Liquid Radioactive Waste Analysis
For P-32 and I-125
Click below for printable versions of the charts to use to estimate the amount of P-32 or I-125 in a full RPO-issued liquid waste container by using a portable survey meter.
For other radionuclides, or partially full containers
The best way to determine the amount of radioactive material in liquid waste is to count a 1 milliliter sample in a liquid scintillation or gamma counter when the jug is ready to be collected for disposal. Follow these steps:
- Count the sample for 1 to 10 minutes.
- Obtain the disintegration rate (dpm) of the sample by dividing the obtained count rate (cpm) by the instrument counting efficiency for that radionuclide.
- Correct this result for the total volume of the container, by multiplying the result by the volume of the container divided by the volume of the sample. A full container holds approximately 9,500 milliliters. So, for a jug filled to the fill line, and a 1 millilter sample, multiply the result by 9,500.
- Convert the disintegration rate to mCi units, where 1 mCi = 2.22 x 109 dpm.
For example, if a sample of tritium waste counted in an LSC with an efficiency of 50% had 10,000 net cpm, there would be 20,000 dpm of tritium in the sample.
sample dpm = 10000cpm / 0.50 = 20000 dpm
The jug would then have a total of 1.9 x 108 dpm of tritium.
jug dpm = sample dpm x (jug mL / sample mL)
jug dpm = 20000 dpm x (9500 mL / 1 mL)
jug dpm = 1.9 x 108 dpm
Converting to milliCuries, we have a total of 0.086 mCi of tritium in the jug.
jug mCi = (jug dpm) / (2.22 x 109 dpm / mCi)
jug mCi = 0.086 mCi