THIS FUSS ABOUT ATOMS

New Zealand Listener, Volume 19, Issue 480, 3 September 1948, Page 19

THIS FUSS ABOUT ATOMS

(From a talk recorded for the NZBS by PROFESSOR

F.J.

LLEWELLYN

of Auckland University College )

scientists and engineers in the Old .and. the New World directed all their energies towards the production ‘of an atomic bomb. They eventually succeeded and the war with Japan ended even though the Japanese Armies, which were retreating, had not suffered the complete military defeat which had just overtaken their German Allies. In other words atomic weapons destroyed war in 1945, at least temporarily; can they now help to build a better world from the wreckage of the old one? The answer is an unqualified "Yes" provided only that we will learn, and- never forget, the lessons of those two terrible days in the spring of 1945. The most obvious, and probably the least important, method of utilising 1939 to 1945 atomic

atomic energy is to direct the great heat "produced in an atomic fission into useful channels. For example, with this heat we could raise steam for driving turbines and other steam engines; we could heat water for domestic and industrial purposes

and this hot water supply could be piped all over our cities for our greater convenience. Enormous Cost One of the main obstacles im the widespread industrial use of atomic power is the enormous cost entailed in separating the U-235 atoms in natural uranium, However, this natural uranium-a mixture of U-235 atoms and U-238 atomshas an ace up its sleeve. When it is bombarded with neutrons some of the U-235 atoms split up, releasing energy and more neutrons; the U-238 atems can capture these neutrons and become new atoms. When these new atoms have settled down they are themselves capable of undergoing fission in the same way as the atoms of U-235. In this backhanded manner uranium compliments the scientist on his achievements by supplying him with an easy method of controlling that rate of fission of U-235 as well as providing him with a new kind of atom. The factory set up in Washington for the production of these new atoms-they are called plutonium -represents the ultimate realisation of the alchemist’s dream-the transmutaticn of one element into another. Plutonium can be made on a large scale

and much more cheaply than U-235 can be isolated from natural uranium, Our supply of atomic fuel is therefore reasonably adequate. Atomic fuel is a good name because it gives one the right idea of the appliéation of plutonium and U-235 to the needs of industry. It is a fuel and as such provides heat. This heat has to be converted into work by some kind of engine in the same way as coal or oil is burned to produce heat which is converted into electricity by means of a steam turbine and a dynamo. But atomic fuel must be used on a moderately large scale in order to sus-_ tain the fission reaction, and because the heat energy it develops has to be converted into power through an orthodox heat engine-there is little likelihood of its use in small power units such as those used for propelling motor

cars and trucks, The principal use for atomic fuel will be in supplying heat for large power units; electric power stations, large oceangoing vessels, and possibly large air liners and freight carriers come within this category. It is unlikely, too, that

atomic fuel will operate through any but the orthodox heat engines, at least in the immediate future, so that although the atomic fuel will occupy a comparatively small space, the engines will be as large as ever and no more efficient than they are at present. a The advent of atomic fuel will not then revolutionise power generation in the foreseeable future, nor will it greatly reduce power costs; but it will increase the availability of power especially in countries where there is little coal or water power. The great industrial cities of the world need no longer belch forth smoke and soot to pollute the atmosphere and corrode the buildings, Atomic fuel, in this sense at least, is clean, Why So Much Fuss? Why, then, we may ask, is so. much fuss. made about this new ‘source of power? We are abundantly endowed with alternatives. At our present rate of consumption the proved coal reserves will last a few thdusand years and from coal we can make petroleum when the natural supply is exhausted. Many ridiculous predictions have been made concerning the peaceful application of atomic fuel, and these have served only to confuse and confound us. Even if we make the assumption that one ton of atomic fuel will have the same cost as one ton of coal and that this quantity will supply energy equivalent to burning just over three million tons of coal; then the cost of power in the home or factory will be reduced by only about (continued on next page) i

Atomic Energy and the Future

(continued from previous page) 5-10 per cent. This is a worthwhile advance, but it is not revolutionary. The great advantages which atomic fuel has over all others is its small weight, its ability to function without oxygen, and the absence of noxious combunstion gases. Power plants could be operated in confined spaces, for example, below the surface of the earth or even beyond the limits of the atmosphere. This is, However, by no means the whole of the peacetime story of atomic energy; in fact, the production of power by. means of atomic fuel is one of. the least interesting, and probably also one of the least important, roles which the control of nuclear fission brings to us. When an atom of U-235 or plutonium is torn asunder by the bombarding neutron, a great deal of energy is liberated as some of the matter of the atom is converted inte heat; neutfons and a host of other particles are ejected. The neutrons may be instrumental in starting other nuclear fissions, but the other particles when they settle down after the excitement become ordinary atoms which are of course much lighter in weight than the original U-235 or plutonium atoms. Dangerous When Excited These lighter atoms, which we call "fission products," are extremely dangerous to life until they have really settled down; they are radioactive, and they emit, during their settling-down process, a number of radiations; the most harmful is the very short wave-length radiation which can penetrate matter and has an extremely disruptive effect upon human tissues. Directly then by collecting the fission products and by many other methods we now have a whole collection of excited atoms, some of which take a very long time before they settle down and cease to emit their radiations. These artificially radioactive atoms behave chemically exactly like their unexcited brothers, but they always reveal their whereabouts by the radiation which they emit. If they are used in extremely small quantities mixed up with vast proportions of ordinary atoms their radioactivity becomes useful as a sort of label. For example, if

you eat a loaf of bread in which one cellulose molecule in every ten million contains a radioactive carbon atom it is quite an easy matter to trace the digestion and ultimate destination of the labelled atom by following the radiation source. In more specific circumstances it is possible to investigate bone formation, glandular activity and so on by merely following the labels around. Further, samples of these various kinds of radioactive atoms can now be made relatively cheaply, and each provides its own particular brand of radiation as it settles down. Medical and Chemical Uses Whereas previously we had only radium as our useful, naturally-occurring source of radiation, we can now choose from a very large number of different radioactive atoms to suit the particular purpose we have in mind. Already there is some evidence that biological systems are affected differently by the radiations emitted by the various fission products during their settling-down processes. These radiations which curb the usefulness of atomic fuel for power production, in that vast quantities of metal and other materials are required to shield the operators, thereby keeping the weight of the installation. highthese radiations properly controlled and carefully selected may constitute one of the greatest therapeutic agents of tomorrow’s medical practice. In the chemical industries, too, there are already indications of their usefulness. We can anticipate considerable advances in the polymerisation processes now in use in the manufacture of plastics and rubber.. Some success has already been achieved in this field. A large number of drugs and other physiologically active substances which are produced only in plants and animals will probably appear as by-products. of chemical reactions induced by these new radiations. Already some viruses have been relieved of their virulence, and converted into innocuous. producers of antibodies and this opens up vistas in which these carriers of disease and death may be made, under the influence of the specific radiation, to purge a human body of the torments which they themselves pave caused.