The CSM is a pioneering facility: it was the first radioactive waste repository ever operated and closed in France. Its design features were used to help define the major principles applicable to radioactive waste disposal facilities, and even now it remains a worldwide reference in the matter.
Waste at the CSM
The Manche disposal facility during its operating phase
The CSM has stayed in operation for 25 years; it received a total 527,225 m3 of low- and intermediate-level waste, mainly containing short-lived radionuclides.
Most of the waste emplaced at the CSM comes from nuclear facilities operated by EDF, Orano and the CEA. This waste was produced as a result of operating and maintaining nuclear power plants, research laboratories and from dismantling nuclear facilities. It includes, for example, work clothes worn by employees, filters used in ducts at nuclear facilities, concrete and metal waste.
The 25 years of the facility's operation were marked by major changes in disposal design.
Following the commissioning, the waste packages were emplaced directly in excavated trenches. This practice was then abandoned. However one trench containing waste packages was left as it is .
The following disposal design methods were then adopted: where a waste package afforded an adequate level of safety, it would be placed on a slab called a "disposal Platform": concrete packages were first placed along the edge of the structure to create the shape of a gently-sloping mound, like a pyramid, and then the place in the middle was filled with other packages and gravel to immobilise them. The end disposal structure was therefore in the form of a "tumulus".
Waste packages that required additional protection, depending on their activity levels, were placed in reinforced disposal structures called "concrete-lined trenches" or "monoliths". Waste packages were placed Inside in successive layers. Concrete was poured between each layer to envelop and stabilise the packages.
The final cap covering the top of the disposal vaults was installed between 1991 and 1997.
It is designed to protect the packages and minimise water infiltration. It functions just like an umbrella, preventing water from penetrating through into the disposal structures and causing it to run off so that it can be collected, checked before being discharged back into the environment. The cap also protects the waste disposal facility from human, animal or plant (tree root) intrusion.
The cap construction operation was a world's first. It is made up of alternating drainage/impermeable layers, including a bituminous membrane chosen for its elasticity and its ability to adapt to ground movements. The material is soaked in bitumen to make it watertight.
The cap also has a multi-layer drainage system to collect rainwater that would otherwise permeate down through the cap.
The water management system
Water is collected at the CSM thanks to a series of networks (drifts, pipework and drains) that are easy to monitor and are classified into four categories:
- A surface network collects runoff water from the cap and access roads.
- A drainage network, at the level of the membrane, collects any water that has infiltrated down through the cap.
- An underground drainage known as the "underground gravity-assisted separation network" lies beneath the disposal structures. It collects infiltration water that seeps through the structures and thus may have been in contact with the waste packages
- A deep drainage network lies beneath the base of the buried disposal vaults, supporting walls and drifts.
Monitoring the environment
The results of monitoring carried out at and around the CSM demonstrate that the facility does not pose any danger to the population or to the environment: its impact is negligible - at least a thousand times less than the impact of natural radioactivity.
Measurements taken and results
Around 2,000 samples are taken every year by Andra at the CSM and the surrounding area - over 10,000 tests are then performed on those samples in laboratories approved by the French Nuclear Safety Authority (ASN), including the laboratory at Andra's Aube disposal facility (CSA). Sampling frequency can vary: it may be daily, monthly or quarterly.
The measurements performed entail testing for the presence of radioactivity and chemicals to check the impact of the disposal facility on the natural environment.
The results of these measurements are sent to the French Nuclear Safety Authority (ASN), presented at meetings of the Local Information Commission (CLI) and made public in the annual information reports published by the CSM and on the website of the French National Environmental Radioactivity Measurement Network (RNM) run by the ASN and IRSN.
Studies on the potential evolution of conditions at the facility
The CSM was closed in 1994, and the challenge now is to determine its final form, and especially concerning the final cover.
The CSM is the first radioactive waste disposal facility in the world to enter the post-closure monitoring stage. The facility no longer receives waste packages, but various improvements and adaptations are still being regularly made with a view to the facility's final closure within the next fifty years.
All information (monitoring data, adaptations, ...) are currently being scrutinised and examined as a part of the ten-yearly safety review and the report on "dismantling, closure and monitoring", which Andra has to submit in 2019.
Constructing memory of the site
The CSM is the first radioactive waste disposal facility in the world to enter the post-closure monitoring stage, making it a forerunner, one that is now developing tools to ensure that the memory of this site is preserved and passed down to future generations.
- Detailed records to preserve memory
- The Report on Memory Preservation
- The working group on Memory
- Ongoing work on the memory-keeping system
Sustainable management of radioactive waste implies ensuring that the most vital information regarding the disposal of this type of waste is preserved and passed over to the future generations.
The following objectives are pursued: to preserve the memory of the site for as long as possible, in a format that can be easily accessed, understood and used by everyone. This entails many challenges: a suitable site and the most appropriate conservation conditions need to be identified, the language and symbolism used must be appropriate for the purpose, and long-term markers must be developed.
To this end, Andra has developed a comprehensive system based partly on technical and regulatory information and partly on involving local residents in ensuring that this memory is passed on through the generations.
Detailed records to preserve memory
The detailed records (or 'memory') contain more than 11,000 documents (approximately 500,000 pages, taking up a space measuring just over 60 linear metres). They cover all phases in the life of the facility.
The hardcopy originals of the documents selected have all been reproduced in two copies on permanent paper, using equipment and products approved by France's National Archives. One of these two copies of each of the detailed records was sent to the National Archives in 2004, together with a first batch of additional documents on the first five years of monitoring which was added in 2005. The second, identical, copy is kept at the disposal facility site.
Example of an archive box and documents printed on permanent paper
The Report on Memory Preservation
The Report on Memory Preservation (Dossier synthétique de Mémoire) is a regulatory document that Andra wants to make as widely accessible as possible. It must be submitted to the French Nuclear Safety Authority (ASN) as part of the safety review of the CSM in 2019. This report will then be widely-distributed in the area around the disposal facility and at international level.
The purpose of the report is to summarise the key information about the disposal facility that needs to be passed on to future generations and, above all, to remind them of the very existence of the facility and the risks that may last for a very long time (more than 300 years). The document will also include information on the facility's design, how it operated and on the waste contained there.
The studies that led Andra to propose the structure for this report take into account the recommendations made by the French Nuclear Safety Authority (ASN) and the French Institute for Radiological Protection and Nuclear Safety (IRSN), as well as suggestions made by members of the working group on preserving the memory of the CSM and by the experts called in to assess the detailed records of the site 2012.
The Report on Memory Preservation will come in three formats, each produced using different levels of information, enabling readers of the future to understand the information at different levels, following a "learning curve" starting with very basic information aimed at a mainstream reader (the basic information file), and then going up a level with more detailed information (the Key information file), and ending with technical data presented in the form of reference sheets.
The working group on Memory
The working group on preserving the memory of the CSM was set up in 2012. It has fifteen members, including industry representatives, local councillors and politicians, and former employees and local residents. The members discuss how best to pass down the memory of the facility to future generations.
They study issues such as:
- work on captioning images in the image archives, which started in 2014. This entails identifying and captioning images and photos of the site produced during the operating phase. This labour-intensive task, involving over 10,000 digital images, is carried out by a former employee, who worked at the Manche disposal facility from 1969 to 1994.
- the advantages of setting up "markers" to preserve the memory of the site. The working group studies the most permanent media and initiatives that could be used to remind people of the existence of the site. Possible options include setting up a marker stone or organising an annual festival associated with a discovery trail to learn about the heritage of La Hague, based around the CSM, designed as an entertaining way to attract visitors to learn about the issue of memory as well as to enjoy the attractive heritage sites of La Hague.