Toshiba’s compact 4S fast reactor excited Bill Gates and was closely related in concept to TerraPower’s traveling-wave reactor.
This article examines how Japan’s innovative next-generation nuclear technology—capable of long-term operation without refueling and designed with passive safety features—was placed at risk of stagnation after the Fukushima Daiichi accident while China, Russia, India, and other countries accelerated their development programs.

Background
This chapter republishes an article first issued on May 7, 2019, which itself incorporated a chapter published on July 30, 2018.
The newspaper article quoted here was published by the Sankei Shimbun on September 18, 2014, under the headline, “Nuclear Revival, Part Two: The Japanese Next-Generation Reactor That Excited Bill Gates Stalls After the Nuclear Accident as China and Others Close In—A Potentially Fatal Delay.”
The projected dates for commercialization in Russia, China, and other countries are those reported in 2014.
August 3, 2020
“A gap of even a few years could be fatal,” nuclear researchers say with one voice.
Keeping the flame of technological development alive in pursuit of both a stable energy supply and safety is indispensable if Japan is to maintain its international competitiveness.
Under the title, “Akira Ozaki, a senior nuclear technology specialist in Toshiba’s Power Systems Company, says that the construction of a practical reactor remains technically possible even at the present time,” I am republishing the chapter first issued on May 7, 2019.
The following is the chapter published on July 30, 2018.
It is taken from a Sankei Shimbun article dated September 18, 201?.
I believed that voices of outrage must have arisen in Japan over what Bill Gates had done, and I found this article by searching for them.
The Japanese Next-Generation Nuclear Reactor That Excited Bill Gates Stalls After the Nuclear Accident as China and Others Close In—A Potentially Fatal Delay
“Wow!”
Toshiba officials vividly remember the excitement displayed by Bill Gates, the founder of Microsoft.
On November 9, 2009, Gates secretly visited the Isogo Engineering Center in Yokohama, where nuclear power plants are designed, and other Toshiba facilities.
He came in his capacity as chairman of TerraPower, a venture company developing next-generation nuclear reactors in which he had personally invested, to inspect Toshiba’s next-generation 4S reactor.
Although the 4S is a small reactor with an output of between 10,000 and 50,000 kilowatts, its defining feature is its ability to operate continuously for between ten and thirty years without refueling.
It is also said to provide a high degree of safety.
Even if electric power is suddenly lost, the reactor automatically shuts down and its core cools naturally.
Akira Ozaki, a senior nuclear technology specialist in the Nuclear Energy Division of Toshiba’s Power Systems Company, said, “Even at the present time, construction of a practical reactor is technically possible.”
The next-generation reactor being developed by TerraPower, known as the traveling-wave reactor, or TWR, uses a system closely resembling that of the 4S.
It can operate for as long as one hundred years without refueling, requires almost no internal maintenance, and shuts down naturally in an emergency.
Gates and the other TerraPower members praised the design, saying, “Of everything we have studied in nuclear power, Toshiba’s 4S was the most innovative.”
Toshiba and TerraPower have signed a confidentiality agreement, so the details are unknown.
However, a Toshiba official disclosed that they were considering applying 4S technology to the TWR.
Development programs for next-generation reactors known as Generation IV reactors are currently advancing throughout the world.
Nuclear power plants have continued to evolve, particularly through improvements in safety.
The initial reactors were classified as Generation I.
Those constructed from the latter half of the 1960s through the early 1990s were classified as Generation II.
Those that began operating between the latter half of the 1990s and around 2010 were classified as Generation III.
Generation IV reactors were expected to enter practical use from the 2030s onward.
Research and development were progressing on several different next-generation reactor designs, including TerraPower’s TWR.
In Japan, the fast breeder reactor had long been regarded as the leading Generation IV candidate.
A fast breeder reactor, which produces more nuclear fuel than it consumes, is known as a “dream reactor.”
However, the prototype Monju reactor in Fukui Prefecture remained shut down for an extended period following repeated problems.
After the accident at the Fukushima Daiichi Nuclear Power Station, Monju’s future became uncertain, and there remained strong support even within the governing parties for complete withdrawal from the project.
Despite the adverse climate surrounding nuclear power, Japanese organizations were working to preserve the technology developed through the fast breeder reactor program.
The Japan Atomic Energy Agency, Mitsubishi Heavy Industries, and other Japanese organizations agreed to cooperate on next-generation reactor development with the French nuclear company Areva and other parties.
They planned to participate in France’s project to develop ASTRID, a demonstration next-generation fast reactor, and apply Japanese technology to it.
The Japanese government also planned to restart a high-temperature gas-cooled research reactor, whose operation had been suspended since the Great East Japan Earthquake, as early as the following fiscal year and to resume full-scale research and development.
A Mitsubishi Heavy Industries executive explained the significance of the project, saying, “The outlook for next-generation reactor development in Japan is uncertain.
We must accumulate strength for the future.”
Yutaka Sagayama, then a special advisor to the Japan Atomic Energy Agency, emphasized, “For us, this will also help preserve our technology.”
Russia, China, India, and other countries, however, were conducting research and development aimed at the practical application of next-generation reactors.
According to documents issued by the Ministry of Economy, Trade and Industry, Russia planned to begin operating a commercial fast reactor in 2025, while China planned to introduce a commercial reactor around 2030.
There was a danger that Japan would lose its technological advantage while it stood by and failed to proceed with next-generation reactor development.
“A gap of even a few years could be fatal.”
Nuclear researchers spoke with one voice.
Keeping the flame of technological development alive in pursuit of both a stable energy supply and safety is indispensable if Japan is to maintain its international competitiveness.
A senior official of the Ministry of Economy, Trade and Industry emphasized the importance of next-generation reactor development to Japan’s energy policy:
“For Japan, preserving as many options as possible is indispensable for the future.”