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City scenario

London nuclear blast radius

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This scenario puts a 15 kt airburst on Westminster so the rings read against the Thames, the parks, and the central boroughs. Greater London is much larger than a Hiroshima-scale disk.

Open London in the 3D simulator

Educational estimate only. Blast and heat rings use simplified yield scaling. They ignore terrain, weather, shielding, and weapon design. Casualty counts use WorldPop 2020 residents on an approximately 1 km grid and ignore time of day, commuting, shelter, and evacuation. This is not a targeting or civil-defense tool. About the model.

Aim point: Westminster / Whitehall core · Weapon: Little Boy (15 kt, 543 m (1,780 ft) optimum airburst)

Ground ranges for Little Boy (15 kt, 543 m (1,780 ft) optimum airburst) in this simulator.
Effect Ground range What the model means
Fireball 266 m (872 ft) Maximum luminous radius
20 psi 839 m (2,751 ft) Heavy destruction
5 psi 1.8 km (1.1 mi) Most buildings collapse
Thermal 2.0 km (1.3 mi) 3rd-degree burns
1 psi 4.2 km (2.6 mi) Windows shatter
Rings scaled to 1 psi. Yellow fireball, red 20 psi, orange 5 psi, gold thermal, blue 1 psi. Not a map of buildings.

Casualty estimate at this pin

People on the WorldPop 2020 grid inside this scenario’s 1 psi ring. Rounded educational estimate, not a forecast.
Estimated deaths 45,408
Estimated injuries 172,871
Residents inside 1 psi 629,284

What the rings cover

Fireball and 20 psi stay in the Westminster core. 5 psi and thermal reach across a slice of central London and the river. 1 psi covers several inner boroughs and still leaves most of Greater London outside window-breakage.

The pin is in the government and river core, not in Croydon or a Heathrow centroid. That matches the other capital-city pages: a place a visitor can name, with a populated WorldPop cell.

London’s parks and the river make 2D circles misleading. In 3D you can see that a kilometre of 5 psi is the distance from Whitehall to parts of the South Bank or the edge of the West End — not ‘all of London.’

Civil-defense history in Britain is real; this page is not that archive. It is an indexable view of the same educational model used on New York and Paris.

Related pages

Paris · New York · Tokyo · Hiroshima

All cities and sites

City index · Historic sites · Weapon yields

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