The Chemist Who Hardly Was and the Chemical Reaction that Actually Wasn't
Background image courtesy Brandon Morrison.
In honor of the International Year of Chemistry, a blog carnival is being hosted by the blog network of C&ENews, CENtral Science. For those of you who are only reading this because we're family or long-time friends on Facebook, the call for posts over at CENtral Science defines 'blog carnival' like this:
A blog carnival is a periodic collection of blog posts written loosely around a single theme that are then aggregated at the host blog.
The theme is "Your favorite chemical reaction."
I guess I should start by confessing that I'm not a chemist. When I studied geology as an undergraduate, I thought I'd eventually be a geologist, but I'm not really that either. I'm somewhere in the middle--a Ph.D. student in a structured, repeating universe known as crystallography.
Tasked with writing about my favorite chemical reaction, I had a bit of a problem. I didn't really have one, and when I finally thought of one that I liked, it wasn't really a chemical reaction at all. It was a nuclear reaction.
The difference is that chemical reactions refer to the combination or separation of elements through electronic interactions, while nuclear reactions occur when nuclei themselves are split or combined. If chemical reactions happen between friends at parties, nuclear reactions are for the introverts of the periodic table.
In a special type of nuclear reaction, a nuclear chain reaction, an atom of uranium-235 becomes unstable and splits into smaller fission products when hit with a stray neutron. This event releases a few neutrons and a tremendous amount of energy. When one of the released neutrons smacks into another uranium-235 atom, the process continues. This will go on until the supply of fissile uranium-235 is exhausted, the introduction or in-growth of neutron absorbing elements interferes, or a rapid build-up of heat causes the reacting material to blow itself apart. It is this chain reaction, albeit in a controlled fashion, that makes uranium-235 valuable for energy production in nuclear reactors.
One of the most interesting occurrences of a nuclear chain reaction is the Oklo natural nuclear reactor in Gabon, Africa. Discovered in 1972 by an attentive French physicist, Oklo was found to have sustained nuclear reactions for a period of 1 million years following its formation nearly 3 billion years ago.
What's better than a single natural nuclear reactor? 17 natural nuclear reactors! Oklo doesn't actually refer to just one reactor but a group of 17 natural nuclear reactors. These reactors formed as the result of the build-up of a massive uranium ore, and operation began because the relative abundance of uranium-235 was high enough billions of years ago to jump-start a natural nuclear reaction.
Pretty cool, right?
Want to know more? Check out my sources:
Loss, Robert. "Oklo Fossil Reactors." 15 December 2010. Curtin University of Technology. 26 September 2011. link
Meshik, Alex P. "The Workings of an Ancient Nuclear Reactor." 26 January 2009. Scientific American. 26 September 2011. link