JPH0641999B2 - Solidification method for radioactive waste incineration ash - Google Patents

Description

Detailed Description of the Invention

 Purpose of the invention

[Industrial applications]

The present invention relates to an improved method for solidifying radioactive waste incineration ash in a form compatible with final storage and land disposal.

[Prior art]

For example, polyethylene sheets, paper waste, cloth waste, work clothes, etc.
Combustible solid waste with low levels of radioactivity is generated. Conventionally, these wastes were compressed and stored in drums, but since the amount of these wastes has increased recently, they are incinerated and volume-reduced from the viewpoint of effective utilization of the storage space for drums. ing. The incineration ash with this low level of radioactivity is stored in drums. As means for final storage of waste incineration ash until the radioactivity falls to a safe level and further land disposal, for example, a plastic solidification method or a solidification method by microwave melting or high frequency induction heating melting is proposed. ing. As a plastic solidification method, for example, there is a method in which incineration ash and a solidifying agent (unsaturated polyester resin) are mixed and stirred, then placed in a drum, and then a hardening agent is injected and stirred by a rotary blade to solidify. This method has a drawback in that if unburned carbon or water is present in the incineration ash, the curing of the plastic is hindered, and therefore the compounding ratio is limited and the degree of volume reduction cannot be increased. In addition, this method has a problem in handling such as taking out and transporting incinerated ash from the drum as it is a powder. The solidification method by melting is a method in which the incineration ash is irradiated with microwaves or heated by high-frequency induction heating to a high temperature, and then melted and solidified. Although this method is excellent in terms of volume reduction and physical properties of the solidified product, it is also difficult to handle and costly. As another means, there is a solidification treatment method using cement, but in the conventional technique, since the incineration ash and the solidifying agent are mixed by out-drum mixing, scattering of the incineration ash when driving the mixer or waste liquid from the mixer washing In addition to handling problems, new problems arise, such as the disposal of secondary waste (which is also radioactive). In addition, soluble solids in the incinerated ash, lead, zinc, etc. may cause embrittlement of the cement solidified product or cause poor setting of cement.

[Problems to be Solved by the Invention]

The object of the present invention is to solve the problems that have been associated with the solidification treatment method of ash incinerated from wastes having low levels of radioactivity, and to handle easily, and to worry about scattering of incinerated ash and treatment of cleaning wastewater. It is an object of the present invention to provide a treatment method capable of producing a solidified body which is easy to handle and which is easy to handle at low cost. Structure of the invention

[Means for solving problems]

The solidification method of radioactive waste incineration ash of the present invention is to inject cement mortar or paste (hereinafter represented by "cement paste") into a drum containing the incineration ash of radioactive waste, and rotate or rotate and vibrate the drum. The mixture of incinerated ash and cement paste is granulated in the drum can by giving the above, the resulting granular material is cured in the drum can, the cement paste is injected again after waiting for its solidification, and the drum can is vibrated to give cement. It consists of filling the gaps of the solidified granules with paste and curing to solidify. That is, the treatment method of the present invention, the first step of granulating and solidifying the incineration ash with cement paste, the second step of further filling the cement granules with cement paste to solidify the whole, from two stages Become. The purpose of the cement paste, which is injected in the first step, is to granulate while preventing the incineration ash from scattering and to solidify it to a point where it has a temporary strength. Depending on the degree, no incineration ash remains without being granulated, while it is appropriately selected within the range in which substantially no free water is generated. The cement is selected from ordinary ones such as Portland cement and used.
Of course, other hydraulic materials may be used in combination. The cement paste used in the second step can also be prepared using any cement. It is also useful to add an appropriate amount of aggregate such as sand in order to reduce heat generation and increase the strength of the solidified body. Further, in order to enhance the fluidity, it is preferable to add a fluidizing agent. As the fluidizing agent, a water reducing agent which is used as an additive in the construction of concrete or mortar in civil engineering or construction work, especially when pouring grout material is effective. Optimal use conditions could be readily determined by following the instructions for each water reducing agent. Injecting the cement paste in the first step is usually carried out for the necessary time, taking care not to scatter the incinerated ash from the upper part of the container. The injection amount is suitably in the range of 0.6 to 1.6 with respect to the incineration ash. When there is not enough space for injecting the cement paste in the upper part of the container, it is effective to apply the vibration in advance to lower the surface of the incineration ash and then inject it while further applying the vibration. After the cement paste is injected, or preferably at the same time as the injection, the incinerated ash is granulated into the same mass having a diameter of about 5 to 100 mm by rotating and / or vibrating the container. The rotation is preferably performed by inclining the container with respect to the vertical axis by 45 to 90 °, and the rotation speed is preferably a slow speed of about 5 to 30 rpm. When vibration is applied, the frequency is 3,000-7,000 v.pm and the amplitude is 0.5-
3.0 mm is suitable. It is preferable to use both rotation and vibration in order to promote the granulation. Granules of incinerated ash are brittle and easily collapsed immediately after formation,
Let it stand for at least 24 hours, and once it has solidified, move to the second step. The injection of the cement paste in the second step may be performed from the top of the container, but insert a pipe toward the bottom of the container, or provide a pipe in advance, use it to bottom or middle It is also preferable to inject from. Since vibration is applied to the container at the time of injection or subsequent to injection, it is the work of filling the space between the solidified particles of cement paste and expelling the air bubbles so that no cavities are formed. It is advantageous to select a condition in which the amount of vibration is small in order to shorten the time required for vibration and obtain a reliable effect. To apply the vibration, an appropriate vibration generating means such as a vibration motor or an air vibrator is used. In order to treat a large amount of incinerated ash, it is necessary to prepare a dedicated vibrating table to vibrate the entire container, but if the target is a small amount, contact the vibrating means with the bottom or side wall of the container. It is also possible to apply vibration by applying. Since the vibration in the second step does not cause the scattering of incineration ash, the range of selection of frequency and amplitude can be widened. Generally, it is appropriate that the frequency is 3,000 to 7,000 v.pm and the amplitude is 0.5 to 3.0 mm.

[Work]

The cement paste mixes with the incineration ash by rotation and / or vibration and acts as a binder to form granules. As a result, the incineration ash loses its scattering property and becomes a form that can be easily handled. If left unattended, this granular material will have a certain strength as the cement solidifies, so that it is possible to further solidify the surroundings by filling the cement paste with vibration. In this way, a form of radioactive waste incineration ash suitable for final storage and land disposal is provided.

【Example】

1. A 50-drum can containing 30 volumes of simulated incineration ash was injected with 1/2 of the volume ratio of cement mortar to the incineration ash. Cement mortar has the following composition. “Dencatascon” premix 84.7 parts by weight Water 15.3 〃 (The above premix is cement 36.6% by weight, sand 41.2%, “Dencatascon” 4.5% and water 1
It has a composition of 7.7%. ) The drum was closed, its axis was tilted at 90 ° with respect to the vertical, and the drum was rotated at a rotation speed of 10 rpm for 30 minutes. In each case, a granular material in which incineration ash was bonded was obtained. Particle size is 10
It was in the range of ~ 30 mm. 2. The same cement mortar with a volume ratio of 2/3 to the incinerated ash is poured into a 50-drum can containing 30 of the same simulated incinerator ash by volume, and the same cement mortar as described above is injected and sealed, and then the shaft is vibrated with the axis kept vertical. Using a machine, a vibration having a frequency of 6,000 v.pm and an amplitude of 1.0 mm was applied for 30 minutes. The particle shape and particle size are 1. Somewhat more irregular, but similar granules were obtained. 3. The granules of 1 and 2 were left to stand in a drum at room temperature for 2 days, and waited for solidification of the granules. Then, the same cement mortar as above was injected while vibrating at a frequency of 6,000 v.pm and an amplitude of 1.0 mm using a vibrator. It was observed that there was no disintegration of the granules and the cement mortar filled the voids well. 4. After the injection, the drum was left at room temperature for one month and then cut to cut the solidified body into vertical pieces. From the observation of the cross section, it was confirmed that the particulate matter was stably fixed in the cement mortar with good airtightness. The compression strength of the solidified body was 150 kg / cm ² or more. Effects of the Invention If the incineration ash of radioactive waste is solidified by cement according to the solidification method of the present invention, there is no handling problem such as scattering of the incineration ash, and the waste incineration ash stored in a container such as a drum can is solidified as it is. can do. Not only the out-drum mixer but also the rotor for in-drum mixing is not required, so there is no equipment cost and no problem of treatment of washing water. In the obtained solidified product, the cement paste fully fills the voids of the granular material, and there are substantially no harmful cavities, and its strength is sufficient for subsequent transportation and storage. Moreover, since the cement-based solidifying agent is available at a low cost, the cost of the solidified body is low. In this way, safe storage and disposal of incineration ash of radioactive waste is realized easily and at low cost.

Claims (1)

[Claims] 1. A cement can is produced by injecting cement paste into a drum that contains incinerated ash of radioactive waste and rotating or rotating and vibrating the drum to granulate the mixture of incinerator ash and cement paste in the drum. The granules are cured in a drum can, the cement paste is injected again after waiting for its solidification, and the cement paste is filled in the gaps of the solidified granules by applying vibration to the drum can,
A method for solidifying radioactive waste incineration ash, which consists of curing and solidifying.