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Nuclear Fusion: Future or Fallacy?

With the energy crisis nearing, if not already upon us, there emerges a need for energy sources that give more than they take. Many debate about the means of energy production, with arguments favoring wind energy, solar energy, and energy through hydropower. They each also have their drawbacks, with particular criticism being made of Nuclear fission power by Green Parties in various countries. The main reason cited is that the nuclear waste produced has lethal effects for the environment and is a solution to the energy crisis with a lot of strings attached to it.

While there continue to be many sides to the debate, this blog is not focused on the the benefits and drawbacks of nuclear fission. This blog discusses a relatively lesser talked about (for obvious reasons) source of clean energy: Nuclear Fusion. I will present to you the bare bones that there is to know about Nuclear Fusion. What it is, method of energy production, viability, related technology, and the pros and cons. It is then unto you to reflect and to evaluate this method of energy production.

Nuclear Fusion refers to the controlled process where the nuclei of two atoms are smashed together such that they fuse, liberating energy in the process. The reason energy is released can be explained by the concept of binding energy.

We must first recall one of the most famous equations in the world of Physics. Einstein’s relation between mass and energy. E=mc^2. The relation says the mass and energy of a particle are proportional to each other, and indicates that the mass of a particle can be converted to energy and vice versa.

When two or more particles bind together, the overall energy of the system decreases due to finding a stable configuration, and hence the mass of the system decreases. When a nucleus is assembled, with all its nucleons (constituent particles), the sum of the nucleus is less than the sum of the individual masses of the nucleons. This mass difference results in an energy difference, which is called the binding energy. Consequentially, the binding energy is the amount of energy put into a nucleus to separate all of its nucleons into their individual selves.

Energy can not just disappear, it has to go somewhere. Hence, during the creating of a nucleus, the binding energy of the nucleus is liberated.  This makes the creation a nucleus a theoretically viable process for energy production.

Granted, one does not make a nucleus out of thin air, we need the components to make a new nucleus. One way to do it is by using other nuclei. This method is called nuclear fusion. The nuclei of two atoms are brought together, and fused to make a new nucleus with a larger number of nucleons in it. The process releases a lot of energy.

 

The Binding energy per nucleon against nuclear mass

Credit:https://pwg.gsfc.nasa.gov/stargaze/SnucEnerA-2.htm

The above image gives us the binding energy for each nucleon in a given element. The mass number refers to the total number of protons+ neutrons in the nucleus. We notice at this point, that the graph assumes a particular shape. One with a peak, a maximum binding energy. This occurs for the element Iron, which has 56 nucleons.  Now that we know what nuclear fusion is, the question becomes, which two atoms do we fuse to liberate energy?

The curve serves as an indicator. To have energy be liberated, the binding energy of the atoms before fusion must be less than the binding energy of the atom after fusion. Hence, to produce energy via nuclear fusion, one must fuse atoms of a smaller mass number than 56, hence creating an atom with a higher mass number, thus higher binding energy.

Keep in mind that the atoms to be fused need to have a mass number less than 56, so everything to the left of iron fuses, but nothing to the right of iron will produce fusion energy. This is because the binding energy decreases after iron.

Fantastic, this is a method that can produce more energy for a given amount of mass being fused than even nuclear fission (splitting heavy nuclei to the right of Iron to smaller nuclei). Then, why is it not the most used form of energy production? The answer boils down to the net energy liberated.

The nucleus repels itself, due to the presence of protons in it. Hence, to get two nuclei to stick together, one must first overcome this repulsive electrostatic force, and push them all the way close until, at the point of the separation, the attractive ‘strong nuclear force’ is higher than the repulsive electrostatic force. The issue is that poshing repelling nuclei towards each other takes energy, and to achieve the outlined scenario, the fusing energy is larger than the energy liberated, hence resulting in the net energy loss. Even if there is no net energy loss but gain, the gain is so small, that it is of no use for mainstream energy production.

 

One of the main research interests in viable methods for fusion is the TOKAMAK project. It explores the idea of magnetic fusion. To get nuclei to fuse, massive pressure must be put on them. Also, the nuclei can be smashed at very high velocities so that they fuse. This is the principle of magnetic fusion. It is conducted via the means of a high temperature plasma. Plasma is a state of matter where the atoms can exist as separate electrons and nuclei at high temperatures. The higher the temperature, the faster the nuclei in the plasma move, hence more successful high speed reactions result in higher amount of fusion.

 

The TOKAMAK is a donut shaped “cage”, that uses magnetic fields to confine extremely high temperature plasma where nuclear fusion can take place. The advantage a magnetic field offers is that no solid material can contain the plasma at such high temperatures, but a magnetic field can confine the plasma. Hence, the high temperatures can be confined in a magnetic field and then shielded with vacuum, hence creating an insulation. So far, magnetic fusion is one of the most successful methods of nuclear fusion known to man, with other methods not yielding as well. Research continues to be done in the field, with the focus now on the idea of minimizing energy losses, how to achieve even higher temperatures, and extracting the produced energy.

 

Therefore, Nuclear Fusion remains a hot (hah!) bed for research, and the viability as a real source of energy is a question of when, not if.  The advantages nuclear fusion offers is more than any other method of energy production. Some of them include no carbon footprint, abundancy of fuel, and very low level of radioactive waste. With the very small amount of drawbacks, this makes it one of the best energy sources we have available.

Authors: Pratheek Kishore, Octavian Stoicescu, Nicollas S.M. Borges, Abhijith Jyothis P.

Nuclear energy has been suggested as a possible solution for climate change for a while, but how effective is this solution? What are the benefits of nuclear energy that would help with the current climate predicament? The purpose of this blog is to explore nuclear energy as a viable alternative energy source for cleaner emission and how this aids in alleviating climate change. We will consider the current state of the climate, the theory behind nuclear energy, comparison of different energy sources and their risks, and finally the future of nuclear energy (nuclear fusion?). 

We often hear about global warming being a current issue,  what we don’t hear is that this is something that’s been having an impact on our world for quite some time. The total average land and ocean surface temperature increase from 1850 to 2012 is 0.78  ͦ C. Total Glacier mass lost around the world except glaciers present on the periphery of ice sheets from 1971-2009 is 226 Gt per year. The Global Mean Sea Level (GSML) has risen by 0.19 m, as is estimated from a linear trend, from 1901-2010 and permafrost temperatures have increased in most regions worldwide from observations of trends since the early 1980s.Humans have been clearly impacting the climate of the planet for a very long time, but what does this all mean? It’s easy to look at statistics and forget these numbers have real world implications. For example, in some terrestrial systems, “Spring Advancement” can clearly be observed, which is the premature occurrence of spring-related events such as hibernation, breeding, flowering, and migration. Ocean acidification due to climate change decreases calcification which favours the dissolution of calcium carbonate and bioerosion, ultimately yielding coral reefs that are poorly cemented. Rocky shore animal and algae distribution, as well as abundance, has been observed to be altered due to climate change along with a significant decline in mussel bed biodiversity in the Californian coast. The body sizes of several marine species such as the Atlantic cod have been clearly negatively linked to changes in the temperature. The effects of climate change can be observed all around us, from the forests to the oceans, from the desert to the tundra, but perhaps the most relatable and personal effect would be the impact of climate change on humans. Climate change can have varying effects on several ecosystems, which can lead to food security issues globally. Climate extremes might increase the spread and ultimately the likelihood of attaining some diseases and infections. We can observe from studies on heat waves the effect increased heat will have on health, which leads to  increases in cardiovascular and respiratory disease, and generally increased mortality. During 2004-2018, in the United states alone, an average of 702 deaths annually were heat related (287 deaths had heat as a contributing cause, and 415 had heat as an underlying cause). So as you can see, climate change is an issue that has clear and direct effects on our ecosystems, on our environment, and on ourselves. If this matter is not addressed with the utmost of care and research, it may lead to dire consequences for us and our future on this planet. This is why there must be a global effort to utilise trialed and tested solutions to counter this problem. Currently our energy is supplied primarily by fossil fuels, which are not only limited in supply and depleting quickly, but major contributors to climate change through the emission of greenhouse gasses. Following this trajectory is not a viable solution for our future. But what could such a solution be? It turns out we had one answer from the mid-20th century: Nuclear Energy.

The atom with masses as small as 1.6735575 × 10-27 and length scales of around 10-10 m is our current best bet at tackling climate change? As small as atoms are one must realise the immense magnitudes of energy they hold in the form of binding energy of its nucleus i.e. the energy required to hold the atom together. Einstein’s famous formula E = mc2 is what is in-fact used to calculate the energy that gets released. The difference in masses of the reactants and products of a nuclear reaction, called the mass defect, is multiplied by c2 which as we know is a massive number. Hence this explains the enormous amount of energies released during such reactions. One can extract this energy methodically via nuclear reactors using a fuel source-fissile material.  The energy released by an average sized nuclear reactor in a day is of the order of 1013 J! A measure of the efficiency of  such power/energy generating plants is the so-called capacity factor which is defined as the ratio of the actual energy output during a specific period of time to the maximum energy that can theoretically be produced during the same period. Nuclear energy has a capacity factor of 93% twice that of coal. Currently this amount of energy at these rates of efficiency can be produced by no other source . Moreover, the carbon footprint associated with actual energy production or running of the nuclear power plant is almost nil. This, coupled with the high energy densities of the fuels, makes it a leading contender in providing a potential solution to the current climate change crisis. Current estimates of nuclear fuel reserves suggest that there is enough to power all the nuclear reactors in the world for 200 more years! To get a sense of this note that a volume of ideally enriched uranium fuel of the size of a golf ball is sufficient to provide an average human being more than sufficient to meet the energy needs for their lifetime. Despite not being a popular source due to its high initial setup cost’s nuclear energy currently responsible for up to 10% of global electricity generation, in spite of only being dominantly used in around 30 countries or less.

There are multiple fuel source categories such as oxide fuel, metal fuel, non-oxide ceramic fuels, liquid fuels etc. But the dominant fuel used in most nuclear reactors is oxide fuel of Uranium-235. Although to achieve the efficiency and numbers we have just stated above one needs to enrich mined uranium by percentages of around 3-5 % To ensure a sustainable chain reaction of the neutrons, the exact percentages may vary based on type of reactor and other factors/requirements. As a result, less than 1% of mined uranium can actually be used as fuel. Some of the principal methods that are widely used to enrich fuel are gaseous diffusion, gas centrifuge and laser separation.

As it is with everything there is no light without the dark and so it is with uranium fuel. extracting/ mining uranium is a high energy consuming process with a large carbon footprint! And there are safety risks also associated with its transportation, treatment and back-end activity associated with spent nuclear fuel management. However there exist certain strategies such as Twice-through fuel cycles and advanced fuel cycles which are aimed at reducing the mitigating and avoiding such issues. 

A further possibility to handle the issue is via using alternative fuels such as Thorium which provide a better alternative! Almost all the thorium that is mined may be used as fuel unlike uranium. Other advantages are that it produces far lesser nuclear waste and is much safer! But almost every reactor currently works only on uranium. There’s always a catch isn’t there ? The problem is that while thorium is extremely fertile i.e. All of it as is mined in theory can be transmuted into fissile material which is the actual fuel that can work in a nuclear reactor it is not fissile itself i.e. it  cannot be directly used as nuclear fuel. However there is currently a lot of research going around in order to develop efficient thorium fuel cycles that may be used by the nuclear reactors! Which sure seems like a step forward in the right direction. 

One of the other disadvantages with nuclear energy are high investment energy sources. However, one can say for certain that we are more capable today in handling nuclear energy than we have ever been in the past. And it is certainly a worthwhile investment. Surely its advantages can be weighed over its disadvantages. As a result, Further research in nuclear reactor methods, Alternative fuel cycles and safety protocols can immensely boost the impact nuclear energy may have in pulling back the adverse effects of climate change. To quote an Indian physicist, the late Dr Homi Bhabha: “No energy is more expensive than no energy“. 

One way of measuring how “effective” a process (in this case, a type of energy production) is, is by doing a life-cycle assessment (LCA). LCA takes into account the extraction of the fuel, processing, distribution, and disposal of the waste.  A life-cycle assessment can measure the impact that the production of nuclear energy could have. An LCA from a 2017 study predicts that the life-cycle emissions from fossil fuels with carbon capture and sequestration plants to be between 78 and 110 gCO2eqkWh⁻¹ by 2050. The same study gives the life-cycle assessment for a combination of nuclear, wind and solar to be between 3.5 and 11.5 gCO2eqkWh⁻¹. Another study on nuclear power says that so far, nuclear power has prevented 64 gigatonnes of CO2 greenhouse gas emissions and 1.84 million air pollution-related deaths (as of 2013) and could prevent another 80-240 gigatonnes of CO2 and 420000 – 7.04 million deaths by 2050.

Fusion energy has been in development for decades and it’s a common joke that fusion energy is always thirty years away. The strife towards fusion is because there is minimal environmental impact, unlike fission reactors fusion produces no radioactive waste, and even if there would be a nuclear meltdown the radioactive material (tritium) is only a transition element which is present only in small amounts in fusion reactors. The half life of tritium is around 12.3 years and hence it would not render the facility radioactive for centuries. Also if there would be a breach in the reactor, the plasma would be extinguished meaning the reactor will be intrinsically safe. The only byproduct of the reactor is helium which is not a greenhouse gas, and being the second lightest element, it would ascend in the atmosphere and drift off into space. Fusion is when you take two atomically light nuclei and smash them together to create a heavier nuclei, however the heavier nuclei is not an exact sum of the mass of the two original ones hence the extra mass is converted to energy accompanied by the release of a couple of bosons. There are several different types of fusion reactors currently being researched and developed, some examples being magnetic confinement fusion (MCF), inertial confinement fusion (ICF), Stellartor and magnetized target fusion (MTF). MCF, as it might sound, is when you confine a plasma within a volume and heat It enough so that fusion is possible. However the temperatures required to initiate fusion such that on average a particle has enough energy to break the Coulomb barrier is around 170 million degrees kelvin, which is roughly 11 times the temperature of the core of the sun! So you can imagine why physicists are having such a hard time developing this technology. However MCF currently holds the most hope for a fusion future as an experimental fusion reactor has been heavily invested  in by India, the EU, USA, Korea, Russia and Japan, which is designed to show the scientific feasibility of fusion as an energy source. It is set to have its first plasma test at the end of 2025, but will only be fully operational by 2035. It is designed to have a Q = 10, meaning it will produce ten times the amount of energy it ingests. If the reactor is deemed successful in achieving its Q value and testing the feasibility of fusion. A new fusion reactor will be built called DEMO which will be used to produce electricity, which is scheduled to be completed by the 2050s. Even though fusion shows great promise it is a technology of the future and should not be relied upon in dealing with the climate crisis, because for the moment reducing carbon emissions using fusion is just a fantasy. We cannot rely on the possible technology of the future to solve today’s problems.