The conventional nuclear reactor generates power by nuclear fission of radio active elements such as Uranium, Plutonium, etc, As we know, these elements have very long half life time and hence the radiation and its impact are highly dangerous.
There are many other radio active elements which are less harmful to environment. Even though these elements may yield less power compared to conventional radio active materials for power generation, the alternative elements may be used to power small townships, hence reducing nuclear radiation risks and lower gaseous emissions from thermal power plants.
The whole concept of nuclear power generation may be decentralized in a safer manner at low risk.
1. Thorium is a radioactive element that could be used to generate low-carbon electricity. Compared to the uranium that is used in today's nuclear plants, thorium is more abundant and widely distributed in the Earth's crust. It also offers various safety benefits over uranium: it's not susceptible to generate chain reactions that can lead to nuclear disasters. Its waste products remain dangerous for a much shorter period, and its byproducts aren't useful for making nuclear weapons. In addition, thorium reactors could theoretically be used to burn up the dangerous plutonium stored in existing nuclear waste stockpiles.
There are different ways that thorium can be used to generate energy:
- solid thorium fuel used in water-cooled reactors;
- liquid fluoride thorium reactor (LFTR);
- the use thorium in sub-critical accelerator-driven reactors.
2. According to paper: Sustainable Minireactors: A Framework for Decentralized Nuclear Energy Systems by A. A. Harms and W. W. Sassin, there is a need for small power sources serving localized and special energy requirements consisting of small minireactors in the 1-10 MW capacity range. These minireactors would therefore need to operate safely with high reliability and, as we emphasize here, be assured of a sustainable supply of easily transportable fuel. A central nuclear "parent" facility is envisaged for this purpose.
https://link.springer.com/chapter/10.1007/978-3-642-81988-9_5
In the coming decades, the use of the so-called "Small Modular Reactors or SMR" for electricity generation and desalination will be the most convenient solution for continuing the use of nuclear energy for this specific purposes. Other types of reactors are the so-called "Generation IV" reactor and fusion reactors.
The conundrum is how to generate electricity at a sensible long-run economic cost. The recent completion of the reactor in Abu Dhabi is believed to have a levelised cost very significantly lower than £60/MWh. Smaller reactors suffer from a large fixed cost which is partly why the Westinghouse AP1000 was scaled up from the AP600. The Energy Technology Institute report of late 2015 has SMRs' levelised costs around £100/MWh. For SMRs to be cost effective, a different approach to design is needed where the extremely well known and understood nuclear physics is not treated as the primary topic but how to build, operate and maintain the devices as efficiently and economically as possible subject always to the approach of the safety regulator. All this has to be considered together with both the death rate of different forms of generation - see http://bit.ly/2utrKRR) and the late David MacKay's observation in his wonderful book (see http://withouthotair.com) that if all the energy used in a person's life came from nuclear generated electricity, all the high level waste would fit in a Coke can. As for alternative elements, any element larger than Iron can in principle (binding energy per nucleon) be split to release energy and lower Z ones could be fused to release energy. However, what really matters is the whole-life cost of the choices, not the element itself. For example, the use of Uranium in conventional reactors followed by further use in fast reactors can create the ultimate waste with much shorter half-lives. It is possible, if this closed fuel cycle approach were to be used, that the ultimate waste would have short enough half lives that in 500-ish years time the waste would have about the same sort of radioactivity as the original ores from which it came. The Chinese, Russians and Indians are working on this approach (amongst others). What's needed is a pragmatic approach based on long-run costs and consequences, not nuclear engineers who need to be servants to the project with regulatory oversight. The South Korean success is the result of creating a good design once and building the same thing over and over again and driving efficiency in construction and fleet management, maintenance and operation. The UK (by example) has a large collection of one-of-a-kind devices - while the fleet of advanced gas cooled reactors at the heart of the current nuclear generation fleet were intended to be a single design, different construction teams over years modified the designs - out of good intentions - but the fleet learning was badly damaged as a result. With pressurised water reactors operating at a thermodynamic limit of around 35% efficiency (which given the tiny cost of the fuel is a very small economic issue), the greatest gains come not from tweaking designs for efficiency but increasing capacity factors to as close to 100% as practically possible, by designing for ease of maintenance (and thus driving up capacity factors) and by designing for ease of manufacture to keep the capital cost down. THe biggest factor, however, is the cost of capital. For large reactors, 1 percentage point change in the Weighted Average Cost of Capital creates a variation of around £13/MWh in the electricity cost. Equally, a £!bn change in the capital cost creates a variation of around £8/MWh. Driving down the cost of capital through smarter sources of capital and lower inherent construction and operation risk is the biggest challenge.
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