Implementation of the HASS regulations for nuclear licensed sites

Introduction

Experience worldwide of handling high activity sealed radioactive sources (HASS) indicates that there is the potential for such sources to be misplaced and their locations either forgotten or not recorded. The EU HASS Directive, and subsequently the UK HASS Regulations, have been introduced in order to provide a rigorous regulatory regime for the control of HASS sources.

Legislative background

The EU Directive on High Activity Sealed Radioactive Sources and Orphan Sources, 2003/122/EURATOM, came into force in December 2003. It was implemented in the UK through the High Activity Sealed Radioactive Sources and Orphan Sources Regulations 2005, Statutory Instrument No. 2686, which came into force in October 2005.

The HASS Regulations do not affect a user’s requirement to comply with the Ionising Radiations Regulations 1999. Compliance must be demonstrated with both sets of Regulations. The HASS Regulations amend the Radioactive Substances Act 1993.

What is a HASS source?

In terms of its containment integrity, a HASS source is defined as a source whose structure is such as to prevent any dispersion of radioactive materials into the environment under normal conditions of use.

For sealed sources comprising a single radionuclide, the activity should be noted at the time of manufacture or, if this is not known, at the time when it first became available on the market. Such a source is classified as a HASS source if its 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 source if its activity exceeds 1/100 of the A1 value given in the IAEA Transport Regulations, TS-R-1, IAEA, Vienna, 2000.  A source only ceases to be a HASS when its activity has fallen below the exemption level given in the EU Basic Safety Standards Directive,  96/29EURATOM.

The EU HASS Directive and the UK HASS Regulations do not make specific recommendations on when mixed isotope sources should be classified as HASS sources. However, agreement has been reached between ONR, EA and SEPA that a mixed isotope source will be classified as a HASS source 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 source.

Regulatory responsibilities

The EU HASS Directive requires, amongst other things, competent authorities in all member states to keep formal records of the location, composition and activity of all HASS sources held in their states. The UK government has decided to comply with this requirement through the creation of a national database of all HASS sources held within the UK.

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

The EA and SEPA already have well developed arrangements for the registration of radioactive sources, made using the powers granted to them by the Radioactive Substances Act 1993. The HASS Regulations extend these powers to include HASS sources.

For non-mobile HASS sources owned by nuclear site licensees and located on nuclear licensed sites, the enforcing authority is the Health and Safety Executive, who have delegated the responsibility to the Nuclear Installations Inspectorate (ONR).

However, neither the Radioactive Substances Act nor the HASS Regulations provide any regulatory powers to ONR regarding the registration of HASS sources located on nuclear licensed sites. Hence, in order to obtain the necessary information to allow the UK national database of HASS sources to be completed, ONR has decided to issue Specifications under Nuclear Site Licence Condition 25(4), which requires licensees to provide operational records.

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

Note that the majority of HASS sources in the UK are not held on nuclear licensed sites but are held in other establishments such as research institutions, where they are used for research purposes, and hospitals, where they are used in diagnostic and therapeutic procedures.

Responsibilities of users of HASS sources

It should be noted that users of HASS sources are required to keep formal records of all HASS sources held in their possession and to register these sources with the appropriate enforcing authority. They are also required to provide such records to the relevant enforcing authority at periodic intervals not greater than 12 months.

A national database has been set up jointly by EA, SEPA and ONR, to record the location, composition and activity of all HASS sources in the UK. Users of HASS sources must notify the relevant enforcing authority whenever they come into possession of a HASS, transfer it to another user, transfer it back to the manufacturer, or transfer it a Recognised Installation for long-term storage (see below).

Users of HASS sources must provide information and training to their staff in order to inform them of the precautionary measures to be taken when dealing with HASS sources. 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 sources, i.e. HASS sources 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 various regulatory bodies, i.e. ONR, EA and SEPA, have worked together to identify suitable facilities in the UK for the long-term storage of disused HASS sources.