Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/28—Treating solids
  • G21F9/34—Disposal of solid waste
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/28—Treating solids
  • G21F9/30—Processing
  • G21F9/301—Processing by fixation in stable solid media
  • G21F9/302—Processing by fixation in stable solid media in an inorganic matrix
  • G21F9/304—Cement or cement-like matrix

Definitions

• the present invention relates to engineered cementitious contaminant barriers and to containers for storage of solid hazardous waste materials. More particularly, the present invention is directed to 0 containers and contaminant barriers prepared from cementitious materials capable of isolating contaminants, including toxic and radioactive waste materials, from a substantially uncontaminated environment.
• the cementitious barriers include compounds capable of adsorbing, absorbing, 5 chemically reacting with, bonding with, or otherwise trapping contaminants in the form of liquids, dissolved ions, and gases which might otherwise penetrate or leach through the barrier.
• the public has become more sensitive to the environment and the effect of hazardous and toxic waste materials on the environmental ecosystem.
• the public has recognized the need and 5 desirability of being free from exposure to toxic wastes and other hazardous chemicals and chemical by-products.
• Ground water contamination not only 0 effects the health and safety of humans, but also other forms of plant and animal life. Ground water contamination can result from direct introduction of harmful chemicals into the water source. In such cases, the problem is usually remedied by identifying th3 source of contamination and prohibiting future disposal of the waste without adequate waste treatment.
• nuclear waste materials are some of the most dangerous because their damage is permanent and they can remain radioactive for extremely long periods of time. Much of the radioactive waste materials which needs to be disposed of includes refuse from nuclear weapons plants, civilian nuclear power plants, and medical industry sources.
• plutonium waste from weapons plants decays by emitting alpha particles. Alpha particles do not even penetrate paper. As a result, the plutonium waste materials from weapons plants may be handled without protective clothing and pose no danger, as long as they remain sealed. Nevertheless, plutonium is extremely toxic and very long-lived.
• the Waste Isolation Pilot Project (“WIPP") site near Carlsbad, New Mexico, is one possible radioactive waste disposal site.
• the WIPP 5 site was excavated in a massive underground salt formation.
• Underground salt formations, such as the WIPP site, are considered as possible permanent radioactive waste disposal sites because of the long-term stability of the underground formation and because the salt strata has a low water
• the underground rooms are filled with the waste containers and back-filled with a grout material to fill as much empty
• C0 2 carbon dioxide gas
• Radioactive materials including spent fuel
• the following concentrating methods have been suggested: evaporation of the liquids, fixation of radioisotopic elements by solids, precipitation of radioisotopic elements by solids, precipitation of radioisotopic elements from the waste liquids, and calcination of the waste liquids.
• the contaminant barrier or container should be made of a nonmetal or other material which intrinsically does not corrode and produce gases;
• the contaminant barrier should prevent contaminant liquids, dissolved ions, or gases from escaping or permeating the barrier;
• the contaminant barrier or container should be of a material which "self-heals" upon contact with an aqueous solution
• the contaminant barrier should be made of a material having a record of long term geologic stability.
• the present invention is directed to engineered cementitious contaminant barriers and containers.
• 2o cementitious contaminant barriers and containers are formed by positioning a hydraulic cement composition into a predetermined configuration and then hydrating the cement composition without substantial mechanical mixing of the cement and water.
• 25 may be positioned into the configuration before hydrating.
• the contaminant barriers of the present invention are capable of isolating contaminants, including toxic and radioactive waste materials, from a substantially uncontaminated environment.
• the barriers may be
• waste storage and disposal containers prepared in a variety of configurations including, but not limited to, waste storage and disposal containers, in situ barrier walls, pipes, tanks, wells, or envelopes.
• contaminant barriers enable contaminant barriers to be engineered for effective isolation of a wide variety of different contaminants, including materials such as highly toxic and radioactive waste materials.
• the term "getter” includes materials which adsorb, absorb, chemically react, ionically bond, trap, attract, or otherwise bind to selected liquids, gases, or ions. Zeolites and layered clays are examples of typical getters which might be used in the present invention to form contaminant barriers.
• the contaminant barrier is preferably engineered or designed such that a sufficient quantity and type of getters are added to account for the anticipated liquid, gas, or ion contaminant generation by the waste material over the life of the waste.
• the getters may be mixed with the hydraulic cement composition prior to forming the contaminant barrier.
• the contaminant barrier may contain one or more carefully positioned getter layers combined with one or more layers of cement.
• the contaminant barriers within the scope of the present invention are intended to provide a boundary or barrier which separates the contaminated environment from the unconta inated environment.
• the present invention includes in situ barriers for isolating hazardous waste materials from the environment.
• the present invention also includes waste containers in which the contaminant barriers form the container walls.
• Such containers may be divided into two general categories: (l) empty containers into which contaminants are added after the container is formed; and (2) containers which are prepared by surrounding contaminants with one or more getters and powdered hydraulic cement, compressing the cement and getter around the contaminants, and allowing at least a portion of the hydraulic cement to hydrate.
• the cementitious barriers preferably undergo some hydration to close the cement pore structure and to provide mechanical strength.
• the amount of hydration may vary from a very nominal amount to extensive hydration depending upon the desired properties and characteristics of the final _
• the cementitious barrier may even be hydrated from exposure to ambient water in the environment such as water vapor in the air or from 5 ground water in an underground storage facility.
• gypsum a hydrated calcium sulphate, CaS0 4 »2H 2 0
• ettringite a calcium sulphoaluminate, 3CaO»Al 2 0 3 »3CaS0 4 »31H 2 0
• zeolites a calcium sulphoaluminate, 3CaO»Al 2 0 3 »3CaS0 4 »31H 2 0
• zeolites or gypsum containing water (such as zeolite X and zeolite Y) , or other compounds containing water in a crystalline form.
• the compounds are combined with the powdered hydraulic cement prior to forming the cementitious contaminant barrier. Subjecting the zeolites or gypsum in the waste
• clays for instance, cancrinite, a zeolite, and hydrotalcite, a clay, are capable of releasing
• Carbonates can enhance the strength, chemical stability, and durability of the final cementitious contaminant barrier.
• J2 selectively release the compounds of interest.
• contaminant includes liquids, ions, or gases for which isolation by the cementitious barrier is desired.
• Contaminants include solid, substantially solid, semisolid, liquid, and gaseous waste as well as liquids, ions, or gases generated by the waste. Contaminants include toxic and radioactive waste, as well as nonhazardous materials for which isolation by the barrier is desired.
• the waste containers within the scope of the present invention are preferably prepared by surrounding solid hazardous waste with a layer of powdered hydraulic cement and then compressing the cement around the solid waste. As with the contaminant barriers, the outer surface of the compressed hydraulic cement is then hydrated in order to close the pore structure and to provide mechanical strength. The amount of hydration may vary from a very nominal amount to extensive hydration depending upon the desired strength characteristics of the final waste container.
• solid hazardous waste includes solid, substantially solid, and semisolid materials which may contain varying amounts of water.
• solid hazardous waste includes hazardous waste materials typically contained in steel waste containers, with or without the waste container.
• waste containers which include conventional 55 gallon steel drums and other similar storage containers, may individually be included within the scope of the term “solid hazardous waste.”
• the waste containers of the present invention is directed to containers for solid hazardous waste, as opposed to liquid hazardous waste.
• the waste material is preferably substantially solid or semisolid.
• the water content of the solid hazardous waste may range from anhydrous waste materials to waste materials saturated with water. According to government regulations, the amount of free liquid associated with the waste is preferably less than about a pint per 55 gallon drum. /O
• Hydraulic cements used within the scope of the present invention are inexpensive, geologically and environmentally stable, and do not produce gases.
• more than c one layer of powdered hydraulic cement may be used.
• an outer layer of Portland cement may surround an inner layer of expansive and fast reacting high alumina cement.
• Suitable getters may be mixed with the powdered hydraulic cement.
• one or more getter layers 0 may be used with one or more cement layers.
• Pressure compaction processes including isostatic compression, are preferably used to position the hydraulic cement and getters into the desired cementitious barrier configuration. Thereafter, the hydraulic cement is _ preferably hydrated.
• the container may be hydrated by soaking it in an aqueous solution.
• the aqueous solution 0 would diffuse into the container and hydrate the cement to an average depth in the range from about zero to several feet, and preferably in the range from about 0.25 inches to about 3 inches, depending on the exposure time.
• sufficient hydration may be obtained by exposure with C0 2 in a high relative humidity. Regardless of the extent of outer surface hydration, it is important that the inner powdered hydraulic cement remain in a substantially unhydrated state. If aqueous solution were to breach the outer layer, the unhydrated inner cement layer would be available to react with the water.
• the hazardous waste containers are prepared by compressing the hazardous waste within a layer of powdered hydraulic cement, the void space within the container is minimized.
• the hazardous waste materials are essentially compacted to a high density inside a strong and stable container.
• novel contaminant barriers and waste containers of the present invention have several advances over the prior art, including: constructed of materials which do not intrinsically corrode to produce gases; utilize liquid, ion, or gas getters; are self-healing upon contact with an aqueous solution; do not require high temperature vitrification processes; and are relatively inexpensive to manufacture.
• Figure 1 is a partial cut-away perspective view of a waste container having walls that are contaminant barriers within the scope of the present invention.
• Figure 2 is a cross-sectional perspective view of another waste container having walls that are contaminant /
• barriers within the scope of the present invention showing a "getter” layer surrounding the , waste material.
• Figure 3 is a partial cross-sectional view of another possible contaminant barrier within the scope of the present invention showing multiple "getter” layers surrounding the waste material.
• Figure 4 is a partial cut-away perspective view of yet another waste container having walls that are contaminant barriers within the scope of the present invention.
• the present invention provides novel cementitious contaminant barriers and waste containers useful for containment of waste materials including highly toxic and radioactive waste materials.
• the cementitious contaminant barriers within the scope of the present invention are formed by positioning a hydraulic cement composition into a predetermined configuration and then hydrating the cement composition.
• One or more liquid, ion, or gas getters may be positioned into the configuration before hydrating.
• the getters are capable of binding or absorbing undesirable liquids, ions, or gases which externally penetrate the barrier or which internally leak from contained waste material surrounded by the barrier.
• the contaminant barriers within the scope of the present invention provide a barrier which separates a contaminated environment from an uncontaminated environment.
• the present invention includes in situ barriers for isolating large volumes of waste materials, as well as smaller waste containers.
• Such containers may be divided into two general categories: (1) preformed containers having lids; and (2) containers which are prepared by compressing hydraulic cement and at least one getter around waste material and allowing at least a portion of the hydraulic cement to hydrate.
• Containers within each of the general categories above may include contaminant barriers prepared with (a) a mixture of powdered hydraulic cement and a single getter;
• Hazardous waste container 10 is prepared by compressing substantially unhydrated powdered hydraulic cement 12 around solid hazardous waste 14, followed by hydrating outer surface layer 16 of the powdered hydraulic cement.
• Waste container 10 includes a mixture 12 of at least one liquid, ion, or gas getter and powdered hydraulic cement.
• the mixture 12 is compressed around solid hazardous waste 14.
• the outer surface layer 16 of the cement mixture is subsequently hydrated.
• outer surface layer 16 of the waste containers illustrated in Figures 1 and 2 may vary from as little as about 0.001 inches to as much as 100 inches or more. In most cases, the thickness will range from about 0.25 inches to about 3 inches. Desired strength characteristics often dictate the thickness of the hydrated outer surface layer. In some cases, natural water vapor in the atmosphere may hydrate a thin outer surface layer prior to depositing the waste container in an underground storage site. More complete hydration would then occur over the years as ground water contacts the waste container.
• waste containers within the scope of the present invention may be prepared in a variety of different shapes.
• triangular, rectangular, hexagonal, and many / other geometric cross-sectional configurations may be used.
• Waste containers within the scope of the present invention may also be prepared by compressing powdered hydraulic cement around the solid hazardous waste and thereafter applying a layer of cement paste over the compressed powdered hydraulic cement. Aggregates, such as fibers, may be added to the powdered hydraulic cement or to the cement paste to provide desired mechanical properties.
• a getter layer containing one or more getters around waste material compress a cement layer containing a powdered hydraulic cement composition around the getter layer, and then hydrate the cement composition. Any number of cement layers and getter layers can be included in such a containment system.
• Figure 3 illustrates one possible waste container 20 within the scope of the present invention having a getter layer 22 surrounding a quantity of waste material 24.
• Outer wall 26 includes substantially hydrated cement.
• Figure 4 illustrates another possible cementitious contaminant barrier configuration 30 in which multiple layers of liquid, ion, or gas getters 32A and 32B are mixed within a hydraulic cement composition layer 34.
• Contaminant barriers within the scope of the present invention may be prepared with a single barrier layer comprising a mixture of one or more liquid, ion, or gas getters and a hydraulic cement composition. The outer surface of this single layer would then be partially hydrated to provide mechanical strength.
• Aggregates may also be incorporated into one or more hydraulic cement layers of the contaminant barriers within the scope of the present invention to obtain desired structural or mechanical characteristics.
• the void space within the waste container is substantially reduced.
• the waste materials are essentially "precrushed" inside the container walls.
• the waste containers can be made so that the whole is much closer to equilibrium with the ground without the need for further compaction, grouting, or sealing.
• the fewer number of void spaces within the waste containers enables the ground to reach equilibrium density faster when the underground storage room collapses.
• the problems with ground water seeping into void spaces are reduced.
• FIG. 5 illustrates another possible hazardous waste container within the scope of the present invention.
• the waste container 40 shown in Figure 4 has a removable lid 42.
• the contaminant barrier forming the container wall includes a getter layer 44 having at least one liquid, ion, or gas getter.
• a layer of hydrated cement 46 provides mechanical strength to the waste container.
• the lid 42 serves to seal the container after a quantity of hazardous waste is placed inside the container.
• the lid preferably includes a getter layer 44 to prevent passage of contaminants through the lid. It is anticipated that cement paste or mortar may be used to seal the lid 42 with the container 40. In this way, the lid and container / ___
• the cement paste preferably includes the getters included within the container wall.
• the cementitious contaminant barriers include at least one getter.
• getters are materials which adsorb, absorb, chemically react, ionically bond, trap, attract, or otherwise bind to selected liquids, gases, or ions.
• the getters may be mixed with a powdered hydraulic cement composition prior to forming the contaminant barrier.
• one or more getter layers may be used to form the contaminant barrier.
• getters including zeolites, layered clays, and similar compounds, are included in the cementitious contaminant barrier to remove contaminants which might leach from waste material or otherwise penetrate the cementitious barrier. In those cases where many different types of contaminants may need to be isolated by the cementitious barrier, then more than one getter may be required to adequately contain the contaminants.
• Table 1 A few examples of common getters which may be used in connection with the present invention are listed in Table 1.
• Zeolites are an important class of getters used within the scope of the present invention.
• Zeolites are aluminosilicate framework minerals having a general formula (1) :
• n is the cation valence. They are characterized by their open structures that permit exchange of ions or molecules. Both natural and synthetic zeolites find wide application as ion exchangers, adsorbents, and catalysts. The ion exchange and molecular sieve properties of zeolites /.
• zeolites One important use of zeolites is the removal of radioactive cesium and strontium from waters contaminated with these elements. Because of their differing structures, particular zeolites can be used as molecular sieves to capture molecules of different sizes and shapes.
• zeolites may also be used as getters for ions, liquids, organics, and gasses such as H 2 and C0 2 . Mixtures of different zeolites and clays may be used to prevent a wide variety of different ions and molecules from escaping the waste container.
• Zeolite A has the following typical oxide formula: Na 2 O»Al 2 O 3 »2SiO 2 »4.5H 2 0.
• Zeolite A has a highly charged framework which will selectively adsorb thallium, silver, strontium, zinc, cadmium, mercury, lead, and barium over calcium.
• 90 Sr a common nuclide in nuclear explosion fallout with a half life of 28 years is preferentially removed in the presence of calcium ions. This zeolite is not effective for trivalent ions.
• Zeolite X has the following typical oxide formula: Na 2 0»Al 2 0 3 »2.5Si0 2 »6H 2 0. Zeolite X is preferred for higher valent ions such as iron, chromium, uranium, lanthanides, and actinides. The ion exchange of the actinides is irreversible if the temperature is above -85 ⁇ C. Neither Zeolite A nor
• Zeolite X is stable in acidic environments with protons as the cations.
• Zeolite Y has the following typical oxide formula: Na 2 0 «Al 2 0 3 »4.8Si0 2 »8.9H 2 0. Zeolite Y has more silicon in the framework (Si/Al -3) . As a result, it is more stable in acidic conditions. Cation exchange tends to be faster but less complete than for zeolite
• Chabazite has the following typical oxide formula: CaO «Al 2 0 3 »4Si0 2 «6.5H 2 0. Chabazite is important because calcium is less selectively exchanged than for the above zeolites. For example, the following cation selectivity has been reported: Tl * > K * >Ag * > Rb * > NH 4 * > Pb 2* > Na + - Ba 2* > Sr 2* > Ca 2* > Li * .
• Chabazite can be made in the acid form.
• Mordenite has the following typical oxide formula: Na 2 O «Al 2 O 3 «10SiO 2 «6H 2 O. Mordenite, also known as Zeolon, has been used to isolate cesium 137 and radioactive strontium ( 90 Sr) . The hydrogen form selectively absorbs NO ⁇ . Mordenite can be made in the acid form.
• Clinoptilolite has the following typical oxide formula: (Na 2 ,K 2 )O»Al 2 O 3 »10SiO 2 »8H 2 O. Clinoptilolite nas a strong preference for ammonium ions and also prefers strontium over calcium.
• High silica content molecular sieves such as silicalite and ZSM-5, may also be used in acidic environments. They do not have high exchange capacities for cations, but will adsorb organic molecules. Boron can be substituted for silicon to give a molecular sieve with a large neutron capture cross section.
• Arsenates, iodates, sulfides, sulfates, selenides, selenates, and fluorides are anions, and in general, will not be selectively adsorbed by zeolites unless they react with a cation, such as lead, which is already within the zeolite framework to form a substantially insoluble compound. These compounds can also be absorbed in hydrotalcite clays as well.
• Mixtures of different zeolites may be used to absorb a wider variety of hazardous waste ions and gases than using a single zeolite or layered clay material. Mixtures of zeolites and/or clays can improve the efficiency of "getting" or sieving out specific hazardous substances.
• zeolites are a few currently preferred zeolite mixtures. It should be noted that due to the large concentrations of calcium present when the zeolite mixtures are combined with hydraulic cement compositions, it is possible a "mass action" effect could in some cases overwhelm the selectivity of the noted zeolites for other ions.
• Anorthite referred to above, is known as an "early condensate.” Early condensates are formed at high LI
• the terrestrial abundance of the early condensates is similar to their cosmic abundance. Examples include iron with 12% nickel, which condenses at 1500"K; diopside, CaMgSi 2 0 6 , which condenses at 1450°K; and anorthite, CaAl 2 Si 2 0 8 , which condenses at 1350*K. It is for this reason that Fe, O, Mg and Si make up more than 90% of the earth.
• Zeolite X one of the most open zeolites, can be easily exchanged with Ca or Sr and directly converted by vitrification to the very stable anorthite phase Ca(Sr)Al 2 Si 2 0 8 .
• Selective exchange for Sr followed by condensation to anorthite at elevated temperatures may be a useful way to deal with °°Sr decay which generates considerable heat.
• Layered Clays are another important class of getters used within the scope of the present invention.
• the layered clays can be used to absorb large organic molecules, gases, cations, and even Z
• Kaolinite has the following typical oxide formula: Al 2 Si 2 0 5 (OH) 4 .
• Kaolinite is a two-layered sheet clay composed of a Si0 4 tetrahedra sheet and an
• Smectite and Vermiculite has the following typical oxide formula: Al 2 Si 4 O 10 (OH) 2 .
• Vermiculite have three layer sheets with one octahedra layer between two tetrahedral layers. Substitutions of Mg 2 *, Ca 2 *, and Fe 3 * for aluminum can be used to change the charge of the framework and structural features.
• Hydrotalcite is an unusual anion exchanger clay which can be modified to adsorb various negatively charged ions.
• the anions can be large metal oxide anionic aggregates, simple inorganic anions such as selenate (Se0 4 2" ) , or organic in nature.
• Some gas getters may be specifically included within the contaminant barriers of the present invention for the purpose of trapping certain gasses that might be generated by waste materials. Gaseous formation of hydrogen and carbon dioxide from organics and metals in radioactive and other hazardous wastes and waste containers is a serious problem. Of course, unhydrated cement will act as a C0 2 getter, but some zeolites such as hydroxy cancrinite, and some nonzeolite compounds such as hydrotalcite clays may 13 also be included in the hazardous waste container to function as C0 2 getters.
• Zeolites impregnated with palladium may be used to adsorb and remove hydrogen gas.
• Palladium is one of the most effective hydrogen getters known in the art.
• Other compounds such as FeTi(H ⁇ ) and LaNi 5 (H ⁇ ) are also good hydrogen getters at high pressure.
• FeTi(H 12 ) is formed by trapping 0.1 grams H 2 /ml which is greater than the density of liquid hydrogen (0.07 grams H 2 /ml) .
• LaNi 5 (H 6 ) is formed by trapping 0.09 grams H 2 /ml.
• the waste material to be contained Before selecting specific getters to be included in a cementitious contaminant barrier, the waste material to be contained must be identified.
• the waste material is preferably assayed and characterized to determine the nature and quantity of contaminants per unit mass.
• a low-level radioactive waste form may consist of 50 liters of soil containing only 1 gram of mercury or radioactive cesium that causes the entire mass to be classified as hazardous.
• Specific hazardous materials that have a particularly high toxicity and/or a propensity or probability of diffusion or leaching through the containment barrier are preferably further identified and characterized.
• the potential of generating and diffusing or leaching a maximum amount of each contaminant of interest per unit mass of waste is determined.
• a cementitious contaminant barrier is then engineered and fabricated with one or more getters disbursed therein (either randomly or in layers) having the capacity of trapping the maximum quantity of potential contaminants of interest.
• getters are selected for inclusion in cementitious contaminant barrier depending on the type and quantity of contaminants for which there is concern of diffusion or leaching through the barrier.
• the amount of the getter necessary to trap specific contaminants must be calculated.
• the getter 5 be capable of calculating the amount getter required by taking into consideration the molecular or formula weight of the getter, the amount of potential contaminant, and the getter efficiency.
• the ultimate fabrication method and design based used will depend upon the economics of 0 fabrication which include the manufacturing process costs and the getter costs.
• Example 1 o This example calculates the amount of hydrogen getter required to absorb hydrogen generated by five kilograms of hazardous waste material within.10 cubic feet of mass. It is assumed the hazardous waste material is 5% hydrogen by weight.
• the hydrogen gas (H 2 ) is preferably converted to a - stable hydride or hydroxide at low temperature.
• One possible mechanism for converting the H 2 is the use of palladium and/or silver cations highly dispersed in a zeolitic framework.
• the palladium is preferably loaded into the zeolite by 0 ion exchange as Pd(NH 3 ) 4 * 2 .
• All molecular sieves or zeolites containing ten or- twelve rings are suitable for this method of exchange.
• ion exchange using aqueous solutions of halide salts of 5 palladium or dry impregnation (incipient wetness) is used.
• Coexchange with transition metals such as cobalt or iron is used to enhance the dispersion of the palladium(O) phase.
• sodium zeolite Y Na 56 (A10 2 ) 56 (Si0 2 ) 136
• sodium zeolite Y Na 56 (A10 2 ) 56 (Si0 2 ) 136
• hydrothermal crystallization see D.W. Breck and E.M. Flanigen, "Molecular Sieves,” Soc. Chem. Ind.. London 1968) , p. 47 and H. Kacirek and H. Lechert, J. Phys. Che . 1975, vol. 79, p. 1589
• purchased commercially Lide LZ-Y52
• the zeolite sample is washed, filtered, and subsequently dehydrated in a flow of oxygen (570-870"K) at a heating rate of l'K/min to form the active absorber.
• Example 2 This example calculates the amount of hydrogen getter required to absorb hydrogen generated by five kilograms of hazardous waste material within 10 cubic feet of mass according to the procedure of Example 1, except that iron or cobalt is further substituted for the sodium in the sodium zeolite Y. This has been demonstrated to increase the room temperature reactivity of palladium with hydrogen
• the zeolite is first exchanged with iron, then dehydrated under oxygen at 623°K under oxygen, and then ion exchanged with Pd(NH 3 ) 4 *2 (0.01 M) . Alternatively, ion ⁇ exchange procedure can be reversed.
• the resulting zeolite has the following chemical analysis: Na 29 Fe 38 Pd 10 (AlO 2 ) 56 (SiO 2 ) l36 (Formula weight 13418). ith the same assumptions as in Example 1, 25 moles or 335.5 kg of zeolite containing the same amount of palladium (26.6 kg) is required to convert the hydrogen.
• Example 3 This example calculates the amount of hydrogen getter required to absorb hydrogen generated by five kilograms of hazardous waste material within 10 cubic feet of mass according to the procedure of Example 1, except that silver and copper exchanged zeolites are used.
• the silver zeolitic phase undergoes reduction with hydrogen below 100°C (see H.K. Beyer and P.A. Jacobs in "Metal Microstructures in Zeolites", ed. P.A. Jacobs, et al., Elsevier, Amsterdam, p. 95, 1982.)
• the copper zeolite is reduced below 200*C, although the lower limit is not well established. This is readily done with small pore size zeolites, such as zeolite A, as well as zeolite X or Y.
• compositions can be used.
• the latter has a formula weight of 15997.
• 500/36 13.9 moles (222.2 kg) of zeolite are required at 50% efficiency.
• the copper may assist in the reduction, but has not been included as a backup factor.
• the amount of silver needed is 500 moles or 53.95 kg.
• Example 4 This example calculates the amount of ion getter required to absorb mercury contained in five kilograms of hazardous waste material within 10 cubic feet of mass. It is assumed the hazardous waste material contains IS- Hg 2 *.
• sodium zeolite A is prepared by conventional hydrothermal crystallization or purchased commercially (Linde 5A) . Sodium zeolite A has the z.
• the family of cements known as hydraulic cements used in the present invention is characterized by the hydration products that form upon reaction with water. It is to be distinguished from other cements such as polymeric organic cements.
• powdered hydraulic cement as used herein, includes clinker, crushed, ground, and milled clinker in various stages of pulverizing and in various particle sizes.
• powdered hydraulic cement also includes cement particles which may have water associated with the cement; however, the water content of the powdered hydraulic cement is preferably sufficiently low that the cement particles are not fluid.
• the water to cement ratio is typically less than about 0.25.
• Examples of typical hydraulic cements known in the art include: the broad family of Portland cements (including ordinary Portland cement without gypsum) , calcium aluminate cements (including calcium aluminate cements without set regulators, e.g.. gypsum) , plasters, silicate cements (including ⁇ dicalciu silicates, tricalcium silicates, and mixtures thereof) , gypsum cements, phosphate cements, magnesium oxychloride cements, as well as mixtures of hydraulic cements.
• Hydraulic cements generally have particle sizes ranging from about 0.1 ⁇ m to about 100 ⁇ m.
• the cement particles may be gap-graded and recombined to form bimodal, trimodal, or other polymodal systems to improve packing efficiency.
• a trimodal system having a size ratio of about 1:5:25 and a mass ratio of about 22:9:69 (meaning that 21.6% of the particles, by weight, are of size 1 unit and 6.9% of the particles, by weight, are of size 5 units and 69.2% of the particles, by weight are of size 25 units) can theoretically result in 85% of the space filled with particles after packing.
• Another trimodal system having a size ratio of about
• a bimodal system having a size ratio of 0.2:1 and a mass ratio of 30:70 (meaning that 30% of the particles, by weight, are of size 0.2 units and 70% of the particles, by weight, are of size 1 unit) can theoretically result in 72% o the space filled with particles after packing.
• Another bimodal system having a size ratio of 0.15:1 and a mass ratio of 30:70 can result in 77% of the space filled with particles after packing.
• cement paste includes cement mixed with water such that the hydration reaction has commenced in the cement paste. Cement pastes are continuous, fluid mixtures having a measurable viscosity.
• Pressure compaction processes such as dry pressing and isostatic pressing, may be used to compress powdered hydraulic cement and getters in the form of waste containers described above. Dry pressing consists of compacting powders between die faces in an enclosed cavity. Pressures can range from about 500 psi to greater than 100,000 psi in normal practice.
• additives are mixed with the powdered hydraulic cement to make molding easier and to provide sufficient strength so that the article does not crumble upon removal from the press.
• Suitable additives preferably neither initiate hydration nor inhibit later hydration of the hydraulic cement.
• Grading the cement particles and getters may also provide a certain fluidity to the cement powder and getters during compressing.
• it may be useful to lubricate the cement powder with an oil emulsion, according to techniques known in the art, to facilitate the lateral movement among the particles.
• Suitable emulsions may be prepared using nonaqueous, volatile solvents, such as acetone, methanol, and isopropyl alcohol.
• cement particles are formed by crushing and grinding larger cement clinker pieces, the individual particles have rough edges. It has been found that rounding the edges of the cement particles enhances their ability to slide over each other, thereby improving the packing efficiency of the cement particles. Techniques for rounding cement particles known in the art may be used.
• Isostatic pressing is another powder pressing 0 technique in which pressure is exerted uniformly on all surfaces of the cement article being formed.
• the method is particularly suitable in forming of symmetric shapes, and is similarly employed in the shaping of large articles which could not be pressed by other methods. 5
• the powdered mix is encased in _a pliable rubber or polymer mold.
• the mold is then preferably sealed, evacuated to a pressure between 0.1 atm and 0.01 atm, placed in a high-pressure vessel, and gradually pressed to the desired pressure.
• An essentially 0 noncompressible fluid such as high-pressure oil or water is preferably used. Pressures may range from 100 to 100,000 psi.
• the forming pressure is preferably gradually reduced before the part is removed from the mold.
• Vibrational compaction techniques may be used to help pack the hydraulic cement composition mix into molds and into in situ barrier configurations.
• vibrational compaction processes the powdered hydraulic cement particles and getter particles 0 are typically compacted by low-amplitude vibrations. Inter-particle friction is overcome by application of vibrational energy, causing the particles- to pack to a density consistent with the geometric and material characteristics of the system and with the conditions of
• vibration packing processes Packed densities as high as 100% of theoretical are possible using vibration packing processes.
• the term "theoretical packing density" is defined as the highest conceivable packing density achievable with a given powder size distribution.
• the theoretical packing density is a function of the particle size distribution.
• Vibration packing processes may also be combined with pressure compaction processes to more rapidly obtain the desired packing densities or even higher packing densities.
• Typical vibration frequencies may range from about 1 Hz to about 20,000 Hz, with frequencies from about 100 Hz to about 1000 Hz being preferred and frequencies from about 200 Hz to about 300 Hz being most preferred.
• Typical amplitudes may range from about one half the diameter of the largest cement particle to be packed to about 3 mm, with amplitudes in the range from about one half the diameter of the largest cement particle to about 1 mm. If the amplitude is too large, sufficient packing will not occur.
• the frequency may be varied as necessary to control the speed and rate of packing.
• the vibration amplitude is preferably in the range from about 10 ⁇ m to about 500 ⁇ m.
• aggregates commonly used in the cement industry with the powdered hydraulic cement prior to hydration examples include sand, gravel, pumice, perlite, and vermiculite.
• aggregates commonly used in the cement industry with the powdered hydraulic cement prior to hydration.
• aggregates include sand, gravel, pumice, perlite, and vermiculite.
• One skilled in the art would know which aggregates to use to achieve desired characteristics in the final cementitious waste container.
• the differently sized aggregates have particle sizes in the range from about 0.01 ⁇ m to about 2 cm.
• salt may be included as an aggregate material with the powdered hydraulic cement to enhance the thermodynamic compatibility of the container with its storage environment.
• One overriding goal in developing suitable waste storage containers is to design a container which will be as thermodynamically compatible with the storage environment as possible so that the container will quickly reach thermodynamic equilibrium with its environment. For example, the more chemically compatible the storage container is to its storage environment, the closer the container is to thermodynamic equilibrium with its environment and the lower the driving force for chemical change.
• hydration as used herein is intended to describe the chemical reactions that take place between the cement and water.
• the chemistry of hydration is extremely complex and can only be approximated by studying the hydration of pure cement compounds.
• cement hydration involves complex interrelated reactions of the each compound in the cement mixture.
• Portland cement With respect to Portland cement and the waste containers, the principal cement components are dicalcium silicate and tricalciu silicate.
• Portland cement generally contains smaller amounts of tricalcium aluminate (3Ca ⁇ «Al 2 0 3 ) and tetracalcium aluminum ferrite (4Ca ⁇ »Al 2 0 3 »FeO) .
• the hydration reactions of the principal components of Portland cement are abbreviated as follows:
• the principal cement components using Portland cement for the contaminant barriers are about 55% tricalcium silicate (3Ca0 «Si0 2 , also referred to as C 3 S) , about 25% dicalcium silicate (2CaO «Si0 2 , also referred to as C 2 S) , about 10% tricalcium aluminate (3CaO»Al 2 0 3 , also referred to as C 3 A) , and about 8% tetracalcium aluminoferrite (4CaO»Al 2 0 3 »Fe 2 0 3 , also referred to as C 4 AF) .
• some minor components are also present in Portland cement.
• the hydration reaction of the two silicates with water produces calcium silicate hydrates (C-S-H) and calcium hydroxide.
• C-S-H make the largest contribution to the strength of the hydrated cement.
• Tricalcium aluminate also forms a hydrate, but it contributes little to the strength of the cement.
• the hydration reaction of tricalcium aluminate is so rapid that it has to be controlled by gypsum.
• the presence of tricalcium aluminate is, however, advantageous in the preparation of Portland cement. Tetracalcium alu inoferrite is not particularly important except that it contributes to the characteristic gray color of Portland cement.
• Hydration With Gaseous and Liouid Water It is within the scope of the present invention to hydrate the powdered hydraulic cement after the cement particles have been compressed into a hazardous waste container. Hydration is accomplished without mechanical mixing of the cement and water. Thus, diffusion of water (both gaseous and liquid) into the compressed hazardous 30
• waste container is an important hydration technique within the scope of the present invention.
• hydration occurs immediately after the container is compressed. In other cases, initial hydration may occur from water vapor in the atmosphere, with a more complete hydration occurring from ground water exposure after the container is placed in underground storage.
• the gas When hydration is achieved by contacting the cementitious waste container with gaseous water, the gas may be at atmospheric pressure; however, diffusion of the water into the article, and subsequent hydration, may be increased if the gaseous water is under pressure.
• the pressure may range from 0.001 torr to about 2000 torr, with pressures from about 0.1 torr to 1000 torr being preferred, and pressures from about 1 torr to about 50 torr being most preferred. Even though water vapor is introduced into the cement compact, it is possible that the water vapor may immediately condense into liquid water within the pores of "the cement compact. If this happens, then gaseous water and liquid water may be functional equivalents.
• Atomized liquid water may, in some cases, be used in place of gaseous water vapor.
• atomized water is characterized by very small water droplets, whereas gaseous water is characterized by individual water molecules. Gaseous water is currently preferred over atomized water under most conditions because it can permeate the pore structure of the compressed cementitious container better than atomized water.
• the temperature during hydration can affect the physical properties of the hydrated cement container. Therefore, it is important to be able to control and monitor the temperature during hydration. Cooling the cement container during hydration may be desirable to control the reaction rate.
• the gaseous water may also be combined with a carrier gas.
• the carrier gas may be reactive, such as carbon dioxide or carbon monoxide, or the carrier gas may be inert, such as argon, helium, or nitrogen.
• Reactive carrier gases are useful in controlling the morphology and chemical composition of the final cementitious container. Reactive carrier gases may be used to treat the hazardous waste container before, during, and after hydration.
• the partial pressure of the water vapor in the carrier gas may vary from about 0.001 torr to about 2000 torr, with from about 0.1 torr to about 1000 torr being preferred, and from about 1 torr to about 50 torr being most preferred.
• An autoclave may be conveniently used to control the gaseous environment during hydration. It is also possible to initially expose the cement container to water vapor for a period of time and then complete the hydration with liquid water. In addition, the cement container may be initially exposed to water vapor and then to carbon dioxide.
• Heating the gaseous water will increase the rate of hydration. Temperatures may range from about 25°C to about 200 * C. It should be noted that the temperature at which hydration occurs affects certain physical characteristics of the final cement container, especially if an additional silica source is added. For example, when hydration temperature is greater than about 50 ' C, the formation of a hydrogarnet crystalline phase is observed, and when the hydration temperature is greater than about 85°C other crystalline phases are observed.
• C0 2 can be used to prepare contaminant barriers and containers having improved water resistance, surface toughness, and dimensional stability. These results may be obtained by exposing the contaminant barrier to an enriched C0 2 atmosphere while rapidly desiccating the cement container.
• the C0 2 is preferably at a partial pressure greater than its partial pressure in normal air.
• Aqueous solutions may also be used to hydrate the cementitious contaminant barriers and hazardous waste containers within the scope of the present invention.
• aqueous solution refers to a water solvent having one or more solutes or ions dissolved therein which modify the hydration of hydraulic cement in a manner different than deionized water. For instance, it is possible to simply immerse the unhydrated cement container in lime water to achieve adequate hydration.
• Lime water is an aqueous solution containing Ca 2* and OH ' ions formed during the hydration reactions. Because of the 31 presence of hydroxide ions, lime water typically has a pH in the range from about 9 to about 13.
• aqueous solutions such as extracts from cement paste, silica gel, or synthetic solutions may be used to hydrate the contaminant barriers of the present invention.
• Other ions in addition to Ca 2* and OH * such as carbonates, silica, sulfates, sodium, potassium, iron, and aluminum, may also be included in aqueous phase solutions.
• solutes such as sugars, polymers, water reducers, and superplasticizer may be used to prepare aqueous solutions within the scope of the present invention.
• a typical aqueous solution within the scope of the present invention may contain one or more of the following components within the ranges set forth in Table II:
• ppm refers to the standard dosage rate used in the concrete industry
• Apparatus capable of monitoring the concentrations of ions in the aqueous solution include pH meters and spectrometers which analyze absorbed and emitted light. e. Addition of Hydrated Crystals
• gypsum a hydrated calcium sulphate, CaS0 4 «2H 2 0
• ettringite a calcium sulphoa 1 uminate
• These water-containing compounds are preferably added to the powdered hydraulic cement prior to forming the cementitious contaminant barrier. Subjecting the contaminant barrier to mild heating, typically less than about 100"C, causes water to be released. The water is then capable of partially hydrating the hydraulic cement. High green strengths are obtained using this technique. Cementitious contaminant barriers formed in this manner would also be excellent water getters.
• Example 5 an engineered waste container having a contaminant barrier was prepared.
• a waste material was identified that had the potential of generating 0.1 moles of hydrogen gas per kilogram of waste by way of oxidation of iron.
• Twenty kilograms of the waste (having a unit density of 2.0 grams/cm 3 ) was selected to be contained in a preformed containment system with a separate lid.
• the container was manufactured to have an interior capacity of 10 liters.
• the container was in the shape of a box having an interior dimension of approximately 22 centimeters per side.
• 7.3 kilograms of ordinary Portland cement was combined in a dry powder mixer with 300 grams of LaNi 4 ⁇ l g 3 .
• the LaNi AI Q 3 has the capacity to absorb up to three moles of hydrogen gas under ambient conditions.
• the resultant dry powder mixture was placed in a mold.
• the mold had a latex exterior with an inside steel cubic mandrel having a cross section of 22 x 22 centimeters.
• the cement/LaNi 4 T AI Q ⁇ mixture was placed within the latex mold.
• the mold was then sealed and placed in an isostatic press and pressurized to 30,000 psi for 30 seconds and released.
• an engineered waste container having a contaminant barrier is prepared.
• a waste material is identified that has the potential of generating 0.1 moles of hydrogen gas per kilogram of waste by way of oxidation of iron.
• One hundred (100) kilograms of the waste, having a unit density of 2.0 grams/cm 3 are selected to be contained in a preformed containment system with a separate screw lid.
• the container is manufactured to have an interior capacity of 50 liters.
• the preformed container is designed to be a cylinder with an interior diameter of 21 centimeters and an interior height of 36 centimeters. It is further designed to have an outside diameter of 23 centimeters and an overall height of 38 centimeters.
• the container is also designed to have a nearly homogenized layer of LaNi 47 Al 03 , a hydrogen gas getter, approximately 0.1 centimeter thick on the interior of the container.
• the container is formed using the following procedure: An appropriate mold and mandrel having a cross-section of 21 centimeters is selected. 1500 grams of LaNi 4 ⁇ Al 03 having an average particle size of 5 microns are uniformly placed in the mold and isostatically pressed to 10,000 psi. The mold is then released, a larger mold housing is selected, and 21.2 kilograms of ordinary white Portland cement are uniformly placed in the mold. The mold and contents are then vibrated for one minute and evacuated. The mold is then sealed and isostatically pressed to 30,000 psi.
• the "green" container has a total wall thickness of approximately 1.1 centimeters with an interior diameter of 21 centimeters.
• the container is placed in a chamber which is subsequently evacuated and backfilled with an aqueous solution.
• the aqueous solution is extracted from cement paste prepared with ordinary Portland cement having a water to cement ratio of 1.0.
• the container is then allowed to cure for 24 hours. Once the container has cured, the waste material is placed in the container, the preformed screw lid is coated with a 0.3 water to cement ratio cement paste containing 5% LaNi 4 ⁇ l g 3 , and the lid is screwed into place.
• Example 7 an engineered waste container having a contaminant barrier was prepared.
• a waste material was identified that had the potential of generating 0.2 moles of NH 4 * and leaching a maximum of 0.1 moles of mercury per kilogram of waste. Ten kilograms of this waste were to be contained. The waste had an average density of 1.6 grams/cm 3 after compaction to 20,000 psi.
• the container was designed to have 400 grams of zeolite A and 850 grams of zeolite F mixed with 4500 grams of ordinary Portland cement. _.
• a mold was selected having a cubic shape with an interior dimension of 18 centimeters and an exterior diameter of 20 centimeters.
• the 10 kilograms of waste were 5 placed in the interior cavity of the mold and 5750 grams of uniformly blended powder were evenly distributed in the exterior cavity of the mold and pressurized to 20,000 psi.
• Ultrasonic measurement indicated that the resultant container had a uniform cementitious wall of approximately
• the "green" container wall was formed to an engineered voids content of 19%.
• the container was hydrated by initially spraying the entire container with an aqueous solution of water, CaOH, and Si0 2 . Subsequently, approximately one-third liter of
• aqueous solution was uniformly sprayed on the exterior of the container in order to create a hydrated bond of the packed wall to an average depth of 0.75 centimeters. Approximately 0.25 centimeters wall thickness was substantially unhydrated.
• an engineered waste container having a contaminant barrier is prepared.
• a waste material is identified and characterized having 0.2 moles of cesium and
• a cementitious cylindrical container is designed having an approximate interior diameter of 20 centimeters
• the container is manufactured as follows: 1100 grams of fi
• Kaolinite and 730 grams of Zeolite Y are mixed together as dry powders, both having an average particle size less than 10 microns.
• a matrix mold is selected having a diameter of approximately 25 centimeters and a height of 15 centimeters.
• a cylindrical mandrel is placed inside the mold having a cross-sectional diameter of 20 centimeters.
• Approximately 2500 grams of ordinary Portland cement are placed in the mold.
• the mold is then sealed and pressurized in an isostatic press to 10,000 psi.
• the mold is released and the 1830 gram getter mixture is evenly placed in the cavity around the packed cement layer and the mold.
• the mold is sealed again and pressurized to 15,000 psi and released.
• an additional 2500 grams of cement are placed in the cavity between the getter layer and the exterior mold wall.
• the mold is sealed and pressurized to 30,000 psi and released.
• the mandrel is removed and the "green" container has an interior diameter of 20 centimeters and the wall has a cross section of approximately 0.4 centimeters of cement on the outside of the container, a sandwiched getter layer of approximately 0.5 centimeters, and a final layer of 0.4 centimeters of cement as the interior wall of the container.
• a lid is made using a similar process. The 20 kilograms of waste are placed inside the container. The lid is screwed into place and sealed with a cement paste containing kaolinite and zeolite Y. The entire container with waste is then immersed in water for 15 minutes. The container is removed and allowed to hydrate and form an integral barrier to the hazardous waste and particularly to the cesium and nickel contaminants.
• Example 9 an engineered waste container having a contaminant barrier is prepared.
• 150 kilograms of hazardous waste having a moisture content of less than 5% and an iodide content of 0.1 moles per kilogram of waste are selected for containment.
• the waste has a density of 1.6 grams/cm 3 when compacted at 25,000 psi.
• the waste occupies a volume of 94 liters in a pressed cylindrical shape having a diameter of 20 centimeters and a height of 75 centimeters.
• the waste is placed in an appropriately selected latex mold, and a dry powder mixture of 10 kilograms of cement and 9 kilograms of zeolite PbX is placed uniformly around the waste.
• the mold is sealed and pressurized to 20,000 psi.
• the mold is then released and opened.
• 20 kilograms of dry powdered cement is placed around the consolidated mass.
• the mold is then sealed and pressurized again to 25,000 psi and released.
• the final wall has a "green" density, as determined by ultrasound, of approximately 2.4 grams/cm 3 .
• Example 10 an engineered waste container having a contaminant barrier is prepared.
• a waste material is identified and characterized having 0.1 moles of cesium, 0.1 moles of iron, and 0.05 moles of cobalt per kilogram of waste.
• the waste has a unit density of approximately 2 grams/cm 3 .
• a preformed container having multiple layers of getter and cement is formed using a latex mold and an isostatic press.
• the inner layer is compressed around a cylindrical mandrel having a diameter of 20 centimeters and a height of 24 centimeters.
• the inner layer includes approximately 7200 grams of dry white Portland cement (free of gypsum) and is consolidated at 25,000 psi to an approximately thickness of 0.5 centimeters.
• a getter layer is then pressed onto the inner layer at a pressure of about 25,000 psi.
• the getter layer includes a pre-blended dry powder mixture of 6000 grams of clinoptilolite, 900 grams of LaNi 4 ⁇ I Q 3 , and 3000 grams of dry gypsum-free cement.
• An exterior layer is made by uniformly distributing 7200 grams of gypsum-free, white
• the container is then immersed in aqueous solution saturated with lime for ten minutes, removed, and allowed to cure for six hours.
• the container has a final outside diameter of 23 centimeters and an interior diameter of 20 centimeters.
• a lid is prepared using a similar process.
• a 0.3 water to cement ratio paste is used as a bonding agent to chemically bond the lid to the container and seal the waste in the containment system.
• an engineered waste container having a contaminant barrier is prepared.
• a pre-processed, mixed hazardous waste form is identified and characterized as having 0.2 moles of radioactive cesium, 0.1 moles of benzene, and 0.5 moles of mixed alcohol per kilogram of waste.
• the pre-processed waste is placed in a spherical latex mold approximately 42 centimeters in diameter and isostatically compressed to 30,000 psi. Subsequently, a dry mixture of 15 kilograms of montmorillonite, 4.2 kilograms of phlogopite (mica) , and 5 kilograms of ordinary
• Portland cement is uniformly placed around the compacted waste inside the spherical mold.
• the mold is sealed and pressed to 20,000 psi and released.
• An additional 7 kilograms of bi-modal, gap-graded ordinary Portland cement without gypsum is uniformly placed around the previously compacted spherical mass inside the mold.
• the mold is 41 sealed and pressed to 25,000 psi and released.
• the sphere is placed in sea water and allowed to cure underwater.
• a waste container having a contaminant barrier is prepared by encasing hazardous waste with powdered hydraulic cement containing a liquid, ion, or gas getter.
• Ordinary Portland cement and about 200 grams of zeolite A are mixed.
• the hazardous waste material is known to include approximately 50 grams of Hg 2* .
• the hazardous waste and the cement/zeolite mixture are positioned within a pliable polymeric cylindrical mold such that from 1 to 2 inches of the cement/zeolite mixture surrounds the waste material.
• the cement/zeolite mixture also fills irregularities around the exterior surface of the hazardous waste materials.
• the waste container is then compressed at a pressure of 30,000 psi.
• the hazardous waste container is then hydrated by immersing the container in saturated lime water, maintained at a temperature between 22 ⁇ C and 25 * C at atmospheric pressure during hydration. Testing to determine leach rates of the cured hazardous waste container show that no measurable amounts of mercury escape the waste container.
• Example 13 a waste container is prepared by encasing hazardous waste with a getter layer and a cement layer.
• the hazardous waste material is known to include approximately 50 grams of Hg 2* .
• Ordinary Portland cement and about 200 grams of powdered zeolite A are used in this example.
• the hazardous waste and the zeolite are positioned within a pliable polymeric cylindrical mold such that a zeolite layer surrounds the waste material.
• a binder may be used to hold the powdered zeolite together. Binders known to those skilled in the art, including hydraulic cement, may be used.
• the zeolite layer fills irregularities around the exterior surface of 4t
• a layer of the ordinary Portland cement is then positioned around the zeolite layer in the mold.
• the cement and zeolite layers are isostatically compressed at a pressure of 35,000 psi.
• the outer surface of the Portland cement layer is then hydrated by immersion in saturated lime water, maintained at a temperature between 22°C and 25"C at atmospheric pressure during hydration. Testing to determine leach rates of the cured hazardous waste container show that no measurable amounts of mercury escape the waste container.
• Example 14 A waste container is prepared according to the procedure of Example 13, except that the hazardous waste is encased with a layer containing multiple liquid-, ion, or gas getters rather than a single getter.
• the hazardous waste material is known to include a variety of radioactive and nonradioactive hazardous constituents. Mordenite, Chabazite, Faujasite, and Linde 5A are selected as suitable liquid, ion, or gas getters. The amount of each respective getter is calculated according to the general procedure outlined in Examples 1-4 above.
• Example 15 A hazardous waste container is prepared according to the procedure of Example 14, except that the various getters are graded by size to improve packing efficiency.
• Example 16 A hazardous waste container is prepared according to the procedure of Example 14, except that the hazardous waste is encased with multiple layers of liquid, ion, or gas getters rather than a single layer.
• the hazardous waste material is known to include a variety of radioactive and nonradioactive hazardous constituents including organic residues.
• Zeolite X, NaZSM5, Clinoptilolite, and Linde 5A are selected as suitable liquid, ion, or gas getters.
• the 1 amount of each respective getter is calculated according to the general procedure outlined in Examples 1-4 above.
• the hazardous waste and getters are positioned within a pliable polymeric cylindrical mold such that layer containing zeolite X surrounds the waste material. If necessary, a binder may be used to hold the zeolite X together. Binders known to those skilled in the art, including hydraulic cement, may be used. A second layer containing NaZSM5 is positioned around the zeolite X layer, followed by a third layer containing Clinoptilolite and a fourth layer containing Linde 5A. Finally, a layer of the ordinary Portland cement is then positioned around the getter layers in the mold. The cement and getter layers are isostatically compressed, and the outer cement layer is hydrated.
• Example 17 A waste container is prepared according to the procedure of Example 13, except that the hazardous waste is encased with multiple getter layers having mixtures of different getters.
• the waste material includes a variety of radioactive and nonradioactive hazardous constituents.
• Zeolon, zeolite X, chabazite, and Linde 5A are selected as suitable liquid, ion, or gas getters.
• the amount of each respective getter is calculated according to the general procedure outlined in Examples 1-4 above.
• the waste material and a first getter layer are positioned within a pliable polymeric cylindrical mold such that the first getter layer, containing a mixture of zeolon and zeolite X surrounds the waste material. If necessary, a binder may be used to hold the getter layer together.
• a second getter layer containing a mixture of chabazite and Linde 5A is positioned around the first getter layer.
• a layer of the ordinary Portland cement is then positioned around the getter layers in the mold. The cement and getter layers are isostatically compressed, and the outer cement layer is hydrated. ⁇ O
• a waste container is prepared by compressing a getter and a powdered hydraulic cement composition into a mold.
• the mold is capable of defining an internal cavity within the waste container.
• the container wall includes a layer containing the getter and a layer containing the cement composition.
• the hazardous waste container is designed to hold hazardous waste material which includes approximately 50 grams of Hg 2* .
• Ordinary Portland cement and about 200 grams of powdered zeolite A are used in this example.
• the zeolite A is positioned within a pliable polymeric mold and compressed to form a zeolite layer.
• a layer of the ordinary Portland cement is then positioned around the exterior surface of the zeolite layer.
• the cement is isostatically compressed.
• a removable lid for the waste container is prepared by compressing separate zeolite and hydraulic cement layers as described above. The Portland cement layers of the container and lid are then hydrated by immersion in saturated lime water.
• Example 19 A waste container is prepared according to the procedure of Example 18, except that a mixture of various liquid, ion, or gas getters is used rather than a single getter.
• the container wall includes a layer containing a mixture of various getters and a layer containing the cement composition.
• the waste container is designed to hold waste material having a variety of radioactive and nonradioactive hazardous constituents. Mordenite, Chabazite, Faujasite, and Linde 5A are selected as suitable liquid, ion, or gas getters. The amount of each respective getter is calculated according to the general procedure outlined in Examples 1-4 above. 7
• Example 20 A waste container is prepared according to the procedure of Example 19, except that the various getters are graded by size to improve packing efficiency.
• Example 21 A waste container is prepared according to the procedure of Example 18, except that the container wall includes multiple layers containing various getters and a layer containing the cement composition.
• the hazardous waste container is designed to hold waste material having a variety of radioactive and nonradioactive hazardous constituents. Mordenite, Chabazite, Faujasite, and Linde 5A are selected as suitable liquid, ion, or gas getters. The amount of each respective getter is calculated according to the general procedure outlined in Examples 1-4 above.
• a multi-layered waste container is prepared according to the procedure of Example 21, except that the outer layer of Portland Cement also contains a plurality of fibers wrapped around the compressed high alumina cement to improve the mechanical properties of the final hazardous waste container.
• Example 23 a multi-layered waste container is prepared according to the procedure of Example 21, except that the outer layer of Portland Cement also contains electrical and thermal conducting aggregates dispersed therein to improve the mechanical properties of the final hazardous waste container.
• Example 24 a cementitious contaminant barrier capable of preventing passage of radon gas is prepared in situ.
• the cementitious contaminant barrier is prepared at a site for a proposed building known to release unacceptably high levels of radon gas. Rather than pouring a concrete floor directly on compacted excavated ground, a
• a hazardous waste container is prepared by isostatically compressing powdered hydraulic cement surrounding solid hazardous waste materials.
• the solid hazardous waste and the ordinary Portland cement are positioned within a pliable polymer mold such that from 5 to 10 inches of powdered cement surrounds the solid waste.
• the Portland cement also fills irregularities around the exterior surface of the solid hazardous waste materials.
• the container is then compressed at a pressure of 35,000 psi. After compression, the cement container has a green density of 2.6 g/cm 3 .
• the hazardous waste container is hydrated by immersing the container in saturated lime water having a pH of about 12 for about 24 hours.
• the saturated lime water is prepared by dissolving CaO in water.
• the lime water is maintained at a temperature between 22°C and 25"C at atmospheric pressure during hydration.
• a hazardous waste container is prepared according to the procedure of Example 1, except that a layer of powdered high alumina cement is positioned adjacent the solid hazardous waste and a layer of ordinary Portland cement is positioned around the high alumina cement prior to isostatic compression.
• the high alumina cement also fills irregularities around the exterior surface of the solid waste materials.
• the thickness of the high alumina cement layer is maintained between 2 to 8 inches, and the thickness of the Portland cement layer is maintained between 2 to 8 inches.
• a hazardous waste container is prepared according to the procedure of Example 1, except that the compressed cement container is hydrated by immersing the container in a 10% aqueous phase solution for about 24 hours.
• the 10% aqueous phase solution is prepared by making a cement paste having a 0.4 water to cement ratio and mixing the cement paste for 5 minutes.
• the aqueous phase is extracted from the paste and diluted with water to form the 10% aqueous phase solution.
• a hazardous waste container is prepared according to the procedure of Example l, except that after isostatic compression, the hazardous waste container is hydrated by immersing the container in water for about 24 hours.
• Example 29 In this example a hazardous waste container is prepared according to the procedure of Example 1, except that after isostatic compression, the hazardous waste container is hydrated by immersing the container in water for about 24 hours and thereafter exposing the hazardous waste container to C0 2 while in a desiccating environment.
• Example 30 In this example a hazardous waste container is prepared according to the procedure of Example 1, except ⁇ 4
• the hazardous waste container is carbonated under autoclaving conditions at
• a hazardous waste container for high level nuclear waste is prepared according to the procedure of Example 1, except that the relative thickness of the cement compared to the quantity of waste materials is increased.
• a hazardous waste container is prepared by isostatically compressing powdered hydraulic cement surrounding solid hazardous waste materials.
• the solid hazardous waste and ordinary Portland cement are positioned within a pliable polymer mold such that from 5 to 10 inches of powdered cement surrounds the solid waste.
• the Portland cement also fills irregularities around the exterior surface of the solid hazardous waste materials.
• the container is then compressed at a pressure of 35,000 psi. After compression, the cement container has a green density of 2.6 g/cm 3 .
• a layer of cement paste approximately 3 inches thick is then placed around the compressed waste container.
• the hazardous waste container includes an inner layer of substantially unhydrated cement compressed about and in contact with the hazardous waste and a hydrated cement outer layer.
• Example 33 a multi-layered hazardous waste container is prepared by isostatically compressing powdered hydraulic cement surrounding solid hazardous waste materials.
• the solid hazardous waste and high alumina cement are positioned within a pliable polymer mold such that from 5 to 10 inches of powdered cement surrounds the _ solid waste.
• the powdered cement also fills irregularities around the exterior surface of the solid hazardous waste materials.
• the container is then compressed at a pressure
• the cement container After compression, the cement container has a green density of 2.6 g/cm 3 .
• the outer surface of the compressed high alumina cement is carbonated under autoclaving conditions at 100% relative humidity.
• An outer layer of Portland cement is 0 then positioned around the compressed high alumina cement and compressed at a pressure of 35,000 psi as described above.
• the outer layer of compressed Portland cement is hydrated by immersing the waste container in saturated lime
• the saturated lime water is prepared by dissolving CaO in water.
• the lime water is maintained at a temperature between 22 * c and 25"C at atmospheric pressure during hydration.
• Example 34 a multi-layered hazardous waste container is prepared according to the procedure of Example 9, except that the outer layer of Portland Cement also contains a plurality of fibers wrapped around the compressed high alumina cement to improve the mechanical
• Example 35 In this example, a multi-layered hazardous waste container is prepared according to the procedure of Example 9, except that the outer layer of Portland Cement also contains electrical and thermal conducting aggregates dispersed therein to improve the mechanical properties of the final hazardous waste container. __
• liquid, ion, or gas getters may be advantageously used in the design of contaminant barriers as molecular sieves to prevent specific waste constituents from passing through one layer into another. For instance, knowing the relative selectivities of various liquid, ion, and gas getters, one layer of the barrier may be selected to trap a specific ion or class of ions with additional layers selected to trap other ions.
• the present invention provides novel cementitious contaminant barriers and containers which are constructed of strong materials that do not intrinsically corrode to produce gases.
• the present invention also provides novel contaminant barriers which include liquid, ion, and gas getters.
• the present invention provides contaminant barriers constructed of materials which are self-healing upon contact with aqueous solution.
• the present invention further provides contaminant barriers which do not require high temperature vitrification processes.
• the present invention provides novel contaminant barriers which are inexpensive to manufacture.

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• 1991
  • 1991-07-19 AT AT91917485T patent/ATE151192T1/de active
  • 1991-07-19 AU AU86311/91A patent/AU8631191A/en not_active Abandoned
  • 1991-07-19 EP EP91917485A patent/EP0555238B1/fr not_active Expired - Lifetime
  • 1991-07-19 WO PCT/US1991/005100 patent/WO1992002024A1/fr active IP Right Grant
  • 1991-07-19 DE DE69125500T patent/DE69125500D1/de not_active Expired - Lifetime

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