Accumulation of 210Pb activity on particulate matter in LPG rail cars

The presence of radon in petroleum natural gas has been known for over 90 yr. Typical activity concentrations in Western Canada vary from 5 to 20 Bq/L. In Canada, liquified natural gas is transported over large distances by rail cars with capacities of approx. 105 L. At least every 10 yr, the gas vessels of these cars are tested hydrostatically. During this operation, about 10 L of fine ferric dust is found to have accumulated inside the vessels and this is cleaned out. The dust has been found to consist of flakes of about 200μ in size which has accumulated 210Pb and daughter activities. The specific activities have been measured for a composite sample by beta and alpha spectrometry and have been found to be similar to activities previously reported for the interior surfaces of valves and separators in natural gas processing plants.