Radiation and Phosphogypsum (18696) # // Reply /Next/ /Previous/ * Geo>K0FF Mar 14, 2010 View Source Radiation and Phosphoric Acid + The phosphoric acid produced in Florida contains much of the uranium that was present in the mined ore, but little of the radium. + In the past, uranium was valuable enough that extraction facilities at the chemical plant sites were used to concentrate and remove it from the phosphoric acid as a solid product. Since the uranium is present only at trace quantities, this was an expensive process. + Removal of uranium as a product is no longer profitable and all of the extraction facilities have been dismantled. The uranium that remains in the phosphoric acid and fertilizer products is at a low enough level that it is safe for use. Radiation and Phosphogypsum o Both natural gypsum and phosphogypsum contain radioactivity, but phosphogypsum contains more. o In the manufacture of phosphoric acid, the acid is filtered through cloth to remove solids. The radium is filtered out with the solids. The solid portion is known as phosphogypsum. o Phosphogypsum produced in North Florida contains roughly 5 – 10 picocuries per gram (pCi/g) of radium while phosphogypsum from Central Florida contains about 20 – 35 pCi/g radium. o The U.S. EPA prohibits the use of phosphogypsum. An exception is made for phosphogypsum with an average concentration less than 10 pCi/g radium which can be used as an agricultural amendment. EPA's ban was based on a single scenario which assumed that the by-product was used in road building or as an agricultural ammendment and 100 years later a house was built on the farm field or the abandoned road and the homeowner lived in the house 70 years, staying in the house 18 hours a day. Under this scenario the homeowner's risk of radon-related health concerns only slightly exceeded the EPA's acceptable limits. o Phosphogypsum is primarily calcium sulfate, and plants need the sulfur it contains. Since much of the North Florida phosphogypsum is below the EPA restriction level, it can be used as a crop amendment, but for no other use. o The Central Florida phosphogypsum is restricted to storage on land in large piles called “stacks.” o The overall radioactivity in the stacked phosphogypsum is actually less than what was in the original phosphate ore that was taken out of the ground. *NOTE: I am still seeking a gallon size container of phosphogypsum from the central Florida stacks for analysis and display purposes. Geo*