We'll be gathering exciting things to see over the summer, both as a warm-up to summer school and just for a look around. If you're interested in nuclear power and its future, come back here from time to time.
Reactor start-up
The TRIGA reactor is a training and research reactor without a pressurised core, so it cannot generate electricity from water vapour - all the heat is transferred to the surrounding water. It does, however, allow you to see how the reactor works. The video shows the reactor starting up and, in the video below, a close-up of the control rod moving and the heated water moving up the core.
Blue light is Cherenkov radiation - electrons travelling faster than the speed of light create an effect in the environment (water) that is similar in principle to the blast waves of a supersonic aircraft.
Radioactive waste
Nuclear waste is one of the most talked-about issues in this energy mix. But not because it poses a real risk in normal circumstances, as is often thought, but probably more because nuclear is the only energy sector where laws and regulations require the safety of the entire fuel cycle to be monitored and verified. This means that uranium (or any other nuclear fuel) moving from the mine to the enrichment plant, from there to the nuclear power plant and finally to the nuclear waste repository or reprocessing facility must be accurately documented. There is no such verification requirement for any other energy sector.
For example, used wind turbine blades can be chopped up and buried without the owner of the turbine being liable for any toxins leaching from the blades into the environment, and the silver used to make solar panels is generally of unknown origin once it leaves the factory. The mountains of oil shale ash can be seen by anyone who has been to East Estonia, but CO2 emissions are already being felt very seriously across the planet.
On average, it takes 0.5 kg of nuclear fuel to produce the amount of energy consumed in a person's lifetime, and about the same amount of waste, which today would be more accurately called "spent fuel". This is because the vast majority of the fuel 'used' in a nuclear power plant can be reprocessed (as is the case in France and Japan, but not in the US, due to legislation) and reused in a nuclear power plant. Generation IV breeder reactors also use "nuclear waste" as fuel, which means that today's waste could be the fuel for future nuclear plants.
During the use of nuclear fuel, various substances are formed in the fuel which inhibit the fission process and the fuel loses some of its efficiency. If the fuel becomes too inefficient, it must be replaced. The spent fuel is initially left to "cool" in the reactor pool and is later vitrified in a borosilicate glass, placed in a container and stored in a dedicated repository. Depending on whether the spent fuel is to be used later or not, a choice can be made between underground or deep storage. At a depth of several hundred metres in granite rock, spent fuel is safe for humans and the environment until its radioactivity level reaches the natural background.
High-level waste from the production of nuclear electricity in borosilicate glass disks, consumed on average per human lifetime.
Spent fuel containers in a modern storage facility in Ontario, Canada.
Onkalo kayak reservoir in Finland.
Small modular reactors - the future of nuclear power
For decades, nuclear power plants have been a powerful tool for mankind to generate emission-free electricity. However, because nuclear power plants are somewhat more complex to build than coal-fired plants, for example, they have so far been built on the principle of "the bigger the better". A typical reactor has an electrical capacity of around one gigawatt and often has several reactors in a single plant. But the world has changed a lot over the decades, and so has the economy and the energy sector.
Large nuclear power plants have proven to be too costly under today's conditions and take too long to build given the rate of growth in energy demand. Moreover, safety requirements have become increasingly stringent over the years, which means that a large nuclear power plant has to be "upgraded" at the planning or construction stage, which is costly and time-consuming for older reactor types.
Since then, work has started in many countries to design and produce small modular reactors. The term "modular reactor" means that its components are manufactured and assembled in a factory, not on a construction site - just like a modular house. The word 'small', however, means that the electrical power of such reactors does not exceed 300 MW.
Small modular reactors are simpler and faster to build, have standardised components and are therefore easier and cheaper to maintain. As the reactor is immediately designed with all modern safety requirements in mind, a great deal of attention has been paid to safety, including in particular passive safety, which prevents accidents and malfunctions caused by human error or malicious intent. A reactor with these safety parameters does not require a large safety envelope, which in the case of large plants can extend over a distance of tens of kilometres. In addition, the plant can start generating electricity as soon as the first reactor is commissioned, thus recouping the initial investment, and more reactors can be added later if necessary.
Fermi Energia has selected reactors from five manufacturers - General Electric/Hitachi, Moltex Energy, NuScale, Terrestrial Energy and Ultra Safe Nuclear Corporation - to be evaluated for commissioning in Estonia. However, before selecting the most suitable reactor technology, it is necessary to find a suitable site for the plant, design the legislation, assess the necessary safety requirements, calculate the costs and benefits of the project and train experts.
Radiation and the risk to humans
The effect of radiation on an organism is best described by the equivalent dose, which is measured in Sv. When measuring radiation dose, the time spent exposed to radiation must also be taken into account.
For example, the normal range for natural background radiation is considered to be 2.4 millisieverts per year (mSv/y) on average. About half of this dose (1.26 mSv/y) is from inhaled air, 0.29 mSv/y from food, 0.48 mSv/y from the ground and 0.39 mSv/y from cosmic radiation. If we add to this the calculated average dose from X-rays, CT scans (the main source of anthropogenic radiation is medicine, with an average of 0.6 mSv/a), nuclear accidents and nuclear testing, the total average dose to the average person is 3.01 mSv/a. Converted into hours, this is 0.00034 mSv/h or 0.34 micro-sievert per hour (μSv/h).
The radiation levels around us vary greatly from region to region - for example, in Brazil, the popular Guarapar beach has 90 μSv/h (micro-sievert per hour), while next to the Chernobyl nuclear reactor sarcophagus it is 90 μSv/h (micro-sievert per hour). more than 100 times lower - 0.81 μSv/h. In comparison, the average natural radiation flux in Finland is 0.9 μSv/h, in Estonia 0.8 μSv/h. In an aeroplane flying at an altitude of 10 km, the radiation background is about 5 μSv/hour.
Thus, a background radiation dose of about 0.1-1 μSv/h at ground level, plus radiation doses from air travel, medical research and other human activities, up to 10 μSv/h in the short term, can be considered normal.
Higher radioactive sources, such as X-ray machines, deliver higher doses of radiation over a short period of time - for example, a single CT scan can give a person a dose of 10-30 mSv, or an accumulated dose of 80 mSv over 6 months in an international space station.
However, the doses that pose a health risk are significantly higher and depend largely on the duration of exposure. For example, the minimum dose that has been shown to increase the likelihood of cancer is 100 mSv/y, or 100 000 μSv/y, but in radiotherapy, for example, very localised doses exceeding 2000 mSv, or 2 000 000 μSv/y, are used to treat cancer. If a person were to spend hours exposed to such radiation, death would be very likely.
Thus, nuclear materials pose a health risk, especially when they are in close proximity for long periods of time.
Click on the adjacent graphs to see full screen.
