The First War of Physics (65 page)

Zeldovich, who had been conducting independent research on the possibility of thermonuclear fusion, was now asked to investigate the Super
design that had been delivered to Soviet intelligence by Fuchs. Meanwhile, a second, parallel investigation was initiated under the leadership of Igor Tamm at the Physics Institute of the Soviet Academy of Sciences. Each research group was aware of the other’s existence, but only Zeldovich had sight of Fuchs’ report. Tamm recruited some of the Soviet Union’s most talented young physicists: Semyon Belenky, Vitaly Ginzburg, Yuri Romanov and Andrei Sakharov.

Tamm approached Belenky and 27-year-old Sakharov in a rather furtive manner after a Friday seminar at the institute. He explained what they had been asked to do. ‘Our task would be to investigate the possibility of building a hydrogen bomb and, specifically, to verify and refine the calculations produced by Yakov Zeldovich’s group at the Institute of Chemical Physics’, Sakharov later explained. Nobody had sought his consent to work on thermonuclear weapons, and Sakharov felt he had no real choice in the matter. But it was an opportunity to do physics in an area he regarded as a genuine theoretician’s paradise.

With guards mounted outside their office doors, and armed with new German-made calculators, the young physicists set to work with great enthusiasm, as though ‘possessed by a true war psychology’:

I understood, of course, the terrifying, inhuman nature of the weapons we were building. But the recent war had also been an exercise in barbarity; and although I hadn’t fought in that conflict, I regarded myself as a soldier in this new scientific war. (Kurchatov himself said we were ‘soldiers’, and this was no idle remark.)

Sakharov was particularly impressive. ‘I envy Andrei Sakharov’, Zeldovich said. ‘My brain is built to work like a well-maintained computer. But a computer only works if it is pre-programmed. Sakharov’s brain writes its own programmes.’

Sakharov spent two months studying Zeldovich’s reports and improving his knowledge of gas dynamics. He suspected that the original Super design being investigated by Zeldovich’s group had been inspired by espionage, and he quickly identified its flaws.

By the end of the summer he had devised an alternative design, which in his memoirs he calls the ‘First Idea’. This was the ‘Sloika’ or ‘layer cake’, consisting of alternating layers of deuterium and tritium and U-238. The basic idea is that a core plutonium bomb creates the temperatures and pressures necessary to ignite fusion of the deuterium and tritium nuclei. The fast neutrons released by the fusion reactions then initiate fission in the U-238 layer. This layer serves both to confine the layer of lighter elements and, on fissioning, provides compression of the fusion fuel which further enhances the yield of thermonuclear energy.

The compression achieved by the ionised nuclei from the U-238 layer became known as ‘sakharisation’, at once crediting the scientist responsible for the invention of the process and providing a pun – ‘sakhar’ being the Russian for sugar.

The Soviet design took a further step forward in December 1948, when Ginzburg suggested that the deuterium and tritium fuel in the bomb be replaced by the chemical compound lithium-6 deuteride. Sakharov calls this the ‘Second Idea’. It has the advantage that at room temperatures lithium deuteride is a non-radioactive, chalk-like solid substance, thereby avoiding the problems associated with handling gaseous mixtures of deuterium and tritium or the refrigeration apparatus required to turn these to liquid.

On absorption of a neutron the rare isotope Li-6, accounting for about 7.5 per cent of naturally-occurring lithium, fissions to produce tritium and helium nuclei. So, triggering a plutonium fission bomb in the presence of lithium-6 deuteride produces tritium and deuterium nuclei
in situ
at the temperatures and pressures required for these light nuclei to fuse together, releasing much greater quantities of energy in a thermonuclear explosion.

It was immediately seen as a much more promising design.
¹
It was subsequently agreed that Tamm’s group would concentrate on Sakharov’s ‘Sloika’ proposal, and that Zeldovich’s group would support this work while pursuing further investigations of the original design.

In early 1949 Tamm and Sakharov were summoned to Vannikov’s spacious office in Moscow. Vannikov explained that Sakharov was to be transferred to Arzamas-16 to work with Khariton: ‘It’s necessary for the project’, he said. But Tamm was extremely reluctant to let Sakharov go. He argued that Sakharov promised much in key scientific fields and to limit him to applied research would be a great mistake, not in the country’s best interests.

When the direct line from the Kremlin rang, Vannikov answered. He tensed. It was Beria. ‘Yes, I understand’, he said. ‘Yes sir, I’ll tell them.’ He hung up. ‘I’ve just been talking with Lavrenty Pavlovich [Beria]’, he explained to Sakharov. ‘He is
asking
you to accept our request.’

Beria did not often ask nicely, and he did not ask twice. ‘There was nothing left to say’, wrote Sakharov. ‘Things seem to have taken a serious turn’, said Tamm.

Emergency War Plan 1-49

By January 1949 SAC possessed more than 120 aircraft capable of delivering atomic weapons, consisting of B-29s and B-50s that had been modified for air-to-air refuelling. There were now six bomb-assembly teams, with a further team in training. Flight crews were being drilled relentlessly, and navigation and targeting skills were improving.

LeMay drew up his first war plan. The result, the SAC Emergency War Plan 1–49, was delivered in March 1949. It encapsulated all the lessons LeMay had learned from his experience firebombing Japanese cities. These were simply summarised: hit fast, and hit hard. He called on SAC ‘to increase its capability to such an extent that it would be possible to deliver the entire stockpile of atomic bombs, if made available, in a single massive attack’.

At the time this meant striking 70 Soviet cities with 133 atomic bombs, targeting urban industrial centres, government offices, the oil industry, transport networks and power stations. Of course, not all the bombs were of the latest, higher-yield, design. But a conservative assumption that each bomb would yield a Nagasaki-scale 20,000 tons of TNT equivalent implies a plan to hit the Soviet Union with an explosive force totalling three million tons (three megatons) of TNT. It was estimated that there would be nearly three million civilian deaths, and four million casualties.

Such was the calculus of atomic war. To countenance such a plan required a moral compass set spinning by nothing less than one of Lawrence’s giant magnets. But as LeMay later pointed out, before leaping to moral judgements it helped first to establish a proper sense of perspective:

Incidentally, everybody bemoans the fact that we dropped the atomic bomb and killed a lot of people at Hiroshima and Nagasaki. That I guess was immoral; but nobody says anything about the incendiary attacks on every industrial city of Japan, and the first attack on Tokyo killed more people than the atomic bomb did. Apparently, that was all right …

Towards the end of the war, LeMay had ordered the firebombing of 63 Japanese cities, which had resulted in the deaths of two and a half million civilians. As far as LeMay was concerned, all that atomic weapons had done was make the process so much more efficient.

America was not at war, however, and this was still just a plan. Nevertheless, the temptation to launch a pre-emptive strike must have been very real. A noon SAC reconnaissance exercise over Vladivostok was met with no resistance. ‘We practically mapped the place up there with no resistance at all’, LeMay said later. ‘We could have launched bombing attacks, planned and executed just as well, at that time. So I don’t think I am exaggerating when I say we could have delivered the stockpile had we wanted to do it, with practically no losses.’

LeMay’s plan was judged sufficient to precipitate a collapse of the Soviet Union, or at least sufficient to destroy the Soviet capability for offensive operations. As if this was not enough, the AEC confidently predicted that it could make a stockpile of 400 atomic weapons available by the end of 1950.

A perfect spy

Fuchs was enjoying his job as division head at Harwell and, perhaps for the first time in his life, he was making good friends. There were even rumours of an affair. He had acquired an MG sports car, somewhat more reliable than the dilapidated Buick he had driven while at Los Alamos. He continued to gain respect for his work. Over dinner at a restaurant in Abingdon in September 1948 Oppenheimer had offered him a position at the Institute for Advanced Study in Princeton. He had politely declined.

He had been the perfect spy. But beneath the veneer of calm and quiet authority Fuchs was now in turmoil. He was having some serious doubts about what he had done. He was quickly losing the ability to compartmentalise the two very different sides of his life. At the same time he had become all too aware that he was betraying the trust of his friends. Worse, he was betraying secrets to a regime whose true character was now beginning to emerge into the wider public consciousness, as Moscow crushed its Eastern European satellite states into submission. His political world was changing, dramatically.

‘I then realized that the combination of the three ideas which had made me what I was, were wrong,’ Fuchs later wrote, ‘in fact that every single one of them were wrong, that there were certain standards of moral behaviour which are in you and that you cannot disregard.’

Fuchs started to drink heavily. He grew increasingly nervous during visits to Harwell by his father, Emil, fearing that he would let slip his son’s early Communist affiliations. He began mentally to prepare himself for a final end to his espionage activities. At a meeting with Feklisov in February 1949, sitting on a park bench in Putney Bridge Park near the Spotted Horse pub, Fuchs described his plans for the future.

‘I’d like to help the Soviet Union until it is able to test its atomic bomb. Then I want to go home to East Germany where I have friends. There I can get married and work in peace and quiet. That’s my dream’, he told Feklisov, with a smile.

Fuchs went on to tell of recent meetings he had had with members of his family: his father Emil during a visit to Abingdon, Kristel in Cambridge, Massachusetts, his brother Gerhard, suffering from tuberculosis, in Davos, Switzerland. Feklisov saw an opportunity to provide some small reward for Fuchs’ efforts in support of the Soviet cause.

‘Klaus, I know you’re not working for the money and want none for yourself, Feklisov said. ‘But we do wish to help you with your daily financial problems. I hope you will not feel offended if I offer this small token of our gratitude.’

Fuchs hesitated, but accepted the envelope. ‘Thank you,’ he said, ‘I don’t need the money, but I do appreciate your offer. I’ll send a money order to my brother right away.’

One of Fuchs’ close friends at Harwell was Henry Arnold, the AERE Security Officer. For reasons of his own, Arnold had decided that if there was a Soviet spy operating at Harwell, then Fuchs would be high on his list of suspects.

Fuchs arranged to meet Feklisov again in early April. It would be their last meeting.

First Lightning

Kurchatov’s brother Boris had been the first Soviet scientist to separate plutonium from spent fuel slugs taken from the F-l reactor. A full-scale separation plant, called Installation B, was constructed alongside F-2 at Cheliabinsk-40. It was ready in December 1948. A third installation, designed to purify the plutonium further and convert it to metallic form, was not quite ready by the time the first plutonium nitrate solutions were becoming available in early 1949, and a temporary workshop was set up. By April 1949 Cheliabinsk-40 was producing pure plutonium dioxide.
Shortly thereafter, sufficient plutonium metal was available for the Soviet Union’s first bomb test.

Just as the two hemispheres of the first bomb core were being nickelplated prior to sending them to Arzamas-16 for criticality tests, Pervukhin and a number of Soviet generals arrived to inspect them. They wanted to know how the scientists could be certain it really was plutonium and not just a lump of iron disguised to look like plutonium. Anatoly Alexandrov, responsible for plutonium separation at the plant, assured them it was the genuine article and pointed out that as a result of its radioactivity, the hemispheres were warm to the touch. However, this did not seem to convince them. They pointed out that it was easy just to heat a piece of iron. In frustration, Alexandrov suggested that they could sit with the hemispheres until the next morning and check that they remained warm. The generals went away.

A state commission had been formed to monitor the test, with Beria as chairman and Kurchatov as the scientific supervisor. In May Kurchatov left for the test site. This was Semipalatinsk-21, a small settlement some 50 miles north-west of Semipalatinsk along the Irtysh river in Kazakhstan. In August the scientists and observers began to gather.

Essential hardware and test instruments were transported to Kazakhstan by train. The Soviet scientists travelled quickly, stopping only to change locomotives and check the cargo. At the stations where they did stop, they were surprised to find the platforms deserted. At one such stop, Zeldovich and a number of young scientists disembarked to play volleyball on the empty platform. Zavenyagin ordered them back on the train: ‘They’re supposed to be serious people’, he grumbled. ‘They’re on a responsible mission and they behave like a bunch of eighteen-year-old kids.’

On 28 August Beria, Kurchatov, Khariton, Flerov, Zavenyagin and Zernov watched as RDS-1 was assembled according to Khariton’s strict instructions. The first Soviet test, codenamed First Lightning, was to take place at 6:00 the following morning atop a specially constructed tower over 100 feet high. The scientists were all too aware of the problems that had beset the Trinity test and even now there could be no absolute guarantee
that the bomb would work. Few got any sleep that night. To make matters worse, the weather was poor.

At 2:00am the assembled bomb was moved into the freight elevator which would lift it into position. The intention had been to send the bomb up the tower unaccompanied, but when Beria raised his eyebrows Zernov quickly climbed in alongside. Flerov and a small team of scientists then ascended the tower to mount and check the detonators. Flerov was the last to return.