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Wednesday, 30 July 2014

From Jul. 9, 2014 Nuclear Waste Disposal

Japanese politicians have been debating scrapping the country's nuclear reactors since the 2011 Fukushima Daiichi disaster. Now, Prime Minister Shinzo Abe says the country will push for nuclear power generation as a key energy source.

Nuclear Watch looks at the issue of the toxic radioactive waste these facilities produce. NHK WORLD's Yoichiro Tateiwa reports.

Located near Japan's northernmost point, Horonobe, Hokkaido is a small dairy farm town. Here, researchers of the Japan Atomic Energy Agency are studying the possibilities for the final disposal of radioactive waste.

Workers at a facility that opened in 2003 have dug 380 meters into the ground.
Researchers are looking into whether nuclear waste can be safely stored.

Japan's nuclear energy policy says spent nuclear fuel must be reprocessed and recycled as fuel. In reprocessing, workers extract plutonium and uranium as recyclable substances, leaving behind highly toxic wastewater. Researchers mix that with heated glass and pour the high-level radioactive waste into steel containers.

Each unit is 1.3 meters in height and 500 kilograms in weight. And they emit radiation at an extremely high level...enough to kill a person within 20 seconds.

"Regardless of Japan's nuclear energy policy, highly radioactive nuclear waste must be disposed of. We have to ensure that such waste does not harm the human environment."
Naotaka Shigeta / JAEA Horonobe Underground Research Dept.

Natural uranium is enriched and becomes nuclear fuel.
Radioactivity reaches highest when fuel generates power in a nuclear plant. After the fuel is removed from a nuclear reactor, it is reprocessed and nuclear waste is left. It is kept cooling for about 50 years until the temperature is brought down to less than 100 degrees Celsius. Then it is transported to an underground depository site. Experts say it would take 100,000 years for the level of radioactivity to return to that of natural uranium.

Researchers here study the movement of geological strata and underground water. Workers have to pump up 120 tons of underground water daily. They also assess the durability of materials around the nuclear waste units, to ensure that radioactivity does not escape.

The 2-kilometer-by-3-kilometer underground storage facility has a capacity of 40,000 units. The total length of its tunnels is 270 kilometers.
Researchers hope to find out what impact an earthquake would have on the facility. They installed seismometers at the site and monitor tremors constantly.

"Radioactive waste stored here will have been processed into perfectly solid form, so the glass units will shake with the facility. This means an earthquake would not destroy them."
Naotaka Shigeta / JAEA Horonobe Underground Research Dept

But members of the country's most prestigious science association are voicing their concerns about deep repository systems.
They say it's hard for Japan to build a facility in a region that's prone to earthquakes and volcanic activity.
They recommend that Japanese leaders look for other technological developments to safely store waste.

Japan has 1,700 glass nuclear waste units. The number would rise to 27,000 if all spent fuel rods currently stored at nuclear plants were processed. Japanese leaders must decide where and how to safely store the waste.

Researchers at Horonobe plan to start an experiment using simulated waste units later this year. They say real nuclear waste will never be used here.
The research agency and the local government agreed that radioactive materials will never be brought into the township.
The idea of storing nuclear waste underground is debated around the globe. Only Finland and Sweden have chosen construction sites for such facilities.


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