Drawing up an inventory of radioactive materials

Radioactive materials are very varied. They differ in terms of their physical and chemical properties, the intensity and nature of the radiation they emit, and the risks they entail. The vast amounts of scrap from uranium mines, which release a small amount of radon, have almost nothing in common with the vitrified residues from La Hague. The management of each category of waste has to suit the characteristics of that waste. For waste to be managed properly, a complete inventory of it has to be drawn up.

For the purposes of management, the inventory is based on two classification criteria:
– The activity level, which determines the protection measures to be taken. The categories are: very low-level waste (VLLW), low-level waste (LLW), intermediate-level waste (ILW), or high-level waste (HLW);
– The length of life of the main radioactive elements present, which determines the duration of the protection to be considered. Radioelements with a half life of less than 31 years are known as short-lived (SL). It’s all relative! Others are known as long-lived (LL).

There is also very short-lived waste (VSLW), a significant share of which comes from the medical applications of radioactivity (diagnostics or treatment). The radioelements in this kind of waste have half lives of less than 100 days. They naturally disappear very rapidly. Managing very short-lived waste consists merely of waiting the necessary length of time.

The waste presenting the lowest risk is very low-level waste (VLLW) or low-level short-lived waste (LLW-SL). Not only are the volumes of this waste by far the largest, but the waste is also industrially managed. At the opposite end of the spectrum there is high-level waste from reactors. Here almost all the radioactivity is concentrated in a small volume. Generally speaking, the greater the volume for a particular waste category, the lower the activity and risks.

Highly radioactive materials from spent fuel from reactors have to be managed as a priority. Naturally the largest producers are companies that generate electricity. While in operation, reactors only release a minute quantity of radioactivity into the environment thanks to the abundance of precautions taken. The same standard must be maintained when the irradiated fuel is unloaded from the reactor core. This is a relatively easy task over several decades, but it is a challenge that has to be met on a scale of centuries.