The disposal of radioactive wastes in seabed sediments has been under study for more than ten years, both in the UK and in the international community As a result of this research three assessments of disposal of vitrified high level waste in deep ocean sediments have recently been completed (Mobbs et al, unpubl, De Marsily et al, unpubl, Kane, 1987) The NRPR (National Radiological Protection Board) has been involved in the assessment of the subseabed disposal option for many years, principally through participation in the NEA Seabed Working Group, and has recently performed the radiological assessment of subseabed disposal of high-level waste for the CEC PAGIS project (Sumerling et al, unpubl) At present there are no plans to dispose of high-level waste in seabed sediments, but in the UK a nember of options for the disposal of low- and intermediate-level wastes (LLW and ILW) are under consideration by the responsible body, UK Nirex Ltd (Nirex, 1987) One of the options under consideration is disposal in the sediments of the continental shelf and the NRPB has performed some preliminary calculations of the associated radiological impact (Smith et al, 1987) This chapter discusses the approaches to radiological assessment of subseabed disposal used by the NRPB and draws on the results of recent assessments to highlight important areas for future research
In the UK, as in most other countries, the radiological protection standards and criteria applied to waste management and disposal are based on the recommendations of the International Commission for Radiological Protection (ICRP) ICRP recommendations of the International Commission for Radiological Protection (ICRP) IRCP recommendations are based on the principle that the risks to people from radiation exposure should be kept to acceptable levels In the context of solid waste disposal, the radiological protection objectives proposed by the ICRP (ICRP, 1985) are
a requirement that the risk to an individual should not at any time exceed 105 per year, with risk being defined as the product of the probability that a dose will be received and the probability that the dose will give rise to deleterious health effects,
a requirement that all exposures shall be kept as low as reasonably achievable, economic and social factors being taken into account (the ALARA principle)
There is a general consensus (NEA, 1984, NRPB, 1983) that a limit on individual risk is an appropriate criterion for solid waste disposal and in the UK this is reflected in a document issued by the Authorising Departments concerning the principles for assessing land disposal facilities (Department of the Environment et al, 1984) In that document it is stated that a risk target of 106 per year is to be applied to each repository. The main implication of using standards based on risk is that radiological assessments should take into account both the probabilities and consequences of releases of radioactive materials into the environment.