Finding suitable sustainable alternatives to fossil fuels has become one of the most pressing questions of our time. While renewable sources of energy are usually put forward as the only responsible solution, their ability to provide the capacities required remains a point of contention. Research confirms that...
What has become known to us about this technology up till now is ample reason to press on and take the next steps in investigating the MSR.
Finding suitable sustainable alternatives to fossil fuels has become one of the most pressing questions of our time. While renewable sources of energy are usually put forward as the only responsible solution, their ability to provide the capacities required remains a point of contention. Research confirms that the thorium fuelled Molten Salt Reactor shows remarkable performance in terms of safety, environmental, and economic aspects, and leans more towards offshore wind power than towards conventional nuclear power regarding these. A technology that promises large scale, low carbon, and arguably sustainable energy generation that is capable of solving some of the greatest energy problems of our time is within our reach. Now let us grasp it.
Whether one contends that renewables will overcome current shortcomings or not, the only conclusion the rational observer can draw with absolute certainty, is that we simply cannot be sure at this juncture. The question then becomes: if we are uncertain about the successful outcome of these efforts, is it sensible to put all of our eggs in one basket? What if we gamble, and lose?
Surely the prudent course of action would be to have a feasible contingency plan on hand, in case the renewable option does not perform as advertised.
Nuclear power could provide an adequate solution but suffers heavy opposition, which is why an innovative nuclear technology may offer a more than satisfactory option. We shall discuss both below.
Nuclear energy challenges
Although nuclear energy has the advantages of large scale, low carbon energy generation, it is controversial because of the perceived adverse characteristics associated with it. These are real concerns, and potent arguments against nuclear power being considered a sustainable energy candidate. According to the literature most important among these are:
1. reactor safety, i.e. prevention of accidents and Fukushima/Chernobyl type disasters,
2. safe long-term storage of nuclear waste,
3. potential for nuclear weapons proliferation,
4. the relatively high costs of nuclear power generation
If these are the reasons nuclear power is not perceived to be sustainable, what happens if they are dramatically decreased, or even completely removed?
The Molten Salt Reactor (MSR)The Molten Salt Reactor (MSR) reactor design has enjoyed a rapid increase in interest in recent years that shows no signs of slowing down. It departs radically from the traditional assumptions of what a nuclear reactor should be, which gives it several significant advantages and completely avoids some of the key problems associated with conventional reactor designs, simply because it is a fundamentally different piece of machinery.
Coupling the MSR with the thorium fuel cycle further enhances it performance. The thorium-MSR (TMSR) is believed to be the MSR in its optimal configuration as well as the ideal way of utilizing thorium as a nuclear fuel.
Challenge 1: Reactor safety
The defining characteristic of the MSR is that its fuel is in a liquid state, instead of a solid as is common in conventional reactors.
Because the fuel is not in a solid state, the danger of meltdown is removed. Meltdown occurs when the solid uranium fuel rods overheat to such an extent that the material melts, which can have dire consequences if the material then escapes its containment. In the MSR the fuel is expected to be in a liquid state and the structure is engineered to safely accommodate this.
If the fuel's temperature does increase, the reactor relies on several passive safety systems, meaning that instead of requiring continuous external manipulation to keep temperatures at safe levels, the reactor will automatically restore safety without any outside intervention. In the off-chance the liquid fuel were to escape its containment it rapidly cools and hardens, trapping dangerous fission products inside.
What's more, the liquid containing the fuel doubles as the reactor's coolant. Contrary to the coolant in most conventional reactors, water, the MSR is cooled by a mixture of molten salts that can reach much higher temperatures without turning into steam. This obviates the need to keep the coolant under high pressure to increase its capacity to take on heat, thus eliminating the major danger of pressure explosion.
The 2011 Fukushima Daiichi disaster has negatively influenced the perception of nuclear power. Source: People’s Daily Online
Challenge 2: Nuclear waste
Nuclear waste production will be drastically reduced in the TMSR. Total volume is expected to be 35 times less than is common in conventional reactors to produce the same amount of energy, and of what remains 99.99% is stable within 300 years, instead of the dreaded tens of thousands of years for conventional nuclear waste. In addition, MSRs can also burn existing nuclear waste, thus contributing to solving the existing waste problem.
Important reasons for the MSR's reduced waste profile are that it utilizes all of its fuel instead of the 3-5% common in conventional reactors, and it has a higher thermal to electrical conversion rate. Fission products that are formed can simply remain in the liquid fuel and be burned up, or removed if they are undesirable (e.g xenon gas).
Challenge 3: Nuclear weapons proliferation
The potential for nuclear weapons proliferation is strongly reduced in the MSR due to its physical unsuitability for weapons production. Although theoretically possible, the reactor is believed to be a poor means to this end. A party would have to be in control of the reactor and such an entity would have a much easier time generating plutonium or enriching natural uranium using different means.
A key reason for the TMSR’s proliferation resistance is that the thorium decay chain produces uranium-233, which is always accompanied by uranium-232. Uranium-232 is almost inseparable from uranium-233 and produces strong gamma radiation that is highly destructive to ordnance components, circuitry, and personnel, making it highly impractical to handle.
There is reason to believe TMSR electricity will be significantly less expensive than electricity from current nuclear technology. Factors contributing to a lower cost profile are simplified construction including the absence of expensive safety systems, modular construction, simplified fuel handling, higher energy efficiency, and the potential for additional processes made possible by the MSR’s high operating temperature, among others. Additional construction relating to components unique to the MSR such as the fuel salt processing system have to be accounted for as well however.
Finally, adding to thorium fuel’s sustainable performance is that there is plenty of it. Reserves are estimated to be sufficient to satisfy the entire world's energy needs for tens of thousands of years.
A closer look: Environmental Impact Assessment (EIA)
To go beyond the basic theory and come to a deeper understanding of what can be expected of the TMSR's environmental performance, its “environmental impacts” were evaluated using the widely accepted Environmental Impact Assessment (EIA) standards. Information to populate the assessment was sourced from existing literature on the subject complemented with input from experts in this field. In addition to classic environmental features like contamination of air, water, and soil, nuclear power's top 4 perceived adverse aspects were included.
The TMSR's environmental impacts were then compared to those of the Pressurised Water Reactor (PWR), the most common reactor type in operation, as well as offshore wind power as a benchmark of true sustainable energy generation by assigning points to environmental impact performance. Although it was clear that the former would lend itself better to comparison than the latter, enough common ground could be found to make a meaningful comparison. Where this was not possible because wind simply does not possess a particular characteristic, it received a perfect score of 0 points. In case of any doubt about the assigning of relative importance to particular characteristics, wind was given the benefit of the doubt to avoid painting too rosy a picture of the nuclear options.
The encouraging outcome was that the TMSR performed surprisingly well under the pressure of these strict environmental criteria. While wind power showed to be the most environmentally sustainable option as expected, with 32 environmental impact points, MSR technology leans more towards offshore wind power in the environmental impact spectrum with 73 impact points than it does towards conventional nuclear power, which was responsible for 126 points.
Environmental impacts evaluation results for traditional nuclear, wind and TMSR.