Science Facts

What Happens To Nuclear Waste? – Disposal System

Nuclear Waste

Today there are nearly 450 nuclear reactors around the world. In the UK, 15 nuclear reactors provide around 20 percent of the country’s energy needs. In the USA, 99 reactors account for 30% of the world’s nuclear energy generation. Power plants were commissioned, and electricity was pumped out with apparently little in the way of a long-term plan.

While uranium might not pump out any nasty gases as fossil fuels do. It does leave behind a lasting legacy in the form of high-level radioactive nuclear waste. That same radioactivity that hits the water in a nuclear reactor tends to linger once that fuel is discarded. However, international conventions don’t allow the disposal of any waste in global oceans. And the thing about subduction zones is that what goes down tends to come back up.

What happens to nuclear waste?

Nuclear plants are processing powerful radioactive energy that needs to be disposed of correctly to keep the environment and the people handling it safely. Modern nuclear plants keep waste to a minimum by recycling used fuel back into uranium-based and mixed-oxide fuel. But four percent of nuclear waste can’t be processed and remains highly radioactive. As a result, radioactivity is a waiting game, as the toxic quality of the waste decreases over time. It is measured in half-life or the time it takes for a radioactive substance to reduce to half of its nuclear value. The time it takes for nuclear waste to neutralize varies wildly.

Some common isotopes like Strontium-90 have a half-life of around thirty years. But other powerful artificial nuclear isotopes like Plutonium-239 have a half-life of over twenty thousand years. So not only is it radioactive enough to kill anyone exposed to it, but it could be an unpleasant surprise for whoever digs it up in the far future.

Nuclear power plants operate in thirty-one countries, including all of the world’s largest economies, and much of Asia and Africa are planning new builds. The regulation of nuclear waste is overseen by the International Atomic Energy Agency’s joint convention on spent fuel management, and they work to keep the world safe.

  • The risks of exposure to nuclear waste include a higher risk of cancer, a higher risk of birth defects in pregnant women, high concentrations, organ failure, and death.
  • Most nuclear waste comes from nuclear power plants and nuclear arms, but medical and industrial waste and natural radioactive materials also pose a risk.

Nuclear waste comes from two primary sources: the front-end and the back-end.

Front-end nuclear waste: It comes from the extraction of uranium and contains radium. The depleted uranium that comes from it is extremely dense and is often recycled into anti-tank shells and other metals where extreme durability is needed.

Back-end nuclear waste: It comes from spent fuel rods and is packed with beta and gamma radiation. These powerful energies come with extremely long half-lives and are formed in nuclear reactors.

Some of the most challenging waste to dispose of comes from nuclear weapons materials. And the plutonium used to create these powerful bombs is extremely difficult to separate and isolate. That makes nuclear weapon disposal a growing concern. The world is less likely to end now, but what are we going to do with all those things that can end the world?

The classification of nuclear waste determines the priority level of processing and disposal. About 90 percent of the nuclear waste we produce every year is low-level waste, clothing and tools, and whatnot. Out of the remaining ten percent, seven are intermediate-level leftover reactor components, and three percent are high-level waste.

Low-level nuclear waste

The lowest-priority nuclear waste is uranium mill tailings, created by the rough processing of uranium ore. In contrast, they don’t contain a high level of radioactivity. They have long half-lives and are full of metals with other health risks like arsenic and lead.

Low-level waste is the most common waste type because it’s anything that came into contact with radioactivity. Common in hospitals and processing plants, it can include paper, clothing, tools, and filters used by people working with nuclear energy. These objects pick up trace levels of radioactivity. And these should be disposed of safely instead of being processed with standard trash.

Intermediate waste is usually the by-product of nuclear processing and is harder to dispose of than low-level waste. Resins, chemical sludge, and metal coverings exposed to nuclear energy long-term pick up the harmful radioactivity. And the hazardous nature builds over time. For example, when breaking down a nuclear reactor for decommissioning, even the building materials surrounding the core can build up radioactivity.

Before disposing of this waste, it should be safely shielded to prevent exposure. Then there’s high-level waste, and this is what everyone thinks about when they hear about nuclear power plants. The alarms start blaring. The hazmat suits go on.

Intermediate level waste

Intermediate-level waste includes higher contaminated filters, rags, medical tools, steel, reactor components, and many other items. Finally, there’s waste incidental to reprocessing. It refers to waste by-products that result from reprocessing spent nuclear fuel more on that in a bit. Uranium mill tailings are the residues remaining after the processing of natural ore to extract uranium and thorium.

High-level nuclear waste

High-level nuclear waste is as radioactive as you think, but the good news is there is an effective waste to contain it. When a nuclear fuel rod serves its purpose and is taken out of the core, it becomes high-level waste. In comparison, the number of high-level waste objects is small compared to the other classes. The level of radioactivity is so high. It accounts for over 95% of total radioactivity caused by nuclear energy.

While most radioactive isotopes produced by high-level waste are high-powered but have a short half-life. The presence of isotopes like plutonium makes it critical to ensure it’s contained safely.

Disposal nuclear waste

What’s the best way to dispose of nuclear waste? That’s what nuclear-energy-using countries have been arguing over for decades. Most experts say the best solution for long-term disposal is by constructing a deep underground facility. That can contain large amounts of high-level waste away from humans and be sealed up in between disposals. But that’s easier said than done, and no country has finished one. Although Finland is close to completing their Onkalo spent nuclear fuel repository on their west coast.

Before disposal of nuclear waste, some major process must have to follow:

First, the site needs to be selected. The ideal location is geologically stable, far away from faults that rupture and cause earthquakes if drilled.

The packaging of the waste is also important. To ensure it stays where it’s, Patna spent fuel is first encased in insoluble resin and then placed into thick steel containers. Several of these containers are put inside steel or a copper sarcophagus. It is then surrounded by buffer materials specifically designed to absorb the radiation. The fuels final resting places in deep underground bunkers could then be backfilled with concrete to prevent any later disturbance.

Engineers have come up with an ingenious solution with ”hydraulic cage”. It works by surrounding the waste containing chambers with a layer of gravel. Any water that finds its way through the rock will find it easier to flow through the gravel around the chamber rather than flow through it. That keeps the nuclear waste nice and dry inside.

Bit by bit, scientists and engineers are overcoming the challenges facing the nuclear disposal problem. There are also two popular methods for disposing of nuclear waste:

Vitrification: High-level radioactive waste is mixed with silica sand and other glass-forming chemicals. That mixture is heated to temperatures up to 2100 degrees Fahrenheit until it melts. Then the molten material is poured into stainless steel containers where it cools and forms a glass. It’s still radioactive, but it’s small, doesn’t leak, and easier to store.

Nuclear tube: A small island off Finland’s Westcote has plans to begin storing 5,500 tons of nuclear waste nearly a mile below the earth. This new tube will take over a hundred years to complete at the cost of 5.3 billion dollars. Once it’s done, the repository will be filled with nuclear waste and sealed off for the next hundred thousand years.

The only problem is that man has never created anything that’s lasted longer than seven thousand years. So this nuclear tube is an effective solution, but it is promising.

Currently, countries use many alternative systems that are considered safe but imperfect. The first step to minimize the impact of nuclear waste on the environment is to neutralize it as much as possible. This is done by processing it and stabilizing it into a form that loses its explosive properties. For example, some countries mix the waste with sugar and then calcinate it into a solid object by processing it through a rotating tube.

Turned into the glass, the waste products are bonded to the other molecules and then poured into stainless steel and sealed. They’re then stories underground, where the waste products are trapped for thousands of years without leaking radioactivity into the environment.

Other technologies include ion exchange, where medium-level wastes are neutralized by concentrating the radioactivity into a much smaller volume. It makes them easier to contain but isn’t recommended with the volatile high-level wastes. When the time range for nuclear waste to become deactivated can reach millennia or longer. Scientists are concerned that these storage methods could come back to haunt us. That’s why we’ve eliminated many of the more short-sighted nuclear waste disposal methods, like ocean disposal.

The Arctic ocean was a popular choice for the Soviets, as they controlled a huge coast in the north. Overall, 137,000 tons were dumped in the water by European countries in thirty-four years, and it took its toll on the oceans. Moreover, tests of areas where dumping was common found elevated levels of radioactivity. As a result, in 1993, a treaty was passed banning ocean disposal of nuclear waste.

The most common current method for nuclear waste disposal is above-ground disposal. First, the waste is sealed up in a steel cylinder with an inert gas that won’t react and seal in radiation-shielding concrete. The radiation-proof drums are then sealed in a storage facility near the nuclear power plant. This is how big plants handle their waste in-house, and it’s popular for a few reasons.

  • First, it’s handled internally, and the plant doesn’t have to get approval and fight its way through government red tape to find a dumping facility.
  • Second, it’s inexpensive and doesn’t require construction or expensive materials.
  • Finally, the waste remains on-site for reprocessing, which remains the best solution for solving the nuclear waste question.

The secret weapon for eliminating nuclear weapons is chemists and physicists. These scientists have developed ways to chemically separate fission products and unused uranium from used nuclear fuel. This started by extracting Plutonium, with its long half-life, from nuclear fuel to construct nuclear weapons. But as the focus shifted from bombs to energy plants, scientists developed ways to create a new type of nuclear fuel from the remnants of the old.

MOX nuclear fuel, or mixed oxide fuel, is created in high-level facilities from nuclear waste plants around the country. It has become a top way of disposing of nuclear waste in Europe.

The government is focusing on research in America, and commercial nuclear fuel reprocessing isn’t widespread yet.

Future nuclear waste disposal system

What will nuclear waste disposal look like in the future? One of the biggest possibilities is space disposal, as this will get the radioactivity as far away from people as possible. The problem is that technology isn’t there yet. While technology like mass drivers and space elevators is in development, the carrying capacity of current space shuttles is limited. And it would only be able to carry a small amount of nuclear waste.

The money that goes into every space shuttle launch is high, and the program is far from fool-proof. The loss of the Challenger and the Columbia shuttles proves that a catastrophic accident is possible. And a space shuttle disaster carrying a nuclear payload could contaminate a large area. Could we transform nuclear waste into less harmful waste with a shorter half-life?

That was the dream of the scientists behind the Integral Fast Reactor. An experimental reactor that would use a nuclear fuel cycle that reprocessed fuel through electrorefining. It would extract almost all the energy contained in uranium, cutting fuel requirements by two orders of magnitude. Unfortunately, the design had problems with leaking cooling fluid, and the US Government canceled the project in 1986. But research is ongoing, and new fission reactors with much more processing power than traditional light water reactors are under development.

The earth itself might be our best ally for disposing of nuclear waste, as artificial structures underground are the top proposal for future storage facilities. By digging out large, stable bunkers in sparsely populated areas of a country, nations could keep their nuclear waste in a centralized location and reduce the risk of leaks happening in multiple locations.

Deep borehole disposal is an alternative. That creates narrower but much deeper holes capable of storing the waste up to three miles under the Earth, where any leaks would be far away from humans. Besides developing the technology for safe deep-earth drilling, getting approval from governments is a holdup. Many countries have rejected proposals out of fear that the disposal won’t be safe or destabilize the ground. The consequences of a nuclear accident are massive and long-term, as the residents of Pripyat, Ukraine, know all too well.

In the heart of the Chernobyl nuclear plant is the Elephant’s Foot, a mass of solid nuclear waste caused by the 1986 meltdown. Dense and hard to damage, it was so radioactive when released. Today, over thirty years later, it’s still highly radioactive and poses major health risks to exposed people.


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Sources:

“The Geological Society of London – Geological Disposal of Radioactive Waste”.
“Recycling used nuclear fuel – Orano la Hague”.
Attix, Frank, Introduction to Radiological Physics and Radiation Dosimetry.
Gofman, John W, Radiation and human health.
Cochran, Robert, The Nuclear Fuel Cycle: Analysis and Management.

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