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EP-4736187-A1 - NUCLEAR REACTOR CORE ARRANGEMENT AND METHOD FOR HANDLING THIS ARRANGEMENT

EP4736187A1EP 4736187 A1EP4736187 A1EP 4736187A1EP-4736187-A1

Abstract

The invention relates to a nuclear reactor core arrangement, comprising a core (6) formed of fuel assemblies (600) comprising fuel plates or rods arranged in the core parallel to a first direction (A) which constitutes a vertical direction for introducing the core into a cylindrical vessel (9) having a vertical axis of revolution (Z), the assemblies being separated by spaces for accommodating control rods (601) which are accommodated between the assemblies (600), and by passages for a heat-transfer liquid parallel to the first direction, around the fuel plates or rods, the arrangement comprising a basket (60) for supporting the core (6), provided with a first perforated plate (75) which is provided with holes (76) for the passage of the heat-transfer liquid, is arranged in a plane perpendicular to the first direction under a lower face of the core, and is intended to support the core when it is placed in the reactor vessel and when it is handled, the basket comprising lateral uprights extending along the lateral faces of the core and extending in the first direction above the core, and a second perforated plate (70) covering an upper face of the core and provided with holes for the passage of the heat-transfer liquid and cross-shaped slots for the passage of the control rods (601).

Inventors

  • VALLEE, ALAIN

Assignees

  • CALOGENA

Dates

Publication Date
20260506
Application Date
20240620

Claims (13)

  1. [Claim 1] Nuclear reactor core arrangement comprising a core (6), formed of fuel assemblies (600) comprising fuel plates or rods arranged in the core parallel to a first direction (A) constituting a vertical direction of introduction of the core into a cylindrical vessel (9) with a vertical axis of revolution (Z), said assemblies being separated by spaces for receiving control rods (601) received between said assemblies (600) and by passages of a heat transfer liquid parallel to said first direction, around the fuel plates or rods, characterized in that it comprises a basket (60) supporting the core (6), provided with a first perforated plate (75) provided with holes (76) for the passage of the heat transfer liquid, arranged in a plane perpendicular to said first direction under a lower face of the core and intended to support the core during its installation in said reactor vessel and its handling, said basket comprising lateral uprights running along the side faces of the core and extending in the first direction above the core and a second perforated plate (70) covering an upper face of the core and provided with holes for the passage of the heat transfer liquid and cross-shaped slots for the passage of said control bars (601).
  2. [Claim 2] Nuclear reactor core arrangement according to claim 1, for which the basket (60) comprises a third perforated plate (73) above the core at a distance from the upper face of the core at least equal to a height of the core between the first plate (75) and the second plate (70), said third plate (73) being provided with holes for the passage of the heat transfer liquid and holes for the passage of rods (7) for operating the control rods (601).
  3. [Claim 3] A nuclear reactor core arrangement according to claim 2 wherein the second plate and the third plate are removable.
  4. [Claim 4] A nuclear reactor core arrangement according to claim 1, 2 or 3 wherein an upper end of at least some uprights carry suitable attachment means to allow the basket to be handled.
  5. [Claim 5] Nuclear reactor core arrangement according to any one of the preceding claims, for which said lateral uprights are shaped as angles (60a), forming recesses on edges of the core parallel to said direction of introduction (A), for receiving corner reflectors (62) when the core is in position at the bottom of the vessel (9).
  6. [Claim 6] A nuclear reactor core arrangement according to any preceding claim wherein the basket is a metal structure made of steel and/or a material transparent to neutrons such as zircaloy or aluminum.
  7. [Claim 7] A nuclear reactor core arrangement according to any preceding claim wherein the basket (60) is sized to allow the core (6) to be completely removed from the vessel.
  8. [Claim 8] Nuclear reactor comprising a nuclear core arrangement according to any one of the preceding claims and a vessel, characterized in that it comprises peripheral neutron reflectors (61), in a reflective material such as beryllium, surrounding the lateral faces of the core parallel to said vertical direction of introduction when the core is in the operating position in the vessel (9).
  9. [Claim 9] Nuclear reactor according to claim 8 comprising a support (90) of the core on a bottom of said reactor vessel, said support comprising an openwork structure forming a debris filter.
  10. [Claim 10] A nuclear reactor according to claim 9 comprising a pool and in the pool a reloading bench into which the basket can be inserted and the walls of which are made of a neutron-absorbing material such as boron steel, hafnium, cadmium or other alloy used by the nuclear industry for this purpose allowing the removal of the control rods from the fuel assemblies.
  11. [Claim 11] A method of maintaining a nuclear reactor core arrangement according to any one of claims 1 to 7, characterized in that it comprises, for unloading said arrangement: a. - a shutdown of the reactor and an insertion of all the rods (601) of the control rods into the core; b. - opening the tank (9) in the pool; c. - dismantling and removing the control rods, leaving the control rods inserted in the core; d. - moving the basket containing the core between the bottom of the tank (9) and a reloading bench (32) in the pool (3) containing the tank (9).
  12. [Claim 12] Maintenance method according to claim 11, for which, the basket comprising said second perforated plate (70) and third perforated plate (73), the method comprises on the reloading bench (32) a removal of said second perforated plate (70) and third perforated plate (73) and a removal of the control rods from the basket before a removal of said fuel assemblies (600) and the replacement of said second perforated plate (70), third perforated plate (73) and the cross rods on the basket (601) after a replacement of said assemblies.
  13. [Claim 13] A maintenance method according to claim 11 or 12, wherein removal and replacement of said assemblies is carried out by means of a loading/unloading machine (43) positioned above the pool and adapted to carry out the removal of worn assemblies, the insertion of new assemblies into the core and the storage of the assemblies in racks (31) in the pool.

Description

Description Title: NUCLEAR REACTOR CORE ARRANGEMENT AND METHOD FOR HANDLING SAID ARRANGEMENT Technical field [0001] The present disclosure relates to the field of nuclear reactors and in particular low-power nuclear reactors intended for use as heat generators for heating networks. Previous technique [0002] The fight against global warming leads to reducing the carbon footprint of all energy sectors. Housing is one of these, and is still very dependent on fossil fuels today. Highly incentivizing public policies to move towards low-carbon solutions are being implemented throughout Europe. [0003] District heating, which is highly developed in northern and eastern Europe, is experiencing significant growth but remains highly dependent on fossil fuels, particularly gas and coal. The latter is a major contributor to pollution in highly urbanized areas. Solutions such as geothermal energy exist, but are difficult to deploy on a large scale. The main route being considered is the use of biomass, but this limited resource is coveted by several energy sectors, such as aeronautics, and will inevitably be subject to strong tensions on the prices of the combustible raw material. [0004] Nuclear energy, which a number of countries, including France, have chosen as a means of controlling their carbon emissions in electricity production, can be considered as a potential solution in the field of urban heating. [0005] According to the International Atomic Energy Agency, around forty nuclear reactors in the world currently cogenerate electricity and heat for housing. Many projects are currently under development to use the "fatal" heat from nuclear reactors in urban heating, particularly for the new generation of small reactors (SMR) currently in the pipeline. [0006] However, the coupling of constraints linked to electricity production and heat production does not facilitate the implementation of optimal dual solutions. [0007] Nuclear reactors purely dedicated to district heating have been developed in the past, but none have seen concrete implementation to date. [0008] For example, we can cite the Thermos reactor, from the French Atomic Energy Commission (CEA), designed during the 1970s. However, in addition to the problems of acceptance of this technology, the power of the reactor, 100 MW, proved to be oversized compared to the capacities of local heat networks and the economic relevance of such an achievement appeared unconvincing compared to the construction of a coal-fired power station. [0009] A small-sized reactor is also described in documents WO2022/106756 A1. [0010] The question of the safety of a reactor for district heating requires the management of emergency cooling situations in the event of a fault in the installation and in particular in the event of the shutdown of the cooling liquid circulation pumps of a secondary circuit. [0011] Document FR2 314 560 A1 describes a nuclear reactor for a district heating network comprising so-called shutter tubes replacing valves, the primary cooling circuit being constantly in open communication with a cooling basin via an exhaust port and an intake port in the boundary walls of the primary cooling circuit, the exhaust port at least being provided with a connection member provided for this purpose, in the form of a gas shutter tube. [0012] Document US 4,363,780 relates to a steam generating reactor which comprises valves allowing, in the event of overheating, the evacuation of steam and the entry of water from a pool into the container of the reactor core. Technical problem [0013] It is desirable to produce low-power reactors and therefore to improve their efficiency while producing a passive safety device suitable for cooling the core of the reactor in the event of failure of an active heat recovery circuit of said core. Disclosure of the invention [0014] In view of this situation, the present disclosure proposes several improvements for a nuclear reactor installation suitable for district heating. [0015] The present disclosure relates in particular to equipment designed so that the heat transfer fluid, for example consisting of water, contained in the pool can naturally cool the reactor without any intervention by an operator, a cooling solution making it possible to cover all its operating states, normal or accidental. This reactor will therefore not require any human intervention to guarantee safety for an extended period, typically at least one week, and does not use any electrical source to ensure cooling of the core. [0016] The present disclosure relates in particular to an arrangement of the core adapted to allow control of the reactivity of the core simply. [0017] More specifically, the present disclosure proposes a nuclear reactor core arrangement comprising a core, formed of fuel assemblies comprising fuel plates or rods arranged in the core parallel to a first direction constituting a vertical direction of introduction of the core into a cylindrical vessel wi