Serious levels of radioactive fallout after a nuclear accident are very difficult to mitigate. In most cases we’ve experienced the most contaminated sites are uninhabitable,or represent regions into which we may go only for brief periods. The location is not stable and weathering can both alter the distribution of radioactivity within the region or expand its size. Clean up is then often made more difficult by the fact that distribution of radioactive substances with the site is constantly changing.
Radioactivity often falls on and contaminates both drinking water in reserviors as well as on land where crops have been cultivated. In time, rainfall will disperse the fallen radioactive substances from plants and above-ground plants or even animals where radioactive substances may have initially landed. In those places radioactivity will decline while in lower areas of soil radioactivity will increase and will often begin to sink further and further into the soil. Thus any clean up plans needs to take stock of the fact that the target is moving.
Gradually on land radioactivity migrates to both plants and animals. Within streams a drivers often falls easily into lower aquatic organisms. In time, radioactive materials move up through the food chain and accumulates into edible fish. In general, massive fallout can only go from bad to worse. Workers can be modestly protected from radioactive substances emitting alpha or beta particles and x-rays. Gamma-ray and neutron emitting radionuclides are more dangerous from the outset.
Plants readily take up metals from the soil including common radioactive metal elements. This takes radioactivity from the soil and lodges it within the plant. In time, the plant will decay and radioactive salts dissolved by rain and renter the soil. Alternatively. In dry weather, the radioactive salts will be dispersed by the winds.
Actual concentration of radioactive substances by plants offers the possibility of mitigating the soil’s radioactive contamination. Until or unless this can be accomplished or the ground relieved of its radioactive materials in other ways, it will likely not be safe to reestablish residence there and especially not wise to plant edible crop into which radioactive salts will concentrate and consumed by people.
Both the Russian and American experiences are important in gaining insight into decontamination and decommissioning of radioactive fallout sites. Both countries have 50-plus years of experience. The Russian program has taken on increased emphasis since 1996, and will likely increase further in the future. Increasing death rates due to accumulating serious radioactive contamination may begin to make sizable contribution to declining human populations through both increased cancer rates as well as death due to decreased immunity in the general population. This can be seen in particular in the population decline both Bellarus and the Ukraine as well as in western Russia, due in the latter case to years of contamination at Mayak as well as to the problems generated in portions of Sooth Western Russia near the Bellarus and Ukraine borders after the explosion and fires at Chernobuyl.
Fukushima represents as entirely different level of contamination so far, one which could become much more serious if additional seismic events claim the day over the next 40 years as decontamination and decommissioning at the site continues.