SPENT FUEL TRANSPORT USING A CASK LOADED OUTSIDE THE POOL

During the last year, SOGIN (the Italian company in charge for decommissioning of Italian NPPs) had to predispose an accelerated decommissioning plan of EUREX pool due to the finding of a water leakage toward environment from the pool. EUREX is a no more operating pilot reprocessing plant passed some years ago under the responsibility of Sogin. There were 52 spent FAs from Trino Vercellese PWR nuclear power plant, 48 irradiated pins from a Garigliano BWR FA, and 10 plates from an irradiated MTR FA stored in the EUREX pool, so the first steep of such accelerated decommissioning plan consisted in the evacuation of this spent fuel. Considering the necessity to start the evacuation as soon as possible, Sogin decided to use an already existing cask (AGN-1) used in the past for the transport of Trino and Garigliano FA. This cask has been requalified in order to obtain transport licence for the FAs stored in EUREX pool according to ADR 2005 regulation. Transport license for AGN-1 cask loaded with EUREX FAs was released by APAT (Italian Safety Authority) in the spring of 2007. Due to limited capacity of EUREX pool crane (27 t for nuclear loads) and limited dimensions of pool operational area, it was not possible to transfer the AGN-1 cask (50 t) inside the pool for FAs charging. The solution implemented to overcome this problem has been the loading of cask outside the pool. A special shielding shuttle was developed and used to allow safe spent fuel transfer between the pool and cask. This procedure avoided also problem of excessive contamination of cask surface that should had been arisen in case of cask immersion in the pool due to very high level of contamination of EUREX pool water. Some other shielding devices were developed and used to reduce dose rate during cask loading operations. Nevertheless the evacuation of spent fuel assemblies from EUREX pool was a very challenging activity due to short time available, unfavourable space conditions inside pool building and handling tools limitations, all loading and transport operations were performed successfully and without particular problems. 10 transports were carried out to evacuate all spent fuel stored in EUREX pool. Spent fuel was transferred to Avogadro Deposit pool. First loading sequence start the 2nd of May 2007 and the first transport was performed the 6th of may 2007. The 10th and last transport was performed the 21st of July 2007. A dose less than 50 µSv (neutron + gamma) has been measured for the most exposed operator during a complete cask loading sequence.