NATURAL CIRCULATION BOILING WATER REACTOR

Abstract

A core disposed in a reactor pressure vessel includes one layer (an outermost region) at an outermost side of the core, two-three layers (an outer region) inside the outermost region and other layers (an inner region) inside the outer region. Fuel assemblies arranged in the core are supported by fuel supports having orifice. Orifice pressure loss coefficient of the orifice in the outermost region is set to be maximum and the orifice pressure loss coefficient of the orifice in the outer region is set to be minimum such that the flow rate of the coolant W for each fuel assembly in the outermost region is lowest and that for each fuel assembly in the outer region is highest. In the core of the natural circulation boiling water reactor, the reactor power distribution in a radial direction is flattened, and it is possible to increase the thermal margin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural view showing a natural circulation boiling water reactor according to an embodiment of the present invention.

FIG. 2A is a longitudinal sectional view of a fuel assembly.

FIG. 2B is a plane view of a fuel assembly shown in FIG. 2A.

FIG. 3A is a structural view showing a fuel support disposed in an inner region of a core.

FIG. 3B is a structural view showing another fuel support disposed in an outermost region of a core.

FIG. 4 is a sectional view taken along a line X-X of FIG. 1.

FIG. 5 is a cross sectional view showing a ¼ division region of a core according to first embodiment of the present invention.

FIG. 6 is a cross sectional view showing a ¼ division region of a core according to second embodiment of the present invention.

FIG. 7 is a cross sectional view showing a ¼ division region of a core according to third embodiment of the present invention.

FIG. 8 is a cross sectional view showing a ¼ division region of a core according to the fourth embodiment of the present invention.

FIG. 9 is a cross sectional view showing a ¼ division region of a core according to fifth embodiment of the present invention.

FIG. 10 is a cross sectional view showing a ¼ division region of a core according to sixth embodiment of the present invention.

FIG. 11 is a cross sectional view showing a ¼ division region of a core according to seventh embodiment of the present invention.

Claims

1. A natural circulation boiling water reactor, comprising: a reactor pressure vessel;a core loading a plurality of fuel assemblies and disposed in said reactor pressure vessel; anda plurality of fuel supports placing in said reactor pressure vessel, for supporting said fuel assembly and forming a coolant flow path in which orifice for adjusting flow rate of coolant is disposed, for introducing said coolant to said fuel assembly,wherein said core includes an third region, a second region surrounding said third region and an outermost first region surrounding said second region in a radial direction;pressure loss coefficient for said orifice disposed in said second region is set so as to be smaller than that for said orifice disposed in said third region; andthe pressure loss coefficient for said orifice disposed in said first region is set so as to be larger than the pressure loss coefficient for said orifice disposed in said second region.

2. The natural circulation boiling water reactor according to claim 1, wherein the pressure loss coefficient for said orifice in said first region is set so as to be larger than the pressure loss coefficient for said orifice in said third region.

3. The natural circulation boiling water reactor according to claim 1, wherein a number of said orifices is equal to a number of said fuel assemblies, and said orifice is provided to said fuel support.

4. The natural circulation boiling water reactor according to claim 2, wherein a number of said orifices is equal to a number of said fuel assemblies, and said orifice is provided to said fuel support.

5. A natural circulation boiling water reactor, comprising: a reactor pressure vessel;a core loading a plurality of fuel assemblies and disposed in said reactor pressure vessel; anda plurality of fuel supports placing in said reactor pressure vessel, for supporting said fuel assembly and forming a coolant flow path in which orifice for adjusting flow rate of coolant is disposed, for introducing said coolant to said fuel assembly,wherein said core includes an fifth region and an outermost fourth region surrounding said fifth region in a radial direction, and a plurality of sixth regions disposed in said fifth region and having said fuel assembly that in-core fuel dwelling time is longer than that of said fuel assembly disposed in said fifth region;pressure loss coefficient for said orifice in said sixth region is set so as to be smaller than the pressure loss coefficient for of said orifice in said fifth region; andthe pressure loss coefficient for said orifice in said fourth region is set so as to be larger than the pressure loss coefficient for said orifice in said sixth region.

6. The natural circulation boiling water reactor according to claim 5, wherein the pressure loss coefficient for said orifice in said fourth region is set so as to be larger than the pressure loss coefficient for said orifice in said fifth region.

7. The natural circulation boiling water reactor according to claim 5, wherein a number of said orifices is equal to a number of said fuel assemblies, and said orifice is provided to said fuel support.

8. The natural circulation boiling water reactor according to claim 6, wherein a number of said orifices is equal to a number of said fuel assemblies, and said orifice is provided to said fuel support.

9. A natural circulation boiling water reactor, comprising: a reactor pressure vessel;a core loading a plurality of fuel assemblies and disposed in said reactor pressure vessel and including a plurality of control cells having a control rod and four fuel assemblies arranged around said control rod; anda plurality of fuel supports placing in said reactor pressure vessel, for supporting said fuel assembly and forming a coolant flow path in which orifice for adjusting flow rate of coolant is disposed, for introducing said coolant to said fuel assembly,wherein said core includes an eighth region and an outermost seventh region surrounding said eighth region in a radial direction, and a plurality of ninth regions disposed in said eighth region and having said fuel assembly disposed in said control cell;pressure loss coefficient for said orifice in said ninth region is set so as to be smaller than the pressure loss coefficient for said orifice in said eighth region; andthe pressure loss coefficient for said orifice in said seventh region is set so as to be larger than the pressure loss coefficient for said orifice in said ninth region.

10. The natural circulation boiling water reactor according to claim 9, wherein the pressure loss coefficient for said orifice in said seventh region is set so as to be larger than the pressure loss coefficient for said orifice in said eighth region.

11. The natural circulation boiling water reactor according to claim 9, wherein a number of said orifices is equal to a number of said fuel assemblies, and said orifice is provided to said fuel support.

12. The natural circulation boiling water reactor according to claim 10, wherein a number of said orifices is equal to a number of said fuel assemblies, and said orifice is provided to said fuel support.