Patent Number: 
Section: claims

1. A separate type safety injection system, comprising:a coolant injection unit connected to a reactor coolant system by a safety injection pipe such that coolant stored therein is injected into the reactor coolant system by a pressure difference when a loss-of-coolant-accident (LOCA) occurs;a gas injection unit disposed at a position higher than the coolant injection unit, and configured to pressurize the coolant injected into the reactor coolant system, by introducing gas stored therein to an upper part of the coolant injection unit in the loss-of-coolant-accident;a connection pipe configured to connect the upper part of the coolant injection unit and a lower part of the gas injection unit such that gas within the gas injection unit is introduced to the upper part of the coolant injection unit; andan orifice formed on an inner side of the connection pipe to contract a flow cross-sectional area of the gas introduced to the coolant injection unit, the orifice being configured to allow increases of a flow velocity and a flow rate of gas introduced to the coolant injection unit when a pressure difference between the coolant injection unit and the gas injection unit increases to a critical value and configured to passively limit the flow velocity and the flow rate of the gas introduced to the coolant injection unit as a critical flow velocity and a critical flow rate by forming choked flow when the pressure difference between the coolant injection unit and the gas injection unit is more than the critical value. 2. The separate type safety injection system of claim 1, wherein the coolant injection unit is provided with a coolant tank for storing the coolant therein,wherein the gas injection unit is provided with a gas tank for storing the gas therein, andwherein the coolant tank and the gas tank are connected to each other by the connection pipe. 3. The separate type safety injection system of claim 2, further comprising a throttle member installed at the safety injection pipe such that a flow rate of the coolant injected into the reactor coolant system is restricted, and configured to contract a flow cross-sectional area of the safety injection pipe. 4. The separate type safety injection system of claim 2, further comprising a check valve installed at the safety injection pipe such that the coolant inside the reactor coolant system is prevented from back-flowing and leaking into the separate type safety injection system. 5. The separate type safety injection system of claim 2, wherein at least part of the orifice protrudes from an inner side wall of the pipe line formed by the connection pipe or the partition wall. 6. An integral type reactor comprising:a core makeup tank configured to inject coolant into a reactor coolant system using a gravity force and pressure balance when an accident occurs on the reactor, by reaching a pressure equilibrium state with the reactor coolant system; anda separate type safety injection system connected to the reactor coolant system, and configured to inject coolant stored therein into the reactor coolant system when a loss-of-coolant-accident (LOCA) occurs,wherein the separate type safety injection system comprises:a coolant injection unit connected to a reactor coolant system by a safety injection pipe such that coolant stored therein is injected into the reactor coolant system by a pressure when the loss-of-coolant-accident occurs;a gas injection unit disposed at a position higher than the coolant injection unit, and configured to pressurize the coolant injected into the reactor coolant system, by introducing gas stored therein to an upper part of the coolant injection unit in the loss-of-coolant-accident;a connection pipe configured to connect the upper part of the coolant injection unit and a lower part of the gas injection unit such that gas within the gas injection unit is introduced to the upper part of the coolant injection unit; andan orifice formed on an inner side of the connection pipe to contract a flow cross-sectional area of the gas introduced to the coolant injection unit, the orifice being configured to allow increases of a flow velocity and a flow rate of gas introduced to the coolant injection unit when a pressure difference between the coolant injection unit and the gas injection unit increases to a critical value and configured to passively limit the flow velocity and the flow rate of the gas introduced to the coolant injection unit as a critical flow velocity and a critical flow rate by forming choked flow when the pressure difference between the coolant injection unit and the gas injection unit is more than the critical value. 7. The integral type reactor of claim 6, wherein the coolant injection unit is provided with a coolant tank for storing the coolant therein, andwherein the gas injection unit is provided with a gas tank for storing the gas therein,wherein the coolant tank and the gas tank are connected to each other by the connection pipe. 8. The integral type reactor of claim 7, further comprising a throttle member installed at the safety injection pipe such that a flow rate of the coolant injected into the reactor coolant system is restricted, and configured to contract a flow cross-sectional area of the safety injection pipe. 9. The integral type reactor of claim 7, further comprising a check valve installed at the safety injection pipe such that the coolant inside the reactor coolant system is prevented from back-flowing and leaking into the separate type safety injection system. 10. The integral type reactor of claim 7, wherein at least part of the orifice protrudes from an inner side wall of the pipe line formed by the connection pipe or the partition wall. 11. The integral type reactor of claim 6, further comprising an isolation valve installed at a pipe which connects a lower end of the core makeup tank with the reactor coolant system, and configured to be open by an actuation signal generated when a related accident occurs, such that the coolant is injected into the reactor coolant system from the core makeup tank. 12. The integral type reactor of claim 6, further comprising a pressure balancing pipe having one end connected to the reactor coolant system and another end connected to the core makeup tank, such that a pressure balance is formed at the core makeup tank. 13. The integral type reactor of claim 6, further comprising a passive residual heat removal system configured to remove heat of the core by circulating a fluid stored therein to a steam generator inside the reactor coolant system, when an accident occurs on the reactor. 14. The integral type reactor of claim 13, further comprising an isolation valve installed at a pipe which connects the passive residual heat removal system with the reactor coolant system, and configured to be open by an actuation signal.