Along with nuclear accidents, waste is the most controversial topic in nuclear safety. What to do with radioactive materials?
First of all, we’ll look at what nuclear waste is, and the special case of radioactive discharges (such as tritium, which is regularly discussed). Next, we’ll look at the different types of waste, whose characteristics vary widely: some are barely radioactive at all, while others are highly hazardous and need to be vitrified. Finally, we present the different methods of storing nuclear waste.
I. What is nuclear waste?
Radioactive or nuclear waste “is defined as radioactive substances for which no further use is planned or envisaged.”(source)
It’s not just the nuclear industry that generates nuclear waste. It’s also the case in research, medicine (remember: scanners), defense (we have nuclear submarines) and industry in general (rare-earth mining, sterilization devices, etc.).
Note that in France, only a small proportion of spent fuel is considered waste. In fact, reprocessed uranium is not nuclear waste. We recover it for re-enrichment or storage for future use.
The special case of radioactive releases
Nuclear facilities may release radioactive gases and liquids into the environment. These can be seen as “nuclear waste”, but they are treated differently and do not appear to be harmful.
In general
Nuclear facilities release tritium (more on this later), carbon-14, radioactive iodine, radioactive noble gases and other radionuclides, in gaseous and/or liquid form. Together, these represent some one hundred trillion becquerels per year, the vast majority of which is tritium, which is not very radiotoxic. Although health standards may seem impressive, they are designed to ensure that this does not pose any health or environmental problems. Biomass- and coal-fired power plants release higher quantities of radioactive compounds (to be verified).
To find out more, read Tristan Kamin’s article Impact of radioactive discharges
The case of tritium
Nuclear facilities tend to produce tritium, the hydrogen isotope with 3 neutrons. It is a fission product, found in spent fuel. It is impossible to filter, as it is part of the water itself. The French Orano plant at La Hague often releases it as part of its spent fuel reprocessing process. Irradiated water
Tritium is radioactive, but this radioactivity is not very dangerous. As we have seen, we need to go from absolute radioactivity (in bequerels) to its impact (in Sievens). This involves defining an equivalence. For tritiated water, “in the worst case (i.e. in a one-year-old child) and by ingestion, the dose factor amounts to 64 pSv/Bq.” This is 1,000 times lower than for potassium-40, naturally present in our bodies and, in particular, in bananas (which contain the equivalent of around 20Bq).
In France, the legal discharge limit for the La Hague plant is 18,500 TBq/year, and for a nuclear power plant a few dozen TBq/year. According to Tristan Kamin, an impact study of Orano’s La Hagues plant concludes that, in the worst-case scenario, all marine discharges represent an exposure of 7µSv/year, a tiny amount compared to natural exposure (~4Sv/year). What’s more, tritium would only account for 0.5% of this 7µSv/year … To complete the picture, you can read his article“Tritium stories“.
II. The different categories of radioactive waste in France
Not all radioactive waste presents the same risk. To treat them differently, we have separated them into several groups. They are classified according to their lifespan (how long they will remain radioactive) and their level of radioactivity. In France, they are divided into 5 categories:
- Very low-level waste (VLLW)
- Low- and medium-level short-lived waste (LML-SLW)
- Long-lived low-level waste (LLW-LL)
- Long-lived intermediate-level waste (ILW)
- High-level long-lived waste (HLLLW)
Broadly speaking, there are two types of radioactive waste: materials that have been in contact with high levels of radiation for so long that they themselves have become radioactive, and spent fuel, which falls into the last and most problematic category (HA-VL).
Somewhat apart from this is very short-lived waste, resulting from medical applications, which is simply stored on site until radioactivity declines (<100 days).
Very low-level waste (VLLW)
This type of waste is not specific to nuclear activity, but will develop a slight radioactivity when in contact with it for a long time. This is the case, for example, of certain rubble from the dismantling of nuclear facilities.
Although they represent large volumes (537,000m3, 27% of the total), their radioactivity is minimal(0.0001% of the radioactivity of all waste). Its half-life is very short, around ten years.
Low- and medium-level short-lived waste (LML-SLW)
Some materials and consumables are closer to nuclear activity and therefore retain more radiation. Others come from other activities handling radioactivity, such as hospitals and laboratories.
This represents the bulk of the waste volume (938,000m3, 63%), and still only a small proportion of the radioactivity (0.03%).
Low-level long-lived waste (LLW-LLW)
This category includes waste containing radium. This is particularly the case with radiferous graphite from the dismantling of first-generation power plants (whose technology used graphite as a moderator).
It represents 93,600m3, 7% of the volume and 0.14% of the total radioactivity.
Long-lived intermediate-level waste (ILW)
This is the category for materials closest to fossil fuel. This includes, for example, the cladding surrounding the spent fuel, recovered during reprocessing.
They represent 42,800m3, 3% of the volume and 4.9% of the radioactivity of the whole.
High-level long-lived waste (HLLLW)
This is the “real” nuclear waste, the remains of spent fuel.
It has a lifespan of several thousand years and, although it represents only 3740m3 0.02% of the volume, it accounts for 94.9% of the radioactivity of radioactive waste.
III. Disposal methods for nuclear waste (France)
Each country has its own regulations governing the storage of nuclear waste.
In France, the 1991 Bataille Law initiated major research, leading to the June 28, 2006 program law on the “Management of radioactive materials and waste”.
Short-lived waste is compacted and stored in concrete cells and “stored in concrete cells at the Andra storage center at Soulaines or Morvilliers in the Aube”. They lose half their radioactivity within 31 years, and become virtually inactive after 300 years(EDF)
MA-VL waste is compressed and encapsulated in metal canisters, which in turn are encapsulated in “asphalt packages”. The worst waste is vitrified (= encapsulated in glass) and packaged in small metal flasks. They are currently stored at the La Hague site. Here are some photos of people who have visited the site.
When the deep geological repository is installed, as envisaged by the 2006 law, this waste will be transferred to it.
Deep geological disposal involves
Sweden is also planning to use deep geological disposal.
One company, Deep Isolation, plans to offer relatively inexpensive deep geological storage.
Another visit: https://twitter.com/GoldbergNic/status/1534279829566148609
III Innovations in waste treatment
The waste treatment sector is particularly active in terms of innovation, especially in connection with the dismantling of nuclear power plants. First and foremost, there are two subsidiaries of major energy companies, which combine their activities in these areas:
- Veolia ‘s VeoliaNuclear Solutions, created in 2017
- EDF’sCyclife, created in 2019
There are many specific projects dedicated to better managing radioactive waste:
- Waste2Glass, a project founded by Veolia Nuclear Solutions and Cyclife aimed at developing a less expensive and more practical vitrification process (Geomelt) than the one currently used.
- Fast-neutron reactors, in particular Transmutex, would enable the most problematic elements to be transmuted into lower-activity, shorter-lived elements.
- IRSN,
- https://www.irsn.fr/FR/connaissances/Installations_nucleaires/dechets-radioactifs/gestion-stockage-dechets-radioactifs/Pages/1-dechets-radioactifs-differents-types.aspx#.Y85s562ZOUk
- IRSN video series: https://www.irsn.fr/FR/Actualites_presse/Communiques_et_dossiers_de_presse/Pages/20220324_questions-francais-risques-dechets-nucleaires.aspx#.Y5zjoX2ZOUk
- Tristan Kamin, on geological disposal: https://doseequivalentbanana.home.blog/2021/05/08/dechets-8-on-ne-sait-pas-gerer-les-dechets-nucleaires/
- CEA, The essentials on … Radioactive waste
- Ministry of Ecology, Dismantling and management of radioactive waste, https://www.ecologie.gouv.fr/demantelement-et-gestion-des-dechets-radioactifs
- ASN issues its opinion on the management of high-level waste (HA) and long-lived intermediate-level waste (MA-VL)
- reprocess to reuse’ nuclear waste is the way forward
- Le Réveilleur video series: https://www.youtube.com/watch?v=p0zX8eUW_jQ&list=PLhgpBc0hGjSvCZ4Uo9mE1XTc7aSa4NRLE
- On tritium :
- https://doseequivalentbanana.home.blog/2019/11/24/des-histoires-de-tritium/
- https://doseequivalentbanana.home.blog/2019/11/24/leau-contaminee-au-tritium-de-fukushima/