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GS Paper IUPSC Prelims 2001
Health & Medicine
Question No. 287Interactive Test Mode
00:00
+2-0.66

Q287. Consider the following statements: In a nuclear reactor, self-sustained chain reaction is possible, because: 1. more neutrons are released in each of the fission reactions. 2. The neutrons immediately take part in the fission process. 3. The fast neutrons are slowed down by graphite. 4. Every neutron released in the fission reaction initiates further fission. Which of these statements are correct?

Consider the following statements: In a nuclear reactor, self-sustained chain reaction is possible, because:

  1. more neutrons are released in each of the fission reactions.
  2. The neutrons immediately take part in the fission process.
  3. The fast neutrons are slowed down by graphite.
  4. Every neutron released in the fission reaction initiates further fission. Which of these statements are correct?
Select the correct option below (or cross out options to eliminate)
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Official Answer Key & Detailed Solution

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Official UPSC Answer KeyUPSC Prelims 2001 • Science and Technology

Correct Answer: Option (A) — 1, 2 and 3

Concept & Option Breakdown

Standard Reference Verified
  • Statement 1 is correct: Each fission of U-235 releases 2 to 3 secondary neutrons, enabling chain reaction multiplication.
  • Statement 2 is correct: Neutrons are promptly available to participate in chain propagation.
  • Statement 3 is correct: Graphite acts as a moderator to slow down fast neutrons to thermal energies, increasing their capture cross-section for fission.
  • Statement 4 is incorrect: Not every released neutron induces fission; many are absorbed by non-fissile materials (like control rods) or escape the core.
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Question Specifications & Syllabus Mapping

Examination & YearUPSC Civil Services Preliminary Examination 2001 (Q287)
Paper & Marking SchemeGS Paper I • 2 Marks (-0.66 Negative for incorrect response)
Syllabus Subject & TopicScience and Technology → Health & Medicine
Official Answer KeyOption (A) — 1, 2 and 3

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Frequently Asked Questions — UPSC Prelims 2001 Q287

What is the official answer for UPSC Prelims 2001 GS Paper I Question 287 (Science and Technology)?

The official UPSC answer key for this 2001 Science and Technology (Health & Medicine) question is Option (A): "1, 2 and 3". Correct attempts carry 2 Marks with -0.66 Negative penalty for wrong answers.

Which UPSC Prelims syllabus topic does this 2001 question belong to?

This question belongs to GS Paper I under the subject "Science and Technology" and micro-topic "Health & Medicine". You can explore all repeated questions from Health & Medicine in Acme AI's 3D Prelims PYQ Realm or practice 50 full-length and sectional tests in the APT Prelims Test Series.

How can I solve this Health & Medicine UPSC Prelims question using option elimination?

To solve Health & Medicine questions in UPSC Prelims, identify extreme modifiers, verify core NCERT conceptual definitions, and eliminate mutually contradictory statement pairs before locking your final option.

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