High Activity Sealed Sources (HASS) Radioactivity Thresholds
Published: Dec 07, 2024
Source: Ionactive Radiation Protection Resource
A radioactive sealed source becomes a High Activity Sealed Source (HASS) when its activity exceeds a threshold which is radionuclide specific. The activity values are based on the "D values " which are published by IAEA in the document IAEA Safety Guide RS-G-1.9 (Categorization of Radioactive Sources).
We have produced some specific guidance on D-values here: Ionactive guidance: Sealed source category and the 'D' value.
A HASS source ceases to be HASS when its activity has decayed below the activity threshold.
High Activity Sealed Source (HASS) radioactivity thresholds
All the values listed below are in GBq (109 Bq). By definition, the values listed below are also "D Values" which are used in the security classification of sealed radioactive sources.
| Radionuclide | Symbol | HASS threshold (GBq) |
|---|---|---|
| Americium 241 | Am-241 | 60 |
| Barium 133 | Ba-133 | 200 |
| Caesium 134 | Cs-134 | 40 |
| Caesium 137 | Cs-137 | 100 |
| Californium 252 | Ca-252 | 20 |
| Cobalt 57 | Co-57 | 700 |
| Cobalt 60 | Co-60 | 60 |
| Europium 152 | Eu-152 | 60 |
| Gadolinium 153 | Gd-153 | 1000 |
| Germanium 68 | Ge-68 | 70 |
| Iridium 192 | Ir-192 | 80 |
| Polonium 210 | Po-210 | 60 |
| Radium 226 | Ra-226 | 40 |
| Selenium 75 | Se-75 | 200 |
| Sodium 22 | Na-22 | 30 |
| Sodium 24 | Na-24 | 20 |
| Strontium 90 | Sr-90 | 1000 |
For more information on the safety aspects HASS sources - visit Dose Rates from HASS (High Activity Sealed Sources).