Thorium — Complete Timeline: From Discovery to the Present Day

Thorium — Complete Timeline: From Discovery to the Present Day

Date	Event	Significance
1828	Swedish chemist Jöns Jacob Berzelius discovers thorium in a mineral sample from Løvøya island, Norway; names it after Thor, Norse god of thunder	Discovery; the element enters the scientific record
1898	Marie Curie and Gerhard Carl Schmidt independently discover that thorium is radioactive	Establishes thorium's radioactive nature; begins the nuclear physics era for thorium
Late 19th–early 20th century	Thorium dioxide (ThO₂) becomes the key material in gas mantles for gas lighting; Welsbach mantle (developed 1885) makes thorium a major commercial material	First major industrial use; thorium enters mass commerce
Early 20th century	Thoriated tungsten electrodes developed for TIG welding; ThO₂ used in special optical glass for camera and microscope lenses	Industrial applications expand
1939	Nuclear fission discovered by Hahn, Strassmann, Meitner; the nuclear age begins	Context: the theoretical basis for both uranium and thorium nuclear energy is established
1941	Alvin Weinberg joins the Metallurgical Laboratory (Chicago) working on Manhattan Project nuclear theory under Fermi	Weinberg begins his nuclear career
1942	Chicago Pile-1 achieves first self-sustaining nuclear chain reaction (December 2); Weinberg participates in theoretical work	The nuclear age begins operationally
1943–1945	Manhattan Project; Oak Ridge established; preliminary thorium studies conducted alongside uranium weapons work; U-233 first produced and studied	Thorium enters the weapons/nuclear program context
1948–1950	Ed Bettis and Ray Briant at Oak Ridge propose the molten fluoride salt reactor concept for the Aircraft Nuclear Propulsion (ANP) program	Conceptual origin of all MSR technology
1950–1956	Intensive molten fluoride reactor development program at Oak Ridge for ANP	Develops the fundamental science and engineering of fluoride salt reactors
1954	Aircraft Reactor Experiment (ARE) operates at Oak Ridge; 2.5 MW; the first molten salt reactor in history; operates successfully for nine days	Proof of concept; the MSR is demonstrated to work
1955	Alvin Weinberg appointed director of Oak Ridge National Laboratory	Begins Weinberg's era of leadership; gives the MSR program its most effective advocate
1956	ANP program winds down; Weinberg redirects the molten salt program toward civilian power	The pivot from military to civilian MSR application begins
1958–1960	Oak Ridge conceptual design work on the Molten Salt Reactor for civilian power; the two-fluid breeder concept developed	Thorium breeding concept reaches conceptual maturity
1960	India's three-stage nuclear power program formally articulated by Homi Bhabha; Stage 3 explicitly targets the thorium fuel cycle	India's strategic commitment to thorium begins
1961	Nuclear-powered aircraft program cancelled; frees resources for civilian MSR work	Clears institutional space for the civilian thorium program
1963	Construction begins on the Molten Salt Reactor Experiment (MSRE) at Oak Ridge	Hardware development of the first dedicated thorium-cycle-relevant MSR
1965 (June 1)	MSRE achieves first criticality; full power operation achieved August 1965	The MSRE is operational; thorium technology moves from concept to demonstrated reality
1965–1969	MSRE operates for ~13,172 equivalent full-power hours; demonstrates all key MSR principles except thorium breeding	The most important experimental nuclear program of its era; its findings remain the technical foundation of LFTR design
1968	MSRE becomes the first reactor in history to operate on U-233 fuel (bred from thorium); the fuel transition succeeds	Critical proof: U-233 from thorium works as a reactor fuel exactly as predicted
1969 (December 12)	MSRE shut down; AEC declines to fund the Molten Salt Breeder Reactor (MSBR) successor; program effectively ended	The most consequential funding decision against thorium technology
1971 (January)	President Nixon announces the liquid metal fast breeder reactor as the nation's top energy research priority; MSR program starved of resources	Political decision seals the fate of the US MSR program
1972	Oak Ridge completes the MSBR conceptual design — a 1,000 MW(e) commercial thorium breeding reactor; it is never built	The design exists; the funding does not
1973	Alvin Weinberg fired from Oak Ridge directorship by the AEC; told he is "too focused on safety"	The institutional voice for thorium within the US government laboratory system is silenced
1974	Oak Ridge Molten Salt Reactor Program formally shut down	The US government ceases active thorium reactor development for the next ~40 years
1977	President Carter bans commercial reprocessing of spent nuclear fuel; a decision that makes online-reprocessing-dependent MSR design commercially impractical in the US	The reprocessing ban forecloses the MSBR design for the foreseeable future
1977	The Clinch River Breeder Reactor project — the fast breeder alternative to the MSBR — begins major design work	The alternative path chosen over thorium; it too will fail
1979	Three Mile Island accident (March 28, Pennsylvania); partial meltdown; nuclear power's public credibility in the US severely damaged	Context: exactly the type of accident a LFTR's freeze plug would have prevented
1983	Clinch River Breeder Reactor project cancelled by Congress after ~$1.7 billion spent	The alternative to the MSR fails; the US is left with LWRs only
1986	Chernobyl disaster (April 26); 31 immediate deaths; large radioactive release; permanent exclusion zone	Context: the graphite-moderated, positive-void-coefficient reactor that caused Chernobyl is fundamentally different from and far more dangerous than the LFTR
1994	Weinberg publishes "The First Nuclear Era: The Life and Times of a Technological Fixer" — his autobiography and most detailed account of the MSR program's history and his firing	The definitive primary source on the institutional history of thorium suppression
Early 2000s	Kirk Sorensen, working at NASA on lunar base energy systems, discovers the declassified Oak Ridge MSR documents in the National Technical Reports Library	The beginning of the modern thorium revival
2006	Sorensen establishes the Energy From Thorium blog; begins uploading thousands of declassified Oak Ridge documents; builds the primary online thorium research resource	The modern revival becomes publicly accessible
2006	Weinberg dies on October 18, 2006 at age 91; Oak Ridge, Tennessee	The founding father of thorium reactor technology is gone
2009	Yucca Mountain permanent nuclear waste repository cancelled by the Obama administration; demonstrates the unresolved US nuclear waste problem	Makes the thorium waste advantage more politically significant
2010	Gordon McDowell produces "Thorium Remix" — an online documentary compilation reaching millions of viewers; thorium enters mainstream popular awareness	The thorium revival reaches a mass audience
2011	China announces the Thorium Molten Salt Reactor (TMSR) program; $350 million committed; Shanghai Institute of Applied Physics leads	The world's most advanced thorium program is launched
2011	Kirk Sorensen founds Flibe Energy; the primary US private LFTR development company	Private sector thorium development begins
2011 (March)	Fukushima Daiichi disaster (March 11); three reactor meltdowns following tsunami; renewed interest in inherently safe reactor designs	Context: the passive drain of an LFTR would have prevented all three meltdowns; interest in the LFTR spikes globally
2011	Sorensen's TED talk on thorium reaches millions; becomes one of the most watched science presentations online	The thorium story reaches mainstream popular culture
2013	Terrestrial Energy founded in Canada; pursues the near-term commercial Integral MSR (IMSR) without thorium breeding as a first step	MSR technology development begins in the private sector at scale
2016	Moltex Energy founded in the UK; pursues the Stable Salt Reactor (SSR) concept; can burn nuclear waste	More diverse private MSR development
2018	US Nuclear Regulatory Commission begins pre-application engagement with several MSR developers	Regulatory framework for MSR begins development in the US
2021–2022	China's TMSR-LF 2 MW(th) test reactor reportedly achieves operation at the Gobi Desert test site in Wuwei, Gansu Province	The first liquid-fuelled MSR operation since Oak Ridge 1969; the 50-year gap is ended by China
2022 (May 18)	Senator Tommy Tuberville introduces S.4242 "Thorium Energy Security Act" — to preserve the US U-233 stockpile for thorium reactor startup fuel	Legislative recognition of thorium technology at US Senate level; bill not passed
2023	IAEA publishes updated analysis of thorium's long-term energy potential; recommends continued international R&D	International atomic energy body formally re-endorses thorium research
2024	Multiple private MSR companies (Terrestrial Energy; Moltex; Kairos; Flibe; ThorCon) in various stages of design, licensing, and investor engagement	The private sector MSR/thorium industry is an established if pre-commercial sector
Present	No commercial LFTR operates anywhere in the world; China's TMSR program is the most advanced; India's three-stage program continues; private sector development accelerating	The technology's promise remains unrealised at commercial scale; the debate about its potential continues