The overlooked achievements of Charles Pecher and Edgar Sengier

In February 1940 Charles Pecher arrived in Berkeley, California, to investigate medical applications for the radioisotopes produced by Ernest Lawrence’s newly invented cyclotron. Within a year, the medical doctor and physics researcher had discovered that strontium-89 could treat metastatic bone cancer and had demonstrated the imaging method later known as bone scintigraphy.

At around the same time, engineer and industrialist Edgar Sengier moved to New York to organize the commercial affairs of the Union Minière du Haut Katanga, a firm dedicated to extracting the rich mineral resources of Belgian-colonized territory in central Africa. He soon became a central figure in the Allied war effort by selling the US government a large supply of the uranium-rich mineral pitchblende, which he had shrewdly arranged to have delivered to New York City.

The history of radiation science in the US during World War II usually focuses on the Manhattan Project and the making of the atomic bomb, aided by émigrés such as Edward Teller, Leo Szilard, and Enrico Fermi. The stories of Pecher and Sengier don’t quite fit that narrative. They came not from Italy or Hungary but from Belgium, and they contributed to nuclear science in ways beyond bomb design.

Due to Cold War–era secrecy, the achievements of both Belgians remained obscured from the public for years. As it turned out, the fates of Pecher and Sengier diverged dramatically after their initial successes.

A career and life cut tragically short

Born in Antwerp on 26 November 1913, Pecher pursued medicine at the Université Libre de Bruxelles, where he earned a medical degree in July 1939. He was also interested in physics and worked part-time in the physiology department, where he produced several papers on the excitability of nerve fibers in frogs.¹

In August 1939 Pecher accepted a fellowship from the Belgian American Educational Foundation (BAEF) at Harvard University. Pecher wished to apply the then novel field of artificial radioactivity to medicine and biology. The following year he joined Lawrence’s Radiation Laboratory in Berkeley, California, where he immediately demonstrated impressive creativity. He soon filed a patent for the use of the synthetic gamma-ray emitter yttrium-86 to replace expensive radium in industrial metal radiography, a standard technique used to detect cracks and other defects. Pecher also developed an invisible ink laced with artificial radioisotopes, for the purpose of transmitting secret intelligence. The recipient could read the message via autoradiography on a photographic film.

During the same brief period, he coauthored several publications that demonstrated two novel medical uses of artificial radioisotopes. The first was a bone-scan technique. He injected mice with a chemical compound containing radiocalcium or radiostrontium that preferentially attached to bones. By imaging the resulting radiation, Pecher was able to study the skeleton in detail.

Pecher also demonstrated the therapeutic properties of ⁸⁹Sr, an artificial radioisotope chosen as an analogue of calcium for the treatment of bone lesions.² He prepared the beta-ray emitter by irradiating naturally occurring ⁸⁸Sr with a beam of deuterons that had been accelerated in the Berkeley cyclotron. The radioisotope, in the form of a solution of strontium chloride or a similar salt, was injected into the patient intravenously. The radioactive chemical attached preferentially to bones with metastatic lesions, where it emitted beta radiation that killed neighboring tumor cells. Pecher demonstrated the spectacular analgesic effect of the treatment on a human patient suffering from advanced bone metastases.

Pecher’s remarkable streak of productivity was cut short in the spring of 1941, when he received an order from the Belgian government (which at the time was exiled in London) to join a military training camp in Joliette, near Montreal. However, Pecher had already enrolled in the US Army, motivated by his belief that it was the best way to serve his native country. Over the next several months Pecher had to navigate a series of orders, counterorders, and conflicting advice from the Belgian government, the US Army, BAEF, and scientists and diplomats of various ranks—including former US president Herbert Hoover.

At the end of April, Pecher travelled to Joliette and attended military drills. After a month of training, he was given a week’s leave in New York City. From there he followed instructions from the US Army to return to Berkeley. But the Belgian government declared him a deserter, so once again he left his pregnant wife in Berkeley and reported to Joliette. The ordeal left him distraught, and he attempted to ameliorate his anxiety with a powerful sedative. On 31 August 1941, he was found dead on the bank of the Assumption River, north of Joliette. According to the coroner, the death was due to suicide. Considering the absence of eyewitnesses or any written message, the cause of death remains uncertain.

“I have been waiting a long time for your visit”

Sengier was born on 9 October 1879 in Kortrijk. He studied mining engineering and electrical engineering at the University of Louvain before joining Union Minière in 1911.

In 1914 Sengier was promoted and sent to London to oversee the firm’s efforts to provide the Allies with its minerals during World War I. Three years later he was put in charge of the finances of the Commission for Relief in Belgium, which provided food and assistance for the economic and industrial recovery of the German-occupied country. The chairman of the commission was Hoover, a mining engineer whose accomplishments before becoming US president included creating the BAEF in 1920.

In 1918 Sengier turned his attention to rich uranium mineral reserves discovered in 1913 in the Katanga province of the Belgian Congo. He urged Union Minière to start processing the ore for the extraction of radium, which was in demand after the pioneering work of Marie and Pierre Curie. Thousands of tons of uranium-rich pitchblende, the residual waste from radium extraction, began to accumulate in Katanga and in Belgium. At that time, uranium was used only for limited applications, such as in watches, where its weak alpha emission would cause a phosphor to fluoresce.

In 1939, with the world headed toward another war, Sengier made a series of decisive moves. Based in New York, where he had taken refuge from the threat of German invasion, he created the African Metals Corporation (Afrimet), a subsidiary of Union Minière that supplied the US with Congolese strategic metals, including copper, cobalt, and tin. Sengier also ordered the shipping of 1200 tons of pitchblende directly from Katanga to New York. The shipment arrived at the end of 1940 and was stored on Staten Island, where it would be all but forgotten for two years. Neither the other leaders of Union Minière nor any Belgian authorities were informed of the delivery.

What motivated Sengier to make the pitchblende shipment? Along with the threat of Germany invading Belgium, Sengier had an additional incentive. In May 1939 he had been secretly approached and briefed on nuclear fission by Henry Tizard, the rector of Imperial College London and an adviser to the British government, and the French Nobel laureate Frédéric Joliot-Curie. The men wanted to ensure the exclusive acquisition of the highly coveted uranium ore for their respective countries.

Sengier suddenly realized the enormous strategic value that pitchblende had acquired. As a close friend of Marie Curie, he promised to deliver a few hundred tons of the material to the French, but he turned down the British, who wanted exclusive access to the Union Minière supply. Tizard advised Sengier to keep the uranium safe. “Sir, think carefully: If the uranium ore you have were ever to fall into the hands of a possible enemy, it would be a national disaster for our countries,” he said. Tizard’s tip did not fall on deaf ears.

In January 1942, in the aftermath of the Pearl Harbor attack, President Roosevelt ordered the acceleration of R&D that would lead to the atomic bomb. On 17 September, the day after Leslie Groves was placed at the head of the Manhattan Project, he sent his aide, Kenneth Nichols, to meet Sengier in his Afrimet offices. Nichols inquired whether uranium ore from the Congo could be supplied to the US. Sengier asked when Nichols needed it. “If that were not impossible, I would say tomorrow,” Nichols replied. “It’s not impossible,” stated Sengier. “Right now, the ore is here in New York, a thousand tons of it. I have been waiting a long time for your visit!”³

Moments later, a dumbfounded Nichols emerged from Sengier’s office with a signed, handwritten sheet of yellow legal paper declaring that the stock of Staten Island was now owned by the US; the price of the sale would be determined later. Again, Sengier closed the deal without consulting any company or Belgian leaders, many of whom were incommunicado under German occupation in Brussels.

As the end of the war in Europe drew closer, the Allies realized they would have to approach the Belgian government about the future use of Congo-sourced pitchblende. In April 1944 Sengier went to London to represent Belgium in talks with Groves, representing the US, and Sir Charles Hambro, representing Great Britain. On 5 September 1944, a few days before its return to liberated Brussels, the Belgian government signed the Tripartite Agreement. The document gave Belgium a share of the uranium ore to ensure the long-term development of civilian nuclear energy activities.⁴ The agreement was to be treated as a military secret.

Uneven legacies

On 9 August 1945, the day the US dropped its second atomic bomb on Japan, Groves invited Sengier to Washington to meet President Truman. “I present to you the man without whose assistance we could not have accomplished what we did,” Groves said to Truman. The following year, in a private ceremony, Groves presented Sengier with the Medal for Merit, at the time the highest distinction awarded to an American or foreign civilian.

The secrecy surrounding Sengier’s accomplishments has no doubt affected his legacy. For instance, Sengier’s name is never mentioned in Richard Rhodes’s 1986 Pulitzer Prize–winning book, The Making of the Atomic Bomb. Still, the Medal for Merit and several other distinctions bestowed to Sengier crowned the career of an exceptional man.⁵ On the world stage, Sengier’s immediate legacy was to accelerate the birth of nuclear weaponry, hastening the end of World War II.

Pecher’s legacy has been similarly shrouded in secrecy, not only because of the classified aspects of his work but also due to his early death. In 2011 Pecher’s daughter, Evelyne, self-published a book⁶ about her father, who died two months before she was born. In researching the book, she compiled her father’s scientific papers as well as a handful authored by Marshall Brucer, a president and founding member of the Society of Nuclear Medicine, that credited Charles Pecher for his groundbreaking medical imaging work. Since then Pecher has been honored posthumously by the Royal Academy of Belgium and other organizations. We can only speculate on how his career might have developed had he continued to deploy his diverse and immense talents.

His idea of using ⁸⁹Sr was eventually rediscovered⁷ and, in 1993, commercialized in the US by GE Healthcare under the name Metastron; the company made no mention of Pecher in its documentation for the drug. The drug is currently being replaced by radium-223 dichloride under the commercial name Xofigo for the treatment of bone metastases from prostate or breast cancers.

Medical physicists have also adopted Pecher’s bone-scan technique, now known as bone scintigraphy. The modern scan employs ^99mTc, a metastable isomer of technetium with a convenient six-hour half-life that emits 141 keV gamma. Some of the supply of that isotope comes from Belgium, which stands as one of the world’s leading sources of nuclear pharmaceutical products—due in part to the Tripartite Agreement negotiated by Sengier.

References

1. See, for example, C. Pecher, Arch. Int. Physiol. Biochem. 49, 129 (1939).
2. C. Pecher, Univ. Calif. Publ. Pharmacol. 2, 117 (1942).
3. J. Gunther, “Mystery Man of the A-Bomb,” Reader’s Digest, December 1953.
4. A. Jaumotte, Bull. Cl. Sci. Acad. R. Belg. 14, 245 (2003).
5. E. Van der Straeten, Biographie Belge d’Outre-Mer, vol. 7-A, Royal Academy of Overseas Sciences (1973), p. 429.
6. E. Cerf-Pecher, Mon père Charles Pecher: L’homme de sciences, 1913–1941, Didier Devillez Éditeur (2011).
7. N. Firusian, P. Mellin, C. G. Schmidt, J. Urol. 116, 764 (1976).

Amand Lucas is a physicist who holds positions at the Donostia International Physics Center in San Sebastián, Spain; the University of Namur in Belgium; and the University of Liège in Belgium. The article is based on a paper written in French for the 2018 annual meeting of the Royal Science Society of Liège.

The author would like to thank Evelyne Cerf-Pecher for having entrusted him with her very detailed scientific biography of her father, from which part of the original article was inspired. Milton Cole, Stéphane Coutu, and Joseph Manson reviewed the manuscript and helped with the English translation. Frank Deconinck offered his expertise on Charles Pecher, and François Jamar and Stéphane Lucas provided information on medical radioelements.