Which one of the following elements is essential for the construction of nuclear reactors ?

Zirconium is the correct choice because it is the standard structural material used in reactors for fuel cladding: zirconium alloys (e.g., Zircaloy) enclose uranium fuel pellets and prevent release of radioactivity while enduring high-temperature water/steam environments. Crucially, zirconium has a very low thermal-neutron capture cross-section so it does not unduly absorb neutrons needed to sustain the chain reaction, and it exhibits excellent corrosion resistance under reactor conditions. Textbook-level sources also note zirconium among special metals used in atomic energy, confirming its central role in reactor construction and materials engineering for fuel elements [1].

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 4: The World of Metals and Non-metals > SCIENCE AND SOCIETY > p. 54