Commercial-scale treatment of NPP heavy wastewater

 Heavy water reactors such as the Wolseong NPP in South Korea generate wastewater as intermediate-level radioactive waste. Waste paper is an ion exchange resin used to remove radionuclides in the process of treating liquids such as heavy water, and it contains carbon-14 (14C), a radioactive isotope. Due to the high concentration and large amount of radioactivity, it is impossible to dispose of it at the Gyeongju Radioactive Waste Disposal Center in Korea. 

It has been stored separately in storage tanks at the power plant for a long time, but the KAERI(Korea Atomic Energy Reserch Institute) has found a solution.

                                                                   Process Unit(Photo: Herald Corporation)
                                     

The research team of Dr. Hwan-seo Park of the Advanced Nuclear Cycle Technology Development Division has succeeded in demonstrating the world's first commercial-scale treatment of heavy water wastewater with the largest capacity, the institute announced on Friday.

In 2018, KAERI developed the 'Wastewater Treatment Source Technology through Microwave Irradiation'. This technology heats the ion exchange resin with microwaves to change its chemical structure and separate carbon-14. Based on this technology, a commercial-scale process was developed, and in February, the institute treated wastewater stored at the Wolseong Power Plant to separate, reduce, and recover 99 percent of the expensive radioisotope carbon-14. This demonstration is significant as it is the world's first commercial-scale treatment of wastewater that has been confirmed safe, licensed, and actually used.

Canada, China, and India, which operate heavy water reactors, are also conducting research on heavy water reactor wastewater treatment, but they are at the laboratory scale.

On the other hand, the research team focused on microwaves to effectively recover carbon-14 in the wastewater. Just as microwaves in a microwave oven irradiate food and generate kinetic energy to heat the food, the researchers found that when the wastewater is irradiated with microwaves for about two hours, a chemical reaction occurs and about 99% of the carbon-14 is separated.

For the demonstration, the team set up a microwave irradiation reactor about the size of a refrigerator inside a power plant, and then transferred wastewater from the wastewater storage tank to the microwave reactor. During the irradiation process, the carbon-14 in the wastewater is generated as a gas inside the device, which is then fed to an adsorbent, which recovers the carbon-14. The remaining wastewater will be classified as low-level waste and sent to the Gyeongju disposal site.

Wastewater stored in domestic heavy water reactors also contains a large amount of carbon-14, which is worth more than 1 trillion won. The technology developed by the research team opens the way for direct recovery of the expensive isotope, which is entirely imported, to be utilized in domestic industries or exported to foreign countries.

"This heavy water reactor wastewater treatment technology is one of the important research results to solve the problem of radioactive waste," said Ryu Jae-soo, head of the Advanced Nuclear Cycle Technology Development Division at the KAERI. 

Resouce : Koo Bon-hyuk in Herald Corporation