Appendix CRF - Part 3 - Northamptonshire County Council

Radiological Assessment 0820-2
Version 2
3 Assessment Methodology
This section describes the overall assessment methodology used to calculate potential
doses from disposals of LLW at the ENRMF and to determine radiological capacities.
Section 3.1 summarises the SNIFFER methodology, on which the assessment is
based. Section 3.2 describes the changes made to the SNIFFER methodology to take
account of specific features of the ENRMF and the proposed disposals.
3.1 Summary of SNIFFER methodology
3.1.1 Assessment framework
The SNIFFER methodology was developed so as to provide the regulators, and other
stakeholders, with a consistent approach to assessing the potential for landfill sites to
accept the category of LLW known as Special Precautions Burial (SPB). The overall
assessment approach is illustrated in Figure 3.1 (SNIFFER 2006a).
It was originally envisaged that a screening stage would be useful if large numbers of
sites were examined (SNIFFER 2006a). This might be done by site owners, seeking
to put forward a few sites as potential disposal sites, or by planners, seeking to assess
the overall availability of disposal capacity for LLW. The principal application of the
methodology, however, would be for the assessment of particular sites and this
screening stage would not be required.
An important aim of the SNIFFER methodology was to provide regulators with a
means of assessing radiological capacity for a landfill site and updating this capacity
as more information becomes available and the available capacity is reduced though
disposals. To ensure that the assessment is robust and fit for purpose, the approach
developed by the IAEA and others of defining an assessment context forms an
important part of the SNIFFER methodology. To provide as much consistency and
flexibility as possible, the elements comprising the assessment context were
incorporated as generic elements (providing consistency) or site-specific elements
(providing flexibility) as considered most appropriate.
Using the assessment terminology established by the IAEA, the generic aspects of the
assessment context are the assessment purpose, endpoints, basis, and assumptions
regarding future society. The site-specific aspects of the assessment context are the
environmental system of interest, site context, nature of the wastes, and assessment
timescales.
The assessment endpoint and basis are established as generic factors so as to ensure as
much consistency as possible between sites. The assessment end-point is dose, so that
the results can be compared with an effective dose criterion. The SNIFFER
methodology was based on a criterion of 20 Sv/year, representing the point at which
doses arising from disposals can be regarded as being below regulatory concern
(SNIFFER 2006a).
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