Impact and surveillance
Radiological impact of Cigeo
During the facility's operating phase
Since the packages of waste received at Cigeo will contain no liquids and only small amounts of gaseous radionuclides, discharges from the facility during its operating phase will be very limited. Almost all of discharges from Cigeo will come from radioactive gases (carbon 14, tritium, krypton 85, etc.) released from certain packages of ILW-LL. These gases will be channelled, measured and strictly controlled before being dispersed and diluted in the air. These discharges and their limits will be subject to authorisation by the French Nuclear Safety Authority (ASN) and will be strictly controlled during the entire operating phase. An initial assessment, based on pessimistic assumptions, indicates that the impact of the discharges will be approximately 0.01 millisievert per year (mSv/year) near the facility, which is well below the regulatory standard (1 mSv/year) and considerably lower than the impact of naturally occurring radioactivity (2.4 mSv/year on average in France). Liquid effluents which is liable to be contaminated with radioactivity will be collected via a specific network. Once collected, these effluents will be analysed to check their level of radioactivity. If contamination is detected, they will be treated and handled in the appropriate manner.
After closure of the repository
The long-term impact of the repository is evaluated both in normal operating conditions and in a degraded situation, in order ensure that its impact will be as low as possible. The studies have shown that the repository will have no impact for 100,000 years, and that in a normal evolution scenario, the impact will be around 0.01 millisievert. In a degraded situation (human intrusion, failure of a repository component, etc.), the studies show that the repository's impact would still be below 0.25 millisievert. This evaluation is based on research done on the phenomena which occur within the repository, whether thermal, chemical, mechanical, hydraulic, radiological or biological.
This research has also been used to identify the main areas of uncertainty and to define different scenarios in order to make pessimistic assessments of the impact of various possible situations. This methodology is implemented within a specific framework, defined by safety baselines established at the international level by the International Atomic Energy Agency (IAEA) and the OECD's Nuclear Energy Agency (NEA), and at the national level by the French Nuclear Safety Authority (ASN). The safety guidelines established by the ASN define the methods to implement to assess the safety of the facility after closure. They provide for an iterative assessment approach to accompany all phases of the repository's development, up to its closure.
Monitoring of the repository and its environment
Andra has planned various inspection, observation and monitoring measures for the repository and its environment, throughout the entire operating phase and after closure.
Predisposal inspection of packages
A series of inspections are and will be carried out on the packages before their placement in the repository, both at the producers' sites prior to delivery and at Cigeo:
- Inspections carried out under the producers' responsibility, within the framework of the waste production process and the request submitted to Andra for disposal of the waste at Cigeo;
- Inspections carried out under Andra's responsibility, to make sure that the packages comply with the producers' declarations and Cigeo's safety specifications;
- Second-level inspections, by sampling, also carried out under Andra's responsibility within the framework of package quality control monitoring.
A monitoring programme will be implemented at Cigeo as from its construction phase and throughout its entire operating phase, in order to keep track of the parameters important to the repository's safety, such as machinery speed, hydrogen concentration, THE filter performance and ventilation air, etc.). In addition to monitoring in the strict sense of the term, parameters affecting the repository's medium- and long-term evolution will also observed: ambient air temperature, changes in diameter of engineered structures (convergence of tunnels), cement integrity, corrosion of steels, etc.
Individual monitoring for reference packages will be done in special rooms in which each reference package can be easily accessed and examined at regular intervals. Reference structures representative of the repository's different components (seals, cells, etc.) and specifically dedicated to observation and monitoring will also be produced during the first phase of Cigeo construction. These structures will be equipped with many instruments to allow detailed monitoring of their behaviour and evolution over time.
Tens of thousands of sensors will be installed in Cigeo
The planned monitoring equipment are based on both existing sensors already in use in the nuclear industry and in civil engineering, for which important experience feedback is available (after decades of use on nuclear reactors, dams, etc.), and innovative equipment being developed through R&D programmes.
In 2007, Andra set up a Perennial Observatory of the Environment (OPE). One aim of the OPE is to establish the initial state of the current environment around the future repository, for a ten-year period, and then to track its evolution during Cigeo's construction and throughout its operating life. It will allow Cigeo's very low impact on the environment to be verified. The territory studied by the OPE covers a surface area of 900 km² around the potential Cigeo site. Within this area, more detailed studies are being conducted on a reference sector of around 240 km².
The system of studies in place is based on several hundred observation points supplemented by data and satellite and aerial photographs, experimentation our land lots and continuous monitoring stations (forest, agricultural, atmospheric and water). Each year, more than 2,000 points are monitored on the fauna and flora, and around a hundred on crops and the physico-chemical and biological soil quality, over a ton of samples are collected and analysed, and more than 85,000 data are recorded using protocols in accordance with current best practices.
To ensure the traceability and preservation of the data collected by the OPE, Andra is building a sample and data banks (écothèque) to be commissioned in 2013. This is where the samples will be preserved, i.e. samples taken from matrices such as local food chain (milk, cheese, corn, vegetables, fruit, etc), forest ecosystems (leaves, mushrooms, wood, game animals, etc.) and aquatic ecosystems (water, fish, etc.). The écothèque will be operated for at least 100 years to ensure monitoring of environmental evolutions throughout Cigeo's operating life. The related scientific tasks are carried out within the framework of national and international partnerships, within a certified observation system.
The local populations have, on several occasions, expressed their hope to see health surveillance around the repository. An expert panel has been established to propose technical methods for ensuring this surveillance. Andra has submitted the matter to its supervisory ministries so that the governance and organisation of such measures can be defined.