Architecture and management of a geological repository - Andra

4 – Waste disposal PackagesFor both variants, the small diameter disposal package body (bare and individually cladd assembly) iscomposed of a single cylindrical shell made of non-alloy steel (P235) with rated thickness of 120 mmas illustrated in Figure 4.3.6 and Figure 4.3.7, and of a welded built up bottom with rated thickness of150 mm made of the same material. Rated thickness is slightly higher than that of the large diameterpackage as it not only has to ensure leaktightness for 10,000 years (corrosion thickness) but alsoprovide container mechanical resistance (see below). An additional thickness of 20 mm reinforces therated thickness of the bottom to be used as a root face for electron beam welding.Figure 4.3.6 Emplacement for clad assembly Figure 4.3.7 Emplacement for bare assemblyAs for large diameter containers, the assembly emplacement is closed with a plug which is also awelded disk 10 mm thick.• The lidThe lid has a total thickness of about 265 mm to fulfil the same functions as for large diametercontainers as well as mechanical resistance.4.3.3.2 PerformancesThis section reports on studies conducted to justify container design basis as regards objectives ofdurability (leaktightness and mechanical resistance) and safety-criticality.• Steel thickness and lifetimeAs in the case of C waste, thermal phase duration, i.e. the duration required for package temperature togo below about 50 °C, depends on three related parameters: (i) maximum repository temperature 52 ,(ii) fuel age when placed in the repository (iii) and repository zone architecture.With temporary storage prior to disposal for CU1 and CU2 types of fuel of 60 years and 90 yearsrespectively, thermal design basis of disposal presented in section 5.3 results in maximum thermalphase duration of a few thousand years [10]. Package temperature evolutions over time are presentedin Figure 4.3.8.52As a reminder: 100 °C at repository container surface and 90 °C on contact with the engineered barrier based on swelling clay, seechapter 5.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM150/495