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
  • G21F9/30—Processing
  • G21F9/301—Processing by fixation in stable solid media
  • G21F9/307—Processing by fixation in stable solid media in polymeric matrix, e.g. resins, tars
• • 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 a method for disposing of radioactive materials, in particular radioactive graphite as casting compound or casting body, in particular produced using the previously defined methods.
• Radioactive waste particularly radioactive graphite
• final storage for example by so-called compact conditioning or by solidification (cementing, etc.), but very large volumes of material to be disposed of or to be disposed of result.
• compact conditioning or by solidification cementing, etc.
• WO98 / 54107 proposes the encapsulation of hazardous wastes, such as heavy metals, arsenic, etc., and radioactive materials. Encapsulation takes place in a hardenable system containing calcium carbonate and magnesium oxide.
• DE 31 31 798 in turn describes the mechanical disassembly of fuel elements with the aid of a high-pressure water jet. After the graded material has been classified, the graphite slurry that is finally obtained is solidified with cement to form final storage blocks.
• the prior art offers the possibility of dry mixing graphite, for example, together with sand and cement, and then solidifying it by adding water to produce blocks.
• graphite / sand cement blocks produced in this way have poor compressive strength, so that the disposal of radioactive graphite proposed in the prior art, for example by concreting in, has not been pursued further.
• the object is achieved by means of a method according to the wording according to claim 1.
• the fine fraction in the material to be disposed of, such as graphite is low, ie that the proportion with an average grain size ⁇ 250 ⁇ m is less than 30% by weight.
• the fine fraction ⁇ 200 ⁇ m of the radioactive waste to be disposed of is preferably less than 20%, more preferably less than 15% by weight.
• the radioactive reactor graphite to be disposed of for example in a formulation of casting or pouring mortar and concrete, such as, in particular, cement mortar, the sand or gravel normally used through the ground or broken and broken and to be disposed of radioactive material in a hydraulic binder.
• the radioactive reactor graphite to be disposed of for example in a formulation of casting or pouring mortar and concrete, such as, in particular, cement mortar, the sand or gravel normally used through the ground or broken and broken and to be disposed of radioactive material in a hydraulic binder.
• the radioactive reactor graphite to be disposed of for example in a formulation of casting or pouring mortar and concrete, such as, in particular, cement mortar, the sand or gravel normally used through the ground or broken and broken and to be disposed of radioactive material in a hydraulic binder.
• the radioactive reactor graphite to be disposed of for example in
• radioactive reactor graphite is thus, for example, by wet grinding with subsequent, sometimes complete substitution of additives such as sand and / or gravel and / or additives in cement-bound masses such as cement mortar, concrete, for example in the form of a graphite / cement mortar matrix for filling other waste-laden materials
• Containers such as containers and the like are used.
• this type of waste conditioning a complete elimination of the volume of waste that otherwise arises during the solidification of radioactive reactor graphite, which alone or with other radioactive waste as a final condition, can be achieved. nated waste containers would then be available. From an economic point of view, this method of graphite disposal is associated with considerable cost savings, since otherwise high disposal costs would be incurred due to the additional waste containers to be generated with subsequent storage.
• the graphite disposal method consists of the following steps:
• Grinder such as a crushing mill known for example in grit production for grain sizes from 0 - approx. 60 mm diameter for the purpose of substituting additives and / or additives, such as up to 100% sand (here grain sizes up to 6 mm) as additives in the cement-bound formulation, which may be approximately 45% by weight in cement-containing fillers, which are used for final conditioning to solidify other waste to be disposed of in containers.
• additives and / or additives such as up to 100% sand (here grain sizes up to 6 mm) as additives in the cement-bound formulation, which may be approximately 45% by weight in cement-containing fillers, which are used for final conditioning to solidify other waste to be disposed of in containers.
• the addition of ground graphite can also be present in addition to the amount of sand, sometimes by further substitution of additives up to 50% by weight in the cement mortar.
• additives such as gravel and sand and sometimes also additives can be substituted by broken and crushed raioactive graphite
• a graphite / cement ratio of at least 1.3 is chosen, more preferably a graphite / cement ratio of at least 1.35.
• FIG. 1 shows in section an example of a container 1 containing various radioactive materials to be disposed of, which are enclosed in a potting matrix proposed according to the invention.
• 1 schematically shows, for example, a graphite segment 3, graphite fragments 5, segments of a thermal or biological protective shield 7 and colemanite concrete fragments 9.
• Fig. 2 shows in section a further container 21, which may be, for example, a 20 t small thin-walled concrete container, mainly containing radioactive steel or gray cast iron waste, which have been used, for example, as protective shields in nuclear reactors.
• a further container 21 which may be, for example, a 20 t small thin-walled concrete container, mainly containing radioactive steel or gray cast iron waste, which have been used, for example, as protective shields in nuclear reactors.
• Table 1 shows four recipes with maximum grain sizes of graphite of 6 mm, 15 mm, 30 mm and 60 mm.
• the pore filler is amorphous silica, a binder for excess calcium hydroxide (Ca (OH) 2 ). This disperse silica serves to increase the leaching strength.
• Zeolite is a substitute for binding cesium and strontium, which are mobile radioactive fission products that are usually easily soluble. Zeolite prevents the leaching of mobile radionuclides.
• the additives such as pore fillers and zeolite, can be replaced by finely ground graphite waste.
• a Portland cement or higher-quality cements such as, for example, sulfate-resistant cements or corrosion-resistant cements, which are used especially in bridge construction and for applications under water, are advantageously used as the cement.
• binders are possible:
• An additive is used as a plasticizer to optimize the flowability or the degree of filling of the mortar mixture.
• wetting agent Used to wet the graphite surface and to prevent air pockets. The wetting agent must not be complex and should be quickly degradable in a cement environment. Two years after solidification (storage), a wetting agent should largely no longer be detectable.
• FIGS. 3 to 6 show the corresponding sieve analyzes of the graphite used in the four formulations, FIG. 3 showing a max. Grain size of 6 mm, Fig. 4 is a max. 15 mm, Fig. 5 of 30 mm and Fig. 6 of 60 mm.
• Table 2 below shows the grain size distributions of the various graphite aggregates with the maximum grain diameters 6, 15, 30 and 60 mm, as they are shown in FIGS. 3-6.
• the formulation when using a maximum grain size of up to 60 mm the formulation can be loaded with significantly more graphite, ie approx. 70% more than with a maximum grain size of 6 mm.
• Which formulation is ultimately used for the pouring of further radioactive waste depends on the "bulkiness" or on the dimensions of this waste as well as on the order of magnitude of the loading of the graphite / cement mortar mass. The larger the maximum grain size of the graphite in the mortar formulation, the higher the graphite loading of the formulation.
• the great advantage of the graphite / cement mortar formulations proposed according to the invention lies in the fact that, in addition to the pouring of any radioactive waste and in addition to liquids to be disposed of, instead of the sand or gravel or other additives normally used, radioactive reactor graphite can be disposed of.
• a higher degree of filling can be used than is customary when using sand or mineral fillers.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Processing Of Solid Wastes (AREA)

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• 2000
  • 2000-05-16 JP JP2001503180A patent/JP2003502623A/ja not_active Withdrawn
  • 2000-05-16 WO PCT/CH2000/000268 patent/WO2000077793A1/de not_active Application Discontinuation
  • 2000-05-16 EP EP00922405A patent/EP1200965A1/de not_active Withdrawn

Non-Patent Citations (1)

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