MANAGEMENT OF VERY LOW‐LEVEL WASTE (VLLW)

This past decade, the possibility of disposing of low-level radioactive materials as conventional waste has been integrated into the national regulations of several countries. This is in line with the new IAEA and EU basic safety standards published in 1996. These modifications of national regulations aim to harmonize waste disposal practices among different countries and, most importantly, they fall within the context of the current increase in VLLW volumes to be handled, particularly due to the development of nuclear facility dismantling activities. At the same time, the increase in price of raw materials and the consideration of sustainable development issues motivate national authorities to develop new waste management solutions geared toward reuse. Countries having chosen to include in their regulations the possibility of disposing of slightly contaminated materials as conventional waste systematically base this policy on the dose rate values recommended by the IAEA and EU:

• Maximum individual dose: 10 µSv/year.
• Maximum collective dose: 1 person-Sv/year.

In most cases, regulations also propose disposal thresholds based on specific or surface activity. These threshold values are often taken directly from international recommendations (IAEA Safety Guide RS-G-1.7 in particular), but they are also sometimes derived from dose values associated with specific scenarios defined by national authorities.

For example, Swedish regulations on the disposal of waste generated by nuclear facilities date from 1996. These regulations stipulate the possibility of releasing low-level radioactive for disposal as conventional waste if the activity level does not exceed 5 Bq/g for / emitters and 0.5 Bq/g for emitters. In addition, the total activity of the VLLW released from the same site for disposal as conventional waste must not exceed 1 GBq/year (limit determined based on the estimated quantity of waste generated by nuclear facilities). In 2006, the Swedish radiological protection authority proposed a revision of these regulations, considering that the previous version was not well suited for the large quantities of radioactive materials resulting from nuclear facility dismantling operations.

In Canada, the concept of disposing of radionuclide-containing materials as conventional waste was not defined in a regulatory framework until 2008. The new regulations effective since April 2008 authorize an operator to abandon or evacuate radioactive materials, without requiring a permit to do so, provided the following requirements are met:

• The effective dose received by an individual as a result of the abandonment or evacuation must not exceed 10 µSv per year.
• The specific activity of the radionuclide considered must not exceed the threshold value defined in the appendix of these regulations (Table 15, which provides a list of threshold values taken directly from IAEA Safety Guide RS-G-1.7) or, in cases where the radionuclide is not listed in the appendix, the specific activity must not exceed the following limits:

• • 1 Bq/g for radionuclides with atomic number lower than 81,
  • 1 Bq/g for radionuclides with atomic number greater than 81, but not emitting radiation (including progeny),
  • 0,1 Bq/g for other radionuclides.

Table 1. Examples of disposal thresholds proposed in the new Canadian regulation

Disposal thresholds may differ from one country to another, but the orders of magnitude for a given radionuclide are generally the same. It should also be noted that national regulations almost systematically give operators the freedom to propose their own disposal thresholds (after approval by national authorities) based on specific scenarios corresponding to the conditions considered. France has chosen not to adopt unconditional disposal options. French regulations stipulate no specific dose limits or threshold values for disposing of very low-level radioactive materials as conventional waste, even though it is theoretically possible on a case by case basis. In practice, the associated procedure is long and complex (see further below). Disposal within the nuclear fuel cycle after treatment in a conventional facility could be considered in particular. Three conventional facilities are currently authorized to treat very low-level radioactive materials. This includes the Huart foundry (Bouches du Rhône area), which is currently used to recycle lead scrap from AREVA NC, EDF and CEA facilities (after decontamination in the Marcoule site). This lead is then reused as biological shielding in these same facilities.