Which one of the following metals is alloyed with sodium to transfer heat in a nuclear reactor ?
- A.Potassium
- B.Calcium
- C.Magnesium
- D.Strontium
Correct answer
Explanation
The correct answer is A, Potassium. An alloy of sodium and potassium, called NaK, stays liquid at room temperature and carries heat away from the core of some nuclear reactors.
Liquid metals make good coolants because they conduct heat very well and stay liquid over a wide range of temperatures without needing high pressure. Sodium alone melts at about 98 degrees Celsius, but mixing it with potassium lowers the melting point well below zero, so the coolant does not freeze in the pipes. Fast breeder reactors, such as India's at Kalpakkam, use liquid sodium as coolant.
B is wrong because calcium is not used with sodium as a reactor coolant; it is a hard metal with a high melting point. C is wrong because magnesium is used in light alloys and in early reactor fuel cladding, not as a liquid coolant with sodium. D is wrong because strontium is known for red fireworks and its radioactive isotope Sr-90, not as a coolant.
Exam tip: NaK, the sodium-potassium alloy, is a liquid metal coolant; fast breeder reactors use liquid sodium.
Practice Questions
View allWhich one of the following is monatomic?
- A.Hydrogen
- B.Sulphur
- C.Phosphorus
- D.Helium
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A monatomic element exists as single, separate atoms. Helium is a noble gas of group 18: its only shell, the first, is full with two electrons, so a helium atom has no tendency to share or transfer electrons and does not bond even with another helium atom.
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- A.80 mm of Hg
- B.100 mm of Hg
- C.120 mm of Hg
- D.140 mm of Hg
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- A.Archaeologists
- B.Anthropologists
- C.Palaeontologists
- D.Geologists
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Read the full explanation →Which of the following catalytic systems is used for the reduction of unsaturated hydrocarbon to saturated hydrocarbon?
- A.Copper and H2
- B.Iron and H2
- C.Zinc and H2
- D.Nickel and H2
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Read the full explanation →Which one among the following is not a plant hormone ?
- A.Gibberellins
- B.Abscisic acid
- C.Auxins
- D.Thyroxine
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Thyroxine is an animal hormone, made by the thyroid gland in the neck, and it controls the rate of metabolism in the human body.
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