Where else could you find this kind of energy? At the Nuclear Regulatory Commission (NRC) our power comes from our people. Hardworking Americans who oversee the safe use of nuclear technology that powers communities, revolutionizes medicine, and empowers America.

Clementine—The world’s first fast neutron reactor

March 19, 2024, 3:00PMNuclear NewsJeremy Hampshire

The exterior of the Clementine nuclear reactor at Los Alamos Scientific Laboratory. (Photo: LANL)

In March 1949—75 years ago this month—the 25-kilowatt reactor known as Clementine reached full power. As an experimental reactor, it had a rather long and successful run. It was the world’s first fast neutron (high-energy) reactor and operated from initial criticality in 1946 to final shutdown in 1952.

To continue reading, log in or create a free account!

Mark Peters: Building on a strong foundation

July 10, 2026, 3:09PMNuclear NewsLucas Geiger

Summer at the American Nuclear Society carries with it a sense of renewed momentum as the incoming president takes office and starts making plans for the year ahead. This has been particularly...

Spent fuel recycling and conditioning topic of U.S.-Japan meeting

June 8, 2026, 3:32PMNuclear News

Officials with the Department of Energy’s Office of Environmental Management discussed spent nuclear fuel recycling and conditioning with counterparts from Japan during the 13th U.S.-Japan...

INL reports findings on unusual quantum behavior of plutonium

June 8, 2026, 7:11AMNuclear News

Scientists at Idaho National Laboratory have discovered that plutonium hexaboride (PuB6) displays a type of unusual quantum property called a topological Kondo insulating state. Materials with...

Oklo continues plutonium fuel development with LANL and Nvidia partnership

May 1, 2026, 7:16AMNuclear News

Oklo announced a new partnership with Los Alamos National Laboratory and Nvidia to perform AI-enabled research on nuclear infrastructure and fuel.The partnership is focused on exploring...

New Mexico comes after DOE again on WIPP waste

April 29, 2026, 9:38AMNuclear News

Claiming the Department of Energy is backing away from commitments made in a 2023 settlement agreement with the state, the New Mexico Environment Department (NMED) is proposing revisions to...

New scintillating composite leads to versatile and inexpensive neutron sensor

April 13, 2026, 12:24PMNuclear News

Los Alamos National Laboratory has announced the development of a new type of neutron sensor that works across a wide range of conditions, including in the presence of strong gamma...

Panelists discuss U.S. path to criticality in ANS webinar

April 1, 2026, 3:08PMNuclear News

The American Nuclear Society recently hosted a panel discussion featuring prominent figures from the nuclear sector who discussed the industry’s ongoing push for criticality.Yasir Arafat,...

Return of the HB Line at SRS

March 11, 2026, 5:02PMNuclear News

The Department of Energy is bringing the HB Line facility at the Savannah River Site back on line to recycle surplus plutonium and produce uranium-plutonium mixed oxide (MOX) fuel for advanced...

New Mexico holds DOE’s feet to fire in removal of LANL waste

February 17, 2026, 7:24AMNuclear News

The state of New Mexico is fining the Department of Energy for nearly $16 million, claiming the department has failed to prioritize the removal legacy nuclear waste from Los Alamos National...

Valar achieves cold criticality at LANL

November 18, 2025, 3:02PMNuclear News

Valar Atomics has announced that its Nova Core achieved zero-power criticality on November 17 at Los Alamos National Laboratory’s National Criticality Experiments Research Center (NCERC) at...

Clementine—The world’s first fast neutron reactor

Related Articles