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The ITER project aims to experimentally prove by 2035 that power produced through nuclear fusion reactions can be used as a viably sustainable source of energy.
ITER will be the first of its kind to produce more output power than input power through nuclear fusion, thus it will be a considerably significant milestone within the scientific community. As it will be made evident by the end, upon the completion of ITER, the power which it produces will not be used commercially.
This is due to its “Q ratio” being less than 20 as a result of expense.
Nuclear fusion is a naturally occurring phenomenon, this involves the binding of atomic nuclei with low atomic numbers to form heavier nuclei with the release of energy. Nuclear fusion takes place within the core of stars, this is possible thanks to the extreme pressure and temperature that exists within the core, which are estimated to be the equivalent of 250 billion atmospheres (25.33 trillion KPa) and 15,7 million kelvin, respectively.
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The sun releases energy at a mass–energy conversion rate of 4.26 million metric tons per second, which produces the equivalent of 38,460 septillion watts (3.846×1026 W) per second. This gargantuan proportion of power is the reason why scientists are building nuclear fusion reactor technologies such as ITER.
ITER is one of the most ambitious energy projects in the world today. In southern France, The ITER Members; China, the European Union, India, Japan, Korea, Russia and the United States have combined resources and are collaborating to build the world's largest tokamak, a magnetic fusion device that has been designed to prove the feasibility of fusion as a large-scale and carbon-free source of energy.
According to the ITER timeline, by 2035, Deuterium-tritium operations will begin. It is estimated that the ITER tokamak will be able to produce 500MW of output power at a temperature of 150 million K (10X the temperature of the core of the sun). The fusion of deuterium and tritium produces a helium nuclei alongside a neutron and a large quantity of energy. In reality ITER will act as a prototype for future nuclear fusion reactors which use this D-T reaction. ITER will allow scientists and engineers to develop the knowledge and technologies needed to proceed to a next phase of electricity production through fusion power stations.
At extreme temperatures, electrons are separated from nuclei and a gas becomes a plasma; an ionized state of matter similar to a gas. Composed of charged particles (positive nuclei and negative electrons), plasmas are nearly one million times less dense than the air we breathe and provide the environment in which light elements can fuse and yield energy.
As mentioned in the introduction, the ITER fusion reactor uses tokamak technology. A tokamak is a toroidal plasma confinement device which consists of a complex system of magnetic fields.
The helical magnetic field in a tokamak shown in figure 3, has two components: (1) a toroidal component, which points elliptically horizontal around the reactor, and (2) a poloidal component directed the vertically around the machine. Both components are necessary for the plasma to be in stable equilibrium. The toroidal magnetic field value of ITER on the plasma axis is 5.3T (see figure 5) and 6T in the poloidal field, which produces a maximum field strength of 12T .
In the ITER tokamak, deuterium and tritium nuclei will fuse to form helium, losing a small amount of mass that will be converted into energy. Most of the energy will be carried away by neutrons, which will escape the plasma and strike the walls of the tokamak, producing heat. In a fusion power plant, that heat would be used to make steam to turn a turbine to generate electricity, similar to existing power plants which use other sources of heat, like burning coal. ITER’s heat will be dissipated through cooling towers.
There are many parameters needed to specify a tokamak device which have many relations and constraints between them. One of these parameters is defined as the Q ratio of fusion output power (Pfus) to auxiliary heating power (Paux). For ITER, this Q ratio is 10, meaning there will be a power output equal to 10X that of the heating power (500 MW of fusion power from 50 MW of input heating power).
The Q ratio is only an approximation due to plasma energy leaks, this occurs through various means such as heat conduction, particle diffusion and radiation emission. Thus it is possible to derive the Q ratio for the maintained plasma as follows:
Suppose a plasma of temperature T, volume V and density n_e=n_D+n_T (where n_D is the density of deuterium and n_T is the density of tritium) is maintained during time τ.
The energy released (Efus) during the time τ is given by:
Efus= τPfusV (1)
The energy lost (Eaux) during the time τ is given by:
Eaux= τ(Paux+3n_e T)V (2)
Where the term 3n_e TV is the total kinetic energy of the plasma particles which can also be written as (3/2)n_e TV + (3/2) (n_D+n_T) TV.
Thus using the definition of the Q ratio, we can divide equation by equation to obtain:
Q= Efus/Eaux= Pfus/(Paux + 3n_e T) (3)
As it can be deduced from equation 3, the Q ratio is dimensionless and is thus used as a measure of the quality of the plasma fuel. [5]
Using equation (3) and the list of parameters for ITER in figure 6, the Q ratio for ITER can be determined:
Q= 410MW/(41MW+(3(1.01×〖10〗^20 m^(-3) )(8.5KeV)))
Thus following this calculation, it can be deduced that the Q ratio for ITER is 10 due to the fact that the term (3(1.01×(10)^20 m^(-3) )(8.5KeV)) is negligible, hence proving the theoretical quality of the plasma fuel.
From an economical standing point a Q ratio of 10 is still technically too low for an electrical company to produce a reasonably substantial profit. This is due to a lack of efficiency and thus losses made through the inability to achieve economies of scale. A minimum Q ratio of 20 is an ideal target for a commercial nuclear fusion reactor, this is because at this number, plasma will begin to ignite efficiently and self-burn meaning the plasma will not need to be continuously ignited which would incur costs.
The goal for ITER is to produce roughly 500MW of thermal energy in long pulses of at least 400 seconds. During each pulse exothermic nuclear reactions in the surrounding materials would be enhanced by 20% leading to an efficiency of approximately 40%. Other site power requirements would lead to a total steady power consumption roughly 200 MW. If this total thermal power were then converted to electricity at 33% (well within reach of commercial steam turbines), about 200 MW of electrical power could be generated. This would be enough to power a small to medium sized town. However, from a commercial standing point is not reliable because power will need to be supplied to the grid constantly (not in short bursts).
Unlike current fission reactors, ITER will have the advantage of reduced radioactive waste. Waste resulting from a tokamak fusion plant can be stored above ground, and after approximately twelve years most of the radioactivity would decay. On the other hand, in a tokamak fusion reactor, the diffusion of tritium and the radio activation could create challenging waste management and disposal problems, especially because components have to be replaced continually during the reactor’s operational lifetime.
ITER will be safer than conventional nuclear fission plants, primarily because the reactor always remains in a subcritical state. This eliminates the possibility of a meltdown and corresponding release of radioactive material into the surrounding environment. Even in the event of a malfunction, the amount of fuel contained in the reactor core is insufficient to cause off-site harm. On the other hand Lithium would be present in substantial quantities in a pure fusion plant; consequently, a lithium fire could break out, resulting in considerable release of radiation. Even when compared to fission systems; the risk of industrial accidents involving radiation release during construction, operation, and decommissioning should not be disregarded.
The ITER project initially called for £16.6 billion to be spent over thirty-five years, but leading figures at the ITER Development Agency recently said costs will almost certainly increase. This has led critics to question not only the financial viability of the ITER project, but also the feasibility of fusion-based power and the possibility of producing economically competitive energy. ITER’s price may seem high, but it should be recalled that its budget will be spent over thirty-five years and funded among eight partners.
ITER is intended to be the final stage before the construction of a full-scale commercial fusion reaction energy production facility that will be known as DEMO. There are limited design plans for DEMO, with no current agreements from any nations about the source of funding. But it is known that DEMO will have an even larger plasma volume than ITER, a much greater thermal energy output, and a steam turbine generator that will run off the thermal energy transferred from the cooling system producing electrical energy at a commercial scale (as shown in figure 4).
In conclusion, when ITER is fully constructed it will be able to produce power well within the commercialised threshold. If all construction goals are met within ITER’s schedule then ITER could theoretically start producing power from 2035 onwards (when deuterium-tritium operations begin).
Although ITER is suitable for commercialisation, economically it would not yield a high enough level of profit if operated in large enough environments, this is due to the fact that a 500MW output and Q ratio of 10 would not be able to achieve economies of scale, furthermore plasma will only be burnt in small 400s bursts meaning it will not be reliable for commercial use. On the other hand, ITER would have a Q ratio of 10 which would be an enormous experimental mile stone due to ITER being the first of its kind to produce more output power than input power. In addition to this scientists would be able to study the structural integrity of a commercial sized nuclear fusion reactor.
ITER’s success would allow for future generations of nuclear fusion reactors such as DEMO to be built. This would result in a reduction in the usage of fossil fuels thus leading to fewer carbon emissions. As a result of this governments may be incentivised to provide additional funding for ITER especially since it will be safer than conventional nuclear fission plants. In my personal opinion, if consistent funding is provided to ITER then it should be possible for ITER to be constructed and operational by 2035. However I also believe that realistically ITER would not be completed until at least 2040 due to increasing costs as mentioned by the ITER Development agency. Thus the construction and operation of DEMO could be delayed until 2060 – 2070. This means that carbon free power produced through nuclear fusion will not be commercially and economically viable for another half century.
References
Evaluating the ITER Project: A Leap Towards Sustainable Nuclear Fusion Energy. (2024, Feb 18). Retrieved from https://studymoose.com/document/evaluating-the-iter-project-a-leap-towards-sustainable-nuclear-fusion-energy
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