90Sr is one of the most deadly products of nuclear ?ssion. Assume that 4% of the ?ssion fragment yield from a 235U atomic bomb is 90Sr. In a nuclear interchange on the planet Inhospitable, 1000 atomic bombs, each corresponding to the ?ssion of 100 kg of 235U, are detonated.
(a) How many atoms of 90Sr are released?
(b) Assuming the 90Sr is spread evenly over the planet of diameter 12,000 km, what is the resulting activity for each m2? The half-life of 90Sr is 28.8 y.