Indexed on: 12 Jul '08Published on: 12 Jul '08Published in: Health physics
The contribution of 228Ra progeny to the gross alpha-particle activity of water samples by EPA Method 900.0 is investigated as a function of residue mass and geometry and time between sample collection and analysis. It is shown that these factors can cause the contribution of 228Ra progeny to gross alpha-particle activity to be up to 2.2 times the initial 228Ra activity for grab samples and up to 3.5 times the initial 228Ra activity for quarterly composite samples when samples are held for the maximum 6-mo holding time. Thus, under some conditions, 228Ra, by itself, can cause a gross alpha-particle violation (>0.55 Bq L(-1)). Since 228Ra activity is already regulated, a gross alpha-particle activity violation that only exists because of the presence of 228Ra can be considered to be a false positive violation.