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
  • G21F9/04—Treating liquids
  • G21F9/06—Processing
  • G21F9/16—Processing by fixation in stable solid media
  • G21F9/162—Processing by fixation in stable solid media in an inorganic matrix, e.g. clays, zeolites
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
  • C04B28/04—Portland cements
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/00767—Uses not provided for elsewhere in C04B2111/00 for waste stabilisation purposes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

• the invention relates to the treatment and disposal of boron containing radioactive waste waters such as characteristically generated by pressurized water reactor (PWR) nuclear facilities. More specifically, the invention relates to the treatment of such wastes in order to convert the same to a form more suitable for handling and disposal by encapsulation in solid binder materials.
• PWR pressurized water reactor
• boric acid waste common to pressurized water reactors contains boric acid as a chemical shim for
• the present invention relates to direct solidification of hot boric acid solutions by specific addition of magnesium compounds to form magnesium borates, which, after the addition of cement, then complexes with added calcium hydroxide or calcium oxide (lime) so that a uniform solid is produced with no apparent free liquid.
• Aqueous boric acid solutions from pressurized water reactors are mixed with finely powdered magnesium oxide or hydroxide to form a magnesium borate complex. While various powdered magnesium oxides or hydroxides may be utilized, the selection of materials is critical with respect to particle size.
• a particularly effective magnesium oxide powder is Magox 98 HR manufactured by Basic Chemicals. The fineness of this material is such that 99.5 percent will pass through
• the temperature of the aqueous boric acid waste is typically 77 degrees Centigrade when it leaves the reactor and is placed into the liner (container). However, this process will work with boric acid materials at .a temperature of 55-95 degrees Centigrade.
• the magnesium oxide compound is added to the boric acid waste and is continously agitated, in fact, agitation is maintained throughout the entire process until, because of increases in viscosity, agitation is no longer possible or required.
• the formation of the magnesium borates produces an exotherm which can be monitored by the use of a temperature sensing probe in the container.
• the exotherm is typically 3-6 degrees Centigrade.
• the amount of magnesium oxide or hydroxide required to treat each portion of waste is predetermined in the laboratory using process control procedures.
• the amount of the magnesium compound added is a function, obviously, of the concentration of the boric acid contained in the waste material.
• the amount of magnesium oxide or hydroxide added is about 50 percent or more by weight of the amount of boric acid (H ⁇ o ) present.
• cement is added to the liner and agitation is continued.
• the amount of cement added is as low as about 1/2 the weight of the radioactive waste liquid , in the system. While the choice of the type of cement is not necessarily critical, the use of various forms of Portland Cement is preferred.
• the calcium oxide or calcium hydroxide is added to the container. The addition of the calcium oxide component causes an increase in the pH of the system which promotes the formation of the gel matrix. It is important to note that the magnesium oxide or magnesium hydroxide in themselves will not shift the pH to the gelling range, even if added in excess. This then prevents premature gellation before the proper amount of cement has been added and mixed.
• the amount of the calcium- hydroxide or calcium oxide added to achieve the desired product gel is about ' 1/4 of the weight of boric acid waste liquid. As set forth above, the amounts of all components to be employed in this process are
• the state of the matrix gel formation can be monitored 0 by various means. Usually, the change in viscosity can be seen by an increase in hydraulic pressure for the agitator drive employed for mixing purposes.
• the gel structure itself has a substantial degree of ⁇ -* rigidity, as shown in the laboratory, even without the addition of cement. It is significant that the boric acid in the waste becomes an integral part of the gel structure, which in combination with the hydrated cement produces a uniform waste matrix. 0
• the rate at which the cement present in the system exothermically hydrates can be measured by the same probe used to measure the magnesium borate reaction exotherm.
• the solidified waste material is sufficiently 5 firm for shipment within about 24 hours. It is important that the calcium oxide or hydroxide be added only after the addition of the cement, because the change in pH resulting from the addition of the calcium component will cause the production of a gel and possibly not allow for adequate 0 mixing of the .cement.
• the instant invention can be utilized for certain wastes produced from boiling water reactors.
• a radioactive sulfate waste is produced from a boiling water reactor. In such a system it is necessary to
• magnesium oxides or magnesium hydroxides are both suitable for use, magnesium oxide is preferred because of the reduced cost and weight of the material.
• the instant invention provides several advantages over other processes for waste disposal.
• Of principal import is the fact that the amount of cement used in the process can be reduced by up to 50 percent. This allows for a considerably greater amount of room in the
• the final product contains no free liquids. In the event that there is some unreacted liquid, the liquid will, because of the greater density of the solid product, rise to the top of the container. Additional cement can then be added to solidify
• a typical liner for radioactive waste disposal contains 5.52 cubic meters of storage space. With prior art 35 processes, only about 3.40 cubic meters of waste could be 1 processed. By the process of this invention, up to 3.96 cubic meters of waste can be effectively solidified in the same size liner.

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Cited By (7)

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• 1983
  • 1983-10-17 WO PCT/US1983/001626 patent/WO1985001828A1/en unknown
  • 1983-10-17 EP EP83903692A patent/EP0157771A1/de not_active Withdrawn
  • 1983-10-17 JP JP58503726A patent/JPS61500455A/ja active Pending
• 1984
  • 1984-10-02 IT IT2294984A patent/IT1196276B/it active

Non-Patent Citations (1)

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