Part 4
Would 30 grams of tritium be enough to serve as the superkindling for exploding, let’s say, 1,000 kilograms (one ton) of deuterium? We shall probably not know until we actually try it. It will largely depend on the temperature generated by our more powerful A-bomb models. If it is true, as Senator Johnson informed his television audience, that they have “six times the effectiveness of the bomb that was dropped over Nagasaki” (which, by the way, had more than twice the effectiveness of the Hiroshima model), it is quite possible that their temperature is as high as 150 million, or even 200 million, degrees. In that case, the extra kindling of a 20–30 gram D-T mixture, with its tremendous burst of 5,000,000 kilowatt-hours of energy in 0.28 to 0.38 microseconds (added to the vast quantity already being liberated by the exploding plutonium, or U-235), might well heat the deuterium to the proper ignition temperature and keep it hot long enough for its mass to explode well within 1.2 microseconds. In any case it would appear logical to expect that a mixture of 150 grams of tritium and 100 grams of deuterium, which would release an energy equal to that of the Hiroshima bomb, should be able to do the job with plenty of time to spare.
We thus have a threefold answer to the question: Can the H-bomb _actually_ be made? As we have seen, the deuterium bomb is definitely not possible. The tritium bomb is theoretically possible, but definitely not practicable. But a large deuterium bomb using a reasonably small amount of a deuterium and tritium mixture as extra kindling is both possible and feasible.
We now also stand on solid ground in dealing with the questions of cost and of the time it would take us to get into production. With these questions answered, we can then decide whether the H-bomb, if made, will add enough to our security to make the effort worth while.
We know at this stage that the H-bomb requires three essential ingredients. It needs, first of all, an A-bomb to set if off. We have a sizable stockpile of them. It needs large quantities of deuterium. We have built several deuterium plants during the war, and they should be large enough to supply our needs. Since it is extracted from water, the raw material will cost us nothing. The only item of cost will be the electric power required for the concentration process, and this should not be above $100 per kilogram, and probably less. The third vital ingredient, tritium, can be made in the giant plutonium plants at Hanford, Washington. Thus it can be seen that all the essential ingredients of the H-bomb, the costliest and those that would take longest to produce, as well as the multimillion-dollar plants required for their production, are already at hand.
This means that as far as the essential materials are concerned, we are ready to go right now. And as for the cost, it would appear to require hardly any new appropriations by Congress, or, at any rate, only appropriations that would be mere chicken feed compared with the five billion we have already invested in our A-bomb program.
The raw material out of which tritium is made is the common, cheap light metal lithium, the lightest, in fact, of all the metals. It has an atomic weight of six, its nucleus consisting of three protons and three neutrons. When an extra neutron invades its nucleus, it becomes unstable and breaks up into two lighter elements, helium (two protons and two neutrons) and tritium (one proton and two neutrons). They are both gases and they are readily separated. And while lithium of atomic weight six constitutes only 7.5 per cent of the element as found in nature (it comes mixed with 92.5 per cent of lithium of atomic weight seven), there is no need to separate it from its heavier twin, since the latter has no affinity for neutrons and nearly all of them are gobbled up by the lighter element.
The production of tritium, even in small amounts, will nevertheless be a formidable process. As we have seen, it takes eighty times as many neutrons to produce any given amount of tritium as to produce a corresponding amount of plutonium. Since the lithium will have to compete with uranium 238 (parent of plutonium) for the available supply of neutrons, and since the number of atoms of U-238 per given volume is nearly forty times greater than the number of lithium atoms, the rate of tritium production would be very much slower than that of plutonium. On the other hand, even if it took as much as two hundred times as long to produce a given quantity of tritium, the handicap would be considerably overcome because of the relatively small amounts that may be required. If, for example, we should need only 30 to 150 grams of tritium per bomb, it would take our present plutonium plants only six to thirty times longer to produce these quantities than it takes them to produce one kilogram of plutonium. A hypothetical plant such as the one mentioned in the official Smyth Report, designed to produce one kilogram of plutonium per day, would thus yield 30 grams of tritium in six days.
How much tritium would be needed for an adequate stockpile of H-bombs? Since our primary reasons for building it are to deter aggression, to prevent its use against us or our allies, and as a tactical weapon against large land armies, it would appear that as few as twenty-five, or fifty at the most, would be adequate for the purpose. On the basis of the larger figure (assuming 30 to 150 grams of tritium per bomb), it would mean an initial stockpile of only 1.5 to 7.5 kilograms of tritium, which would entail the sacrifice of about 120 to 600 kilograms of plutonium. Once this initial outlay had been made, however, our plutonium sacrifice would be reduced annually to only one twenty-fourth of the original respective amounts—namely, 5 to 25 kilograms a year—just enough to make up for the decay of the tritium at the rate of fifty per cent every twelve years.
One of the major problems to be solved, in addition to the main problem of designing the assembly, arises from the fact that the deuterium and the tritium booster will have to be in liquid form. Liquid hydrogen boils (that is, reverts to gas) at a temperature of 423 degrees below zero Fahrenheit under a pressure of one atmosphere (fifteen pounds per square inch). To liquefy it, it is necessary to cool it in liquid air (at 313.96 below zero F.) while keeping it at the same time under a pressure of 180 atmospheres. To transport it, it must be placed in a vacuum vessel surrounded by an outer vessel of liquid air. This would point to the need of giant refrigeration and storage plants, as well as of refrigerator planes for transporting large quantities of liquid deuterium and its tritium spark plug.
Will the H-bomb, if made, add enough to our security to make the effort worth while? We have seen that the required effort may, after all, not be very great. In fact, it may turn out to be a relatively small one, in view of the fact that all the basic ingredients and plants are already at hand and fully paid for. But supposing even that the effort turns out to be much more costly than it now appears? The question we must then ask ourselves is: Can we afford not to make the effort?
It is true, of course, as some have pointed out, that ten or even fewer A-bombs could destroy the heart of any metropolitan city, while only one would be quite enough, as we know, for cities the size of Hiroshima or Nagasaki. But that neglects to take into consideration the fact that one H-bomb concentrates within itself the power of thirty A-bombs to destroy by fire and by burns an area of more than 1,200 square miles at one blow. Nor does it take into consideration the military advantage of delivering the power of a combination of ten and thirty A-bombs in one concentrated package, which would make it a tremendous tactical weapon against a huge land army scattered over many miles, or its possible enormous psychological effect against such an army.
Most important of all, this view grossly minimizes the apocalyptic potentialities of the H-bomb for poisoning large areas with deadly clouds of radioactive particles. It is a monstrous fact that an H-bomb incorporating one ton of deuterium, encased in a shell of cobalt, would liberate 250 pounds of neutrons, which would create 15,000 pounds of highly radioactive cobalt, equivalent in their deadliness to 4,800,000 pounds of radium. Such bombs, according to Professor Harrison Brown, University of Chicago nuclear chemist, could be set on a north-south line in the Pacific approximately a thousand miles west of California. “The radioactive dust would reach California in about a day, and New York in four or five days, killing most life as it traverses the continent.”
“Similarly,” Professor Brown stated in the _American Scholar_, “the Western powers could explode H-bombs on a north-south line about the longitude of Prague which would destroy all life within a strip 1,500 miles wide, extending from Leningrad to Odessa, and 3,000 miles deep, from Prague to the Ural Mountains. Such an attack would produce a ‘scorched earth’ of an extent unprecedented in history.”
Professor Szilard, one of the principal architects of the A-bomb, has estimated, as already stated, that four hundred one-ton deuterium bombs would release enough radioactivity to extinguish all life on earth. Professor Einstein, as we have seen, has publicly stated that the H-bomb, if successful, will bring the annihilation of all life on earth within the range of technical possibilities. The question we must therefore ask ourselves is: Can we allow Russia to be the sole possessor of such a weapon?
There can be no question that Russia is already at work on an H-bomb. Like ourselves, she already has the plutonium plants for producing both A-bombs and tritium. She can produce deuterium in the same quantities as we can. In Professor Peter Kapitza she has the world’s greatest authority on liquid hydrogen.
Furthermore, she has great incentives to produce H-bombs. Since she is still behind us in her A-bomb stockpile, she can, in a sense, catch up with us much more quickly by converting her fewer A-bombs into H-bombs that would be the equivalents of ten to thirty A-bombs each, thus increasing the power of her stockpile ten to thirty times. Equally if not more important from Russia’s point of view is the stark fact that an H-bomb could be much more easily exploded near a coastal city from a submarine or innocent-looking tramp steamer, since most of our great cities are on the seacoast, whereas Russia practically has no coastal cities.
Even if we openly announced that we would not make any H-bombs, it would not deter Russia from making them as fast as she could, not only because she would not believe us but also because her sole possession would greatly weight the scales in her favor. If, God forbid, she finds herself one day with a stockpile of H-bombs when we have none, she would be in a position to send us an ultimatum similar to the one we sent to the Japanese after Hiroshima: “Surrender or be destroyed!”
Valuing their liberty more than their lives, the American people will never surrender. But while there is time, would anyone advocate that we run the risk of ever facing such a choice?
III SHALL WE RENOUNCE THE USE OF THE H-BOMB?
A few days after President Truman announced that he had directed work “to continue” on “the so-called hydrogen, or super bomb,” a group of twelve eminent physicists, including half a dozen of the major architects of the atomic bomb at Los Alamos, who, no doubt, are playing a similar role in the development of the H-bomb, issued a statement urging the United States to make “a solemn declaration that we shall never use the bomb first,” and “that the only circumstances which might force us to use it would be if we or our allies were attacked by _this_ bomb.” They added that “there can be only one justification for our development of the hydrogen bomb, and that is to prevent its use.”
Signers of the statement, unprecedented in the annals of science (with the possible exception of a secret memorandum submitted to the government just before the A-bomb was used), included such outstanding physicists as Hans A. Bethe of Cornell; Kenneth T. Bainbridge of Harvard; Samuel K. Allison, University of Chicago; Dean George B. Pegram, Columbia; C. C. Lauritsen, California Institute of Technology; Bruno Rossi and Victor F. Weisskopf, Massachusetts Institute of Technology; F. W. Loomis and Frederick Seitz, University of Illinois; Merle A. Tuve, Carnegie Institution of Washington; R. B. Brode, University of California; and M. G. White, Princeton—all, with the exception of Dr. Tuve, professors of physics at their respective universities. Those among them who did not directly participate in the development of the A-bomb played major parts in other scientific wartime projects, such as radar and the proximity fuse.
Implicit in their statement was the first confirmation—indeed, the most authoritative we have had so far from scientists with first-hand knowledge of the subject—that a hydrogen bomb of a thousand times the power of the A-bomb could be made. More than that, they informed us that Russia may complete the H-bomb in less than four years, meaning, of course, that we too could achieve the same goal in the same period. We were thus provided by the experts with a time-table on which we must act if we are not to run the risk of Russia’s getting the H-bomb ahead of us, and so being in a position to use it, or threaten its use, against the nations of western Europe, as the greatest blackmail weapon in history.
The statement summarizes in essence the principal points of view that have been advanced so far on what policy we should adopt on the H-bomb, and since it was promulgated by men known to have definite inside knowledge of the subject, it deserves closer scrutiny than it has hitherto received.
“It was stated correctly,” they inform us at the outset,
that a hydrogen bomb, if it can be made, would be capable of developing a power 1,000 times greater than the present atomic bomb. New York, or any of the greatest cities of the world, could be destroyed by a single hydrogen bomb.
We believe that no nation has the right to use such a bomb, no matter how righteous its cause. The bomb is no longer a weapon of war, but a means of extermination of whole populations. Its use would be a betrayal of morality and of Christian civilization itself.
Senator Brien McMahon has pointed out to the American people that the possession of the hydrogen bomb will not give positive security to this country. We shall not have a monopoly of this bomb, but it is certain that the Russians will be able to make one, too. In the case of the fission bomb the Russians required four years to parallel our development. _In the case of the hydrogen bomb they will probably need a shorter time._
We must remember that we do not possess the bomb but are only developing it, and Russia has received, through indiscretion, _the most valuable hint that our experts believe the development possible_. Perhaps the development of the hydrogen bomb has already been under way in Russia for some time. But if it was not, our decision to develop it must have started the Russians on the same program. If they had already a going program, they will redouble their efforts.
Statements in the press have given the power of the H-bomb as between two and 1,000 times that of the present fission bomb. Actually, the thermonuclear reaction on which the H-bomb is based is limited in its power only by the amount of hydrogen which can be carried in the bomb. Even if the power were limited to 1,000 times that of a present atomic bomb, the step from an A-bomb to an H-bomb would be as great as that from an ordinary TNT bomb to the atom bomb.
To create such an ever-present danger for all the nations of the world is against the vital interests of both Russia and the United States. Three prominent Senators have called for renewed efforts to eliminate this weapon and other weapons of mass destruction from the arsenals of all nations. Such efforts should be made, and made in all sincerity from both sides.
In the meantime, we urge that the United States, through its elected government, make a solemn declaration that we shall never use this bomb first.
Before discussing in detail the merits of the proposal that the United States renounce the use of the H-bomb, “no matter how righteous its cause,” except in retaliation for its use against us or our allies, it behooves us to examine the effect of our decisions to proceed with the development of the H-bomb on Russia’s A-bomb progress.
We know that the H-bomb requires an A-bomb for its trigger. We also have strong grounds for assuming that, in addition to the A-bomb, an H-bomb will require certain quantities of tripleweight hydrogen, or tritium, as extra superkindling to boost the A-bomb. We know, furthermore, that it takes eighty times as many neutrons to make a given quantity of tritium as it does to make a corresponding amount of plutonium, which, of course, means a reduction in A-bombs.
Hence, should Russia decide to embark on an H-bomb program of her own, or to “redouble her efforts,” it would lead inevitably to a serious curtailment in her stockpile of A-bombs. While we would have to make the same sacrifice of plutonium, it is obvious that we can afford the sacrifice much better than Russia, since we already have a sizable stockpile of both plutonium and uranium bombs, whereas she has just begun building her stockpile. The situation for her would be much worse if she has put all her atomic eggs in the plutonium basket without bothering to build the much more complicated and costly uranium separation plants, as the incomplete evidence available would seem to indicate. In that case she would be faced with a serious dilemma indeed, for you cannot have H-bombs without A-bombs, and you cannot have A-bombs without plutonium, and if, as the evidence indicates, she has built her A-bomb program exclusively around plutonium, she would have to sacrifice quantities she could ill afford to spare, at this stage of her development, of the only element she desperately needs for building up her A-bomb stockpile.
How do we know that Russia’s A-bomb is made of plutonium? We have the testimony of Senator Johnson of Colorado, who assured us in his famous television broadcast of November 1, 1949 that “there’s no question at all that the Russians have a bomb more or less similar to the bomb that we dropped at Nagasaki, a plutonium bomb.” In this single sentence the Senator from Colorado, who as a member of the Joint Congressional Committee on Atomic Energy has access to such information, inadvertently let at least three cats out of the bag. He confirmed that the Nagasaki bomb was made of plutonium (though, in fairness, it must be said that this had been known unofficially for some time); he told us that we had found out not only that “an atomic explosion had occurred in the U.S.S.R.,” as the President had announced in carefully chosen words, but that the explosion was that of an atomic bomb and that, more important still, the bomb was made of plutonium. And in doing so he, furthermore, gave away the secret of how we had obtained that information, something the Russians very much wanted to know. Not being a scientist, Senator Johnson obviously did not realize that the split fragments (fission products) of a plutonium bomb differ from those given off by the explosion of a uranium bomb, so that in revealing that we knew what the bomb was made of he would also be revealing at the same time that we found it out by examining radioactive air samples and finding them to contain fission fragments of plutonium, as well as whole plutonium atoms that escaped fission.
There is thus no doubt that the Russians have built nuclear reactors for producing plutonium from nonfissionable uranium 238. We cannot, of course, be sure that they have not at the same time also built plants for concentrating uranium 235, but the odds favor the negative. We built uranium separation plants at Oak Ridge, Tennessee, and plutonium plants at Hanford, Washington, during the war because we didn’t know at the time which method would work, and we gambled on the chance that, by building plants for producing fissionable materials by four different methods, at least one of them might work. Had we known at the time that the plutonium plants were practical, it is quite likely that we would not have invested a billion dollars in building the uranium separation plants. Since the Russians have obviously decided on plutonium plants as the simplest and cheapest (three plutonium plants cost us a total of $400,000,000, whereas a single large uranium separation plant cost half a billion), it is hardly likely that they would consider it worth while to invest in the much more costly uranium separation plants.
As Senator Johnson said in the same broadcast: “We tried out four different methods of making a bomb and all of them succeeded, but one of these methods was superior to all the others in simplicity and effectiveness, and we told the Russians and we told the world that fact. Of course, they didn’t have to make the experiments that we had to make to find out by elimination which method was the most effective and which the one that they should follow.”
The evidence is thus strongly in favor of the assumption that Russia has only plutonium plants as her sole source of A-bomb material, whereas we have both plutonium plants and gigantic uranium plants in full operation. If that is so, then our forcing Russia to embark on an H-bomb program, at a time when her A-bomb program is barely started, will place her under a double handicap in her race to catch up with us in A-bombs, and at least to keep abreast of us, if not ahead, in H-bombs. For in this grim race we have a dual if not a triple advantage: our much superior stockpile, both in numbers and no doubt in quality, and our gigantic plants for concentrating U-235, the production of which would not have to be curtailed at all, since tritium can be made only in plutonium plants. In fact, we are now in the process of construction of two great additions to the uranium plant at Oak Ridge.