The “numerical Value” column above converted the values in the original references to US “traditional” units (if needed). These units include the roentgen (R), rad, rem, and disintegrations per minute (dpm).
For gamma radiation: 1 rad = 1 rem ~ 1 R
In practice, units of roentgen, rad and rem are sometimes used interchangeably because a roentgen of exposure would lead to approximately a rad of absorbed dose in tissue for the majority of photon energies of interest to the ROSS. The physical quantity exposure, in units of roentgen (R), can be converted to a corresponding radiation protection quantity such as personal dose equivalent (rem), however these conversions are photon energy dependent. Examples can be seen in the table below.
|
Photon Source (Energy) |
rem/R |
|
Am-241 (59.5 keV) |
1.66 |
|
Cs-137 (662 keV) |
1.06 |
|
Co-60 (1173 & 1332 keV) |
1.03 |
For this reason, documents often use the tilde (~) to reinforce that the roentgen (R) to dose (i.e., rad, Gy) and dose equivalent (i.e., rem, Sv) conversions are only an approximation.
If converting to SI units, the follow information may be helpful:
⚫ Hot Zone: 10 mrem/h = 0.1 mSv/h = 100 μSv/h
⚫ Dangerous Radiation Zone: 10 rem/h = 0.1 Sv/h = 100 mSv/h