Operational radiation protection
To rule out a hazard to the staff and the general public, the Federal Office for Radiation Protection (BfS) has taken numerous safety precautions. Both staff and visitors to the mine are protected in the scope of operational radiation protection, e.g. by establishing radiation protection areas, using dose monitoring and contamination controls. The discharge of radioactive substances into the environment is controlled by monitoring the exhaust air.
Radioactive Control Areas are designated.
With the application for a licence to handle radioactive substances according to §7 StrlSchV in 2009, the BfS performed a radiological fact-finding for the Asse II mine and submitted the results as a licensing document representing the basis for the radiological safety analyses for the operation of the Asse II mine.
The objective of the radiological safety assessments is to prove that the protection goals for the protection of staff and environment stipulated in the Atomic Energy Act and the Radiation Protection Ordinance be guaranteed.
Radiation protection measures
The radiation protection measures include:
- All persons working underground on a regular basis are classified as radiation-exposed persons of category B.
- To determine the personal dose, the staff use dosimeters when working underground.
- Occupationally exposed persons are routinely measured on a whole-body-counter and examined for radioactive materials possibly taken up in the body.
- Following deployment in radiation protection areas persons and objects are controlled for contamination.
- All visitors are provided with a directly readable dosimeter so that they can control their radiation dose during the visit. Before they leave the mine, additional contamination controls are carried out. So far no contamination of persons has been detected.
- Surface contamination controls are carried out on a regular basis, also outside the radiation protection areas. So far no impermissible contamination has been detected in these measurements.
- Monitoring of saline solutions – also outside the radiation protection areas – for natural and artificial radionuclides. This does not indicate either that relevant contamination outside the radiation protection areas was caused by the saline solutions.
- Extensive analyses in terms of contamination of operational waste outside the radiation protection areas. They did not indicate impermissible contamination either.
- Monitoring the activity concentration of radioactive materials in the mine air. So far, the monitoring has not provided indications of impermissible surface contamination.
- Monitoring of the discharge of radioactive materials through the exhaust air flow into the environment (emission monitoring).
Fact-finding: Separate protective and monitoring measures
Contamination control at the shaft exit
In the scope of the fact-finding process to open the chambers it is planned to carry out at first preliminary investigations at two emplacement chambers (7/750 and 12/750). For this purpose the areas in front of the chambers are separated hermetically from the residual mine openings by means of locks and filters. Separate protective and monitoring measures are carried out in these special areas (radiation protection area). They include:
- Monitoring of the activity concentration of radioactive materials in the mine air, in particular monitoring of the aerosol-bound activity,
- Protection from the incorporation of radioactive materials with the help of special health and safety measures,
- Monitoring of exhaust air from the work areas before it leaves the mine and reduction of the activity concentration by appropriate measures (such as filter technology),
- Contamination controls of persons and objects following their deployment in the radiation protection areas to avoid inadvertent dispersion of contamination,
- If required use of personal protective clothing (such as force-ventilated suits) when carrying out special works (such as sampling of cuttings).
In the experience of the BfS, a radiological risk for the staff in the Asse mine can be ruled out when the mentioned radiation protection measures are implemented consequently.