Comparison of TLD and DRD Results

  

The BRMD  TLD badge  is the only dosimeter recognized by the regulatory authorities and is the dosimeter of record at TRIUMF. DRDs are often used when immediate dose information is required for dose control purposes. DRD results, are not an official record unless used as an estimate when a TLD result is not available.

Difference in doses measured by a TLD and a DRD are to be expected for the following reasons:

1. TLDs  and DRDs  have a somewhat different energy response.
2. A large number of dosimeters, of either type, placed in the same radiation field will show a variation of up to 20% in their readings.
3. DRDs may read high in fields where high energy beta particles exist.
4. DRDs suffer from leakage and mechanical shock which can alter readings.
5. Small rounding off errors made in each reading are cumulative and can distort the value of cumulative doses derived from DRD readings.

If the two dosimeters are worn side by side all the time the DRD reading should be within 25% of the TLD result most of the time.