<h4>Introduction to PFBR Criticality</h4><p>The <strong>Atomic Energy Regulatory Board (AERB)</strong> recently granted a crucial permission for the <strong>“First Approach to Criticality”</strong> of India's <strong>500 MWe Prototype Fast Breeder Reactor (PFBR)</strong>.</p><p>This significant milestone occurred at <strong>Kalpakkam, Tamil Nadu</strong>, marking a major step forward for India's indigenous nuclear power program.</p><div class='info-box'><p>📍 <strong>Location:</strong> Kalpakkam, Tamil Nadu</p><p>⚡ <strong>Capacity:</strong> 500 MWe</p><p>🇮🇳 <strong>Significance:</strong> India's first indigenous <strong>PFBR</strong></p></div><h4>Understanding Nuclear Criticality</h4><p><strong>Criticality</strong> is a fundamental concept in nuclear reactor operation. It represents a state where a self-sustaining nuclear chain reaction is achieved.</p><p>This occurs when the rate of neutron production from nuclear fission precisely balances the rate of neutron loss due to absorption or leakage.</p><div class='key-point-box'><p><strong>Criticality:</strong> The state in a nuclear reactor where the number of neutrons produced by fission exactly replaces those lost through leakage or absorption, maintaining a constant neutron population for a self-sustaining chain reaction.</p></div><h4>Fission vs. Fusion: Key Nuclear Processes</h4><p>While the <strong>PFBR</strong> operates on the principle of nuclear <strong>fission</strong>, nuclear energy discussions often contrast it with nuclear <strong>fusion</strong>.</p><p>Both are powerful nuclear processes, but they involve different mechanisms for releasing energy from atomic nuclei.</p><div class='exam-tip-box'><p><strong>UPSC Insight:</strong> Understanding <strong>criticality</strong> and the working principles of different reactor types (like <strong>FBRs</strong>) is vital for <strong>GS Paper 3</strong>, particularly for questions on India's energy security and nuclear policy.</p></div>