BURYING NUCLEAR WASTE
High and low-level waste are stored in very different ways
1 MAKING HIGHLEVEL WASTE
Radioactive uranium gradually decays so that it doesn’t drive enough of a chain reaction, but it’s still dangerous and hot.
2 MOVING IT TO A DIFFERENT POOL
Cranes move the uranium to a waterfilled pool to cool down for five to ten years.
3 STORING IT SECURELY
The cooled uranium is secured in a steel container. It might be mixed with molten glass, and is also sometimes encased in concrete.
4 FINDING IT A HOME
Usually secured uranium has to travel to a storage site. Many countries don’t yet have long-term storage for high-level waste.
5 THE WASTE GOES DEEP
Properly stored highlevel waste should be buried up to 1,000 metres underground.
within hours. There are many radioactive substances in nature which in small amounts are safe, but in higher amounts they can be dangerous. The radiation that radioactive uranium releases can kill our cells by damaging our genetic material, or DNA.
Cranes, rather than people, usually handle radioactive materials straight from nuclear reactors. They pull spent fuel rods out of the reactor, keeping them under water or in another shielding liquid. They’re usually kept in storage pools for a few years, with the water being kept topped up as the heat from the rods boils it off.
The world has more than 250,000 tonnes of high-level nuclear waste (HLW) that needs to be stored, with over 90,000 tonnes in the US. We add around 12,000 tonnes to this each year. Uranium-235 in waste fuel rods makes them dangerous – and useful. Some facilities reprocess the waste, removing remaining uranium-235 to put in new fuel rods. Yet even this process leaves some HLW behind. Usually all nuclear waste ends up in steel containers and buried underground. When stored, the danger from the waste initially falls quickly. The heat and radioactivity it releases when it leaves a reactor is about 100 times higher than what it will be after 50 years. However, it still takes HLW a long time to become truly safe. The Onkalo spent nuclear fuel repository is planning for it to take 100,000 years. For comparison, the oldest pyramid is just 4,600 years old. It’s one of many ways that nuclear power has changed how we think.