GB2535848A

GB2535848A - Secondary side passive waste heat removal system

Info

Publication number: GB2535848A
Application number: GB1600378.2A
Authority: GB
Inventors: Shen Yonggang; Lu Xianghui; Zhou Zhou; Rui Min; Zhang Jisheng; Hou Huaqing; Cui Xuyang; Lin Zhikang
Original assignee: China General Nuclear Power Corp; China Nuclear Power Technology Research Institute Co Ltd; CGN Power Co Ltd
Current assignee: China General Nuclear Power Corp; China Nuclear Power Technology Research Institute Co Ltd; CGN Power Co Ltd
Priority date: 2014-11-19
Filing date: 2015-03-31
Publication date: 2016-08-31
Anticipated expiration: 2035-03-31
Also published as: CN104361913A; WO2016078285A1; GB201600378D0; GB2535848B

Abstract

Disclosed is a secondary side passive waste heat removal system, comprising a steam pipeline (140) and a water supply pipeline (160), wherein the steam pipeline (140) hermetically penetrates a containment vessel and is connected to an outlet of a steam generator (130) arranged in the containment vessel as well as a cooling water tank (150) arranged outside the containment vessel, the water supply pipeline (160) hermetically penetrates the containment vessel and is connected to the cooling water tank (150) and an inlet of the steam generator (130), and the steam pipeline (140), the water supply pipeline (160) and the cooling water tank (150) form a circulating channel so as to remove decay heat in the containment vessel out of the containment vessel. The steam pipeline (140) and the water supply pipeline (160) are directly connected to the steam generator (130) on the secondary side so as to prevent the steam generator (130) from drying out, and coolant leakage, in the event of malfunction. The cooling water tank (150) is arranged outside the containment vessel, such that more available space of the containment vessel is obtained. Moreover, by using an open circuit, there is no need to arrange a heat exchanger, required by the conventional passive waste heat removal system, in the cooling water tank (150), and no emergency equipment is required, such that the expenditure on design and construction of the system is lowered.

Description

SECONDARY SIDE PASSIVE RESIDUAL HEAT REMOVAL SYSTEM FIELD OF THE INVENTION

[0001] The present invention relates to the field of safety equipments in nuclear power plant and, more particularly to a secondary side passive residual heat removal system used in a PWR. (pressurized-water reactor) nuclear power plant having a once-through steam generator.

BACKGROUND OF THE INVENTION

[0002[ The use of nuclear power is a breakthrough in the history of energy use, and high energy unmatched by any other conventional fossil energy can be produced via fission reaction of atomic nucleus, with a small quantity of nuclear fuel consumed. Thus the human pays attention to the utilization of the nuclear energy increasingly and expands the research and development in the field of nuclear energy progressively. Up to the present, nuclear energy has been one type of important energy in many countries in the world. However, nuclear accidents such as nuclear leakage may happen if protection is insufficient during the nuclear development, which may bring serious nuclear pollution to the environment and the human.

[0003] Containment in a nuclear power plant served as the final protection to prevent radioactive products from releasing to the environment is an important safety equipment in the reactor. Commonly, a residual heat removal system is configured at a primary side in the conventional PWR. nuclear power plant, so as to remove decay heat in the reactor core once a design basis accident or a beyond design basis accident is occurred. Such a system requires a cooling water tank installed in the containment, which occupies the available space of the containment, and a heat exchanger placed in the reload water tank, which increases the design cost and the construction cost of the system. Once a heat transfer tube is broken, the coolant in the primary loop may be leaked. Additionally, such a system further requires in-plant and out-plant power supply, emergency equipments (such as an expensive emergency diesel), and operators, which may increase risk of human mistake and increase equipment amount thereby the equipment cost of purchasing, installing, running and maintaining is increased, and the construction and malignance cost of the nuclear power plant is increased accordingly.

[00041 Thus, there is a need to provide an improved secondary side passive residual heat removal system which can passively remove decay heat in a nuclear accident and reduce construction, running and maintenance cost, to overcome the drawback mentioned above.

SUMMARY OF THE INVENTION

[00051 One objective of the present invention is to provide an improved secondary side passive residual heat removal system which can passively remove reactor core decay heat in a nuclear accident and reduce construction, running and maintenance cost.

[00061 To achieve the above-mentioned objectives, a secondary side passive residual heat removal system of the present invention, adapted to remove decay heat of reactor core in a containment, includes a cooling water tank configured outside the containment; a steam pipeline adapted for hermetically running through the containment and being connected to an outlet of a steam generator configured in the containment; and a water pipeline adapted for hermetically finning through the containment and connected to the cooling water tank and an inlet of the steam generator respectively. The steam pipeline, the water pipeline and the cooling water tank form a circulation channel whereby the decay heat in the containment is removed to the outside.

[0007] Preferably, the location of the cooling water tank is higher than that of the steam generator.

[00081 Preferably, the steam pipeline has an d to the outlet of the steam generator and an outlet inserted into coolants in the cooling water tank, [0009] Preferably, the water pipeline has an nlet connected to a bottom of the cooling water tank and an outlet connected to the inlet of the steam generator.

[0010] Preferably, the steam pipeline is provided with a first ve which s configured in the containment.

[00111 Preferably, the water pipeline is provided with a second valve which is configured outside the containment and a third valve which is configured in the containment, [0012] Preferably, the outlet of the steam generator is located at an upper end, and the inlet of the steam generator is located at a lower end.

[0013] Preferably, the steam generator is connected to a pressure vessel in the containment, and the steam generator is connected to a main water pipeline and a main steam pipeline respectively.

[0014] Preferably, the main water pipeline is provided with a fourth valve, and the main steam. pipeline is provided with a. fifth valve; both of the fourth and the fifth valves are configured in the containment.

[0015] Preferably, the cooling water lank is open.

[0016] Preferably, the steam generator is a once-through steam generator.

[0017] In comparison with the prior art, the secondaside passive residual heat removal system of the present invention includes the steam pipeline and the water pipeline. The steam pipeline hermetically runs through the containment and is connected to the cooling water tank that is connected to the outlet of the steam generator and configured outside the containment, and the water pipeline hermetically runs through the containment and is connected to the cooling water tank and the inlet of the steam generator. The steam pipeline, the water pipeline and the cooling water tank form a circulation channel whereby the decay heat in the containment is removed to the outside. After an accident occurs, the steam in the steam generator goes into the cooling water tank via the steam pipeline, and then is condensed therein, whereafter the water in the cooling water tank flows back to the steam generator via the water pipeline, such that a passive and natural circulation loop is formed in the circulation channel by means of density difference and height difference. Subsequently, the water in the tank will be heated. to become steam which is discharged to the atmosphere, and the water level in the tank will be decreased gradually. After the cooling water in the tank is used up, the steam from the steam generator will be directly discharged to the atmosphere, so that the decay heat in the core will be removed passively, which reduces the possibility of the system failure and prevents damage brought by the power failure and man-induced errors thereby improving safety of the unclear power plant. Furthermore, no emergency equipment is required thereby reducing the equipment amount and the cost for purchasing, installing, running and maintaining such equipments, and saving the construction and maintenance cost of the nuclear power plant finally. In addition, since the steam pipeline and the water pipeline arc connected to the steam generator directly, thus the steam generator is prevented from boiling away and the coolant leakage is prevented, in a possible nuclear accident. And the available space in the containment is saved since the cooling water tank is configured outside the containment.

Moreover, an open cycle loop is applied in the present system, instead of installing a heat exchanger in the cooling water tank required in the conventional system, thereby reducing the design cost and construction cost of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings facilitate an understanding of the various embodiments of this invention. In such drawings: [00191 1 is a schematic view of a secondary side passive sidual heat removal system according to the present invention; [0020] Fig. 2 is a schematic view of a secondary side passive residua removal system according to the present invention, showing an operation status; and [0021] Fig. 3 is another schematic view of a secondary side passive residual heat removal system according to the present invention, showing another operation status.

DETAILED DESCRIPTION-OF ILLUSTRATED EMBODIMENTS

[0022] Various preferred embodiments of the invention will now be described with reference to the figures, wherein like reference numerals designate similar parts throughout the various views.

[0023] Referring to Fig. 1, a secondary side passive residual heat removal system 100 according to the present invention can passively rove reactor core decay heat inside a containment 110 in a nuclear accident and reduce construction and maintenance cost. A pressure vessel 120 and a steam generator 130 connected together are configured in the containment 110. Generally, 2 to steam generators 130 are used in a PWR nuclear power plant, and one of them is shown in the present embodiment, other ones are we11 known to one skilled in the art. And the steam generator 130 is the only heat exchanger for removing the heat energy in the primary loop in the PWR. nuclear power plant.

[0024] In the present invention, the steam generator 130 is once-through steam generator (OTSG) which has smaller water inventory; thus water in the cooling water tank 150 (described later) can pass through the OTSG easily to form a. single-phase natural circulation, which is unable by a conventional steam generator.

[0025] Optionally, only one secondary side passive residual heat removal system 100 can be configured to connect with multiple steam generators 130 respectively; or multiple secondary side passive residual heat removal systems 100 also can be configured, each of which is connected with one steam generator 130.

[0026] Referring to Fig. 1 again, the example of one system 100 connecting with one steam generator 130 is described as following.

[0027] As shown, the secondary side passive residual heat removal system includes a steam pipeline 140, a water pipeline 160, and a steam generator 130 in the containment 110. The steam pipeline 140 hermetically runs through the containment 110 and is connected to a cooling water tank 150 that is connected to the outlet of the steam generator 130 and configured outside the containment 110, and the water pipeline 160 hermetically runs through the containment 110 and is connected to the cooling water tank 150 and the inlet of the steam generator 130. The steam pipeline 140, the water pipeline 160 and the cooling water tank 150 form a circulation channel whereby the decay heat in the containment 110 is removed to the outside.

[0028] Specifically, the cooling water tank 150 is open at the top, and the installation location of the cooling water tank 150 is higher than that of the steam generator 130. Water sufficient for removing reactor core decay heat is filled in the cooling water tank 150. Due to the cooling water tank 150 is installed in a high location relative to the steam generator 130 to produce a height difference for the natural circulation, thus the cooling water in the tank 150 will go into the steam generator 130 automatically and then be heated to remove the heat energy in the primary loop, once the steam pipeline 140 is connected with the water pipeline 160. Further, when the water in the tank 150 is vaporized to expend, the steam from the steam generator 130 will be discharged to the atmosphere directly via the steam pipeline 140 since the cooling water tank 150 is opened. Additionally, the tank 150 will not occupy the space of the containment 110 since it is configured outside the containment 110.

[0029k Specifically, the outlet of the steam generator 130 is located at the upper end, and its inlet is located at the lower end, the steam pipeline 140 has an inlet 140a connected to the outlet of the steam generator 130 and an outlet 140b extended into the cooling water tank 150 and inserted into the cooling water with a predetermined depth. The water pipeline 160 has an inlet 160a connected to the bottom of the cooling water tank 150 and an outlet 160b connected to the inlet of the steam generator 130. in such a way, the steam generator 130, the steam pipeline 130, the cooling water tank 150 and the water pipeline 160 form an open cycle loop circulation channel, which prevents the steam generator 130 from boiling away and prevents the coolant leakage in the primary loop, 111 a possible nuclear accident.

[0030] Further, the steam pipeline 140 is provided with a first valve 141 which is configured in the containment 110. The water pipeline 160 is provided with a second valve 161 configured outside the containment 110 and a third valve 162 configured in the emit° enI 110. The first, the second, and the third valves 141, 161, 162 are closed when he nuclear power plant is in normal running, and will he turned on once an accident occurs, thereby starting the secondary side passive residual heat removal system 100.

100311 In the embodiment, one end of the steam generator 130 is further connected to a main water pipeline 170, and the outlet of the steam generator 130 is further connected to a main steam pipeline 180. When the nuclear power plant is under normal running, the nuclear reactor core in the primary loop produces huge heat energy due to the fuel fission, by which the feedwater in the primary loop is heated to become steam, Then the steam passes through heat transfer tubes in the steam generator 130, whereby the heat energy is transferred to the cooling water in the secondary loop, and the feedwater will be carried to the reactor core to heat again. The cooling water in the secondary loop is vaporized and then goes into a turbine to do work via the main steam pipeline, in such a way, the heat energy is converted to electric energy. Subsequently, the steam will be condensed to water by a condenser, which is sent to the steam generator 130 again to produce steam again.

[00321 Specifically, the main water pipeline 170 is provided with a fourth valve 171, and the main steam pipeline [80 is provided with a fifth valve 181; both of the fourth and the fifth valves 171, 181 are configured in the containment 110 and are turned on u dc., the normal running of the nuclear power plant.

100331 By combination of Figs. 1 to 3, the working principle of e secondary side passive residual heat removal system 100 is explained.

[00341 As shown in Fig. 1, when the nuclear power plant is under normal running, the secondary side passive residual heat removal system 100 will not started but be on standby. Under this condition, the first, the second, and the third valves 14 I, 161, 162 are turned off, and the fourth and the fifth valves 171, 181 are turned on.

[0035] As shown in Fig. 2, in accident conditions (from design basis accidents to beyond design basis accidents such as plant blackout), the reactor stops working, and the secondary side passive residual heat removal system 100 is triggered to start by a corresponding protection signal. At this time, the fourth valve 171 and the fifth valve 181 are isolated, and the first, the second and the third valves 141, 161, 162 are turned on in order, such that the steam in the steam generator 130 passes through the outlet and goes into the steam pipeline 140, and then passes through the outlet 140b of the steam pipeline 140 and goes into the cooling water tank 150 and then is condensed therein. Subsequently, the water in the cooling water tank 150 flow back to the steam generator 130 via the water pipeline 160, such that a passive and natural circulation loop is formed in the circulation channel by means of density difference and height difference. While heat will he transferred to the cooling water in the tank 150, steam is condensed in the cooling water tank 150. In the early stage of an accident, the temperature of the cooling water in the tank 150 will increase continuously to reach 100t while boiling, as a result, the water in the tank 150 be converted into steam that is discharged to the atmosphere, and the water level in the tank 150 will be decreased gradually.

100361 As shown in Fig. 3, the outlet 1401) of the steam pipeline 140 will be exposed to the after a part of the cooling water in the tank 150 is spent, which causes the steam from the steam generator 130 discharge to the atmosphere, and no heat is entered to the cooling water tank 150. However the remain water in the tank 150 will be expended due to the water pipeline 160 coimected. After the water is used up for a certain time, the function of the circulation removal system will he lost f no water is supplied to the cooling water tank 150.

[0037] Because the steam pipeline 140 and the water pipeline 160 are connected with the steam generator 130 directly to form an open cycle loop, thus decay heat in the core can be removed passively, which reduces the possibility of the system failure.

100381 In the present invention, tire. secondary side passive residual heal removal system 100 includes the steam pipeline 140 and the water pipeline 160. The steam pipeline 140 hermetically runs through the containment 110 and is connected to the cooling water tank 150 that is connected to the outlet of the steam generator 130 and configured outside the containment 110, and the water pipeline 160 hermetically nms through the containment 110 and is connected to the cooling water tank 150 and the inlet of the steam generator 130. The steam pipeline 140, the water pipeline 160 and the cooling water tank 150 form a circulation channel whereby the decay heat in the containment 110 is removed to the outside. After an accident occurs, the steam in the steam generator 130 goes into the cooling water tank 150 via the steam pipeline 140, and then is condensed therein, whereafter the water in the cooling water tank 150 flows hack to the steam generator 130 via the water pipeline 160, such that a passive and natural circulation loop is formed in the circulation channel by means of density difference and height difference. Subsequently, the water in the tank 150 will he, heated to become steam which is discharged to the atmosphere, and the water level in the tank 150 will be decreased gradually. After the cooling water in the tank 150 is used up, the steam from the steam generator 130 will be directly discharged to the atmosphere, so that the decay heat in the core will be removed passively, which reduces the possibility of the system failure and prevents damage brought by the power failure and man-induced errors thereby improving safety of the unclear power plant. Furthermore, no emergency equipment is required thereby reducing the equipment amount and the cost for purchasing, installing, running and maintaining such equipments, and saving the construction and maintenance cost of the nuclear power plant finally. In addition, since the steam pipeline 140 and the water pipeline 160 are connected to the steam generator 130 directly, thus the steam generator 130 is prevented from boiling away and the coolant leakage is prevented, in a possible nuclear accident.

The available space the containment 110 is saved, due to the cooling water tank 150 is configured outside the containment 110. Moreover, an open cycle loop is applied in the present system, instead of installing a heat exchanger in the cooling water tank required in the conventional system, thereby reducing the design cost and construction cost of the system.

[00391 In addition, the detailed structure of the pressure vessel 120 and the steam generator 130 are well known to one skilled in the art, which are omitted here thereby.

100401 While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope invention. It

Claims

WHAT IS CLAIMED IS: 1. A secondary side passive residual heat removal system, adapted to remove decay heat of reactor core in a containment, comprising: a cooling water tank configured outside the containment; a steam pipeline adapted for hermetically running through the containment and being connected to an outlet of a. steam generator configured in the containment; and a water pipeline adapted for hetmetically running through. the containment and connected to the cooling water tank and an inlet of the steam.venerator respectively; the steam pipeline, the water pipeline and the cooling water tank forming a circulation channel whereby the decay heat in the containment is removed to the outside.
2. The secondary side passive residual heat removal system according to claim 1, wherein the location of the cooling water tank is higher than that of the steam generator.
The secondary side passive residual heat removal system according to claim I; wherein the steam pipeline has an inlet connected to the outlet of the steam generator and an outlet inserted into coolants in the cooling water tank.
4. The secondary side passive residual heat removal system according to claim 1, wherein the water pipeline has an inlet connected to a bottom of the cooling water tank and an outlet connected to the inlet of the steam generator.
5. The secondary side passive residual heat removalsystem according to claim I, whe the stew pipeline is provided with a first valve configured in the containment.
6, The secondary side passive residual heat removal system according to claim 1, wherein the water pipeline is provided with a second valve configured outside the containment and a third valve configured in the containment.
7. The secondary side passive residual heal removal system according to claim 1, wherein the outlet of the steam generator is located at an upper end, and the inlet of the steam generator is located at a lower end.
8. The econdary side passive residual heat removal system according to claim 1, wherein the steam generator is connected to a pressure vessel in the containment, and the steam generator is connected to a main water pipeline and a main steam pipeline respectively.
9. The secondary side passive residual heat removal system according claim wherein the main water pipeline is provided with a fourth valve, and the main steam pipeline is provided with a fifth valve; both of the fourth and the filth valves are configured in the containment
10.The secondary side passive residual heat removal system according to claim 1, wherein the cooling water tank is open.

1 I.The secondary side passive residual heat removal system according to claim 1, whereinthe team generator is a once-through steam generator.