The consequences of a nuclear explosion are radioactive particles that fall to Earth. This fallout consists of remnants of weapons, fission products, and irradiated soil. These particles range in size from thousandths of a millimeter to several millimeters. Residual radiation is defined as radiation emitted more than one minute after detonation.
If the fission explosion is an aerial blast, the residual radiation will mainly come from the debris of the weapon. If the explosion occurs on or near the surface, soil, water, and other materials in the vicinity will be sucked upwards by the rising cloud, causing early (local) and late (global) precipitous rainfall. Early precipitation settles on the ground for the first 24 hours; it can contaminate large areas and be an extreme and immediate biological hazard. Delayed precipitated rain, which arrives after the first day, consists of microscopic particles that are dispersed by prevailing winds and are deposited in low concentrations on possible large portions of the Earth's surface.
To illustrate the method of predicting consequences presented here, an increasing nuclear exchange scenario was used, which is consistent with that described in the SCOPE-ENUWAR study (Pittock et al.). For this work, the KDFOC2 computer model (Harvey and Serduke, 197) was used to calculate rain fields for individual gusts, which in turn were used to develop a semi-quantitative model to prepare rough estimates of rainfall areas for typical strategic weapons. After approximately 1 year, nuclear fuel cycle products could make a substantial contribution to total gamma-ray dose precipitation patterns in the United States. After that catastrophe, significant amounts of rainfall were deposited in more than 52,000 square miles (135,000 km2) in Belarus, Scandinavia and elsewhere in Europe.
In the 1950s and 60s, the United States Atomic Energy Commission (ACS) began developing nuclear fallout safety standards for civil nuclear reactors. Although these models are extreme in terms of overlapping rainfall patterns, neither can be taken as a limit calculation of extremes in areas of catarrhal rainfall for specific doses. On Earth in the Northern Hemisphere, the presence of smoke and soot would likely result in less rainfall and a decrease in tropopause; these changes could decrease intermediate time scale (tropospheric) rainfall and, depending on changes in stratospheric circulation, could alter the stratosphere contribution to rain in the Northern Hemisphere. Calculations of local catastrophic rain fields were performed using the KD-FOC2 model and an increasing nuclear exchange scenario.Rain radiation is in the form of alpha, beta, and gamma radiation, and since regular clothing provides protection against alpha and beta radiation, most rain protection measures are concerned with reducing exposure to gamma radiation.
Since the end of World War II (1939-194), the United States, the former Soviet Union, the United Kingdom, France and China have carried out test explosions of nuclear weapons above the ground and have therefore contributed to global consequences. This agreement, which was made possible with the end of the Cold War, greatly diminished the chances of nuclear war and the generation of enormous amounts of rain. ACS regulations against potential consequences of nuclear reactors focused on power plant capacity for maximum credible accident (MCA). Disastrous nuclear accidents such as those at Three Mile Island and Chernobyl have made nuclear reactors much less popular.
For doses received within the first 48 hours, the nuclear weapon's gamma radiation pathway for a high-performance warhead (~1 Mt) dominates the gamma radioactivity of the fuel cycle even if it is assumed that all radioactivity from an attacked nuclear fuel cycle installation dissipates with arm products. There are three very different versions of rain pattern from this test because rain was only measured on a small number of widely spaced Pacific atolls.