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Answer:
hey dear all are correct but 20(B) i is wrong, it will be (a)
Answer:
Nonrenewable Energy Resources
Nuclear Fuel
Nuclear fuel—Uranium-235, found in certain rock formations, is mined for use as the fissile material in slow-reaction nuclear power generation. Rare in its natural state, uranium-235 is a nonrenewable resource, although small quantities go a long way. For example, the fission of one pound of uranium releases more energy than burning three million pounds of coal.
Nuclear fission reactors split atoms to release the energy from the nucleus of enriched uranium. In this process, the fuel is placed in rods in the reactor core, and a chain reaction is started by bombarding the fuel with slow neutrons. Heat from the chain reaction is absorbed by the water in the reactor. The water then turns into steam, which, in turn, drives a turbine and a generator to produce electricity. Control rods—made of cadmium or boron—are introduced to slow down or stop the chain reaction.
In fast-reaction nuclear power generation (breeder reactors), high-velocity neutrons cause the fissions, using plutonium or uranium-233. Breeder reactors produce more fuel (enriched uranium and plutonium) than they consume. Thus, fast-reaction nuclear power fuel is considered renewable and sustainable. Nuclear power plants do not release carbon dioxide (a contributor to global climate change) or sulfur dioxide (a contributor to acid rain).
One obstacle to nuclear fission power is that radioactive nuclear waste is generated. High-level radioactive waste—the fission products in the used fuel rods—will be dangerous for the next 100 to 1,000 years. There is no known way to speed the removal of radioactivity from waste. Spent fuel rods are first cooled in large tanks, then encapsulated in ceramic or glass containers. These containers are then placed in stainless steel containers and stored. Very little high-level waste is made by a reactor in a year—enough to occupy a volume of about half a cubic yard.