EP0192777B1 - Method of and apparatus for treating radioactive waste - Google Patents

Method of and apparatus for treating radioactive waste Download PDF

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Publication number
EP0192777B1
EP0192777B1 EP85904280A EP85904280A EP0192777B1 EP 0192777 B1 EP0192777 B1 EP 0192777B1 EP 85904280 A EP85904280 A EP 85904280A EP 85904280 A EP85904280 A EP 85904280A EP 0192777 B1 EP0192777 B1 EP 0192777B1
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Prior art keywords
radioactive waste
resin
carbonized
degassing
ion exchange
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German (de)
English (en)
French (fr)
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EP0192777A4 (en
EP0192777A1 (en
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Kiyomi Funabashi
Masami Matsuda
Hideo Yusa
Kazuhide Mori
Makoto Kikuchi
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Hitachi Ltd
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Hitachi Ltd
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    • 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
    • G21F9/32—Processing by incineration

Definitions

  • the present invention relates to a process for treating a radioactive waste comprising mainly a used ion exchange resin.
  • the invention relates to a process and device for treating a spent ion exchange resin having adsorbed a radioactive material, which is generated from a nuclear power plant.
  • the above-mentioned volume reduction and solidification treatment apparatuses are satisfactory from the viewpoints of the technical performance and safety, they have a problem that an increase in the capacity of the apparatus and a special means are necessitated for the treatment of spent ion exchange resin because of its properties.
  • the description will be made on the problems of the respective apparatuses stated above.
  • the quantity of heat generated amounts to 10 4 kcal/kg which is thrice as much as that of the inflammable solids, since the spent ion exchange resin is a plastic. Therefore, a means is provided therein so as to prevent a temperature runaway in the fluidized bed furnace. It is, for example, a means of introducing and mixing with another radioactive waste of a low calorific value such as inflammable solids.
  • thermoplastic resin used as the solidifying agent
  • the intended solidifying effect of the thermoplastic resin cannot be obtained when water is contained therein even in only a small amount.
  • thermosetting resin when the solidification is effected in the presence of water, a curing accelerator, such as cobalt naphthenate, in the thermosetting resin is decomposed and, therefore, this resin cannot be cured, so that a part of the thermosetting resin remains as it is, i.e. in liquid form.
  • a curing accelerator such as cobalt naphthenate
  • the solid product having a high toughness cannot be obtained.
  • the water content of a powder dried with a centrifugal thin film dryer is controlled strictly by determination with a moisture meter such as a neutron moisture meter.
  • the pellets are broken due to the moisture during the storage, since dry powder of the spent ion exchange resin absorbs water to change its volume. To prevent the breakage, the humidity of air in the pellet-storing tank is controlled.
  • the dry powder or pellets of the spent ion exchange resin are solidified with a hydraulic solidifyng agent such as cement or a solidifying agent comprising an alkali silicate solution
  • a hydraulic solidifyng agent such as cement or a solidifying agent comprising an alkali silicate solution
  • said dry powder or pellets absorb water to increase the volume thereof, since the solidification reaction is effected in the presence of a large amount of water. Therefore, when the hydraulic solidifying agent or the solidifying agent comprising an alkali silicate solution is used, the amount of the solidified radioactive waste to be packed in an ordinary 200 I drum is only 1/3 to 1/2 of that treated in the apparatus (2) (110 kg of the resin can be packed in the 200 I drum) disadvantageously.
  • US-A-40 53 432 describes a process for reducing the volume of a spent radioactive ion exchange resin in which the resin is dehydrated, thermally decomposed into a waste gas and a radioactive material, which is burnt in an oxygen-containing gas.
  • a spent radioactive ion exchange resin from a nuclear power plant is thermally decomposed in 2 steps: first at a temperature of 350°C or below to decompose the ion exchange groups and then at high temperature to decompose the polymer matrix.
  • the radioactive components remain in the residue which is solidified with a solidifying agent such as cement or plastic.
  • the processes for treating the radioactive waste comprising mainly spent ion exchange resin have problems due to the properties of the ion exchange resin.
  • the object of the present invention is to provide a process and an apparatus for treating a radioactive waste comprising mainly a spent ion exchange resin by reducing its volume and solidifying the same in an easy manner to obtain a solid having a high uniaxial compression strength.
  • the process of the present invention for treating radioactive waste mainly comprising a spent ion exchange resin comprises the steps of
  • the invention further concerns the apparatus for treating a radioactive waste, comprising mainly a spent ion exchange resin, which comprises a thermal decomposition device for heating the radioactive waste to carbonize it, comprising an inert gas feeding device for feeding an inert gas in the thermal decomposition device, a waste gas treating device for discharging the gas generated in the thermal decomposition device and treating the gas, the degassing means for degassing the carbonized radioactive waste to remove a gas adsorbed therein and a solidifying means for solidifying the degassed radioactive waste.
  • the apparatus for treating a radioactive waste comprising mainly a spent ion exchange resin
  • a thermal decomposition device for heating the radioactive waste to carbonize it, comprising an inert gas feeding device for feeding an inert gas in the thermal decomposition device, a waste gas treating device for discharging the gas generated in the thermal decomposition device and treating the gas, a pelletizer for pelletizing the carbonized radioactive waste, a degassing means for degassing the pelletized radioactive waste to release a gas adsorbed therein and a solidifying means for solidifying the degassed, pelletized radioactive waste.
  • the present invention having the above-mentioned characteristic. constitution exhibits an effect of remarkably reducing the volume of a radioactive waste comprising mainly a spent ion exchange resin and solidifying it in an easy manner to obtain a solid having a high uniaxial compression strength.
  • the fundamental principle of the present invention is that the ion exchange groups of an ion exchange resin are thermally decomposed at a temperature of 120 to 350°C, preferably 200 to 300°C and that a styrene/divinylbenzene copolymer which is a polymer base of the ion exchange resin is carbonized in the step of thermal decomposition.
  • the inventors have further found that as the polymer base of the ion exchange resin is carbonized by the thermal decomposition, the expansion or shrinkage due to water absorption or drying of the ion exchange resin observed before the carbonization disappears and, instead, a phenomenon of the adsorption of a gas such as air appears.
  • the cation exchange resin has a polymer base comprising a copolymer of styrene with divinylbenzene having a sulfonic acid group (S0 3 H) bonded thereto as the ion exchange group.
  • This compound has a crosslinked, three-dimensional structure of the following formula and a molecular formula of (C 16 H 15 0 3 S) n :
  • the anion exchange resin has the same polymer base as that of the above-mentioned cation exchange resin but it has a quaternary ammonium group (NR 3 0H) bonded thereto as the ion exchange group.
  • This compound has the molecular formula of (C 2o H 26 0N) n and the following structural formula:
  • Fig. 2 shows a skeletal structure of the cation exchange resin.
  • the skeletal structure of the anion exchange resin is essentially the same as this, merely different in the ion exchange groups from each other.
  • the ion exchange group having the lowest bond energy is decomposed first, then the straight-chain moiety of the polymer base is decomposed, and finally the benzene ring moiety is decomposed.
  • thermogravimetric analysis TGA
  • Fig. 3 The results of the thermogravimetric analysis (TGA) of the ion exchange resin effected with a differential thermal balance in air are shown in Fig. 3. A weight loss due to the evaporation of water occurring at 70 to 110°C is not shown.
  • the solid line shows a thermogravimetric change of the anion exchange resin and the broken line shows that of the cation exchange resin.
  • the decomposition temperatures of the bonded moieties shown in Fig. 3 are shown in Table 2.
  • the quaternary ammonium group (ion exchange group) of the anion exchange resin is decomposed first at 130 to 190°C, then the straight-chain moiety is decomposed at 350°C or higher, and finally the benzene ring moiety is decomposed at 380°C or higher.
  • the sulfonic acid group (ion exchange group) is decomposed at 200 to 300°C, then the straight-chain moiety, and finally the benzene ring moiety are decomposed in the same manner as in the anion exchange resin.
  • Figs. 4 and 5 show results of thermogravimetric analyses carried out in air containing oxygen in an amount corresponding to a chemical equivalent necessary for the thermal decomposition of the spent resin and in an oxygen-free nitrogen atmosphere (the results shown in Fig. 3 were obtained when oxygen was fed in an amount far larger than the chemical equivalent).
  • Fig. 4 showing the results obtained by the thermal decomposition of the cation exchange resin, the solid line shows those obtained in an atmosphere containing a chemical equivalent of oxygen and the broken line shows those obtained in a nitrogen atmosphere. It will be understood that a major part of the reaction of the polymer base is oxidation which requires oxygen and which is exothermic.
  • the ion exchange group (sulfonic acid group) is thermally decomposed at 200 to 300°C even in a nitrogen atmosphere. In this case, the supply of oxygen is unnecessary for the thermal decomposition of the ion exchange group and this reaction is not exothermic.
  • Fig. 5 shows the data obtained by the thermal decomposition of the anion exchange resin.
  • the solid and broken lines show the data obtained in the atmosphere containing a chemical equivalent of oxygen and in a nitrogen atmosphere, respectively, as in Fig. 4. It has thus been found that the ion exchange group (quaternary ammonium group) of the anion exchange resin is decomposed at 130 to 190°C even in the absence of oxygen and the polymer base is oxidatively decomposed by oxygen at 350 to 480°C to generate heat like the cationic exchange resin.
  • dry granular ion exchange resin and granular ion exchange resin thermally decomposed at 600°C (hereinafter referred to as carbonized resin) were used and degrees of swelling of them with water were measured.
  • carbonized resin dry granular ion exchange resin and granular ion exchange resin thermally decomposed at 600°C
  • the phenomenon observed when the dry ion exchange resin was immersed in water was different from that of the carbonized resin.
  • the phenomena and the mechanisms thereof of both resins are shown in Fig. 7.
  • the phenomenon observed when the dry ion exchange resin is immersed in water is swelling and the mechanism is considered generally as follows: the ion exchange group of the ion exchange resin is present in the reticular molecular structure of the styrene/divinylbenzene copolymer.
  • the ion exchange group has a high polarizability. This is a main cause for the adsorption of water having a high polarity.
  • the adsorbed water penetrates therein even by forcedly enlarging the openings of the elastic reticulate structure of the polymer base, whereby the ion exchange resin is swollen to increase its volume.
  • the granular ion exchange resin having an average granular diameter of 400 pm in a dry state is swollen to an average granular diameter of 450 to 600 pm (the volume ratio: 1.2 to 3) (the degree of the volume increase which varies depending on the ion bonded with the ion exchange group is generally as follows: H * > alkali metal > alkaline earth metal and transition metal).
  • the ion exchange resin is swollen for the following two reasons: one is that the ion exchange group having a high polarizability absorbs water and the reason is that the polymer base has an elastic reticulate structure. Namely, even a resin comprising a polymer base having no ion exchange group absorbs water to expand its volume about 1.2-fold. However, this phenomenon is not observed in the carbonized resin. Namely, the granule diameter of the resin is reduced by the carbonization below that of the dry resin and the volume of the carbonized resin is 1/2 of the dry resin. Consequently, the properties of pores of up to about 0,7 mm (7A) of the ion exchange resin appear.
  • the molecular structure is converted into a polycyclic one which is close to the structure of graphite and, as a result, a hydrophobic property of carbon appears.
  • This property inhibits the adsorption of water in the pores and facilitates the adsorption of a gas such as air.
  • the gas such as air temporarily adsorbed is desorbed again and released as the gas in the presence of a large amount of water when, for example, it is immersed in water. This is the degassing phenomenon. Because of this phenomenon, the carbonized resin seems as if it is swollen. Since the carbonized resin has a dense polycyclic structure, its volume is not increased even by adsorption of water, unlike ordinary polymer bases. This fact is supported by the fact that the volume was unchanged even after the immersion for 150 h (about 6 days) as shown in Fig. 6.
  • the above-described properties of the carbonized resin were not known prior to the present invention. Namely, the ion exchange resin thermally decomposed at a temperature in the range of 200 to 600°C (above 120°C) has properties utterly different from those of the non-decomposed ion exchange resin.
  • the intermediate storage of the waste can be facilitated without necessitating any special equipment for humidity control, etc. Since the carbonized resin or its pellets are hydrophobic as described above, the solid product thereof prepared by solidifying the same even with a thermosetting plastic sensitive to water has a high strength.
  • the inventors have developed a process for preparing the solidified product by degassing the carbonized resin by immersing it in a solidifying agent comprising the hydraulic substance or alkali silicate while the hardening effect thereof is inhibited and then hardening the solidifying agent.
  • the carbonized resin was immersed in the alkali silicate solution to degass the resin. Then, the hardening agent was added thereto to solidify the same.
  • the relationships between the residue of the adsorbed gas and the strength of the solidified product and between the former and the feed amount are shown in Fig. 8.
  • the temperature in this step was 25°C and the relative amounts of the carbonized resin alkali silicate solution and hardening agent were 40 wt.%, 40 wt.% and 20 wt.%, respectively.
  • the hardening agent is not limited to silicon polyphosphate but any weak acid may be used. Examples of them include inorganic phosphates such as sodium phosphate and alkaline earth metal salts such as calcium silicate and barium carbonate (for details, see the specification of Japanese Patent Laid-Open No. 197500/1982).
  • the amount of the gas adsorbed in the carbonized resin was 2.1 cm 3 /g prior to the degassing step.
  • the uniaxial compression strength is reduced slowly as the residue of the adsorbed gas increases and the feed amount of the carbonized resin per unit volume is reduced as the residue of the adsorbed gas increases. This corresponds to the amount of the bubbles generated by the gas desorbed from the carbonized resin. Further, it is apparent that the reduction in the uniaxial compression strength is due to the bubbles.
  • the residue of the adsorbed gas should be controlled to up to 59%. Also, to pack the waste in an amount of at least 110 kg in a 200 I drum, the residue of the adsorbed gas should be controlled to up to 50%.
  • the immersion time of the carbonized resin in the alkali silicate solution necessary for the 50% release was determined.
  • the residue of the adsorbed gas observed after the immersion in the alkali silicate solution is shown in Fig. 9. The immersion was effected under three different conditions, i.e. without stirring, under stirring and under both stirring and heating.
  • the quantity of the adsorbed gas was reduced with time.
  • the reduction rate of the quantity of the gas was as follows: (without stirring) ⁇ (under stirring) ⁇ (under both stirring and heating).
  • the residue was reduced to 50% or below which satisfies the above-mentioned requirements of the feed amount and strength within 2 h in the cases of "under stirring” and “under both stirring and heating” and in 3 h in the case of "without stirring".
  • the effects similar to those obtained by stirring were obtained also by an ultrasonic treatment.
  • the mechanism of the variation of the degree of reduction of the adsorbed gas depending on the immersion conditions is as follows:
  • the carbonized resin is covered by the desorbed gas and the cover thus formed inhibits the adsorption of water in the carbonized resin to inhibit the release of the gas.
  • the gas covering the carbonized resin is removed to accelerate the release of the gas.
  • the release of the gas is accelerated, supposedly because water is converted into water vapor and the rate thereof to diffuse into the carbonized resin is increased.
  • the above-mentioned results indicate that when the carbonized resin is immersed in the alkali silicate solution, at least 50% of the gas adsorbed therein can be released in 3 h.
  • the treated resin can be solidified with the hardening agent to form a solidified product having a high strength and a large feed amount.
  • the desorption time of the gas can be shortened by stirring or heating.
  • the carbonized, powdery ion exchange resin and pellets obtained by compression granulation of the carbonized resin can also be degassed in the same manner as in the above-described defoamation of the carbonized granular ion exchange resin.
  • Fig. 10 The results of the degassing are shown in Fig. 10. This degassing process was effected at 25°C and the diameter of the granular ion exchange resin was about 30 um.
  • the pellets were columnar and had both height and diameter of about 20 mm. To reduce the residue of the adsorbed gas in the pellets to 50% or less, the treatment time of about 4 h is necessary.
  • the carbonized, powdery ion exchange resin can be degassed in a period of time shorter than that required for the degassing of the carbonized, granular ion exchange resin.
  • the pellets cannot be degassed sufficiently by merely stirring in some cases.
  • the residue of adsorbed gas in the pellets can be reduced to 20% or less by vacuum suction of the gas adsorbed therein and then introducing a mixture of the alkali silicate solution and the hardening agent therein and, thus, the intended solidified product having a large feed amount and a high strength can be obtained.
  • the adsorbed gas in the carbonized powdery and granular ion exchange resins can be released by previously immersing them in the alkali silicate solution and the intended solidified product having a large feed amount and a high strength can be obtained.
  • the pellets can be degassed by the vacuum degassing more effectively and then it is immersed in the alkali silicate solution to obtain a solidified product having a large feed amount and a high strength.
  • a hydraulic substance such as cement
  • Portland cement is used usually as the cement, which can be hardened by mixing with water. Since cement is in the form of a powder, the carbonized resin is immersed previously in water to release the gas from the resin.
  • Fig. 11 shows a change of the residue of the adsorbed gas in the carbonized granular ion exchange resin with time.
  • the experiments were carried out under three different conditions, i.e. without stirring, under stirring and under both stirring and heating, in the same manner as in Fig. 9. The time required for the degassing was shorter than that required when the alkali silicate solution was used.
  • the residue of the adsorbed gas was reduced to 50% or less in 2 h.
  • the cement is added to the degassed carbonized resin to harden the resin and to obtain a solidified product.
  • the resulting solidified product comprises 40 wt.% of the cement, 20 wt.% of water and 40 wt.% of the carbonized resin.
  • the relations between the residue of the adsorbed gas in the carbonized resin and the uniaxial compression strength of the solidified product and between the former and the feed amount of the obtained solidified product are the same as in Fig. 8.
  • the solidified product having a large feed amount and a high strength can be obtained also when the cement is used.
  • Fig. 12 shows the degassing rates of the carbonized resins and the pellets determined at 25°C.
  • the carbonized powdery ion exchange resin can be degassed by immersion in a shorter period of time. The time necessary for reducing the residue of the adsorbed gas in the pellets was about 3 h. However, the degassing cannot be effected sufficiently by the mere stirring in some cases.
  • the residue of the adsorbed gas in the carbonized resin can be reduced to 20% or less and the solidified product having a large feed amount and a high strength can be obtained.
  • the product solidified with cement and having a large feed amount and a high strength can be obtained from the powdery or granular ion exchange resin by carbonizing the same and immersing the carbonized resin previously with water to release the adsorbed gas. Also, the product solidified with cement and having a large feed amount and a high strength can be obtained from the pellets by effectively degassing the same by vacuum suction.
  • a powdery ion exchange resin from a condensate purifier in a boiling water reactor was thermally decomposed to obtain a carbonized resin, which was then mixed with an alkali silicate as solidifying agent to solidify the same.
  • a flow sheet of the treatment system employed in this example is given in Fig. 1.
  • the spent powdery ion exchange resin (hereinafter referred to as powdery resin) 51 was in the form of a slurry, since it was discharged from a condensate demineralizer by back washing.
  • the powdery resin 51 was stored in a waste resin tank 52.
  • the powdery resin 51 in the form of about 10% slurry was fed into a dehydrator 54 through a valve 53 and centrifugally dehydrated therein to a water content of around 50%. Then, a given amount (about 200 kg on the dry weight basis) of the dehydrated powdery resin 51 was fed in a thermal decomposition device through a knife gate valve 55.
  • the thermal decomposition device comprised a reactor 56 of a batchwise fixed bed system have a capacity of about 1 m 3 and a heater 57.
  • the powdery resin 51 fed in the reactor 56 was heated to 300°C by means of the heater 57 for about 4 h to form a carbonized resin 58.
  • An inert gas such as nitrogen gas was fed in the reactor 56 through an inert gas inlet tube 80 and a valve 81 to carry out thermal decomposition of the ion exchange resin in the inert gas. Therefore, even when the heating temperature of the ion exchange resin is elevated to around 600°C, the ion exchange resin is not burnt and, accordingly, neither heat generation nor temperature runaway is caused unlike the process carried out in an oxygen atmosphere (see Figs. 4 and 5). Thus, no device is required for preventing the heat generation due to the burning or runaway of the temperature.
  • a waste gas comprising water from the powdery resin as well as H 2 S, SO., NH 3 , etc. formed by the decomposition of the ion exchange group was formed in the course of the thermal decomposition.
  • the waste gas was introduced in a waste gas treating device 60 through a valve 59 and treated therein.
  • the carbonized resin 58 was fed into a drum 62 through a knife gate valve 61.
  • the amount of the carbonized resin 58 was as small as about 120 kg, while the amount of the initial powdery resin was 200 kg (on the dry basis).
  • 72 kg of water was fed in the drum 62 from a supply water tank 63 to initiate degassing of the carbonized resin. In this stage, the mixture was stirred by means of stirring blades 64 so as to accelerate the degassing.
  • a powdery alkali silicate was fed therein through a solidifier hopper 65 and a powdery inorganic phosphoric acid compound was fed through a hardener hopper 66 in such amounts that the total of them would be 108 kg.
  • the carbonized resin, water, solidifier and hardener were mixed homogeneously by means of the stirring blades 64 to form a solidified product.
  • Fig. 13 shows a sectional view of the resulting solidified product and an enlarged sectional view thereof. It is apparent from Fig. 13 that the carbonized resin 58 was dispersed quite homogeneously in the solidifier 67 and no bubble was observed in the solidified product owing to the degassing effect.
  • the obtained solidified product had a sufficient strength of at least 150 kg/cm 2. It was understood from the results obtained in this example that the bubble-free, strong solidified product as shown in Fig. 13 could be obtained by homogeneously mixing 120 kg of the carbonized resin with 180 kg of the alkali silicate solidifier containing the hardener and water in the 200 I drum.
  • a solidified product was prepared in the apparatus shown in Fig. 1 in the same manner as above except that the defoaming step was omitted.
  • 120 kg of the carbonized resin was mixed homogeneously with 180 kg of the solidifier in the 200 I drum in this case, the solidified product was swollen in the course of the hardening and a part thereof ran over the drum.
  • the same procedure as above was repeated except that the amounts of the carbonized resin and solidifier were reduced to 60 kg and 90 kg, respectively and they were mixed together homogeneously in the 200 I drum to obtain a solidified product shown in Fig. 14.
  • the resulting solidified product contained a large amount of bubbles 68 in addition to the carbonized resin 58 and the solidifier 67.
  • the solidified product had a uniaxial compression strength of as low as 50 kg/cm 2 .
  • the powdery resin was thermally decomposed and then solidified homogeneously with an alkali silicate by a solidifying process and in a thermal decomposition device different from those used in Example 1.
  • a flow sheet of the treatment system employed in this example is given in Fig. 15.
  • the powdery resin 51 in the waste resin tank 52 was fed quantitatively in the form of about 10% slurry in a thermal decomposition device 70 through a slurry pump 69.
  • the thermal decomposition device 70 was a rotary kiln of continuous treatment type in which the temperature was kept at 200 to 400°C.
  • the slurry of the powdery resin fed therein was dried and thermally decomposed simultaneously to form the carbonized resin 58.
  • An inert gas such as nitrogen gas was fed in the thermal decomposition device 70 through the inert gas inlet tube 80 and the valve 81 so as to carry out the thermal decomposition of the ion exchange resin in the inert gas.
  • the waste gas formed in this step was sent to the waste gas treating device 60 through the valve 59 and treated therein in the same manner as in Example 1.
  • the obtained carbonized resin 58 was stored temporarily in a powder hopper 71. Thereafter, a given amount (600 kg) of the carbonized resin 58 was fed from the powder hopper 71 into a kneader 72 and, at the same time, 400 kg of a liquid alkali silicate containing no hardener was fed therein as the hardener from a hardener tank 73.
  • the degassing was effected in the blender 72.
  • the degassing was accelerated by stirring with the stirring blades 64 and by vibration with an ultrasonic vibrator 74 attached to the blender 72, since a longer time is required for the degassing of the liquid alkali silicate than that of water.
  • the degassing was completed in about 2 h.
  • 200 kg of a powdery inorganic phosphoric compound was fed from the hardener hopper 66 into the blender 72 to mix the same with the mixture of the carbonized resin 58 and the alkali silicate homogeneously. After completion of the mixing, about 300 kg of the obtained mixture was poured in each drum 62 to obtain a solidified product.
  • the solidified product obtained as above contained no bubbles and had a uniaxial compression strength of at least 150 kg/cm 2 as in Example 1.
  • the feed amount of the carbonized resin in a 200 I drum was 120 kg.
  • the thermal decomposition may be effected either batchwise or continuously in a thermal decomposition device such as a fixed bed furnace or a rotary kiln multistage furnace, that the carbonized resin may be mixed with the solidifier by either the in-drum method as in Example 1 or out-drum method as in Example 2 and that the degassing may be effected by mere standing, stirring, ultrasonic treatment, vacuum degassing or a combination of some of them.
  • any combination of the decomposition device means of mixing the carbonized resin and the solidified and the degassing means may be employed.
  • the powdery ion exchange resin was treated in Examples 1 and 2, a granular ion exchange resin thereof can be treated in the same manner as above.
  • granular resin from a drainage purifier in a pressurized water reactor was thermally decomposed to obtain a carbonized resin, which was then pelletized and the pellets were solidified with an alkali silicate solidifier in a drum.
  • a flow sheet of the treatment system employed in this example is given in Fig. 16.
  • the spent granular resin 76 from the waste resin tank 51 was dehydrated centrifugally in the dehydrator 54 in the same manner as in Example 1 and then fed into the reactor 56 and heated to 300°C with the heater 57 for about 4 h to form the carbonized resin 58.
  • An inert gas such as nitrogen gas was fed in the reactor 56 through the inert gas inlet tube 80 and the valve 81 to carry out thermal decomposition of the ion exchange resin in the inert gas.
  • the carbonized resin 58 was fed into a powder mixer 77 through the knife gate valve 61.
  • a binder 79 was added thereto in an amount of about 20 kg for 100 kg of the carbonized resin through a binder hopper 78.
  • the binder 79 was used for improving the toughness of the pellets prepared in a granulator 80a.
  • the binder used in this example was a cellulose fiber having a thickness of about 101tm and a length of about 300 pm.
  • a binder other than the cellulose fiber such as a fibrous substance, e.g. metal fiber or carbon fiber, or a thermosetting or thermoplastic resin usually used as an adhesive is used.
  • a homogeneous mixture of the carbonized resin 58 and the binder 79 prepared in the powder mixer 77 was fed into the granulator 80a through the knife gate valve 81.
  • the granulator 80a herein used was an ordinary tableting machine in which the powder was pressed into pellets under a pressure of about 5 ton/cm 2 .
  • the mixture of the carbonized resin and the binder was shaped into columnar pellets 82 having both height and diameter of about 20 mm in the granulator 80a and the pellets 82 were fed into the drum 62 through a chute 83.
  • the drum 62 was placed in a vacuum housing 84. After confirming that the drum 62 was filled with the pellets 82, the housing 84 was evacuated with a vacuum pump 85. After completion of the vacuum defoaming of the carbonized resin, 80 kg of a mixture of an alkali silicate solidifier and an inorganic phosphoric compound as hardener was fed from a solidifier feeding tank into the drum 62 through a valve 87 while the vacuum condition was kept to obtain a solidified product.
  • the pressure in the vacuum housing 84 was returned to an atmospheric pressure by a leak valve 88 and the drum 62 was taken out and left to stand to effect curing. After about one month, the properties of the obtained solid were examined to find that the gaps between the pellets were entirely filled up with the solidifier and no bubbles were contained therein.
  • the solidified product had a uniaxial compression strength of at least 150 kg/cm 2 .
  • the carbonized resin which was compression-molded into the pellets 82 as described above could be feed in an amount of up to 150 kg in the 200 I drum.
  • the tableting machine used in this example may be replaced with a briquetting machine or extruder.
  • the pellets 82 may be treated by another method wherein they are stored in a large tank as such for a given period of time (usually 5 to 10 years) to decay the radioactivity before solidified in the drum or the like, if necessary. This method is generally called “intermediate storage” and has advantages which will be stated below.
  • the ion exchange resin When the ion exchange resin is dried and pelletized directly, the resulting pellets absorb moiety in air and swollen to reduce its toughness during the storage, since the resin has a high hygroscopicity. On the contrary, the carbonized resin from which the ion exchange group has been removed does not absorb the moiety in air and, therefore, the toughness of the pellets is not reduced in the course of the storage, since the carbonized resin is hydrophobic as described above. This effect is quite advantageous. In Fig. 17, the toughness of the pellets of the untreated resin during the intermediate storage is shown in comparison with that of the pellets of the carbonized resin.
  • the alkali silicate used as the solidifier in the above Examples 1 to 3 may be replaced with a hydraulic substance such as cement or gypsum.
  • the alkali silicate proved to be the best solidifier.
  • the high-sulfate slug cement, alumina cement, Portland cement and calcined gypsum are called "hydraulic solidifiers", since they solidify upon reaction with water.

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  • Processing Of Solid Wastes (AREA)
  • Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
  • Excavating Of Shafts Or Tunnels (AREA)
  • Fertilizers (AREA)
EP85904280A 1984-08-31 1985-08-28 Method of and apparatus for treating radioactive waste Expired - Lifetime EP0192777B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP59180561A JPS6159299A (ja) 1984-08-31 1984-08-31 放射性廃棄物の処理方法および処理装置
JP180561/84 1984-08-31

Publications (3)

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EP0192777A1 EP0192777A1 (en) 1986-09-03
EP0192777A4 EP0192777A4 (en) 1986-10-02
EP0192777B1 true EP0192777B1 (en) 1990-08-22

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EP85904280A Expired - Lifetime EP0192777B1 (en) 1984-08-31 1985-08-28 Method of and apparatus for treating radioactive waste

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EP (1) EP0192777B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
JP (1) JPS6159299A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
KR (1) KR870700248A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DE (1) DE3579312D1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
WO (1) WO1986001633A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)

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JP4322735B2 (ja) * 2004-05-27 2009-09-02 株式会社東芝 放射性廃棄物の固化処理方法及び固化処理装置
JP2012149168A (ja) * 2011-01-19 2012-08-09 Toshiba Corp クロムを含む廃イオン交換樹脂の処理方法及びその処理装置
CN103219059B (zh) * 2013-04-10 2016-04-20 中广核工程有限公司 放射性废树脂计量系统
CN104064239B (zh) * 2014-07-14 2018-05-29 中广核工程有限公司 一种核电站低中水平放射性活性炭处理方法
KR101776905B1 (ko) 2017-06-09 2017-09-08 (주)한국원자력 엔지니어링 중ㆍ저준위 방사성 폐기물 탄화시스템에서 발생된 탄화부산물의 고화장치

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JPS5682500A (en) * 1979-11-08 1981-07-06 Kernforschungsz Karlsruhe Method of solidifying radioactive ion exchanging resin with cement
JPS578498A (en) * 1980-06-19 1982-01-16 Hitachi Ltd Pelletizing method of radioactive liquid waste

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US3865745A (en) * 1971-01-15 1975-02-11 Grace W R & Co Process for the preparation of metal carbide and metal oxide microspheres
US4008171A (en) * 1973-09-10 1977-02-15 Westinghouse Electric Corporation Volume reduction of spent radioactive ion exchange resin
AT338387B (de) * 1975-06-26 1977-08-25 Oesterr Studien Atomenergie Verfahren zum einbetten von radioaktiven und/oder toxischen abfallen
AT338388B (de) * 1975-06-26 1977-08-25 Oesterr Studien Atomenergie Verfahren und vorrichtung zur uberfuhrung von radioaktiven ionenaustauscherharzen in eine lagerfahige form
US4053432A (en) * 1976-03-02 1977-10-11 Westinghouse Electric Corporation Volume reduction of spent radioactive ion-exchange material
JPS54157000A (en) * 1978-05-31 1979-12-11 Tokyo Electric Power Co Inc:The Method of waste disposal of ion-exchange resin having radioactivity
JPS6041320B2 (ja) * 1980-04-30 1985-09-14 住友重機械工業株式会社 重水減速型原子炉に於ける廃イオン交換樹脂の処理方法
SE425708B (sv) * 1981-03-20 1982-10-25 Studsvik Energiteknik Ab Forfarande for slutbehandling av radioaktivt organiskt material
JPS58155398A (ja) * 1982-03-12 1983-09-16 株式会社日立製作所 放射性廃棄物の固化方法
JPS58166299A (ja) * 1982-03-27 1983-10-01 株式会社日立製作所 放射性廃棄物の無機性固化剤による固化方法
JPS59107300A (ja) * 1982-12-10 1984-06-21 株式会社日立製作所 放射性廃樹脂の処理方法および装置
JPH0230680B2 (ja) * 1983-05-18 1990-07-09 Ngk Insulators Ltd Hoshaseihaikibutsunoshorihoho

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JPS5682500A (en) * 1979-11-08 1981-07-06 Kernforschungsz Karlsruhe Method of solidifying radioactive ion exchanging resin with cement
US4483789A (en) * 1979-11-08 1984-11-20 Kernforschungszentrum Karlsruhe Gmbh Method for permanently storing radioactive ion exchanger resins
JPS578498A (en) * 1980-06-19 1982-01-16 Hitachi Ltd Pelletizing method of radioactive liquid waste

Also Published As

Publication number Publication date
EP0192777A4 (en) 1986-10-02
JPS6159299A (ja) 1986-03-26
DE3579312D1 (de) 1990-09-27
KR870700248A (ko) 1987-05-30
WO1986001633A1 (en) 1986-03-13
EP0192777A1 (en) 1986-09-03
JPH0448199B2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1992-08-06

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