1. Nuclear Basics
2. Nuclear Power Generation & Safety
3. Fuel Cycle and Waste Management
4. Radiation and Daily Life
5. Myths About Nuclear Energy and Radiation

1. Nuclear Basics (Learn more about Nuclear Science & Radiation)

What are nuclear fission and nuclear fusion?
Nuclear fission refers to the process in which the nucleus of an atom splits into smaller parts (lighter nuclei that are highly radioactive) and releases neutrons, radiation and large amounts of energy. Today, a nuclide called Uranium 235 is the only natural material that can be split easily.

Nuclear fusion refers to the process by which two or more atomic nuclei join together to form a single heavier nucleus. An even larger amount of energy will be released during the process, and possibly together with some sub-atomic particles dependent on the ingredients for the process. Nowadays, humankind is exploring joining two Hydrogen nuclides, namely Deuterium and Tritium, by fusion to produce energy.
Why do we use Uranium 235 for nuclear fission?
Uranium 235 is the only naturally-found nuclide that could carry out nuclear fission. The other 2 nuclide that could carry out nuclear fission, Plutonium 239 and Uranium 233, could hardly be found in nature. They are obtained from the conversion of Uranium 238 and Thorium 232 respectively.
What are the differences between a nuclear reactor and a nuclear bomb?
Natural Uranium contains only 0.7% of Uranium 235 which can readily undergo fission while the remaining 99.3% of Uranium 238 is much more resilient to fission. It will be necessary to raise the enrichment of Uranium 235 above 90% for Uranium to become bomb material. In contrast, the Uranium 235 enrichment of a typical nuclear reactor is less than 5%. So a nuclear reactor will not explode like a nuclear bomb from the perspective of Physics.

A good analogy would be to compare alcoholic spirits to beer. Alcoholic spirits, such as Vodka, typically have a 40% alcohol content, and are highly flammable. Beer, which generally has an alcohol content of less than 5%, does not burn.

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2. Nuclear Power Generation & Safety (Learn more about Nuclear Power Generation and Nuclear Safety)

Is Nuclear Energy a highly productive source of power?
Triggered by just one neutron, the nuclear fission process, which generates nuclear power, releases massive amounts of heat and more neutrons that create a self-sustaining chain reaction. Therefore, nuclear power is considered as a highly productive energy source.

A simple analogy can be used to compare the amount of fuel needed from different kinds of energy sources to generate the same output of electricity. To generate 400kWh of electricity, we need:
  • 12 g of Uranium
  • 70 m3of Natural Gas
  • 90 kg of Oil
  • 140 kg of Coal
  • a wind farm with 40m2 to run for a year

Furthermore, a nuclear power station may operate almost continuously without limitation of seasonal and weather conditions.
How does a nuclear power station affect the environment?
During operation, a nuclear power station will produce a certain amount of radioactive waste. The amount is small on an industrial scale and can be managed within our current level of technology without affecting the environment.

The nuclear power station will also discharge a minute amount of radioactivity in a controlled manner into the air and the water. The amount is very small in practice and the level of radioactivity is low that any nearby resident or the environment is not affected.

Like any other power station, it will also discharge its unused heat into the environment, either into the sea via seawater taken in for cooling or into the air as steam from the cooling tower. The amount of water extracted and the rise in temperature in the discharge are controlled so that the environment is not affected.

A nuclear power station will operate a continuous programme to monitor its surrounding ecology and radiation level to control any possible impact.
Is it a must to build nuclear power stations by the sea?
Any power station will need plenty of water to carry for cooling, so building by the sea will facilitate this. Nuclear power station can also be built inland where cooling towers are used.
How are nuclear accidents classified?
The International Atomic Energy Agency (IAEA) set up the International Nuclear and Radiological Event Scale (INES) to facilitate communication to the public of the safety significance of nuclear events.

INES has 7 levels. The upper levels (4-7) are termed as accidents and the lower levels (1-3) are termed as incidents. Events that have no safety significance are classified Below Scale or Level 0 and are termed deviations. They are classified according to the decrease in safety measures at the nuclear station, the extent of decrease in safety protection and the exposure of the people and the environment to the resulting discharge of radiation.

A distinct phrase has been attributed to each level of INES in order to express the increasing severity of events from Level 1 to Level 7. These are: anomaly, incident, serious incident, accident with local consequences, accident with wider consequences, serious accident and major accident.
Are there international organisations which oversee the operation of nuclear power stations worldwide?
The International Atomic Energy Agency (IAEA) provides safety guidelines and frameworks on the operation of nuclear power stations. The government authorities of the respective countries will strictly regulate their nuclear power stations according to their national criteria that very often make extensive reference to those guidelines and frameworks.

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3. Fuel Cycle and Waste Management (Learn more about Nuclear Power Generation)

Where could we find Uranium? How could we mine and mill it?
Uranium is a commonly found metal existed in many types of rocks and in seawater. 64% of world Uranium reserves comes from Kazakhstan, Canada and Australia. Mining is carried out either by traditional open-cast/underground excavation of typically 0.1%-2% ore or by “in-situ leaching” (ISL), which allows minimum surface disturbance through drilling deep down to the ore layer for extraction of dissolved Uranium. Milling involves a series of processes including dissolving Uranium and its recovery, precipitation and dry off. The milled Uranium will then go through a Conversion process, in which the Uranium Oxide is converted into a gaseous Uranium Hexafluoride (UF6) to make it ready for enrichment.
How is Uranium made usable in a nuclear reactor?
Natural Uranium contains about 0.7% of Uranium 235 which is the only type found in nature that is readily usable. In contrast, most of the nuclear power reactors need a concentration of Uranium 235 at around 2%-5%, so it is necessary to raise the concentration of Uranium 235 to this level before the material is usable in a reactor.

Industrial processes can be used to "enrich" Uranium 235 concentration in a stream of gaseous Uranium Hexafluoride to reach the required level, at the expense of "depleting" the concentration in a parallel stream. The process may either make use of the faster diffusion rate of the lighter Uranium 235 bearing Uranium Hexafluoride (UF6) gas through a membrane compared to the heavier Uranium 238 bearing UF6 gas, or more commonly the higher concentration of this lighter Uranium 235 bearing UF6 gas at the centre of a centrifuge. Industrial processes can be used to "enrich" Uranium 235 concentration in a stream of gaseous Uranium Hexafluoride to reach the required level, at the expense of "depleting" the concentration in a parallel stream. The process may either make use of the faster diffusion rate of the lighter Uranium 235 bearing Uranium Hexafluoride (UF6) gas through a membrane compared to the heavier Uranium 238 bearing UF6 gas, or more commonly the higher concentration of this lighter Uranium 235 bearing UF6 gas at the centre of a centrifuge.
How is nuclear spent fuel treated? How is human safety ensured?
Spent fuel contains fission products and is highly radioactive. Spent fuel assemblies are stored under water in a dedicated storage pool at the power station for cooling and radiation shielding. They are typically held this way for 5-10 years to allow the radiation and heat to decrease before they can be removed from the power station.

When the spent fuel assemblies are removed from the power station, they are stored inside a sealed cask to prevent leakage. They are then sent to be reprocessed or stored in a repository according to the requirements of the respective countries.
What kinds of nuclear wastes are produced from a nuclear power station?
There are Low-level Radioactive Waste, Intermediate-level Radioactive Waste and High-level Radioactive Waste:
  • Low-level and Intermediate-level Radioactive Waste refer to spare parts / components from the reactor and other contaminated materials used in the power station (e.g. staff clothing)
  • High-level Radioactive Waste refers to either spent fuel after being used for power generation or the remaining waste resulting from the reprocessing of spent fuel, depending on the national policy for either direct disposal of spent fuel or extract of its useful constituents.
What is the lifespan of a nuclear power station?
Most of the nuclear power stations are designed to have a working life of around 40 years. Given prudent operation and maintenance, the lifespan of modern Pressurised Water Reactors could be extended up to around 60 years.
What is nuclear power station decommissioning?
At the end of their useful lives, nuclear power stations have to be decommissioned and demolished. Their sites must then be cleaned up or decontaminated before being released for general use. Full decommissioning normally takes several decades. The time is taken to allow the radiation level to fall to a level that will allow decommissioning work being taken at a low radiation dose for the workers.

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4. Radiation and Daily Life (Learn more about Nuclear Science & Radiation)

What are the sources of radiation in everyday life?
About 85% of the radiation is completely natural. The sources of radiation in everyday life include:
  • Radon (42%)
  • Buildings and soil (18%)
  • Cosmic ray (14%)
  • Medicine (14%)
  • Food and drink water(11%)
  • Nuclear industry (1%)
How is radiation measured?
When we look at the amount of radiation being emitted, the unit of measurement is Becquerel (Bq) which is used to express the number of disintegrations of radioactive atoms in a radioactive material in a second.

When a person is exposed to radiation, energy is deposited in the body tissues. The amount of energy deposited per unit mass of human tissue is called the absorbed dose, which is measured in Gray (Gy).

On the other hand, under the same absorbed dose, different types of radiation (alpha particle, beta particle and gamma ray) have different effects on the human body. Sievert (Sv) is the unit indicating biological damage caused by the absorbed dose. (One Gy of absorbed beta or gamma radiation has 1Sv of biological effect; 1 Gy of alpha radiation has an effect of 20 Sv).
What are the health effects of radiation exposure?
The lowest level radiation dose that could conceivably increase one's likelihood of developing cancer is above 100mSv. A sudden large dose of radiation of 1,000mSv or above to the body will also cause acute radiation injuries that will, in turn, result in short-term symptoms such as nausea, vomiting, extreme fatigue and hair loss. A short dose of 10,000mSv or more can be fatal unless proper medical attention is received.

In our daily lives we are faced with radiation of at least several mSv per year and there is no indication that it is harmful at this level.
What are the principles of radiation protection? How do we protect ourselves?
The principle of radiation protection is to minimise our exposure to man-made radiation and assumes that such is hazardous, so the goal is to keep exposure as low as reasonably practical. (ALARP) .

There are 3 ways to protect ourselves from identified radiation sources, particularly those that are man-made:
  • Exposure time: The less time you are exposed, the lower the dose of radiation you will receive
  • Distance: The further away you are from the source of radiation, the less intense its effects will be
  • Shielding: Shield yourself behind a thick concrete wall or stay indoors. Thick concrete protective covers withstand radiation penetration very well

The above 3 ways apply in daily life, at work, and in emergencies. However, particularly in an emergency, it is important to listen to the information from the authorities and follow instructions on protective measures accordingly. For example, evacuation has its own risks and potential for injury so it must be undertaken with proper preparation and care.

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5. Myths About Nuclear Energy and Radiation (Learn more about Nuclear Science &       Radiation and Risk & Concerns)

Are we getting most of our yearly radiation dose from nuclear power stations?
About 85% of the radiation that people are exposed to comes from natural sources, which include food, drinking water, radon, soil, building material and cosmic ray as well as from each other. In contrast, the public receive an imperceptible amount of their radiation dose from an operating nuclear power station. Even a worker encountering radiation in a nuclear power station will typically receive less radiation dose at work than he or she receives from daily life.
Do nuclear power station workers have a higher chance of developing cancer?
There is a strict limit to the radiation dose to which a nuclear power station worker is permitted to be exposed. The annual dose limit is governed at both country and plant levels at such low limits no harmful effect has been observed. Workers' health and radiation levels are also regularly monitored to ensure that they are not harmed.
Is it true that white clothing can reduce radiation exposure?
White clothing is of no help but there are 3 ways of reducing exposure:
  • Staying further away from the source of radiation
  • Shortening exposure time
  • Shielding inside buildings with concrete walls
Can we protect ourselves against radiation exposure by eating salt?
Salt provides no protection against radiation exposure. Instead, stable iodine tablets could be taken before or within a few hours of the arrival of a radiation plume to effectively block the thyroid gland's uptake of radioactive iodine, thus reducing the risk of thyroid cancer. Stable iodine tablets are a restricted medicine and should only be taken according to government or medical instructions.

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