JPS6337360B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for treating radioactive organic waste.

At 600-1100 °C, excess water vapor is countercurrent in a closed furnace to ash the organic components, and the exhaust gas is passed through the temperature band 800-1100 °C again for post-reaction, radioactive contamination ions. Methods of treating exchange resins by pyrolysis have already been proposed.

The nuclear industry generates a large amount of contaminated organic waste (paper, rags, plastics, gloves, etc.) that, despite being bulky and containing relatively little radioactive material, cannot be disposed of using conventional methods. I can't. In particular, wastes containing highly toxic plutonium or artificial radionuclides are mentioned. The aim of all methods of treating such waste is to reduce the volume by ashing and remove the ash residue without generating contaminated exhaust gases or radioactive wastewater.

According to the proposal, the treatment of radioactively contaminated organic waste is achieved by gasification of the organic components in a closed furnace arrangement at 600-1100°C with an excess of water vapor flowing countercurrently, with the exhaust gases being For post-reaction, pass through the temperature zone of 800-1100℃ once more.

Nuclear industrial equipment such as power reactors and reprocessing units generate large quantities of radioactively contaminated ion exchange resins from water treatment equipment that are depleted in one or more loads and sent to final storage. There must be. These contain radioactive substances, especially in the form of radioactive heavy metal ions.

Terminal storage of this radioactive resin as a deposit is not permitted. These must be mixed with the fixative and filled into containers. The solids obtained in this way are subject to high demands on strength and leaching stability.

Due to increasingly demanding storage conditions and the anticipated increase in storage costs in the future, it is imperative to reduce the amount of waste. This is only possible by reducing the volume of waste material before introducing it into the fixation material.

In the case of radioactive ion exchange resins, this is achieved according to currently known methods by starting from a swollen, water-rich state, such as that generated from nuclear industrial equipment, and drying the resin. However, the volume reduction achieved with this method is approximately 50% of the starting volume.
It only reaches %. Even with other known heat treatments, the volume reduction is only to the above extent. Moreover, in this case, an exhaust gas problem arises which is difficult to treat.

The above-mentioned proposal for completely ashing organic waste from nuclear reactors by high-temperature hydrolysis is also not optimal for treating radioactively contaminated ion exchange resins. This is because, during complete ashing, most of the radioactivity is transferred to the exhaust gas or exhaust gas filter, which then needs to be ashed anew.

It is therefore an object of the present invention to provide a method for reducing the volume of radioactively contaminated ion exchange resins so that radioactive exhaust gas problems do not occur.

This purpose is to carry out the high-temperature hydrolysis treatment of the ion exchange resin according to the above-mentioned proposal according to the present invention, by gasifying it with steam at 600-800°C until the volume of the charged ion-exchange resin becomes 4-10% by volume of the starting volume. This is solved by

The hyperthermal hydrolysis process is therefore stopped when 4-10% of the starting volume is still in the apparatus. This point can be determined purely optically or experimentally at a constant temperature and resin.

The method of the invention has the important advantage that no expensive exhaust gas treatment is required, since the radioactivity remains in the carbonized resin or only a small portion is transferred to the condensate and the exhaust gas is almost radioactive.

The evaporation residue remaining during evaporation of the condensate can advantageously be mixed with the carbonized resin and solidified at any time. Since the swelling power of the resin is lost due to carbonization, the volume does not increase by mixing with the evaporation residue. The final volume is therefore less than 10% of the starting volume of the ion exchange resin used in this case.

Next, the method of the present invention will be explained with reference to the drawings.

The device has, for example, a fluidized bed reactor 2 with a heating device 1, in which superheated steam is fed to the radioactive ion exchange resin. Steam is produced in an evaporator 3 and heated to a reaction temperature in a superheater 4. After leaving the fluidized bed reactor 2, the water vapor is sent to a two-stage spray condenser 5 together with condensable and non-condensable reaction products. Water vapor and condensable reaction products condense there. Non-condensable reaction products are filtered through adsorption filter 6.
is sent to the exhaust gas system via the gas and optionally processed.

The condensed liquid is sent back to the evaporator 3 and evaporated again. The water vapor generated during this process is sent back to the process. One substream of water vapor reaches the fluidized bed reactor again via superheater 4, the second substream is condensed in condenser 7 and subsequently sprayed via pump 8 and nozzle 9 into spray condenser 5. . This creates a closed circuit for the process medium water or steam.

The residual liquid in the evaporator 3 consists of condensable radioactive reaction products generated during carbonization of the ion exchange resin. This is withdrawn discontinuously into a storage tank 10 from where it is sent by pump 11 for mixing with the carbonized ion exchange resin.

The method of the invention will now be explained by way of example.

Example 1 Charge ion exchange resin particles into a fixed bed reactor and close the reactor. The reactor is heated to a temperature of 150°C by direct heating of the vessel wall to prevent condensation of water vapor within the reactor when steam is introduced. Next, superheated steam at 650℃ is introduced. The carbonization reaction lasts approximately 3 hours, after which time 8% of the starting volume is still present. The reactor is then cooled from the outer wall. The cooled reaction product can be removed. Since the radioactivity of the exhaust gas was reduced to at least 1/1000 of the radioactivity of the charged ion exchange resin, it could be released into the atmosphere through an adsorption filter without requiring any special post-treatment.

Example 2 Charge ion exchange resin to a fluidized bed reactor. The reactor is heated to a temperature of 180° C. by direct wall heating. When the reactor temperature has risen sufficiently, superheated steam at 700℃ is sent. Water vapor serves as a fluidizing gas and a reactant gas for the ion exchange resin. Since the reaction components are in sufficient contact, the carbonization time is approximately 1 at a residual volume of 7%.
time is reduced. Solid particles are obtained as individual particles. This structure facilitates mixing with the radioactive condensate and binding into the immobilized material.

After the carbonization process has ended, the reaction product can be cooled with a gas stream and then removed from the reactor. The exhaust gas could be treated in the same way as in Example 1.

When carbonizing acidic or alkaline ion exchange resins, the reaction gas must be neutralized, especially in the spray condenser 5, or the ion exchange resin must be mixed in such a way that a neutral reaction gas is generated.

Example 3 Ion exchange resins of different nature, for example acidic and alkaline resins, are mixed together. The mixture is carbonized in an apparatus under the reaction conditions of Example 1 or 2. In this case, for example, one generates SO ₃ and the other generates amine. If you adjust the mixture of ion exchange resin appropriately,
Chemically neutral reaction products are generated.

Example 4 An acidic ion exchange resin or a mixture of acidically reactive acidic and alkaline ion exchange resins is charged to a reactor and carbonized as in Example 1 or 2.

However, to neutralize the reaction products before the process vapor enters the reactor, use lime milk, powdered lime or Ca.
Supply (OH) ₂ aqueous solution.

Example 5 An acidic ion exchange resin or a mixture of acid-reactive acidic and alkaline ion exchange resins is charged to a reactor.

The carbonization process is carried out as in Example 1 or 2. The acidic gaseous reaction products are neutralized in a spray condenser.
For this purpose, milk of lime or Ca(OH) ₂ is supplied to the cooling water via a suitable metering device before it enters the spray nozzle 9.

[Brief explanation of the drawing]

The drawing shows the arrangement of equipment for carrying out the method of the invention. 2... Reactor, 3... Evaporator, 5, 7... Condenser.

Claims (1)

[Claims] 1. At 600 to 1100°C, excess water vapor is countercurrently flowed in a closed furnace to incinerate organic components, and the exhaust gas is heated again to a temperature range of 800 to 1100°C for post-reaction. In the radioactive organic waste treatment method, when treating radioactive ion exchange resin as radioactive organic waste, ashing with steam at 600 to 800 ° C.
A method for treating radioactive organic waste, characterized in that the volume of the charged radioactive ion exchange resin is 40 to 10% by volume of the starting volume, and the exhaust gas is discharged into the atmosphere without high-temperature post-treatment. 2. The method according to claim 1, wherein the radioactive condensed residual liquid generated in the closed circuit is mixed with carbonized resin and sent to a final storage facility. 3. The method according to claim 1 or 2, wherein the reaction product is neutralized during or after the reaction.