Toshiba Corp says it has developed a revolutionary new technology designed to decontaminate radioactive soil from the area surrounding the stricken Fukushima Daiichi nuclear power plant.
The technology was originally designed to purify radioactive water at the nuclear power plant, but its developers say it also removes 97% of cesium from radioactive soil.
Toshiba said in a statement that the device is currently capable of dealing with 1.7 tons of radioactive soil per day, but it is theoretically possible for a machine capable of processing 100 times that amount. The device uses crystalline adsorbents that have the ability to selectivity remove radioactive ions from liquids, soil and waste.
The equipment fits in a truck container
It pumps low-concentration contaminated water with a pump and removes radioactive caesium from the water in a container that stores adsorbent. It can process a ton of contaminated water in one hour and lower the density of radioactive caesium in the water to 10 becquerels per kilogram, which is the value that Japan’s Health, Labour and Welfare Ministry is considering to use as the new upper limit of the contamination of drinking water, or lower.
Toshiba also claims that the machine is capable of decontaminating radioactive ash from garbage incineration plants. The company hopes it will provide a nationwide solution to the problem of dealing with radioactive materials.
TBS reported that Toshiba plans to hold training conferences nationwide from next month to ensure that local governments and other associations across the country are able to properly operate the machinery.
The containers of adsorbent are being replaced.
The new system was developed by reducing the size of the “Sarry,” a polluted water treatment system being used at the Fukushima Daiichi Nuclear Power Plant. Toshiba and IHI reduced the number of active components such as pump and motor and realized stable and trouble-free operation, they said.
To ensure the safety of workers, a shield was installed inside the container that stores adsorbent used to remove radioactive materials such as caesium. The container is a general-purpose 200 liter drums and can be handled with a forklift, etc.
The new system can be transported by mounting all the equipment on an internationally-standardized 20-foot container (approximately 6.1 x 2.4 x 2.6m) and pulling the container with a truck. It can be used for processing swimming pool water and agricultural water containing radioactive caesium as well as water produced by decontamination. To sell the system in Japan, new legislation is required. So, Toshiba will start talks with the central government and local governments in January 2012.
Another Competing Cesium removal system
The technology separates cesium in water solution. First, water-soluble ferrocyanide, which works as an adsorbent, is added to cesium-contaminated water so that it is bonded with cesium. Then, the resultant material is reacted by using iron chloride, which is a material for magnetic substance.
When an alkaline solution is added to it, a magnetic material containing cesium is generated. By using a magnet for magnetic separation, cesium can be removed and collected from the contaminated water.
The new technology enables to remove cesium in a shorter period of time than technologies using solid adsorbents such as zeolite. And it is expected to reduce the amount of waste. Because the new technology uses a material that is highly available at a low cost, it is possible to reduce removal cost.
When JNC tested the technology by using water solution with a cesium concentration of about 10ppm, it took less than 10 minutes to generate a cesium-containing magnetic material and separate cesium from it. In one operation, 99.5% of the cesium was removed, the company said.
Currently, JNC is developing a cesium removal process for treating a large quantity of contaminated water.
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