Andra's approach to safety is based on the implementation of the functions defined in the Safety authority guidelines and requirements, and address the following issues:
- Control of nuclear chain reactions;
- The containment of harmful substances (radioactive in particular);
- The protection of man and the environment against radiation.
The function of the control of the thermal power is not retained in the demonstration of CSA nuclear safety, taking into account the relatively low activity levels of the waste received and disposed of.
The required level of safety is achieved by the combined properties of three major constituents in the disposal system :
- The waste package;
- The disposal facilities;
- The geological environment of the site, in particular the Aptian sand layer.
Waste packages and disposal vaults will ensure the safety of the disposal facility during the operational phase and the monitoring phase.
Beyond the monitoring phase, with the arrangements made during the operational phase (eg limitation of the quantity of harmful substances in the waste) it is retained, in a conservative way, that only the geological medium will contribute to the safety of the facility.
During the operational phase, the following elements are considered important for safety:
- Vaults' containment enclosures
- Nuclear ventilation
- Radiological protection means
- Environmental protection measures
The organization of the activities of the CSA has been defined in coherence with this approach and the different services are in charge of monitoring the elements and the activities considered important for safety.
These are the services in charge of:
- Acceptance of waste packages (approval and acceptance process) and updating as much as needed, the reference specification system (package acceptance specification);
- Operations (disposal, processing, ...) and maintenance;
- The construction of vaults, research, projects and implementation (material modifications, ...);
- The computerized controls of the waste packages and the archiving of the disposed inventories;
- Safety and risk prevention;
- Environment, quality and documentation (archiving, memory, ...);
- The analysis laboratory.
Impact on the environment
As part of the 2016 safety reassessment, the CSA questioned the impact of the facility in a normal situation with regard to the radiological and physico-chemical impact of liquid and gaseous releases on the environment.
This impact is particularly limited, radiologically, at less than one millionth of a mSv/year.
The search for dangerous chemical or toxic substances in effluents from the CSA did not identify anything significant (out of the 131 molecules, some non-zero concentrations were observed, however at low concentrations).
The monitoring of the different waters (runoff, wastewater, storm basin) did not reveal any pollution related to repository activities.
The ambient level of radiation of the CSA is subject to the Andra's objective of a maximum value of 0,25 mSv / year induced by our activities. Measurements showed that it does not exceed 0.03 mSv for a person (stroller type) staying daily for three hours at the limit of the fence of the facility.
Finally, the CSA brings no other nuisance on the environment close to the site (impact from noise, vibrations or light induced by our activities).
Andra has defined and applies a set of rules, procedures and means of prevention and monitoring to prevent or reduce the harmful effects of ionizing radiation on people and the environment directly or indirectly.
Radiation protection is based on three fundamental principles :
The use of ionizing radiation is justified when the benefit it can bring is greater than the disadvantages of such use.
Individual exposures should not exceed regulatory dose limits (see diagram below).
Individual and collective exposures must be maintained at a level as low as reasonably achievable and below the regulatory dose limits, and this account given the state of the art techniques and societal factors. This is the ALARA principle (As low as achievable / as low as reasonably possible.)
The evaluation of the doses received by employees (external exposure) is carried out in accordance with regulation by two types of personal dosimetry:
Every worker having to work in supervised area is equipped with a passive dosimeter. Passive dosimeters are regularly sent to the laboratory for analysis.
Every worker having to work in a controlled zone is also equipped, in addition to passive dosimetry, with an electronic dosimeter. Electronic dosimeters allow measure in real time of the received exposure.
In 2016, the most exposed agent at the CSA received a dose of 1.43 mSv (millisievert) over the year. This value is slightly down from 2015 (1.64 mSv). The worker was assigned to handling duties, crane operations and control activity. This dose is approximately 7.2% of the maximum authorized dose for one year for this category of staff (category A), which is 20 mSv.