Radioactive waste management: identify the option that is not considered a practical or accepted method for disposing of low-level radioactive waste under real-world engineering and regulatory constraints.

Introduction / Context:
Low-level radioactive waste (LLW) management prioritizes containment, isolation, and control of exposure pathways. Practical methods must be technically feasible, regulatorily acceptable, and economically sensible.

Given Data / Assumptions:

• Waste class: low-level radioactive waste.
• Criterion: practicality and acceptance in real-world programs.
• Constraints: safety, cost, reliability, and regulatory compliance.

Concept / Approach:
Practical LLW strategies include engineered near-surface disposal, decay storage, and controlled releases within strict regulatory limits in some historic contexts. Ideas like space disposal are speculative, unsafe, and prohibitively expensive, and pose catastrophic risk if a launch fails.

Step-by-Step Solution:

Verification / Alternative check:
International guidance emphasizes engineered barriers and controlled facilities; space disposal is consistently rejected on risk-cost grounds.

Why Other Options Are Wrong:

• Dilution with inert material: historically referenced in limited contexts, though modern practice favors containment; still more practical than space launch.
• Release through tall stacks after dilution: historically practiced under strict limits; not preferred today but technically real.
• Disposal in rivers or oceans: historically occurred but is now heavily restricted/forbidden; nevertheless, it existed in practice unlike space launching.
• Engineered near-surface containment: standard, practical method.

Common Pitfalls:
Assuming that anything ever tried historically is recommended today; conflating practicality with desirability. The question asks for not practical, which space disposal clearly is.

Final Answer:
Filling steel crates and launching beyond earth gravity