EP-4736190-A1 - A REACTOR CONSTRUCTION

EP4736190A1EP 4736190 A1EP4736190 A1EP 4736190A1EP-4736190-A1

Abstract

The present invention relates to a reactor construction (1) comprising an upper compartment (2) above a drain tank compartment (3), said upper compartment (2) comprising: a molten salt reactor (MSR) (4), comprising a reactor vessel (5) comprising a molten fuel salt (6); a molten salt drain system connected to the reactor vessel (5); said drain tank compartment (3) comprising: one or more drain tanks (10) in communication with the molten salt drain system; a buffer water tank (15) comprising an inner wall (16) and an outer wall (17) and buffer water (21) in the gap between the inner wall (16) and the outer wall (17) of the buffer water tank (15), said buffer water tank (15) surrounding the one or more drain tanks (10), wherein a first piping structure (22) is defining a circuit for at least part of the buffer water (21) and comprising a heat exchanger (23) in thermal contact with a reservoir water tank (30), said reservoir water tank (30) being at a level above the buffer water tank (15), said reservoir water being in thermal contact with an environment and/or a second piping structure (24) is defining a circuit for at least part of the buffer water (21) and comprising a heat exchanger (25) in thermal contact with an environment, said heat exchanger (25) being at a level above the buffer water tank (15) and/or a seawater heat exchanger (26) in thermal contact with the buffer water (21) and seawater, said seawater heat exchanger (26) being located below seawater level outside the outer wall (17) of the buffer water tank (15).

Inventors

YOON, Juhyeon
ESTEVEZ, Samanta
RUSCOE, Timothy
GARCIA, Matias
CIRERA, Bernat
CANDASSAMY, Vighnesh S.
JUHL, Andreas B.
WAGNER, Mads Kert

Assignees

Saltfoss Energy ApS

Dates

Publication Date: 20260506
Application Date: 20240701

Claims (1)

C L A I M S 1. A reactor construction (1) comprising an upper compartment (2) above a drain tank compartment (3), said upper compartment (2) comprising: - a molten salt reactor (MSR) (4), comprising a reactor vessel (5) comprising a molten fuel salt (6); - a molten salt drain system connected to the reactor vessel (5); said drain tank compartment (3) comprising: - one or more drain tanks (10) in communication with the molten salt drain system; - a buffer water tank (15) comprising an inner wall (16) and an outer wall (17) and buffer water (21) in the gap between the inner wall (16) and the outer wall (17) of the buffer water tank (15), said buffer water tank ( 15) surrounding the one or more drain tanks (10), wherein a first piping structure (22) is defining a circuit for at least part of the buffer water (21) and comprising a heat exchanger (23) in thermal contact with a reservoir water tank (30), said reservoir water tank (30) being at a level above the buffer water tank (15), said reservoir water being in thermal contact with an environment and/or a second piping structure (24) is defining a circuit for at least part of the buffer water (21) and comprising a heat exchanger (25) in thermal contact with an environment, said heat exchanger (25) being at a level above the buffer water tank (15) and/or a seawater heat exchanger (26) in thermal contact with the buffer water (21) and seawater, said seawater heat exchanger (26) being located below seawater level outside the outer wall (17) of the buffer water tank (15). 2. The reactor construction (1) according to claim 1, wherein the reactor construction (1) comprises an upper compartment (2) above a drain tank compartment (3), said upper compartment (2) comprising: - a molten salt reactor (MSR) (4), comprising a reactor vessel (5) comprising a molten fuel salt (6); - a molten salt drain system connected to the reactor vessel (5); said drain tank compartment (3) comprising: - one or more drain tanks (10) in communication with the molten salt drain system; - a buffer water tank (15) executed as a tube system comprising an inner tube (52) and an outer tube (51), wherein the inner and outer tube are conjoined, wherein the buffer water is located within the tube within the conjoined inner and outer tube of the tube system, said buffer water tank (15) surrounding the one or more drain tanks (10), wherein a first piping structure (22) is defining a circuit for at least part of the buffer water (21) and comprising a heat exchanger (23) in thermal contact with a reservoir water tank (30), said reservoir water tank (30) being at a level above the buffer water tank (15), said reservoir water being in thermal contact with an environment and/or a second piping structure (24) is defining a circuit for at least part of the buffer water (21) and comprising a heat exchanger (25) in thermal contact with an environment, said heat exchanger (25) being at a level above the buffer water tank (15) and/or a seawater heat exchanger (26) in thermal contact with the buffer water (21) and seawater, said seawater heat exchanger (26) being located below seawater level outside the outer wall (17) of the buffer water tank (15). 3. The reactor construction (1) according to claim 1 or 2, wherein the reactor construction (1) comprises an upper compartment (2) above a drain tank compartment (3), said upper compartment (2) comprising: - a molten salt reactor (MSR) (4), comprising a reactor vessel (5) comprising a molten fuel salt (6); - a molten salt drain system connected to the reactor vessel (5); said drain tank compartment (3) comprising: - one or more drain tanks (10) in communication with the molten salt drain system; - a buffer water tank (15) executed as a tube system comprising an inner tube (52) and an outer tube (51), wherein the inner (52) and outer (51) tube are conjoined, wherein the buffer water is located within the tube within conjoined inner and outer tube of the tube system, said buffer water tank (15) surrounding the one or more drain tanks (10), wherein the conjoined inner and outer tube of the tube system comprise a section in which the buffer water evaporates (57), a section in which the buffer water is adiabatic (56), and a section in which the buffer water condenses (55), wherein a first piping structure (22) is defining a circuit for at least part of the buffer water (21) and comprising a heat exchanger (23) in thermal contact with a reservoir water tank (30), said reservoir water tank (30) being at a level above the buffer water tank (15), said reservoir water being in thermal contact with an environment and/or a second piping structure (24) is defining a circuit for at least part of the buffer water (21) and comprising a heat exchanger (25) in thermal contact with an environment, said heat exchanger (25) being at a level above the buffer water tank (15) and/or a seawater heat exchanger (26) in thermal contact with the buffer water (21) and seawater, said seawater heat exchanger (26) being located below seawater level outside the outer wall (17) of the buffer water tank (15). 4. The reactor construction (1) according any one of the above claims, wherein the reactor construction (1) comprises an upper compartment (2) above a drain tank compartment (3), said upper compartment (2) comprising: - a molten salt reactor (MSR) (4), comprising a reactor vessel (5) comprising a molten fuel salt (6); - a molten salt drain system connected to the reactor vessel (5); said drain tank compartment (3) comprising: - one or more drain tanks (10) in communication with the molten salt drain system; - a buffer water tank (15) executed as a tube system comprising an inner tube (52) and an outer tube (51), wherein the inner (52) and outer (51) tube are conjoined, wherein the buffer water is located within the tube within conjoined inner and outer tube of the tube system, said buffer water tank (15) surrounding the one or more drain tanks (10), wherein the conjoined inner and outer tube of the tube system comprise a section in which the buffer water evaporates (57), a section in which the buffer water is adiabatic (56), and a section in which the buffer water condenses (55), wherein a seawater heat exchanger (26) in thermal contact with the buffer water (21) and seawater, said seawater heat exchanger (26) being located below seawater level outside the outer wall (17) of the buffer water tank (15) within a rectangular or cylindrical recess, preferably a sea chest (58). 5. The reactor construction (1) according any one of the above claims, wherein the reactor construction (1) comprises an upper compartment (2) above a drain tank compartment (3), said upper compartment (2) comprising: - a molten salt reactor (MSR) (4), comprising a reactor vessel (5) comprising a molten fuel salt (6); - a molten salt drain system connected to the reactor vessel (5); said drain tank compartment (3) comprising: - one or more drain tanks (10) in communication with the molten salt drain system; - a buffer water tank (15) comprising an inner wall (16) and an outer wall (17) and buffer water (21) in the gap between the inner wall (16) and the outer wall (17) of the buffer water tank (15), said buffer water tank (15) surrounding the one or more drain tanks (10), and a first piping structure (22) is defining a circuit for at least part of the buffer water (21) and comprising a heat exchanger (23) in thermal contact with a reservoir water tank (30), said reservoir water tank (30) being at a level above the buffer water tank (15), said reservoir water being in thermal contact with an environment; and optionally a second piping structure (24) is defining a circuit for at least part of the buffer water (21) and comprising a heat exchanger (25) in thermal contact with an environment, said heat exchanger (25) being at a level above the buffer water tank (15); and optionally a seawater heat exchanger (26) in thermal contact with the buffer water (21) and seawater, said seawater heat exchanger (26) being located below seawater level outside the outer wall (17) of the buffer water tank (15). 6. The reactor construction (1) according to any one of the above claims, wherein the first piping structure (22) comprises: - at least one rise-pipe (27) with a first end (28) being an inlet for at least part of the buffer water (21) and with a second end (29) in contact with an inlet for a heat exchanger (23) in the reservoir water tank (30); and - at least one fall-pipe (31) with a first end (32) in contact with an outlet of the heat exchanger (23) in the reservoir water tank (30) and with a second end (33) being an outlet for at least part of the buffer water (21). 7. The reactor construction (1) according to claim 6, wherein the minimum cross section of the first end (28) of rise-pipe is larger than the minimum cross section of the second end (33) of the fall-pipe. 8. The reactor construction (1) according to any one of the above claims, wherein a natural convection enhancer is comprised in the buffer water (21) in the buffer water tank (15), said natural convection enhancer comprising a tankwall (34) in the gap between the inner (16) and outer wall (17) dividing the buffer water tank (15) in an inner tank region (35) and an outer tank region (36), the tank-wall (34) extending above buffer water level into a dry wall section (37) contacting the outer wall (17) at a wall contact location (38), wherein - the dry wall section (37) and/or the inner wall (16) comprises perforations (39) to allow air circulation between the inner tank region (35) and the outer tank region (36), - the first end (28) of the rise-pipe being allocated above the wall contact location (38) and the second end (33) of the fall-pipe being allocated below the wall contact location (38). 9. The reactor construction (1) according to any one of the above claims, wherein the buffer tank inner wall (16) is connected to an inner bottom plate (18) so that inner wall (16) and the inner bottom plate (18) has a bowl shape. 10. The reactor construction (1) according to any one of the above claims, wherein the molten salt drain system is a molten fuel salt drain system and comprises a salt piping system comprising at least one salt plug (13). 11. The reactor construction (1) according to any one of the above claims, further comprising a gas supply system comprising - a carrier gas reservoir; - a carrier gas piping (12) comprising at least one valve (11, 110, 111, 112), said carrier gas piping (12) connecting from the carrier gas reservoir to the one or more drain tanks (10). 12. The reactor construction (1) according to any one of the above claims, wherein the molten fuel salt (6) having a composition selected from the group consisting of compositions comprising: sodium fluoride + potassium fluoride + uranium fluoride; lithium fluoride + thorium fluoride + plutonium fluoride; lithium fluoride + thorium fluoride + uranium fluoride; lithium fluoride + beryllium fluoride + uranium fluoride; lithium fluoride + beryllium fluoride + uranium fluoride + thorium fluoride; lithium fluoride + beryllium fluoride + uranium fluoride + thorium fluoride + zirconium fluoride; sodium fluoride + rubidium fluoride + uranium fluoride; sodium fluoride + beryllium fluoride + uranium fluoride + thorium fluoride + zirconium fluoride; potassium chloride + plutonium chloride + uranium chloride; sodium chloride + plutonium chloride; sodium chloride + plutonium chloride + uranium chloride. 13. The reactor construction according to any one of the above claims, wherein the MSR further comprises a moderator based on a material selected from the group of a graphite material, a Be compound containing material, a molten salt of a metal hydroxide wherein when the moderator is molten salt of a metal hydroxide, the reactor construction further comprises a molten salt of a metal hydroxide drain system including molten salt of a metal hydroxide drain tanks. 14. The reactor construction according to any one of the above claims, wherein the reactor construction comprises a compartment separator comprising: a grid structure forming a substantially horizontal surface separation between the upper compartment and the drain tank compartment, said grid structure comprising a metal grid and a thermally insulating layer and one or more funnels penetrating the grid structure, each funnels comprising a plug made of a sacrificial material. 15. The reactor construction according to any one of the above claims, wherein the MSR (4) is located on a marine structure, preferably a barge (40). 16. A method of transferring heat from a molten salt comprising the steps of - providing a molten fuel salt (6) in one or more drain tanks (10) for molten fuel salt (6); - surrounding the one or more drain tanks (10) for molten fuel salt (6) with a buffer water tank (15) comprising buffer water (21) in a gap between an inner wall (16) and an outer wall (17) of the buffer water tank (15), said molten fuel salt (6) transferring heat through at least one of heat radiation, heat conduction or heat convection with the inner wall (16) to heat the buffer water (21) into steam; - providing a first piping structure (22) comprising at least one rise-pipe (27) above at least part of the buffer water (21), said risepipe (27) collecting steam and directing the steam to a heat exchanger (23) in the reservoir water in a reservoir water tank (30) above the buffer water tank (15) to condense the steam into water; at least one fall-pipe (31) to direct water from the heat exchanger (23) in the reservoir water in the reservoir water tank (30) to the buffer water tank (15) and/or - providing a second piping structure (24) comprising at least one rise-pipe (27) above at least part of the buffer water (21), said risepipe (27) collecting steam and directing the steam to a gas heat exchanger (25) in thermal contact with an environment comprising gas, said gas heat exchanger (25) being above the buffer water tank (15) to condense the steam into water; at least one fall-pipe (31) to direct water from the gas heat exchanger (25) to the buffer water tank (15) and/or - providing a seawater heat exchanger (26) in thermal contact with the buffer water (21), said seawater heat exchanger (26) being located below seawater level outside the outer wall (17) of the buffer water tank (15), wherein buffer water (21) circulates through the seawater heat exchanger (26). 17. The method of transferring heat from a molten salt according to claim 16 furthermore comprising a transfer of heat from the reservoir water tank (30) to an environment, such as an outside environment in thermal contact with the reservoir water tank (30). 18. The method of transferring heat from a molten salt according to claim 17 where the transfer of heat from the reservoir water tank (30) is at least partly through the evaporation of the reservoir water to the outside environment. 19. The method of transferring heat from a molten salt according to any of claims 16 to 18, wherein the heat transfer is a passive heat transfer method. 20. The method of transferring heat from a molten salt according to any of claims 16 to 19 wherein a natural convection enhancer comprising a tank wall (34) in the gap between the inner (16) and outer wall (17) divides the buffer water tank (15) in an inner tank region (35) and an outer tank region (36) - causing the buffer water (21) in the inner tank region (35) to boil off, and - providing an upwards flow path for steam.

Description

A REACTOR CONSTRUCTION Field of the invention The present invention relates to a reactor construction for a small modular reactor (SMR) such as a molten salt reactor (MSR) where the reactor construction comprises a cooling system for the decay heat from the nuclear fission reaction. The reactor construction comprises a water tank for transferring heat to enable a fully passive decay heat removal system. The present invention furthermore relates to a method of transferring heat from a molten salt. Background of the Invention Molten salt reactors (MSRs) are based on a critical concentration of a fissile material dissolved in a molten salt. The molten salt comprising the fissile material is commonly referred to as the fuel salt or molten fuel salt. Research was conducted on MSRs initially at the Oak Ridge National Laboratory (ORNL) in the 1950's and 1960's but is yet to be successfully commercialised. MSRs have several advantages over other reactor types, including those being in commercial use nowadays. MSRs are capable of breeding fissile U-233 from thorium, of producing much lower levels of transuranic actinide waste than uranium/plutonium fueled reactors; capable of operating at high temperatures, capable of avoiding accumulation of volatile radioactive fission products in solid fuel rods and capable of combusting larger amounts of fissile material than is possible in conventional reactors. Other particular attractive features of an MSR are the operation at ambient or low pressure and the retention of the fission products as strongly bonded salts which are conventionally either fluoride salts or chloride salts. Much of the attention of the safety systems for nuclear reactors is focused on the removal of heat arising from the decay of the fission products especially if a breakdown occurs of the normally functioning cooling pumps of the nuclear plants sometimes described as a loss of cooling accident (LOCA). These occurrences can be the result of a loss of offsite power (LOOP) or for other reasons. Conventional light water reactors (LWRs) are of the Generation II type and a few are of the Generation III type. The Generation II and III types use active systems for cooling with residual heat removal heat exchangers. Advanced designs (Gen III and Gen III+) rely extensively on passive safety systems at least for a certain grace period to allow time for an active system to be up and running to remove the large amounts of decay heat for most prevailing nuclear power plants. Molten salt reactors (MSRs) are characterized as Gen IV designs along with other advanced small modular reactors (SMRs) such as high temperature gas cooled reactor (HTGR). These reactor types are expected to rely on passive and inherent safety features for an indefinite period of time. The reactor vessel auxiliary cooling system (RVACS) and the direct reactor auxiliary cooling system (DRACS) are examples of such relatively new safety systems. RVACS and DRACS are particularly suited as cooling systems for SMR's whereas these systems are less attractive for conventional nuclear reactors where the demand to heat removal may be an order of magnitude larger. ORNL-314 "MOLTEN-SALT REACTOR PROGRAM QUARTERLY PROGRESS REPORT" from 15 December 1960 discloses heat removal in relation to the operation of the original Molten Salt Reactor Experiment (MSRE). The document discloses that the heat is removed from molten fuel salt after the molten fuel salt has been drained into several drain tanks. It is described that in order to make the heat removal as nearly uniform as possible throughout the tank, forty immersed bayonet coolers are used, with boiling water as coolant. Water-cooling was selected above gas, molten salt, or NaK because of its simplicity and relative independence from utilities failures. However, the immersion of water contained in bayonets directly into the molten fuel salt imposes a risk in case of a breach of the bayonet material, typically a metal alloy accompanied by a contact between the molten fuel salt and water leading to sudden burst of high-temperature steam. KR20090021722 discloses a cooling system for removing decay heat from a high temperature gas cooled reactor (HTGR). The system is aimed at minimizing the parasitic heat loss during normal operation. The decay heat from the reactor core is transferred to a piping system for water where the water pipe is air cooled. The water piping is in thermal contact with a water reservoir via a water bath heat exchanger and the water is actively pumped through the water piping. A passive air-cooling system is used as the main cooling system and only the air- cooling device is used during normal operation and the water-cooling part of the system is used in the event of an accident. Though a large capacity of passive cooling can be obtained in the event of an accident with a nuclear reactor, especially a high-temperature gas reactor, the system also relies on active cooling to minimize para