Speaker
Description
Ansaldo Nucleare S.p.A. has designed, fabricated and partially qualified a high integrity container (CONTAS), for the conditioning, transportation and long term storage of solid ILW with low content of -emitter radionuclides. Based on national and international norms and standards (IAEA SSR-6, ADR-RID, UNI 11784, Raccolta V.S.R.) CONTAS complies with stringent requirements to ensure protection of persons and environment.
CONTAS is a cylindrical container 1500mm high by øext 1100mm, having a maximum internal usable height of 1165mm by and øint 740mm , offering a general shielding wall thickness of 160mm and an internal usable volume of approximately 0,5m3 .
The main distinguishing features of CONTAS are described as follows:
• base material in forged carbon steel P355 QH1 & QL1
• nominal mass (full load) 10.000 kg , usable volume 500 liters
• 50 straight years lifetime, extendable to 100 years in case of scheduled inspections and/or maintenance activities
• two secondary openings closed by blind flanges: the first one to drain CONTAS after loading underwater and to detect internal pressure during operation, the second one to vent CONTAS during draining
• primary sealing system (between body and lid) made by two axial gaskets in series, co-planar, tightened through bolting; the gaskets are energized metallic C-rings, CONTAS design ensures the sealing performances in every design condition including accidental events
• secondary sealing systems made each by an energized metallic C-ring in series with an NPT plug; the tightening of the flanges is obtained through bolting
• every sealing systems provided with a control volume each, inspectable during CONTAS operation and preserving the overall leak tightness of the package
• geometrical details aimed to prevent stagnation of contaminated water and/or particulate (e.g. conical floor, bolt head open seats, drain holes for bolts)
• lifting devices allowing both lateral and bottom lifting
• bottom end and top lid profiles easing stacking
• suitability to host customized internal baskets and additional shielding panels
Innovative features of CONTAS have been patented (both in Italy and in main EU countries).
CONTAS design, within the scope of a proper defined Qualification General Plan, has been successfully even if partially qualified through a mix of experimental and analytical tests; the experimental ones have been performed both on material samples or even full-scale prototypes, arranging the test sites according to standards criteria, and involving qualified Suppliers and Laboratories.
Experimental tests include:
• free drop on a target rigid platform according to IAEA SSR-6 and SSG-26
• fire accident
• degradation
• dynamic characterization of base material for FEM model validation
• leak tightness
• pressure
• functional (assembly, handling, lifting, stacking, etc.)
Once the FEM model and methodology have been validated by comparing numerical results with experimental outcomes, multiple dynamic simulations have been launched to assess the consequences of as many free drop scenarios.
From the transportation point of view Ansaldo Nucleare has begun to demonstrate the compliance of CONTAS design with IAEA SSR-6, as Type IP-3 package.
Ansaldo Nucleare has recently awarded a contract for the supply of CONTAS for the conditioning of ILW internals at Garigliano spent nuclear plant. For this specific application, Ansaldo Nucleare is aiming to:
• design internal baskets to host the waste streams
• design an impact limiter for transportation purpose
• provide additional shielding devices where needed
• complete the qualification of CONTAS both as IP-3 and B(U) package according to the reference Standards, in particular IAEA SSR-6, by performing a mix of other experimental and analytical tests
