With reference to radioisotope thermoelectric generators (RTGs), consider the following statements:
- 1.RTGs are miniature fission reactors.
- 2.RTGs are used for powering the onboard systems of spacecrafts.
- 3.RTGs can use Plutonium-238, which is a by-product of weapons development.
Which of the statements given above are correct?
Answer & explanation
Answer: (b) 2 and 3 only
An RTG is not a reactor: nothing is split in a chain reaction. It simply turns the steady heat given off by the natural decay of plutonium-238 into electricity using thermocouples, which is why it powers deep-space probes and rovers such as Voyager, New Horizons, Curiosity and Perseverance. The US made its plutonium-238 at the Savannah River nuclear-materials plant, part of its weapons complex.
- ✗ 1. RTGs have no fission or chain reaction. Heat from the spontaneous radioactive decay of plutonium-238 is converted to power by thermocouples, with no moving parts.
- ✓ 2. They supply electricity and warmth to spacecraft where sunlight is weak or dust blocks solar panels; the current US model, the MMRTG, gives about 110 watts at launch.
- ✓ 3. Plutonium-238 is not weapons-grade plutonium, but the US produced it at its Savannah River plant, a site built to make nuclear-weapons materials, until the late 1980s; it is the standard RTG fuel.
Remember · RTG = heat from natural decay of Pu-238 → electricity via thermocouples (Seebeck effect). No fission. Powers Voyager, Cassini, New Horizons, Curiosity, Perseverance.
Sources
- US Department of Energy, Office of Nuclear Energy: What is a Radioisotope Power System? ↗ “Radioisotope power systems (RPS) convert heat generated by the natural decay of plutonium-238 —a radioactive isotope—into electrical power. They have powered more than two dozen U.S. space missions”
- NASA Radioisotope Power Systems programme ↗ “a type of nuclear energy technology that uses heat to produce electric power for operating spacecraft systems in the darkest, dustiest, and most distant places in our solar system.”
- NASA: About Plutonium-238 ↗ “U.S. production of plutonium oxide for space exploration at the Department of Energy’s Savannah River Plant in South Carolina ceased in the late 1980s, and interim purchases of heat source material from Russia have ended.”
- US Department of Energy: Savannah River Site History 1950-1989 ↗ “The Savannah River Site was constructed during the early 1950s to produce the basic materials used in the fabrication of nuclear weapons, primarily tritium and plutonium-239, in support of our nation's defense programs.”
Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). ·