Nuclear Plant with a Pebble Bed Nuclear Reactor

Abstract

This invention relates to a nuclear plant including a main power system and a fuel handling and storage system. The system is connected to a sphere inlet and a sphere outlet of a multi-pass high temperature gas cooled pebble bed reactor. The system is configured such that gas flows from the system into the reactor through both the sphere inlet and the sphere outlet thereby inhibiting the ingress of high temperature gas from the reactor into the system. Restricting indexers permit the movement of spheres between the reactor and the system and dampen out the transmission of pressure fluctuations from the power system to the system.

1 . A nuclear plant which includes
 a pebble bed nuclear reactor having at least one sphere inlet at or towards an upper end thereof and at least one sphere outlet at or towards a lower end thereof; and   a fuel handling and storage system which includes   sphere flow path defining means defining a sphere flow path having a sphere inlet connected to the sphere outlet of the reactor and a sphere outlet connected to the sphere inlet of the reactor; and   sphere flow path pressurizing means configured to create a flow of gas along at least part of the sphere flow path to convey spheres along the at least part of the sphere flow path and to pressurize the sphere flow path such that the pressure at the sphere inlet of the sphere flow path is higher than the pressure at the sphere outlet of the reactor and the pressure at the sphere outlet of the sphere flow path is higher than the pressure at the sphere inlet of the reactor such that gas flows from the fuel handling and storage system into the reactor.   
   
   
       2 . A nuclear plant as claimed in  claim 1 , which includes damping means configured to permit the passage of spheres between the reactor and the fuel handling and storage system and to dampen the transmission of pressure fluctuations in coolant of the reactor to the fuel handling and storage system. 
   
   
       3 . A nuclear plant as claimed in  claim 1 , in which the sphere flow path pressurising means includes a blower having an inlet and an outlet, the blower outlet being connected to the sphere flow path at a gas inlet and the blower inlet being connected to the sphere flow path at a gas outlet, the gas inlet being positioned at a level which is lower than the level of the sphere inlet of the sphere flow path such that spheres entering the sphere flow path from the reactor will move under the influence of gravity to the gas inlet where they will be entrained in a gas stream flowing through the sphere flow path and conveyed away from the gas inlet. 
   
   
       4 . A nuclear plant as claimed in  claim 3 , which includes a top flow restricting indexer positioned, relative to the direction of movement of the spheres, upstream of the sphere inlet of the reactor and a bottom flow restricting indexer positioned downstream of the sphere outlet of the reactor. 
   
   
       5 . A nuclear plant as claimed in  claim 4 , in which the top flow restricting indexer is positioned between the gas outlet of the sphere flow path and the sphere inlet of the reactor and the bottom flow restricting indexer is positioned between the sphere outlet of the reactor and the gas inlet of the sphere flow path. 
   
   
       6 . A nuclear plant as claimed in  claim 3 , which includes
 a closed loop main power system which includes, in addition to the nuclear reactor, in series, at least one turbine and at least one compressor; and   a feed line for feeding gas from the main power system to the fuel handling and storage system to replace gas which flows from the fuel handling and storage system into the reactor.   
   
   
       7 . A nuclear plant as claimed in  claims 6 , in which the main power system includes a recuperator having a hot or low pressure side connected between the at least one turbine and the at least one compressor, and a cold or high pressure side connected between the at least one compressor and a gas or working fluid inlet of the reactor, the feed line leading from the main power system from a position between the at least one compressor and the cold side of the recuperator and being connected to the fuel handling and storage system between the gas outlet and the inlet of the blower. 
   
   
       8 . A nuclear plant which includes
 a pebble bed nuclear reactor having at least one sphere inlet at or towards an upper end thereof and at least one sphere outlet at or towards a lower end thereof; and   a fuel handling and storage system which includes   sphere flow path defining means defining a sphere flow path having a sphere inlet connected to the sphere outlet of the reactor and a sphere outlet connected to the sphere inlet of the reactor; and   damping means configured to permit movement of the spheres between the reactor and fuel handling and storage system and to dampen the transmission of pressure fluctuations in the coolant of the reactor gas to the fuel handling and storage system.   
   
   
       9 . A nuclear plant as claimed in  claim 8 , in which the damping means includes a top flow restricting indexer positioned, relative to the direction of movement of the spheres, upstream of the sphere inlet of the reactor and a bottom flow restricting indexer positioned downstream of the sphere outlet of the reactor. 
   
   
       10 . A method of operating a nuclear plant having a pebble bed nuclear reactor having a sphere outlet and a sphere inlet and a fuel handling and storage system for conveying spheres from the sphere outlet of the reactor to the sphere inlet of the reactor which method includes the step of pressurising the fuel handling and storage system to create a leak flow from the fuel handling and storage system to the reactor. 
   
   
       11 . A method as claimed in  claim 10 , in which the leak flow from the fuel handling and storage system to the reactor is through both the sphere outlet and sphere inlet of the reactor. 
   
   
       12 . A method as claimed in  claim 1  in which the nuclear plant includes a closed loop main power system of which the reactor forms part and the method includes feeding gas from the main power system into the fuel handling and storage system to replace gas leaked from the fuel handling and storage system into the reactor. 
   
   
       13 . A method as claimed in  claim 12 , in which the gas is fed from the main power system from a position where the gas in the main power system is at maximum pressure.