page_title: Thorium-based nuclear power
section_title: Background and brief history
hierarchical_section_title: Thorium-based nuclear power / Background and brief history
caption_attribution_description: English: Photo of a molten-salt reactor (MSR) at Oak Ridge National Laboratory before their thorium energy research ended. There is a larger copy of this file already at Commons File:MoltenSaltReactor.jpg We hope (talk) 21:39, 14 October 2012 (UTC)
context_page_description: Thorium-based nuclear power generation is fueled primarily by the nuclear fission of the isotope uranium-233 produced from the fertile element thorium. According to proponents, a thorium fuel cycle offers several potential advantages over a uranium fuel cycle—including much greater abundance of thorium on Earth, superior physical and nuclear fuel properties, and reduced nuclear waste production. However, development of thorium power has significant start-up costs. Proponents also cite the lack of easy weaponization potential as an advantage of thorium due to how difficult it is to weaponize the specific uranium-233/232 and plutonium-238 isotopes produced by thorium reactors, while critics say that development of breeder reactors in general increases proliferation concerns. As of 2020, there are no operational thorium reactors in the world
  A nuclear reactor consumes certain specific fissile isotopes to produce energy. Currently, the most common types of nuclear reactor fuel are:
  Uranium-235, purified by reducing the amount of uranium-238 in natural mined uranium.
context_section_description: After World War II, uranium-based nuclear reactors were built to produce electricity. These were similar to the reactor designs that produced material for nuclear weapons.  During that period, the government of the United States also built an experimental molten salt reactor using U-233 fuel, the fissile material created by bombarding thorium with neutrons. The MSRE reactor, built at Oak Ridge National Laboratory, operated critical for roughly 15,000 hours from 1965 to 1969. In 1968, Nobel laureate and discoverer of plutonium, Glenn Seaborg, publicly announced to the Atomic Energy Commission, of which he was chairman, that the thorium-based reactor had been successfully developed and tested.
  In 1973, however, the US government settled on uranium technology and largely discontinued thorium-related nuclear research. The reasons were that uranium-fueled reactors were more efficient, the research was proven, and thorium's breeding ratio was thought insufficient to produce enough fuel to support development of a commercial nuclear industry.  As Moir and Teller later wrote, "The competition came down to a liquid metal fast breeder reactor (LMFBR) on the uranium-plutonium cycle and a thermal reactor on the thorium-233U cycle, the molten salt breeder reactor. The LMFBR had a larger breeding rate ... and won the competition."  In their opinion, the decision to stop development of thorium reactors, at least as a backup option, “was an excusable mistake.”
  Science writer Richard Martin states that nuclear physicist Alvin Weinberg, who was director at Oak Ridge and primarily responsible for the new reactor, lost his job as director because he championed development of the safer thorium reactors. Weinberg himself recalls this period:
  [Congressman] Chet Holifield was clearly exasperated with me, and he finally blurted out, "Alvin, if you are concerned about the safety of reactors, then I think it may be time for you to leave nuclear energy." I was speechless. But it was apparent to me that my style, my attitude, and my perception of the future were no longer in tune with the powers within the AEC.
  Martin explains that Weinberg's unwillingness to sacrifice potentially safe nuclear power for the benefit of military uses forced him to retire:
  Weinberg realized that you could use thorium in an entirely new kind of reactor, one that would have zero risk of meltdown. ... his team built a working reactor .... and he spent the rest of his 18-year tenure trying to make thorium the heart of the nation’s atomic power effort. He failed. Uranium reactors had already been established, and Hyman Rickover, de facto head of the US nuclear program, wanted the plutonium from uranium-powered nuclear plants to make bombs. Increasingly shunted aside, Weinberg was finally forced out in 1973.
  Despite the documented history of thorium nuclear power, many of today's nuclear experts were nonetheless unaware of it. According to Chemical & Engineering News, "most people—including scientists—have hardly heard of the heavy-metal element and know little about it...," noting a comment by a conference attendee that "it's possible to have a Ph.D. in nuclear reactor technology and not know about thorium energy." Nuclear physicist Victor J. Stenger, for one, first learned of it in 2012:
  It came as a surprise to me to learn recently that such an alternative has been available to us since World War II, but not pursued because it lacked weapons applications.
  Others, including former NASA scientist and thorium expert Kirk Sorensen, agree that "thorium was the alternative path that was not taken … " According to Sorensen, during a documentary interview, he states that if the US had not discontinued its research in 1974 it could have "probably achieved energy independence by around 2000."
caption: Early thorium-based (MSR) nuclear reactor at Oak Ridge National Laboratory in the 1960s
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