<span class="bsf-rt-reading-time"><span class="bsf-rt-display-label" prefix="Reading Time"></span> <span class="bsf-rt-display-time" reading_time="5"></span> <span class="bsf-rt-display-postfix" postfix="mins"></span></span><!-- .bsf-rt-reading-time -->Where are we with the safer nuclear option known as nuclear fusion?

Where are we with the safer nuclear option known as nuclear fusion?


Danish Sunasra
2021-02-22 09:03:09
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The world’s largest experimental nuclear fusion reactor is in development in Provence, southern France. ITER (originally the International Thermonuclear Experimental Reactor) is an international nuclear fusion research and engineering megaproject funded and run by seven member entities: the European Union, China, India, Japan, Russia, South Korea, and the United States; Overall, 35 countries are participating in the project directly or indirectly. The project was initiated in 1988 and is expected to start full deuterium-tritium fusion experiments in 2035. That’s a very long project time. The Manhattan Project to develop the world’s first nuclear weapon lasted for 6 years. One would be correct to assume that it must be a behemoth of a task with far-reaching consequences for humanity. As Matt McGrath rightly titles his BBC article –‘Nuclear fusion is a question of when, not if’, how long will it take us to produce energy using nuclear fusion?

WHAT IS NUCLEAR FUSION?

Nuclear fusion is the process that powers the sun and the stars. Fusion is the fusing of two or more atoms to form different atomic nuclei and subatomic particles. The mass lost in the process is converted to energy. For the nuclei of two atoms to overcome the aversion to one another caused by having the same charge, high temperatures and pressures are required. Temperatures must reach approximately six times those found in the core of the sun. At this heat, the hydrogen is no longer a gas but a plasma, an extremely high-energy state of matter where electrons are stripped from their atoms.

WHY NUCLEAR FUSION AND NOT FISSION?

With the money, time, and effort being spent on this project, the question arises if it’s worth it? Can we improve the way by which we produce nuclear energy? The biggest problem with nuclear fission is the storage of dangerous radioactive end products. The storing and reprocessing are further complicated by the long half-life of the radioactive materials in the nuclear waste. For example, some of the components can retain half of their dangerous levels even one million years later after production. Until we find a safe and reliable method, disposal of nuclear wastage is just a dangerous risk we are passing onto our progeny. Even with all the risk measures taken, there is always a risk of accidents with devastating consequences which cannot be predicted.

These points were kept in mind while planning.

From the ITER website:

  • It is absolutely impossible for a Fukushima-type accident to happen at ITER. The fundamental differences in the physics and technology used in fusion reactors make a fission-type nuclear meltdown or a runaway reaction impossible. The fusion process is inherently safe.
  • Even in the event of a cataclysmic breach in the tokamak, the levels of radioactivity outside the ITER enclosure would remain very low. The ITER Preliminary Safety Report presents an analysis of risks that demonstrates that during normal operation, ITER’s radiological impact on the most exposed populations will be one thousand times less than natural background radiation. For postulated “worst-case scenarios,” such as fire in the Tritium Plant, the evacuation of neighboring populations would not be necessary.
  • Fusion reactors, unlike fission reactors, produce no high activity/long life radioactive waste. The “burnt” fuel in a fusion reactor is helium, an inert gas. Because the half-life of most radioisotopes contained in this waste is lower than ten years, within 100 years the radioactivity of the materials will have diminished in such a significant way that the materials can be recycled for use in other fusion plants.

SO WHERE ARE WE WITH FUSION ENERGY?

This is not the first time a nuclear fusion reactor is being made. “Fusion machines” were already operating in the Soviet Union, the United Kingdom, the United States, France, Germany, and Japan by the mid-1950s. A breakthrough occurred in 1968 in the Soviet Union when researchers were able to achieve temperature levels and plasma confinement times — two of the main criteria to achieving fusion — that had never been attained before. The Soviet machine was a doughnut-shaped magnetic confinement device called a tokamak. The Tokamak is an experimental machine designed to harness the energy of fusion.

FUSION PROCESS

Inside a tokamak, the energy produced through the fusion of atoms is absorbed as heat in the walls of the vessel. Just like a conventional power plant, a fusion power plant will use this heat to produce steam and then electricity by way of turbines and generators. Inside, under the influence of extreme heat and pressure, gaseous hydrogen fuel becomes a plasma that provides the environment in which light elements can fuse and yield energy. The charged particles of the plasma can be shaped and controlled by the massive magnetic coils placed around the vessel. As the plasma particles become energized and collide they also begin to heat up. Auxiliary heating methods help to bring the plasma to fusion temperatures (between 150 and 300 million °C). Particles “energized” to such a degree can overcome their natural electromagnetic repulsion on collision to fuse, releasing huge amounts of energy.

There have been various Tokamaks that have successfully operated but only for short durations, which is the main problem ITER is trying to solve. France holds the record for the longest plasma duration time of any tokamak: 6 minutes and 30 seconds. We are yet to produce a fusion machine that produces as much energy as is required to heat them which is defined by the Q ratio. Plasma energy breakeven (a Q ratio of 1) has never been achieved: the current record for energy release is held by JET, which succeeded in generating 16 MW of fusion power, for 24 MW of power used to heat the plasma (a Q ratio of 0.67). ITER aims to have a Q ratio of 10, which means producing 500 MW of energy for 50 MW of energy consumed which is a very audacious target. But it will not be striving alone in its quest—fusion machines all over the world have re-oriented their scientific programs or modified their technical characteristics to act either partially or totally in support of ITER operation.

SO WHEN WILL IT START OPERATING?

The project duration is a very long one. ITER project officially initiated in 1988 with conceptual design activities. Machine assembly was launched on 28 July 2020. The construction of the facility is expected to be completed in 2025 when commissioning of the reactor can commence. ITER’s First Plasma is scheduled for December 2025 and the deuterium-tritium operation is to start in 2035. That will be the first time the machine is powered on and the first act of ITER’s multi-decade operational program.

Decades of fusion research and generations of fusion devices have contributed to the design of ITER. ITER, in its turn, will contribute to the design of the next-generation machine—DEMO—that will bring fusion research to the threshold of a prototype fusion reactor. DEMO is the machine that will address the technological questions of bringing fusion energy to the electricity grid, which is the end goal.

ITER will be the largest of more than 100 fusion reactors built since the 1950s with the total price of constructing and operating the experiment expected to be more than €22 billion as of 2016. It’s a technological marvel no doubt and the achievements will be immense. It definitely will be a historic moment when we finally produce net energy from the fusion process.



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