Exactly one year ago, March 11 in 2011, Japan was hit by a devastating earthquake with a magnitude of 9.0 on the Richter scale. Following the earthquake, a violent tsunami struck the northeast coast of Japan, where Fukushima is located. The natural disaster claimed 20,000 lives, as well as several meltdowns at the Fukushima Daiichi nuclear power plants, which lead to release of nuclear radiation.
A recent poll reveals that the people of Japan are starting to rethink nuclear energy: Almost 70% wants to stop or reduce the use of nuclear energy. What are the chances of an accident like this happening again? Is harnessing nuclear energy really worth the risks?
No Guarantees for Safety
The Fukushima Daiichi accident is the largest nuclear disaster since Chernobyl that took place in Soviet almost three decades ago, resulting in over 4000 civilian casualties according to the World Health Organization (WHO). A Russian publication, Chernobyl: Consequences of the Catastrophe for People and the Environment, claims that the aftermath of the nuclear radiation is responsible for almost 1 million pre-mature deaths.
The extent to the nuclear accident in Japan is of course not as devastating as it was in Chernobyl. However, it does make one ponder about how safe nuclear power really is.
The nuclear reactors showed to be robust seismically; the safety systems did not work, as they should’ve when the 50 feet tsunami struck them. Although the technology behind the safety systems in the nuclear facilities has had radical improvements since Chernobyl, there are ultimately no guarantees and there never will. Nuclear processes are inherently unstable and the amounts of energy released in them, nuclear radiation and waste should not be taken lightly.
What About Thorium?
In the last decade, and especially after the nuclear accident in Japan, the interest in using thorium to power the fission processes in a nuclear reactors has grown tremendously.
Thorium possesses several noteworthy advantages:
- The reserves of thorium have been estimated to be four times as large as those of uranium.
- The waste generated compared to uranium is reduced by a factor of several hundreds.
- The energy density of thorium is astonishing. The average lifetime consumption of energy is equivalent to a ball of thorium, small enough to fit in your palm.
- Looking to the future, massive reserves of thorium can also be found on the moon. The natural element’s electro-magnetic signature makes it easy to locate on other plants from the Earth.
While the benefits mentioned above are very important, it is probably the fundamentally different safety system that is associated with thorium power plants that is the most impressive:
The father of conventional nuclear power plants that uses uranium as fuel, Alvin Weinberg, also lead the research of thorium powered nuclear plants, which possessed far less safety issues.
Uranium reactors use water as the basic coolant has some benefits, but also a lot of problems. The water needs to be at very high temperatures for electricity to be generated efficiently. This requires pressures that are 70-150 times the atmospheric pressure to prevent vaporization. There is no way getting around this. Accidents where there’s a pressure loss inside a reactor, resulting in rapid vaporization of water (steam), can be disastrous. If somehow the safety mechanisms designed to cool down the reactor fails, a meltdown happens and its surroundings are exposed to dangerous radioactivity.
A thorium-powered power plant does not have these problems because of a very simple reason: It is not based on water-cooling. Instead, it uses a molten salt mixture, which are remarkably chemically stable. This enables the facility to operate at much lower pressures than a uranium-powered reactor, thus eliminating the problems with water-cooled reactors mentioned above.
It is speculated that the development of uranium power plants were at least partially motivated by the fact that the same underlying technology is the foundation of nuclear weapons.
It is comforting to see that the interest has moved away from uranium reactors and towards Weinberg’s alternative designs, as well as other fundamentally different approaches to harnessing nuclear energy.
A thorium power plant would use a mechanism called a freeze plug, a piece of frozen salt that is kept frozen by cool gas. An emergency would trigger the cool gas to stop flowing; the freeze plug would melt, ensuring that the liquid fuel inside the reactor ends up in a drain tank where it can safely be dealt with.
This is a fundamentally different approach to safety than what is used in today’s uranium-fueled power plants, where we have to provide power for safety measures to commence. In comparison, with a liquid fluoride thorium reactor, it is the absence of power that triggers appropriate safety procedures, even without human intervention.
The Fukushima Daiichi Aftermath
Three workers where killed at the Fukushima Daiichi nuclear power plants as a result of the earthquake and tsunami. There have been no fatalities from nuclear radiation. As a side note, it is strange to see how the media put emphasis on the event being a “nuclear” disaster.
On the other hand, the long-term problems associated with the nuclear radiation are not well known yet. Renowned physicist Michio Kaku estimates the cleanup to take somewhere between 50-100 years, and thinks the event will become the worst industrial accident in the history, topping Chernobyl at $200 billion.
The Tohoku earthquake and the following meltdowns at the Fukushima Daiichi reactors can teach us one important lesson: As long as we harness nuclear energy, we can never protect ourselves completely from nuclear accidents. That does not mean that safety can’t be improved and the risks involved can’t be reduced. Further developing thorium power plants is a step in the right direction.