Paul Kazuo Kuroda

Many times in the course of the exposition of science and scientific discoveries, the lime light is focused on one or two individuals and it is often forgotten that many other worthy individuals were involved: Those that provided fundamental input, the data gatherers, the professors or even mentors. They are not household names like an Einstein or Newton but nevertheless had a significant role. Such is the following individual.

"In the 1950s, Kuroda predicted that
self-sustaining nuclear chain reactions could have occurred naturally in earth's geologic history. In 1972, his prediction was confirmed when scientists discovered a natural nuclear reactor in Gabon, Africa. In 1960, he predicted the existence of Plutonium-244 as an element present during the solar system's formation. The presence of excess Plutonium-244 fission-xenon was first detected in his laboratory at the University of Arkansas in 1965. Confirmation of his theory enabled scientists to more accurately date the sequence of events in the solar system's early history." He also employed Francis William Aston's use of the mass spectrometer in chemical analysis.


Biography:

University of Arkansas

Paul Kazuo Kuroda was born April 1, 1917 in Kurogi, Fukuoka Prefecture, Kyushu, Japan, the only son of Kanjiro and Shige Kuroda. His father was a school teacher and later an official at the Ministry of Education in Tokyo and a noted calligrapher. His paternal ancestors belonged to the samurai class in Fukuoka, the so-called Kuroda-Bushi (samurai of the Kuroda-clan), well-known among the Japanese. His maternal ancestors (according to his grandmother) can be traced to the 16th century warlord Shibata-Katsuie, the head retainer of Lord Oda - Nobunaga, who later became a Shogun.

Kuroda grew up under the influence of the words of an American chemist, William Smith Clark (1826-1885), President of the Agricultural College of Massachusetts (now the University of Massachusetts) who in 1876 was invited by the Japanese government to come to Japan to establish an American-style university in Sapporo, Hokkaido. The Agricultural College of Sapporo (now the University of Hokkaido) was thus founded in 1877. When Clark left Japan to return to America, he turned in his saddle, waved at his students, and shouted in farewell, "BOYS! BE AMBITIOUS!" ----- a phrase still familiar to almost all Japanese.

William Smith Clark received his doctoral degree in 1852 at the George Augustus University in Göttingen, where he studied under the great German chemist Friedrich Wöhler. The title of his thesis was Analysem von Meteoreisem, a remarkable coincidence since exactly 100 years later Kuroda was to be appointed to the faculty of the University of Arkansas to begin his studies on meteorites. Kuroda took his first name Paul from a well-known Japanese scholar, Paul Inazo Nitobe, who published the book Bushi-do (the Code of Samurai) and who was a student of William Clark at the Agricultural College of Sapporo.

In 1929, Kuroda entered the Tokyo-Koto-Gakko, an elite school for boys from age 12 to 19, the Japanese version of Eaton. In 1932, when he was 15, Kuroda learned of discoveries of radioactivity and radium by Becquerel and the Curies and decided to become a chemist. Two years later in 1934, Frederic Joliot and Irene Curie discovered artificial radioactivity.

In 1936 when Kuroda was 19, Francis William Aston visited Japan and gave a special lecture on "Mass Spectra and Isotopes". Kuroda had the good fortune of attending the lecture and meeting Aston. Kuroda was greatly impressed and decided to study under Francis Aston, after graduating from the Imperial University of Tokyo. He realized at once that the mass-spectrometer invented by Aston would play a key role in chemistry in the future, but he was disappointed to find that professors of chemistry in those days seemed to regard it as a tool for physicists, not for chemists.

In 1937, Niels Bohr visited Japan and gave a series of lectures at the Imperial University of Tokyo. Since Bohr was always surrounded by a crowd, all Kuroda was able to do was sit in the front row of the lecture hall and listen to what Bohr had to say. Three months later in July 1937, the Japanese Imperial Army began the war in China, and soon Japan became isolated from much of the world.

In 1938, the Nobel Prize in Physics was awarded to Enrico Fermi. Then Kuroda decided to go to Italy to study under Fermi and the radiochemist Emilio Segré who later (with Perrier) discovered the first artificial element, technetium. In preparation for an examination for the Japan-Italy Fellowship Program Kuroda purchased a book Italian in Three Weeks and studied day and night. A few days before the examination he was shocked to discover that it would be given in French.

So Kuroda never had an opportunity to meet Fermi, but he did become personally acquainted with Segré several decades later. In 1988, Segré and his wife visited Kuroda at his home in Las Vegas. Segré was annoyed at that time because a Belgian nuclear physicist had published a series of papers in Europe and the U.S. arguing that the discovery of Element 43 should be credited to Ida Noddack. Segré asked Kuroda to settle this matter. Kuroda agreed to do his best and in 1989 published A Note on the Discovery of Technetium in which he concluded that Perrier and Segré were, in fact, the discoverers of technetium. In December 1988 Segré gave as a Christmas present to Kuroda a photograph of Fermi, Segré and Hideki Yukawa taken in 1948 at the University of California, Berkeley, one year before Yukawa was awarded the 1949 Nobel Prize in Physics. Yukawa was the first Japanese scientist to receive a Nobel Prize. On the back of this photograph, which was enlarged by Segré himself, were the following words: "FROM ARTIFICIAL TO NATURAL TECHNETIUM".

Kuroda graduated from the Imperial University of Tokyo in 1939 and in the same year was appointed to the rank of Fukushu (junior assistant). In 1941 he was promoted to the rank of Joshu (senior assistant). Kuroda studied under Professor Kenjiro Kimura, discoverer of 237U and the symmetric mode of fission, and in 1944 he received his doctorate and was promoted to the rank of Jokyoju (associate professor) of the Imperial University of Tokyo. At the age of 27, Kuroda was the youngest faculty member. The war suddenly ended in 1945; and, the name of the university was changed to the University of Tokyo. Kuroda thus became the last Jkyju of the Imperial University of Tokyo.

In 1949 Kuroda received the Pure Chemistry Prize of the Chemical Society of Japan. He was the youngest chemist in Japan to receive the highest honor bestowed on a chemist in Japan.

In 1949 Kuroda was admitted to the United States. In 1955, he became a U.S. citizen; and thus, for many years, he was to be scrutinized and shunned by most of the old generation of Japanese scientists. His brilliant career in the United States during the second half of the 20th century was never fully recognized in Japan until finally in 1991 (42 years after he received the Pure Chemistry Prize of the Chemical Society of Japan) he was awarded the first Shibata Prize of the Geochemical Society of Japan, which carries the name of Professor Yuji Shibata founder of geochemistry in Japan and who, for many years, was President of the Japan Academy of Sciences.

In 1952, Kuroda was appointed Assistant Professor of Chemistry at the University of Arkansas and Associate Professor in 1955. He was appointed Full Professor in 1961 and became the first Edgar Wertheim Distinguished Professor in 1979. He retired from the University of Arkansas in 1987, at the age of 70.

In addition to the Pure Chemistry Prize and the Shibata Prize, Professor Kuroda received the University of Arkansas Distinguished Faculty Achievement Award (1963), the American Chemical Society Southwest Regional Award (1970), the ACS Southern Chemist Award (1973), the ACS Midwest Regional Award (1977), and the ACS Nuclear Applications in Chemistry Award (1978). He was the Honor Initiate at the 43rd Biennial Conclave of Alpha Chi Sigma.


Memorial:

Meteoritics & Planetary Science 36, 1409-1410 (2001)

Paul K. Kuroda (1917-2001)

Paul K. Kuroda was born on 1 April 1917 in Fukuoka Prefecture, Japan, as Kazuo Kuroda, and died at his home in Las Vegas, Nevada on 16 April 2001. He received bachelors and doctoral degrees from the Imperial University of Tokyo where he studied under Professor Kenjiro Kimura. A special lecture by Francis William Aston, in Japan to observe the solar eclipse in 1936, may have sparked Kuroda's future interest in combined studies of radio- and cosmo-chemistry. His first paper was published in 1935, and he became the youngest faculty member at the Imperial University of Tokyo in 1944. Despite the ban on radio-chemistry in occupied Japan and the confiscation of all uranium and thorium minerals and reagents at the university, Kuroda continued his studies of natural radioactives in thermal water, volcanic fumaroles, and rain until 1949, when he sailed to America. En route, he received the Christian name, "Paul". On arriving in San Francisco in August of 1949, he visited Glenn Seaborg at UC-Berkeley. Although Kuroda received the Pure Chemistry Prize of the Chemical Society of Japan that year, as a Japanese national he was not eligible to work on nuclear studies that involved U.S. national security. His 1950-1952 postdoctoral studies at the University of Minnesota with Professors E. B. Sandell and I. M. Kolthoff were in analytical chemistry, but he returned to the study of natural and artificial radioactivity after joining the faculty at the University of Arkansas in 1952.

Fate was kind to Kuroda in the interim. He met Louise Morren, his lovely Dutch wife-to-be, at the University of Minnesota and he met a nuclear chemist, Dr. Rayond R. Edwards, chairman of the Chemistry Department at the University of Arkansas, at the first combined International Symposia of UPAC and ACS in September 1951. Following his move to Arkansas and his marriage to Louise, he became a US Citizen in 1955. At the University of Arkansas he trained 64 PhD students, several postdoctoral associates, and he befriended many undergraduate students. He became the first Edgar Wertheim Distinguished Professor of Chemistry in 1979, he officially retired from the University of Arkansas in 1987, but he remained active in research. He was the author or co-author of almost 400 publications. In nuclear and radio-chemistry Kuroda is known for his study of spontaneous fission, for having published the first unclassified report on artificial fission products in rainwater with Paul Damon in 1953, and for isolating Tc-99 from pitchblend with Bernie Kenna in 1961. In meteoritics and planetary science Kuroda is best known for having predicted, in 1956, that self-sustaining nuclear chain reactions could have occurred naturally in Earth's geologic history and for having predicted, in 1960, that Plutonium-244 (t1/2 = 82 Ma) had been present in the early solar system. On 25 September 1972, the French Atomic Energy Commission reported evidence that a natural nuclear reactor had occurred at Oklo in the Republic of Gabon, Africa, and the presence of excess xenon in the Pasamonte meteorite from the fission of 244Pu was first detected in his laboratory at the University of Arkansas in 1965. Glenn Seaborg and Walter Lovelend selected both of Kuroda's papers on these subjects as 2 of the 85 Benchmark Papers in Nuclear Chemistry (Benchmark Papers, Vol 5, Hutchison Ross Pub. Co, Stroudsburg, PA, 1982). His students remember Kuroda for his deep personal commitment to the spirit of scientific inquiry, excellence in teaching, genius at seeing trends in data, love for his family, admiration and paternal kindness for his current and former students, and the sukiyaki dinners that he prepared when we were invited to his home. In addition to the Pure Chemistry Prize, Kuroda received the University of Arkansas Distinguished Faculty Achievement Award (1963), the ACS Southwest Regional Award (1970), the ACS Southern Chemist Award (1973), the ACS Midwest Regional Award (1977), the ACS Nuclear Applications in Chemistry Award (1978), and the Shibata Prize of the Geochemical Society of Japan (1991). He was the Honor Initiate of Alpha Chi Sigma Fraternity at its 43rd Biennial Conclave in 1996. Kuroda remained active in research, each year publishing papers on the origin and early history of the solar system. His creativity shows in the final chapter of his career (Kuroda and Myers, 2000) with findings that a) the 244Pu/136Xe ages of lunar samples and meteorites indicate formation of the solar system started 5.1 Ga ago, soon after the explosion of a supernova, and b) the break-up of meteorite parent bodies occurred 4.55 Ga ago, the age generally assumed for the solar system in attempts to interpret experimental data of older lead/lead and K/Ar ages.

Oliver K. Manuel

University of Missouri Department of Chemistry

Rolla, Missouri 65401, USA


SELECTED PUBLICATIONS OF PAUL K. KURODA:

KURODA, P. K. (1956) On the nuclear physical stability of
the uranium minerals, J. Chem. Phys. 25, 781- 782.

KURODA, P. K. (1956) On the infinite multiplication
constant and the age of the uranium minerals, J. Chem.
Phys. 25, 1295- 1296.

KURODA, P. K. (1960) Nuclear fission in the early history
of the Earth, Nature 187, 36- 38.

ROWE, M. W. AND KURODA, P. K. (1965) Fissiogenic
xenon from the Pasamonte meteorite, J. Geophys. Res. 70,
709-714.

CLARK, R. S., YOSHIKAWA, K., RAO, M. N., PALMER,
B. D., THEIN, M. AND KURODA, P. K. (1967) The time
interval between nuclear detonation and formation of single
fallout particles, J. Geophys. Res. 72, 1793-1796

KURODA, P. K. (1971) The temperature of the Sun in the
early history of the Solar System, Nature 230, 40-42.

KURODA, P. K. (1979) Isotopic anomalies in the early
solar system, Geochem. J. 13, 83-90.

KURODA, P. K. (1982) The Origin of the Chemical
Elements and the Oklo Phenomenon, 165 pp. Springer-
Verlag, Berlin, Germany.

KURODA, P. K. AND MYERS, W. A. (1998) Extinct
radionuclides 26Al and 129I in the early solar system,
Naturwissenschaften. 85, 180-182.

KURODA, P. K. AND MYERS, W. A. (2000) Xenology,
FUN anomalies and the plutonium-244 story, in Origin of
Elements in the Solar System: Implications of Post-1957
Observations (ed. O. Manuel) pp. 431-499. Kluwer
Academic/Plenum, New York, New York, USA.


Also see:

"My Early Days at the Imperial University of Tokyo" by Paul Kazuo Kuroda