Quintessa have been closely involved in a revision of the Environment Agency’s initial radiological assessment methodology (‘IRAT’), which was first published in 2006. The latest version uses updated models and data, includes additional radionuclides and exposure groups, and incorporates an assessment of dose rates to wildlife. The updated version is referred to as the Initial Radiological Assessment Tool 2 or ‘IRAT2’.
The Environmental Permitting (England and Wales) Regulations 2016 (EPR 2016) provide the framework for controlling the generation and disposal of solid, liquid and gaseous radioactive waste so as to protect the public and the environment. When deciding whether to grant a permit for a disposal or discharge of radioactive waste, the Environment Agency requires that radiation doses to the public do not exceed specified dose constraints and there are no adverse effects on wildlife.
The Environment Agency uses a staged assessment process (see Figure 1) as an input to its determination of a permit application. IRAT2 is used in the first two assessment steps. It provides a simple and cautious prospective assessment of the dose that may arise from the proposed discharges.
Figure 1: Stages of Environment Agency dose assessment process used when permitting discharges of radioactive waste (reproduced from the "Initial Radiological Assessment Tool 2 - Part 1 User Guide"). You may also view this image in full resolution.
The tool assesses doses from the release of radionuclides via the following routes:
- to air
- to estuary/coastal water
- to rivers/streams
- to public sewers
Doses can be calculated for up to eight different groups of the public and four age groups. Dose rates can also be calculated for wildlife inhabiting terrestrial, coastal or river environments. The model contains data for around 100 radionuclides, including those that may be used in medical and industrial applications.
IRAT2 is documented in two reports:
- Initial Radiological Assessment Tool 2 – Part 1 User Guide
- Initial Radiological Assessment Tool 2 - Part 2 Methods and Input Data
IRAT2 is also implemented in spreadsheet tools (for example, see Figure 2) which are available on request from the Environment Agency.
Figure 2: IRAT2 release to estuary/coast stage 2 assessment with assessment details tab completed for Example 3 selecting a user defined average coastal exchange rate (reproduced from the "Initial Radiological Assessment Tool 2 - Part 1 User Guide").