What does the phrase 'blanket death' mean?
Solution 1:
It's not a set phrase in that quote, I'd say it may mean either of two things:
- death very soon after birth (right there on their blanket) or at early age (when child lives in a crib, wrapped in a blanket)
- inevitable death, death like all other children at the time, because radiation blankets their world.
Off-topic: today there is an-almost-set-phrase "blanket death" with a completely different meaning: when a child dies due to choking on or strangulation by their blanket.
Solution 2:
Strontium 90 is a fission product produced by nuclear bombs. It is readily absorbed into bone marrow when ingested and can lead to bone cancers and leukaemia. Since strontium is chemically similar to calcium, it will be present in milk in significant quantities. The term "blanket death" is almost certainly an allusion to the global effects of an all-out nuclear war.
Wikepedia: Strontium-90