Nuclear physics-part (2)

Total Questions: 45

31. With reference to India, consider the following statements: [I.A.S. (Pre) 2022]

1. Monazite is a source of rare earths.

2. Monazite contains thorium.

3. Monazite occurs naturally in the entire Indian coastal sands in India.

4. In India, Government bodies only can process or export monazite.

Which of the statements given above are correct?

(a) 1, 2 and 3 only
(b) 1, 2 and 4 only
(c) 3 and 4 only
(d) 1, 2, 3 and 4

Correct Answer: (b) 1, 2 and 4 only

Solution:Monazite is a complex reddish-brown phosphate of thorium and rare earth minerals [(Ce, La, Nd, Th, Y) PO, and this is radioactive in nature. In India, monazite is the principal source of rare earths and thorium. Monazite bearing economic heavy mineral deposits are found along the coastal and inland placer sands of the country. However, monazite is not found in entire Indian coastal sands.

Atomic Minerals Directorate for Exploration and Research (AMD), a constituent unit of Department of Atomic Energy (DAE) has so far established 12.73 million tonnes (as per 2020 estimates) of monazite contained in 130 deposits in the coastal beach placer sands in parts of Kerala, Tamil Nadu, Odisha, Andhra Pradesh, Maharashtra and Gujarat and in the inland alluvium in parts of Jharkhand, West Bengal and Tamil.Nadu. These deposits have been formed naturally due to littoral action of sea waves coupled with wind action. In India, private firms are restricted from processing or exporting monazite. Monazite is a strategic mineral and cannot be sold in commercial market. It is a prescribed substance to be handled by the DAE. IREL (Indian Rare Earths Limited), a Government of India Undertaking under the DAE and KMML (The Kerala Minerals and Metals Ltd.), a Kerala State Government Undertaking, are actively engaged in mining and processing of beach sand minerals from placer deposits. IREL is the only entity processing monazite to produce thorium and rare earth (RE) compounds.

32. With reference to the radioactivity, which of the following statements is/are correct? [U.P. P.C.S. (Pre) 2021]

1. Radioactivity is a nuclear property.

2. Hydrogen bomb is prepared on the principle of nuclear fission.

Select the correct answer using the codes given below.

Codes:

(a) Only 1
(b) Only 2
(c) Both 1 and 2
(d) Neither 1 nor 2

Correct Answer: (a) Only 1

Solution:Radioactivity is a nuclear phenomenon in which an unstable atomic nucleus undergoes a decay. In this process, unstable atomic nucleus loses energy by radiation. It is the process of spontaneous emission of alpha, beta and gamma radiations from the nuclei of an atom. Hence, statement 1 is correct.

Statement 2 is incorrect as hydrogen bomb is prepared on the principle of nuclear fusion in which nuclei of isotopes of hydrogen combine under extremely high temperature to form helium nucleus.

33. To meet its rapidly growing energy demand, some opine that India should pursue research and development on thorium as the future fuel of nuclear energy. In this context, what advantage does thorium hold over uranium? [I.A.S. (Pre) 2012]

1. Thorium is far more abundant in nature than uranium.

2. On the basis of per unit mass of mined mineral, thorium can generate more energy compared to natural uranium.

3. Thorium produces less harmful waste compared to uranium.

Which of the statement (s ) given above is/are correct?

(a) Only 1
(b) 2 and 3
(c) 1 and 3
(d) 1, 2, and 3

Correct Answer: (d) 1, 2, and 3

Solution:Thorium is more abundant in Earth's crowd than uranium at a concentration of 0.0006% vs. 0.00018% for Uranium 3 times) On the basis of per unit mass of mined mineral, thorium can generate more energy compared to natural uranium. Thorium cycles exclusively allow thermal breeder reactors (as opposed to fist brenders) Thorium cycle does not irradiate U-238 and therefore does not produce transuranic (bigger than uranium) a tons like plutonium, americium, curium, etc. These transuranics are the major health concern of long-term nuclear waste. Also the thorium fuel generates no new bomb-usable material in the waste profile.

34. Consider the following statements: [I.A.S. (Pre) 2023]

Statement-I: India, despite having uranium deposits, depends on coal for most of its electricity production.

Statement-II: Uranium, enriched to the extent of at least 60%, is required for the production of electricity. Which one of the following is correct in respect of the above statements?

(a) Both Statement-I and Statement-II are correct and Statement-II is the correct explanation for Statement-1
(b) Both Statement-I and Statement-II are correct and Statement-II is not the correct explanation for Statement-1
(c) Statement-I is correct but Statement-II is incorrect
(d) Statement-1 is incorrect but Statement-II is correct

Correct Answer: (c) Statement-I is correct but Statement-II is incorrect

Solution:

Statement-I: India, despite having uranium deposits, depends on coal for most of its electricity production. This statement is correct.

India does have some uranium deposits, primarily in states like Jharkhand, Andhra Pradesh, and Telangana. However, the extent of these economically viable deposits is limited compared to India's massive energy needs. As a result, coal remains the dominant fuel source for electricity generation in India.

Statement-II: Uranium, enriched to the extent of at least 60%, is required for the production of electricity. This statement is incorrect.

Uranium enrichment levels required for electricity production in typical nuclear power reactors are significantly lower than 60%. Most commercial nuclear power plants that use enriched uranium fuel operate with enrichment levels of around 3% to 5% of Uranium-235. Uranium enriched to 60% or higher is typically classified as Highly Enriched Uranium (HEU) and is used in specialized research reactors or nuclear weapons, not standard electricity-generating reactors.

Therefore, Statement-I is correct, and Statement-II is incorrect.

35. The half-life of a radioactive substance is 10 days; it means there will be : [R.A.S/R.T.S.(Pre) 2007]

(a) complete decay of substance in 20 days.
(b) complete decay of substance in 40 days.
(c) decay of 3/4 part of substance in 20 days.
(d) decay of 1/4 part of substance in 5 days.

Correct Answer: (c) decay of 3/4 part of substance in 20 days.

Solution:The half life of a radioactive substance is 10 days; it means in next 10 days there will be half of the remaining radioactive substance. Thus, in total 20 days, there will be decay of 75% or 3/4 part of substance.

(1/2+1/4)=3/4

let total amount is 100 unit.

In 10 days half of total is decay = 50 unit decay, reaming is 50 unit.

In next 10 days half of 50 unit decay = 25 unit.

now total unit decay in 20 day's = 50 + 25 = 75 unit . which is equal to 3/4 of total unit.

36. Which one of the following is not radioactive ? [I.A.S. (Pre) 2001]

(a) Astatine
(b) Francium
(c) Tritium
(d) Zirconium

Correct Answer: (d) Zirconium

Solution:Zirconium, whose atomic number is 40 is not a radioactive element. Generally, those elements whose atomic number is above 80 is considered as radioactive elements except Technetium (43) and Promethium (61). They both are radioactive elements whose atomic number is less than 80. According to the question, Astatine (atomic number 85) and Francium (atomic number 87) are radioactive elements, while Tritium is a radioactive isotope of hydrogen.

37. Which Uranium isotope is used in nuclear power plants to produce electricity? [Uttarakhand P.C.S. (Pre) 2012]

(a) U-233
(b) U-234
(c) U-235
(d) U-239

Correct Answer: (c) U-235

Solution:

U-238 and U-235 (which has 143 neutrons) are the most common isotopes of uranium. Uranium-235 is the isotope of uranium that is used in nuclear reactors. Natural uranium contains only around 0.7% of U-235 and most nuclear reactors require a U-235 concentration of between 3% and 5%. The process of increasing the concentration of U-235 is called enrichment.

38. Which metal can be used for producing electricity? [47th B.P.S.C. (Pre) 2005]

(a) Uranium
(b) Iron
(c) Copper
(d) Aluminium

Correct Answer: (a) Uranium

Solution:The main use of uranium in the civilian sector is to fuel nuclear power plants. 1 kg of U-235 can theoretically produce about 20 tera joules of energy which is equivalent to 1500 tons of Coal.

39. Radioactive substance emits - [40th B.P.S.C. (Pre) 1995]

(a) Alpha rays
(b) Beta rays
(c) Gamma rays
(d) All the above

Correct Answer: (d) All the above

Solution:Radioactive elements are elements that have an unstable nucleus. When the nuclei are considered unstable, they radiate alpha, beta and gamma radiation and is converted into a stable element. This type of radiation is invisible for naked eye.

40. What happens if the control rods are not used in a nuclear reactor? [R.A.S/R.T.S. (Pre) 1992]

(a) The reactor will stop working.
(b) Chain process would go out of bounds.
(c) The reactor will be slow to act.
(d) The reactor will continue to work as it is.

Correct Answer: (b) Chain process would go out of bounds.

Solution:Control rod constitutes a real-time control of fission process which is crucial for both keeping the fission chain reaction active and preventing it from accelerating beyond control. These rods are composed of chemical elements such as boron silver, indium and cadmium.

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Nuclear physics-part (2)