In recent months, former Prime Minister Junichiro Koizumi has rekindled the public debate on atomic power, drawing attention to perhaps the most critical question about its future: Is there a safe place and way to dispose of high-level radioactive waste?

Koizumi lashed out at the fact that the government has no plan to build a permanent waste repository, even though it is eager to restart the 50 remaining viable commercial reactors if they meet new safety standards.

Amid growing criticism, the government said it will draw up a basic nuclear energy policy by the end of January.

How much nuclear waste does Japan have and what risk does it pose? Following are some questions and answers about the hazards of nuclear waste:

What is radioactive waste?

The International Atomic Energy Agency defines it as any material that contains a concentration of radionuclides greater than those deemed safe by national authorities, and for which no use is foreseen.

Japan classifies radioactive waste mainly into two categories: high level, or that generated from reprocessing spent fuel by separating the plutonium and uranium for recycling, and low level, which refers to all other waste.

Low-level waste can vary from used control rods and reactor parts to used filters, liquid waste, used gloves and other gear.

How is the high-level waste processed?

High-level waste is a byproduct of fission in the reactor core, which is very hot and dangerous. It is mixed with glass and solidified before being placed in robust heat-resistant stainless steel canisters that are 130 cm high, 40 cm in diameter and weigh 500 kg each.

A full canister emits about 1,500 sieverts per hour — an extremely lethal biological level — and has a surface temperature in excess of 200 degrees.

Its radioactivity starts at 20,000 trillion becquerels. It will take about 1,000 years to fall to one-thousandth of that level, and tens of thousands of years to weaken to the same intensity as natural uranium ore, the Natural Resources and Energy Agency says.

How much high-level waste does Japan have?

Before the Fukushima disaster started in 2011, the nation had been generating atomic power for some five decades, with more than 50 reactors all generating nuclear waste.

According to the Nuclear Waste Management Organization of Japan (NUMO), there were 1,664 canisters in Japan as of December 2009, each capable of holding 500 liters of vitrified high-level waste.

In addition, power plants across the country are keeping vast amounts of fuel in their spent fuel pools — enough to fill 23,100 canisters.

If Japan reactivates and keeps running its 50 commercial reactors, it would generate enough waste to fill 40,000 canisters by 2021, according to NUMO.

What risks does it pose?

High-level waste needs to be stored for tens of thousands years before it reaches a safe radiation level. Critics say no one knows if humankind will be able to manage such dangerous substances in the far-distant future.

At first, spent fuel rods must be kept submerged on-site for several years before their temperatures decline enough to be transported and reprocessed.

But Japan’s fuel reprocessing effort hasn’t even started because its experimental reprocessing plant, in the village of Rokkasho, Aomori Prefecture, has been plagued by trouble.

This means power plants must leave thousands of spent fuel assemblies in the storage pools, where they are vulnerable to natural disasters like those that wrecked the Fukushima No. 1 plant.

At the time of the crisis, the plant had 4,546 spent fuel assemblies in pools, including 1,331 in the spent fuel pool of reactor 4, which was exposed to the atmosphere by a hydrogen blast.

When the cooling systems for those pools were knocked out by the quake and tsunami, the crisis fueled fears that the pools might dry up, exposing the rods and releasing vast amounts of catastrophic fallout that could force Tokyo to evacuate.

How much spent fuel is in the power plants?

According to the Natural Resources and Energy Agency, some 14,000 tons of spent fuel is stored in pools and dry cask facilities at 15 plants nationwide, not counting Fukushima’s No. 1 and No. 2 plants.

The 15 have a total storage capacity of only 20,000 tons, and some have almost run out of space. For example, the Kashiwazaki-Kariwa complex in Niigata Prefecture, the Genkai plant in Saga and the Tsuruga plant in Fukui will all be full in three years if they are restarted.

The government plans to create permanent underground repository for high-level waste somewhere in stable bedrock so the canisters can be stored for tens of thousands of years.

But before that, they must spend 30 to 50 years cooling down at an intermediate storage facility in Rokkasho.

Where does the government plan to build the repositories and is there any way to guarantee their long-term safety?

The government has yet to find a community willing to host such dangerous depositories. It claims certain bedrock locations in seismically active Japan will be stable enough to last a millennium.

The government claims it can find a place devoid of earthquake threats but experts and activists, including Koizumi, disagree. No one can guarantee the canisters’ safety for 10,000 years, they say.

The weekly FYI appears Tuesdays. Readers are encouraged to send ideas, questions and opinions to hodobu@japantimes.co.jp .

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