The Chemistry of Fusion Bombs

In the previous article, we learned about how nuclear fusion occurs naturally, specifically in stars throughout the universe. Now that we understand the very extreme set of conditions that must be present for fusion to occur, we can shift to the oppositeend of the spectrum: man-made fusion. As we have already learned, the fusion reaction gives off a great amount of energy which can be used for many practical purposes that would benefit our daily lives. Throughout the ages, it seems that it has been humanity’s goal to harness ever increasing power for its own benefit which could also destroy humanity altogether. Whether it is a bomb, or an alternative energy source in the form of a nuclear fusion reactor, those inventors who are able to achieve both are definitely making a great contribution to all mankind as long as humans are seeking peaceful cohabitation at all times.

Let’s start off with the largest nuclear fusion bomb ever detonated. The device officially designated RDS-220, known to its designers as Big Ivan, and nicknamed in the west Tsar Bomba was the largest nuclear weapon ever constructed or detonated. The nickname Tsar Bomba is areference to a famous Russian tradition for making gigantic artifacts for show. The bomb was detonatedin 1961 on Novaya Zemlya islands in Arctic Russia. This three-stage weapon was actually a 100 megaton bomb design, but the uranium fusion stage tamper of the tertiary (and possibly the secondary) stage(s) was replaced by one(s) made of lead. This reduced the yield by 50% by eliminating the fast fissioning of the uranium tamper by the fusion neutrons, and eliminated 97% of the fallout (1.5 megatons of fission, instead of about 51.5 Mt), yet still proved the full yield design. (http://www.tsarbomba.org/)

The result was the “cleanest” weapon ever tested with 97% of the energy coming from fusion reactions. The effect of this bomb at full yield on global fallout would have been tremendous. It would have increased the world’s total fission fallout since the invention of the atomic bomb by 25%. Despite the very substantial burst height of 4,000 m (13,000 ft) the vast fireball reached down to the Earth, and swelled upward to nearly the height of the release plane. The blast pressure below the burst point was 300 PSI, six times the peak pressure experienced at Hiroshima in 1945. The flash of light was so bright that it was visible at a distance of 1,000 kilometers, despite cloudy skies.

As we discussed in the first blog post, there are two types of nuclear fusion reactors that have been developed. They include the magnetic confinement reactor and the inertial confinement reactor. In the late 1940’s it seemed an irresolvable problem to scientists as how to enclose the plasma, since any contact to the reaction container wall would let the surface layer of the wall evaporate and cool the plasma rapidly, causing the fusion cease. In 1951, Lyman Spitzer had the idea to enclose the plasma in a magnetic cage. As the plasma is ionized, it consists of charged particles (positive ions and electrons) that can be influenced by a magnetic field. Their trajectory has two components: a circular motion at right angles to the magnetic field and a linear motion across the magnetic field. The Tokamak was invented by Soviet physicist Igor Tamm and Andrei Sakharov in 1952. Toroidal magnetic fields were used to avoid the particles that escaped at the poles of the magnetic field. However, a toroidal magnetic field was not able to hold the plasma in an equilibrium force balance because the field strength decreased from the inside to the outside of the toroidal field with the effect that the particles drift towards the wall. Therefore, the field lines may not take a circular course about the axis of the torus, but need to be helically looped. The scientists were enthusiastic and predicted in 1955 that in 20 years time, nuclear fusion would provide us with limitless energy. However, the magnetic confinement turned out to be much trickier than assumed. To this day, experiments and tests are being run in nuclear fusion facilities in France to prevent particles from leaving the magnetic field. (http://www.world-nuclear.org/info/Current-and-Future-Generation/Nuclear-Fusion-Power/

Now that we know that fusion is the future of clean and virtually unlimited power for all of our electrical needs, we can move forward into our next topic: Fusion in the Future, and specifically, cold fusion. Get excited to really focus on the chemistry concepts involved with this unique type of energy creation. Until then, keep reading to find out!

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