Radiation.1.1. Radiation Dose. 1.2. Type of Radiation. 1.3. The Amount of Pollution. 1.4. The form of Dispersion of the Release. 2. Use of Radiation in Society. 3. Radioactivity in the Ocean. 4. Pollution and Chemical Compounds.4.1. Plutonium and the Environment. 5. Remedial Action.
Radiation, both natural background and man-made, forms a part of our environment which must be considered as both a benefit and a risk. In order to judge radiation a number of things must be taken into account, such as:
When a situation occurs with radioactive pollution, it is important to get accurate information about the radiation doses that are involved. It would be a waste of resources to immediately implement countermeasures if the doses involved are smaller than the variations in natural background radiation.
To date no general agreements have been reached with regard to the dose levels where actions should be taken. For example, in the case of radon, the recommendations from WHO (World Health Organization) are that 800 Bq/m3 should be considered as an action level. The equivalent dose involved would be approximately 20 mSv per year.
Type of radiation
In order to perform dose calculations and estimate health risks, it is important to have information on the radiation source (e.g., the isotopes involved). As pointed out in previous chapters, there is a clear distinction between γ-emitting isotopes and those which emit α- and β-particles.
1.3. The amount of pollution
The amount of radioactive material released to the environment should be given in Bq (or in Ci) and not in volume or weight since a large release in weight may contain small amounts of radioactivity and vice versa.
In the example of the Chernobyl accident a large fallout of Cs-137 resulted, both to areas around the reactor as well as far away. In Scandinavia, areas were found with fallout of 100 kBq/m2. However, the total release of Cs-137 was in fact only a few kilograms. Here, a small amount of material produced an easily measurable amount of radioactivity at a great distance from the accident.
1.4. The form and dispersion of the release
It is important to have information on the form of the release; whether it is in the solid state, liquid state, or gaseous state. It is also important to know the dispersion or scatter characteristics in some detail in order to localize so-called "hot" areas. Consider two examples which demonstrate the differences with regard to transport and dispersion of radioactivity:
• The Chernobyl accident
This accident caused a large release of radioactivity that reached a height of several thousand meters and was then transported by the wind systems. The fallout was mainly determined by precipitation in the areas where the radioactive "cloud" passed by. After fallout, the different radioactive isotopes still have possibilities for further dispersion via the water systems and plant uptake. This means that the isotopes reached the food chain and gave a large segment of the population an extra dose.
• The submarine Komsomolets
In 1989, the Russian submarine Komsomolets was sunk in the North Atlantic to a depth of 1,680 meters. It contained a reactor, fission products, and nuclear war heads. The dispersion of radioactivity from this accident is so far not measurable and extra doses to the public are almost nonexistent. Because plutonium is not dissolved easily in water, even as it is released in the future, its dispersion will be very small.
Use of Radiation in Society
Human activities include the use of radiation. Some of these activities may involve a high probability for pollution. If the risk is high, the activity should be stopped. Again, the benefits must be compared with the risks.
Most people would agree that radioactive isotopes used in medical diagnoses and research involve minor pollution problems. However, the large radioactive sources used in therapy and in other activities have resulted in some radiation accidents with fatal outcomes. It is, therefore, necessary to train workers and to implement proper safety routines. This is particularly true within the nuclear power industry where the use of uranium involves risks for the release of radioactive isotopes from the mining of the ore to the final disposal of the waste. Under normal operating conditions, only negligible amounts of radioactivity are released from a power reactor. The public has concerns with waste disposal and the relatively low risk of accidents.