Patent GB-1454239-A (GB)
Title: Process for handling fuel assemblies which have been irradiated in a fast neutron nuclear reactor and installation for performing the process
IPC: G21C19/32
Filed: 1974-06-25
Abstract: 1454239 Fuelling reactors COMMISSARIAT A L'ENERGIE ATOMIQUE 25 June 1974 [27 June 1973] 28141/74 Heading G6C In a fast reactor comprising an open pressure vessel 2 hung in a protective enclosure 1 which has thick concrete walls and which is closed by a horizontal concrete slab 7 disposed above the level 4 of a liquid metal coolant for the reactor core 3, an irradiated fuel assembly 12 which has a high residual power and which has been lifted out of the core 3 by the handling device 10, 11 is immediately removed from the pressure vessel 2, without any storage time in the pressure vessel, and transferred to a receptacle outside the pressure vessel while immersed in liquid metal within a handling flask 14, e.g. of the type disclosed in Specification 1,332,888, adapted to remove the heat evolved by the assembly. The flask is moved up along an inclined surface 15 by means of a winch (not shown) into a pivoting hood 17, e.g. of the type disclosed in Specification 1,408,698. After rotation of the hood 17 through 180 degrees, the flask 14 is lowered down an inclined surface 20 extending through slab 7 into a chamber 21 within the concrete walls of enclosure 1. Chamber 21 contains a receptacle 22 filled to a level 23 with liquid metal and provided with a vertical pocket 24 adapted to receive the flask 14. A handling device 26 mounted in a rotatable plug 25 enables the assembly 12 to be lifted from the flask 14 on to a turntable 31 by means of which it is moved into vertical alignment with one of several orifices 37. Spent fuel assemblies can be placed in a number of concentric rings on the tray 30 of turntable 31 from which they are removed by the grab of a transfer carriage 40 and introduced into a processing passage lock 38 bounded by a concrete wall. 39. In a constructional variant (Fig. 2, not shown) the carriage 42 is replaced by a turntable (42a). A sealing element 45 in the floor 51 of the lock 38 separates the contaminated atmosphere within the lock 38 and above the liquid metal in receptacle 22 from the atmosphere within a cell 46 where the spent assembly is placed inside a coffin 47. Means (not shown) associated with the element 45 are operated to seal the mouth of the coffin top in a leak-proof manner. The coffin 47 is then moved across cell 46 by means of a carriage 48 running on rails 49 and brought under an exit 50 covered by a hood 52 to protect the environment from radiation coming from the spent assembly through the coffin wall. The hood 52 with the coffin in it is then moved to above an aperture communicating with a shielded transportation flask 54 borne by a lifting system 55. The flask 54 which usually contains a number of spent assemblies is then taken to a reprocessing works. By means of the pivoting hood 17 a spent fuel assembly is removed from the core 3 simultaneously as a fresh fuel assembly is charged into the hood, whereafter the hood is rotated through 180 degrees so that the spent assembly can be lowered into the receptacle 22 and the fresh assembly lowered into the pressure vessel 2. Accordingly the receptacle 22 has, with advantage, a passage for introducing the fresh assemblies which are disposed in a ring reserved for such assemblies on the periphery of the turntable tray 30.