Fallout-Rechner: Wohin zieht die Wolke?
Atombombe oder Reaktorunfall: Einschlag wählen, Stärke, dein Ort — die Karte zeigt mit dem echten Wind von jetzt, ob du in der Fallout-Zunge liegst, wann sie ankommt und wie lange du drinnen bleiben musst.
—
How the fallout calculator works
The calculator answers one question: is my place in the fallout plume, when does it arrive, and how long do I have to stay inside? It is based on the standard reference by Glasstone and Dolan, The Effects of Nuclear Weapons (1977), which authorities also use for such estimates.
Bomb: blast, heat and fallout
For a nuclear bomb the calculator first draws the rings around the impact: fireball, total destruction, heavy building damage, burns in the open and shattering windows. Their size grows with the cube root of the yield, so a bomb eight times stronger reaches twice as far. You can choose 100, 300 or 800 kilotons.
The type of burst decides the fallout. In a surface burst soil is vaporised, becomes radioactive and rains down downwind, forming a long, narrow plume. An air burst produces hardly any fallout; there the danger is blast and heat.
Reactor accident
A nuclear power plant has no blast wave. The calculator shows the zones for immediate evacuation, exclusion and iodine tablets, plus the cloud as a fan of about 30 degrees either side of the wind direction. Nearby nuclear power plants are marked as points on the map.
The wind right now
Fallout is carried by the wind aloft, which is usually stronger than at the ground and often veers to the right. The calculator fetches the current wind at the impact site and averages the ground and three levels up to 5.5 kilometres. That gives the direction and length of the plume and the time until it reaches your place.
How long to stay inside
Radiation in fallout decays fast: to a tenth every seven hours, the so-called 7-10 rule. After two days one percent is left. That is why the first 48 hours decide, and why the calculator gives a duration per zone, from two days to two weeks inside. An inner room with a lot of masonry around cuts the dose to about a tenth.
Limits
The result is an approximation. Wind aloft, rain and terrain shift the plume; the uncertainty is a factor of two to three. In an emergency, radio, official measurements and the authorities' instructions take precedence. The calculator stores nothing and needs no sign-up.