History: "Megaton" Class Fission Bombs (1940s/1950s)

Discussion in 'History After 1900' started by Delta Force, Sep 12, 2017.

  1. Delta Force

    Delta Force Administrator
    Staff Member Administrator

    Mar 9, 2017
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    The United Kingdom pursued a fission approach in the 1950s due to difficulties developing thermonuclear bomb technology. The British found several problems with pure fission devices and moved to thermonuclear designs as soon as possible. Those are weight, inefficient materials usage, safety and readiness concerns due to the large number of critical masses in a single core and the safeguards that must be employed to prevent a criticality accident or even a nuclear fizzle partial detonation.

    The Orange Herald boosted fission device achieved worse performance than the unboosted Mark 18 Super Oralloy Bomb. The Orange Herald design used 117 kilograms of highly enriched uranium for 740 kilotons yield (about 6 kilotons per kilogram HEU) while the Mark 18 used 60 kilograms for 500 kilotons (8 kilotons per kilogram HEU). This is a significant amount of material, the Orange Herald test consumed almost all of the United Kingdom's annual production of 120 kilograms HEU. To put that in perspective, a critical mass of uranium 233 is only 15 kilograms.

    There were safety issues with large fission designs because the large amount of material involved increased the risk of accidentally assembling a critical mass. The British designed a smaller fission device, Green Grass, for deployment, but it was inefficient and unsafe:

    The United States had similar concerns about the Mark 18, and they were in fact rebuilt to the Mark 6 configuration once thermonuclear bombs started entering service:

    It's also thought that the pressure to produce materials for Orange Herald and other boosted fission designs led to the use of improper fuel elements that led to the Windscale Fire:


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