The Voyager I space probe is powered by a generator that usesplutonium-238 (238Pu) as a fuel source. Plutonium-238 has ahalf-life of 87.7 years. If Voyager I was launched in 1977, whatpercentage of the original 238Pu will remain in 2025, the year inwhich Voyager I is expected to cease operation?

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N. Korea restarts plutonium production for nuclear bombs