CN-116134551-B - Nuclear power station

Abstract

A nuclear power plant has a nuclear reactor that includes a reactor pressure vessel containing a plurality of fuel rods containing fissile material. The nuclear power plant also has means for submerging the reactor pressure vessel in water, thereby water cooling the reactor pressure vessel in the event of an emergency in which cooling of the nuclear reactor is required. The nuclear power plant also has a primary core catcher located outside the reactor pressure vessel, the primary core catcher being made of a material adapted to hold molten core melt in the event that the core melt escapes the reactor pressure vessel. The nuclear power plant also has a secondary core catcher external to the primary core catcher, which is lined with a tank that is filled with water during normal use of the nuclear power plant to submerge the primary core catcher and thereby water cool the primary core catcher. The secondary core catcher is also made of a material suitable for retaining molten melt in the event that the melt escapes the first core catcher.

Inventors

• KNIGHT ADRIAN

Assignees

• 劳斯莱斯SMR有限公司

Dates

Publication Date

20260508

Application Date

20210714

Priority Date

20200716

Claims (8)

1. 1. A nuclear power plant (10) having: a nuclear reactor comprising a reactor pressure vessel (12) containing a plurality of fuel rods containing fissile material; means for water cooling the outside of the reactor pressure vessel (12) in the event of an emergency in which cooling of the nuclear reactor is required, the means for water cooling the outside of the reactor pressure vessel comprising means for immersing the reactor pressure vessel in water; A primary core catcher (32) external to the reactor pressure vessel (12), the primary core catcher formed of a material adapted to retain molten core melt in the event that core melt escapes the reactor pressure vessel, and A secondary core catcher (38) external to the primary core catcher, the secondary core catcher lining a tank (36), the tank (36) being filled with water in normal use of the nuclear power plant to submerge the primary core catcher and thereby water cool the primary core catcher, the secondary core catcher being formed of a material adapted to retain molten core melt in the event that core melt escapes the primary core catcher (32); Wherein the means for submerging the reactor pressure vessel (12) in water comprises a water retaining jacket (24) located outside the reactor pressure vessel, the jacket being spaced from the reactor pressure vessel such that in an emergency the cavity between the jacket and the reactor pressure vessel can be filled with water to submerge the reactor pressure vessel, thereby water cooling the reactor pressure vessel, wherein the water retaining jacket (24) acts as a heat shield to retain heat in the reactor during normal operation of the nuclear reactor, the cavity between the jacket and the reactor pressure vessel (12) being an air cavity during such normal operation.
2. 2. The nuclear power plant of claim 1 wherein the means for water cooling the exterior of the reactor pressure vessel (12) includes a supply system for supplying water to submerge the reactor pressure vessel in an emergency.
3. 3. The nuclear power plant of claim 1 further having one or more heat exchangers (28), the heat exchangers (28) being arranged to condense steam formed by boiling water that submerges the reactor pressure vessel.
4. 4. The nuclear power plant of claim 1 wherein the primary core catcher (32) is a metal core catcher.
5. 5. The nuclear power plant of claim 1 wherein the secondary core catcher (38) is a ceramic core catcher.
6. 6. The nuclear power plant of claim 1 wherein the secondary core catcher is external air cooled.
7. 7. A method of operating a nuclear power plant (10) according to any one of claims 1 to 6, the method comprising: Normally operating the nuclear power plant, during which the outer surface of the reactor pressure vessel (12) is surrounded by air, and The outside of the reactor pressure vessel is water cooled in case of emergency situations where cooling of the nuclear reactor is required or in case of safety testing of the nuclear power plant.
8. 8. The method of claim 7, wherein water cooling the exterior of the reactor pressure vessel comprises immersing the reactor pressure vessel in water.

Description

Nuclear power station Technical Field The present disclosure relates to a nuclear power plant. Background The nuclear power plant converts thermal energy generated by decay of a fissile material in the fuel assembly into electrical energy. A Pressurized Water Reactor (PWR) nuclear plant has a primary coolant loop that typically connects pressurized components, a Reactor Pressure Vessel (RPV) containing a fuel assembly, one or more steam generators, and one or more pressurizers. A coolant pump in the primary circuit circulates pressurized water through a piping system between these components. The RPV houses a nuclear reactor that heats water in a primary circuit. The steam generator serves as a heat exchanger between the primary circuit and the secondary circuit in which pressurized steam is generated to drive the turbine. The pressure regulator typically maintains the pressure in the primary circuit around 155 bar (bar). After passing through the turbine, the pressurized steam of the secondary circuit is cooled and condensed in one or more condensers before returning to the steam generator. The condenser transfers heat from the condensed steam to a tertiary circuit that circulates water between a tertiary radiator (i.e., ocean, lake or river) and the condenser, the tertiary radiator being the ultimate destination of the waste heat of the nuclear power plant. The design of the safety system of a nuclear power plant is to prevent a series of failures. Successful implementation of these safety measures ensures that the nuclear power plant conditions remain within safe limits. Failure of these safety measures can lead to core damage, known as a "severe accident". A severe accident safety system may be included in the design of a nuclear power plant to protect people and the environment from the deleterious effects of ionizing radiation by confining radioactive materials within the containment structure of the nuclear power plant. In particular, engineering structures may be included in the nuclear power plant to confine the molten core, supply water to cool these structures and maintain their structural integrity, and provide a separate radiator to remove heat from the containment system. Disclosure of Invention In general, the present disclosure provides a nuclear power plant with enhanced safety by having multiple molten core emergency safety shells. In a first aspect, the present disclosure provides a nuclear power plant having: a nuclear reactor comprising a reactor pressure vessel containing a plurality of fuel rods containing fissile material; Means for water cooling the outside of the reactor pressure vessel in the event of an emergency in which cooling of the nuclear reactor is required; a primary core catcher outside the reactor pressure vessel, the primary core catcher being formed of a material adapted to hold molten core melt in the event that the core melt escapes the reactor pressure vessel, and A secondary core catcher external to the primary core catcher, the secondary core catcher lining a tank that is filled with water in normal use of the nuclear power plant to submerge the primary core catcher and thereby water cool the primary core catcher, the secondary core catcher being formed of a material adapted to retain molten core melt in the event that the core melt escapes the primary core catcher. For molten core melt to escape the nuclear power plant from the core melt, at least three containment layers of the nuclear power plant must have failed, namely the outside water-cooled, water-cooled primary core catcher and secondary core catcher of the reactor pressure vessel. Thus, the likelihood of complete closure failure is significantly reduced. This reduced likelihood is further enhanced by the substantial independence of the three security shells. Furthermore, during the process from the innermost to the outermost containment layers, the melt temperature and melt volume will increase as the melt passes through these layers, the melt temperature increases due to decay heat, and the melt volume increases due to the molten core mixing first with the molten material of the reactor pressure vessel and second with the molten material of the primary core catcher. This increase in temperature results in an increase in temperature differential from the surrounding environment and the molten core melt outside the containment, ultimately promoting greater heat flux from the melt and increasing the likelihood of solidification. Delays due to having to pass through these security shells also reduce decay heat levels. In addition, the increased volume reduces the bulk density of decay heat, again increasing the likelihood of solidification. In a second aspect, the present disclosure provides a method of operating a nuclear power plant of the first aspect, the method comprising: Normally operating the nuclear power plant, during normal operation, the outer surface of the reactor pressure vessel being surrou