Explanation:

• Recent Context: Indian Space Research Organisation (ISRO) plans for nuclear energy use in space.
• The UR Rao Satellite Centre (URSC) of ISRO invited proposals for the three phase development of a 100 Watt Radioisotope Thermoelectric Generator (RTG).
• RTGs are lightweight, compact spacecraft power systems that are very reliable.
• RTGs provide electrical power using heat from the natural radioactive decay of plutonium-238.
• RTGs can be used for thermal management, that is providing source of heat for the spacecraft in very low temperatures of space.
• Thus RTGs can provide both heat and electric energy for the space missions.
• Hence, statement 1 is correct.
• RTGs are not new it was first used in space during the Cold War in 1961 for the US’s Transit-4A Mission.
• More than two dozen U.S.space missions have used RTGs such as Perseverance, Cassini, New Horizon, and Curiosity etc.
• In deep space missions solar energy cannot be used as source for generating energy and thus RTGs can be used for such mission, they provide both heath and electric energy for such deep space missions.Hence, statement 2 is correct.
• The large difference in temperature between this hot fuel and the cold environment of space is applied across special solid-state metallic junctions called thermocouples, which generates an electrical current using no moving parts.
• Although sometimes referred to as “nuclear batteries,” RTGs are not fission reactors, nor is plutonium the type that is used for nuclear weapons.
• Hence, statement 3 is not correct.
• Radioisotope Thermoelectric Generators (RTGs) are an alternative source of power where a chain reaction does not take place.
• The power depends on the initial amount of the radioisotope used as fuel and the power is provided by converting the heat generated by radioactive decay of the radioisotope into electricity using thermocouples.
• Most RTGs use plutonium-238.
• With the use of RTGs, the power generated cannot be varied or shut down so supplementary batteries need to be taken into account for the peak times.
• RTGs are used when spacecraft require less than 100 kW.