Research and analysis

Initial radiological assessment tool 2: summary

Updated 2 November 2022

1. Chief Scientist’s Group report summary

The Initial radiological assessment tool 2 (IRAT2) is a methodology and spreadsheet system used by the Environment Agency to assess radiation doses to people and wildlife resulting from proposed discharges of radioactive waste to the environment. IRAT2 replaces IRAT published in 2006 and is updated and expanded, containing additional radionuclides and exposure pathways, updated data and data to support wildlife assessments.

The IRAT2 update project produced 2 reports and updated spreadsheet tools:

• Initial Radiological Assessment Tool 2 – Part 1 User Guide – provides guidance on conducting initial radiological assessments using the IRAT2 spreadsheets. It presents the dose per unit release data for the standardised discharge situations used in the initial assessments, guidance on how to apply the data, and worked examples.
• Initial Radiological Assessment Tool 2 - Part 2 Methods and Input Data – provides a detailed description of the initial radiological assessment methodology and the relevant input data, intermediate data and data sources.
• The IRAT2 spreadsheet tools are available on request from the Environment Agency.

1.1 Background

When granting a permit for a disposal or discharge of radioactive waste, the Environment Agency is required to ensure that radiation doses to the public do not exceed specified limits and that permitted discharges do not have adverse effects on wildlife.

The Environment Agency, the Food Standards Agency and the Health Protection Agency (now UK Health Security Agency) defined a set of principles providing guidance on how to assess public doses for the purpose of authorising planned discharges of radioactive waste to the environment. These principles recommend a staged approach to the assessment of doses for permitting purposes. The first stage consists of a cautious assessment of the dose to a representative person or wildlife – an Initial Radiological Assessment.

1.2 Approach

The initial radiological assessment methodology and spreadsheet tool (IRAT2) provides a system for an initial assessment of the dose arising from discharges of radioactive waste into the environment. For IRAT2 the sources are gaseous and liquid radioactive discharges. The initial radiological assessment methodology is based on pre-calculated dose per unit release (DPUR) factors, which are combined with proposed discharges to calculate radiological doses to members of the public and dose rates to wildlife.

1.3 Results

The methodology allows assessment of the release of 100+ radionuclides via the following routes:

• to air directly, and following incineration
• to estuary/coastal water
• to river/stream
• to public sewer (and on to a stream, river or estuary)

Doses from these discharge routes can be calculated for eight different public groups and for four age groups. Dose rates for wildlife in terrestrial, coastal or river environments can also be calculated.

1.4 Publishing details

This summary relates to information from project EBPRI 13097, reported in detail in the following outputs:

• Report: EBPRI 13097/R1
• Title: Initial radiological assessment tool 2 – part 1 user guide

• Project manager: Louise Paul, Research Team, Chief Scientist’s Group

• Report: EBPRI 13097/R2
• Title: Initial radiological assessment tool 2 – part 2 methods and input data
• Project manager: Louise Paul, Research Team, Chief Scientist’s Group

This project was commissioned by the Environment Agency’s Chief Scientist’s Group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.

Enquiries: research@environment-agency.gov.uk.

© Environment Agency