of a worst-case scenario where the reactor housing fails and radiation is released to the atmosphere. In your evaluation, you determine that 120 kg of lodine-131 (a radioisotope that causes thyroid gland and liver damage) could be released into the atmosphere. a. Assuming the release of lodine-131 is very rapid and all of it is uniformly distributed through the valley's atmosphere with none escaping the valley, what would the concentration of lodine-131 be in the valley's air? Your answer should be expressed in units of ppm by volume. You may assume an atmospheric pressure of 1 atm and a temperature of 20°C. b. Assuming the lodine-131 concentration you calculated in part a is the initial concentration in the valley, you would now like determine how long it will take for the concentration to decrease to the safe limit of 1.0x 10-° ppm. The average wind speed through the valley (entering at one end of the 15-km length of the valley and exiting at the other end) is only 1.5 m/min. However, lodine-131 is also removed by radioactive decay with a half-life of 8.1 days. How much time is needed for the concentration to drop to the safe limit?

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