Dangers of new US nuclear weapons programmes

The recent Nuclear Policy Review says that the US will pursue the development of two new types of nuclear weapon - small nuclear weapons and weapons designed to destroy bunkers.

Mini-nukes have long been recognised as particularly dangerous. A US law in 1994 prohibits the development of weapons with a yield of less than 5 kilotons on the grounds that "low-yield nuclear weapons blur the distinction between nuclear and conventional war."

Bunker busting weapons are a problem in two ways:

Firstly, any weapon detonated in this way would result in very large quantities of nuclear fallout. When a nuclear weapon is detonated as an "airburst" there is less fallout. When the fireball of the explosion touches the ground then a large amount of radioactive dust is thrown into the air and dispersed. So the new weapons which are proposed will produce far more fallout than current weapons of an equivalent yield. In theory if a weapon was able to penetrate more than 600 feet underground then the fallout might be contained, however it is not possible for a weapon to burrow to this depth.

Secondly, it is likely that the US will conduct nuclear tests to develop the new weapon. In 1997 they did develop the B61-11 earth penetrating bomb using an existing warhead without any nuclear tests. However the B61-11 has only limited effectiveness. It has been proven to penetrate only 20 feet of dry earth when dropped from 40,000 feet. It is unlikely that any existing warhead design would be able to withstand the shock of impact at the velocities needed to dig further underground. The Nuclear Policy Review hinted at this, suggesting that it might be necessary to carry out nuclear tests to develop new weapons.

More information on this available in a report on Low Yield Earth Penetrating Weapons from the Federation of American Scientists.