Office for Nuclear Regulation

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High-activity Sealed Radioactive Sources and Orphan Sources (HASS) on nuclear licensed sites

Update on the HASS legislation

Please note that there are on-going changes to HASS legislation and this webpage will be updated in due course to reflect those changes. Any submissions or questions relating to HASS should still be sent to the contact details at the bottom of this page. An interim update on HASS is included below.

The Environmental Permitting (England and Wales) (Amendment) (No. 2) Regulations 2018 came into force on the 2nd May 2018. Some key changes affecting reporting of HASS to ONR for licensees in England and Wales are:

  • The use of the activity levels in Annex III of BSSD for defining HASS; and
  • A source will now cease to be HASS when its activity has fallen below the relevant HASS activity level.

The Radioactive Substances Act 1993 and the High-activity Sealed Radioactive Sources and Orphan Sources Regulations 2005apply in Scotland. These regulations are repealed in Scotland by The Environmental Authorisations (Scotland) Regulations 2018 which were made on the 28th June and come in to force on the 1st September 2018. The activity levels in table 4 of these regulations should be used  from the 1st September 2018 when identifying HASS sources for reporting to ONR.


High-activity Sealed Radioactive Sources (HASS) are potentially hazardous, and as such they are subject to a rigorous regulatory regime. The EU Control of High-activity Sealed Radioactive Sources and Orphan Sources directive was introduced to provide strict control on the control of HASS, particularly in terms of maintaining accurate and up to date records of the location, composition and activity level of all HASS held in EU Member States. The details 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; EU HASS) came into force in December 2003. It was implemented in the UK through High Activity Sealed Radioactive Sources and Orphan Sources Regulations (HASS) 2005 (Statutory Instrument No. 2686) in October 2005. The HASS regulations modified the Radioactive Substances Act 1993 (RSA1993).

Subsequently, RSA1993 was repealed and superseded by the Environmental Permitting Regulations (EPR) in England and Wales, and HASS was introduced into EPR in 2010 (EPR2010). The RSA and HASS regulations continue to apply in Scotland and Northern Ireland. It should be noted that the regulatory requirements for HASS are the same throughout the UK.

These regulations apply only to HASS on civil sites. Arrangements for defence-related HASS, irrespective of whether they are located on nuclear licensed sites or not, fall outside the scope of the HASS regulations.

What are HASS?

A sealed source is an apparatus or radioactive substance whose structure is such as to prevent any dispersion of radioactive materials into the environment under normal conditions of use. A sealed source is classified as a high-activity sealed source (HASS) if the activity exceeds the values given in Annex I of the EU HASS Directive. In most cases, this means that a source is defined as a HASS if its activity exceeds 1/100 of the A1 value given in the IAEA Transport Regulations, TS-R-1, IAEA, Vienna, 2005.  A source only ceases to be a HASS once its activity has fallen below the relevant exemption level given in the EU Basic Safety Standards Directive,  96/29/EURATOM.

HASS may contain more than one radioactive substance / isotope. The EU HASS Directive and the UK implementations of this directive do not make specific recommendations on when mixed isotope sources should be classified as HASS. However, agreement has been reached between ONR, EA and SEPA that mixed isotope 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 isotope 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 isotope HASS.

Regulatory responsibilities in the UK

The legislation described requires, amongst other things, that Competent Authorities in all EU Member States to keep formal records of the location, composition and activity of all HASS sources held in their states. The UK government has created a national database to record this information in order to comply with this requirement.

Which UK authority is responsible for enforcing HASS depends on the country and 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 and Wales (with National Resources Wales taking over for Wales in 2015) and the Scottish Environmental Protection Agency (SEPA) in Scotland.

EPR2010 does not provide any regulatory powers regarding the registration of non-mobile (fixed) HASS sources located on nuclear licensed sites.  To address this, ONR issued a Specification under Nuclear Site Licence Condition 25(4), to require licensees to provide the information to ONR on the HASS they hold, as required by the HASS legislation.

It is important to note that there are other strict requirements on the use, transport and storage of HASS. For instance, the HASS Regulations, as described above, do not change a users requirement to comply with the Ionising Radiations Regulations 1999.

Responsibilities of users of HASS

The HASS legislation requires that holders of HASS keep formal records of all HASS held in their possession and to register these sources with the appropriate enforcing authority. Additionally, HASS users are required to notify the relevant enforcing authority whenever they come into possession of HASS, transfer it to another user, transfer it back to the manufacturer, or transfer it a Recognised Installation for long-term storage (see below). They are also required to provide such records to the relevant enforcing authority at periodic intervals of not greater than 12 months.

Users of HASS must provide information and training to their staff in order to inform them of the precautionary measures required when dealing with HASS, including provision of training and appropriate management procedures for handling the orphan sources (i.e. the unexpected discovery of sources not previously accounted for). They must also carry out periodic leak tests, based on international standards, to confirm that the integrity of the source containment remains sound.

Long term storage of disused HASS

The EU HASS Directive requires Member States to identify Recognised Installations for the long-term storage of disused HASS, i.e. HASS that have reached the end of their useful lives and are no longer intended to be used for the practice for which they were originally registered. The Regulatory Bodies involved in HASS enforcement (ONR, EA and SEPA), have worked together to identify suitable facilities in the UK 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