Tuesday, 11 September 2012
Space probes, light houses and pacemakers
You might think of nuclear energy as being used in only two ways; in a nuclear reactor in a power plant helping you boil the kettle, or in the core of a nuclear weapon. However, it turns out nuclear energy can be used, and produced, in some more unusual ways.
Not only do radioactive isotopes constantly give off radiation at a known, steady rate, but they also give off heat, sometimes for many years. Some of them are warm to the touch, and plutonium 238 will actually begin to glow red hot if you cover it with an insulating material (as seen in the picture above). This property is exploited in devices known as radioisotope thermoelectric generators (or RTG’s), which convert this heat into electricity for powering systems that must function for long periods of time without maintenance, such as space probes.
As with many other areas of nuclear history however, the deeper you look, the more peculiar it becomes. It turns out that plutonium batteries were used, in a very limited number of cases, to power pace makers. Its pretty hard to think of an element more hostile to life than plutonium; massively radioactive and poisonous, and a key component of most nuclear weapons, yet here it is playing a role in preserving life.
RTG’s were utilised for one more unlikely task; powering lighthouses in remote regions of the Soviet Union. It was a bit much to ask someone to man a conventional lighthouse on the vast, icy wastes of the north Russian coast, so they were instead fitted with RTG’s that would require no maintenance over their lifetime.
This though gives rise to a very frightening possibility. Because the RTG’s are in such remote locations, someone could nick a cheeky bit of radioactive material and nobody may ever notice. What’s the big deal you say? Surely no one can make a nuclear bomb out of that? Well, not strictly speaking, but they could make a crude, so-called “dirty bomb”. This is a conventional explosive strapped onto a quantity of a radioactive isotope, which spreads it over a given area and renders it uninhabitable. Imagine what would happen to the UK economy if one of those went off in the city of London’s “square mile”…
Indeed, the whole of nuclear history is fraught with fears of weapons or nuclear materials going missing. The fact remains that it’s actually pretty easy to mislay a nuclear weapon. The US alone has 5113 of the things, so they’re bound to drop one behind the sofa occasionally. It is believed that they have lost eleven, often in tragically comic circumstances, such as when a jet armed with a 1 megaton bomb rolled off the deck of an aircraft carrier in 1965, immediately sinking to the bottom of the ocean and taking its pilot and its lethal cargo with it.
Perhaps even more sinister than the possibility of these weapons getting into the wrong hands is the possibility of computer error in missile warning systems. The most chilling example is the so called “Norwegian rocket incident’ of 1995. American scientists had informed the international community they would be launching a research rocket that would follow a trajectory similar to that used by nuclear missiles, but apparently not all parts of the Russian military had been told. The appearance of the rocket on radar screens caused a mass panic, and the briefcase containing Nuclear launch codes was presented to then president Boris Yeltsin, who had seconds to make a decision. Blind luck prevailed as Yeltsin decided not to launch. I leave you with the cheerful thought that this situation could recur at any time, and not end quite so well…