Low power pressure tube nuclear reactor

Abstract

A low-power nuclear reactor includes a housing and a reflector forming a reactor core. The core includes inner and outer primary tubes therein, arranged together as bayonet tubes and intended for circulating a coolant, and secondary tubes, accommodating elements of a control and protection system. The reactor further includes an intake chamber for coolant of a primary loop, and a discharge chamber for coolant of the primary loop, separated by a partition. The outer primary tubes are secured on the intake chamber's bottom, and the inner primary tubes are secured on the partition. Fuel assemblies are mounted in the inner primary tubes on suspensions, which are mounted on the discharge chamber's upper portion. The secondary tubes are sealed off from the intake and discharge chambers for the coolant of the primary loop, and an inter-tube space of the core is filled with a medium or material transparent to neutrons.

Claims

1. A nuclear reactor, comprising: a housing with a reflector, forming a reactor core including an inner space; first process channels, located in the reactor core, designed for coolant circulation; second process channels, located in the reactor core, designed for placement of control and protection system components; a plurality of fuel rod arrays; a first coolant loop; wherein: the first coolant loop comprises a supply chamber including a bottom and a discharge chamber separated from the supply chamber by a partition; the first process channels are designed as bayonet tubes, each said bayonet tube includes an external tube and an internal tube, each said external tube is attached to the bottom of the supply chamber, and each said internal tube is attached to the partition; each fuel rod array of said plurality of fuel rod arrays is installed on a suspender, inside of each corresponding said internal tube, wherein the suspender is attached to an upper part of the discharge chamber; the second process channels are isolated from the supply chamber and the discharge chamber; and the inner space of the reactor core is filled with medium or material transparent for neutrons.

2. The nuclear reactor according to claim 1, wherein: the reflector comprising a side reflector designed as a pack of rings, an upper reflector and a lower reflector.

3. The nuclear reactor according to claim 1, wherein: the inner space is filled with a zirconium alloy.

4. The nuclear reactor according to claim 1, wherein: said control and protection system components include control and protection system controls located at an upper part of the discharge chamber.

5. The nuclear reactor according to claim 1, wherein: said control and protection system components include emergency protection absorbing rods, compensating rods, and absorbing control rods.

6. The nuclear reactor according to claim 5, wherein: the compensating rods and the emergency protection absorbing rods include an absorber consisting of B.sub.4C enriched to 80% for .sup.10B.

7. The nuclear reactor according to claim 5, wherein: the control rods include an absorber consisting of B.sub.4C enriched to 20% for .sup.10B.

8. The nuclear reactor according to claim 1, wherein: said plurality of fuel rod arrays include a part of fuel rods filled with Gd.sub.2O.sub.3 burnable absorber.

9. The nuclear reactor according to claim 1, wherein: said plurality of fuel rod arrays include a part of fuel rods filled with Er burnable absorber.

10. The nuclear reactor according to claim 1, wherein: said plurality of fuel rod arrays include a first number of fuel rods filled with Gd.sub.2O.sub.3 burnable absorber and a second number of fuel rods filled with Er burnable absorber.

Description

BRIEF DESCRIPTION OF DRAWINGS OF THE INVENTION

(1) To better understand the idea of the proposed technical solution, a description of the exact example of invention is given below, which is not a limiting example of a practical implementation of a nuclear reactor in accordance with this invention with references to drawings, where the following is depicted.

(2) FIG. 1 shows an axonometric section of the general layout of the reactor in accordance with this invention.

(3) FIG. 2 shows a coolant supply and discharge chamber design of the first loop with locations of first process channels.

(4) FIG. 3 shows a design of suspenders for fuel rod arrays and second process channels.

(5) FIG. 4 shows a design of first process channels with fuel rod arrays.

(6) FIG. 5 shows a cross-section of the reactor's reactor core.

(7) FIG. 6 shows view A of FIG. 5.

(8) FIG. 7 shows view B of FIG. 5.

DETAIL DESCRIPTION OF THE INVENTION

(9) While the invention may be susceptible to embodiment in different forms, there are described in detail herein, specific embodiments of the present invention, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as exemplified herein.

(10) The principal structural layout of the reactor is shown in FIG. 1. The reactor consists of a metal housing 1, within of which an reactor core 2 of the reactor is located, formed by reflector 3. First process channels 4, designed for the first loop coolant circulation, and second process channels 5, designed for the placement of CPS components are located within the reactor core.

(11) First loop coolant supply chamber 6 and discharge chamber 7, separated by partition 8 are located above reactor core 2. CPS controls 9 are located above the first loop coolant discharge chamber 7.

(12) Reflector 3 consists of a side reflector, designed as a pack of individual rings 10, lower reflector 11 and upper reflector 12. AlBe alloy is used as a material for the reflector 3.

(13) As shown in FIG. 2, first loop coolant supply chamber 6 consists of lid 13 of housing 1 of the reactor, side wall (housing) 14 and partition 8. Ducts 15 (FIG. 3) are located on side wall 14, which feed the first loop het carrier to supply chamber 6 by circulating pumps. Water H.sub.2O is used as a first loop coolant.

(14) As shown on FIG. 3, the first loop coolant discharge chamber 7 is formed by partition 8, side wall 16 and upper lid 17. Ducts 18 are placed on side wall 16, which are used to carry the first loop coolant from chamber 7 to the heat exchanger, which can be designed as a steam generator.

(15) First (fuel) process channels 4 (FIG. 2) are designed as Field tubes, each containing external tube 19 and internal tube 20. External tube 19 is welded into lid 13 of the reactor housing 1, designed as a tube plate with holes placed along the triangular grid. Internal tube 20 is welded into partition 8 between supply chamber 6 and discharge chamber 7 of the first loop coolant, which (partition) is designed also as a tube plate with holes corresponding to holes of lid 13.

(16) Second (controlling) process channels 5 (FIG. 3) each containing tube 21, placed in the reactor core 2, and tube 22, passing through supply chamber 6 and discharge chamber 7 of the first loop coolant, and isolating second process channel from the coolant. The space 23 (FIG. 4) between process channels in the reactor core 2 is filled with zirconium alloy E-110, which has a small neutron absorption cross-section.

(17) The locations of first and second process channels in the reactor core 2 are shown in FIG. 5.

(18) Suspenders of fuel rod arrays 24 are installed on the upper lid 17 (FIG. 3) of the first loop coolant discharge chamber 7. Fuel rod array 24 consists of the central rod 25, at the lower end of which a bundle of 18 fuel rods 26 is attached. A special flange 27 is located at the upper end of the central rod 25 to tighten suspenders of fuel rod array 24 on the upper lid 17 and to grip fuel rods while installing and removing it from the reactor core 2.

(19) The coolant from circulating pumps through ducts 15 feeds into supply chamber 6 of the coolant to first process channels. Then, as shown in FIG. 2, along the space between external tube 19 and internal tube 20 of Field tubes, fed pre-heated into the reactor core 2. Further, as shown in FIG. 4, the coolant travels to internal tube 20, where fuel rod array 24 is located. Traveling through the fuel rod array, the coolant is completely heated to the required temperature and returns to coolant discharge chamber 7, and then, through ducts 18, fed to the heat exchanger.

(20) Such design of fuel channels allows to half linear dimensions of the reactor core, in our case, the height. Furthermore, an evenness and effectiveness of the heat removal due to a partial heat dissipation at the coolant outlet from internal tubes 20 to the coolant at the inlet to external tubes 19. Also, fuel rod heat load distribution along their lengths is improved.

(21) The reactor design is simple, which ensures a total compensation of temperature deformations. All of this allows to ensure a large consumption of the coolant through a reactor core, which increases rated power and gives a heat power capability of 20 MW at small dimensions.

(22) The described reactor's fuel rods are enriched uranium dioxide. Advantages include an optimal processing of this type of fuel, confirmed by its usage for thousands of reactor years. Uranium enrichment for nuclear fuel production is limited to 20% in accordance with IAEA requirements to prevent a proliferation of nuclear weapons. The chosen enrichment equals to 19% by uranium-235 content (enrichment, similar to production fuel for BN-800 reactors). A choice of the maximum allowed value of enrichment allows to reduce the size of the reactor core, reaching the required reactivity margin and high depth of burning.

(23) To ensure long operational life of the reactor without overloads, a large reactivity margin (around 22%) is required. A compensation of such margin at minimum number of absorbing rods in the reactor core and ensuring an internal self-defense are achieved by using fuel with burnable absorber. Erbium (Er) and Gadolinium (GdC) are used as burnable absorbers.

(24) The positions and content of fuel rods of the fuel rod array 24 are shown in FIG. 7. A fuel rod array contains three Er fuel rods 28, three Gd.sub.2O3 fuel rods, and twelve rods 30 that do not contain a burnable absorber.

(25) The reactor control is performed by thirteen regulating CPS controls (FIG. 2), each one of them is designed as a pack of seven absorbing rods 32 (FIG. 6). All packs of CPS absorbing rods are divided into the following groups, according to their purpose: four packs 33 of compensating rods, ensuring a compensation of the reactivity margin of the reactor, created by the loss of reactivity as a result of fuel burning; two packs 34 of control rods, ensuring control and support for the reactor power during its operation; seven packs 35 of emergency protection rods, ensuring a quick decrease in power and switching the reactor to sub-critical mode when there are normal operation failures and emergency situations.

(26) As shown in FIG. 5, twelve packs of absorbing rods are located along the hexagon perimeter and one pack (emergency protection) is located at the center of the reactor core. Packs 34 of control rods are symmetric to each other relative to the reactor core center.

(27) B.sub.4C, enriched to 80% to .sup.10B, is used for compensating and emergency protection rods, and B.sub.4C, enriched to 20% to .sup.10B, is used for absorbing and control rods.

(28) The proposed invention is not limited to the abovementioned options of its practical implementation. Thus, for example, we can assume that using internal designs, having the shape, quantity of components and locations differ from those described above.