Options for Disposal of Active Material Dr. Brian Heaton Aberdeen Radiation Protection Services Ltd.

Waste Streams Exempt waste (Very Low Level Waste) Medium Activity Waste (Low level Waste) High Activity Waste (Medium Level Waste)

Ground Rules Dilute and disperse is not an option for radioactive waste. Shallow Burial is not considered an option for long lived radioactive waste.

Exempt Waste Waste at less than 1 Bq/g isotopic activity. Care must be taken to ensure no reprocessing takes place that would raise level to above this. Could the normal operation of a sludge farm be considered to be “deliberately diluting” the waste.

Problem Wastes High Activity wastes which must clearly be subject to controlled disposal. The large volumes of medium activity silts and sludges from vessels, sand contaminated by leaking produced water and perhaps the residues in some ponds/pits that are not exempt.

International Standards 1 During the operation of a practice (an operation which raises the exposure radiation dose of a worker or a member of the public above background levels) the dose to a member of the public is subject to a constraint of 0.3mSv/y.

Methods of Achieving Shielding Limitations on Access(Distance) Time –Ensuring this happens is generally not a problem

International Standards 2 Until the present a potentially uncontrolled disposal had to ensure that the dose to a member of the public did not exceed 10µSv/y. This figure has been used for many years. There is a move to change this in the future to 0.3 mSv/y.

High Level Waste Really only one option - deep burial through an injection well. Could be very expensive in terms of cost of injection well and injection facilities if new well required. In practice there could be a very small amount required to be reinjected per year.

Medium Level waste Could some of this be land farmed? Risk assessment would have a constraint of 0.3mS/y.

Exposure Scenarios Areas where the land farms are located are remote and when oil production ceases the water supply currently available will generally disappear. What is the possibility of people going to live in the area of a disposal site for a period of time and if so for how long?

Questions arising from this What exposure scenarios should be used when calculating possible doses? What constitutes long term and surveillance?

Radiation Hazards In the long term (>100 years) the hazard is really only due to the radium 226 and its progeny. Main component of dose received is the external dose from the ground.

Would these areas be attractive? Relatively soft flat area for living on. Potentially grassy in times of rain (but very soft and muddy). Access tracks/roads perhaps centre of network or suitable transit point.

Shallow Burial Can it be used in areas of concern. –Excavating trenches which are properly capped to a very high standard. –Placing large boulders on top using heavy lifting machinery. –Destroy access roads.

National Problem Should national governments take responsibility or is the operators responsibility?