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EP-4736192-A1 - SAFETY SYSTEM FOR NUCLEAR FACILITY, AND METHOD FOR MAKING SUCH A FACILITY SAFE

EP4736192A1EP 4736192 A1EP4736192 A1EP 4736192A1EP-4736192-A1

Abstract

The invention relates to a safety system for a nuclear facility, comprising a reactor hall (4) provided with a nuclear reactor (1) in a cooling pool (3) of said reactor, characterised in that it comprises a ventilation system, for adjusting the ambient conditions of technical rooms and of the reactor hall and for filtration to protect the environment from gaseous radioactive waste. The system is provided with: a. at least one air inlet (201a) having a variable cross-section in a wall of a building (10), the air inlet opening into an intake treatment room (201) provided with a first air outlet (201b) into the reactor hall; b. a water/air exchanger (5) in the pool, comprising an inlet duct (5a) open in the reactor hall (4); c. an air outlet duct (5b) of the exchanger (5), the duct being suitable for supplying the air leaving the water/air exchanger to an outlet filtration device (203) in communication with a flue (210); d. at least one extractor (202) arranged at the outlet of the air outlet duct (5b) in a room comprising the outlet filtration device (203), and for which, when the extractor is at a standstill, the water/air exchanger and the cross-section of the at least one air inlet (201a) are configured so that, when the reactor is at a standstill, the rise in the temperature of the water in the pool heats the air in the exchanger relative to the outside temperature at the flue outlet and creates an air flow that sucks the outside air at the air inlet in order to eject it at the outlet of the flue through the filtration device (203).

Inventors

  • VALLEE, ALAIN

Assignees

  • CALOGENA

Dates

Publication Date
20260506
Application Date
20240620

Claims (11)

  1. [Claim 1] Safety system for a nuclear installation, comprising a reactor hall (4) provided with a nuclear reactor (1) in a pool (3) for cooling said reactor, characterized in that it comprises a ventilation system, for adjusting the ambient conditions of technical rooms and the reactor hall and for filtration for protecting the environment from gaseous radioactive discharges provided with: a. at least one air inlet (201 a) with variable section in a wall of a building (10), said air inlet opening into an inlet treatment room (201) provided with a first air outlet (201 b) in the reactor hall, b. a water/air exchanger (5) in the pool comprising an inlet duct (5a) open in the reactor hall (4), c. of an air outlet duct (5b) from said exchanger (5), said duct being adapted to bring the air leaving said water/air exchanger to an outlet filtration device (203) in communication with a chimney (210), d. of at least one extractor (202) arranged at the outlet of the air outlet duct (5b) in a room comprising said outlet filtration device (203), e. and for which, with the extractor stopped, said water/air exchanger and the section of said at least one air inlet (201 a) are configured so that, with the reactor stopped, the increase in the temperature of the pool water heats the air in said exchanger relative to the outside temperature at the chimney outlet and creates an air flow sucking in the outside air at said air inlet to spit it out at the chimney outlet through said filtration device (203).
  2. [Claim 2] Security system according to claim 1 for which said at least one air inlet (201 a) comprises a diaphragm or a flap comprising a fully open position of said air inlet and a partially closed position of said air inlet (201 a).
  3. [Claim 3] A safety system according to claim 2 wherein said fully open position of said air inlet is maintained by a force electromagnetic and the partially closed position of said air inlet (201 a) is obtained in the absence of said electromagnetic force.
  4. [Claim 4] A security system according to claim 3 wherein said electromagnetic force is generated by an electrical device powered in parallel with the electrical supply of said extractor (202).
  5. [Claim 5] Safety system according to any one of the preceding claims, for which said air flow maintains the reactor hall (4) under vacuum, with the extractor stopped.
  6. [Claim 6] A safety system according to any preceding claim, wherein the input processing room (201) is provided with a second air outlet (201c) to an auxiliary systems room (12) and/or a heat transfer room (13) and/or a loading/unloading hall (14) forming part of the technical rooms and each provided with a third air outlet to the reactor hall (4).
  7. [Claim 7] Security system according to claim 6, for which at least one of the rooms of the auxiliary systems (12), heat transfer room (13) and loading/unloading hall (14) is maintained under vacuum.
  8. [Claim 8] A safety system according to any preceding claim comprising one or more filters (203) upstream of said chimney (210) and downstream of said extractor (202).
  9. [Claim 9] A method of securing a nuclear installation provided with a safety system according to any one of the preceding claims, for which: a. in normal operation, the variable section of said air inlet (201 a) in the wall of the building (10) is configured in the maximum opening position and said extractor (202) sucks air from the reactor hall (4) putting the reactor hall under vacuum and, b. during a loss of electrical power supply to the installation, a reactor shutdown sequence is initiated, the variable section of said air inlet (201 a) in the wall of the building (10) is configured in the reduced opening position and the water/air exchanger produces a convection current sucking air from the reactor hall to evacuate it into the chimney (210).
  10. [Claim 10] Method according to claim 9, for which a loss of electrical power supply to the systems of the nuclear installation further activates a passive fluid circuit for cooling the reactor via the pool so as to put the reactor into self-sufficient operation for a period compatible with the restarting of said electrical power supply.
  11. [Claim 11] Nuclear installation comprising a security system according to any one of claims 1 to 8.

Description

Description Title: SECURITY SYSTEM OF A NUCLEAR INSTALLATION AND METHOD FOR MAKING SUCH AN INSTALLATION SAFE 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 a security system for a nuclear installation and a method for securing such an installation. [0017] More particularly, the present disclosure proposes a safety system for a nuclear installation, comprising a reactor hall provided with a nuclear reactor in a cooling pool of said reactor which comprises a ventilation system, for adjusting the ambient conditions of technical rooms and