Radiation is all around us. In, around, and above the world we live in. It is a natural energy force that surrounds us, and it is a part of our natural world that has been here since the birth of our planet. From the beginning of time, all living creatures have been, and are still being, exposed to ionizing radiation. Ionizing radiation is generated through nuclear reactions, nuclear decay, very high temperature, or acceleration of charged particles in electromagnetic fields.
Radiation Exposures from Coal Cycle
The public is also exposed to radiation from so-called “enhanced sources of naturally occurring radioactive material.” This also means industries such as metal mining, coal mining, and coal power production from coal create additional exposures due to the densification of naturally occurring radionuclides. Coal is the predominant source of energy used to produce electricity today. The coal cycle is a process chain consisting of various stages. For the coal cycle, the life cycle includes:
- coal mining,
- power plant operation,
- coal ash deposits.
According to the UNSCEAR, power generation from coal and the entire coal cycle contribute more than half of the total radiation dose to the global population from electricity generation. This statement will seem paradoxical to many readers since it’s not commonly known that non-nuclear energy sources release any radiation into the environment. But power generation from coal also creates additional exposure to the public. Even the nuclear fuel cycle releases less radiation into the environment than the coal cycle and any other major energy source.
The problem is coal itself and especially coal ash (fly ash). Coal, a combustible black or brownish-black sedimentary rock, contains a substantial amount of the radioactive elements uranium and thorium. According to the UNSCEAR, the average specific activity of both uranium-238 and thorium-232 in coal is generally around 20 Bq/kg (range 5-300 Bq/kg). Coal mines in Freital, Germany, which have uranium concentrations of 15000 Bq/kg coal, are an exception. Burning coal gasifies its organic materials, concentrating its inorganic components into the remaining waste, called fly ash. Around 10% of coal is fly ash. Fly ash is hazardous and toxic to human beings and some other living things. Fly ash also contains the radioactive elements uranium and thorium, concentrated by a factor of 10. It must be emphasized that even fly ash does not possess any health hazards to the public. There are a few restrictions on the use of fly ash in landfills and road construction. Most restrictions are on the use in building construction, which can result in increased exposure, especially from radon. In any case, we don’t want to cause any irrational fear of radiation from coal. It does not mean that it must be dangerous. In the case of radiation from electricity generation, the doses are usually very, very low. Moreover, these results cannot be used to determine whether one form of energy generation is preferable to another.
The collective dose, which results from the coal cycle, is:
- 670-1400 man Sv for coal cycle, depending on the age of the power plant,
When considering the amount of electricity generated in 2010 by each technology, the coal cycle resulted in the largest collective dose to the global public and workers combined, followed by the nuclear fuel cycle. Of the remaining technologies, geothermal energy and combustion of natural gas were the next largest contributors.
The normalized collective dose (per gigawatt and year) is:
- 0.7 – 1.4 man Sv/GW.a (man sievert per gigawatt year) for coal cycle
Special Reference: Sources and effects of ionizing radiation, UNSCEAR 2016 – Annex B. New York, 2017. ISBN: 978-92-1-142316-7.
In the following points, we try to express ranges of radiation exposure from electricity generation and doses, which can be obtained from various sources.
- 05 µSv – Sleeping next to someone
- 09 µSv – Living within 30 miles of a nuclear power plant for a year
- 1 µSv – Eating one banana
- 3 µSv – Living within 50 miles of a coal power plant for a year
- 10 µSv – Average daily dose received from natural background
The above doses are related to public exposure. Considering occupational exposure regarding coal mining and fly ash deposits, the collective dose is higher, especially for coal miners. Coal miners as a group receive the largest collective dose of radiation through enhanced exposure to naturally occurring radionuclides.
Note that the collective effective dose is often used to estimate the total health effects, but according to the ICRP, this should be avoided (see more: Collective Dose).