Office for Nuclear Regulation

High-Activity Sealed Radioactive Sources (HASS) on Nuclear Licensed Sites


High-Activity Sealed Radioactive Sources (HASS) are potentially hazardous, and as such are subject to a rigorous regulatory regime. The EU Basic Safety Standards Directive (BSSD) 2013/59/EURATOM sets out requirements for the control of HASS, including requirements for maintaining accurate and up to date records of the location, composition and activity level of all HASS held in EU Member States. The detail of how this requirement is implemented in the UK is presented below.

Legislative background

The EU Directive on High-activity Sealed Radioactive Sources and Orphan Sources 2003/122/Euratom (the ‘HASS Directive’) was repealed by BSSD. BSSD includes revised requirements for HASS which are implemented in Great Britain through the Environmental Permitting (England and Wales) Regulations 2016 (EPR2016) (as amended in 2018) and the Environmental Authorisations (Scotland) Regulations 2018 (EASR 2018).

It should be noted that the regulatory requirements for HASS are the same throughout the UK. It is also important to note that there is other legislation relevant to HASS which must also be complied with, for example the Ionising Radiations Regulations 2017.

What are HASS?

A sealed source is a radioactive source in which the radioactive material is permanently sealed in a capsule or incorporated in a solid form with the objective of preventing, under normal conditions of use, any dispersion of radioactive substances. A sealed source is classified as HASS if the activity exceeds the activity values given in Annex III of BSSD (please note some of these activity values differ from the previous values given in the HASS Directive). For radionuclides not listed in the table in Annex III, the relevant activity level is identical to the D-value defined in the IAEA publication Dangerous quantities of radioactive material (D-values) (EPR-D-VALUES 2006).   A source ceases to be HASS once its activity has fallen below the relevant HASS activity value (please note this is a change introduced by BSSD; previously a source had to decay below a lower exemption level for it to no longer be considered HASS).

HASS may contain more than one radionuclide. BSSD and the UK legislation do not make specific recommendations on when mixed radionuclide sources should be classified as HASS. However, agreement has been reached between UK enforcing authorities that mixed radionuclide sources will be classified as HASS when the activity levels (A1, A2, A3) of the radionuclides present and the HASS thresholds (L1, L2, L3) of the individual radionuclides present satisfy the following relationship:

A1/L1 + A2/L2 + A3/L3  > 1

This relationship allows for the situation where a mixed radionuclide source contains several radionuclides, the activities of which all fall below the individual HASS thresholds, but the total source represents an equivalent or greater level of hazard to that of a single radionuclide HASS.

Regulatory responsibilities in the UK

The legislation described requires, amongst other things, that Competent Authorities in all EU Member States keep records of HASS holders and the sources they hold.

In the UK, the authority responsible for enforcing HASS depends on the region (England, Wales, Scotland or Northern Ireland), owner and location of the HASS.

For HASS that are not located on nuclear licensed sites, mobile HASS located on nuclear licensed sites, and HASS owned by tenants on nuclear licensed sites, the enforcing authorities are the Environment Agency (EA) in England, Natural Resources Wales (NRW) in Wales and the Scottish Environment Protection Agency (SEPA) in Scotland.

The environment agencies receive HASS records through their permitting regimes; however some sources kept and used by nuclear licensees are subject to exemptions from the permitting requirements. In these cases, requirements are set out in a Specification (a regulatory power within the nuclear site licence conditions) which has been issued to licensees under nuclear site Licence Condition 25(4). This Specification requires licensees to provide information to ONR on the exempt HASS they hold.

Providing HASS records to ONR

Records of HASS covered by a Licence Condition 25(4) Specification must be provided to ONR whenever such HASS is brought on to the site or consigned from the site, for example if the licensee transfers it to another user, transfers it back to the manufacturer/supplier, or transfers it for disposal or long-term storage (see section below). HASS records must also be provided to ONR when a source decays below the relevant HASS activity value. These records must be provided within 40 calendar days of the change.

Licensees are also required to provide records of all HASS on site covered by a Licence Condition 25(4) Specification to ONR at periodic intervals. Such records must be submitted every 5 years, beginning in January 2024.

The standard HASS record form should be used when submitting HASS records to ONR. A link to the standard EA form is included below.

Long term storage of disused HASS

BSSD requires that adequate arrangements are made for the safe management and control of sources, including when they become disused sources. Such arrangements may provide for transfer of disused sources to the supplier or placement in a disposal or storage facility. Suitable facilities in the UK have been identified for the long-term storage of disused HASS.


Any submissions or requests for information on HASS should be sent to:

Division Delivery Support
Office for Nuclear Regulation
3rd Floor - St James House
St James Square
GL50 3PR