History of Nuclear Engineering Part 1: Radioactivity

For just over 100 years, radioactive elements have proved of industrial and commercial use. Martin Pitt charts their emergence

IN THE chemistry lab, I sometimes admired uranium solutions when sunlight caught the bottle, giving a green fluorescence to the yellow liquid. A similar effect was exploited by Czech glassmakers with the same colours. They added some useless black rock the miners called pechblende (bad luck ore) found among the silver ore at Joachimsthal (Jáchymov today). Known as pitchblende in English, its key component is uranium oxide. This art glass was popular in North America and Europe in the 19th and early 20th century, being particularly striking under ultraviolet light.

In 1789, German chemist Martin Klaproth (1743–1817) determined that pitchblende contained a new element, which he called uranium, after the planet Uranus, discovered in 1781. He also experimented with it in glass, probably provoking the trend.

In 1841, French chemist Eugène-Melchior Péligot (1811–1890) produced the first sample of the metal and developed its chemistry. Uranium compounds had some use in analytical chemistry. The metal was heavier than lead, but less inert and more expensive to make so had no commercial applications until much later.

French physicist Antoine Henri Becquerel (1852–1908) was interested in light-emitting compounds (phosphorescent and fluorescent) and wondered if they had anything to do with the newly discovered X-rays and cathode rays, so placed samples of the substances on top of photographic plates wrapped in black paper. Only the uranium compound blackened the plate. In 1896, he published seven papers on the topic, showing that non-fluorescent uranium compounds and the metal had the same effect, and concluded that there were invisible rays emitted. The becquerel Bq is now the SI unit of radioactivity.

New elements

Polonium

The weak “uranic rays” were of little interest to the scientific community excited by X-rays and cathode rays. However, in Paris, Polish chemistry PhD student Marie Skłodowska Curie (1867–1934) was intrigued and took it for her thesis. She used an instrument invented by Pierre Curie (1859–1906) (whom she had married in 1895) called an electrometer to measure the effect of these rays on the electrical properties of air and worked through the elements one by one. She discovered that thorium had a similar but weaker effect, which she called radioactivity, a property of the atoms, not compounds. She discovered that pitchblende was four times more active than the uranium content would indicate. As she had tested all known elements, there must be a new one present. With help from Becquerel, the pair found funding and a workplace to commence a heroic study. The Austrian government provided a tonne of pitchblende, hoping to find a use for this industrial waste (Joachimsthal was then part of Austria.) It was hard, manual work, dissolving 20 kg of rock in a large vat, which they took in turns to stir with a huge rod, then gradually refined to bucket scale and separated down to beaker and test tube to produce tiny amounts of compounds.

The first discovery was vastly more radioactive than uranium, named polonium by Marie after her native Poland, being chemically virtually identical to bismuth. Its low concentration and short half-life meant that she could not isolate it, and there was no practical use. Her daughter Irene Joliet-Curie was supplied with a sample solution in 1946, which was produced by neutron bombardment of bismuth. Unfortunately, the flask exploded which may have contributed to her death from leukaemia ten years later.

The first discovery was vastly more radioactive than uranium, named polonium by Marie after her native Poland...Its low concentration and short half-life meant that she could not isolate it, and there was no practical use

Radium

The second element, radium, was like barium, so coprecipitated, and was then separated by tedious fractional crystallisation, as the chloride. In 1898, spectroscopy confirmed it was a new element. It had taken three years to produce one-tenth of a gram of radium chloride from a tonne of ore. The Curies observed a faint blue glow from ionised air on the surface, since it was 2.7 million times as radioactive as uranium. The unit of radioactivity was originally defined as that of 1 gram of radium and called the curie (Ci). This is a huge unit, equal to 3.7 GBq, so microcuries were more often used.

Sadly, Pierre died in a road accident after falling under the wheels of a carriage in 1906. Marie produced the metal by electrolysis five years later.

In 1913’s The Patchwork Girl of Oz, best-selling US children’s author L Frank Baum (1856–1919) introduces the Horners, who mine radium and line their houses with it, giving a beautiful soft light. According to Chief Horner: “It is a medicine, too, and no one can ever be sick who lives near radium.”
It’s in complete contrast to the reality but how had this happened?

Henri Becquerel had close contact with the Curies and obtained an early sample of radium chloride which he placed in the pocket of his waistcoat. He developed a radiation burn but reasoned that it might do the same for tumour cells. The Curies confirmed it destroyed cancer cells faster than normal ones, so was successful under careful medical supervision. King Edward VII (1841–1910), was cured of skin cancer of the nose in 1907 with radium chloride. Marie Curie was horrified when various supposed medical and beauty products were produced, claiming to cure a wide range of non-cancerous diseases and improve health in general.

Joachimsthal grew into a fashionable spa where the wealthy came to bathe and drink its radioactive waters at the Radium Hotel. The main source of uranium in the world from which radium could be extracted, it was only the outbreak of the First World War that encouraged searches for ores elsewhere. The US was interested and founded the scientific journal Radium in 1904. Not wishing to be limited by imports, it discovered its own uranium source in a mineral called carnotite, a uranium vanadate, in Colorado.

From 1917, the Radior company of London produced a whole range of cosmetics guaranteed to contain measurable quantities of radium (unlike many of their competitors, they stressed). In France, Tho-Radia products (thorium and radium) proudly included the name of Dr Alfred Curie on their packages, though he had nothing to do with Marie and Pierre.

American champion golfer and influencer of the time Eben Byers (1880–1932) swore by his daily drink of Radithor containing a microcurie each of both radium and thorium. Byers reportedly drank as many as three bottles a day, amounting to nearly 1,400 bottles before he realised the radioactive water was rotting his body from the inside. Eventually, minus a jaw, which had decayed and with holes forming in his skull and abscesses on his brain, Byers died of multiple cancers. He was buried inside a lead-lined coffin designed to absorb the radiation (Marie Curie’s body was also deemed dangerously radioactive when she died of aplastic anaemia).

A major (genuine) use was for a paint which glowed green in the dark. This included radium chloride and zinc sulphide (which actually provided the glow when activated by the radiation). Radium art was a fashion before the Second World War, with glowing paintings, jewellery, and other display items. Tins of paint were sold to the general public to paint door handles, telephones, and even slippers, to find them in the dark. Safety-conscious organisations used them to indicate fire exits. The military were particularly keen on instruments which could be read in the dark, while the public could buy clocks and watches with radium dials.

The US Radium Corporation employed 4,000 women at its factories from 1917 in clean, modern conditions at a good rate of pay to paint dials. They were instructed to lick the paintbrush to restore a fine point (faster than using a wet rag) having been told it was harmless. Sadly, some of the “radium girls” died and most had health problems. Nevertheless, radium paint was used until the 1960s (we had a radium alarm clock where the light didn’t fade overnight). There was Radium black shoe polish as well, which I don’t think contained any. There are no radium products today, with its only use being in nuclear medicine.

In 1915, an ore with a content of 50% UO₂ was discovered in the Belgian Congo (now DR Congo) and named becquelerite by the French Academy of Sciences. The first radium production plant in Belgium opened in 1922 and within a year dominated the world market, so that the US industry ceased. In the 1930s, a similar grade of ore was discovered in Canada, and in 1938 the two factories agreed not to compete but to share the market as a duopoly, which continued to the late 1950s. The total radium production of the Belgian plant was just over 500 grams over 40 years.

In 1942, IChemE published a paper describing the industrial processes for producing radium.¹

But what about the separated uranium, a waste product of the process? The answer goes back to the Romans, who used uranium oxide as a yellow ceramic glaze. Stocks were used for tiles across Europe and North America in a range of colours depending on the other metals added and firing temperature. It was also used for very popular glazed china dinnerware. Concern has recently been raised over the measurable radiation in some buildings.

Radon

The gas radon is a decay product of radium. Marie Curie collected it but did not identify it as an element. It is a noble gas so could not be separated or measured chemically, and decays rapidly (half-life 3.8 days). Instead, she described it as an emanation from radium. During the First World War she paused her research to take a mobile X-ray unit to the battlefield to determine the position of bullets and shrapnel in wounded soldiers. She also carried some radium chloride with her and with a syringe took some of the gas above it to treat certain conditions, a technique she had found successful during her studies of cancer treatment. Collection of radon over three days was later used as a method of assay for radium, known as the emanation method.

Its identification as an element was complex, involving many people, primarily New Zealand physicist Ernest Rutherford (1871–1937) who received the Nobel Prize in Chemistry in 1908 for his work on nuclear physics. He is often described as the discoverer but thought the honour should go to Marie Curie. He noted that the same emanation came from thorium. It was isolated in 1910 and its properties determined by Scottish chemist Sir William Ramsay (1852–1918), who had previously discovered argon, krypton, neon, and xenon, and isolated helium, thus adding the noble gases to the periodic table. There were many suggestions for a name, but in 1912 the International Union of Pure and Applied Chemistry standardised on niton (Nt). In 1923, they changed it to radon (Rn).

Back in 1527, German polymath Georg Bauer (1494–1555) who wrote in Latin under the name Georgius Agricola, took up the post of town physician and pharmacist in the previously mentioned boomtown of Joachimsthal where silver mining had begun ten years earlier. In his spare time, he studied minerology, writing a key textbook on all the processes associated with metal production. An illustrated 12-volume work which included substantial chemical engineering, De re metallica was a practical handbook for six centuries.

As a physician, he was concerned at the way in which silver miners got ill and died early. He was convinced it was something to do with their working conditions but could not identify the cause. It was in fact radon. In 1948, the USSR took over Czechoslovakia and set up prison camps at Jáchymov, forcing Czechs (a third of them political prisoners) to mine the abandoned silver workings for uranium under harsh conditions. The miners suffered the same symptoms observed by Bauer and had a greatly reduced life expectancy.

Radon is widespread as a gas or dissolved in water in the vicinity of ores of uranium and thorium, and granite. It is the leading cause of lung cancer in non-smokers.

References

1. Trans IChemE January 1, 1942: EF MacTaggart The Production of Radium

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Martin Pitt CEng FIChemE is a regular contributor. Read other articles in his history series: https://www.thechemicalengineer.com/tags/chemicalengineering-history