GENERATION
Klaus Fuchs, nuclear spy extraordinary
and the end of “Modus Vivendi”
by CM Meyer, technical journalist
This is the first part of a series of articles that will be published in Energize tracing the history of nuclear energy throughout the world.
The first step towards nuclear power.
“Then one day, in February or March 1940,
Frisch said “Suppose someone gave
you a quantity of pure 235 isotope of
uranium – what would happen?”
[Peierls, 1985: 153-154]
University, who “promised to get it to the right
person.”
The answer theoretical physicist Rudolf Peierls
sat down and worked out with Robert Frisch in
Birmingham in early 1940 astounded them
both. Only “about a pound” of uranium235 would be necessary to release a huge
amount of energy, as Peierls later put it in his
autobiography, “the equivalent of thousands
of tons of ordinary explosive.”
The memorandum arrived just in time: the British
government committee concerned with the
possibilities of a nuclear chain reaction had
seen no possibilities in this (they had been
investigating natural uranium, not uranium235), and was just about to disband. Instead,
this memorandum galvanised them into the
first research aimed at using nuclear energy,
then focused on the first atom bomb. Ironically,
this step had been taken by Peierls, a German
immigrant married to a Russian wife, both of
whom had only recently been naturalised as
British citizens.
His estimate of the critical mass of uranium235 later turned out to be too low (the actual
critical mass is said to be more than 15 kg
[Rhodes,1996: 48], but it was of the right
magnitude. Thus, the first step towards the use
of nuclear power – and the first atom bomb
– was taken in Britain in 1940, when Peierls and
Frisch summarised their findings in a secret
memorandum.
Like Peierls, Robert Frisch was also a German
immigrant. The nephew of the physicist
Lise Meitner, he had fled Germany with her.
Together, they had estimated the energy
released by fission (the splitting of the uranium
atom: Frisch was the first to coin the term
“fission”). Fission had then only recently been
discovered: in 1939, by Hahn and Strasman
in Berlin.
Neither of them knew how to write a secret
memorandum – or who to give it to. After some
thought, they gave it to Prof. Mark Oliphant,
then in charge of physics at Birmingham
The reply Peierls and Frisch received was typical
of the time. It went something like this: the
authorities were grateful for the information,
but they would have to understand that,
as they were considered “actual or former
‘enemy aliens’”, the work would be continued
by others, and that would be the last they
would hear of it.
But, fortunately for the allied war effort, Peierls
did not accept this nonsense. He wrote to the
chairman of the committee (whose name he
did not yet know), pointing out that he and
Frisch had thought “a great deal” about many
of the problems associated with releasing
nuclear energy, and “might well know the
answers to important questions”. Common
sense won, and Peierls and Frisch were placed
on the subcommittee that started the first work
on the atom bomb.
However, common sense is not very common,
especially in wartime. Frisch, still classed as
an “enemy alien” even after he had later
moved to Liverpool to start work on the atom
bomb project, found he needed a permit
to live there, and even special permission to
own a bicycle and ride around in the evening
(Peierls, 1985: 152-156, 159).
Research for MAUD
“Even if this (uranium-235 enrichment) plant
costs as much as a battleship, it would be worth
having” Peierls and Frisch discussing the value
of an enrichment plant to produce uranium235 [Peierls, 1985: 154]
Today, with the United States being the
leading superpower, especially in nuclear
technology, it is hard to believe that research
on nuclear power and the atom bomb started
in the United Kingdom. But it was in the United
Kingdom that many of the key ideas and
concepts for this first took shape. Later, it was
the huge manufacturing base of the USA that
transformed these concepts into practical
realities: and the first atom bomb.
The work Peierls handled for the committee
was growing rapidly. By now, the committee
had the strange code name MAUD (to hide
its purpose). Later, the research was named
“Tube Alloys”: another deliberately meaningless
name to hide its purpose.
Klaus Fuchs, the quiet man on the extreme left, at Harwell in 1949. Next to him are
Herbert Skinner, a close friend, Bruce Chalmers, Harold Tongue, Egon Bretscher,
Robert Spence and Sir John Cockroft, the Director. Photo: Courtesy of UKAEA.
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Peierls had been getting more and more
problems to solve. Very early on, when doing
the first rough calculations on the critical mass
of uranium-235, he saw the need for a process
to separate uranium-235 from natural uranium
(only one atom in 140 of uranium is uranium-
GENERATION
235, the rest are atoms of uranium-238). He
soon realised that the only possible way of doing
this would be to convert the uranium to uranium
hexafluoride, a highly corrosive gas, and in some
way use the difference in physical properties of
the two isotopes to separate them.
At first he thought of thermal diffusion, which
did not work. After further discussions, Peierls
and Frisch decided that “the most promising
method was to use gaseous diffusion through
membranes with fine pores”. This idea later
became the huge gaseous diffusion plant set
up at Oak Ridge, Tennessee, in the USA. From
this came uranium-235 (eventually at the rate of
100 kg per month (Rhodes, 1996: 192)), used for
the first atom bomb to be dropped on Japan,
on Hiroshima on 6 August 1945.
Later, also in Britain, theoretical work by Feather
and Bretscher in Cambridge showed that “the
new element, plutonium, which resulted from
the capture of neutrons by uranium-238 in a
slow-neutron chain reaction, might be as good
a nuclear explosive as uranium-235, or better”
[Peierls, 1985: 160]. Later, once huge reactor
facilities had been set up at Hanford in the USA,
plutonium was also produced in large enough
amounts, (eventually at the rate of 20 kg per
month (Rhodes, 1996: 192)) to make atom
bombs, including the one for the very first test
and the one later dropped on Nagasaki, Japan
on 9 August 1945.
But, in those early days, more and more crucial
work was being handled by Peierls. He therefore
needed an assistant, and he thought of Klaus
Fuchs. Like himself, Fuchs was a refugee from
Hitler’s Germany and a theoretical physicist of
considerable promise.
At the time, Fuchs seemed a good choice.
But, eight years later, Peierls was to bitterly regret
that he chose Klaus Fuchs to work on nuclear
energy.
The man who stole nuclear energy
“He is the only physicist I know who changed
history,” Hans Bethe, head of theoretical
research at Los Alamos, commented on Klaus
Fuchs [Rhodes, 1996: 259]
Klaus Fuchs not only made nuclear history, he
also changed it. One of the less well-known
results of his work, both as a scientist and as a
spy, is that Great Britain was unable to access
American reactor technology when planning its
first power stations, and was forced to develop
gas-cooled reactors.
Dr. Klaus Fuchs is better known as the man who
gave the most sensitive secrets of the atom
bomb to the then Soviet Union at a critical time
in world history, enabling the Soviets to save an
estimated two years in their race to develop
nuclear weapons. Some blame him for the
Korean War, saying Stalin would never have
dared to support North Korea in 1950 without
having the atom bomb, and that Fuchs’s inputs
were crucial.
To begin to understand why the US and
Great Britain followed different routes to
nuclear power stations after World War Two,
we must first understand something of Klaus
Fuchs. As we shall see, Fuchs was not only
spying for Russia but also for Britain, and
he actually played a key role not only in
developing the first atom bomb, but also in
early work on the first hydrogen bomb.
Klaus Fuchs was born into a family where the
father, Emil Fuchs, encouraged his children
to stand up for their own beliefs and go their
own way. His early life was not as happy as
he later described it, as his mother committed
suicide while he was quite young, and one
of his two sisters, Elizabeth, later killed herself
by jumping into the path of an oncoming
train. His other sister, Kristel, who emigrated
to America, had to be hospitalised at one
time because of mental illness.
As a student in Hitler ’s Germany, Fuchs
became increasingly drawn to the left.
Active in politics, he first joined the SDP (Social
Democratic Party) while studying at Leipzig,
and then later the Communist Party while
a student in Kiel. He also turned against his
father’s pacifism (his father was a minister,
later becoming a Quaker). At Kiel, as a
student leader, he displayed considerable
courage by actively taking a public stand
against the Nazis, and later having to flee
for his life. He reached Britain as a refugee
in September 1933, later being accepted
by professor Nevill Mott as a PhD student at
Bristol University.
After graduating, he went to work for
Prof Max Born in Edinburgh, publishing several
research papers and earning a DSc as a
research assistant. Then, in little more than
three weeks (between 10 and 30 May 1940),
Nazi invasions conquered three countries:
Holland, Belgium and France.
Many in authority in Great Britain could not
understand that German military skill and
advanced strategies had made these rapid
victories possible, and instead blamed
German agents: and, indeed, any Germans
and Italians they could find. This meant, in
Britain, a wave of hysteria and a rush to classify
and intern the 27 000 Germans and Italians
then living in Britain (many of them refuges) as
enemy aliens, and get as many as possible
out of the country.
Classed as an enemy alien, Fuchs was
arrested in May 1940 without being able to
inform Born of his plight. He was deported by
ship to Canada, where he was interned: in the
same camp as several Nazi’s. Clearly, in this,
he saw a side of Britain that he did not like.
Eventually, Born managed to intercede for
Fuchs, and get him reclassified and returned
to Britain on 17 December 1940. Fuchs was
working under Born when Peierls offered him
work (Rhodes, 1986: 56-57).
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GENERATION
Fuchs accepted, and started work in May 1941,
having no problems on working on a possible
atom bomb (Peierls, 1985: 163). But, on
22 June 1941 something happened that
changed his life: Germany attacked the USSR,
and the Soviet Union was soon engaged in a
grim struggle for survival: a struggle that, at
least for the first six months, it appeared to be
losing. Fuchs decided, without any prompting
from anyone, that the work he was doing
could help the Soviet Union militarily, and that,
as a communist, it was his duty to inform the
Russians. More importantly, he later decided
to keep the Russians informed after he had
moved with Peierls to the USA, to start work on
the top-secret Manhattan Project.
Thus, a few months after Fuchs started work for
Peierls, in late 1941, he had also started work
of a very different kind: as a spy supplying
information to Soviet Military Intelligence, the
GRU.
The beginnings of Harwell
“The British flew rather than shipped Fuchs home
(after the war in a British bomber) because they
wanted him promptly at Harwell…(they) were
preparing secretly to build their own atomic
bomb, and what Fuchs knew was valuable to
them. He thus became a vector for nuclear
proliferation to England as well as the Soviet
Union.” [Rhodes, 1996: 259].
Today, when some parts of the former topsecret atomic research centre at Harwell have
been demolished to make way for a business
park, it is difficult to understand the excitement
when it was first founded after World War 2.
When Klaus Fuchs arrived there in 1946 as head
of the theoretical physics section, there was
huge excitement at the prospects of nuclear
power: and nuclear weapons. Japan had
just been forced into surrender by two atomic
bombs, World War 2 was finally over, and Britain
was secretly preparing to make its own atomic
weapons: and develop peaceful applications
of nuclear energy.
Fuchs had distinguished himself in the top-secret
wartime Manhattan project, where practical
atomic weapons had been developed in
the USA and Canada from British research
coordinated by the MAUD committee. He
had been at the heart of work to solve some
of the most difficult problems to produce a
practical nuclear weapon using plutonium,
and helped very considerably to solve the
problem of implosion.
Making a nuclear weapon out of uranium235 is, as historian Richard Rhodes ably
explains, comparatively simple. Two pieces
of uranium-235 each below the critical mass
are carefully machined so as to fit perfectly,
and then placed at opposite ends of their
bomb. When detonation is required, one part
is blasted into the other by high explosive: the
so-called “gun design”, used in the first atomic
bomb dropped on Hiroshima, Japan. The
uranium mass exceeds that of critical mass,
goes critical, and a nuclear explosion results
[Rhodes, 1996: 115-116] [Peierls, 1985: 199].
But, the same design cannot be used for
plutonium. Because plutonium can undergo
spontaneous fission something like ten times
as easily as uranium-235, a “gun-design”
bomb using plutonium would start to detonate
(predetonate) before the two pieces had
reached each other, and would blow apart
before most of the plutonium had a chance
to fission [Rhodes, 1996:115- 117].
The only practical way researchers at the
Manhattan Project found to detonate a
plutonium bomb was using implosion. Here, a
small, central ball of plutonium (below critical
mass) was surrounded by a hollow sphere of
plutonium (also below critical mass). This hollow
sphere, held in place by wires, was covered
by special shapes of high explosive, called
“lenses”. When the time came to detonate the
bomb, electronic detonators in each lens were
set off within microseconds of each other, in a
carefully calculated sequence. This sequence
then resulted in a powerful shock wave that
compressed the plutonium into a ball greater
than the critical mass: but so quickly that the
plutonium did not have time to predetonate
[Peierls, 1985: 199-200].
The correctness of this design was tested on 16
July 1945, when the first ever nuclear bomb
was detonated, and later used on Nagasaki.
Fuchs had extensively studied implosion, and
wrote no fewer than seven secret research
papers on it. He also knew many other aspects
of producing nuclear weapons, and knew of
the earliest theoretical resarch on a possible
hydrogen bomb [Rhodes,1996: 118-119,
252-254]. While in the USA, he had kept the
Soviets informed of the most significant work
done at Los Alamos: including a plan of an
actual plutonium bomb and very detailed
background information.
Small wonder that, at Harwell, he was placed in
charge of theoretical aspects to develop the
British atomic bomb. But, even though Fuchs
worked diligently at Harwell, he continued to
supply the Soviets with information.
Unknown to him, the defection of a cipher
clerk, Igor Gouzenko from the Russian Embassy
in Canada in 1944, had started a chain of
events that would ultimately lead to his work
as a spy being discovered: and to a crisis in
Anglo-American relations that would affect
British nuclear research profoundly.
The Modus Vivendi agreement between
the USA and Great Britain
“The Joint Chiefs (of Staff in the USA) decided
that the United States could use no more than
150 ‘Nagasaki type’ bombs (against Russia
in 1947), basing that number on a Pentagon
study that envisioned ‘attacks on approximately
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100 different urban locations’ in the USSR”
[Rhodes, 1996: 298]
By the end of June 1947, both the UK and the
USA had made embarrassing discoveries. Great
Britain would, in a few months, be out of dollars.
In technical terms, this meant that in a few
months, the UK would have only $500- million
left of the original US loan of $7,5- billion, and
would be practically bankrupt.
The United States, in turn, was desperately
short of uranium. There was not nearly enough
uranium for reactors at Hanford to generate
the plutonium needed to produce the 150
‘Nagasaki type bombs’ it needed for its national
security. With less than 1,5-million men under
arms, the USA was now relying on atom bombs
to fill in the gap against the Soviet Union: by
then the USSR had more than five million men
under arms and was perceived as an increasing
threat.
In 1946, the MacMahon Act had been passed
by Congress, transferring control of atomic
research from the US Military to the Atomic
Energy Commission (AEC). In it, supplying
information about nuclear weapons and
reactor technology to foreign countries was
prohibited. Only after the act had been passed
and signed into law did senior congressmen
and senators become aware of the secret
wartime Quebec Agreement of 1943. In this
agreement, Great Britain, Canada and the
USA had agreed not to use the atom bomb
against each other - and for Britain to have a say
(effectively a veto) on targets the atom bomb
was to be used against. This had worked well
when the war against Japan was still ongoing,
but key members in the AEC were appalled at
the prospect of Britain vetoing American use of
the bomb: especially now it was the cornerstone
of US defence policy.
There was also the question of the world’s richest
supply of uranium ore, produced in the then
Belgian Congo. Although Great Britain had
paid for half of all the uranium ore, it had all
gone to the USA while the Manhattan project
was operational. But, when the war ended,
and the British wanted to start their own nuclear
programme, half the uranium produced
had once more gone to Britain, where it was
stockpiled.
Huge pressure was brought to bear against
Britain by the US: in exchange for Marshall aid
(in essence, dollars to stave off their looming
bankruptcy), Great Britain was forced to yield
up its veto, once more allow all uranium ore to
go to the USA, and give up its uranium stockpile
to the United States.
This agreement, known as the “Modus Vivendi”
(literally, way of co-existing) was duly signed on
7 January 1948 after some tough negotiations,
and was to last until the end of 1949 [Rhodes,
1996: 300-301]. The agreement did mean that
Great Britain had to postpone its programme to
develop nuclear weapons by some years. But
GENERATION
it did allow Britain access to nuclear reactor
technology. That is, until the news broke of
Fuchs’ spying activities in January 1950.
The end of the modus vivendi and British
access to nuclear reactor technology
“Then a bomb exploded in London. A
British scientist – Klaus Fuchs, who had been
working in this country (the USA) on the
Manhattan Project during the war – was
arrested…..and later tried and convicted.
Also, in February, Senator Mc Carthy began
his attacks on the State Department. The
talks with the British and Canadians returned
to square one, where there was a deep
freeze from which they did not return in my
time (1949-1953 as Secretary of State)”. Dean
Acheson, US Secretary of State 1949 - 1953
[Moss, 1987: 169].
In November 1949, shortly before Fuchs was
arrested, a meeting was held of the little-known
Combined Development Agency in the USA.
Present were representatives of Great Britain,
the USA and Canada. Although the meeting
was technically held to discuss uranium
supply, the discussions centred on a far more
important topic.
For the first time since the signing of the secret
Modus Vivendi nearly two years ago, something
better seemed in the offing. An invitation
had come to Britain to increase nuclear
cooperation to something approaching the
level that existed during World War 2. Knowing
that Britain wanted to develop nuclear
weapons, Dean Acheson, the US Secretary
of State, wanted to improve the working
relationship with the UK, and had arranged for
a proposal for both countries to share research
and development in all aspects of nuclear
research [Moss, 1987: 168-170].
Acheson had good reason to improve relations
with the British. Only some three months
earlier, the Soviet Union had exploded its first
atom bomb (on 29 August 1949) [Rhodes,
1996: 365-6], and the communist forces of
Mao Zedong had seized control of China
(forming the PRC on 1 October 1949). But
Acheson had not reckoned on Klaus Fuchs!
At first, everything went very well. The Americans
were receptive to the British proposals, and
it looked like the US Congress could be
persuaded to change the MacMahon Act that
denied the UK access to the technology it so
desperately wanted.
And then, in January 1950 came the news
of Fuchs’ arrest, and the shattering news of
all he had given to the Russians (for which he
received a sentence of 14 years in jail).
The next month, Senator McCarthy started to
stir up anti-communist hysteria, culminating
three years later when J Robert Oppenheimer,
who had directed the scientific side of the
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Manhattan Project was accused of being
“another Fuchs” [Rhodes, 1996: 530].
Later in 1950 the Korean War started, probably
as a direct result of the USSR having the bomb.
It took some four years for the hysteria to
subside and nuclear cooperation between
the USA and Great Britain to resume.
But the damage was done. The Modus Vivendi
had expired, with nothing to replace it. As
Acheson put it, there was now a “deep freeze”
that he could do nothing to change. And this
had considerable implications for nuclear
power generation. This as secret work was
then starting in the USA, and was to lead to the
development of new technology (pressurised
water reactors) to power submarines. This
technology was denied to the United Kingdom
(see parts 6 and 7 in this series “The long
shadow of Admiral Hyman Rickover”). This
ultimately forced the British to develop gascooled reactors (see part 8 in this series, “From
MonteBello to Magnox reactors”).
References
[1]
Moss, N (1987). Klaus Fuchs – the man who
stole the atom bomb. London: Grafton
Books.
[2]
Peierls, R (1985). Bird of passage. Princeton:
Princeton University Press
[3]
Rhodes, R (1986). Dark sun: the making of
the hydrogen bomb. London: Simon and
Schuster. 