Patent GB-1067914-A (GB)
Title: Swimming pool reactor
Inventor: AGERON PAUL
IPC: G21C7/08
Filed: 1964-10-26
Abstract: 1,067,914. Reactors. COMMISSARIAT A L'ENERGIE ATOMIQUE. Oct. 26, 1964 [Oct. 30, 1963], No. 43559/64. Heading G6C. A swimming pool reactor comprises a core 3 formed by vertical fuel assemblies 4 of parallel plates placed in a water-filled metal enclosure 8 which is open at the top, the core 3 being cooled by a rising flow of water, means being provided for withdrawing water through side orifices 22, 23 in the enclosure 8 and for partly decontaminating and cooling the water, means being provided for returning most of such water to the bottom of the core 3 and the remainder to the top of the enclosure 8 above the orifices 22, 23, and deflectors 20 being disposed at the top of each fuel assembly 4 to direct the water which leaves the core 3 towards the orifices 22, 23. The enclosure 8, which has a movable dam 8a for introducing experimental apparatus near the core 3, stands in a concrete vessel 1 filled with water to a level 2 and divided halfway up by an annular plate 25, while inside the enclosure 8 are four metal plates (only two, viz. 9 and 10, are shown in Fig. 1) rigidly secured to the enclosure and supporting a grid 11. On the floor of the vessel 1 is a grid 7 of similar dimensions to the grid 11, the former bearing the fuel assemblies 4 by means of metal support members 5 while the latter maintains them vertical. Some of the sockets in the grids have no fuel assemblies and these enable experimental apparatus, such as test loops 15, 16 to be placed in or near the core. Sockets which have neither fuel assemblies nor experimental apparatus receive members similar to the members 5, but having at their tops square plates 17 which close the sockets in the grid 11. The cooling water, which is cooled by heat exchangers (not shown), is delivered by pumps (not shown) through two passages 18, 19 extending to the region of the members 5. The cooling water rises through the assemblies 4 and in order to force it through the whole of the active mass before it overflows into the swimming pool at the top of the core 3, a caisson (not shown) is placed around the core 3 and each fuel assembly is surrounded by a box which is open at both ends. The mean pressure in the core is the sum of the static pressure due to the height of water in the swimming pool above the core plus the load loss in the fuel assemblies, and is sufficient to prevent boiling of the cooling water. The water passing through the orifices 22, 23 enters a deactivating chamber 24 below the annular plate 25, from where it is conveyed outside the reactor through ducts 26, 27 and is further decontaminated (e.g. by ion exchange) and cooled by heat exchange before being recycled. To ensure that active water cannot rise to the surface 2, a downward flow of water is provided at the top of the swimming pool, this water being taken from the core cooling circuit after the deactivating chamber 24 and introduced at the top of the enclosure 8 by a distributing system 29. To reduce natural convection flows at the top of the swimming pool, a diffuser 32 is provided to maintain a layer of hot water at the surface 2. Each fuel assembly 4 has a transverse plate 30 secured by means of a structure 31 which forms part of a support member 5 and is made of metallic baffles through which the cooling water can pass. The function of the plate 30, upon which the water acts vertically downwards, is to prevent the fuel assembly 4 from being raised by the pressure of the cooling water issuing from the passages 18, 19. The coolant circulating pumps have flywheels so that delivery is sufficient during the first few seconds after the reactor has stopped or after the power has been reduced. When the pressure of the core circuit water becomes equal to that of the swimming pool water, a valve disposed upstream of the core in the passages 18, 19 outside the enclosure 8 opens and interconnects the core and swimming pool. Cooling is then by natural convection. This device also operates in the event of breakdown of the pumps.