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EP-4736188-A1 - NUCLEAR REACTOR HAVING A CONVECTIVE EXCHANGER

EP4736188A1EP 4736188 A1EP4736188 A1EP 4736188A1EP-4736188-A1

Abstract

The invention relates to a nuclear reactor provided with a nuclear core (6), arranged on a support (6a) in a bottom of a cylindrical vessel (9) oriented along a vertical axis, filled with a heat-transfer liquid, in particular water, under an upper dome of the vessel, comprising an annular primary exchanger (91) surrounding a flue (9a) for installing and extracting the core, the exchanger starting above the core, extending along the cylindrical wall of the vessel under the dome, and comprising a primary circuit consisting of the heat-transfer liquid circulating in the core and in the primary exchanger by convection, for which a first part of the cylindrical wall (94) of the vessel (9) is surrounded by a first annular casing (1a) forming a cold plenum (83) in communication with an inlet (91a) of a secondary circuit of the exchanger (91) in the lower part of the exchanger and extending from the bottom of the vessel to below an outlet (91b) of the primary exchanger. A second part of the cylindrical wall is surrounded by a second annular casing (1b), above the first annular casing (1a), forming a hot plenum in communication with the outlet (91b) of the secondary circuit of the exchanger (91) in the upper part of the exchanger, an intermediate heat extraction circuit comprising a first pipe (81), for the inflow of cold heat-transfer liquid, opening out in the upper part of the first casing (1a), while a second starting pipe for hot heat-transfer liquid exits in the upper part of the second casing (1b).

Inventors

  • VALLEE, ALAIN

Assignees

  • CALOGENA

Dates

Publication Date
20260506
Application Date
20240620

Claims (10)

  1. [Claim 1] Nuclear reactor provided with a nuclear core (6), arranged on a support (6a) in a bottom of a cylindrical vessel (9) oriented along a vertical axis, filled with a heat transfer fluid, in particular water, under an upper dome of the vessel, comprising an annular primary exchanger (91) surrounding a chimney (9a) for installing and extracting said core, said exchanger starting above said core, extending along the cylindrical wall of the vessel under said dome, and comprising a primary circuit constituted by the heat transfer fluid circulating in the core and in said primary exchanger by convection, characterized in that a first part of the cylindrical wall (94) of said vessel (9) is surrounded by a first annular casing (1a) forming a cold plenum (83) placed in communication with an inlet (91a) of a secondary circuit of said exchanger (91) in the lower part of said exchanger and extending from the bottom of the vessel up to under an outlet (91 b) of the primary exchanger, in that a second part of said cylindrical wall is surrounded by a second annular casing (1 b), above said first annular casing (1 a), forming a hot plenum placed in communication with the outlet (91 b) of said secondary circuit of said exchanger (91) in the upper part of said exchanger, an intermediate heat extraction circuit comprising a first pipe (81), for the arrival of cold heat transfer liquid, opening into the upper part of said first casing (1 a) while a second pipe (82), for the departure of hot heat transfer liquid exits in the upper part of said second casing (1 b).
  2. [Claim 2] Nuclear reactor according to claim 1 for which the upper dome of the vessel is filled with a chemically neutral gas (93) for regulating pressure in the vessel.
  3. [Claim 3] Nuclear installation comprising a reactor according to claim 1 or 2 for which the tank is arranged in a well (2) formed in the bottom of a pool (3) filled with the same heat transfer liquid as the intermediate circuit, said first envelope and said second envelope being surrounded by the heat transfer liquid contained in the pool.
  4. [Claim 4] Nuclear installation according to claim 3 for which the first casing (1a) comprises a first opening (83a) for placing said cold plenum (83) in the first casing (1a) in communication with the pool (3), said first opening (83a) being kept closed by a first gravity valve (85) pushed back under the action of a first flow of said heat transfer fluid (F1) between the first pipe (81), for the arrival of cold heat transfer fluid from an intermediate circuit (8) and the second pipe (82) for the departure of hot heat transfer fluid from said intermediate circuit, said first opening opening under the action of the first gravity valve in the absence of said first flow (F1) so as to allow heat transfer fluid to pass between the first casing and the pool (3).
  5. [Claim 5] Nuclear installation according to claim 4 for which said first gravity valve comprises a mass (86) calibrated according to said first flow (F1) to close the first opening from a given first flow value (F1).
  6. [Claim 6] Nuclear installation according to claim 4 or 5 for which the second casing (1 b) comprises a second opening (84a) for placing said hot plenum in communication with the pool, said second opening being kept closed by a second gravity valve (87) in the presence of said first flow (F1) emerging from the reactor via said second pipe (82), said second opening opening under the action of the second gravity valve in the absence of said first flow (F1) so as to allow heat transfer liquid to pass between the second casing (1 b) and the pool (3).
  7. [Claim 7] Nuclear installation according to claim 6 for which said second gravity valve comprises a mass (88) calibrated according to said first flow (F1) to close the second opening from a given first flow value (F1).
  8. [Claim 8] Nuclear installation according to any one of claims 3 to 7 for which the volume of the pool (3) is sized so as to guarantee passive cooling of a residual power of the core (6) in the absence other means of cooling and maintaining the heat transfer fluid in the primary circuit below a fixed temperature for a specified period.
  9. [Claim 9] Nuclear installation according to any one of the preceding claims, for which the first pipe (81) and the second pipe (82) are part of the intermediate circuit (8) comprising an intermediate exchanger (100) and at least one pump (101).
  10. [Claim 10] Nuclear installation according to claim 9 for which said intermediate exchanger distributes the heat from the intermediate circuit to a primary distribution network (105) of urban heating supplying first buildings (106) and substations (110, 120) supplying heat to second buildings (107, 108, 109).

Description

Description Title: NUCLEAR REACTOR WITH CONVECTIVE EXCHANGER 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, about forty nuclear reactors in the world currently cogenerate electricity and heat for housing. Many projects are currently in 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 a reactor comprising a convective exchanger in the reactor vessel for transmitting heat to an improved intermediate circuit and comprising 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 invention relates in particular to a nuclear reactor comprising a vessel provided with a nuclear core and a primary convective exchanger for transferring heat to an intermediate circuit comprising at least one annular envelope around a portion of the cylindrical wall of the vessel. [0017] More specifically, the present disclosure p