Nuclear weapon

• 1. Introduction

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  Nuclear weapons are explosive devices capable of destroying a city with a yield measured in the low kilotons of TNT. Nine sovereign states are believed to possess them today: the United States, Russia, the United Kingdom, France, China, India, Pakistan, North Korea, and Israel. The global stockpile once exceeded 64,000 warheads before falling to around 9,600. Nuclear weapons have been used in combat exactly twice, both times in 1945, killing between 150,000 and 246,000 people in two Japanese cities in the span of three days. The questions the rest of this documentary will answer are deceptively simple: how do these weapons work, what strategies have grown up around them, and why, decades after the Cold War ended, do they remain one of the defining dangers of human civilization?

• 2. How the Bomb Works

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  On the 6th of August 1945, the United States Army Air Forces detonated a uranium gun-type fission bomb nicknamed "Little Boy" over Hiroshima. The physics behind it was stark: a mass of fissile material forced into supercriticality triggers an exponential chain reaction. Fission weapons use one of two methods to achieve this. The "gun" method fires one sub-critical piece of material into another. The "implosion" method uses chemically fueled explosive lenses to compress a sphere of fissile material, and is smaller, lighter, and requires less of the expensive fuel. The most commonly used fissile materials have been uranium-235 and plutonium-239. Fission bombs can release energy ranging from the equivalent of just under a ton to upwards of 500,000 tons of TNT. What they cannot do easily is grow larger without running into criticality danger, meaning a premature chain reaction from too much pre-assembled fissile material.

  Thermonuclear weapons solve that problem. In the Teller-Ulam design, a fission bomb serves as a "primary" that compresses and heats fusion fuel in a separate "secondary" stage. The gamma rays and X-rays emitted first compress the fusion fuel, then heat it to thermonuclear temperatures. The resulting fusion reactions produce enormous numbers of high-speed neutrons that can fission materials not normally prone to it, including depleted uranium. In large, megaton-range hydrogen bombs, roughly half of the total yield comes from this final fissioning of depleted uranium. Because additional fusion stages can each ignite a larger amount of fuel in the next, thermonuclear weapons can in principle be built to arbitrarily large yields. The largest ever detonated, the Soviet Tsar Bomba, was a three-stage weapon that released the energy equivalent of more than 50 megatons of TNT. Early planners at the Livermore Laboratory in the United States once drew up designs for two even larger tests, named Gnomon and Sundial, with projected yields of 1 gigaton and 10 gigatons of TNT respectively, though neither was built.

• 3. Getting It There

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  Delivery systems account for 57% of all financial resources the United States spent on nuclear weapons projects since 1940. The simplest method is a gravity bomb dropped from an aircraft, which is what the United States used against Japan in 1945. The majority of US nuclear warheads are free-fall gravity bombs, a design still being refined today in the form of the B61. Aircraft delivery limits attack range, response time, and the number of weapons a country can field simultaneously.

  Missiles changed the calculation. Intercontinental ballistic missiles and submarine-launched ballistic missiles gave nations the ability to deliver warheads anywhere on the globe. Multiple independently targetable reentry vehicles, or MIRVs, allow a single missile to release warheads aimed at separate targets, multiplying the challenge for any missile defense system. Together, land-based missiles, submarine-launched missiles, and nuclear strategic bombers form what strategists call the nuclear triad. Tactical weapons took the widest variety of forms: artillery shells, land mines, depth charges, torpedoes, and the Special Atomic Demolition Munition, a man-portable or truck-portable device of one or two kilotons suitable for destroying bridges, dams, or tunnels. The USAF also deployed nuclear-armed antiaircraft weapons including the AIR-2 Genie, the AIM-26 Falcon, and the Army's Nike Hercules.

• 4. Strategy and Deterrence

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  Nuclear deterrence rests on a simple and terrifying logic: the threat of unacceptable retaliation is supposed to prevent a first strike. Maintaining a credible second-strike capability, meaning the ability to absorb a nuclear attack and still respond, is the core requirement. During the Cold War, game theorists and military planners built elaborate models to identify stable deterrence conditions. Gen. Pierre Marie Gallois of France, an adviser to Charles de Gaulle, argued in his 1961 book The Balance of Terror: Strategy for the Nuclear Age that mere possession of a nuclear arsenal was sufficient to ensure deterrence, and that the spread of nuclear weapons might even increase international stability.

  Scholars such as Kenneth Waltz and John Mearsheimer have extended that argument, suggesting that nuclear weapons helped prevent the large-scale conventional wars that were common before their invention, and that selective proliferation in troubled regions might reduce the risk of total war. Critics of that view counter that the threat of nuclear terrorism complicates deterrence fundamentally. Robert Gallucci proposed what he called "expanded deterrence," holding the states that might transfer or leak weapons to terrorist groups accountable for any resulting use. Graham Allison argued that nuclear forensics, identifying the unique impurities and contaminants of fissile material after a detonation, could trace a bomb back to its origin country, creating accountability even after the fact. In 1996, the International Court of Justice issued an advisory opinion that the use or threat of use of nuclear weapons would generally violate international law, including the Geneva Conventions, the Hague Conventions, the UN Charter, and the Universal Declaration of Human Rights, though the court did not reach a conclusion about extreme circumstances involving state survival.

• 5. Accidents and Near Misses

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  On the 21st of August 1945, physicist Harry Daghlian received a lethal dose of radiation at Los Alamos National Laboratory when an error during experiments on a plutonium-gallium core caused it to enter prompt criticality. He died 25 days later. The following May, physicist Louis Slotin accidentally caused the same core to become briefly supercritical while conducting further experiments; he died nine days later. That core became known as the "demon core."

  The record of accidents since then is long. On the 13th of February 1950, a Convair B-36B became the first aircraft to lose a nuclear weapon when it crashed in northern British Columbia after jettisoning a Mark IV atomic bomb. On the 22nd of May 1957, a 42,000-pound Mark-17 hydrogen bomb fell from a bomber near Albuquerque, New Mexico; the detonation of its conventional explosives created a crater 25 feet in diameter on land owned by the University of New Mexico. On the 24th of January 1961, a Boeing B-52 carrying two Mark 39 nuclear bombs broke up in mid-air near Goldsboro, North Carolina, and one of the weapons passed through every stage of its firing sequence except one safety switch. On the 17th of January 1966, a B-52G collided with a KC-135 tanker over Spain; three of the four hydrogen bombs it carried were found on land near Almeria, where the non-nuclear explosives in two of them detonated and contaminated a 2 square kilometer area with radioactive plutonium. The fourth was recovered from the Mediterranean Sea after a two-month search. Experts believe that up to 50 nuclear weapons were lost during the Cold War. General George Lee Butler, commander of the US Strategic Air Command from 1991 to 1992, concluded in 1999 that the Cold War had been survived through "some combination of skill, luck, and divine intervention, and I suspect the latter in greatest proportion."

• 6. Arms Control and Disarmament

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  The Russell-Einstein Manifesto was issued in London on the 9th of July 1955, signed by eleven scientists and intellectuals including Albert Einstein, who had signed it just days before his death on the 18th of April 1955. It called on world leaders to seek peaceful resolutions to conflict in the face of nuclear danger. A few days after its release, philanthropist Cyrus S. Eaton offered to sponsor a conference in Pugwash, Nova Scotia, his birthplace. The first Pugwash Conference on Science and World Affairs was held in July 1957.

  The treaty architecture that followed took decades to build. The 1963 Partial Nuclear Test Ban Treaty restricted all nuclear testing to underground sites. The 1968 Treaty on the Non-Proliferation of Nuclear Weapons required signatories to pursue disarmament in good faith, though nuclear-weapon states have largely treated that obligation as, in the words of observers, "decorative" and without force. The International Atomic Energy Agency was established in 1957 under a United Nations mandate to encourage peaceful nuclear applications and provide international safeguards. The 1996 Comprehensive Nuclear-Test-Ban Treaty, signed by many nations, still awaits ratification by eight of the 44 specific states required for it to enter into force. South Africa remains the only country to have independently developed and then fully renounced nuclear weapons. The Doomsday Clock, published annually by the Bulletin of the Atomic Scientists, was set to 89 seconds to midnight in 2025, reflecting the continuing escalation of nuclear tensions, particularly around the war in Ukraine.

• 7. Public Opposition and Fallout

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  Radioactive fallout first entered broad public awareness in 1954 when the Castle Bravo hydrogen bomb test at the Pacific Proving Grounds contaminated the crew and catch of the Japanese fishing boat Lucky Dragon. One of the fishermen died in Japan seven months later. Fear of contaminated tuna led to a temporary boycott of the popular staple across Japan, and the incident provided, as historians have noted, a decisive impetus for anti-nuclear weapons movements in many countries.

  Peace movements had already emerged in Japan, and in 1954 they merged into a unified Japan Council against Atomic and Hydrogen Bombs. Approximately 35 million signatures were collected on petitions calling for bans on nuclear weapons. In the United Kingdom, the Campaign for Nuclear Disarmament organized Aldermaston Marches beginning at Easter 1958, when several thousand people marched for four days from Trafalgar Square in London to the Atomic Weapons Research Establishment near Aldermaston in Berkshire. By the late 1960s, tens of thousands were taking part. In 1962, Linus Pauling won the Nobel Peace Prize for his work to stop atmospheric testing. A Centers for Disease Control and Prevention and National Cancer Institute study estimated that fallout from atmospheric nuclear tests would lead to perhaps 11,000 excess cancer deaths among people alive during atmospheric testing in the United States from 1951 well into the 21st century. Since the Radiation Exposure Compensation Act of 1990, more than 1.38 billion dollars in compensation has been approved to people exposed at sites including the Nevada Test Site.