10 (A410U10-1) Examiner only 12. In 2011 a tsunami damaged the Fukushima nuclear plant in Japan. The radioactive material that escaped consisted of many isotopes. Contaminated water from the site was analysed in the immediate aftermath of the incident, with the levels of radioactivity due to each isotope noted. (a) The main radioactivity detected was beta radiation. Give a reason why it is unlikely that alpha radiation would be detected from a solution contained in a sample tube. [1] (b) State what is meant by gamma radiation. [1] (c) Give a reason why radioactivity is harmful to living things. [1] (d) Arsenic-74 can decay either by emission of a beta particle or by emission of a positron. Identify the isotope formed by emission of a positron. [1] Element ................................................................... Mass number ................................................................... © WJEC CBAC Ltd. Isotope Half-life Radioactivity / Bq per cm3 of solution Type(s) of radioactivity emitted Product of decay chlorine-38 37 minutes 1.9 × 106 beta 38Ar arsenic-74 18 days 3.9 × 102 yttrium-91 59 days 5.2 × 104 beta 91Zr iodine-131 8 days 2.1 × 105 beta 131Xe caesium-134 2 years 1.6 × 105 beta 134Ba caesium-136 13 days 1.7 × 104 beta 136Ba caesium-137 30 years 1.8 × 106 beta and gamma 137Ba lanthanum-140 1.6 days 3.4 × 102 beta 140Ce (A410U10-1) Turn over. A 410 U101 11 11 Examiner only (e) The Becquerel (Bq) is a unit of radioactivity which is equivalent to the decay of 1 nucleus per second. (i) Calculate the mass of xenon-131 produced per minute from 1 cm3 of the solution. [3] Mass = ....................................................... g (ii) Identify which original isotope is present in the greatest concentration in the solution. Explain your answer. [2] (f) After studying the data, it was suggested that the affected area around the reactor would be safe after 60 years as this is twice the half-life of the longest lived isotope in the sample. Give two reasons why this suggestion is incorrect. [2] © WJEC CBAC Ltd. 11