OUT OF CONTROL
By SIR GEORGE THOMSON, FRS IN the long and dreary history of the attempts to reach international agreement on the control of atomic energy, the brightest gleam shone in the autumn of 1946 when a report was signed by all, including the representatives of the USSR, which . contained the words: 'We do not find any basis in the available scientific facts for supposing that effec- tive control is not technologically feasible.' The scheme variously known as the .Lilienthal and the Baruch plan con- sidered in very considerable:detail a control of atomic energy based fundamentally on the raw materials expected to be used—uranium and thorium, though in fact at the time the use of thorium was only a possibility. It was proposed to control uranium right from the mine, the degree of control increasing fis the process advanced. Certain stages were to be inspected by the proposed international authority; others, the more advanced, were to be managed or, as the United States representatives strongly claimed, actually owned by it.
There is little doubt that if the scheme had been accepted and honestly administered, it would have worked in the conditions of 1946. It might perhaps have been possible for the United States, if she had wished to do so, to cheat by hiding some of her stocks of bombs, but it would not have been at all easy. This opportunity of control has been lost.
There are two reasons why it would not now be possible, even with full agreement of all interested parties, to establish a control which would make the clandestine possession, of bombs impossible. The first is the large number of bombs of the uranium-plutonium type which are almost certainly in the possession of both the USA and the USSR. No doubt these countries have full records of the amount of fissionable material which they have in fact produced, but no one except the most trusted officials of the countries concerned has ever seen them. It would be possible to falsify them so as to show a smaller yield of material from piles and separating plants than was in fact the case. It is fissionable-(explosive) material that counts rather than actual bombs. Once the technique of Making them has been worked out, the bomb cases could be made almost anywhere; one could never be sure that all copies of a blueprint had been destroyed. It is doubtful if even an occupying army, like that in Germany, could be certain of proving the fraud, still less of finding the missing material. Certainly no degree of inspection that a sovereign power could be expected to tolerate would stand much chance. Moreover, in these matters it is essential not merely that justice be done, but that it should obviously be done; the mere fact that it is impossible to be certain destroys the value of such an agree- ment as a means of reducing international tension. If accusa- tions of bad faith were made, even unofficially and unjustly, and could not be disproved, the situation might be worse than if no agreement had been made.
The other difficulty concerns the hydrogen, bomb. This is made ptimarily from deuterium, the heavy isotope of hydrogen which occurs to the extent of one part in 7,000 in hydrogen wherever it is. The most important source is, of course, water.
Here there can be no question of the control of the raw material. The separation is a matter of some difficulty and requires a good deal of power. Theoretically its production could be controlled, but it is not necessary, though it is con- venient, to use large plants. To be sure that it was not being made clandestinely would involve the inspection of all factories down to quite a small size. It seems hardly probable that any great country, least of all the USSR, would agree to such an infringement of privacy and risk loss of commercial, not to say military, secrets.
It is believed that bombs of the uranium-plutonium type are used as a kind of detonator to set the deuterium off. If so, there is a theoretical possibility of control, but it is a very poor one. In the first place, the leakage. of even two or three U-bombs would become extremely serious because of the multiplication of their effect, as each could be the centre of an H-bomb; but, worse still, there are rumours that it may be possible to dispense with the U-bomb as a detonator.
Obviously it would be folly to put an international matter of this importance at the mercy of an uncertain point of tech- nology. Even if the rumours are false now, there can be no confidence that they will remain so. Some at least, of the H-bombs have contained lithium. This element, though not common, is fairly widely distributed in traces. It does not, I think, provide a possible means of control. Not merely is there plenty of it in most large countries, but the amount needed is relatively small—only, in fact, what is actually used in the bomb; while in the case of uranium, quantities of the order of a hundred tons might be required for a pile, though the amount of plutonium needed for an individual bomb is enormously less. (This is partly because only one part in about 140 of the uranium is fissionable.) Further, although lithium is probably a convenience, there is no reason to sup- pose it essential.
One final possibility is control through tritium. This third unstable isotope of hydrogen is believed to form part of the detonator of the hydrogen bomb. Being unstable, it has to be made for the purpose; it is most readily made in a pile similar to, or identical with, those used to make plutonium. It has never been disclosed how much is needed; it may be a small amount. There may here be a faint possibility of control; to examine it one would need access to highly classified information. On general grounds the idea is not attractive.
Apart from the fact that it would probably not be difficult to conceal one plant, or even perhaps to make the needed amount after a declaration of war in piles normally used for making commercial and medical isotopes, it is undesirable to make control rest on a single minor constituent; one can never feel sure that an improvement in ' technique will not make it un necessary.
For these reasons it seems that the possibility of the control of nuclear explosives and the bombs they make has passed.
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