14 The radioactive isotope of polonium, 218Po, decays by the emission of an -particle with a half-life of 183 s. a In an accident at

• 14 The radioactive isotope of polonium, 218Po, decays by the emission of an α-particle with a half-life of 183 s. a In an accident at a reprocessing plant some of this isotope, in the form of dust, is released into the atmosphere. Explain why a spillage in the form of a dust is very much more dangerous to health than a liquid spillage. [2] b It is calculated that 2.4 g of the isotope is released into the atmosphere. Calculate the initial activity of the released polonium. [4] c It is felt that it would safe to re-enter the laboratory when the activity falls to background, about 10 Bq. Calculate how many hours must pass before it is safe to re-enter the laboratory. [3]