Small, fast neutron spectrum nuclear power plant with a long refueling interval

Abstract

Nuclear reactor systems and methods are described having many unique features tailored to address the special conditions and needs of emerging markets. The fast neutron spectrum nuclear reactor system may include a reactor having a reactor tank. A reactor core may be located within the reactor tank. The reactor core may include a fuel column of metal or cermet fuel using liquid sodium as a heat transfer medium. A pump may circulate the liquid sodium through a heat exchanger. The system may include a balance of plant with no nuclear safety function. The reactor may be modular, and may produce approximately 100 MW e .

1 .- 24 . (canceled) 
     
     
         25 . A wedge for a core clamping system, the wedge comprising:
 a first end and a second end wherein the first end has less surface area than the surface area of the second end;   a driveline coupled to a vertical positioning mechanism connected to a reactor deck;   wherein the wedge is vertically adjustable; and   said wedge is configured to loosen a nuclear fuel core assembly for fuel handling.   
     
     
         26 . The wedge of  claim 25 , wherein the wedge is at a lower end of the drive line. 
     
     
         27 . The wedge of  claim 25 , wherein the wedge is inserted into the nuclear fuel core assembly 
     
     
         28 . The wedge of  claim 27 , wherein the wedge is capable of re-insertion to clamp the nuclear core fuel assembly. 
     
     
         29 . The wedge of  claim 25 , wherein the wedge can be inserted to clamp the nuclear core fuel assembly and top load pads outward against a core former ring at a top pad elevation. 
     
     
         30 . The wedge of  claim 29 , wherein the top load pads surround a ducted fuel assembly. 
     
     
         31 . The wedge of  claim 30 , wherein the top load pads surround the ducted fuel assembly above a fuel elevation and below the top load pads. 
     
     
         32 . The wedge of  claim 25 , wherein a vertical position of the wedge is adjusted throughout the nuclear core fuel assembly's life to adjust the core reactivity values. 
     
     
         33 . The wedge of  claim 25 , wherein the vertical position of the wedge is adjusted to loosen the nuclear core fuel assembly. 
     
     
         34 . The wedge of  claim 25 , wherein the vertical position of the wedge is used to adjust nuclear core fuel assembly radial expansion. 
     
     
         35 . The wedge of  claim 25 , wherein the vertical position of the wedge may be in response to increased core coolant temperature. 
     
     
         36 . The wedge of  claim 35 , wherein the wedge's vertical position is moved downward from the wedge's initial vertical position in response to the increased core coolant temperature. 
     
     
         37 . The wedge of  claim 36 , wherein the downward position of the wedge causes increased axial leakage and reduced reactivity of the nuclear core fuel assembly. 
     
     
         38 . A method for constructing a modular nuclear reactor system comprising:
 providing a reactor comprising:
 a reactor tank; 
 a reactor core within the reactor tank, the reactor core comprising a fuel column of metal or cermet fuel using liquid sodium as a heat transfer medium; and 
 a pump for circulating the liquid sodium through a heat exchanger; and 
   providing at least one passive safety system comprising reactivity feedbacks;   wherein the system is configured so a balance of plant does not need a nuclear safety function; and   providing an energy converter with approximately 40% or more conversion efficiency;   wherein the reactor is modular, and   wherein the system produces between approximately 50 MW e  to approximately 100 MW e .   
     
     
         39 . The method of  claim 38 , further comprising providing a small-volume containment structure comprising a guard vessel and a dome over a reactor deck, and wherein the small-volume containment structure is emplaced in a silo shield structure with seismic isolation. 
     
     
         40 . The method of  claim 38 , further comprising providing a passive safety system. 
     
     
         41 . The method of  claim 38 , wherein a first loading is enriched uranium at less than approximately 20% enrichment, and all subsequent loadings are recycled uranium, transuranics and zirconium. 
     
     
         42 . The method of  claim 38 , wherein a refueling interval is approximately 20 years, and the whole reactor core is replaced during refueling. 
     
     
         43 . The method of  claim 38 , further comprising one or more multi-assembly clusters. 
     
     
         44 . The method of  claim 38 , wherein the one or more multi-assembly clusters have derated specific power (kwt/kg fuel) for enabling long refueling intervals and enabling refueling operations to begin approximately two weeks after reactor shutdown. 
     
     
         45 . The method of  claim 38 , further comprising providing a removable and adjustable wedge in the reactor core at above core load pads elevation for core clamping and fine tuning adjustments of the reactivity feedbacks. 
     
     
         46 . The method of  claim 38 , wherein thermal efficiency of the system is between approximately 39% and approximately 41%. 
     
     
         47 . The method of  claim 38 , wherein an internal breeding ratio is approximately unity. 
     
     
         48 . The method of  claim 38 , wherein the energy converter is a Brayton cycle energy converter. 
     
     
         49 . The method of  claim 38 , wherein the energy converter is a Rankine steam cycle.