US decommissions massive Cold War nuke

Bunker buster busted

The US has begun decommissioning its last B53 bomb, one of the largest thermonuclear devices ever built for its Cold War arsenal.

The 12-foot device entered active service in 1962, and over 300 were built in all, with two variants: the B53-Y1, designed to create lasting fallout, and the relatively clean B52-Y2. The nine-megaton bomb was designed to be dropped from a B52 bomber, whereupon it would fall to the ground by parachute and then ignite shortly after impact, crushing underground command and control facilities by hammering them with a pressure wave, while also devastating the surrounding area.

The B53 bomb prior to decommissioning

Goodbye, big boy

The bomb is being decommissioned in a National Nuclear Security Administration (NNSA) facility in Amarillo, Texas – but very, very carefully, because most of the original designers are dead and plans for the device could be incomplete. A team of 130 engineers, scientists, and technicians is currently removing the explosives designed to ignite its enriched uranium warhead.

"The elimination of the B53 is a significant milestone in our efforts to reduce the number of nuclear weapons and implement President Obama’s nuclear security agenda,” said National Nuclear Security Administration (NNSA) administrator Thomas D'Agostino in a statement. "Today, we're moving beyond the Cold War nuclear weapons complex that built it and toward a 21st century Nuclear Security Enterprise.”

The B53 was scheduled for retirement in the 1980s, but fifty units were held back, and only officially retired in 1997. While this was in part down to arms limitation, the other motivating factor was that the US military had already built its replacement, the B61 Mod 11.

This 700lb weapon has a much smaller yield of up to 340 kilotons, but is designed with a hardened casing to be fired into the ground and penetrate several meters before detonation, increasing its bunker-busting capabilities.

B61 bunker busting nukes

The B61 will replace the B53 – and hopefully never be used

While the B53 may have been one of the largest US bombs, it's a lightweight compared to the then–Soviet Union’s AN602, or Tsar bomb, which is thought to be the largest nuclear device ever exploded. The Tsar had a nominal yield of 100 megatons, later halved, and would have created a 2.3km fireball from its ignition point testing showed.

By contrast, the largest US nuke was the B41, which had a maximum yield of around 25 megatons. However, the advent of reliable intercontinental ballistic missile technology and accurate satellite tracking of targets made such large weapons unnecessary. Smaller, more numerous nukes were considered preferable from a tactical consideration, since they did not have to be delivered by vulnerable bombers and wouldn’t destroy the usefulness of territory by creating too much fallout.

"The dismantlement of the B53 bomb - the oldest weapon in America's arsenal and one of the largest in US history - is a major accomplishment that has made the world safer and for which everyone involved should be proud," said Deputy Secretary of Energy Daniel Poneman. "Safely and securely dismantling surplus weapons is a critical step along the road to achieving President Obama's vision of a world without nuclear weapons." ®

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