Chemically bonded ceramic radiation shielding material and method of preparation

Abstract

A composition of matter and method of forming a radiation shielding member at ambient temperatures in which the composition of matter includes a cold-fired chemically bonded oxide-phosphate ceramic cement matrix; with one or more suitably prepared and distributed radiation shielding materials dispersed in the cold-fired chemically bonded oxide-phosphate ceramic cement matrix.

Claims

.[.1. A composition of matter comprising: a chemically bonded oxide-phosphate based ceramic matrix; and a radiation shielding material, wherein the radiation shielding material is dispersed in the chemically bonded oxide-phosphate based ceramic matrix in an amount of 40%-75% by weight and the radiation shielding material is selected from the group consisting of barium oxide, barium sulfate, cerium oxide, tungsten, tungsten oxide, gadolinium, gadolinium oxide, depleted uranium oxide, wherein the oxide-phosphate based ceramic matrix is MgHPO43H2O (magnesium hydrogen phosphate trihydrate), or wherein the oxide-phosphate ceramic matrix includes at least two different metal phosphates..].

.[.2. The composition of matter of claim 1 wherein the at least two different metal phosphates are selected from the group consisting of KH.sub.2PO.sub.4 (potassium dihydrogen phosphate), MgHPO.sub.4 (magnesium hydrogen phosphate), Fe.sub.3(PO.sub.4).sub.2 (iron (II) phosphate), Fe.sub.3(PO.sub.4).sub.2.8H.sub.2O (iron(II) phosphate octahydrate), FePO.sub.4(iron(III) phosphate), FePO.sub.42H.sub.2O (iron(III) phosphate dihydrate) AlPO.sub.4aluminum phosphate, AlPO.sub.4.1.5H.sub.2O (aluminum phosphate hydrate), CaHPO.sub.4(calcium hydrogen phosphate), CaHPO.sub.4.2H.sub.2O (calcium hydrogen phosphate dihydrate), BiPO.sub.4(bismuth phosphate), CePO.sub.4(cerium(III) phosphate), CePO.sub.4.2H.sub.2O cerium(III) phosphate dihydrate), GdPO.sub.4.H2O (gadolinium phosphate hydrate), BaHPO.sub.4(barium hydrogen phosphate), and UPO.sub.4 (depleted uranium (U-238) phosphate)..].

.[.3. The composition of matter of claim 1 wherein the radiation shielding material is formed as at least one or more of the aggregates or powders dispersed in the oxide-phosphate ceramic..].

.[.4. The composition of matter of claim 1 wherein the at least two different metal phosphates are selected from the group consisting of magnesium hydrogen phosphate, iron(III) phosphate, aluminum phosphate, calcium hydrogen phosphate, bismuth phosphate, cerium(III) phosphate, gadolinium phosphate, and barium hydrogen phosphate..].

.[.5. The composition of claim 1, comprising at least two radiation-shielding materials to form a multiple layer structure, wherein the at least two radiation-shielding materials are in separate layers of the multiple layer structure..].

.[.6. A method of constructing chemically bonded oxide-phosphate based ceramic matrix radiation shielding at ambient temperature, comprising: providing a mixture of (a) magnesium oxide, or at least two a metal oxides selected from the group consisting aluminum oxide, magnesium oxide, iron(III) oxide; iron (II) oxide and calcium oxide; (b) a phosphate containing material; (c) a radiation shielding material selected from the group consisting of barium oxide, barium sulfate, cerium oxide, tungsten oxide, tungsten, gadolinium oxide, gadolinium, depleted uranium oxide; and (d) a sparsely soluble silicate selected from the group consisting of calcium silicate (CaSiO.sub.3), magnesium silicate (MgSiO.sub.3), barium silicate (BaSiO.sub.3), sodium silicate (NaSiO.sub.3), lithium silicate (LaSiO.sub.3), and serpentinite (Mg64.O10.{OH8}); adding an activator to the mixture; and allowing the mixture of the radiation shielding material, metal oxide, phosphate containing material in an amount of 40% -75% by weight and the sparsely soluble silicate to cure at ambient temperature..].

.[.7. The method of constructing a radiation shielding member at temperature conditions of claim 6 wherein curing occurs at less than 100 C. (one hundred degrees Celsius)..].

.[.8. The method of constructing a radiation-shielding member at ambient temperature of claim 6 wherein the phosphate containing material is phosphoric acid..].

.[.9. The method of claim 6 wherein the activator is water or an acid..].

.[.10. A mixture comprising: magnesium oxide, or at least two metal oxides selected from the group consisting of magnesium oxide, iron (III) oxide; iron (II) oxide and calcium oxide; a phosphate-containing material; a radiation shielding material selected from the group consisting of: barium oxide, barium sulfate, cerium oxide, tungsten, tungsten oxide, gadolinium, gadolinium oxide, and depleted uranium oxide; wherein the radiation shielding material is in an amount of 40%-75% by weight; and a sparsely soluble silicate selected from the group consisting of calcium silicate (CaSiO.sub.3), magnesium silicate (MgSiO.sub.3), barium silicate (BaSiO.sub.3), sodium silicate (NaSiO.sub.3), lithium silicate (LaSiO.sub.3), and serpentinite (Mg.sub.64.O.sub.10.{OH.sub.8}); wherein the composition forms a chemically bonded oxide phosphate ceramic matrix upon activation..].

.[.11. The mixture of claim 9 wherein the phosphate-containing material is potassium dihydrogen phosphates, phosphoric acid, or potassium monohydrogen phosphate..].

.[.12. The mixture of claim 9 wherein the metal oxide is magnesium oxide, and the phosphate-containing material is potassium dihydrogen phosphate; and the radiation shielding material is barium sulfate..].

.[.13. The mixture of claim 9 wherein the metal oxide is magnesium oxide, and the phosphate-containing material is potassium dihydrogen phosphate; and the radiation shielding material is depleted uranium oxide..].

.Iadd.14. A radiation-shielding composition, comprising: (1) a chemically bonded ceramic matrix, comprising: a) magnesium phosphate; and b) wollastonite; and (2) a radiation-shielding material in an amount of 40% to 75% dispersed in the chemically bonded ceramic matrix. .Iaddend.

.Iadd.15. The radiation-shielding composition of claim 14, wherein the magnesium phosphate; is formed from MgO (magnesium oxide) and KH.sub.2PO.sub.4 (monopotassium phosphate). .Iaddend.

.Iadd.16. The radiation-shielding composition of claim 15, wherein the MgO (magnesium oxide) is dead-burned magnesium oxide. .Iaddend.

.Iadd.17. The radiation-shielding composition of claim 14, further comprising a powder or fibers dispersed in the chemically bonded ceramic matrix. .Iaddend.

.Iadd.18. The radiation-shielding composition of claim 14, wherein the magnesium phosphate is MgHPO.sub.43H.sub.2O (magnesium hydrogen phosphate trihydrate). .Iaddend.

.Iadd.19. The radiation-shielding composition of claim 14, wherein the radiation-shielding material is selected from the group consisting of barite, barium sulfate, powdered annealed leaded glass, fibers of annealed leaded glass, barium oxide, cerium oxide, tungsten or a tungsten-containing compound, tungsten oxide, gadolinium, gadolinium oxide, depleted uranium oxide, iron oxide, bismuth or a bismuth-containing compound, boron or a boron-containing compound, aluminum oxide, zeolites, clinoptilotites, celestites, depleted uranium, and combinations thereof. .Iaddend.

.Iadd.20. A radiation-shielding member comprising the radiation-shielding composition of claim 14. .Iaddend.

.Iadd.21. The radiation-shielding member of claim 20, wherein the radiation-shielding member is configured for use as a radiation-shielding wall. .Iaddend.

.Iadd.22. The radiation-shielding member of claim 20, wherein the radiation-shielding member is a single layer structure. .Iaddend.

.Iadd.23. The radiation-shielding member of claim 20, wherein the radiation-shielding member comprises two layers, each of the two layers having a different radiation-shielding property. .Iaddend.

.Iadd.24. The radiation-shielding member of claim 23, wherein the two layers comprise different radiation-shielding materials. .Iaddend.

.Iadd.25. A method of constructing a radiation shielding member, comprising: (1) forming a mixture comprising: (a) MgO (magnesium oxide); (b) KH.sub.2PO.sub.4 (monopotassium phosphate); (c) wollastonite; and (d) a radiation-shielding material in an amount of 40% to 75%; and (2) curing the mixture to provide a chemically bonded ceramic matrix of MgHPO.sub.43H.sub.2O (magnesium hydrogen phosphate trihydrate) and wollastonite with the radiation-shielding material dispersed therein. .Iaddend.

.Iadd.26. The method of claim 25, wherein the radiation-shielding material is selected from the group consisting of barite, barium sulfate, powdered annealed leaded glass, fibers of annealed leaded glass, barium oxide, cerium oxide, tungsten or a tungsten-containing compound, tungsten oxide, gadolinium, gadolinium oxide, depleted uranium oxide, iron oxide, bismuth or a bismuth-containing compound, boron or a boron-containing compound, aluminum oxide, zeolites, clinoptilotites, celestites, depleted uranium, and combinations thereof. .Iaddend.

.Iadd.27. The method of claim 25, wherein curing occurs at less than 100 C. .Iaddend.

.Iadd.28. A method of shielding radiation emitting from a radiation source, comprising obstructing the radiation using a radiation shielding member according to claim 20. .Iaddend.

Description

DETAILED DESCRIPTION

(1) Reference will now be made in detail to the presently preferred embodiments of the invention. The present invention is directed to a composition of matter and method for forming a radiation-shielding member at ambient conditions. Those of skill in the art will appreciate the composition of matter of the present invention is intended to be utilized for shielding and attenuation of various forms of radiation, including x-radiation, the electromagnetic and microwave spectrums; and energy from electron-beam welding (bremsstrahlung radiation or secondary radiation), and the like.

(2) The composition of matter and method provides an efficient composition for utilization in constructing members that exhibit radiation-shielding capability in a region of the electromagnetic spectrum. The resultant material may be formed at ambient conditions in a rapid time frame (one-half hour curing to two days curing). This allows for the formation of a chemically bonded oxide-phosphate ceramic matrix with radiation, electromagnetic, and microwave shielding inclusion materials without the high temperature firing typically required. Typical high temperature firing may exceed several hundred degrees Celsius and usually may occur in the range about 1800 C. (one thousand eight hundred degrees Celsius). While the present method of cold-firing (curing at ambient temperatures) may occur at or below 100 C. (one hundred degrees Celsius), the foregoing may allow for in-situ formation of a member such as a shielding structure or efficient transportation and installation of a preformed panel or structure formed of the composition of matter in comparison to other radiation shielding materials. For example, a structure formed in accordance with the present invention may allow for a fully cured wall partition to be formed and ready for use in the time frame of several days. A composition of matter of the present invention implements a cold-fired chemically bonded oxide-phosphate ceramic material so as to form a matrix for including additional radiation shielding material therein. A chemically bonded oxide-phosphate ceramic matrix may be formed by the incorporation of a metal oxide with a phosphate containing substance or material. Those of skill in the art will appreciate that the resultant chemically bonded oxide-phosphate ceramic may be a hydrated form based on the constituent metal phosphate. Suitable metal oxides may include metal oxides in which the cationic component is associated with radiation shielding, such that the resultant metal phosphate ceramic may exhibit radiation-shielding capability. Suitable phosphates containing substances or materials include potassium dihydrogen phosphates, phosphoric acid, an acid phosphate, monohydrogen phosphates, and the like. Suitable oxides include magnesium, iron (II or III), aluminum, barium, bismuth, cerium (III or IV), gadolinium, tungsten, and depleted uranium (III) (substantially uranium 238).

(3) The resultant chemically bonded oxide-phosphate ceramics may include KH.sub.2PO.sub.4 (potassium dihydrogen phosphate), MgHPO.sub.4.3H.sub.2O (magnesium hydrogen phosphate trihydrate), MgHPO.sub.4 (magnesium hydrogen phosphate),Fe.sub.3(PO.sub.4).sub.2 (iron(II) phosphate), Fe.sub.3(PO.sub.4).sub.2.8H.sub.2O(iron(II) phosphate octahydrate), FePO.sub.4 (iron(III) phosphate), FePO.sub.4.2H.sub.2O (iron(III) phosphate dihydrate), AlPO.sub.4 (aluminum phosphate), AlPO.sub.4.1.5 H.sub.2O (aluminum phosphate hydrate), CaHPO.sub.4 (calcium hydrogen phosphate), CaHPO.sub.4.2H.sub.2O (calcium hydrogen phosphate dihydrate), BiPO.sub.4 (bismuth phosphate), CePO.sub.4 (cerium(III) phosphate), CePO.sub.4.2H.sub.2O (cerium(III) phosphate dihydrate), BaHPO.sub.4 (barium hydrogen phosphate) and UPO.sub.4(depleted uranium (U-238) phosphate). In further instances, different metal and rare earth phosphates/hydrogen phosphates such GdPO.sub.41H.sub.2O gadolinium phosphate may be implemented as well. Suitable multiple metal phosphates may include magnesium hydrogen phosphate, iron(III) phosphate, aluminum phosphate, calcium hydrogen phosphate, cerium(III) phosphate, and barium hydrogen phosphate. In an embodiment the ceramic matrix is of the formula: ceramic matrix is of the formula: MHPO.sub.4.xH2O in which M is a divalent cation selected from the group consisting of: Mg (magnesium), Ca (calcium), Fe (iron(II)), and Ba (barium); wherein x is at least one of 0 (zero), 2 (two), 3 (three), or 8 (eight).

(4) In a further example, the chemically bonded oxide-phosphate based ceramic matrix is of the formula: MPO.sub.4.xH2O in which M is a trivalent cation selected from: Al (aluminum), Ce (cerium (III)), U.sup.238 (depleted uranium); and Fe (iron(III)); and x is at least one of 0 (zero), 1.5 (one point five), or 2 (two). In further embodiments, a multiple layer structure is formed to provide effective attenuation across a range of kilovolt-peak (kVp) ranges. For example, a multiple layer material is formed via a casting or spray application to form a mono structure exhibiting shielding and attenuation across a range. The layers may be formed of differing combinations of ceramics and shielding materials to achieve the desired shielding and attenuation. For example, a first layer is formed with a bismuth shielding material while a second layer is formed of a cerium based ceramic. A third layer of a ceramic including a barium sulfate shielding material may be included as well. In the present example, cerium oxide is included for its attenuation X-rays at 120 kVp at a material thickness of 0.5 inches. Greater material thickness will effectively attenuate x-radiation at higher levels of energy. Also, in one embodiment the bismuth can be prepared or applied in a manner that shields radiation below gamma rays on the electromagnetic spectrum in wavelength, frequency, or photon energy.

(5) Thus, two or more radiation shielding materials can be employed to achieve a multiple layer structure. Because chemically bonded oxide-phosphate ceramic matrices successfully bond to themselves, use of two or more radiation shielding materials increases the range of shielding through layering of the materials in the ceramic matrix. Layering in one embodiment is accomplished through separate curing of individual layers, and then the layers are bonded together in a known manner, such as forming subsequent layers on previously cured layers or by bonding previously cured layers using a oxide-phosphate bonded ceramic adhesive.

(6) In embodiments of the aforementioned layer process, suitable radiation shielding materials may be dispersed in the oxide-phosphate ceramic cement matrices. Those of skill in the art will appreciate that combinations of shielding materials may be incorporated into a single matrix to provide attenuation across a portion of the electromagnetic spectrum, such as X-rays, microwaves, and the like regions or portions of regions of the electromagnetic spectrum. Examples include powders, aggregates, fibers, woven fibers and the like. Exemplary materials include barite, barium sulfate, bismuth metal, tungsten metal, annealed leaded glass fibers and powders, cerium oxide, zeolite, clinoptilotite, plagioclase, pyroxene, olivine, celestite, gadolinium, suitable forms of lead, and depleted uranium.

(7) A zeolite may be approximately by weight percentage 52.4% (fifty two point four percent) SiO.sub.2 (silicon dioxide), 13.13% (thirteen point one three percent) Al.sub.2O.sub.3 (alumina oxide), 8.94% (eight point nine four percent) Fe.sub.2O.sub.3 (ferric oxide), 6.81% (six point eight one percent) CaO (calcium oxide), 2.64% (two point six four percent) Na.sub.2O (sodium oxide), 4.26% (four point two six percent) MgO (magnesium oxide). While barite may be approximately 89% (eighty nine percent) or above, BaSO.sub.4 (barium sulfate) and 5.8% (five point eight percent) silicates with the remainder consisting of naturally varying percentages of titanium dioxide, calcium oxide, magnesium oxide, manganese oxide, and potassium oxide. The foregoing approximation is dependent on naturally occurring weight percentage variations. In one embodiment, the zeolite component of the ceramic is either a basalt zeolite or clinoptilolite of a particle size in the range of from about 5 microns to about 500 microns (minus 30 to plus 325 mesh 25% passing 325 mesh). Research carried out has shown the best results are obtained when zeolite is present in a weight range of about 2-20% by weight zeolite to ceramic. It has been found that with the combination of barite and zeolite, enhanced radiation protection is provided over what is provided by using barite alone, because of the isotope encapsulation abilities of zeolite.

(8) The zeolite is preferably used in a natural form, although a synthetic zeolite can be used. As understood by those of skill in the art, the main zeolite formula is M2/nO.Al2O3.xSiO2.yH2O, with M defining the compensating cation with valence n [7]. The structural component is Mx/n[(AlO2)x(SiO2)y].zH2O, with the general structure as arrangements of tetrahedra in building units from ring structures to polyhedra.

(9) In an exemplary embodiment, a method of constructing a shielding member includes mixing a metal oxide, such as a metal oxide including divalent metal cation with a phosphate containing material. Suitable phosphate containing materials include phosphoric acid, hydrogen phosphate substances (such as monohydrogen phosphates and potassium dihydrogen phosphates) and the like. A radiation shielding material may be incorporated into the metal oxide and phosphate containing material mix. Incorporating may include dispersing aggregate, powder, and fibers. Woven fibers may be incorporated as part of a casting process, a layering process, or the like. The incorporated radiation shielding material and metal oxide-phosphate ceramic may be cured to hardness (maximum compressive strength) at ambient conditions. For example, the member may be cast in place and the curing reaction being conducted at ambient conditions (i.e., ambient temperature). In an embodiment, the reaction and curing of the radiation shielding member occurs at, or at less than, 100 C. (one hundred degrees Celsius). Those of skill in the art will appreciate that the porosity of the resultant member may be varied based on the reagents selected. Excellent admixture aggregates so as to significantly decrease porosity and add strength are fly ash, bottom ash, and wollastinite that can be added in ratios ranging from 15:85 and 50:50, as well as other sparsely soluble silicates as explained in U.S. Pat. No. 6,518,212, entitled: Chemically bonded phospho-silicat ceramics: A chemically bonded phospho-silicate ceramic formed by chemically reacting a monovalent alkali metal phosphate (or ammonium hydrogen phosphate) and a sparsely soluble oxide, with a sparsely soluble silicate in an aqueous solution. The monovalent alkali metal phosphate (or ammonium hydrogen phosphate) and sparsely soluble oxide are both in powder form and combined in a stochiometric molar ratio range of (0.5-1.5):1 to form a binder powder. Similarly, the sparsely soluble silicate is also in powder form and mixed with the binder powder to form a mixture. Water is added to the mixture to form a slurry. The water comprises 50% by weight of the powder mixture in said slurry. The slurry is allowed to harden. The resulting chemically bonded phospho-silicate ceramic exhibits high flexural strength, high compression strength, low porosity and permeability to water, has a definable and bio-compatible chemical composition, and is readily and easily colored to almost any desired shade or hue. Other examples of these sparsely soluble silicates are Calcium silicate (CaSiO.sub.3), Magnesium silicate (MgSiO.sub.3), Barium silicate (BaSiO.sub.3), Sodium silicate (NaSiO.sub.3), Lithium silicate (LaSiO.sub.3), and Serpentinite (Mg.sub.64.O.sub.10.{OH.sub.8}).

(10) In a specific embodiment, a radiation shielding member composed of a composition of matter of the present invention is constructed by mixing 1 lb. (one pound) of a metal oxide, monopotassium phosphate with 1 lb. (one pound) of radiation shielding material such as an aggregate, powder, or fiber filler attenuating material, and H.sub.2O (water) is added to approximately 20% (twenty percent) by weight, and the resultant cold-fired composite radiation shielding material is allowed to cure. In this embodiment, the metal oxide-to-monopotassium phosphate ratio, by weight, is 1/3 (one-third) metal oxide, such as dead-burned magnesium oxide, to two thirds monopotassium phosphate, or MKP (KH.sub.2PO.sub.4) and a further weight ratio of 15:85 to 50:50 of fly ash, bottom ash and other suitable sparely soluble silicates. It should be noted that due to the differing molar ratios between the dead-burned magnesium oxide (MgO) and the monopotassium phosphate (MKP), and/or any suitable alternate oxides and phosphate materials employed, the aforementioned MgO, MKP weight/volume ratios may be varied and still produce effective bonding for the intended attenuating/shielding admixtures.

(11) In further embodiments, various carbonates, bicarbonate (such as sodium bicarbonate, potassium bicarbonate and the like) or metal hydroxides reagents may be reacted in a two step process with an acid phosphate to limit the maximum reaction temperature of the metal oxide and the result of the carbonate, bicarbonate or hydroxide reaction with an acid phosphate.

(12) In further embodiments, other acids may be implemented to form a resultant metal oxide-phosphate ceramic-based material. The selection of the acid may be based on the metal oxide to be utilized; suitable metal oxides include divalent and trivalent metals (including transition metals and lanthanide series and actinide series metals). Other suitable acids include boric acid as a retardant (<1% of the total powder). And in another embodiment hydrochloric acid is used as a catalyst when certain oxide phosphate cementious blends such as a barium oxide, and bismuth phosphate blend are not suitably water-soluble.

(13) In specific examples, mixing the selected ceramic matrix with the desired shielding material formed exemplary compositions. In one embodiment, the final combined mixture forms a product in which the shielding material is cemented or bonded with the ceramic matrix, which includes internal bonding or external bonding or both. In addition, the ceramic matrix materials are in the range of 200 mesh or below. The following specific examples are only exemplary and utilized to explain the principles of the present invention. The following procedures were conducted in ambient conditions (e.g., temperature, pressure). For instances, carried out at a room temperature of between 65 F. to 85 F. (sixty-five degrees Fahrenheit to eighty-five degrees Fahrenheit) under atmospheric pressure. No attempt was made to fully homogenize the material to obtain uniform particles, while substantially uniform distribution of shielding material within the ceramic matrix was attempted.

(14) For samples in which woven fiber shielding fabric material is utilized, the ceramic is hydrolyzed and cast in contact with the fabric material. In instances in which powdered shielding material are incorporated, the particle size varied depending on the material. Ideally, the powder particles are sized in the range of 200 mesh or below. Those of skill in the art will appreciate that a wide range of particle sizes may be utilized. Water is added to hydrolyze the dry mixture. The combination of the water and ceramic oxide, phosphate and shielding material is mixed for a sufficient duration and with sufficient force to cause the mixture to exhibit an exothermic rise of between 20%-40% (twenty percent to forty percent) of the original temperature of the mixture. The hydrolyzed mixture was compacted via vacuum or vibratory or equivalent method to eliminate voids. Compaction is preferably conducted in a container, such as a polymeric container formed from polypropylene or polyethylene, having a low coefficient of friction to facilitate removal. The samples were allowed to harden to the touch (at least twenty-four hours) at ambient conditions.

(15) The samples were submitted for x-ray lead equivalency testing. The samples submitted for testing were formed when a metal oxide such as MgO ('dead-burned' Magnesium Oxide), a suitable sparsely soluble silicate and radiopac additives as set forth in the present disclosure, are stirred in an acid-phosphate solution, (such as monopotassium phosphate and water). The dissolution of the metal oxide forms cations that react with the phosphate anions to form a phosphate gel. This gel subsequently crystallizes and hardens into a coldfired ceramic. Dissolution of the oxide also raises the pH of the solution, with the cold-fired ceramic being formed at a near-neutral pH.

(16) Controlling the solubility of the oxide in the acid-phosphate solution produces the chemically bonded oxide-phosphate ceramic. Oxides or oxide minerals of low solubility are the best candidates to form chemically bonded phosphate ceramics because their solubility can be controlled. The metal oxide in the sample formulations is known as dead-burned Magnesium Oxide (MgO), calcined at 1300 C. or above in order to lower the solubility in the acid-phosphate solution. Oxide powders can be pretreated for better reactions with the acids. One technique includes calcining the powders to a typical temperature of between approximately 1,200 C. and 1,500 C. and more typically 1,300 C. It has been found that the calcining process modifies the surface of oxide particles in a myriad of ways to facilitate ceramic formation. Calcining causes particles to stick together and also form crystals; this leads to the slower reaction rates that foster ceramic formation. Fast reactions tend to form undesired powdery precipitates. Such dead-burned magnesium oxide can then be reacted at room temperature with any acid-phosphate solution, such as ammonium or potassium dihydrogen phosphate, to form a ceramic of the magnesium potassium phosphate. In the case of magnesium oxide-mono potassium phosphate, a mixture of MgO ('dead-burned' Magnesium Oxide), KH.sub.2PO.sub.4 (Monopotassium Phosphate), and a suitable sparsely soluble silicate can simply be added to water and mixed from 5 minutes to 25 minutes, depending on the batch size. Monopotassium Phosphate dissolves in the water first and forms the acid-phosphate solution in which the MgO dissolves. The resultant cold-fired, chemically-bonded oxide-phosphate ceramics are formed by stirring the powder mixture of oxides and radiopac additives, including any desired retardants such as boric acid as have been clearly described herein, into a water-activated acid-phosphate solution in which the dead-burned magnesium oxide (MgO) dissolves and reacts with the monopotassium phosphate (MKP) and in some applications a suitable sparsely soluble silicate such as wollastinite, and sets into a cold-fired ceramic cementious material.

(17) TABLE-US-00001 TABLE 1 CERAMIC SAMPLE FORMULATION den- sity Sam- H20 ceramic shielding lbs/ ple (g) (g) material (g) particle size ft.sup.2 1 112.0 198.0 462.0 barium 10 m (microns) 152.0 sulphate 2 112.0 220.0 220.0 barium 325 mesh (bismuth) 197.0 sulphate 220.0 bismuth 3 112.0 198.0 462.0 bismuth 325 mesh 225.0 4 112.0 198.0 462.0 cerium 5.24 m (microns) 175.0 III oxide 5 112.0 264.0 264.0 barium 10 m (microns) 74.0 sulphate 66.0 bismuth 325 mesh (bismuth) 66.0 cerium III 5.24 m (microns) oxide 6 112.0 basalt powder 130.0 462

(18) TABLE-US-00002 TABLE 2 CERAMIC SAMPLE ATTENUATION Sample Attenuation Designation 60 kVp 80 kVp 100 kVp 120 kVp 1 99.99% 99.97% 99.76% 99.05% 2 99.99% 99.98% 99.77% 99.64% 3 99.89% 99.85% 99.77% 99.70% 4 99.95% 99.92% 99.82% 99.37% 5 99.96% 99.91% 99.66% 99.19% 6 89.17% 81.79% 75.36% 69.62% 7 97.34% 96.37% 93.81% 90.00% 8 56.08% 52.33% 47.83% 43.52% Measured Half 3.0 mmA1 4.0 mmA1 5.1 mmA1 6.2 mmA1 Value Layer (HVL)

(19) TABLE-US-00003 TABLE 3 CERAMIC SAMPLE LEAD EQUIVALENCY (MILLIMETERS PB) Sample Lead Equivalency (mm Pb) Designation 60 kVp 80 kVp 100 kVp 120 kVp 1 1.8* 1.800 1.535 1.065 2 1.8* 1.822 1.552 1.445 3 0.635 1.380 1.551 1.525 4 0.758 1.440 1.660 1.225 5 0.790 1.410 1.375 1.125 6 0.119 0.126 0.130 0.129 7 0.242 0.390 0.428 0.362 8 0.064 0.068 0.070 0.070 Measured Half 3.0 mmA1 4.0 mmA1 5.1 mmA1 6.2 mmA1 Value Layer (HVL) *Due to the high attenuation of this sample, lead equivalency cannot be accurately reported for a tube potential of 60 kVp. The lead equivalency will be no less than that of the next higher kVp setting. (Wherein kVp - kilovolt-peak; mmA1-)

(20) It is understood that the specific order or hierarchy of steps in the processes disclosed is an example of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged while remaining within the scope of the present invention. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

(21) It is believed that the present invention and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention, or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof. An expected specific change is the eventual inclusion of nano-sized constituent material preparation so as to increase the available surfaces principle of bonding. Most if not all of the chemically bonded oxide-phosphate radiation shielding ceramics described in the present patent can be produced as cement, concrete, drywall material, coatings, and groutings, and can be poured, sprayed, troweled, and molded into a variety of forms and uses. Therefore it is the intention of the following claims to eventually encompass and include most, if not all, of these changes and potentials.

(22) In addition, the embodiments disclosed herein can be applied to radiation contaminated objects and structures, to encapsulate the same and contain the contaminant within the object or structure, thus shielding and protecting objects external to the encapsulated object or structure.