c) Simon:
²²⁵Ra (β⁻, t½ = 14.9 d) →
²²⁵Ac (α, t½ = 9.92 d) →
²²¹Fr (α, t½ = 4.18 min) →
²¹⁷At (α, t½ = 32.3 ms) →
²¹³Bi (β⁻, t½ = 45.6 min) →
²¹³Po (α, t½ = 3.65 μs) →
²⁰⁹Pb (β⁻, t½ = 3.25 h) →
²⁰⁹Bi (α, t½ = 2.01 × 10¹⁹ y) (this is WAY more than the age of the universe so it’s unlikely that any atom in the sample will become tellurium in Simon’s lifetime)→
²⁰⁵Tl (stable)
Doesn't matter. They're all gonna die,so I see this as an absolute win. (Sorry,I'm old,and have heard the Christmas song enough times this makes me smile)
Yes, you happen to be correct but you can't just say that. Different isotopes of each of these elements can be many orders of magnitude more active. If I could summon a few grams of any isotope of carbon (like C-20 that decays in microseconds), I could kill you with radiation poisoning instantly.
Anyway, it’s β⁻ decay so they are all affected, plus some α from secondary products that will be mostly received by Simon.
Unless Alvin’s ²³⁵U is above critical mass, in which case they all die very quickly.
Your comment above gave the half lives of the main substances and their secondary products, right? Could you recommend any resources for someone to learn how to do what you did above?