Radiation protection in the Asse mine

Date

24/02/2009

To exclude a hazard to the staff, the Federal Office for Radiation Protection (BfS) has taken numerous safety precautions. Radiation protection areas, dosimetrical monitoring, and contamination controls are to protect the staff.

Radioactive Control Areas are designated.

A radiological characterisation of the mine will lay the foundation for additional safety assessments. The current status of radiation protection and the radiological characterisation of the Asse mine has been summarised in the following.

BfS conclusion from the knowledge that contaminated brines in Asse were relocated from the swamp in front of chamber 12 to areas on the 700-m level: Although it has not yet been possible so far to clarify the fate of contaminated brines (for example brines of the swamp in front of chamber 12), the information available to BfS does not indicate greater contamination in the areas that are accessible to the operating staff.

Already in the past year, BfS ordered a radiological characterisation of the Asse II mine which will be the basis for radiological safety assessments of the facility. The objective of the radiological safety assessments is to prove that the protection goals stipulated in the Atomic Energy Act and the Radiation Protection Ordinance are guaranteed.

The radiation protection measures already taken today comprise the following:

• Classification of the persons mainly working underground and working in radiation protection areas into radiation-exposed persons of category B
• Dosimetric monitoring of the occupied persons when they stay in radiation protection areas
• Incorporation monitoring
• Contamination controls in persons and objects after they have been employed in radiation protection areas
• Regular surface contamination measurements on the 750-m level also outside radiation protection areas (So far no impermissible contamination has been detected in these measurements)
• Monitoring of saline solutions also outside radiation protection areas (This does not indicate activities leading to relevant contaminations, either)
• Extensive analyses carried out by the Brenk company with respect to the contamination of operational waste outside the radiation protection areas (These analyses did not indicate impermissible surface contamination in the mine, either)
• Monitoring of air activity (does not provide indications of impermissible surface contamination)
• Monitoring of emissions
• Monitoring of immissions

Contamination control at the shaft exit

According to the experience of BfS, a radiological risk for the staff in the Asse mine can be excluded with a consequent implementation of the mentioned radiation protection measures.

However, the occupational safety measures have only been documented incompletely.
On account of this residual uncertainty, BfS initiated further safety precautions for radiation protection monitoring of the staff:

• Classification of the persons mainly working underground into radiation-exposed persons of category B
• Carrying dosimeters also outside the radiation protection areas is mandatory.
• When leaving the mine, all persons must be controlled for contamination.

The characterisation of the Asse mine that was already initiated in the past year will be continued and the resulting findings will be taken into account in the planning of the radiation protection monitoring of the staff.