JP4396482B2 - Water supply nozzle and nuclear reactor equipment using the water supply nozzle - Google Patents

Description

  The present invention relates to a water supply nozzle having a thermal sleeve inside.

  Boiling water light water reactor (BWR) boiles water in a core containing fissile material, passes the steam generated by boiling through the main steam pipe to the high-pressure turbine and low-pressure turbine, and interlocks with the shafts of the high-pressure turbine and low-pressure turbine. The generator is used to generate electricity. In a normal BWR, the steam is condensed into water by a condenser installed on the outlet side of the low-pressure turbine, and then pressurized and heated through a feed water heater and a feed water pump to be fed into the reactor pressure vessel. .

  In a normal BWR design, first, the thermal output of the core is determined, and the steam flow after the main steam pipe is optimized so that the highest thermal efficiency can be obtained with the thermal output. Specifically, when steam is converted to water by a condenser, 2/3 of the energy is discharged and wasted at the normal BWR pressure (about 7 MPa) from the principle of thermal cycle.

  Therefore, a part of the main steam is extracted and used to heat the feed water in the feed water heater. In this case, most of the heat of the main steam is recovered, so that the thermal efficiency of the reactor is improved. Generally, in a BWR equipped with a moisture separator using a recirculation pump and a jet pump, the amount of steam finally sent from the low-pressure turbine outlet to the condenser is about 56% of the main steam, and the remaining steam Is used for heating water supply.

  The feed water is heated by a feed water heater and fed to the reactor pressure vessel from the feed nozzle through the feed water system. When a large temperature difference occurs between the water supply and the atmosphere in the reactor pressure vessel during the water supply, an unreasonable temperature difference is added to the water supply nozzle and its surroundings. Therefore, in order to alleviate the unreasonable situation, a cylindrical structure called a thermal sleeve is adopted in the water supply nozzle, and the water supply nozzle has a double pipe structure so that the shock due to the temperature difference is reduced ( For example, see JP-A-10-288690.

Japanese Patent Laid-Open No. 10-288690

  In Japanese Patent Application No. 2004-006198 filed earlier than this application, a method of lowering the feed water temperature without increasing the main steam flow rate and the feed water flow rate is proposed in order to remove the heat output in the core. At this time, in the water supply nozzle portion, a large temperature difference occurs between the temperature inside the high temperature reactor pressure vessel and the temperature of the water supplied from the low temperature water supply pipe, and there is a concern about thermal stress and thermal fatigue at the nozzle portion. Therefore, a water supply nozzle and a sleeve that ensure structural soundness even during the increased output operation are required.

  In general, it is assumed that a newly installed nuclear reactor operates at a constant electric power or heat output. Therefore, replacement of plant equipment is necessary to greatly increase the power output after the reactor is installed. On the other hand, if the plant equipment is designed in advance with an expectation of an increase in output, the size of each equipment increases and the efficiency of the equipment also decreases.

  Next, when increasing the output of an existing reactor, the feed water flow rate and the main steam flow rate increase in proportion to the increase in output. For this reason, design margins of almost all devices such as feed water piping, feed water heaters, feed water pumps, steam dryers and other in-furnace structures, main steam pipes, high pressure turbines, low pressure turbines and condensers are reduced. In a normal BWR, one of the devices that initially loses its design margin due to an increase in the main steam flow rate is a high-pressure turbine. In nuclear power generation systems other than BWR, there is a similar problem for a plant having a relatively small design margin for a high-pressure turbine.

  An object of the present invention is to provide a water supply nozzle that is easy to ensure the soundness of the water supply nozzle when there is a concern about thermal stress and thermal fatigue at the water supply nozzle portion, and another object is to use the water supply nozzle. The purpose of the present invention is to provide a nuclear reactor facility that can safely perform an increased output operation of the nuclear reactor facility while ensuring soundness.

Means for achieving the object of the invention of this application is a water supply nozzle having a thermal sleeve therein, wherein the interval between the annular flow paths formed between the inner surface of the water supply nozzle and the outer surface of the thermal sleeve is δ. and then, the inner diameter of the water supply nozzles and D _i, a water supply nozzle, characterized in that the relationship between the said spacing inside diameter of δ / D _i ≦ 0.03, or water nozzle with a thermal sleeve inside In the above, a rib whose longitudinal direction is directed in the longitudinal direction of the water supply nozzle or the thermal sleeve is provided between the inner surface of the water supply nozzle and the outer surface of the thermal sleeve and / or the inner surface of the thermal sleeve. In the water supply nozzle characterized by the above, or the water supply nozzle provided with a thermal sleeve inside,
The Bei example annular or helical member between the inner surface of the water supply nozzle and the outer surface of the thermal sleeve, the spacing of the flow path between the inner surface and the annular or spiral member of the water supply nozzle and [delta], the the inner diameter of the water supply nozzles and D _i, a water supply nozzle, wherein the relationship between the distance between the inner diameter of δ / D _i ≦ 0.03.

  According to the water supply nozzle of the present invention, there is an effect that it is easy to ensure the soundness of the water supply nozzle when there is a concern about thermal stress and thermal fatigue at the water supply nozzle portion.

  According to the nuclear reactor equipment of the present invention, it is possible to increase the output while appropriately maintaining the design margin of the water supply system equipment.

  An embodiment of the present invention will be described with reference to FIGS. First, FIG. 1 shows a system diagram relating to a heat balance shift method for a low pressure turbine of a boiling water light water reactor at the time of increased output, which is a preferred embodiment of the present invention. High-pressure main steam generated from the reactor pressure vessel 1 is supplied from the main steam pipe 2 to the high-pressure turbine 3 and converted into rotational energy by the high-pressure turbine 3 to work. Thereafter, the expanded main steam is supplied to the moisture separator 4, and after the moisture is removed by the moisture separator 4, the steam performs the same work in the low-pressure turbine 5, and the expanded low-pressure steam is recovered. Condensate in water bottle 6. Thereafter, the condensed cooling water is heated and boosted by the low-pressure feed water heater 7, the main feed water pump 8 and the high-pressure feed water heater 9, and is supplied again into the reactor pressure vessel 1. In a normal boiling water light water reactor, the water supply temperature of the coolant is achieved by using the extracted steam or drain water from the high-pressure turbine or moisture separator for feed water heating within the range where the soundness of the core is sufficiently secured in the event of an accident or transition. Is designed to maximize the thermal efficiency. In FIG. 1, the thermal output of the core is represented by Q, the mass flow rate of water and steam is represented by G, and the enthalpy of water and steam is represented by H. The thermal output Q and mass flow rate G are relative to the main steam flow rate during plant construction. The ratio (%) and enthalpy are expressed in numerical values in units of (kJ / kg).

  In this embodiment, the power of the core is increased by 5% and the ratio of the bleed air from the high-pressure turbine outlet is reduced as compared with the time of plant construction. This is to reduce the heating amount of the water supplied to the pressure vessel, so that the temperature and enthalpy of the supplied water are lowered. As the temperature of the feed water at the inlet of the pressure vessel decreases, the amount of heat absorbed by the water, which is the coolant in the core, begins to boil, and when this balances with the increase in power, the power of the core is increased. However, the main steam flow does not increase. Although the main steam flow and the steam flow of the high-pressure turbine do not increase, the amount of steam entering the low-pressure turbine 5 increases because the amount of steam for the high-pressure feed water heater 9 extracted from the outlet of the high-pressure turbine 3 is reduced. As a result, the low-pressure turbine The amount of steam flowing from 5 into the condenser 6 also increases. In order to reduce the extraction flow rate, an orifice or a flow rate adjustment valve 10 is provided on the extraction pipe between the extraction point and the feed water heater. As another method, the water supply bypass pipe 11 may be installed on the main water supply pipe, and at least one water heater may be bypassed and then returned to the water supply pipe. In a nuclear power generation system, approximately 2/3 of the power generation is generally recovered by a low-pressure turbine. By increasing the amount of steam entering the low-pressure turbine, it is possible to increase the electrical output of the reactor without increasing the main steam flow rate. It is. In the method shown in this embodiment, the electric output can be increased by about 4% without changing the main steam flow rate.

  That is, in the embodiment of the present invention, when the flow rate of steam flowing into the main steam pipe from the reactor pressure vessel after the increased output is Gf1, and the flow rate of steam flowing into the condenser from the low-pressure turbine is Gf2, Is characterized by increasing Gf2 / Gf1. By taking such a heat balance, although the thermal efficiency of the plant is reduced, the feed water temperature is lowered, so that the safety of the core is improved and the pressure loss is reduced as compared with the normal power increase. Since the feed water flow rate and the main steam flow rate can be kept low, it is possible to increase the output without reducing the design margin between the feed water system and the high pressure turbine. Furthermore, it is possible to implement a large increase in power without replacing a high-pressure turbine that generally needs to be replaced at a large increase in power. To prevent decline in plant thermal efficiency, increase reactor pressure, replace moisture separator with moisture separation reheater or moisture separation superheater, introduce pump drain up to feed water heating system, etc. Just do it. A direct cycle type plant other than the boiling water type light water reactor can increase the output by the same method.

  In this way, when performing the increased output operation by the thermal balance shift method, the feed water temperature decreases, so the temperature difference from the reactor water at the feed water nozzle part installed on the side of the reactor pressure vessel becomes larger than before. Therefore, an increase in high-cycle thermal fatigue based on temperature fluctuations due to thermal stratification in the annular channel is expected. At this time, in the conventional water supply nozzle, the thermal stratification and the maximum temperature generation location which are the cause of the temperature fluctuation are not specified, so the water supply nozzle structure under the increased power operation condition is indispensable for reducing the thermal stress. .

  FIG. 2 shows an outline of a water supply nozzle which is a preferred embodiment of the present invention. 3 to 6 show an outline of the mechanism of temperature fluctuation and thermal fatigue for explaining these operations and characteristics. FIG. 3 is a schematic diagram of the temperature distribution around the water supply nozzle, FIG. 4 is a phenomenon explanatory diagram regarding density difference separation by thermal stratification inside the water supply nozzle, and FIG. 5 is an overview of the wall temperature fluctuation ratio with respect to the heat transfer coefficient and fluid temperature fluctuation. FIG. 6 and FIG. 6 show a schematic diagram of the thermal fatigue evaluation flow of the water supply nozzle.

  FIG. 2 shows a portion of a water supply nozzle in which a water supply pipe 12 is installed in the reactor pressure vessel 1. Here, in order to reduce the thermal stress due to the temperature difference during mixing of these two fluids between the reactor water 18 and the feed water 17, a thermal sleeve 14 is installed inside the feed water nozzle 13 so that the two fluids having a direct temperature difference can be obtained. The structure is such that the contact is avoided and the water supply sparger 15 at the tip of the thermal sleeve is ejected into the reactor pressure vessel 1. At this time, fluid temperature fluctuations in the narrow annular flow path 16 (hereinafter also abbreviated as gap δ) between the water supply nozzle 13 and the thermal sleeve 14 are suppressed, and natural convection heat transfer is reduced in the gap 16. It is necessary to suppress the temperature fluctuation of the material on the inner wall surface of the water supply nozzle (hereinafter also referred to as the inner surface of the water supply nozzle) 13a. For that purpose, it is necessary not only to study from the viewpoint of the structural strength that has been conventionally performed, but also to suppress the cause of fluid temperature fluctuations due to the formation of the thermal stratification interface, which is the cause of thermal fatigue. Therefore, in the present invention, the optimization of the gap size was studied.

FIG. 3 shows an outline of the temperature distribution T around the water supply nozzle. The high temperature reactor water Tr and the low temperature feed water Tfw exchange heat in the feed nozzle portion, and the temperature of the reactor water decreases. On the other hand, the temperature of the feed water 17 heated by the reactor water 18 rises along the flow direction toward the center of the reactor, and finally flows out from the feed water sparger 15 outlet into the reactor water, resulting in temperature difference mixing. At this time, the temperature of the reactor water in the annular channel decreases due to heat exchange, and the high-temperature water Trh has a low density, so that the density of the low-temperature water Trc is high. Separation causes thermal stratification. However, if the thermal stratification interface 19 is statically stable even if stratification occurs, the water supply nozzle and the thermal sleeve pose only a problem of static thermal stress generation. However, the disturbance included in the downward flow of the reactor water 18 acts on the thermal stratification interface 19 to cause temperature fluctuation. Fluid temperature fluctuations at this time are propagated to the inner surface of the water supply nozzle 13 and the outer surface of the thermal sleeve 14 through heat transfer in the gap, and thermal fatigue due to temperature fluctuations of these materials occurs, and this is avoided. There is a need to.

Also consider the heat flow phenomenon around the water supply nozzle. FIG. 4 shows a phenomenon related to thermal stratification inside the water supply nozzle. As shown in the figure, at the time of water supply for rated operation, low temperature water 17 is supplied from the water supply pipe to the place where the high temperature reactor water is stopped in the gap, and the thermal sleeve is supplied from the high temperature water in the gap via the thermal sleeve 14. Heat is input 21 to the low-temperature water in 14 to exchange heat. As a result, the temperature of the high-temperature water that remains in the gap decreases. However, the temperature does not decrease evenly in the narrow gap, and natural convection is generated and the high temperature water has a low density, so the density difference is separated to the upper part in the gap, and the low temperature water has a high density, so the density difference is separated to the lower part. To go. In the gap, natural convection vortices called small Benard cells gradually merge to form a large convection vortex 20a. That is, a thermal stratification phenomenon accompanied by natural convection heat transfer occurs in the annular flow path between the water supply nozzle 13 and the thermal sleeve 14. On the other hand, when starting and stopping, since the water supply 17 from the water supply pipe is in a stopped state, the low-temperature water supply in the thermal sleeve 14 receives heat 21 from the surroundings, and finally thermal stratification occurs. Temperature fluctuation occurs.

Here, from the viewpoint of thermal fluid, it is considered the Reynolds number Re _c Rayleigh number Ra and the water supply nozzle in the annular flow path is a dimensionless number expressed by the following equation.

Ra = Gr · Pr = (δ ³ βgΔT / ν ² ) · Pr (1)
_{Re c = vD i / ν (} 2)
Where δ is the interval (gap) of the annular flow path, β is the body expansion coefficient, g is the gravitational acceleration, ΔT is the temperature difference, ν is the kinematic viscosity coefficient, Pr is the Prandtl number, v is the pipe flow velocity, _Di is the nozzle inner diameter It is.

Despite the size of the water supply nozzle, Ra> In 1700 the annular flow path within a small Benard cell becomes natural convection field by a large natural circulation vortices in complex, also Re _c> 1.0 × 10 ⁴ in the nozzle is uniformly developed Forced convection field. Here, as shown in the equation (1), the Grashof number Gr and the Rayleigh number Ra become smaller in proportion to the cube of the gap δ, and the natural relationship between the water supply nozzle and the thermal sleeve is reduced from the relationship shown in the equation (3). Even if the convective heat transfer coefficient h decreases and thermal stratification occurs, temperature fluctuations in the vicinity of this interface are not easily transmitted to the temperature fluctuation occurrence point 22 of the water supply nozzle material and the thermal sleeve material.

Nu∝h∝Ra ^m δ (δ ³ ) ^m (3)
Where Nu is the Nusselt number and m is an exponent.

Next, FIG. 5 shows the heat transfer coefficient in the annular flow path of the water supply nozzle and the wall surface temperature fluctuation ratio with respect to the fluid temperature fluctuation. Here, ΔTw on the vertical axis indicates wall surface temperature fluctuation, and ΔTf indicates fluid temperature fluctuation. ΔTw / ΔTf ≦ 0.3 in the figure indicates a target value for avoiding thermal fatigue of the water supply nozzle. As shown in the upper right in the figure, depending on the magnitude of the heat transfer coefficient h, there is a possibility that the large fluid temperature fluctuation amplitude ΔTf may become a small wall surface temperature fluctuation amplitude ΔTw. The examination conditions were BWR 1.1 million kWe, the material of the water supply nozzle was stainless steel, the inner diameter of the water supply pipe was D = 280 mm, and the uncertain temperature fluctuation frequency f was used as a parameter. Conventionally, the following equation has been used as a prediction equation relating to wall surface temperature fluctuation (see H. Choe, CM Kwong, ASME 79-WA / HT-23, 1980 for the source).

ΔTw / ΔTf = 1 / √2e ² + 2e + 1 (4)
e = √ρ _m πC _m λ _m f / h (5)
Here, ρ _m is the density of the material, C _m is the specific heat of the material, λ _m is the thermal conductivity of the material, and h is the heat transfer coefficient. The constant e in the equation (5) indicates the temperature fluctuation ratio transmitted from the fluid to the material, and these ratios are expressed as an empirical expression such as the expression (4). As a result, the wall surface temperature fluctuation ratio ΔTw / ΔTf monotonously increases as the heat transfer coefficient h increases. Also, ΔTw / ΔTf tends to decrease as the fluctuation frequency f increases. Therefore, in order to satisfy ΔTw / ΔTf ≦ 0.3 as the limit of the allowable fluctuation thermal stress from the results shown in the figure, h ≦ 900 W / m even if the smallest frequency f = 0.01 Hz considered from the actual phenomenon is considered ^It needs to be 2K. This needs to satisfy δ ≦ 10 mm from the relationship of the expression (3).

  Therefore, if the following relationship is satisfied, thermal fatigue on the inner surface of the water supply nozzle due to thermal stratification can be avoided.

δ / D _i ≦ 0.03 (6)
Here, _Di is the feed nozzle inner diameter.

A procedure for evaluating thermal fatigue of the water supply nozzle material will be described based on the above water supply nozzle structure and conditions. FIG. 6 shows an outline of the thermal fatigue evaluation flow of the water supply nozzle. First, low-temperature water supply and high-temperature reactor water exchange heat through a thermal sleeve. Next, it is divided into two phenomena on the left and right in the driving state. The left side of the figure shows the evaluation flow for high cycle thermal fatigue during rated operation. Separation occurs due to the difference in density of high and low temperature water in the annular flow path, and thermal stratification occurs. Fluid temperature fluctuations occur due to reactor water disturbance at this stratification interface. This fluid temperature fluctuation is propagated as a temperature fluctuation on the wall surface of the material on the inner surface of the water supply nozzle and the outer surface of the thermal sleeve by natural convection heat transfer, and high cycle thermal fatigue due to this is generated. This means a fluctuating load of temperature fluctuation that fluctuates rapidly. When viewed from the operation state of the entire reactor, the cumulative damage coefficient UF _h is large because it is operated for a long time while receiving a small temperature fluctuation load, that is, the number of fluctuations is large. On the other hand, the right side of the figure shows an evaluation flow of low cycle thermal fatigue due to thermal cycle at start / stop. When starting and stopping, the largest temperature difference occurs between the upper and lower parts of the thermally stratified annular flow path, and the static thermal stress fluctuates slowly due to the gentle thermal transient cycle, resulting in low cycle thermal fatigue. Happens. This means a gradual transient fluctuating load. When viewed from the operating state of the entire reactor, although it receives a large temperature fluctuation load, the cumulative damage coefficient UF _l is small because of the short time operation, that is, the fluctuation frequency is small. By adding the cumulative damage coefficient UF _l and cumulative damage coefficient UF _h of both calculating a final cumulative damage coefficients UF (U sage F actor), there is a potential for thermal fatigue against the water supply nozzle and the thermal sleeve material Determine whether or not. If this value is 1 or less, it is structurally sound.

According to the above evaluation flow, the value of the cumulative damage coefficient UF was compared between the conventional type and the example of the present invention. FIG. 7 shows the result. Here, the cumulative damage factor UF represents the sum of the cumulative damage factor UF _l by cumulative damage factor UF _h and the low cycle thermal fatigue due to high cycle thermal fatigue. When the current operation is performed using the conventional water supply nozzle, UF is about 0.3, but at the time of the increased output operation, that is, when the water supply temperature is lowered by about 20 to 30 ° C. than before, UF = 1.6 It increases to. Here, UF <1 is a general criterion as a criterion capable of avoiding thermal fatigue on the material surface. Therefore, with the conventional structure and dimensions, thermal fatigue due to temperature fluctuations in the gap may be a problem. On the other hand, in the water supply nozzle of the present invention, UF = about 0.7, and it was confirmed that there was no problem in thermal structural integrity. In addition, what is shown in the figure is an example evaluated under the same examination conditions. It differs slightly depending on the temperature difference between the two fluids, the type of material, the gap, the fluctuation frequency, the surface roughness of the structural material, the flow of the reactor water, the feed water flow rate, etc. I will note that.

In such an embodiment of the present invention, in order to achieve the object of the present invention, the gap in the annular flow path between the water supply nozzle and the thermal sleeve is set so that the natural convection heat transfer coefficient is 900 W / m ² K or less. Make it smaller. Thereby, even if thermal stratification occurs between the low-temperature feed water and the high-temperature reactor water, the heat transfer rate to the inner surface of the feed water nozzle is small, and the temperature fluctuation on the inner surface of the feed water nozzle is small. Thereby, material soundness due to thermal fatigue due to temperature fluctuation can be ensured.

  8 to 17 show another embodiment of the present invention. First, FIG. 8 shows an outline of the structure of the water supply nozzle when at least one outer rib 14c, which is a rib mechanism, is attached to the outer surface 14a of the thermal sleeve in order to suppress thermal stratification in the annular flow path. This has a length to the nozzle end in the axial direction of the thermal sleeve. If possible, it is desirable to install eight at a 45 degree pitch in the circumferential direction at the minimum. Thereby, the heat transfer coefficient in the gap 16 can be suppressed. This is for attenuating fluid temperature fluctuations at the thermal stratification interface formed in the annular flow path during rated operation. The advantage in this case is that it is possible to achieve the above-described effect of reducing the heat transfer coefficient by using the specifications of the conventional thermal sleeve 14 as they are, and therefore, the modification is relatively easy. Furthermore, even if bending due to reactor internal pressure or static thermal deformation occurs, the pipe outer rib 14c, which is the rib mechanism, comes into contact with the inner surface of the water supply nozzle and the outer surface of the thermal sleeve and is in a simple support state. Can also be suppressed. In the following embodiments, at least one or more rib mechanisms are installed on the inner and outer surfaces. FIG. 9 is a schematic diagram of the structure of the water supply nozzle when the pipe rib 14d as a rib mechanism is attached to the inner surface 14b of the thermal sleeve. This is for attenuating fluid temperature fluctuations at the thermal stratification interface formed in the thermal sleeve when the water supply is stopped. FIG. 10 combines the advantages of both FIG. 8 and FIG. FIG. 11 shows a mechanism for suppressing natural convection by making the thermal sleeve into a double tube structure. By adding double the thermal sleeve B14e arranged on the outer periphery of the thermal sleeve 14, convection formation can be suppressed by this alone, and convection formation can be suppressed by the ribs 14a, 14b, 14f thereon.

  As described above, when the gap in the annular flow path between the water supply nozzle and the thermal sleeve is ensured and at least one or more axially extending rib mechanisms are installed on the inner and outer surfaces of the thermal sleeve, A narrow gap is formed as if the inner surface of the water supply nozzle and the outer surface of the thermal sleeve are in contact with each other. In this gap portion, the heat transfer is changed from natural convection heat transfer to heat transfer even between the low temperature water supply and the high temperature reactor water. No stratification occurs. Even if thermal stratification occurs, natural convection heat transfer is reduced, and as a result, the temperature fluctuation of the fluid is abruptly attenuated on the inner surface of the water supply nozzle, thereby reducing the fear of thermal fatigue.

The relationship between the inner surface of the water supply nozzle and the rib mechanism in each of the embodiments shown in FIGS. 8 to 11 is also the distance between the flow paths between the inner surface of the water supply nozzle and the protruding end protruding toward the inner surface of the water supply nozzle of the rib mechanism. and [delta], the inner diameter of the water supply nozzles and D _i, it is preferable that the relationship between the inner diameter and the spacing as is δ / D _i ≦ 0.03 to reduce the natural convection heat transfer coefficient.

  FIG. 12 shows a spiral projection mechanism 23 wound around the outer surface of the thermal sleeve 14 in order to reduce the gap. Here, the pressure in the water supply system is held by the original thermal sleeve 14, and the spiral protrusion mechanism 23 is for reducing the gap δ between the nozzle and the thermal sleeve. Of course, this mechanism can be used with a softer structure than the thermal sleeve, and by simply adding the mechanism to the conventional thermal sleeve, almost no modification is required and it can be easily handled as a water supply nozzle during increased output operation. Become. FIG. 13 shows another embodiment of the above figure, which is a screw-like projection mechanism 24. This may be either an integral structure with the thermal sleeve 14 or a separate structure attached. As a result, the gap δ between the normal nozzle and the thermal sleeve can be reduced, and there is an effect of suppressing temperature fluctuation due to thermal stratification without accompanying a significant structural change.

Regarding the small gap δ in each of the embodiments shown in FIGS. 12 and 13, it is preferable that the relationship between the inner surface of the water supply nozzle and the helical protrusion mechanism 23 or the screw-like protrusion mechanism 24 is also the inner surface of the water supply nozzle. and the distance between the flow path between the tip which protrudes into the inner surface side of the water supply nozzle of the spiral projection mechanism 23 or screw like projection mechanism 24 and [delta], the inner diameter of the water supply nozzles and D _i, and the inner diameter and the interval It is preferable to reduce the natural convection heat transfer coefficient such that δ / D _i ≦ 0.03.

  Further, if a thermal buffer material is packed in the gap portion in order to prevent the occurrence of thermal stratification in the gap, there is no flow of the reactor water in the gap, and the temperature fluctuation suppressing effect is further increased. This thermal buffer material has at least one or more multilayer structures and does not become a stress boundary due to thermal deformation.

  The spiral projection mechanism 23 or the screw projection mechanism 24 is a spiral member that is wound around or integrated with the outer peripheral surface of the thermal sleeve. The member is mounted on the outer peripheral surface of the thermal sleeve concentrically with the thermal sleeve. An annular member may be used.

  FIG. 14 shows a plate-like guide mechanism 25 that suppresses the disturbance contained in the downward flow of the reactor water from flowing into the annular flow path, and opens a gap corresponding to the degree of inflow suppression at the water supply outlet of the water supply nozzle. In addition, it is provided facing the water supply outlet. Even if thermal stratification occurs, temperature fluctuation does not occur as long as the stable stratification interface remains, so high cycle thermal fatigue can be suppressed. In this embodiment, the guide mechanism 25 is installed on the outer surface of the water supply sparger, but the same effect can be obtained even if the mechanism is installed on the inner wall surface of the reactor pressure vessel 1. The plate shape of the guide mechanism 25 may be a disk shape or a rectangular shape.

  The embodiment of FIG. 14 is implemented in combination with the other embodiments of the present invention, so that there is less concern about thermal fatigue of the water supply nozzle portion than when the other embodiments are used alone.

  As described above, if the existing water supply nozzle of BWR is replaced with the water supply nozzle of the present invention and the increased output operation is performed by the thermal balance shift method, even if the water supply temperature is lower than the conventional water supply nozzle, Therefore, it becomes an effective nuclear system capable of increasing the electric output by about 10 to 20% compared with the current plant operation.

  In addition, although the present Example showed the boiling water type light water reactor plant as an example, this invention is applicable also to the secondary system of a pressurized water type light water reactor, and other types of nuclear power generation systems.

Thus, in an embodiment of the present invention, in order to achieve the object of the present invention, first, the gap in the annular flow path between the water supply nozzle and the thermal sleeve is set to a natural convection heat transfer coefficient of 900 W / Reduce to less than m ² K. Thereby, even if thermal stratification occurs between the low-temperature feed water and the high-temperature reactor water, the heat transfer rate to the inner surface of the feed water nozzle is small, and the temperature fluctuation on the inner surface of the feed water nozzle is small. Thereby, material soundness due to thermal fatigue due to temperature fluctuation can be ensured.

  Further, in an embodiment, after securing a gap in the annular flow path between the water supply nozzle and the thermal sleeve, one or more axially extending rib mechanisms are installed on the inner and outer surfaces of the thermal sleeve. . As a result, a narrower portion is formed so that the inner surface of the water supply nozzle and the outer surface of the thermal sleeve are in contact with each other. In this gap portion, natural convection heat transfer is changed to heat conduction, for example, between low-temperature water supply and high-temperature reactor water. But thermal stratification does not occur. Even if thermal stratification occurs, natural convection heat transfer is reduced, and as a result, the temperature fluctuation of the fluid is abruptly attenuated on the inner surface of the water supply nozzle, thereby reducing the fear of thermal fatigue.

  In an embodiment of the present invention, a new reactor is provided with a function of lowering the feed water temperature in advance, so that an electric power supply can be operated during operation or every operation cycle without giving excessive design margin to the high-pressure plant equipment. It is possible to provide a nuclear power generation system that makes it possible to change the output.

  In addition, when adopting the reactor operation method based on the thermal balance shift of the existing boiling water reactor or the improved boiling water reactor, the water supply nozzle according to each of the above embodiments is connected to the reactor pressure of the reactor water supply system. By incorporating it as a water supply nozzle used for connection to the container to form an increased power nuclear power generation system, it is possible to overcome the deterioration of the soundness of the water supply nozzle part due to its operation, and to allow the operation method to be adopted.

  Further, in the embodiment of the present invention, the diameter of the thermal sleeve in the conventional water supply nozzle is increased without significantly changing the reactor system with respect to the increased output of the existing reactor, and the gap is reduced. Even when the operation is changed from normal operation to operation at increased output, the structure is such that there is no problem with thermal fatigue even if the temperature of the water supply flowing into the water supply nozzle decreases, and by installing a compact water supply nozzle and sleeve, While maintaining the design margin of the turbine and reducing the impact on the water supply system and the reactor internal structure, there is no impact on other plant equipment, and the steam flow into the low-pressure turbine is increased, thereby increasing the plant output. A possible nuclear power generation system can be provided.

  The present invention has application to a water supply nozzle connected to a reactor pressure vessel of a water supply system of a nuclear power generation system.

1 is a system diagram of a reactor facility (nuclear power generation system) that can employ a thermal balance shift method according to an embodiment of the present invention. It is sectional drawing of the water supply nozzle which is a suitable Example of this invention, the right figure is a figure which shows the cross section of the longitudinal direction of a water supply nozzle, and the left figure is AA sectional drawing of a right figure. It is a correspondence diagram of the temperature distribution of the water supply nozzle part which is an Example of this invention, and the water supply nozzle site | part which shows the temperature distribution. It is a figure explaining the temperature fluctuation phenomenon of the water supply nozzle part which is an Example of this invention, the upper figure is sectional drawing of a water supply nozzle part, and the lower figure is a figure which shows the temperature fluctuation phenomenon in the AA cross section of the upper figure. The figure on the right side of the figure below shows when the water supply is stopped, and the figure on the left side shows the time of water supply during the rated operation of the reactor. It is a temperature fluctuation attenuation characteristic figure with respect to the heat transfer rate of the water supply nozzle part which is an Example of this invention. It is a figure of the evaluation flow of the water supply nozzle which is an Example of this invention. It is a comparison figure of the cumulative damage coefficient of the water supply nozzle which is an Example of the present invention. It is sectional drawing of the water supply nozzle which is the other Example of this invention, the right figure is a figure which shows the cross section of the longitudinal direction of a water supply nozzle, and the left figure is AA sectional drawing of a right figure. It is sectional drawing of the water supply nozzle which is further another Example of this invention, the right figure is a figure which shows the cross section of the longitudinal direction of a water supply nozzle, and the left figure is AA sectional drawing of a right figure. It is sectional drawing of the water supply nozzle which is further another Example of this invention, The right figure is a figure which shows the cross section of the longitudinal direction of a water supply nozzle, The left figure is AA sectional drawing of a right figure. It is sectional drawing of the water supply nozzle which is still another Example of this invention, the right figure is a figure which shows the cross section of the longitudinal direction of a water supply nozzle, and the left figure is AA sectional drawing of a right figure. It is the schematic of the water supply nozzle which is still another Example of this invention. It is the schematic of the water supply nozzle which is another Example of this invention. It is a schematic sectional drawing of the water supply nozzle which is further another Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Main steam pipe, 3 ... High pressure turbine, 4 ... Moisture separator, 5 ... Low pressure turbine, 6 ... Condenser, 7 ... Low pressure feed water heater, 8 ... Main feed water pump, 9 ... high-pressure feed water heater,
DESCRIPTION OF SYMBOLS 10 ... Extraction flow adjustment valve, 11 ... Feed water bypass pipe, 12 ... Feed water piping, 13 ... Feed water nozzle,
13a: Water supply nozzle inner surface, 13b: Water supply nozzle upper portion, 13c: Water supply nozzle lower portion, 14 ... Thermal sleeve, 14a ... Thermal sleeve outer surface, 14b ... Thermal sleeve inner surface, 14c ... Tube outer rib, 14d ... Tube inner rib, 14e ... Thermal sleeve B, 14f ... tube outer rib B,
DESCRIPTION OF SYMBOLS 15 ... Water supply sparger, 16 ... Annular flow path (gap), 17 ... Water supply, 18 ... Reactor water, 19 ... Thermal stratification interface, 20a ... Natural convection vortex in the annular flow path, 20b ... Natural convection vortex in the thermal sleeve, 21 ... heat input, 22 ... temperature fluctuation occurrence location, 23 ... spiral projection mechanism, 24 ... screw projection mechanism, 25 ... guide mechanism.

Claims (5)

In the water supply nozzle with a thermal sleeve inside,
The interval between the annular flow paths formed between the inner surface of the water supply nozzle and the outer surface of the thermal sleeve is δ, the inner diameter of the water supply nozzle is D _i , and the relationship between the interval and the inner diameter is δ / D _i. A water supply nozzle, wherein ≦ 0.03. In the water supply nozzle with a thermal sleeve inside,
A rib having a longitudinal direction in the longitudinal direction of the water supply nozzle or the thermal sleeve is provided between the inner surface of the water supply nozzle and the outer surface of the thermal sleeve and / or the inner surface of the thermal sleeve. Water nozzle to be used.   3. The water supply nozzle according to claim 2, wherein the thermal sleeve has a double structure including an inner thermal sleeve and an outer thermal sleeve arranged so as to surround an outer periphery of the inner thermal sleeve. . According to claim 2 or claim 3, the distance between the flow path between the tip which protrudes into the inner surface side of the water supply nozzle of the inner surface and the ribs of the water supply nozzle and [delta], the inner diameter of the water supply nozzles and D _i The water supply nozzle is characterized in that the relationship between the interval and the inner diameter is δ / D _i ≦ 0.03. In the water supply nozzle with a thermal sleeve inside,
Bei example annular or helical member between the inner surface and the outer surface of the thermal sleeve of the water supply nozzles,
The interval of the flow path between the inner surface of the water supply nozzle and the annular or spiral member is δ, the inner diameter of the water supply nozzle is D _i , and the relationship between the interval and the inner diameter is δ / D _i ≦ 0. A water supply nozzle characterized by being 03 .

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