Nuclear Plant Shutdown: a Challenge for the Competent Authority

In Sweden in recent years it has been decided that certain old reactors will be shut down in the near future. To enable the nuclear power plants to enter decommissioning, all nuclear fuel and other nuclear materials must first be removed from the plant. This includes damaged nuclear fuel and used nuclear core detectors containing gram quantity of U-235.Depending on the damaged fuel type, from BWR and PWR, there are two methods for encapsulation for intermediate storage at SKB's Clab facility and for later final storage: the \"Westinghouse Quiver method\" adapted for final storage, and the \"Studsvik method\", where encapsulation takes place at the Studsvik site before further transportation to final handling. In addition, logistical differences regarding the types of transport packages that can be handled by both consignor and consignee also necessitate different solutions for safe transportation within the terms of transport regulations.The below are solutions designed by the Swedish Radiation Safety Authority, the competent authority in Sweden for shipments of radioactive materials regardless of the mode of transport:Using “Quivers” as a method to encapsulate damaged fuel on site to replace the function of the cladding. The quivers can therefore be implemented for use in new revisions of package designs already used for shipments of irradiated fuel. Likewise if needed, for Special Arrangement Transport.Regarding the “Studsvik method”, a package design specially made for damaged nuclear fuel may be used. However, since this solution cannot be used for one Swedish NPP, Special Arrangement Transport using an old package design had to be used for a few transports, e.g. to prevent static and kinetic energy buildup during shipment.In order to transport used core detectors (containing U-235) in a package designed for non-fissile internal parts together on the same marine vessel with (fissile) packages containing spent fuel (thus “excepted fissile” cannot be used), the use of exception 6.4.11.2 (b) per IMDG Code 2018 edition was implemented in the new revision of the package design certificate (total CSI less than 10).