Appendix CRF - Part 3 - Northamptonshire County Council

Radiological Assessment 0820-2
Version 2
Executive Summary
The nuclear decommissioning industry has significant future arisings of
decommissioning wastes that fall into the category of low level waste. In the recently
published “Policy for the Long Term Management of Solid Low Level Radioactive
Waste” (Defra 2007), the government has confirmed the acceptability of the disposal
of LLW to landfill including a new subset of LLW classified as high-volume very low
level waste.
Augean plc operates a hazardous waste disposal facility at the East Northants
Resource Management Facility (ENRMF) in Northamptonshire and proposes that the
site is used for the disposal of LLW with a specific activity up to 200 Bq / g. This
report presents a radiological assessment for this site in order to assess the potential
consequences of disposal and determine the radiological capacity of the site for
different waste streams. In this report an example waste stream of LLW from
UKAEA Harwell has been used for illustration.
This report investigates the suitability of the landfill as a disposal route for LLW with
a specific activity up to 200 Bq / g, based on the established approaches used
previously for assessing “Special Precautions Burial” (SPB) which has been used for
wastes of comparable activity. The methodology has been modified to take account
of the likely waste volumes and also for certain site-specific aspects that differ from
the generic assumptions used in the available model.
The assessment model is a simplified and conservative model of the events and
processes that will or might take place during and after operations. A number of
simplifying assumptions are therefore required in order to represent the site and its
surroundings. These assumptions are outlined in the report and the equations and
parameter values used in the model are reported. Where there are significant
uncertainties regarding aspects of the site, a range of assumptions have been used to
test the sensitivity of the model.
The report presents specific dose calculations. These are the doses that would be
received from a disposal of 1MBq of each radionuclide of interest. The specific dose
depends on the pathway by which radionuclides are released and the time of the
release. Specific doses have been calculated for the groundwater release, intrusion,
irradiation and gas release pathways and for pathways relating to leachate
management.
Specific doses are used to calculate the capacity of the site for individual
radionuclides, based on a public dose criterion of 20 Sv / year for normal release
scenarios and a 3 mSv / year dose criterion for pathways resulting from human
intrusion. An illustrative overall site radiological capacity has also been calculated
using preliminary data for the UKAEA Harwell Meashill Trenches waste stream.
In addition to specific dose calculations for the potential exposure of humans to
releases from the site, assessments of dose rates have been made for wildlife in the
vicinity of the site. All of the dose rates calculated, for both terrestrial and the
Galson Sciences Limited i 14 July 2009
WS010001/ENRMF/CONSAPPCRF 547