A rupture disc for a device for protecting against overpressures inside an apparatus, the disc is made of a generally circular part including two planar surfaces substantially parallel to one another, and two notches each located along a circumference, the circumferences of the two notches being different from one another, the notch located on the larger circumference being made on one of the planar surfaces, referred to as lower surface, while the notch located on the smaller circumference is made on the other one of the planar surfaces, referred to as upper surface.

[Objective] An object is to provide a reactor which can cope with a core meltdown accident; i.e., can keep the soundness of a reactor pressure vessel and a reactor containment vessel and prevent release of radioactive substances to the outside even when a core meltdown accident occurs.

[Means for solution] A reactor 1 includes water-injection-to-core interruption means, provided for a possible core meltdown accident, for stopping injection of water into a core after occurrence of a zirconium-water reaction or film boiling in the core is detected on the basis of core pressure or the like. In order to remove core decay heat by natural cooling or water-cooling of the outer surface of a reactor pressure vessel 3 or the outer surface of a heat insulation 4 after injection of water into the core is stopped at the time of a core meltdown accident, the reactor 1 includes melting point restriction management means for managing a melting point restriction in material selection at the time of manufacture of the heat insulation 4 so that the heat insulation 4 melts and breaks without fail at the time of the core meltdown accident, or water injection means for injecting water into the space between the heat insulation 4 and a shield concrete 13.

[Objective] An object is to provide a reactor which can cope with a core meltdown accident; i.e., can keep the soundness of a reactor pressure vessel and a reactor containment vessel and prevent release of radioactive substances to the outside even when a core meltdown accident occurs.

[Means for solution] A reactor 1 includes water-injection-to-core interruption means, provided for a possible core meltdown accident, for stopping injection of water into a core after occurrence of a zirconium-water reaction or film boiling in the core is detected on the basis of core pressure or the like. In order to remove core decay heat by natural cooling or water-cooling of the outer surface of a reactor pressure vessel 3 or the outer surface of a heat insulation 4 after injection of water into the core is stopped at the time of a core meltdown accident, the reactor 1 includes melting point restriction management means for managing a melting point restriction in material selection at the time of manufacture of the heat insulation 4 so that the heat insulation 4 melts and breaks without fail at the time of the core meltdown accident, or water injection means for injecting water into the space between the heat insulation 4 and a shield concrete 13.

Simplified nuclear reactors include depressurization systems or gravity-driven injection systems or both. The systems depressurize and cool the reactor without operator intervention and power. An underground containment building may be used with the depressurization and injection systems passing through the same from above ground. Depressurization systems may use a rupture disk, relief line, pool, and filter to open the reactor and carry coolant away for condensation and exhausting. Injection systems may use a coolant tank above the nuclear reactor to inject liquid coolant by gravity into the reactor through an injection line and valve. The rupture disk and valve may be integral with the reactor and use penetration seals where systems pass through containment. Rupture disks and valves can actuate passively, at a pressure setpoint or other condition, through fluidic controls, setpoint failure, etc. The depressurization system and injection system together feed-and-bleed coolant through the reactor.

Simplified nuclear reactors include depressurization systems or gravity-driven injection systems or both. The systems depressurize and cool the reactor without operator intervention and power. An underground containment building may be used with the depressurization and injection systems passing through the same from above ground. Depressurization systems may use a rupture disk, relief line, pool, and filter to open the reactor and carry coolant away for condensation and exhausting. Injection systems may use a coolant tank above the nuclear reactor to inject liquid coolant by gravity into the reactor through an injection line and valve. The rupture disk and valve may be integral with the reactor and use penetration seals where systems pass through containment. Rupture disks and valves can actuate passively, at a pressure setpoint or other condition, through fluidic controls, setpoint failure, etc. The depressurization system and injection system together feed-and-bleed coolant through the reactor.

Safety valves accurately control closure and opening of fluid passage through the valve. Valves include a barrier that blocks the fluid until removal only by a high-energy projectile. Following removal and opening, the barrier or the projectile can flow through the valve, which remains open. Bullets, pneumatic pistons, shot, coilgun pellets and any other forceful projectile may impact and remove the barrier. The projectile is actuated with any type of chemical reaction, firing pin, spring release, accelerating circuit, ignition circuit. Catchers in the valve envelop or otherwise retain the projectile or barrier pieces and enter the fluid flow of the opened valve without blocking it. Disruptable barriers include strong but breakable glass plates, thin steel sheets, a rotatable door and other barriers that can withstand potentially over 10,000 psi of fluid pressure while closing the valve. Valves can use circuits to both monitor valve open/closed status and initiate firing the projectile.

Safety valves accurately control closure and opening of fluid passage through the valve. Valves include a barrier that blocks the fluid until removal only by a high-energy projectile. Following removal and opening, the barrier or the projectile can flow through the valve, which remains open. Bullets, pneumatic pistons, shot, coilgun pellets and any other forceful projectile may impact and remove the barrier. The projectile is actuated with any type of chemical reaction, firing pin, spring release, accelerating circuit, ignition circuit. Catchers in the valve envelop or otherwise retain the projectile or barrier pieces and enter the fluid flow of the opened valve without blocking it. Disruptable barriers include strong but breakable glass plates, thin steel sheets, a rotatable door and other barriers that can withstand potentially over 10,000 psi of fluid pressure while closing the valve. Valves can use circuits to both monitor valve open/closed status and initiate firing the projectile.

An emergency core cooling system removes decay heat generated by a reactor core of a reactor system. A reactor vessel uses water as a coolant. A containment structure surrounds the reactor system. A reactor cavity surrounds the reactor vessel. A first cavity pipe extends into the reactor vessel and provides a recirculation loop of cooling water by discharging vapor generated in the reactor vessel and supplying condensed water collected in the reactor cavity in an opposite direction.

A pyrotechnic-actuated valve assembly may include an insert body having an inlet, an outlet, and a flow path extending from the inlet to the outlet. The insert body is formed of a first alloy. A shear structure is bonded to the outlet of the insert body so as to close the flow path. The shear structure is formed of a second alloy. The second alloy of the shear structure is bonded to the first alloy of the insert body so as to form a hermetic seal. The dual-alloy nature of the valve assembly allows a relatively clean shearing of the shear structure during actuation, thus reducing or preventing the occurrence of deformation and/or material fragments in the flow path.

A pyrotechnic-actuated valve assembly may include an insert body having an inlet, an outlet, and a flow path extending from the inlet to the outlet. The insert body is formed of a first alloy. A shear structure is bonded to the outlet of the insert body so as to close the flow path. The shear structure is formed of a second alloy. The second alloy of the shear structure is bonded to the first alloy of the insert body so as to form a hermetic seal. The dual-alloy nature of the valve assembly allows a relatively clean shearing of the shear structure during actuation, thus reducing or preventing the occurrence of deformation and/or material fragments in the flow path.