This injection used a radionuclide cocktail of ⁶⁰Co, ¹³¹I, ¹³⁴Cs and ¹⁵²Eu. (¹³¹I is only in the spike input injection). All injections are licensed by our regulator, HSK, and is monitored by Radiation Protection Officers (See the Radioprotection section ).

• These radionuclides are more strongly sorbing than previous tracers used in HPF
   
• Have longer half-lives than previous tracers
   
• Require more stringent radioprotection measures
   
• Provide information more relevant to a repository safety assessment

The final tracer test is a series of stages of injections, it began with;

• Injection of 0.5 litre of cocktail in the equipment sorption stage
   
• Then rapid injection of 5 litres of cocktail in the spike input stage
   
• Then follows injection of up to 60 litres of cocktail in the top hat input stage.

Radionuclide activities are measured at both the inflow and outflow of the dipole, monitoring of the outflow solutions will continue after the injection is complete. Using experience gained in earlier work at the GTS (see the Radionuclide Migration Programme in the CRR section), the HPF experimental shear zone will be stabilised by injection of epoxy resin followed by overcoring using triple core barrel techniques to excavate the shear zone. This technique should allow the cement altered shear zone to be removed for detailed radiochemical, mineralogical and structural analysis.