The demise of radiochemistry: moving beyond nuclear science to more relevant fields within environmental and organic chemistry.
I have been musing over the past couple of years about radiochemistry. Once a major field of endeavour, it seems now to have withered, even though its political and environmental importance has arguably increased. What has happened?
Classical radiochemistry started with Marie Curie and her studies on radium, polonium and other radioactive elements. For a number of years, there was a good deal of floundering, with the discovery of radium dionium, emanation and other elements whose names are no longer familiar. Before they were properly identified, along came neutron activation, with the 'discovery' of many "transuranic elements', which turned out to be products of nuclear fission.
Nuclear fission was a great boon for radiochemists, even though a lot of it was done in war-time secrecy. Chalk River was one of the world centres of radiochemistry, with Leo Yaffe, Geoff Wilkinson, Bill Grummet, Bernard Harvey and others discovering many new radionuclides that had never been seen and identified before.
By the time I got into the field, nuclear fission was still a major activity. Fission-yield fine structure was beginning to be understood; mass-yields were thought to be coming pretty well under control; charge distribution was beginning to be studied, and the world was exciting. For a few years, hot-atom chemistry was popular, until it was realized that the field is too complex to be resolved by the experimental and theoretical methods available. Mossbauer spectroscopy came and went. With the advent of radioactive traces and thickness gauges, the rising popularity of remote power sources and the consideration of radio pharmaceuticals, practical applications of radiochemistry were becoming known. Gordon Conferences on radiochemistry and nuclear chemistry were exciting annual events.
By that time, many universities were teaching radiochemistry and textbooks on nuclear and radiochemistry were becoming classics. The famous book by Friedander and Kennedy was the dominant textbook, and perhaps still is, in its several later editions, although others have tried to unseat it as the world's authority. By this time Chalk River began to diminish in prominence. Leo Yaffe went to McGill and there was quite a bit of activity among the universities in Canada. McGill, McMaster, Carleton, Dalhousie, Simon Fraser, Waterloo and others offered graduate research programs in various aspects of radiochemistry.
But now, where would one go in Canada for an advanced course in nuclear and radiochemistry? Having taught such a course at Carleton for fifty years, I am slowly coming to the recognition that I have become an anachronism. I am teaching a field that no longer exists!
This is not to say that the need for such courses has disappeared. Far from it! The need for environmental monitors, radiopharmaceutical chemists, nuclear reactor operators and others is increasing as the likelihood of increased nuclear power becomes evident. In particular, the need for general understanding of radioactivity is increasing both among the general public and especially among our politicians and policy makers. This is apparently a world-wide phenomenon. True, several universities in Canada have courses in nuclear physics and nuclear engineering. But nuclear chemistry is no longer to be found.
The answer to this dilemma becomes clear, now that I think about it. What was called nuclear and radiochemistry has mostly been done. The chemical problems of nuclear science have been largely solved and there is little else for a graduate student to do a thesis on. (Of course, there are those who spend their time developing more new elements, whose half-lives are so short that researchers never produce weighable quantities. But these people are few, and exist only in remarkably wealthy places.)
So what is left? Well, in the same way that thermodynamics has become a part of chemical metallurgy, solid state chemistry has become part of nanotechnology, and activation analysis has become part of analytical chemistry, nuclear and radiochemistry has become an adjunct to other fields of more current relevance. It has essentially split into two parts: radiochemistry and pharmaceutical radiochemistry. Neither is practiced by the radiochemist, but by the environmental chemist and the organic chemist, each of whom can learn the problems of working with radioactive nuclides. Thus, the problems of synthesizing radiopharmaceuticals and disposing of nuclear waste can be managed by other chemists whose training most likely includes some study of radioactivity, but whose focus has switched from studying properties of exotic isotopes to the application of this type of chemistry to a wider range of problems.
In the fall semester of 2008, after my 50 years of increasing anachronism, I have given "la Derniere Classe" in radiochemistry, and I hand over the field to a physical chemist, whose interests are broader than mine are now.
A SHORT HISTORY OF RADIOCHEMISTRY
In 1898, Marie Curie began delving into the isolation of some ores that had mysterious properties. Having discovered the new element polonium, and subsequently radium, she went on to establish the medical uses (and misuses) of radiation in treating cancers and in photographing broken bones.
The next decade or two saw the development of much important physics: the recognition of the nucleus, the theory of the atom and the recognition of isotopes. The decay products of radium were finally identified. But nothing much else happened in radiochemistry for a couple of decades, until the neutron and its uses were discovered. Then it was realized that nuclear transformation was indeed possible. Enrico Fermi and his group in Rome were among the pioneers, as were Frederic Joliot and Irene Curie in Paris and Otto Hahn in Berlin. At the same time, the California group developed the cyclotron so that protons and alpha particles could be driven into target nuclei.
During the 1930s, many new nuclides were found, many of them by serendipity, until finally in 1939 Otto Hahn proved that a suspected radium isotope was in fact barium-140. It was Lise Meitner who realized that Hahn had recognized nuclear fission. The genie, now let out of the bottle, was quickly put back into another bottle--that of military secrecy. It was quickly realized that the two new fission fragments would fly apart with very high energy and that extra neutrons produced in this process would lead to a continuous chain reaction. Thus, it was realized, would perhaps lead to a usable nuclear bomb and since the Germans first discovered nuclear fission, they would likely attempt to capitalize on their new process. While the United States was not in the Second World War initially, and was not yet contemplating getting involved, a letter from a group of scientists, led by Albert Einstein, convinced the President of the U.S. to get into the competition. This led to great secrecy and, as is now well known, the development of the bomb.
From there on, much work has been done, both to tidy up those newly-discovered nuclides and to discover more of them, and to develop many more uses for chemical radioactivity.
It could be said that this phase of radiochemistry has run itself out and there is very little else to do except a bit of cleaning up here and there. But no, there is much more to do; however, it isn't the classical radiochemistry any more. It is now environmental chemistry, medical physiological chemistry and pharmaceutical chemistry. It appears that nuclear and radiochemistry have become things of the past, but as the Phoenix rises from the ashes, perhaps the new disciplines are as vigorous as ever.
This was a topic of discussion at a recent international conference (INCC, Cancun, 1 April, 2008) Compare "La Derniere Classe", by Alphonse Daudet, a story about a French teacher in Alsace being replaced by another who would teach only in German.
By Don Wiles, FCIC
Don Wiles, FCIC, is a chemist-at-large at Carleton University.
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|Title Annotation:||RELEVANCE OF RADIOCHEMISTRY|
|Publication:||Canadian Chemical News|
|Date:||Sep 1, 2009|
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