December 11, 2015

North Korea claims to have a nuclear fusion hydrogen bomb

Kim Jong-un has stated North Korea has powerful hydrogen bombs, the first time it has been suggested North Korea has such a device. First tested in 1952, hydrogen bombs are more dangerous—and complicated—than atomic bombs. Experts are skeptical of the North Korean claim.

According to the North Korean state news agency KNCA, Kim made the comments at the Phyongchon Revolutionary Site, a former munitions factory. Kim stated that North Korea was, "a powerful nuclear weapons state ready to detonate self-reliant A-bomb and H-bomb to reliably defend its sovereignty and the dignity of the nation."

No further details on the North Korean H-bomb were provided. North Korea is known to have a nuclear arsenal, and is believed to have tested nuclear devices three times in the past.

Thermonuclear weapons or H bombs

A thermonuclear weapon is a nuclear weapon that uses the energy from a primary nuclear fission reaction to compress and ignite a secondary nuclear fusion reaction. The result is greatly increased explosive power when compared to single-stage fission weapons. It is colloquially referred to as a hydrogen bomb or H-bomb because it employs hydrogen fusion. The fission stage in such weapons is required to cause the fusion that occurs in thermonuclear weapon.

The concept of the thermonuclear weapon was first developed and used in 1952 and has since been employed by most of the world's nuclear weapons. The modern design of all thermonuclear weapons in the United States is known as the Teller-Ulam configuration for its two chief contributors, Edward Teller and Stanislaw Ulam, who developed it in 1951.

A simplified summary is:

1. An implosion assembly type of fission bomb is exploded. This is the primary stage. If a small amount of deuterium/tritium gas is placed inside the primary's core, it will be compressed during the explosion and a nuclear fusion reaction will occur; the released neutrons from this fusion reaction will induce further fission in the plutonium-239 or uranium-235 used in the primary stage. The use of fusion fuel to enhance the efficiency of a fission reaction is called boosting. Without boosting, a large portion of the fissile material will remain unreacted; the Little Boy and Fat Man bombs had an efficiency of only 1.4% and 17%, respectively, because they were unboosted.

2. Energy released in the primary stage is transferred to the secondary (or fusion) stage. The exact mechanism whereby this happens is secret. This energy compresses the fusion fuel and sparkplug; the compressed sparkplug becomes critical and undergoes a fission chain reaction, further heating the compressed fusion fuel to a high enough temperature to induce fusion, and also supplying neutrons that react with lithium to create tritium for fusion.

3. The fusion fuel of the secondary stage may be surrounded by depleted uranium or natural uranium, whose U-238 is not fissile and cannot sustain a chain reaction, but which is fissionable when bombarded by the high-energy neutrons released by fusion in the secondary stage. This process provides considerable energy yield (as much as half of the total yield in large devices), but is not considered a tertiary "stage". Tertiary stages are further fusion stages (see below), which have been only rarely used, and then only in the most powerful bombs ever made.

Thermonuclear weapons may or may not use a boosted primary stage, use different types of fusion fuel, and may surround the fusion fuel with beryllium (or another neutron reflecting material) instead of depleted uranium to prevent early premature fission from occurring before the secondary is optimally compressed.

Compression of the secondary

The basic idea of the Teller–Ulam configuration is that each "stage" would undergo fission or fusion (or both) and release energy, much of which would be transferred to another stage to trigger it. How exactly the energy is "transported" from the primary to the secondary has been the subject of some disagreement in the open press, but is thought to be transmitted through the X-rays which are emitted from the fissioning primary. This energy is then used to compress the secondary. The crucial detail of how the X-rays create the pressure is the main remaining disputed point in the unclassified press. There are three proposed theories:

  1. Radiation pressure exerted by the X-rays. This was the first idea put forth by Howard Morland in the article in The Progressive.
  2. X-rays creating a plasma in the radiation case's filler (a polystyrene or "FOGBANK" plastic foam). This was a second idea put forward by Chuck Hansen and later by Howard Morland.
  3. Tamper/Pusher ablation. This is the concept best supported by physical analysis

The basics of the Teller–Ulam design for a thermonuclear weapon. Radiation from a primary fission bomb compresses a secondary section containing both fission and fusion fuel. The compressed secondary is heated from within by a second fission explosion.

Foam plasma pressure

Foam plasma pressure is the concept which Chuck Hansen introduced during the Progressive case, based on research which located declassified documents listing special foams as liner components within the radiation case of thermonuclear weapons.

SOURCES - Wikipedia, Youtube, Popular Mechanics

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