Session: 05-06: LLW Treatment & Packaging Developments

Paper Number: 110225

110225 - Contas - Design and Qualification of a High Integrity Container for Intermediate Level Solid Waste 

Ansaldo Nucleare S.p.A. has recently designed, fabricated and qualified a high integrity container, named CONTAS, for the conditioning, transportation and long term storage of solid ILW with low content of alfa-emitter radionuclides. Based on national and international norms and standards (e.g., UNI 11784:2020 as the reference norm in Italy) CONTAS shall comply with stringent requirements to ensure protection of persons and environment.

CONTAS is a cylindrical container 1500mm high by 1100mm in external diameter, having a maximum internal usable height of 1165mm by and internal diameter of 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:

•    the container body and lid are made in carbon steel P355QH1 obtained by semifinished product

•    the nominal mass (full load) is 10.000kg

•    two blind flanges close secondary openings: the first one used to drain the container when loaded underwater, as well as to measure the internal pressure during operation, the second one to vent the container during draining and to verify the leak tightness through suitable control volumes

•    the body end and lid profiles ease the stacking

•    the primary sealing system (between body and lid) is made by two axial gaskets in series, co-planar, tightened in the direction coaxial with respect to the cylinder axis through bolting. The gaskets are energized metallic C-rings and their design ensures the sealing performances in every design condition including accidental events

•    the secondary sealing systems are made each by an energized metallic C-ring in series with an NPT plug; the tightening of the flanges is obtained by bolting

•    each sealing system is provided with a control volume inspectable during CONTAS operation, preserving the overall leak tightness of the package

•    several geometrical details are aimed at preventing contaminated water or particulate stagnation, especially during waste loading (e.g., conical floor, bolt head seats, drain holes for bolts, inserts)

•    lifting devices are compatible with both lateral and bottom lifting

•    the container is suitable to host standard 220 liters drums, super-compacted discs, or additional shielding panels.

Several innovative elements of CONTAS, especially concerning the sealing systems, are currently patent pending.

CONTAS design, within the scope of a proper defined Qualification General Plan, has been successfully qualified through a mix of experimental and analytical tests, the latter performed both on material samples or even full-scale prototypes, arranging the test sites in compliance with the criteria defined by standards and involving qualified Suppliers and Laboratories.

Experimental tests include:

•   free drop test on a target rigid platform realized in compliance with IAEA SSR-6 and SSG-26

•   thermal test

•   degradation tests

•   dynamic characterization of materials for the FEM model validation

•   leak tightness tests

•   pressure test

•   functional tests (assembly, handling, lifting, stacking, etc.)

Furthermore, once the FEM model and methodology has been validated by comparison of numerical results with experimental ones, multiple dynamic simulations were launched using the validated FEM model to assess the consequences of as many free drop scenarios.

Therefore, Ansaldo Nucleare demonstrated compliance of CONTAS design with:

•    UNI 11784, as container for the conditioning of solid ILW aimed at transportation and long term storage at DNPT (“Deposito Nazionale e Parco Tecnologico”) or other national interim repositories

•    IAEA SSR-6, as Type IP-3 package

•    “Raccolta V.S.R.”, as pressure equipment for nuclear purpose

CONTAS is also potentially suitable for the qualification as Type B(U) packages, according to IAEA SSR-6, but it still needs the completion of the testing activities to demonstrate the conformity to the inherent specific requirements, such as the Accidental Conditions of Transport (mechanical, thermal and water immersion tests).

Presenting Author: Thomas Coltella Ansaldo Nucleare s.p.a.

Presenting Author Biography: Thomas Coltella, born in Genoa on 18th August 1977.
Senior Engineer in Ansaldo Energia Group since 2002 (Ansaldo Fuel Cells since 2002 to 2011, Ansaldo Nucleare since 2011 to 2023).
Experienced in the design and qualification of packages for LLW and ILW solid waste.
Member of UNICEN workgroup to issue the reference norm for the design and the qualification of packages for LLW/ ILW transport, storage and final disposal in the italian territory.