1. During a 40h underground working week radiological monitoring indicates that a miner is subjected to the following levels and periods of exposure to radon daughters
20 h at 0.15 WL
15 h at 0.2 WL
5 h at 0.4 WL
Determine the cumulative exposure in WLM for that week.
2. In a given stope 250 m2 of ore and 200 m2 of waste rock surface are exposed. The stope also contains 300 tonnes of broken ore. Assuming the ore has a density of 2000 kg/m3, determine the rate of emanation into the stope given the following:
J (ore) = 550 pCi/m2s
B (ore) = 600 pCi/m3s
J (waste) = 85 pCi/m2s
3. The airflow is 25 m3/s in a 1000m long airway of perimeter 14m and cross sectional area 12 m2. If the initial concentration of radon in the airway is 20 pCi/l, there is an initial radon daughter activity of 0.05 WL at the entry and the rate of emanation J = 265 pCi/m2, determine the following:
• The working level of radon daughters at exit due to the initial radon
• The activity of radon daughters at outlet due to radon emitted from the rock surfaces
• The activity of radon daughters at outlet due to decay of radon daughter products available at entry
• The total working level of radon daughters leaving the airway
4. Moist air has a dry bulb temperature of 30 °C and a wet bulb temperature of 25 °C, if the pressure is 100 kPa, calculate the following using either formula or a 100 kPa psychrometric chart.
• moisture content
• specific enthalpy
• relative humidity
• sigma heat
• specific volume
• density If the airflow is 30 m3/s, calculate the air mass flow rate.
5. Calculate the same properties as in the previous question for a saturated airstream with a temperature of 26 °C at a pressure of 100 kPa using either formulae and/or chart. (NB For saturation the dry and wet bulb temperatures are equal).