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The environmental and human consequences of nuclear accidents

Environmental consequences
The environmental consequences of nuclear accidents are difficult to assess. In most cases, the state of biodiversity before an accident is not well known, which means that there is no baseline from which to measure change. After a nuclear accident, the human population is evacuated, but the animals and vegetation remain. The soil and all edible plants growing in it are contaminated for many years. The only serious accident that occurred long enough ago to offer some perspective is the 1986 Chernobyl disaster in the Soviet Union (now Ukraine). Recent studies have revealed that the site is now home to a rich but in some ways unusual biodiversity. Animal species thrive in the area, partly because they have no fear of hunters for lack of human presence in the exclusion zone! The forest in this “no man’s land,” spanning a 30-km radius around the plant, was renamed the “red forest” after the color of the trees, which were severely burned by radiation. Starting in 1987, the Soviet authorities excavated some 900 trenches to bury contaminated plant matter and highly radioactive waste from the ravaged plant under a thin layer of clean sand.
In the past decade, Ukrainian researchers, backed by teams from the CEA, IRSN and CNRS, have observed that in one of the trenches, number T22, some nucleotides (cesium-137, strontium-90 and plutonium) are migrating faster than expected given the site’s physico-chemical characteristics. A microbiological investigation revealed that the phenomenon is probably partly due to bacteria in the soil, some species of which trap radionuclides on their surface (biosorption), while others incorporate them (bioaccumulation). These mechanisms make it possible to immobilize the radioactivity or, through cellular migration, to propagate it.
Microbiological analyses of this type should shed light on the migration of radionuclides in the environment.

Human consequences
In the case of a serious accident at a nuclear power plant, the authorities evacuate the neighboring populations to avoid potential exposure to the highly radioactive substances that could be emitted and carried by the air, also contaminating the soil and water. Penetrating the body through breathing, an open wound or the ingestion of contaminated food or water, these particles settle in certain organs, resulting in internal irradiation. For example, radioactive iodine settles in the thyroid and cesium-137 in the muscles and the heart. If exposure to radiation is especially intense or of long duration, the accumulation of radioelements in the cells is likely to cause cancer. Nonetheless, it remains difficult to evaluate the precise impact of a nuclear accident on the health of local populations. A 2005 UN-sponsored report on the Chernobyl disaster by the World Health Organization (WHO) and the International Atomic Energy Agency (IAEA) evaluated the number of immediate deaths caused by the accident at fewer than 50, plus 2,200 premature deaths due to radioactivity among the 200,000 most exposed “liquidators” (cleanup personnel). In addition, records show about 4,000 diagnoses of thyroid cancer that can be attributed to the Chernobyl accident among children and teenagers aged below 18 in 1986. Thyroid cancer is rare in that age range and it is safe to presume that these cases were induced by exposure to the radioactive iodine released in the first few days after the accident. However, these figures are the subject of much controversy among the international scientific community and it is difficult, more than 20 years on, to have a reliable estimate of the number of victims of this catastrophe. Nuclear accidents can also have severe psycho-sociological consequences for the affected human populations, including stress, which can lead to suicide, displaced families losing everything overnight and the fear of contamination. After Chernobyl, many pregnant women in the area had abortions for fear of giving birth to deformed babies.