Prelims · Science & technology · 32 questions

Defence, nuclear & energy technology

Every UPSC Prelims question on this topic, 2016–2026, newest first. Tap an option to check yourself; the answer and explanation open below it.

Asked in 9 of 11 years · most in 2026 (4)

UPSC syllabus: “General Science.” See the full syllabus →

Prelims 2017 · Q22

Medium

It is possible to produce algae based biofuels, but what is/are the likely limitation(s) of developing countries in promoting this industry?

1.Production of algae based biofuels is possible in seas only and not on continents.
2.Setting up and engineering the algae based biofuel production requires high level of expertise/technology until the construction is completed.
3.Economically viable production necessitates the setting up of large scale facilities which may raise ecological and social concerns.

Select the correct answer using the code given below:

Answer & explanation

Answer: (b) 2 and 3 only

Algae for fuel are grown on land, in open ponds or closed photobioreactors, often on non-arable land with non-potable water, so statement 1 is false. The real hurdles for a developing country are the engineering know-how needed and the very large scale (land, water, nutrients, CO2) needed to make it pay.

✗ 1. Algae are cultivated on land in open raceway ponds, attached-growth systems and closed photobioreactors; non-arable land is listed as one of the resources for growing them.
✓ 2. Designing cultivation systems that keep resource use and costs low while keeping productivity high, and then harvesting and processing the biomass, needs advanced technology and skills.
✓ 3. An algal biofuel industry has to scale up to use a large amount of land, water, nutrients and CO2, which can compete with other uses and raise ecological and social concerns.

Remember · Algal (third-generation) biofuel: grown on land in ponds or photobioreactors, even on non-arable land with saline or waste water; the limits are technology and the scale needed to be viable.

Sources

US Department of Energy, Bioenergy Technologies: Algal Production ↗ “grow algae viably include non-arable land, non-potable water, waste nutrient streams, waste carbon dioxide, sufficient sunlight, and supporting infrastructure to access downstream processing operations. Development of an algal biofuel industry requires scaling up to use a significant amount of these resources. … open ponds, attached growth systems, and closed photobioreactors. Cultivation systems must minimize resource use and costs while maximizing productivity.”

Question and answer: UPSC's official GS Paper I (2017, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2017 · Q25

Easy

In the context of mitigating the impending global warming due to anthropogenic emissions of carbon dioxide, which of the following can be the potential sites for carbon sequestration?

1.Abandoned and uneconomic coal seams
2.Depleted oil and gas reservoirs
3.Subterranean deep saline formations

Select the correct answer using the code given below:

Answer & explanation

Answer: (d) 1, 2 and 3

Geological carbon storage injects captured CO2 deep underground into porous rock sealed by an impermeable cap. Saline formations, oil and gas reservoirs and unmineable coal seams are all standard candidate sites, so all three are correct.

✓ 1. Coal that cannot be mined economically can adsorb CO2 on its surfaces; unmineable coal seams are one of the formation types studied for storage.
✓ 2. Oil and gas reservoirs held fluids for millions of years under a sealing layer, so once depleted they can hold injected CO2; injection can also push out extra oil.
✓ 3. Deep saline formations (porous rock filled with brine) have the largest storage capacity and are the main target for large-scale storage.

Remember · Geological CO2 storage sites: deep saline formations, depleted oil and gas reservoirs, unmineable coal seams (also organic-rich shales and basalt).

Sources

US Department of Energy, NETL: Carbon Storage FAQs ↗ “The U.S. Department of Energy (DOE) is investigating five types of underground formations for geologic carbon storage: Saline formations Oil and natural gas reservoirs Unmineable coal seams Organic-rich shales Basalt formations … Carbon capture and storage (CCS) is the separation and capture of carbon dioxide (CO 2 ) from the emissions of industrial processes prior to release into the atmosphere and storage of the CO 2 in deep underground geologic formations.”

Question and answer: UPSC's official GS Paper I (2017, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2017 · Q28

Medium

Consider the following statements:

1.The Nuclear Security Summits are periodically held under the aegis of the United Nations.
2.The International Panel on Fissile Materials is an organ of International Atomic Energy Agency.

Which of the statements given above is/are correct?

Answer & explanation

Answer: (d) Neither 1 nor 2

The Nuclear Security Summits were a US-initiated series of leaders' meetings (2010–2016), not a UN process, and the International Panel on Fissile Materials is an independent group of experts, not part of the IAEA. Both statements are wrong.

✗ 1. The summit process was announced by US President Barack Obama in April 2009. Four summits were held (Washington 2010, Seoul 2012, The Hague 2014, Washington 2016), hosted by those countries, not by the UN.
✗ 2. The IPFM was founded in January 2006 as an independent panel of experts drawn from countries with and without nuclear weapons; it studies fissile material policy and is not part of the IAEA.

Remember · Nuclear Security Summits: Obama's initiative, four summits 2010–2016, outside the UN. IPFM (2006): independent expert panel on fissile material, not an IAEA body.

Sources

Arms Control Association: The Nuclear Security Summit at a Glance ↗ · reference work “The nuclear security summit initiative was announced in an April 2009 speech by U.S. President Barack Obama, in which he pledged to hold a global summit on nuclear security in 2010 … There were four summits in total: in Washington, D.C. in 2010 , Seoul, South Korea in 2012 , the Hague, Netherlands in 2014 and Washington, D.C. again in 2016.”
The White House (archived), 1 April 2016: Nuclear Security Summit 2016 Communiqué ↗ “We, the leaders, gathered in Washington, D.C. on the first day of April, 2016 on the occasion of the fourth Nuclear Security Summit”
International Panel on Fissile Materials: About IPFM ↗ · reference work “The International Panel on Fissile Materials (IPFM) was founded in January 2006 and is an independent group of arms-control and nonproliferation experts from both nuclear weapon and non-nuclear weapon states.”

Question and answer: UPSC's official GS Paper I (2017, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

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