The use of the CONSTOR® cask concept for light water reactor fuel

The company GNB has developed a new dual-purpose cask concept – the CONSTOR® – which fulfills both the safety criteria for storage and for transport. Two variants of the CONSTOR® cask are designed for 32 PWR or 69 BWR spent fuel assemblies (SFA) with high burnups (up to 60 GWd/MTU) and high heat loads (up to 32 kW/cask). The CONSTOR® consists of a thick-walled cylindrical sandwich cask body, including an inner liner fabricated from stainless steel, and an outer liner fabricated from fine-grained steel. The liners are welded to a massive stainless steel head ring to form a double barrier containment. For additional gamma and neutron shielding, the cavity between the liners is filled with CONSTORIT consisting of iron aggregate and cement. Heat-conducting elements are arranged inside the CONSTORIT layer, and on the outer cask surface there are fins improving the dissipation of the decay heat. A double lid-system is available in a welded or a bolted version. Depending on the fuel type, two different baskets are designed for the CONSTOR® cask. To fulfill the hypothetical accident condition requirements for transport, an overpack and two impact limiters are attached to the loaded cask to form the transport package. \"Design by analysis\" is used to demonstrate regulatory compliance. Analyses are performed using IAEA- and NRCaccepted codes and conservative assumptions. In a special experimental programme, the mechanical and thermodynamical properties of CONSTORIT were verified and the reference values required for the safety analyses were determined. The thermal and mechanical behaviour of the CONSTOR® design has been tested by an extensive test programme using a ½ scale model. A full-scale prototype drop test series will be performed in the near future. At PATRAM, a prototype CONSTOR® transport package consisting of a cask with dummy basket, an overpack and two impact limiters will be subjected to 9-meter free drop test at Horstwalde near Berlin.