Naturally Occurred Radioactive Materials (NORMS) in Oil and Gas Production

Excerpt from Austrialina Radiation Protection and Nuclear Safety Aency. (2008). Safety Guide Radiation protection series No.15 Management of Naturally Occurring Radioactive Material (NORM)

Austrialina Radiation Protection and Nuclear Safety Aency. (2008). Safety Guide Radiation protection series No.15 Management of Naturally Occurring Radioactive Material (NORM) .

The decay chain starting with 222Rn can be conveniently grouped into two:

• The short-lived radon decay products ²¹⁸Po, ²¹⁴Pb, ²¹⁴Bi and ²¹⁴Po have a collective half-life of approximately 30 minutes, which means that they will grow in to a stream containing just ²²²Rn within 30 to 60 minutes; if separated from the ²²²Rn they will decay with a half-life of approximately 30 minutes.

• The longer-lived radon decay products consisting of ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po. The 21 year half life of ²¹⁰Pb means that while these grow in to radioactive equilibrium with the parent ²²²Rn slowly, they persist in equipment for significant periods.

As all the decay chain members below radon are solids, they will not indefinitely follow the fluid flow lines in the equipment. Instead they will tend to accumulate at points of impaction, such as control valves, orifice plates, pump suction strainers and pump impellers, and will also accumulate where flows are very low, such as in a storage vessel. There is also the possibility of a thermal precipitation effect in heat exchangers. These accumulation points can be thought of as being inefficient filters, which separate the radon from its decay products.