things, on the hydrogen composition of the gas. This report develops a method for estimating the hydrogen composition of trapped bubbles based on waste properties
[en] Radioactive waste is scheduled to be retrieved from Hanford double-shell tanks AN-103, AN-104, AN-105 and AW-101 to the vitrification plant beginning about 2009. Retrieval may involve decanting the supernatant liquid and/or mixing the waste with jet pumps. In these four tanks, which contain relatively large volumes of retained gas, both of these operations are expected to induce buoyant displacement gas releases that can potentially raise the tank headspace hydrogen concentration to very near the lower flammability limit. This report describes the theory and detailed physical models for both the supernate decant and jet mixing processes and presents the results from applying the models to these operations in the four tanks. The technical bases for input parameter distributions are elucidated
[en] Complete text of publication follows. In this paper the influence of halloysite structure on the properties of melt-prepared polymer nanocomposites have been studied. Intercalation of halloysite (HLS) carried out in solution as well as by dry mechanochemical method has been investigated by vibrational spectroscopic techniques. Except of currently used modifiers (alkylamines, silanes), an intensive study of organo-clay nanocomplexes (with potassium-acetate, urea, formamide and acetamide) has been investigated and new structural models (as well as reaction pathways) were proposed. It was found that modification of halloysite by alkylamines as well as silanes did not lead to intercalated structure of halloysite. Mechanochemical treatment with urea, however, resulted in an intensive intercalation of halloysite. Surface activation of the mineral has been achieved by the thermal treatment of the complex. The impact of the intercalated structure of halloysite was confirmed by improving mechanical properties, as well as by reduction of flammability of PP/halloysite nanocomposites. The investigation of the structure of polymer nanocomposites based on intercalated halloysite confirmed considerable reduction of particle size and high degree of filler exfoliation. The achieved results confirmed that there is a potential for future utilisation of natural halloysites for production of exfoliated polymer nanocomposites with outstanding end use properties.