1. The problem statement, all variables and given/known data A tube containing a isotope of radon, 22286Rn, is to be implanted in a patient. The radon has an initial activity of 1.6 * 104 Bq, a half-life of 4 days and it decays by alpha emission. To provide the correct dose, the tube, containing a freshly prepared sample of the isotope, is to be implated for 8 days. (a) (i) What are the proton (atomic) number and the nucleon (mass) number of the daughter nucleus produced by the decay of the radon? (a) (ii) State one reason why an alpha emitter is preferred to a beta or gamma emitter for such purposes? (b) Determine: (i) the decay constant for radon in s-1, (ii) the initial number of radioactive radon atoms in the tube. (c) The operation to implant the tube has to be delayed. Ignoring the effects of any daughter products of the decay, determine the maximum delay possible if the patient is to receive the prescribe dose using the source. Answers: (b) (i) 2.0 * 10-6 s-1, (ii) 8.0 * 109, (c) 40 hours. 2. The attempt at a solution (a) (i) 22286Rn → 21884Po + 42α. (a) (ii) No idea. Maybe α is less harmful for health? (b) (i) λ = ln 2 / 345 600 = 2 * 10-6 s-1. (b) (ii) dN / dt = - λ N → N = (dN / dt) / λ = 16 000 / 2 * 10-6 = 8 * 109 atoms. (c) A = A0 e- λ t = 16 000 e- 2 * 10-6 * 691 200 = 4016 Bq. This should be the activity after 8 days. But how to determine the maximum possible delay? I though of something like 0 = 4016 e- 2 * 10-6 * t and solve for t, but doesn't look like mathematically solvable. Any help please on bold problems (a) (ii) and (c)?