Predicting Nature’s Nuclear Reactor
Kuroda with students using a mass spectrometer to measure isotope ratios. Photo courtesy the University of Arkansas Special Collections.
In the 1950s, Paul Kuroda of the University of Arkansas’ Department of Chemistry 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.
Bill Durham, professor emeritus of chemistry and biochemistry at the U of A, said Kuroda’s prediction has never been disproven.
“It still stands, there’s no question about it,” Durham said. “For years he collected rainwater to look for fallout, which is the residual radioactive material propelled into the upper atmosphere following a nuclear blast or nuclear reaction. There is a distribution of elements that are produced by a nuclear reaction and Kuroda published a paper indicating what to look for in a natural reactor. He published the criteria.”
Kuroda was also interested in cosmology. In 1960, he predicted the existence of Plutonium-244 as an element present during the solar system’s formation. Confirmation of his theory enabled scientists to more accurately date the sequence of events in the solar system’s early history.
Kuroda’s two papers on these topics were featured in “The 20th Century’s 85 Benchmark Papers in Nuclear Chemistry,” edited by Nobel laureate Glenn Seaborg.
Kuroda, who retired as Distinguished Professor of chemistry in 1987 and died in 2001, received a bachelor’s degree and a doctorate from the Imperial University of Tokyo and in 1944 became the youngest faculty member there. In 1949 he received the Pure Chemistry Prize of the Chemical Society of Japan. That same year he immigrated to the United States and became a U.S. citizen in 1955. After postdoctoral studies at the University of Minnesota, he became an assistant professor of chemistry at the U of A in 1952. In 1979 he became the university’s inaugural Edgar Wertheim Distinguished Professor of Chemistry.
While at the U of A he was the author or co-author of almost 400 publications.
“Paul was definitely unique,” said Durham. “He was very independent. He taught wet nuclear chemistry when there were very few places doing it.”