Radiation Protection at the GTS

The radionuclides we add can have several fates and the waste treatment we use depends on the physical and chemical properties of the radionuclides used.

Much of the work at the Grimsel Test Site (GTS) has involved short half-life tracers, which decay very quickly to non-radioactive forms. Radioactive tracers with longer half lives are taken to the Paul Scherrer Institute (PSI) for treatment and final disposal.

Removal of cores from the Excavation Project

In specific cases (e.g. Excavation Project), where the radionuclides are held very tightly by the rock, the whole rock mass can be immobilised via injection of an epoxy resin. The area of rock containing the radionuclides is then physically removed by taking large (30 cm diameter) cores of rock (which also contains the radionuclides) from the GTS.

Overview of the overcoring procedure

The extracted cores can then be analysed by very precise radiochemical techniques, which allow the sites of radionuclide retardation to be observed.

Every person working in the radiation controlled zone (whether as level B or C) wears a detector that records any radiation dose that they receive. This badge is called a thermo-luminescence detector (TLD). The area within the laboratory is also monitored using state-of-the-art instruments that measure the radiation levels within the laboratory and also with contamination monitors to ensure no spillages have occurred. Computer systems linked to very precise measuring equipment monitor the radionuclide tracers in the groundwater in real time.

Monitoring equipment at the GTS

We have received clearance from ENSI for the use of transuranics radionuclides in the GTS. This is based on the successful application of "simpler" radionuclide tracers in previous experiments and the GTS is, to date, the only underground rock laboratory in the world where transuranics radionuclides can be added directly to the ground water.

All the work carried out in the controlled zone is strictly regulated now by BAG and permission is needed before any work involving radionuclides commences.
 

At the Grimsel Test Site (GTS), we carry out experiments with radionuclides as tracers of the processes in the rocks. Radionuclide tracers are very useful because we can detect them at much lower concentrations than non-radioactive tracers and because they provide individual "fingerprints" which allow us to follow natural mechanisms in the rock and groundwater unambiguously and this makes our experiments more useful than if we used non-radioactive tracers

In addition, use of radioactive tracers in the GTS allows us to study safety-relevant radionuclides in an environment analogous to that of a real radioactive waste repository.

What is radiation protection?

Radiation protection is ensuring that the use of radionuclide tracers at the GTS does not harm the people who work and visit the GTS and ensures that there is no impact on the environment. Initially very strict regulations were set by HSK (Hauptabteilung für die Sicherheit der Kernanlagen / Swiss Federal Nuclear Safety Inspectorate - now ENSI ) and continues with BAG (Bundesamt für Gesundheit / Swiss Federal Office of Public Health) and all work with radionuclides is supervised by a Radiation Protection Expert (RPE).

We wish to thank ENSI and BAG for their continued support of our work at the GTS.

Safe use of radionuclides at the GTS

In 1988, a special area of the GTS tunnels was designated as a radiation controlled zone and this conforms to regulations laid down by ENSI regarding the safe handling and use of radionuclides. In the unlikely case of an accident, the controlled zone would ensure minimal impact on the GTS and any staff or visitors present.
 

Location of controlled zone on GTS map and picture of gate

In normal experiments, the lab operates as a Level C radiochemistry laboratory. The staff working in the controlled zone are monitored for any contamination and all material is handled according to strict regulations.

In addition, our laboratory can routinely be upgraded to a Level B radiochemistry laboratory. This is used when higher activities of radionuclide tracers are required when alpha-emitting radionuclides are used or the set-up of the experiment poses a greater radiological risk to the workers (e.g. during excavation of rock cores as in the Excavation Project). The requirements of a level B lab are:

• Protective clothing must be worn when working in the controlled zone.
• There is a special changing area at the entrance to the lab.
• All people and equipment coming in and out of the laboratory are monitored.
• The air supply within the laboratory is separate to that for the rest of the GTS, is maintained under atmospheric pressure (to contain any possible contamination) and is filtered with any particles trapped in these filters monitored for radiation.

Tracer injection during the EP Project

For further information please contact Dr. Andrew Martin:
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