Nuclear power production is inherently a very clean power, after extraction from the earth of the raw materials then onto the setup of the enrichment processes to extract the nuclides for use in the very complex power stations, the lessening of our dwindling supplies and the reduced reliance on fossil fuel use is exponential and that is a good thing for us and our planet.
Fossil fuels have been with us since the dinosaurs, it is age-old ground down bits of them and early crustations squished into oil from motion with the movements and actions of the tectonic plates, there are seven large scale plates with a number of smaller plates underneath the earths lithosphere and this process, with the ending of the cretinous period as a result from an asteroid hit some 66 million years ago – the start of the movement of the tectonic plates started between 3.3 to 3.5 billion years ago.
So all this dinosaur juice and other organisms including trees, organic and organic compounds, metals, nitrogen, sulphur and oxygen can be found in crude oil. Coal is a result of plants and trees including algae that died long ago to sink to the bottom of lakes and now results as the burnable carbon we know of today.
Crude oil has many uses including the running of ocean going liners, aeroplanes, motor land-based motor vehicles and the end resulting which is a waste product being plastic production, there are different refining processes for these depending on the product required.
Drilling very deep wells in the ocean floor to inject chemicals to extract the oil and digging huge open pits in the ground the world over are not good for the environment or at times the locals, occasional leaks happen (of crude oil) that are devastating to wildlife and can have a lasting effect with generation of sea and bird life habitats and mating rituals.
Nuclear power has a long history of mishaps from ‘The Radioactive boy scout’ attempting to build a reactor in his shed from spare smoke alarm components (Amaricium material), whilst he never built a reactor, he did build a polluting neutron source. X-ray machines have been stolen and scrapped for the contents to pollute a wide area, these are all external to the power plants control but many containment accidents have happened at them including Three mile Island (1979), Tchernobyl (1986) and Fukushima (2011) to name but a few.
The difference between crude oil leaking into the ocean or substrate is very messy and hard to clear up with lasting effects but with a nuclear fuel, cooling liquid or fire is that the resulting contamination can last for a very very long time, the half-life of Plutonium 239 (Pu-239) is 24,100 years, this is the time it takes to for the disintegration (decay) from the fuel to get to a half level it was at before, Plutonium is a man made substance unlike Uranium that is present in nature, we have some resistance to natural Uranium but none to Plutonium in whatever state.
When nuclear power plants fail it could be for a number of reasons but factors include loss-of-pressure-control, loss-of-coolant-accidents, thermal runaways and power excursions, or in reactors without a pressure vessel, reactor core fires either in individual control rods or with a larger number of them – most problems to do with reactors are due to a loss in the cooling system, either the pumps failing and subsequent backup systems not coming online in time or failing entirely as with the Japanese Tsunami that flooded the backup cooling generators at Fukushima.
Most reactors that are online are Pressurized Water Reactors (PWR), they constitute a large number of the worlds nuclear reactor plants aside from those in Japan and Canada that mainly use Boiling Water Reactors (BWR) with core component technology from the 1960s.
Whatever the type of reactor (and there are many more types) if a containment leak happens due to a cooling system failure, many outcomes can occur including immediate fatalities and long-lasting environmental pollution, cognitive defects and widespread cancers. Even though the power plants are safe, and have several backup systems, when an accident happens (with a subsequent containment leak) it has bad consequences*
*Varying accidents will have different fallout dependent on nuclear fuel type, type of accident and whether the fuel is dispersed in a liquid form, airborne or as a wider scale contaminant affecting the mass foodchain/water sources over a longer period of time.
Advances in nuclear fission including the recovery of spent fuel rod material have reduced dangerous waste and the handling of such materials to a level where accidents are unlikely but still possible.
There are options for safer nuclear fuel handling and containment in the form of Thorium (salt) reactors, the fuel does not initially need enriching, the reaction can be easily stopped and there is an added safety (and control) advantage with the operation does not need to take place under extreme pressures.
There are risks with studies suggesting animals drinking massive amounts of Thorium can cause death from metal poisoning, large amounts in the local environment could result in exposure to more hazardous radioactive decay elements such as radon and thoron, which is an isotope of radon but when in a controlled environment, the risks when compared to conventional nuclear power production are less so.
Thorium salt reactors work by the fuel salt being circulated through a heat exchange, it is then cooled by another molten salt loop that is free of radioactive fission and fuel products. The heat from the second loop is then used to do useful work such as heating water to produce steam to turn a turbine and generate electricity.
Advances toward Thorium reactors have been stalled as although the Th-232 fuel is not fissile and as such is not directly usable in a thermal neutron reactor, it is however very “fertile” and will transmute to Uranium-333 easily which is an ideal fissile fuel material.
Thorium fuel molten reactors have many safety advances over conventional tech, they have a negative temperature coefficient of reactivity to achieve active-passive inherent thereby natually lessening the risk against excursions of reactivity.
This is tied to an effect, the so called Doppler effect, if the reaction overheats, fewer neutrons continue the chain reaction, thereby reducing power. Heating of the graphite moderator that usually contributes to a positive temperature coefficient, no heat, no reaction. There is also a factor of the thermal expansion of the fuel – if the fuel overheats it will ‘push’ fuel out of the active core region into a capture tank.
The fuel is stable and coolant too, molten fluorides are chemically stable and do not burn or explode as well as being impervious to excursions of radioactivity with that the systems are run at a far lower pressure and easier to control.
So if these reactors are so great, why are there not more of them?
The systems don’t make much spare fuel – every nuclear reactor creates other elements due to fission reactions, by-products and purposeful enrichment processes including Uranium for bombs. Thorium reactors produce very little with at most 9% more fuel than it burns each year, the next step is to design a reactor that only uses 1% fuel per year reducing costs and associated risks even more, this lessens the creation of bomb making material and most think this is the reason Thorium reactors are not the de-facto choice for the human race.