On September 27, 1956 the first explosion in a British series of atomic explosions took place at Maralinga, South Australia. This series of explosions was christened "Buffalo". Bruce A Bolt was on the Nullabor Plain as one of a group of seismologists making use of the British atomic test to study the earths crust. Seismographs were installed westward from the Maralinga test site along the railway line to Perth. Bolt had placed a seismograph at Cook, 140 kms from the shot point. See map.
Bruce A Bolt describes the location;
"The Nullabor Plain of Australia conveys an endless theme
of sparse vegetation, far horizons, and brooding emptiness. This
outback landscape appears, at first meeting, desiccated and monotonous.
The Plain is almost devoid of real trees; the struggle for life
is intense. Even the ubiquitous Australian eucalyptus, evolved
in endless variations to survive snow or aridness, is rare. However,
intimacy with the Nullabor reveals a different reality. The yellow
and browns of the soil, the sculpture mounds of sand and pebbles,
create a landscape of endless variety. In the gullies and clefts,
among the grey spinifex and mallee scrub one encounters bursts
of desert flowers: the purple of the desert rose; the scarlet
brilliance of the Sturt's pea, like drops of blood among its feathery
foilage; the greenness of a phyllodinous acacia, a few feet high,
with its flattened leafstalks evovled to reduce loss of water."
Sir William Penney arrived in Australia early September 1956 to supervise the tests. Penney was associated with British nuclear research since its early days; he had flown in an observation plane for the Nagasaki atomic bomb drop, he was also in Australia during 1952 for the Monte Bello test. Sir William stated at a news conference in Sydney that the tests would not involve big explosions, but that was not to state that small weapons would not have a tactical role to play during the times of war. The Maralinga tests would be for measurement research, others would determine the behaviour of military equipment and buildings when subjected to explosive forces.
With close cooperation with the British on defence matters the Australian government at the time was led by Prime Minister Robert Menzies. The opposition Labor party opposed Menzies Liberal party Country party policies on allowing the atomic tests in Australia. Deep divisions in the Labor party prevented much affective resistance, the Labor party caucas voted to only send a small group of observers to Maralinga.
Environmental hazards from the nuclear explosions appeared to be taken seriously by the Australian government and scientific circles. An Australian Weapons Safety Committee was established to examine the dangers from radioactive fallout and give the all clear on weather conditions for each test. The committee published open reports in the Australian Journal of Science. The articles explained the actions taken ensuring the safety of the public; these were similar to those already in place in the United States for air, tower and surface bursts in Nevada.
Arrangements were made for measurements of radio -iodine concentrations in the thyroid glands of sheep and cattle, where iodine in digested fodder is quickly concentrated. Radioactive levels were tested in rain, mud and water reservoirs. Sampling of radioactive dust was carried out by the simple method of exposing the sticky surface of gum films to the open atmosphere. By the time of the Buffalo tests of 1956, the Australian fallout network had been expanded to eighty-six stations.
The First Maralinga Explosion
The weather was at first unfavourable at Maralinga for the initial test in Spring 1956. Some 1500 scientists and soldiers were waiting for this first test.
On a clear spring day, the first explosion was ignited. Only near the detonation point was ground motion felt, but people living hundreds of kilometers away heard the sound waves through the air. At Cook two or three distinct blasts were heard about 12 to 13 minutes after the detonation flash. At Kingoonya, 400kms from Maralinga, there was an explosion like a clap of thunder, shutters rattled and houses shook. On the coast, 300kms away at Ceduna, two large bangs rang out- like sticks of dynamite going off.
The first atomic bomb in the Maralinga series was about equal in power to that which destroyed Hiroshima. The device had been suspended from a 110 metre tower. The most distant seismograph known to have recorded it was at Southern Cross, 1000kms away.
The fission detonation produced the usual fireball, flash and cloud. The cloud then became distorted by winds in the upper atmosphere, and it gradually drifted away to the northeast, over the empty desert. An hour after the explosion, news reporters flying over the site reported a shallow, ash grey crater, about 500 metres across. The tower had been vapourised, and smoking equipment dumps and burning scrub streched for over two kms.
Seismological Results Of The First Atomic Tests
The 1956 Maralinga seismological experiments proved as successful as the nuclear explosions themselves. A total of ten seismograms of importance were obtained from the four atomic detonations; the readings were used to determine for the first time the thickness of the Earth's crust in the Australian continent. The results of these seismological experiments concluded that the Western Australian crust had a thickness of around 35km in depth. The depth of crust and seismic properties were similar to other continental shield areas such as Canada, South Africa and Siberia.
After Maralinga
Things went off as the Australian government has assured the public they would. However, there were some sidelights which illustrate how irrational as well as rational fears are born following novel events. Some newspapers pointed to a correlation between the bomb detonation and weather changes. On September 28, the day after the first blast, freakish heavy rain fell in Sydney, Adelaide, and other places in Australia. In Australia's capital, Canberra, parliamentarians were given pause when, after more than three weeks of warm, sunny weather, there was a downpour during the night after the explosion.
Nuclear devices that are detonated above ground, as in the Maralinga tests, form a cloud that rises to between 7500 metres and 20,000 metres, depending on the size of the bomb and the weather. Heat in the fireball vaporises the unfissioned nuclear "fuel", metal casing and mechanism, and some nearby rock. The vapor rises like an aerosol spray, with the exceedingly fine particles remaining in the cauliflower like head of the cloud.
Heavier particles carried upward by strong turbulent updraughts just after the ignition are deposited within a few hundred kilometres of the blast, in the direction of the mean wind. Heavy radioactive contamination of the environment near ground zero occurs in this way. The lighter radioactive particles sometimes drift several times around the world, slowly falling to lower levels. When they reach rain clouds they are quickly transferred to the earth. In large atmopsheric detonations, radioactivity may be injected into the stratosphere, and may take several years to reach the ground.
For all atomic tests in Australia, the Safety Committee concluded in 1959 that the hazard to humans from the consequent radioactive fallout was of no consequence. They compared the increased dose of gamma radiation to the human body over fifty years with that normally experienced: The dose levels incuured are very small; without making allowances for the normal living and occupational habits of man, which can introduce as a correction factor a reduction of an order of magnitude, the dose levels involved are trivial compared with the natural background due to cosmic rays and natural activity". The highest value of the dose to humans from the radioactive contamination, assuming no shielding, was less than one percent of the annual natural background.
Worries about radiation produced by these relatively small fission devices fired above the ground in Australia in late 1956 were soon to be engulfed in a more serious concern. Widespread global increases in radioactivity had already been produced by atmospheric testing of gigantic hydrogen bombs by the Soviet Union, United States, and Great Britain. On September 18, 1956, the Radiological Institute of Freiburg University announced that the radioactivity level in grain fields and pastures in south west Germany had increased in the previous two months. This report and others began to speak of danger to human beings if such levels were increased.
Unknown to the participants in the Nullabor, on the day of the first 1956 Maralinga test, the National Weather Bureau in Tokyo released a startling report stating that radioactivity over Japan had increased considerably over the past months. There was a suggestion that increases in strontium 90 concentration in atmospheric dust over Japan constituted a hazard to health. The report referred to recent U.S. and Soviet tests of thermonuclear fusion weapons above ground.
In this climate, a number of us in Australian university circles began to study the questions of environmental risks arising from above-ground nuclear explosions. It was difficult to be cooly academic with the titanic race in nuclear armaments going on between the great powers.
Particpation in Maralinga also set me thinking about new seismological questions. We had proved that unnatural earthquakes could provide seismic waves from which it was possible to make strong inferences about the structure of the Earth. What more could be done? How similar to were nuclear earthquakes to natural ones? Soon the realisation that the testing of nuclear weapons would force seismology to expand from a small, rather obscure discipline to one that would play a key social role. By the late 1950's, many seismologists had become aware that their energies and talents would be called upon to help solve one of the key scientific dilemmas of the second half of the 20th century.
The problem was as follows: if atomic weapons tests were banned under international treaty, could a nation that wished to violate the treaty do so without being detected? Seismologists had developed methods of recording waves from natural earthquakes from all around the world. They also had experience with recording waves at short distances from chemical explosions, such as quarry blasts. Could seismology alone be relied on to provide the means of detecting the differences between natural earthquakes and unnatural ones fired off secretly within the Earth's crust?
Finally
The British tested only three more atomic devices at Maralinga. In operation Antler two weapons were fired on towers and one suspended from balloons. The 1957 tests were also used for furthur geophysical measurements of the South Australian crust.
Prediction that Maralinga would become a permanent British nuclear testing ground were wrong. The changing climate of opinion in Australia and Britain, together with international pressures, was effective in preventing further testing on Australian territory. The Maralinga facility was returned to the emptiness of the outback.
With the passage of years, Australia took a more jaundiced view of above ground nuclear explosions. The government became troubled particuly about explosions in other parts of the Southern Hemisphere. After 1968, Australian objections to French nuclear weapons tests east of Tahiti grew in intensity. By 1973, opposition had grown to the point that the newly elected Labor governments of Australia and New Zealand brought a case before the International Court of Justice challenging France's right to carry out atmospheric tests in the South Pacific
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This information correlated on this page was derived from the chapter "The Field Of Thunder" pages 1 to 18 of the book "Nuclear Explosions And Earthquakes, The Parted Veil", written by Bruce A Bolt, 1973.
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