Fusion feasibility: why is commercial-scale power generation from controlled fusion reactors not yet a reality?

Introduction / Context:
Fusion promises abundant, low-carbon energy by combining light nuclei (e.g., D + T) to release large amounts of energy. However, translating this promise into an operating power plant requires meeting stringent physics and engineering conditions, notably ignition criteria and steady-state operation with net energy gain.

Given Data / Assumptions:

• Practical fuels: deuterium (abundant in seawater) and tritium (bred from lithium).
• Initiation requires extremely high temperatures and adequate particle density with sufficient confinement time.
• Lawson criterion provides the product n * T * τ_E needed for net energy.

Concept / Approach:
The central obstacle is simultaneously achieving and confining the required plasma temperature, density, and energy confinement time. Reaching these conditions without intolerable losses (radiation, turbulence, disruptions) is challenging. While control is also complex, the primary barrier to date is establishing and maintaining the initiation/ignition conditions with a positive energy balance on a commercial scale.

Step-by-Step Solution:

Verification / Alternative check:
Experimental devices have achieved significant fusion yields for short periods, but continuous, economically viable operation with robust tritium breeding and power conversion remains unrealized.

Why Other Options Are Wrong:

• (a) “Control” is challenging, but the chief barrier has been achieving ignition-level conditions long enough for net energy.
• (b) Deuterium is abundant; tritium can be bred from lithium—scarcity is not the primary blocker.
• (d) Fusion requires tiny fuel masses; the issue is conditions, not quantity.
• (e) Neutron effects matter for materials, not immediate plasma “poisoning.”

Common Pitfalls:
Assuming fuel supply is the main limitation; conflating plasma control issues with the more fundamental challenge of reaching and sustaining ignition parameters.

Final Answer:
It is difficult to initiate fusion by achieving and confining the required temperature and density.