Architecture and management of a geological repository - Andra

2 – General DescriptionIt should also be ensured that hydrological and chemical disturbance (desaturation of the geologicalmedium during construction work, introduction of oxygen and various materials), which may becoupled with mechanical disturbances, does not cause prejudicial damage to the geologicalenvironment.Lastly, since some packages contain fissile material, the repository must remain in a sub-criticalconfiguration, taking account of the potential displacement of matter and long-term changes in thematerials.2.2.1.5 Safety functions over timeThe chart below summarises all the safety functions available over time. For each period considered, itdistinguishes between functions that are directly effective in protecting humans and the environment,and latent functions. The latent functions can help to protect humans and the environment in the eventthat an effective function is weakened.1 – Counter water circulation• Limit groundwater flow• Limit velocity of water circulation betweenrepository and aquiferous formationsCommiss-ioning100 yrs 1000 yrs 10,000 yrs 100,000 yrs 10 6 yrs2 – Limit release of toxic elements andimmobilise them within the repository• Protect B waste• Prevent water from reaching C waste• Limit transport of dissolved species invicinity of C waste• Prevent water from reaching spent fuel• Limit transport of dissolved species invicinity of spent fuel• For all waste and fuel, limit dissolution ofradioactive elements, ensure reducingconditions, filter colloids3 – Delay and weaken migration of toxicelements into the environment• Control migration by diffusion-retentiondispersionin host formation• Delay migration within engineeredcomponents• Preserve natural dispersion capacity insurrounding formations4 – Preserve favourable properties of themedium, limit disturbances• Dissipate heat• Limit mechanical deformation in the argillite• Protect repository from chemical disturbancedue to deterioration of certain packages• Stay sub-criticalKeyEffective functionsIncreasing need for functionLatent functionsGradual loss of functionFigure 2.2.1Safety functions over timeDOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM36/495