How does nuclear fallout affect the environment?

A detonated nuclear bomb produces a fireball, shock waves and intense radiation. A mushroom cloud forms from vaporized waste and scatters radioactive particles that fall to the ground and contaminate the air, soil, water and food supply.

How does nuclear fallout affect the environment?

A detonated nuclear bomb produces a fireball, shock waves and intense radiation. A mushroom cloud forms from vaporized waste and scatters radioactive particles that fall to the ground and contaminate the air, soil, water and food supply. When carried by wind currents, rains can cause far-reaching environmental damage. Above-ground detonation of nuclear weapons sends radioactive materials up to 50 miles into the atmosphere.

Large particles fall to the ground near the explosion site, but lighter particles and gases move to the upper atmosphere. Particles that are dragged into the atmosphere and fall back to Earth are called rain. Rain can circulate around the world for years until it gradually falls to Earth or is brought back to the surface by precipitation. The trajectory of rain depends on wind and weather patterns.

And while the world would cool down, the nuclear winter resulting from a full-fledged global conflict (or even the “nuclear fall”, as some researchers prefer) would not reverse the effect of what we might morbidly call “traditional man-made climate change.”. In the short term, the effects of ocean acidification would worsen, not improve. The smoke layer in the atmosphere would destroy up to 75 percent of the ozone layer. That means that more UV radiation would slide through the planet's atmosphere, causing a pandemic of skin cancer and other medical problems.

It would affect not just humans, or even the most remote islands, as higher UV rates would endanger plants and animals that would otherwise not be affected by global slaughter. The health effects of nuclear explosions are mainly due to air explosion, thermal radiation, initial nuclear radiation and residual nuclear radiation or rain. Compared to deaths from rapid cancer, from acute and latent side effects, the absolute number of effects on the fetus is small and captured within the limits of uncertainty. The number of eye cataracts, according to the experience of Chernobyl workers, is not small.

The occurrence of ocular cataracts in the now aging Japanese population is several tens of percent among the most exposed. The area over which casualties would occur as a result of the various weapon effects described above depends mainly on the explosive performance of the weapon and the height or depth of the explosion. The areas affected by the initial nuclear radiation and rain also depend on the design of the weapon (in particular, the fraction of the performance that is derived from fission reactions) and, in the case of rain, on the weather conditions during and after the explosion (in particular, the speed and direction of the wind, the atmosphere stability, precipitation, etc.), terrain and geology in the area of the explosion. The following calculations assume that the entire population is static and open.

By way of illustrative example, Figure 6.1 shows the área where an outdoor individual would face a 10, 50, and 90 percent chance of dying or serious injury8 from the immediate effects of a 10-kiloton earth penetrating weapon (EPW) detonated at a depth of 3 meters and from the immediate effects of a 250 kiloton. kiloton surface explosion. As discussed in Chapter 5, both weapons would produce a ground shock of approximately 1 kilobar at a depth of 70 meters. Figure 6.2 is similar, but also includes the probability of death or serious injury from acute exposure to external gamma radiation from rain, for illustrative weather conditions, hypothetically assuming that 50 percent of the weapon's performance is derived from fission and that a static population is outdoors.

Figure 6.3 compares the number of victims (deaths and serious injuries) due to the rapid and acute effects of the consequences arising from the use of both weapons. Under these conditions and assumptions, the 10-kiloton EPW is estimated to result in around 100,000 victims, compared to 800,000 casualties for the In each case, the committee asked the DTRA to estimate the average number of victims (deaths and serious injuries from immediate effects, and acute effects from gamma radiation consequences). external) as a result of attacks with earth-penetrating weapons with yields ranging from 1 kiloton to 1 megaton, for fully outdoor and completely indoor populations. Averages are averages over annual wind patterns, but ignore rainfall.

The DTRA also estimated the average number of casualties resulting from surface explosions with yields of 25 kilotons to 7.5 megatons. For selected cases, the committee asked Lawrence Livermore National Laboratory to estimate the number of deaths from immediate effects and consequences, and to quantify the variability in acute and latent deaths from rainfall caused by wind patterns. Figure 6.7 shows the contributions of immediate effects and acute radiation sickness and death from rain to the victim estimates for EPWs. The number of victims is similar for surface explosions of the same performance.

This is particularly true for Goals B and C, for which rain is the only effect of low-performing explosions that can reach population centers. As mentioned, the results shown in Figures 6.1 to 6.7 assume that the entire population is static and open. Assuming that the entire population remains indoors and is therefore protected from radiation, mean total casualties are reduced by a factor of up to 4 for Objective A, and by a factor of 2 to 8 for Objectives B and C. The movement or evacuation of the population after the attack is not taken into account, but it is unlikely that people will be able, by fleeing the area of an attack, to reduce their exposure to rain significantly more than if they remain indoors.

In fact, some people could greatly increase their exposure to rain if they moved through highly polluted areas, as could happen if a major road leaving the city were directly under the cloud path. Therefore, in a population that has not received any warning of an attack, the real effects of shelter and evacuation are likely to be between the two extremes for a population that is supposed to be entirely indoors and one that is supposed to be completely outdoors. The results given in Figures 6, 6 to 6, 8 are averages over annual wind patterns. Rain casualties can be substantially higher or lower, depending on the particular wind conditions during and immediately after the attack.

Figures 6, 9 (a) and (b) show the variation in the number of deaths due to the acute and latent effects of rain from an EPW of 300 kilotons on objectives A and B, respectively, as a function of wind direction. For Objective A, estimated deaths from fallout vary by more than an order of magnitude depending on wind direction, ranging from 90,000 to 800,000 for acute and rain effects; 50,000 to 160,000 for deaths from latent rain effects; and 60,000 to 900,000 for total deaths. For Target B, the corresponding ranges are 9,000 to 40,000 for deaths due to acute effects of rain; 10,000 to 60,000 for deaths due to latent effects of rain; and 20,000 to 90,000 for total deaths. Model runs show significant deaths from both an EPW and an explosive weapon on the surface.

The figures are higher when the attack occurs near a population center and if a wind is introduced in the calculations that could blow the consequences on the population center. Figures 6, 11 (a) and (b) show that, for a given wind direction, the estimated number of fatalities is significantly lower for the lower performing EPW. However, it's also worth noting that in unfavorable winds, the lower-performing EPW would cause nearly as many deaths as would the higher-performing surface that would burst in favorable winds. For example, 40,000 deaths are the result of attacks on Objective A of 10 kilotons (EPW) with the wind blowing from the west and the 250 kiloton surface exploded in the wind blowing from the east.

Similarly, 15,000 deaths are the result of attacks on Objective B of the 10 kiloton EPW with the wind blowing from the southeast and the surface of 250 kilotons exploded with the wind blowing from the northwest. These figures suggest that wind direction may be as important as a 25-fold difference in performance in determining civilian casualties from attacks where rain is the main health hazard. However, Figures 6, 11 (a) and (b) also show that for the same wind direction, with few exceptions, the number of deaths from the surface burst are significantly higher than the number of victims of EPW. These comparisons indicate the sensitivity to wind of collateral damage to populations.

However, an unfavorable wind for an EPW is, of course, also an unfavorable wind for a shallow gust; the same applies to favorable winds. A population center downwind of any of the weapons is an unfavorable situation. As noted above, the estimates produced by the DTRA and LLNL of the number of deaths and injuries due to cadastral rainfall include only the dose of external gamma rays from the deposition of rain particles on soil surfaces, 17 These estimates do not include the external doses of radiation from the passing cloud or internal doses of radiation from inhalation of contaminated air or from ingestion of contaminated food or water. The contribution of these exposure pathways to acute radiation dose is generally not substantial and would not significantly alter the estimates presented above.

However, under some conditions, the contribution of other routes of exposure to the risk of latent cancer could be significant. Here, the contribution of these other exposure routes is reviewed in a semi-quantitative manner. For underground, surface, or near-surface nuclear explosions, radioactive fallout is mixed with a large mass of ejections in the main cloud or in the base wave. These clouds are dense, and most of the mass in In addition to external exposure, individuals may also be exposed to radiation by inhaling rain particles, either during the passage of the cloud or subsequently due to resuspension of deposited particles by wind, plow, vehicle travel, or other surface disturbances.

Based on measured external gamma radiation exposure rates and observed air concentrations downwind from NTS explosions, the whole-body inhalation dose was estimated to have ranged for most organs from 1 to 20 percent of the dose resulting from food intake. contaminated, 19 however, the relative dose to the organs of the gastrointestinal tract by inhalation can be much higher, up to 80 percent of the dose per ingestion. This higher dose is due to the entry, during the passage of clouds, of large particles into the upper respiratory tract, from where the particles are expelled by coughing and swallowed. However, the consumption of food contaminated by the consequences of a nuclear test has proven to be a major problem both in NTS20,21 and in the Semipalatinsk industrial estate, a nuclear test site in the Soviet Union, 22 The nature of this problem was not fully appreciated until about 1963, when weather tests by the United States and the former Soviet Union was ending.

By far the biggest concern has been associated with iodine-131, which has a half-life of 8 days. Due to the combination of several rather unique circumstances, this radionuclide has been the main radionuclide of concern from the point of view of food contamination, both for nuclear weapons testing and for reactor accidents. Nuclear explosions create substantial amounts of 131I activity; this radionuclide is also volatile and does not condense into particles until late, at which time it is associated with the surfaces of precipitation particles, 23 Most of the total surface activity is contained in the smallest particles, so that 131I is normally transported further. Smaller particles are also preferably retained by vegetation 24, from which they are lost with an average retention time of about 10 days.

A dairy cow, if it receives its full share of food from fresh pastures, will consume per day the amount of 131I found in about 50 square meters,25 and will secrete up to 1 percent of that daily intake in a liter of milk, 26 Typically, a human who consumes milk will concentrate 30 percent of its intake in the gland thyroid. The thyroid is a very small gland, weighing about 20 grams in adults and only about 2 grams in infants. Therefore, iodine is preferentially retained in vegetation, which is efficiently sampled by the cow and rapidly secretes into milk; then, an infant concentrates a large fraction of that iodine in the milk in an extremely small gland, thus producing a relatively large dose. It is important to note that this pathway, the consumption of contaminated food, may be relatively more important to the consequences of nuclear explosion accidents in non-urban areas, in the sense that dairy animals are more likely to be located in rural areas.

There would also be a problem of contaminated milk supplies following contamination of other types of food crops. After milk, the food of most concern is fresh leafy vegetables. These vegetables are efficient in capturing rain and are usually eaten fresh daily during the growing season. This practice provides the opportunity for a direct and rapid route to humans after rain deposition, but, once again, this route can be eliminated by an informed population with adequate infrastructure.

Other types of food crops tend to have less capacity to capture rain or have more indirect and longer routes to reach humans. Longer paths allow both radioactive decay and loss of retained material from crops. Pathways of potential concern include consumption of meat from grazing animals, poultry and eggs. Cereal crops are usually not a cause for concern, unless harvested immediately after rain deposition.

In addition to the health effects mentioned above, a variety of environmental effects can be expected from nuclear explosions close to the ground surface. After the explosion of a nuclear weapon, the rain zone is intensely radioactive. However, as noted above, the rate of external exposure to gamma radiation declines rapidly over time, and denial of land use due to rain is not a major concern in relation to other effects of rainfall. This is clearly different from the situation expected after a major accident in a reactor such as Chernobyl39, due to the much larger releases of long-life L37C.

Denial of water use is expected to be even less of a concern, except in very unusual circumstances, due to the rapid dilution of residual rainfall deposited in surface waters. Significant groundwater contamination is unlikely to occur, except in areas immediately adjacent to the explosion of an earth-penetrating weapon. Although underground facilities could be built below the water table and kept dry by diverting and pumping, it is expected that most facilities will be above the water table. Groundwater in the immediate area of an underground explosion would be contaminated, but the greatest release of radioactivity would come from activated materials spreading over the surface.

It is highly unlikely that a bunker facility will be built in groundwater. Groundwater is likely to be in the rain area. However, the greatest release of radioactivity would be from the activated material that spreads over the surface of the water. Radionuclide transport due to groundwater movement will be difficult to assess with useful certainty, since it is a very site-specific phenomenon.

Experience at the Nevada test site indicates that the movement of radionuclides through groundwater is quite limited, although some radionuclides have been found off-site after many decades. These groundwater effects will be much lower than the effects of explosions, fires and precipitation on the ground. In the past, there were concerns that a large number of nuclear explosions could cause large-scale environmental disturbances, including stratospheric ozone depletion due to nitrogen oxides produced by the fireball and changes in climate due to soot and other aerosols released by cities on fire. These concerns are relevant only with the detonation of thousands of high-performance weapons.

Significant environmental disturbances are not expected to occur beyond the areas directly affected by the immediate effects of one or more nuclear explosions and the consequences that, depending on the amount of soil entrained and the fission fraction of the weapon (s), may persist at dangerous levels for at least a year. Beta lethal skin burns, the leading cause of death from the acute effects of rain in Chernobyl, are not considered. KDFOC does not consider beta-burns in its analysis because burns are not considered a major lethal effect, such as immediate and local consequences. For residual effects, it only takes into account the whole-body gamma brightness of radioactive fallout particles larger than 5 microns.

Beta burns from such rain particles would not be extremely lethal except in areas where gamma radiation would have already been, therefore double counting. HPAC does not include beta-induced injuries; all victims are derived from the effects of gamma radiation. The main problem with beta-lesions is that the material must come into contact with the skin, and HPAC has no means of determining the orientation and posture of exposure of the population's skin, nor the secondary beta-burns that people who touch a surface contaminated with beta particles receive. Secondary beta burns are potentially a problem, but there is no way to determine the victims because the total population is not affected.

If an enemy's nuclear weapons are not safe at one point, it is possible that a conventional attack could cause a nuclear detonation. The Comprehensive Nuclear-Test-Ban Treaty (CTBT) The CTBT is a legally binding global ban on the testing of nuclear explosives. One of the biggest environmental disasters of the nuclear test period was caused by the United States in the North Pacific, this being the case of radioactive contamination following the nuclear test of Castle Bravo on Bikini Atoll, in 1954 (Fig. Nuclear explosions create substantial amounts of 131I activity; this radionuclide is also volatile and does not condense into particles until late, at which point it is associated with the surfaces of precipitating particles.

In addition, after detailed investigations, it was discovered that radioactive contamination is not only due to Soviet nuclear tests, but also to nuclear tests carried out by China in the Tarim Basin. Even though there is still very little rainfall in the environment, it's important to remember that rain can be very dangerous. Based on research by existing and emerging experts, the meeting aimed to take stock of the humanitarian and environmental consequences of the use and testing of nuclear weapons, as well as the factors driving nuclear risk. The average number of fatalities due to the rapid and acute effects of rainfall resulting from nuclear EPW attacks with yields of 3 and 30 kilotons was also estimated.

During the 1950s, when atmospheric nuclear tests were conducted at the Nevada Test Site (NTS), there were a number of sets of exposure rate measurements before, during and after the passage of clouds from a variety of types of nuclear tests. The serious environmental damage caused by these nuclear tests, the most powerful ever conducted in the atmosphere, as well as the general context of global nuclear weapons tests, have created the premises of the first instance of large-scale international cooperation to eliminate nuclear weapons tests. Much of the experience with global consequences was the result of major tests conducted by the United States and the Soviet Union between 1961 and 1963, although the previous larger tests in 1952, 1954, 1956 and 1958 also produced global consequences. Nuclear testing is due to atmospheric nuclear tests conducted at the Nevada test site, especially between 1951 and 1958.Testing of the damage caused by the use and testing of nuclear weapons is taking on renewed importance in a world where the risk of nuclear weapons being used is increasing.

Another site of great importance is Novaya Zemlya, where almost 20% of all nuclear tests of the Soviet Union (130 nuclear tests) were carried out (Fig. . .

Nanette Thrun
Nanette Thrun

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