What paradoxical risk is associated with using thick passive shielding against GCRs inside a spacecraft?

Answer

It can create a cascade of secondary, lower-energy particles inside the habitat.

When highly energetic GCRs strike thick shielding materials, they interact to produce secondary particles that can also deposit damaging energy within the biological systems of the crew.

What paradoxical risk is associated with using thick passive shielding against GCRs inside a spacecraft?
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