5. High Activity Sealed Sources (HASS)
Published: Feb 19, 2022
Source: Ionactive Resources
HASS - High Activity Sealed Source
HASS means High Activity Sealed Source. HASS in the UK came into force as the: ‘High-activity Sealed Radioactive Sources and Orphan Sources Regulations 2005’. These regulations only applied to very high activity sources (e.g. for Cs-137 the activity needs to exceed 100 GBq) – typically those found in irradiators and radiography equipment. Users of such sources need to apply much more stringent security procedures and prove that they have the funds to dispose of such sources at the end of their useful life.
[Note: Originally the HASS threshold for Cs-137 was 20 GBq. This, and other radionuclide HASS thresholds were at the time based on IAEA A1 transport values. This was amended by BSSD Council Directive 2013/59/EURATOM and since then the HASS thresholds have been based on the IAEA-D values, these are discussed in more detail in this section of the resource: 6. Sealed source category and the 'D' value. You may also wish and visit the IAEA document which is here: Dangerous Quantities of Radioactive Material (D-Values) (will open in a new tab). ]
HASS is now taken care of by The Environmental Permitting (England and Wales) Regulations 2016 in England and Wales (which covers the same conditions from within Schedule 23). In Scotland, the Environmental Authorisations (Scotland) Regulations 2018 deal with HASS, and in Northern Ireland the Radioactive Substances Act (1993) deals with radioactive substances but the High-activity Sealed Radioactive Sources and Orphan Sources Regulations 2005 are still in force.
Drop and RUN !
Examples of HASS source thresholds
- Am-241 (60 GBq)
- Cs-137 (100 GBq)
- Cf-252 (20 GBq)
- Co-60 (30 GBq)
- Ir-192 (80 GBq)
- Ra-226 (40 GBq)
- Se-75 (200 GBq)
A HASS source ceases to be a HASS source when it's activity drops below the threshold value.
This was not always the case, the 2005 HASS regulations noted earlier referred to Annex I, Table A, column 2 of Council Directive 96/29/EURATOM - the activity values here were HASS thresholds below which a source needed to decay before they fell outside of HASS requirements. For Cs-137 this was 10 kBq (!) - quite unworkable, especially for shorter half life radionuclides such as Ir-192 (74 days) where the threshold was also 10 kBq.