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Sunday, December 23, 2012

Treatment of Radioactive Nuclear Waste

In addition to radiation, one of the most feared people when they hear about the nuclear word is radioactive waste because it wastes still have radiation activity that may be harmful to the human body. So, how exactly radioactive waste from nuclear energy was?

Before discussing it, radioactive waste itself based on the activities level are classified into three, namely low activity, moderate activity, and high activity waste. While based on the physical form, radioactive waste could be divided into solid, liquid, and gas. Each type of waste has a different way of handling.

Broadly speaking, radioactive waste management follow three main principles, namely decrease the volume, turn into a stable form of either physical or chemical. Furthermore, radioactive waste was transferred to a place isolated from the environment and continuously monitored.
Cycle of nuclear waste disposal. (Picture from: http://www.127sale.com/)
Nearly 99 percent of nuclear waste, especially from nuclear power plants, spent fuel derived from elements that still have high radioactivity, while the rest comes from protective clothing (armor), cleaning cloth, laboratory equipment, and hand-gloves that are not used. Although the waste is low-level radioactivity, but still have to be processed and then stored below ground level.

What about the stages of spent fuel waste that contains elements of high radioactivity?
  • First, the fuel elements that have been used removed from the reactor core with specialized equipment and is operated with a remote control or remote control.
  • Second, further spent fuel elements are placed in temporary storage pools that contain water, for about five years for the radiation cooling and decreased activity. "The water in addition to the cooling function also serves as a radiation shield to prevent radiation confinement system is not out of the pool," said Tri Cahyo Laksono, Officer at Radiation Protection Research Reactor TRIGA 2000, at Batan (Badan Tenaga Atom Nasional / Indonesian National Atomic Power Board) in Bandung on Monday (10/12).
  • Third, after five years of waste and spent fuel elements decreased levels of radiation, then moved to a storage area that is sustainable. Sustainable waste storage can be either concrete under the ground surface to a depth of approximately 1,000 meters.
In addition to storage management, today has developed recycling spent fuel elements in some countries. Recycling is intended to take back to divisive elements such as uranium, plutonium, americium, curium, and neptunium to be used as raw material of new fuel elements or for other industries.

For treatment of waste based on its physical form, of course done in a different way. For initial treatment, liquid waste generated during operation or refueling, accommodated in raw sewage holding tank and then processed by the process of evaporation, filtration equipped with ion exchange processes and chemical processing. Treatment of nuclear waste methods adapted to the characteristics of the waste.

The initial treatment will produce a concentrate or resin which is then conditioning in the appropriate waste container. There are many methods of conditioning, but the most common is the immobilization method using cement. While in Korea, conditioning only with dry concentrates and resin blended without cement.

For solid waste, can be classified into three, namely, combustible waste, solid waste can be compacted but can not be burned, and the solid waste can not be burned or compacted.

Waste that can be burned, burned in a reduced volume by incineration furnace at a temperature of 700 to 1,100 degrees Celsius. Flue gas generated from the combustion reaction is passed through several filters, such as bag house filter and a HEPA filter, so that almost 99.9 percent of the gas trapped in the filter. Furthermore, the gas in the form of the remains of acid neutralized with caustic soda. Then exhaust out of the chimney has been completely free of harmful components.

Combustion ash in the form of metal oxide immobilized with cement and
inserted to the 200 liter drums container. After that, waste that had been immobilized is stored in a temporary storage area. Compacting solid waste but can not be burned done by compaction. In many countries, the waste is collected in a 100 liter drum, compacting process may be done if the waste is collected much.

Once solidified in drums of 100 liters, solid waste is placed in a 200 liters container. After the compaction process, coral with certain specifications poured into the annulus formed, then mix sand cement paste is injected into the annulus and vibrated to ensure homogeneous infiltration of pasta. After that, the waste package is stored in a temporary storage area. For solid waste can not be burned or compacted, usually treated with directly immobilization method.

For gas waste, processed by the reactor by way of making use of radionuclides and activated carbon filter. Then filter and activated carbon that has been saturated sent to the radioactive waste management plant to be processed as a solid waste.
A Nuclear radioactive waste store under ground, thousands of barrels, are also put into specially built, buildings on land. (Picture from: http://abundantpureenergy.webs.com/)
In accordance with the principles of waste management, the final storage (disposal) as the end stage of radioactive waste management aims to isolate the waste so that no radiation exposure to humans or environments. Geological disposal facility located at depths of a few hundred to 1,000 meters below the ground surface or the term deep geological disposal. This facility should exist, devoted to the high activity waste containing long-lived radionuclides. *** [FEBY SYARIFAH | PIKIRAN RAKYAT 20122012]
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