Nuclear Safety Analysis for Transport Cask TK-6 (for VVER-440) and Cover for Fresh Assemblies (for VVER-1000) in Implementation of new Fuel Types at Ukrainian NPP
16th Symposium of AER on VVER Reactor Physics and Reactor Safety (2006, Bratislava, Slovakia)
Physical Problems of Spent Fuel Decommissioning and Radwaste
According to the fresh fuel management procedure, fuel assemblies – after nuclear fuel delivery to the NPP fresh fuel unit – are vertically loaded into a cover intended for the delivery of fuel assemblies into the containment of the NPP reactor compartment. The cover is placed into an universal jack in the cooling and refueling pond, and then the fresh fuel assemblies are loaded into the reactor core. Based on the nuclear safety analysis carried out by the Russian Research Center “Kurchatov Institute” for contemporary WWER-1000 fuel, it has become necessary to limit the number of fuel assemblies loaded into a cover below its designed capacity (12 FA instead of 18 FA as originally designed). Such a decision leads to worse economic performances in fuel transportation. The paper considers potential ways to overcome this restriction.
Transport container TUK-6 for spent fuel assemblies was designed quite a long time ago and, as shown in this paper, the requirement on the maximally permissible neutron multiplication factor of the loaded container for individual states to be analyzed in compliance with Ukrainian regulations is not met. First of all, this concerns the container criticality analysis in optimal neutron slow-down (container filling with water-air mixture with optimal density). The paper shows potential ways for TUK-6 burnup-credit loading with the maximum number of fuel assemblies and partial container loading.