Radiation waste management

— Exempt waste (EW). Waste that meets the criteria for clearance, exemption or exclusion from regulatory control for radiation protection purposes.

— Very short lived waste (VSLW). Waste that can be stored for decay over a limited period of up to a few years and subsequently cleared according to arrangements approved by the regulatory authority, for uncontrolled disposal, use or discharge. This would include radioactive waste containing primarily radionuclides with short half-lives often used for research and medical purposes.

— Very low level waste (VLLW). Waste which does not meet the criteria as EW, but which does not need a high level of containment and isolation and therefore is suitable for disposal in near surface landfill type facilities, with limited regulatory control. Such landfill type facilities may also contain other hazardous waste. Typical waste in this class would include soil and rubble with low activity concentration.

— Low level waste (LLW). Waste that contains material with radionuclide content above clearance levels, but with limited amounts of long lived radioactivity. It requires robust isolation and containment for periods of up to a few hundred years and is suitable for disposal in engineered near surface facilities. It covers a very broad range of materials that includes short lived radionuclides at high activity levels, but long lived radionuclides only at relatively low activity levels.

— Intermediate level waste (ILW). Waste which, because of its content, particularly of long lived radionuclides, requires a higher level of containment and isolation than is provided by near surface disposal.

However, it needs no or only limited provision for heat dissipation during its storage and disposal. It may include long lived radionuclides, in particular alpha emitting radionuclides, that will not decay to an activity level acceptable for near surface disposal during the time which

institutional controls can be relied upon and therefore requires disposal at greater depths of the order of tens up to a few hundred metres.

— High level waste (HLW): Waste with radioactivity levels high enough to generate significant quantities of heat by the radioactive decay process or with large amounts of long lived activity which need to be considered in the design of a disposal facility for such waste. Disposal in deep (usually several hundred metres or more below the surface), stable geological formations is the generally recognized option for its long term management.

Most of the waste generated at an accelerator facility will fall into the categories of short lived, low level or intermediate level waste. The main sources of these wastes will be spent targets, chemicals used in the processing of targets and separation of radioisotopes from the target materials. Usually, this material can be collected on-site at a specific facility or in a designated area.

The radioactive waste should then be transferred to an authorized or licensed handler for removal from the site.

9.6.1. Decay in storage

One aspect of the short-lived radioactive isotopes is ‘decay in storage’

where the materials are allowed to decay to a low level in a shielded area before they are removed for disposal. During this time the amount of radioactive material may significantly decrease depending on the half-lives of the radioisotopes present, and in some cases the material may be discarded as regular waste if certain conditions are met. Normally, a facility may hold by-product material with a physical half-life of less than 120 days for decay in storage before disposal without regard to its radioactivity if the facility:

— Monitors by-product material at the surface before disposal and determines that its radioactivity cannot be distinguished from the background radiation level with an appropriate radiation detection survey meter set on its most sensitive scale and with no interposed shielding.

— Removes or obliterates all radiation labels, except for radiation labels on materials that are within containers and that will be managed as biomedical waste after they have been released from the licensee.

9.6.2. Protection of the general public

One of the most serious concerns is the protection of the general public from releases of radioactivity. Therefore, concentrations of radioactive material which may be released to the general environment must be below certain levels, defined set by regulatory control of radioactive discharges to the environment. Any radioactivity released in ground water, surface water, air, soil, plants, or animals must not result in an annual dose exceeding an equivalent of 250 mSv to the whole body, 750 mSv to the thyroid, and 250 mSv to any other organ of any member of the public. A reasonable effort should be made to maintain releases of radioactivity in effluents to the general environment.

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