How to harness the energy released by nuclear fission, for the better or the worse.
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From the enigma of breaking the solid structure of the atom to the prodigiously quick events happening when succeeding, last week’s article covered fission with the observant eye of physicists. Check out the article on our website if you haven’t done so yet.
This week, our focus shifts to the energies at stake, and we step into the shoes of an engineer to envision the myriad ways of harnessing nuclear fission.
How can we harness the power of fission to generate energy for an entire nation? Conversely, how has it been employed as a monstrous weapon of mass destruction? Together, let’s uncover and comprehend the answers to these questions, with the hope of paving the way for a better tomorrow!
The tremendous energy of fission.
Nuclear fission is often associated with the release of immense energy, yet when we examine the outcome of this process at the atomic scale (as discussed in last week’s article), it may seem perplexing that no apparent energy emerges. This leads us to a fundamental question: where does this remarkable energy hide? To answer this query, we must first delve into the concept of energy itself.
As humans, we frequently equate energy with electricity, but physicists provide a far more intriguing perspective. Energy is a fundamental concept that refers to the capacity or ability to perform “work.” Essentially, whenever an event occurs in the universe, energy is intricately involved. Whether it’s the motion of planets in our solar system, the cohesion of protons and neutrons within atomic nuclei, or even the footprints left by humans on a sandy beach during the summer, energy is an inherent part of it all.
Given this broad definition, energy manifests in various forms: kinetic energy (related to motion), thermal energy (associated with heating or cooling), potential energy (the intriguing energy associated with merely existing in time and space), as well as nuclear energy (the energy stored within an atom, distinct from the energy released in nuclear fission), chemical energy, electrical energy, and numerous others.
Energy encompasses a multitude of manifestations, but it adheres to two principles. The first is that it is a scalar quantity, simply said: it can be quantified. The official unit to measure energy is the joule (symbol J). The second is that it follows the most elegant and crucial principles in physics: “Energy cannot be created nor destroyed; it can only change from one form to another.” A principle that might seem blurry, but that you experience every day. In the simple act of boiling water with an electric kettle, for example: you transform electrical energy from your power outlet, into thermal energy (the water getting hot).
Let’s now refocus on nuclear fission and explore the energy involved in this remarkable process.
As atomic nuclei break apart during fission, two smaller atoms are formed, and they repulse each other. Additionally, a few neutrons escape, and some light is emitted. This provides us with the physical picture of nuclear fission, but let’s translate it into the realm of energy. When we say, “Two smaller atoms form and repulse each other,” we are referring to kinetic energy, which arises from their motion. The phrase, “A few neutrons escape,” involves potential energy simply by virtue of their existence and mass. Finally, “light is emitted,” representing radiation energy. Here we have them, the energies at stake in nuclear fission! Among them, kinetic energy, originating from the movement of the newly created atoms, is the most significant, accounting for 83% of the energy released.
When we sum up all these energies, including those not explicitly mentioned, we find that the fission of an atom releases approximately 200 million electron volts, denoted as MeV (a unit used to measure energy on a smaller scale). While this might seem relatively small, considering that 1 eV is about 10^-19 joules, it is actually quite significant when compared to other forms of energy production. For instance, the energy released when burning coal amounts to just a few electron volts at most, which is roughly ten million times less energy per unit of mass compared to fission! In practical terms, this means that you would need 10 million kilograms of coal to produce as much energy as 1 kilogram of uranium. Isn’t it extraordinary? No wonder the discovery of fission has unlocked a whole new world of energy production for humanity!
Let me now explain the fascinating process of how we transform the kinetic energy generated by nuclear fission into the electricity that powers our homes and industries.
Controlling and exploiting nuclear fission to produce energy
So far, we’ve examined fission from an incredibly small-scale perspective. To comprehend how a nuclear power plant operates, it’s time to step back a bit and broaden our view to a macroscopic level.
As this part refers to a multi-part structure, it is easier to understand using schematics. We thank the Encyclopedia Britannica for making them incredible and usable!
At the core of a nuclear power plant, the extraordinary energy unleashed during nuclear fission initiates a fascinating chain of events. It’s crucial to remember that the energy resulting from fission predominantly manifests as kinetic energy, a product of the rapid motion of the newly formed atoms. Consequently, the design of a nuclear power plant revolves around the objective of harnessing this kinetic energy.
First, the nuclear fission process itself, the splitting of the atom, needs to occur, and it must happen safely. This requires careful consideration of several parameters.
While the majority of the energy released from nuclear fission results from the motion of the newly formed atoms, the process also generates a significant amount of radiation energy in the form of light. Most of this radiation is in the form of gamma (or γ) radiation. You might have heard about the dangers of nuclear “irradiation,” and gamma radiation lies at the heart of this issue. However, fission cannot occur without it. Therefore, it’s essential to find a way to protect against gamma radiation while still allowing the fission process to take place.
Solving the puzzle of shielding against gamma rays is not overly complex. Consider what you do when you want to shield yourself from light — you move into the shadow, behind a wall. Restraining gamma radiation involves a similar principle. Since you cannot eliminate gamma radiation from the fission reaction itself, you allow the reaction to occur and then ensure that the radiation cannot escape. This is achieved by conducting nuclear fission within an enclosed space surrounded by a thick, heavy wall. This container surrounds the “core” of the reactor (see Britannica schematics) making sure only the inside gets irradiated.
The nuclear fission reaction can now proceed freely, allowing us to focus on how to harness the kinetic energy. Interestingly, this energy conversion process occurs somewhat spontaneously.
In our earlier explanation of nuclear fission, we mentioned that the newly produced atoms would move away from each other, with most of the energy of nuclear fission originating from this motion. However, within the confines of a nuclear power plant, these atoms are surrounded by various materials. As soon as these flying atoms collide with these materials, they begin to slow down. Think of it like playing with marbles: if you roll a marble on an empty road, it will travel quite a distance, but if you roll it on a road filled with other marbles, it will collide with them and gradually lose speed. However, remember that energy cannot appear or disappear; it can only transform. What occurs is that the fast-moving atoms transfer some of their energy to the particles they collide with. These particles now possess a higher energy density than they should, resulting in one fascinating outcome: heat, or as we mentioned earlier, thermal energy. Kinetic energy has now become thermal energy.
Now, two critical challenges must be addressed. First, the energy generated is so immense that without proper cooling, the entire area surrounding the core would melt, resulting in a catastrophic nuclear disaster. Second, a method must be devised to efficiently transfer this heat to a useful destination where it can be transformed into electricity. Once again, the ingenuity of scientists shines as they conceive a system capable of harnessing this heat while simultaneously cooling the core.
As we’ve observed on numerous occasions, science can sometimes demand incredibly complex considerations, while at other times, it offers surprisingly straightforward solutions. In this case, the resolution to the dual problem lies in a combination of both complexity and simplicity, as it harnesses one of the most common substances on Earth — water — in an exceptionally efficient and ingenious manner.
To ensure containment and minimize the risk of contamination, the water system is divided into three independent sections.
The first section encases the core, and due to its direct exposure to the fission reaction, it must remain isolated and unchanged. Nevertheless, it continues to circulate. As this water becomes extremely hot, it flows through another cooling system. By passing through pipes arranged in an old radiator fashion, the thermal energy acquired from the fission reaction is transferred to the second section.
The second part of the system is where the magic happens, where our energy is finally transformed into the electricity we need. To achieve this, this section employs the same principle as the previous one: it allows the water to become exceedingly hot, reaching the point of boiling and producing steam. Due to the high temperature and the enclosed system, the resulting gas becomes highly pressurized and moves rapidly through the system in an attempt to cool down. In this process, thermal energy is partially transformed back into kinetic energy. This motion is then harnessed to spin a turbine, ultimately generating the desired outcome: electrical energy.
As a security measure, the second system is also isolated, and thus, a third open system is required to cool down the entire process and ensure the integrity of the power plant. Typically, this system is directly connected to a nearby river. Water from the river is circulated through the second section using tubes to capture the thermal energy. The now-heated water is subsequently released into the environment as vapor. This final stage is facilitated by the large cooling towers often associated with nuclear power plants.
And there you have it! The operational process of a nuclear power plant — a truly remarkable demonstration of human ingenuity. It involves harnessing the conversion of initial kinetic energy into thermal energy by heating water, turning it into steam, and utilizing this motion to spin a turbine and generate electricity. All of this is achieved while maintaining a substantial margin of safety, effectively isolating the radioactive core from any potential issues.
What about the other infamous use of nuclear fission then?
How not to control nuclear fission?
While the details of atomic weapons are highly classified military secrets, the scientific understanding of the process is not. To comprehend it, let’s take a step back. Last week, we explained how fission occurs and what results from it. However, we omitted a crucial aspect: the chain reaction.
Fission is indeed a high-energy event, but it’s only useful if it happens more than once. So far, we’ve been discussing it as if it only occurred once. However, for nuclear fission to be exploitable — whether for weapons or power generation — we need more than just one fission event. This is where the chain reaction becomes pivotal.
The concept is straightforward: to initiate the breaking of atomic nuclei and start the fission process, we need a neutron. Once the atom breaks, a few neutrons are produced and released. But here’s the key point: these newly produced neutrons don’t simply vanish into the void. We’re not dealing with a single uranium atom; we’re dealing with countless atoms nearby. Consequently, these emitted neutrons are likely to collide with nearby uranium atoms, initiating new fission reactions. As a result, more neutrons are generated and continue this process in an ongoing chain, creating a cascading effect until there are no more atoms left to split. This is the essence of the chain reaction.
In a nuclear power plant, the controlled harnessing of the energy from these successive fission events allows for stability and controlled power generation. But what happens if you don’t manage or transform this immense energy? What if you fail to maintain stability? In that scenario, millions upon millions of atoms undergo fission simultaneously, releasing an enormous amount of energy. This energy wave proceeds to excite and heat neighboring atoms, causing them to undergo fission as well, resulting in a catastrophic chain reaction. From a macro perspective, this results in a monstrous explosion, destroying, burning, and radiating its surroundings.
While a nuclear power plant shines as a beacon of human ingenuity, an atomic weapon resembles a stark masterpiece of brutalism: initiate the fission process and then unleash total devastation. It’s a deceptively simple and brutally effective concept, one that has left a trail of disastrous history in its wake.
Initially, nuclear fission was nothing more than a remarkable discovery driven by scientists’ passionate pursuit of understanding the atom. However, over time, it evolved into many things, including a source of carbon-free energy and, chillingly, a weapon of mass destruction that respects no boundaries or defenses.
Nuclear fission has the potential to address numerous challenges, but when wielded by those who lack proper control and responsibility, it can become a weapon that unleashes death and destruction. Through these articles, which have covered the history of nuclear fission, the underlying scientific processes, and its practical applications, my aim has been to equip you with the knowledge needed to comprehend and evaluate nuclear fission. I hope that you now emerge from this reading with a deeper understanding, prepared to engage in discussions, cast informed votes, and contribute to shaping a better tomorrow through the power of understanding.
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Thanks for reading this week’s longer episode! Next week, our focus will shift to another pressing challenge of our time: artificial intelligence and its impact. Trust me, you won’t want to miss it!
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