Japan in WWII: An obscure strand

In writing up Japan’s early nuclear power history, I’ve needed to sum up the nation’s World War II efforts to manufacture a nuclear weapon (the main aspirants of course being U.S.A., Germany, and U.S.S.R.). It turns out Japan got almost nowhere towards a nuke, and what it did during the war turned out to have almost no relevance to its slowly emergent post-war interest in nuclear energy. I did, however, spot a curio:

Per Dahl book

While uranium separation got nowhere, a belated heavy-water effort had, it appears, been launched years earlier by the Japanese industrialist Jun Noguchi. In 1926, he founded the Korean Hydro Electric Company at Konan (Japanese for Hungnam), subsequently fed by the massive Chosun and Fusen Reservoirs on the Yalu River. It became the site of an industrial complex producing ammonia, among other things. In 1943, anticipating a shortage of electric power in Japan once the B-29 raids began in earnest, Noguchi stepped up ongoing hydrogen production for ammonia by the Korean Nitrogen Fertilizer Company at Konan, augmenting a smaller-scale effort on Kyushu, Japan’s southernmost island. Shortly after the surrender of Japan, the Manhattan Project’s Atomic Bomb Mission deployed there in September reported that Arakatsu Bunsaku of the F-Project had been obtaining 20 grams per month of heavy water from electrolytic ammonia plants, based on the Haber process, in Korea and Kyushu. Despite the availability of a heavy-water production program potentially rivalling Norsk Hydro’s at Vemork, neutron-multiplication studies with heavy water or any other form of moderator seems not to have been undertaken at Kyoto. The industrial facilities on the Korean peninsula fell into communist North Korean hands before they could be fully explored and assessed by the U.S. occupation authorities.

Dahl, Per F. 1999. Heavy Water and the Wartime Race for Nuclear Energy. IOP, Bristol, p. 281

The Norsk Hydro heavy water plant figured in Allied raids and (failed) German reactivity efforts (failed). Japan, it seems, could have pursued the heavy water path. But it didn’t even try, perhaps because its scientific expertise was so low that it didn’t realize what it had.