Safety of Nuclear Reactors

Safety of Nuclear Reactors

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Nuclear reactors are used for a variety of purposes, from energy production to isotope production to powering space probes. But, due to the potential dangers of radiation, safety is a major concern. To ensure the safety of nuclear reactors, industry and science have developed various protocols and measures to prevent accidents and reduce the impact of any that do occur.

One of the most well-known nuclear accidents is the Chernobyl disaster of 1986. At the time, the number four reactor of the Chernobyl Power Plant experienced a nuclear accident due to a combination of reactor design flaws and human error. As a result, over 130 staff and firefighters were exposed to high doses of radiation, leading to acute radiation syndrome. To reduce the spread of contamination, a sarcophagus was built, and later enclosed, around the reactor.

Dangers of nuclear power

When using radioactive isotopes in nuclear technologies, waste management is a significant challenge. If waste is not handled correctly, it can cause nuclear contamination. Additionally, there is a risk of uncontrolled reactions in nuclear power plants, as demonstrated in the past by incidents such as Chernobyl and Three-Mile Island.

Another critical issue in nuclear safety is the risk of nuclear weapons being created using fissile material. Fissile material is any isotope capable of sustaining a fission reaction, which releases a large amount of energy.

Overall, the safety of nuclear technology and reactors requires careful management of waste, prevention of uncontrolled reactions, and control of fissile materials to prevent the creation of nuclear weapons.

Nuclear contamination

Nuclear technology and reactors make use of materials that emit radiation, known as nuclear fuel. Radiation is dangerous for living beings as it can ionise atoms or molecules. Ionisation happens when high-energy particles interact with an atom, changing its electrical state by removing electrons out of their orbits. In nuclear technology, any element that emits radiation is shielded by a dense wall of material that blocks the radiation. However, radiation can escape (if something fails in the structure, for example), causing nuclear contamination.

Alpha, Beta, and Gamma Radiation are the most common forms of ionizing particles have the greatest mass, approximately four times the mass of a proton or neutron and approximately ~8,000 times the mass of a beta particle. Beta particles have less mass than alpha particles and are more penetrating. Gamma rays are pure energy and are similar to visible light, but have much higher energy. Gamma rays are often emitted along with alpha or beta particles during radioactive decay. Gamma rays have the greatest penetrating power and the lowest ionizing power.

Nuclear waste

During nuclear reactions, heavy isotopes convert into lighter elements. Lighter elements from the nuclear reactions are, in some cases, radioactive too and are called residuals. Residuals cannot be used, and they are stored until their radiation emission decays to a point where they are no longer dangerous. Nuclear waste can also come from nuclear medicine that uses radioactive isotopes for tracing, imaging techniques, and cancer therapy.

Some nuclear waste has a significant half-life and will be radioactive for thousands of years. Other waste is short-lived and is only radioactive for a few years. This short-life waste can be contained in near-surface burials, and facilities for this type of waste can be found in Finland, Japan, the UK, and the USA. Waste with a longer decay period must be sent to deep geological storage facilities.

If the waste is not stored correctly, it can cause nuclear contamination. Therefore, proper storage and disposal of nuclear waste are crucial to prevent any potential harm to the environment and living beings.

To understand the decay processes and storage of radioactive isotopes, check out our explanation on Half Life.

Reactions out of control

Nuclear fission is the process of breaking large atomic nuclei into smaller atomic nuclei to release a large amount of energy. This process is usually done by forcing the nuclei to absorb an extra neutron, which causes it to quickly break into two parts. The process is accompanied by the release of a large amount of energy and gamma photons. When a uranium-235 nucleus absorbs an extra neutron, it quickly breaks into two parts, releasing two neutrons and two lighter elements. The ejected neutrons are then partially slowed down so that other heavy atoms can absorb them and break. This chain reaction increases the number of ejected neutrons that interact with other heavy elements and heats the nuclear core. In a power plant, this heat is used to convert thermal energy into electricity. If the reaction is not controlled, an out-of-control reaction can occur.

The process converts the uranium-235 into uranium-236

In nuclear reactors, the core is made of densely packed fissile material (nuclear fuel). As soon as an isotope breaks away releasing neutrons, a chain reaction begins.  In nuclear reactors, rods are lifted to start the reactions. This design practice/working mechanism is used so that reactions always start at a minimum of activity. They are only lifted when more energy is needed. The rods are made of materials that can absorb the neutrons from the nuclear reaction without entering into fission. The more neutrons they absorb, the fewer neutrons are available for the nuclear reaction.The rods are so effective that in the case of emergency, they can be dropped suddenly, and, when necessary, they shut down the reactor completely. Below is a figure showing the event of dropping the rods suddenly.

A shows the moment when the reactor rods are partially removed so that the reactor can gain power. B shows when the rods are suddenly dropped so that the reaction slows down
A shows the moment when the reactor rods are partially removed so that the reactor can gain power. B shows when the rods are suddenly dropped so that the reaction slows down

Nuclear proliferation

Nuclear material can be used to create nuclear weapons. The International Atomic Energy Agency and the United Nations Office for Disarmament Affairs deter the use of nuclear material for nuclear weapons by detecting early misuse of nuclear technology and actively enforcing and promoting treaties to ban nuclear proliferation.

Safety measures in nuclear power

Nuclear power and technologies have high regulations for safety. This includes the way reactors are built and how waste is managed.

Precautions taken to prevent a nuclear accident

Nuclear reactors are designed with numerous safety measures to ensure their proper functioning and prevent accidents. Some of these measures include:

  1. Control rods: These rods are used to absorb excess neutrons and control the rate of the nuclear reaction in the core. By inserting or removing these rods, the reactor's power output can be adjusted.
  2. Remote refuelling: Reactor refuelling should be carried out remotely, and the process can vary depending on the plant and design.
  3. Structural containment: The structural components of a nuclear power plant should be able to withstand seismic activity and heavy impacts on the outer side. On the internal side, heat and radiation will degrade the materials used in the reactor core construction. As a result, materials that can withstand these conditions over a longer period than the plant lifecycle must.
  4. Diverse: A of sensors, including cameras, thermal sensors, and radiation sensors, are used to collect information about plant operations. This information is then used to update the reactor crew.
  5. Redundant systems: Many mechanical and electrical systems are duplicated or triplicated to ensure that a failure of one component will not affect the plant's overall operation.

These safety measures are essential to prevent accidents and ensure the safe operation of nuclear reactors.

Nuclear waste storage

Nuclear waste storage is an essential technique used to isolate waste materials generated by nuclear technology. The waste can be classified into three categories: low-level waste, high-level waste, and transuranic waste, which can emit alpha particles and consist of elements heavier than uranium.

The type of waste and its level of radioactivity determines the type of containment required. Low-level waste can sometimes be placed in faraway locations and isolated in shallow burials.

However, high-level waste requires more secure containment methods. These methods include deep geological repositories that can reach depths of up to one kilometre. The waste is packed in a tight container that is sealed and shielded to prevent leaks. These repositories are constructed in geologically stable areas to prevent potential geological changes that could cause leaks.

Transuranic waste can also be stored in deep geological repositories or placed in a specially designed waste isolation pilot plant (WIPP) in New Mexico, which is designed to isolate waste for thousands of years safe and secure storage of nuclear is damage and the safety of future generations. Ongoing research and development of storage methods and technologies are to ensuring the safe and secure disposal of nuclear waste.

Low-level radioactive waste disposal
Low-level radioactive waste disposal

High-level nuclear waste requires a deeper burial, known as deep geological repositories, to ensure its long-term containment without maintenance. These burials can extend to depths of up to one kilometre and are designed to protect against leaks. One example of such a system under construction is Onkalo in Finland.

Deep geological repositories are constructed in geologically stable areas to prevent potential geological changes that could cause leaks. The waste are sealed and shielded a tight.

However deep burial sites is still being researched. to the high temperatures generated by nuclear materials at deep depths, the rock type must be able to withstand those temperatures for an extended period. Granite is one of the primary candidates for this task, as it is an erosion-resistant rock that can last for hundreds of millions of years.

The safe containment of high-level nuclear waste is critical to prevent environmental damage and ensure the safety of future generations. As such, the continuing research and development of deep geological repositories are essential to ensure the safe and secure disposal of nuclear waste.

Future of Fission

Nuclear power plants are classified as third-generation power plants, but there is still room for improvement in their safety measures. Fourth-generation plants are being designed with reprocessing capabilities to recover used nuclear fuel, making the process more efficient and producing less waste with a shorter decay period.

Other reactor designs, such as molten salt reactors, are being developed to increase safety measures and decrease the risk of dangerous meltdowns. These reactors function with fuel in a molten state and at lower pressures.

Nuclear technology poses many challenges that require increased safety measures, including nuclear waste, contamination, control of nuclear reactions, and the proliferation of nuclear weapons. High-level nuclear waste is stored in deep geological repositories that must be geologically stable for long-term containment. Control rods are used to reduce or stop the reaction in the nuclear reactor core.

Nuclear proliferation is another danger technology. Countries and organizations have treaties to creation of nuclear weapons.

To ensure the safe and secure use of nuclear technology and development of safety measures and new reactor designs are critical.

Safety of Nuclear Reactors

What safety features are used in nuclear reactors?

Some safety features used in nuclear reactors include controls rods to stop or control the reaction, remote refuelling processes, robust structural components, sensors to monitor the reactor status, and redundant mechanical and electrical systems.

Are nuclear reactors harmful?

Nuclear reactors are harmful because they can pose a risk to living beings if they are not built and controlled properly.

What is the safest nuclear reactor design?

One of the safest nuclear reactor designs is the molten salt reactor. Molten salt reactors function with fuel that is in a molten state and at lower pressures, which decreases the risk of dangerous meltdowns. 

Is nuclear energy radioactive?

Because nuclear energy uses the decay of radioactive elements, it uses a process that emits radiation. The emissions, however, are contained within the core of the reactor, which is shielded from the persons working on the plant. The energy produced by these plants is not radioactive.

Which is the best nuclear reactor?

Molten salt reactors are considered as better or safer reactors in comparison to conventional reactors.

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