**Types of Fallout:**
– Atmospheric nuclear weapon tests doubled radioactive C in the Northern Hemisphere.
– Fallout comes in two varieties: carcinogenic material with a long half-life and radioactive dust with a short half-life.
– All nuclear explosions produce fission products, un-fissioned nuclear material, and weapon residues.
– Nuclear fireball not reaching the ground results in limited fallout.
– Amount of fallout can be estimated from weapon design and yield.
**Global Fallout:**
– Fallout particles suspended in the stratosphere can take months or years to settle worldwide.
– Radioactive fallout from nuclear testing increased cancer risk.
– Fallout accumulates on vegetation and can affect human exposure through consumption.
– Intermediate fallout occurs within the first month, while long-term fallout can persist from stratospheric deposition.
– Chernobyl accident led to both intermediate and long-term fallout with widespread contamination.
**Local Fallout:**
– Surface burst detonations produce large amounts of radioactive particles.
– Fallout can contaminate large areas of land and water, causing mutations in wildlife and humans.
– Severe local fallout contamination can extend far beyond blast and thermal effects.
– Wind patterns affect the spread and dilution of fallout.
– Remaining in a radiologically contaminated area exposes individuals to external and internal radiation hazards.
**Factors Affecting Fallout – Location:**
– Location plays a crucial role in the spread and intensity of fallout.
– Wind patterns determine the direction and distance fallout travels.
– Severe local fallout contamination can occur from high yield surface detonations.
– Chemical properties of elements in fallout influence deposition rates.
– Thunderstorms can accelerate fallout deposition through rainout or washout.
**Additional Influences on Fallout:**
– Location of Explosion:
– Air burst produces less fallout than ground burst.
– Fireball touching ground pulls soil into cloud.
– Neutron activation occurs before fallout settles.
– Water surface bursts produce lighter particles.
– Fallout from seawater burst is difficult to remove.
– Underwater Explosions:
– Wet fallout must be immediately removed from ships.
– Sea bottom may become fallout after explosions.
– Base surge phenomenon present in underwater bursts.
– Fallout from underwater bursts can cause beta burns.
– Base surge in subsurface bursts behaves like a fluid.
– Meteorological Influences:
– Winds can carry fallout over large areas.
– Fallout patterns influenced by atmospheric conditions.
– Fallout from nuclear tests can contaminate vast areas.
– Snow and rain accelerate local fallout.
– Special meteorological conditions can lead to heavy contamination.
– Biological Effects:
– Range of biological changes post irradiation.
– Effects vary from rapid death to delayed effects.
– Actual exposure measured in röntgens.
– 1 joule per kilogram equals 1 gray.
– Bone marrow receives lower dose compared to air exposure.
Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes. The amount and spread of fallout is a product of the size of the weapon and the altitude at which it is detonated. Fallout may get entrained with the products of a pyrocumulus cloud and fall as black rain (rain darkened by soot and other particulates, which fell within 30–40 minutes of the atomic bombings of Hiroshima and Nagasaki). This radioactive dust, usually consisting of fission products mixed with bystanding atoms that are neutron-activated by exposure, is a form of radioactive contamination.
