Measurement
There is no direct way to measure committed dose. Estimates can be made by analyzing the data from whole body counting, blood samples, urine samples, fecal samples, biopsies, and measurement of intake.
Whole body counting (WBC) is the most direct approach, but has some limitations: it cannot detect beta emitters such as tritium; it provides no chemical information about any compound that the radioisotope may be bound to; it may be inconclusive regarding the nature of the radioisotope detected; and it is a complex measurement subject to many sources of measurement and calibration error.
Analysis of blood samples, urine samples, fecal samples, and biopsies can provide more exact information about the chemical and isotopic nature of the contaminant, its distribution in the body, and the rate of elimination. Urine samples are the standard way to measure tritium intake, while fecal samples are the standard way to measure transuranic intake.
If the nature and quantity of radioactive materials taken into the body is known, and a reliable biochemical model of this material is available, this can be sufficient to determine committed dose. In occupational or accident scenarios, approximate estimates can be based on measurements of the environment that people were exposed to, but this cannot take into account factors such as breathing rate and adherence to hygiene practices. Exact information about the intake and its biochemical impact is usually only available in medical situations where radiopharmaceuticals are measured in a radioisotope dose calibrator prior to injection.
Annual limit on intake (ALI) is the derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year. ALI is the intake of a given radionuclide in a year that would result in:
- a committed effective dose equivalent of 0.05 Sv (5 rems) for a "reference human body", or
- a committed dose equivalent of 0.5 Sv (50 rems) to any individual organ or tissue,
whatever dose is the smaller.
Read more about this topic: Committed Effective Dose Equivalent (CEDE)
Famous quotes containing the word measurement:
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—John Dos Passos (1896–1970)