Question

The beaches in Kerala are radioactive due to
A) Uranium- 238
B) Radon- 222
C) Radium- 224
D) Thorium- 232

Answer 1

The coastal belt of Karunagappally, Kerala, India, is known for its high radiation from the black sand containing radioactive elements.

Complete answer:
Kerala has the world’s highest level of natural radioactivity in a densely populated area. The black sand contains radioactive elements, mainly, thorium and monazite. Its long-term exposure may lead to diseases like cancer. The most stable isotope of Thorium is Thorium 232 with a half-life of 14.05 billion years.

Additional information: Thorium is a weak radioactive metallic chemical element with the symbol Th and atomic number 90. It is silvery in color and can turn into black when exposed to air, forming thorium oxide. It is reactive and can ignite in air when it is finely divided. Thorium is hard, malleable and has a high melting point. Thorium, bismuth and uranium are the only three radioactive elements, on earth, that still occur naturally in large amounts as the primitive elements. Thorium is present almost three times more than uranium in the earth’s crust and is mainly refined from monazite sands.
Monazite is the most important commercial source of thorium as it occurs in large deposits worldwide, mainly in India, South Africa, Brazil, Australia and Malaysia. It contains 2.5% – 20% thorium in it. Monazite is a chemically unreactive material that is found as yellow or brown sand. Its low reactivity makes it difficult to extract thorium.
Thorium can fulfill world energy demands for longer as it is more abundant than uranium. Its fuels result in a safer and better-performing reactor core as thorium oxide has a higher melting point, higher thermal conductivity, and a lower coefficient of thermal expansion.

Hence, the correct option is D, ‘Thorium 232’.

Note: There are other places in China, Iran and Brazil with natural radiation, but the Kerala coast is believed to be the only one with high radiation levels with a high population density.