JPS6055039B2 - How to remove sodium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing sodium adhering to equipment that handles sodium, such as a cooling circuit for a nuclear power plant that uses metallic sodium (hereinafter simply referred to as sodium) as a coolant.

As is well known, nuclear power generation uses the heat generated by the nuclear fission chain reaction in a nuclear reactor to create high-temperature, high-pressure steam, which turns a turbine and generates electricity.

One method uses molten sodium as a coolant,
Coolant is circulated within the reactor to extract the heat generated in the reactor, which is led to a heat exchanger to heat water in the secondary cooling circuit, and the resulting high-temperature, high-pressure steam is sent to the turbine. There is a way to guide it to generate electricity.

In such a device, during inspection and maintenance, it is necessary to extract the sodium in the cooling circuit and remove the sodium adhering to the inside.

A known method for removing attached sodium is, for example, washing with alcohol such as methanol, ethanol, isopropanol, butanol, etc. to dissolve and remove sodium as alcoholade. Alcohol containing alcoholade can be distilled to recover the alcohol.

Alternatively, alcohol can be recovered by reacting alcohol containing alcoholate with carbon dioxide gas to precipitate sodium as carbonate and separating it from alcohol. However, these methods are not necessarily advantageous as industrial alcohol recovery methods.

The present inventors efficiently treated sodium adhering inside a device that uses sodium as a heat medium using alcohol, and industrially advantageously removed sodium ions from the alcohol solution containing sodium ions after treatment and recovered alcohol. As a result of extensive research into methods for doing this, we have arrived at the present invention. That is, the present invention cleans equipment that handles sodium, such as a heat exchanger that uses sodium as a heat medium, with hydrous alcohol to dissolve and remove adhering metallic sodium, and the hydrous alcohol containing sodium ions that is discharged is treated with acidic ions. The present invention relates to a method for efficiently removing sodium by recycling alcohol by treating it with an ion exchange resin to remove sodium ions and then using it again for cleaning. To explain the present invention in detail, in the present invention, the hydrous alcohol used for cleaning equipment on which sodium is attached is usually methanol containing 2 to 30% by volume, preferably 2 to 2% by volume of water. Lower alcohols such as , ethanol, isopropanol and butanol are used, and these can be used alone or as a mixture. Also, these alcohols may be mixed with other organic solvents. may be combined.

Note that alcohols with a water content lower than 2% by volume can be used, but such alcohols have a low dissolution rate of sodium and also reduce the ability of the acidic cation exchange resin to adsorb sodium ions.

Follow. For safety reasons, it is preferable to use alcohol containing 2% by volume or more of water, unless the dissolution rate of sodium is particularly low. Further, since alcohol with a water content of more than 30% by volume has too high reactivity with sodium and is dangerous, it is preferable to avoid its use as much as possible.

From the viewpoint of safety during washing and adsorption capacity of the ion exchange resin, it is preferable to use alcohol containing 2 to 5% by volume of water.
A conventional method may be used to clean equipment on which sodium is attached using hydrous alcohol, but since hydrous alcohol is more reactive than anhydrous alcohol, care must be taken to remove generated hydrogen gas.

The acidic cation exchange resin used in the treatment of hydrous alcohol containing sodium ions discharged from the cleaning process is Diaion SK/B (Diaion is manufactured by Mitsubishi Chemical Corporation).
Co., Ltd.'s registered trademark) PK228. Strongly acidic cation exchange resins such as the same JHPK4O and Diamondion WKlO, the same W
Examples include K2 Maki's weakly acidic cation exchange resin.

A column packed with these resins was heated at room temperature and S.p. V. 2～
50 hr-1, preferably S. V. 5~2011r-1
When water-containing alcohol containing sodium ions is passed through the solution at a flow rate of , the sodium ions are easily removed and the water-containing alcohol is regenerated. This hydrous alcohol can be reused as it is as alcohol for dissolving sodium adhering to the device. As described above, according to the method of the present invention, sodium adhering to the cooling circuit, etc. of a nuclear power generation device can be easily removed.

Next, the present invention will be explained in detail using test examples, but the present invention is not limited to the following test examples unless it exceeds the gist thereof.

Test Example 1 Hydrous ethanol containing 2300m9/e of sodium was placed in a glass column with an inner diameter of 15Tn1 and a height of 100" packed with 100mt of strongly acidic cation exchange resin (Diaion SK/B, .H type) collected in ethanol. 50% solution
Table 1 shows the effective column exchange capacity of the resin when flowing at a flow rate of 0 ml/hour.

The effective column exchange capacity is defined as the amount of sodium adsorbed by a unit volume (volume in ethanol) of the ion exchange resin until the sodium concentration in the treated solution exceeds 10% of the sodium concentration in the solution before treatment. It is a value that represents

Moreover, the water content is a value measured by the Karl Fischer method. 1 Test Example 2 A container with an inner diameter of 30mm filled with 500ml of strongly acidic cation exchange resin (Diaion SK/B...H type) collected in ethanol. , in a glass column with a height of 1000writ,
An ethanol solution containing sodium ions was passed through the tube.

Table 2 shows the amount of liquid that flowed out until the sodium concentration of the effluent exceeded 10% of the original solution. Test Example 3 Table 3 shows the time required for the sodium metal to completely decompose when 500 mg of sodium metal cut into cubes was added to 100 ml of water-containing ethanol prepared at various moisture contents.

Claims (1)

[Scope of Claims] 1. A method for removing metallic sodium adhering from equipment handling metallic sodium, which comprises washing the equipment with aqueous alcohol to dissolve the metallic sodium, and removing the aqueous alcohol containing sodium ions to be discharged. A method for removing sodium, which comprises removing sodium ions by contacting with an acidic cation exchange resin, and recycling the hydrous alcohol treated with the resin for cleaning. 2. The method for removing sodium according to claim 1, wherein the device for handling metallic sodium is a device using metallic sodium as a heat medium. 3. In the method for removing sodium according to claim 1 or 2, the hydroalcohol content is 2 to 30% by volume.
A method characterized by containing water of 4. The method for removing sodium according to claim 1 or 2, wherein the hydrous alcohol contains 2 to 5% by volume of water. 5. The method for removing sodium according to any one of claims 1 to 4, characterized in that the alcohol is ethanol.