The present invention relates to a cooling system (1) for evacuation of decay heat of irradiated fuel elements of a nuclear reactor. The system (1) substantially consists of heat conductive elements (4), preferably shaped as plates, of high conductivity material and of a handling device (51) to move the elements (4) with respect to the fuel element (3) to be cooled, which is of the type formed by a plurality of elementary structures (7) made of fuel material one beside the other, for instance bars. Each element (4) has a first portion (4a), which in use may be inserted into the fuel element between the elementary structure to receive heat therefrom and transfer heat by conduction to a second portion (4b), which in use remains outside the fuel element and is cooled by a cooling gas.
The present invention relates to a nuclear reactor (1), in particular a pool -type nuclear reactor cooled with liquid metal (for example, a heavy metal such as lead or lead-bismuth eutectic) or with sodium or molten salts, having a core (4) formed by a bundle of fuel elements (12) and immersed in a primary fluid (F) circulating between the core and at least one heat exchanger (10); the fuel elements (12) extend along respective parallel longitudinal axes (A) and have respective bottom active parts (13) immersed in the primary fluid to constitute the core, and respective service parts (14) that extend at the top from the active parts and emerge from the primary fluid; the fuel elements (12) are mechanically supported via respective top end heads (32) anchored to supporting structures (120) and can be operated via handling machines.
A nuclear reactor (1), in particular a liquid-metal-cooled reactor, is provided with at least one compact primary heat exchanger (11), in particular a steam generator, which has a plurality of heat-exchange tubes (27) having respective spiral portions (37) set in levels on top of one another to form an annular tube bundle (40) delimiting a substantially cylindrical internal central zone (17), which houses, at the bottom, a circulation pump (10) and is pre-arranged for supply from below with primary fluid (liquid metal), which then traverses the tube bundle radially.
G21C 1/02 - Fast fission reactors, i.e. reactors not using a moderator
G21C 1/32 - Integral reactors, i.e. reactors wherein parts functionally associated with the reactor but not essential to the reaction, e.g. heat exchangers, are disposed inside the enclosure with the core
F22B 1/02 - Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
F22B 1/06 - Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being moltenUse of molten metal, e.g. zinc, as heat transfer medium
F22B 1/16 - Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being hot liquid or hot vapour, e.g. waste liquid, waste vapour
F28D 7/04 - Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being spirally coiled
4.
HEAT EXCHANGER, IN PARTICULAR OPERATING AS LARGE- SIZED STEAM GENERATOR
The present invention relates to a heat exchanger (1), in particular a large-sized steam generator, having a conveying structure (11) for conveying a first process fluid (F1) and a plurality of heat-exchange tubes (12), in which a second process fluid (F2) circulates; the tubes (12) have respective substantially plane spiral portions (13) set on top of one another in a number of levels to form a substantially annular tube bundle (14). The tube bundle (14) delimits, inside, a substantially cylindrical central space (29) and, outside and together with a casing (2) housing the tube bundle (14), an annular space (30). The internal central space (29) and the annular space (30) constitute respective ducts for passage of the first process fluid (F1) that traverses the tube bundle (14) radially, whilst the second process fluid (F2) circulates within the spiral portions (13) with a radial component of the velocity locally opposite to that of the first process fluid (F1).
F22B 21/28 - Water-tube boilers of vertical or steeply-inclined type, i.e. the water-tube sets being arranged vertically or substantially vertically built-up from water tubes of form other than straight or substantially straight bent spirally
F22B 27/10 - Instantaneous or flash steam boilers built-up from water tubes bent spirally
F24H 1/16 - Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium in which the water is kept separate from the heating medium by tubes, e.g. bent in serpentine form helically or spirally coiled
F28D 1/047 - Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with the heat-exchange conduits immersed in the body of fluid with tubular conduits the conduits being bent, e.g. in a serpentine or zig-zag
F28D 7/04 - Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being spirally coiled
5.
PRESSURIZED -WATER- COOLED NUCLEAR REACTOR WITH COMPACT STEAM GENERATORS
A nuclear reactor (1) cooled with pressurized water, having a pressurized tank (2) installed in which are compact steam generators (11); each steam generator (11) comprises a plurality of heat-exchange tubes (21) having respective spiral portions (37) set in levels on top of one another to form at least one annular tube bundle (20) delimiting a substantially cylindrical internal central zone (22), pre-arranged for supply from above with primary water, which then traverses the tube bundle radially.
G21C 1/32 - Integral reactors, i.e. reactors wherein parts functionally associated with the reactor but not essential to the reaction, e.g. heat exchangers, are disposed inside the enclosure with the core
F28D 7/04 - Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being spirally coiled
F22B 1/16 - Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being hot liquid or hot vapour, e.g. waste liquid, waste vapour
6.
SYSTEM FOR EVACUATING THE RESIDUAL HEAT FROM A LIQUID METAL OR MOLTEN SALTS COOLED NUCLEAR REACTOR
A system (7) for evacuating the residual heat from a nuclear reactor (1) cooled with liquid metal or molten salts has two types of heat exchangers (8) immersed in the primary fluid (5) of the reactor (1) : heat exchangers (8a) with higher power density, which use boiling water as secondary cooling fluid (9) and are particularly suitable for evacuating the residual heat in the first days after turning-off of the reactor; and heat exchangers (8b) operating with atmospheric air or with water and suitable for evacuating the residual heat for indefinite periods of time. Both types of heat exchangers present a bundle of heat -exchange elements (35), shaped in such a way that the secondary fluid (9) circulating in each element (35) is separated from the primary fluid (5) of the reactor (1) by a double wall (40, 41) of the element (35), which delimits a gap (42) introduced in which is a pressurized inert gas having the function of continuous monitoring of the integrity of the heat exchanger (8) and of thermal resistance calibrated for preventing solidification of the primary fluid (5) of the reactor (1) in the heat exchanger (8).
The invention relates to a system (1) for evacuating the residual heat from a nuclear reactor (2), wherein the residual heat is evacuated by irradiation from the main tank (3) of the nuclear reactor towards a ring of substantially U-shaped tubes (15), inside which external air circulates in natural circulation and which are arranged circumferentially around the tank (3). The tubes (15) are grouped together in modules (11), each of which is made up of a set of U-shaped tubes (15) inserted inside one another with respective side-by-side branches (16) facing the tank (3) and arranged on opposite sides of a common central axis (X) and laterally separated from one another by empty spaces. A radiant heat reflecting wall (30), which also constitutes a structure (33) for containing an insulation filling (34) of the nuclear-reactor well (5), is set behind the tubes (15) with respect to the tank (3) to reflect back onto the tubes (15) the radiant heat passing through the empty spaces between one tube (15) and another. The reflecting wall (30) is shaped in such a way as to be partially inserted between the branches (16) of the tubes (15) to define a longitudinal channel (31) set substantially around each branch (16).
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