The TOPAZ nuclear reactor is a lightweight

nuclear reactor A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...

developed for long term space use by the

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. Cooled by liquid metal, it uses a high-temperature moderator containing hydrogen and highly enriched fuel and produces electricity using a

thermionic converter A thermionic converter consists of a hot electrode which thermionically emits electrons over a potential energy barrier to a cooler electrode, producing a useful electric power output. Caesium vapor is used to optimize the electrode work functi ...

Nomenclature

In initial discussions, it was unclear that TOPAZ and the somewhat similar YENISEI reactors were different systems, and when the existence of the two Russian thermionic reactors became generally known, US personnel began referring to TOPAZ as TOPAZ-I and YENISEI as TOPAZ-II.

TOPAZ-I

The first

reactors were discussed by scientists at the

Los Alamos Scientific Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, in ...

(LASL) in 1957. Following the visit of Soviet scientists to LASL in 1958, they carried out tests on TI systems in 1961, initially developing the single cell ENISY reactor (also known as TOPAZ-II). Work was carried out by the Kurchatov Institute of Atomic Energy and the Central Bureau for Machine Building to develop the multi-cell TOPAZ (also known as TOPAZ-I), a Russian acronym for "Thermionic Experiment with Conversion in Active Zone". It was first ground tested in 1971, when its existence was acknowledged. It was under the auspices of Krasnaya Zvezda. The first TOPAZ reactor operated for 1,300 hours (~54 days) and then was shut down for detailed examination. It was capable of delivering 5 kW of power for 3–5 years from of fuel. Reactor mass was ~ . TOPAZ was first flown in 1987 on the experimental Plazma-A satellites

Kosmos 1818 Kosmos 1818 was a nuclear powered Soviet surveillance satellite in the RORSAT program, which monitored NATO vessels using radar. Kosmos 1818 was the first satellite to use the TOPAZ-1 fission reactor. In July 2008, the satellite was damaged, and ...

and

Kosmos 1867 Kosmos 1867 () was a nuclear powered radar ocean reconnaissance satellite (RORSAT) that was launched by the Soviet Union on July 10, 1987. It was put into an orbit of about . Its mission was to monitor the oceans for naval and merchant vessels, a ...

, which were intended to test both the TOPAZ reactor and the Plasma-2 SPT electric engine. Both reactors were damaged in the 1990s, causing a leak of radioactive coolant. A proposed follow-up Plasma-2 was to have been equipped with an improved reactor. One reactor operated for 6 months, the other for a year. The program was canceled by

Mikhail Gorbachev Mikhail Sergeyevich Gorbachev (2 March 1931 – 30 August 2022) was a Soviet and Russian politician who served as the last leader of the Soviet Union from 1985 to dissolution of the Soviet Union, the country's dissolution in 1991. He served a ...

in 1988.

TOPAZ-II

In the TOPAZ-II or ENISY reactor each fuel pin (96% enriched UO₂) is sheathed in an emitter which is in turn surrounded by a collector, and these form the 37 fuel elements which penetrate the cylindrical

zirconium hydride Zirconium hydride describes an alloy made by combining zirconium and hydrogen. Hydrogen acts as a hardening agent, preventing dislocations in the zirconium atom crystal lattice from sliding past one another. Varying the amount of hydrogen and th ...

(ZrH) moderator. This in turn is surrounded by a

beryllium Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...

neutron reflector A neutron reflector is any material that reflects neutrons. This refers to elastic scattering rather than to a specular reflection. The material may be graphite, beryllium, steel, tungsten carbide, gold, or other materials. A neutron reflect ...

with 12 rotating control drums. Liquid metal coolant ( NaK) surrounds each fuel element. The mass of the reactor is ~ . In January 1991 a model of the TOPAZ-II was exhibited at a scientific symposium in

Albuquerque Albuquerque ( ; ), also known as ABQ, Burque, the Duke City, and in the past 'the Q', is the List of municipalities in New Mexico, most populous city in the U.S. state of New Mexico, and the county seat of Bernalillo County, New Mexico, Bernal ...

, generating interest in the US in the possible purchase of it and the Strategic Defense Initiative Organization arranged to buy two Topaz-2 reactors from Russia for a total of $13 million, planning to use the reactors to improve US models. However, the

Nuclear Regulatory Commission The United States Nuclear Regulatory Commission (NRC) is an independent agency of the United States government tasked with protecting public health and safety related to nuclear energy. Established by the Energy Reorganization Act of 1974, the ...

ruled that US law prohibited the "export" of such a device to the Soviet Union - even though it was Soviet-made and only a model rather than an actual reactor. It took a month before the situation was resolved by a new NRC ruling and the model returned to Russia. The

United States Department of State The United States Department of State (DOS), or simply the State Department, is an United States federal executive departments, executive department of the U.S. federal government responsible for the country's foreign policy of the United State ...

then put a hold on the deal, which was only lifted when Secretary of State

James Baker James Addison Baker III (born April 28, 1930) is an American attorney, diplomat and statesman. A member of the Republican Party (United States), Republican Party, he served as the 10th White House chief of staff and 67th United States secretary ...

intervened. One of the reactors was to be used in a flight test in 1995 to power experimental electrical thrusters, but there were objections from scientists concerned about the possible impact of radiation emitted by the reactor on instruments aboard space satellites and protests from opponents of space-based weapons and nuclear power. In addition, the

Department of Energy A ministry of energy or department of energy is a government department in some countries that typically oversees the production of fuel and electricity; in the United States, however, it manages nuclear weapons development and conducts energy-rela ...

was slow to grant the necessary approval and in 1993 budget restrictions forced the cancellation of the program. Six TOPAZ-II reactors and their associated support equipment were flown to the US, where they were extensively ground tested by US, British, French, and Russian engineers. The reactors' unique design allowed them to be tested without being fuelled. Although the test program was considered a success, no plans were pursued to fly any of the reactors.

Manufacturer

The TOPAZ reactor is manufactured by the State Research Institute, Scientific Industrial Association (also known as Luch), which is operated by Russia's Ministry of Atomic Energy.

References

{{Soviet Union–United States relations, state=collapsed Nuclear power in Russia Nuclear reactors Nuclear power in space Nuclear technology in the Soviet Union Nuclear power in the Soviet Union Soviet inventions Soviet Union–United States relations Satellite nuclear reactors