The Miracle of Atomic Energy

MR. LAWSON: Today The Empire Club of Canada is honoured by the presence of one of Great Britain's outstanding scientists. It is fitting that to make this address Sir John Cockcroft flew this morning from Chalk River, for that was the scene of one of his many triumphs. It was during the years 1944 to 1946 that Sir John was director of the joint Canadian-British Nuclear Research Centre built at Chalk River in this province.

Sir John was born in 1897. He received his higher education at the Universities of Manchester and Cambridge. At Cambridge he became a Fellow and for a time Professor of Natural Philosophy. Much of his earlier work was in the field of Engineering but he later turned to Physics where his achievements have been outstanding. It has been said that his original experiments in association with Dr. E. T. S. Walton are the seed from which has grown the whole new science of Nuclear Chemistry. Many of the researches now being carried out in the Physics Laboratories of Great Britain, Canada and the United States arise directly from his work.

Shortly before the Second World War began, Sir John had realized the great importance of Radar methods of air craft detection for the defence of Britain, and his influence at the Cavendish Laboratory and later at Malvern was of decisive importance in the development of Radar. In 1944 Sir John came to Canada as Director of the Atomic Energy Division, National Research Council of Canada. In Montreal, and later at Chalk River, he was in charge of a large group of British, French and Canadian scientists working on Plutonium production. After the War, when the Atomic Energy Research establishment was set up in the United Kingdom at Harwell, Sir John became its Director and has been active in Atomic Energy Research work ever since.

Sir John's achievements have received worldwide recognition. He holds honorary degrees from some twenty universities; and there is scarcely a scientific society anywhere in the civilized world which has not seen fit to honour him, either with an award or a medal or by electing him as an honorary member.

I mentioned Sir John's early education and lectureship at Cambridge University. On the 28th of this very month Sir John will move his home from the house he has occupied for thirteen years at Harwell to the house he built at Cambridge over thirty years ago where he formerly lived. From his Cambridge home he will direct the building of the new College at Cambridge named after Sir Winston Churchill, for Sir John has been appointed Master Elect of Churchill College.

No one is better qualified to describe the work being done at Harwell and to tell us of the miracle of Atomic Energy. I will now ask Sir John Cockcroft to address us.

SIR JOHN COCKCROFT: The Atomic Energy Research Establishment at Harwell was founded on January 1st, 1946. The Founder Members including the first Director will always consider it to be a daughter establishment of Chalk River since it was there, working in collaboration with Canadian scientists and with help from the U.S. that we learnt our trade.

I was flown off from Prestwick in a U.S. bomber in April 1944 to take charge of the joint Canadian-U.K. Atomic Energy Project, which was then established in the University of Montreal. Collaboration with the United States had just been agreed as a result of the Quebec Conference and I was able to have discussions in Chicago on methods of design of atomic piles and also with the formidable General Groves in Washington, who released for the Canadian project, and from Canadian production sufficient heavy water and uranium to get on with the job. In about a year we had built our first zero energy heavy water reactor the ZEEP, which was the first of its kind in the world, built for the study of reactor physics. By the time I left a year later we had almost completed the construction of the powerful NRX heavy water research reactor, which for a long time was the best tool of its kind in the world.

During this year some of the British members of the team had begun to work on the design of the first atomic pile to be constructed in Britain, for in October 1945, the U.K. Government had decided to found an Atomic Energy Research Establishment, and the Royal Air Force Establishment at Harwell was ceded to us during the course of my visit to England in Autumn 1945. We decided to base the U.K. programme on graphite moderated reactors because we did not have heavy water available and we were able to arrange for the production of the high purity graphite necessary at Welland in Canada. A 'Graphite Group' was formed for the design of two atomic piles and the basic specifications were worked out and transmitted to U.K. for turning into detailed drawings.

We also began work at Chalk River on the chemical process to be used for the separation of plutonium and fission products from irradiated uranium. An irradiated uranium bar was obtained from the U.S. and dissolved at Chalk River and Dr. Spence was able by experimental work on a laboratory bench on a test tube scale to work out the process which was to be adopted in the great chemical separation plant which was to be built at Windscale at a cost of about £ 15 million. There was much disquiet amongst our engineers as to whether the process based on such small scale experiments would work, but it worked without any hitch and has been operating steadily for 7-1/2 years.

I visited our newly acquired Harwell airfield on a wet windy day in February 1946, the rain blowing almost horizontally across the airfield. The R.A.F. had moved out and already we had begun work on the conversion of barrack

blocks into laboratories and offices. By the autumn we had erected 100 prefabs to house our staff and by August of the following year our first Atomic Pile the GLEEP was operating, thanks to the enormous drive of a New Zealand team. Less than a year later it was followed by the much more powerful BEPO which has given very good service ever since and has been a major source of radioactive isotopes for the world.

The construction of our BEPO reactor was carried out by our newly founded Production Group under the charge of Sir Christopher Hinton, which had centred itself in Risley in Lancashire. By the time BEPO was critical in July 1948 the experience gained in building it had been used to design the two Windscale Atomic Piles which were built as plutonium producers for the military programme. Simultaneously with this the Production Group built the chemical separation plant at Windscale.

After dealing with the problems of Windscale our thoughts and energies turned to nuclear power and many different ideas for power reactors were put forward. After the experience of building BEPO and Windscale the idea of a further development of the gas cooled reactor was fairly obvious. It was decided to enclose a graphite reactor in a steel pressure drum and to remove the heat by circulating carbon dioxide gas under a pressure of 7 atmospheres. This enabled 10 times as much heat to be extracted per ton of uranium as in the case of BEPO. We also learnt from Chalk River experience with NRX that it ought to be possible to leave fuel elements in the reactor until heat equivalent of 10,000 tons of coal had been extracted from each ton of uranium. Remarkable to relate, this figure has remained ever since as a target to be aimed at in our power stations of the future. In September 1950 a conference was held at Harwell and our engineers presented figures to show that it should be possible to produce power for less than 12 mils a unit. This was the first detailed assessment which had so far been made of possible costs.

Intensive work then proceeded at Harwell on the development of the technology of this particular reactor system. We had to find out how to treat uranium metal to make it dimensionally stable at temperatures above 400°C; we studied the design of the surfaces of the sheaths of the uranium metal to improve the heat transfer. This showed that quite high heat transfer rates were possible, a point which was not understood by our U.S. friends for several years. We also studied the reactor physics of the system and made sure that the hot carbon dioxide gas would not react too violently with the graphite. By the end of 1952 the feasibility study had shown that a nuclear power station could be built to develop 50,000 KW of electricity and that it could produce substantial quantities of plutonium as a by-product. About this time military demands for more plutonium were made and it was decided that the Production Group should design and build the Calder Hall nuclear power station, as a dual purpose plant. After a tremendous effort the first reactor went critical three and a half years later. Since that time the first Calder Hall power station has generated 1.36 billion units of electricity, and it has become the prototype from which has developed the U.K. programme to build 5,000-6,000 MW of nuclear power stations by the end of 1966.

During this time Harwell has been continuously concerned with the problems of the future nuclear power stations. It has been necessary to carry out detailed studies. on the nuclear design of the graphite uranium lattices to achieve maximum efficiency and this has been done in collaboration with the Industrial Groups who are designing and building these stations. Our BEPO reactor has been used to study the reaction of the hot carbon dioxide gas with the graphite at the higher temberatures they will operate. Experimental work is also carried out in our ancient GLEEP reactor to check the burn-up we should achieve in our power stations. Our chemists work on the problems of disposal of radioactive waste. Our metallurgists work on the problems of irradiation damage of the fuel elements.

During this period we have reinforced the reactor testing facilities by building the twin heavy water reactors DIDO and PLUTO. Like NRX they were designed to operate at 10 MW of heat, but like the NRX they will exceed this by a handsome margin. Due to the high intensity of irradiation in their cores they will enormously accelerate our experience of the effect of reactor radiations on fuel elements and metals of construction, and are now turning out results which will save millions of pounds.

During our twelve years of existence we have equipped ourselves to be one of the leading centres of nuclear measurements in the world. We developed at Harwell the first of the electron linear accelerators in which electrons are made to surf ride along the crest of a travelling electric wave. The wave speeds up and so do the electrons. We now have a high intensity accelerator of this kind which produces 30 million volt electrons. Five British hospitals have now installed 4-million-volt LINACS for treatment of cancer. The record for this type of accelerator is however now held by the University of Stanford which has built a LINAC for 700 MeV and has recently been almost promised 100 million dollars to build one two miles long to produce ultimately 45 billion volt electrons. This is one modest by-product of the early Harwell research.

We have used our LINAC to produce extremely powerful beams of neutrons to study nuclear constants important in our reactor programme. This is however only one of four or five powerful nuclear tools we use for such work.

In our chemical and metallurgical laboratories we first produced plutonium metal in the U.K. This began again as a co-operative Canadian/U.K. effort when a Harwell chemist went to Chalk River and there produced a small pin-point (a few mg) of plutonium which showed that the process we envisaged was viable. Returning to the U.K. the process was scaled up several times in successive orders of magnitude and culminated in the production of about 200 grams of plutonium metal in December 1951. By this time we were ready to hand over the process to the Production Group and we have since turned our plutonium effort to work on plutonium ceramics and alloys which may be used to enrich future power stations and to provide fuel charges for the fast reactor power programme of the future.

We have also again in collaboration with Chalk River extracted some of the elements heavier than uranium and have produced quite visible quantities of Californium and Curium for experimental work.

We have from the beginning devoted a substantial effort to producing and processing radioactive isotopes and our sales now approach a million pounds a year. The isotopes are produced in BEPO or DIDO or in Calder Hall. If they require chemical processing they go to our Radio Chemical Centre at Amersham where they are incorporated into a very wide range of compounds. A particularly important series are the organic molecules in which radioactive carbon has been substituted for normal carbon in one or more of the positions in the molecules. They are now amongst the most important tools of the biochemist. We have recently added to our products, sources of radio-cobalt in units of 100 thousand curies and can even contemplate selling million curie sources in the future. This is a remarkable change from Rutherford's days when he thought he was very fortunate to be able to get the equivalent of half a curie of radium on loan from the Vienna Academy of Sciences.

We also have a very flourishing Isotope School which accommodates sixty pupils in a three months course. We have also established an Isotope Research Division at Wantage Radiation Laboratory where researches into new applications of radio-isotopes are carried out. Work at these laboratories established an economic basis of using radio-cobalt for the sterilisation of wool fibres used for carpet manufacture. We have also been responsible for establishing the first Regional Training School for the application of isotopes in the Middle East, first at Baghdad and now in Tehran. In successfully doing this we have anticipated the work of other international organisations by at least four years.

As a result of developments worked out at Harwell, British Industry has now a wide range of radio-isotope aids to production-thickness gauges for steel, brass, polythene, tissue paper, tin on tinplate and so on. Our isotopes are also extensively used for radiography of welds, for the elimination of static, for assistance to the oil industry and a wide variety of other applications. We believe that these applications are now saving British Industry many million pounds a year.

Research into the possibility of obtaining power from the fusion together of the light elements is one of the most exciting though long-term projects at Harwell. The sun and stars derive their energy mainly by the fusion together of hydrogen nuclei to form helium. In the fusion process matter disappears and is converted to energy and this provides the heat of the sun which makes life possible on the earth. So the sun has been gradually burning up its hydrogen for the last ten billion years.

It is natural therefore with Science's increasing command over Nature that we should emulate the sun and try to make use of the fusion reaction on earth to produce heat and electricity. We are pretty certain we could do this if we could heat up a gas consisting of a mixture of the two heavier isotopes of hydrogen-deuterium and tritium--to a temperature of about 50 million degrees. We can devise means of heating the gas but the problem is to contain the hot gas since material walls would obviously melt long before these temperatures were reached. The only feasible method would appear to be to contain the hot gas in a so-called 'magnetic bottle' in which the magnetic lines of force, visualised by Farady for the first time, act like material walls because we are trying to contain a gas in which all the particles carry electrical charges. The result of this is that when a particle tries to cross lines of force it is acted on by a force which causes it to spiral round the magnetic lines of force instead of crossing them. Various forms of magnetic bottle are being tried and it is too early yet to say how leak-proof they can be made.

At Harwell we have used aluminium donuts of steadily increasing size wrapped round with coils to produce a strong magnetic field. This process culminated in our ZETA donut which has a bore diameter of one metre. In ZETA we heat up the gas by passing currents of up to 900,000 amperes through the gas. The great achievement by ZETA was to increase the temperature of the gas from 500,000 degrees or so in previous donuts by 5 million degrees. With the typical cussedness of Nature however when we reached this point the magnetic bottle began to become leaky. As we fed in more energy by putting up the current through the gas, the temperature stopped rising and we found that the energy was escaping in various ways. We are now using ZETA as a research tool to find out exactly why and how this is occurring. For if we can understand it we have a chance of stopping it.

The situation seems to be that the hot gas developed instabilities as we reached interesting temperatures and pressures and the small instabilities grow until the hot gas breaks through the walls of the magnetic bottle so that its energy is dissipated. We are now studying this misbehaviour whilst at the same time planning to build a new ZETA-like apparatus we call ICSE which should, we hope, behave better. We are however in the stage of basic research into Plasma Physics and we are somewhat far away from being able to design a fusion power station. If in due course we succeed, fusion power would assure mankind of inexhaustible power so long as he survives.

Harwell has from the beginning been an important centre of research into the biological hazards of Atomic Energy. When I worked in the Cavendish Laboratory in the 1930's on the transmutation of atomic nuclei we used to judge somewhat empirically the intensity of the radiation to which we were exposed by holding up a screen covered with zinc sulphide which glows under irradiation. If it looked too bright we added another millimeter thickness of lead to our protective cabin. Somewhat similar methods were employed in the Montreal Laboratory in 1943--workers with Polonium used to take it into a dull room to see whether it glowed. If so it was getting dangerous. If it smelt of ozone it was very dangerous. When I went to Canada in 1944 I was fortunately joined by two eminent U.K. radiobiologists who at once proceeded to lay a sound scientific basis for protection of human beings against radiation.

We started to use geiger counters and built other elegant instruments using quartz fibres to measure the intensity of radiation to which we were exposed, and in this way we ensured that we kept well below the radiation dose which our biological friends specified as the maximum permissible limit.

On our return to U.K. the Medical Research Council established a radio-biological research unit at Harwell which has been a centre of radiobiological research ever since. We now have a much better quantitative idea of the amounts of radiation which will harm human beings though this is still a fairly wide bracket in the quantitive figures. It takes a long time and a lot of animals to test the effects of the very small doses of radiation we are exposed to in normal operation. At the present time workers with radiation have a yearly maximum ration of radiation and also a 10-year ration and a life-time ration. All workers carry photographic films which add up their weekly dose. By such means we achieve good radiation protection.

We also concern ourselves with the measurement of fallout and of contamination by disposal of radioactive effluents. By this means we make our contribution to the studies of the Medical Research Council and the U.N. Radiation Committee whose job it is to evaluate radiation hazards.

The main difficulty facing such bodies is that experimental evidence on the effects of very low doses of radiation takes a very long time to acquire. We therefore have to take a conservative view of induced effects.

THANKS OF THE MEETING were expressed by Lt.-Col. Bruce J. Legge.