JP2016170047A - Reactor pressure vessel water level estimation device and reactor pressure vessel water level estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor reactor water level by mitigating burden of operators at an accident of nuclear reactor facilities.SOLUTION: A reactor pressure vessel water level estimation device 20 estimates a temporal change in the reactor pressure vessel water level. The reactor pressure vessel water level estimation device 20 includes: a decay heat determination part 22 for determining decay heat Q; a water injection state determination part 23 for determining density ρin and enthalpy Hin of injected water; an injected water flow determination part 24 for determining mass flow of injected water Win; a saturation state quantity determination part 25 for determining state quantity in saturation state; steam generation quantity calculation part 27 for calculating steam generation quantity Wg from the decay heat Q, the mass flow of injected water Win, the enthalpy Hin, the saturated water enthalpy Hf and evaporation latent heat Hfg; and a water level determination part 28 for determining reactor pressure vessel estimated water level on the basis of the mass flow of injected water Win, the steam generation quantity Wg and saturated water density ρs.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to a reactor pressure vessel water level estimation device and a reactor pressure vessel water level estimation method that estimate temporal changes in the water level in a reactor pressure vessel.

  Generally, as a method for measuring the reactor water level in a boiling water reactor (BWR), a technique for measuring the water level using a differential pressure is used. In this method, measuring nozzles are installed at the top and bottom of the reactor pressure vessel, and the water level is measured by measuring the differential pressure with a differential pressure gauge that communicates the upper side with the gas phase and the lower side with the liquid phase. To do. In this case, a condensing tank is provided in the line from the upper measurement nozzle to the differential pressure gauge to condense the steam and fill the instrumentation pipe to the differential pressure gauge with condensed water, thereby avoiding a water level fluctuation event in the instrumentation pipe. Reactor water level change is measured by obtaining the change in differential pressure by the pressure change in the lower nozzle part due to fluctuation.

JP-A-10-274554

  The reactor water level, that is, the water level in the reactor pressure vessel, is a process quantity directly related to the safe operation of the reactor facility, and is constantly monitored. In the event of a severe accident at the reactor facility, the water level cannot be measured due to the above-mentioned failure of the differential pressure gauge or the evaporation of water in the condensing tank due to boiling during decompression, and the reactor water level may not be monitored. There is. In fact, there is an example where the differential water pressure gauge cannot be measured due to the evaporation of water in the condensing tank and the reactor water level cannot be monitored during a serious accident.

  Also, for example, in Japan, when it is difficult to measure a parameter that needs to be monitored in order to deal with a serious accident, etc., a facility that can grasp effective information for estimating the parameter is available. It is stipulated that it must be provided. Thus, when the reactor water level cannot be measured, it is required to provide an estimation means using alternative parameters.

  Therefore, in the event of an accident at the reactor facility, the operator cannot measure the reactor water level as described above, or the increase in the reactor water level indication is small relative to the amount of water injected into the reactor. When there is a suspicion of water leaking from the vessel, the reactor water level is estimated from parameters such as reactor pressure, water injection volume, water injection temperature, etc. other than the reactor water level. However, it is difficult for the operator to collect the parameters that change from moment to moment and to calculate the water level by hand calculation when dealing with accidents that require urgency.

  The embodiment of the present invention has been made in consideration of such circumstances, and an object thereof is to enable monitoring of the reactor water level separately from the water level measurement by the water level gauge.

  In order to achieve the above-mentioned object, the present embodiment is provided in a water injection pipe that guides the water injection, a pressure measurement value by a pressure gauge provided in a reactor pressure vessel in which a reactor core is housed and water injection flows in and steam flows out. A reactor pressure vessel water level estimation device for estimating a temporal change in the coolant level of the reactor pressure vessel based on outputs of a temperature measurement value by a thermometer and a volume flow rate measurement value by a flow meter, respectively. , A decay heat determining unit for determining decay heat Q generated from the core for a time after receiving a reactor shutdown system operation signal, and a density ρin and enthalpy Hin of the water injection based on a measured value of the water injection temperature. A water injection state quantity determining unit to determine, a water injection flow rate determining unit for determining a water injection mass flow rate Win based on the volumetric flow rate measurement value V and the density ρin of the water injection, and the raw material based on the measurement value of the pressure gauge. Saturated water quantity enthalpy Hf, saturated water density ρs, and saturation state quantity determination unit for determining latent heat of evaporation Hfg in the liquid phase in the reactor pressure vessel, the decay heat Q, the injected water mass flow rate Win, A steam generation amount calculation unit for calculating the steam generation amount Wg of the steam from the enthalpy Hin, the saturated water enthalpy Hf and the latent heat of evaporation Hfg, the water injection mass flow rate Win, the steam generation amount Wg and the saturated water density ρs; And a water level determination unit for determining an estimated water level in the reactor pressure vessel based on the above.

  In addition, the present embodiment is a pressure measurement value by a pressure gauge provided in a reactor pressure vessel in which a reactor core is accommodated and water injection flows and steam flows out, and temperature measurement by a thermometer provided in a water injection pipe for introducing the water injection. A reactor pressure vessel water level estimation method for estimating a temporal change in the level of cooling water in the reactor pressure vessel based on the output of each of the flow value and the volume flow rate measurement value by a flow meter, the decay heat determining unit However, the decay heat determination step for determining the decay heat Q generated from the core for the time after receiving the reactor shutdown system operation signal, and the water injection state quantity determination unit, the volumetric flow rate measurement value V and the density ρin of the water injection A water injection state quantity determination step for determining the water injection mass flow rate Win based on the flow rate, and a saturated state quantity determination unit that saturates the water stored in the liquid phase in the reactor pressure vessel based on the measured value of the pressure gauge. The saturated state quantity determining step for determining Hf, saturated water density ρs, and latent heat of vaporization Hfg, and the steam generation amount calculating unit, the decay heat Q, the injected water mass flow rate Win, the enthalpy Hin, and the saturated water enthalpy A steam generation amount calculating step for calculating the steam generation amount Wg of the steam from Hf and the latent heat of evaporation Hfg, and a water level determination unit based on the water injection mass flow rate Win, the steam generation amount Wg, and the saturated water density ρs. And a water level determining step for determining an estimated water level in the reactor pressure vessel.

  According to the embodiment of the present invention, it becomes possible to monitor the reactor water level separately from the water level measurement by the water level gauge.

It is a longitudinal cross-sectional view which shows the structure around the reactor pressure vessel including the water level estimation apparatus in a reactor pressure vessel which concerns on 1st Embodiment. It is a block diagram which shows the structure of the water level estimation apparatus in a reactor pressure vessel which concerns on 1st Embodiment. It is a block diagram which shows the structure of the decay heat determination part of the water level estimation apparatus in a reactor pressure vessel which concerns on 1st Embodiment. It is a block diagram which shows the structure of the water injection state amount determination part of the water level estimation apparatus in a reactor pressure vessel which concerns on 1st Embodiment. It is a block diagram which shows the structure of the saturated water state determination part of the water level estimation apparatus in a reactor pressure vessel which concerns on 1st Embodiment. It is a block diagram which shows the content of the steam generation amount calculation part of the reactor pressure vessel water level estimation apparatus and water level determination part which concern on 1st Embodiment. It is a figure which shows the example of the screen display of the trend display of the measured value and estimated value of a reactor water level. It is a conceptual graph for demonstrating the correction method of the estimated value based on the measured value of the reactor water level. It is a flowchart which shows the procedure of the water level estimation method in a reactor pressure vessel which concerns on 1st Embodiment. It is a block diagram which shows the structure of the water level estimation apparatus in a reactor pressure vessel which concerns on 2nd Embodiment. It is a block diagram which shows the structure of the water level estimation apparatus in the reactor pressure vessel which concerns on 3rd Embodiment.

  Hereinafter, a reactor pressure vessel water level estimation device and a reactor pressure vessel water level estimation method according to an embodiment of the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
Hereinafter, the present embodiment will be described using a BWR reactor facility as an example. FIG. 1 is a longitudinal sectional view showing a configuration around a reactor pressure vessel including a reactor pressure vessel water level estimation device according to a first embodiment. A reactor pressure vessel 2 that houses the reactor core 1 is provided, and a reactor containment vessel 3 that houses the reactor pressure vessel 2 is provided outside the reactor pressure vessel 2.

  A coolant 5 is included in the reactor pressure vessel 2. The coolant 5 is divided into a liquid phase part 5a and a gas phase part 5b. There is a liquid phase part 5 a in the lower part in the reactor pressure vessel 2, and a gas phase part 5 b in the upper part in the reactor pressure vessel 2.

  The liquid level 5c of the coolant 5, which is the interface between the liquid phase part 5a and the gas phase part 5b, is kept constant during normal operation. In order to monitor the level of the liquid level 5c, that is, the water level, a water level meter 4 is provided. The water level meter 4 is usually a differential pressure type. The liquid phase part 5a in the reactor pressure vessel 2 and the water level gauge 4 are connected by a pressure guiding tube that penetrates the reactor containment vessel 3 in an airtight manner. Similarly, the gas phase part 5b in the reactor pressure vessel 2 and the water level gauge 4 are connected by a pressure guiding tube that penetrates the reactor containment vessel 3 in an airtight manner. A condensing tank 4a is provided in a portion of the pressure guiding tube from the gas phase portion 5b in the reactor containment vessel 3, and the height of the condensed water in the pressure guiding tube is kept constant. The water level gauge 4 is provided in a reactor building (not shown) outside the reactor containment vessel 3.

  In order to measure the pressure in the gas phase part 5b of the reactor pressure vessel 2, a pressure gauge 6 is provided. The pressure gauge 6 is provided outside the reactor containment vessel 3 and in the reactor building. The reactor pressure vessel 2 and the pressure gauge 6 are connected by a pressure guiding tube that penetrates the reactor containment vessel 3 in an airtight manner.

  A water injection pipe 7 is connected to the reactor pressure vessel 2. At the time of a serious accident in which the coolant in the reactor pressure vessel 2 is released into the reactor containment vessel 3, for example, cooling water stored in a storage tank (not shown) outside the reactor building is injected into the water injection pipe. 7 is injected into the reactor pressure vessel 2. The water injection pipe 7 is provided with a flow rate measuring element 8a such as a flow nozzle or a venturi, and the flow meter 8 outputs a flow rate signal due to the differential pressure. The water injection pipe 7 is provided with a thermometer 9 for measuring the temperature of the cooling water in the water injection pipe 7. The flow meter 8 and the thermometer 9 are provided outside the reactor containment vessel 3.

  The reactor pressure vessel 2 is provided with a steam pipe 10. In the case of a serious accident, for example, a steam path is supplied to a steam turbine (not shown) for driving a pump (not shown) that pumps cooling water.

  Note that a piping for supplying cooling water (not shown) is connected to the reactor pressure vessel 2 and serves as a path for supplying cooling water into the reactor pressure vessel 2 during normal operation. The cooling water supply pipe is a water supply pipe. At the time of a serious accident, the supply of cooling water from this normal cooling water supply pipe is stopped.

  Further, a piping for cooling water outflow (not shown) is connected to the reactor pressure vessel 2 and serves as a path through which cooling water flows out of the reactor pressure vessel 2 during normal operation. The piping for cooling water outflow is a main steam pipe in the case of BWR. At the time of a serious accident, the cooling water outflow from this normal cooling water outflow pipe is stopped.

  Therefore, in the state at the time of the accident, the supply of the cooling water from the normal cooling water supply pipe and the outflow of the cooling water from the normal cooling water outflow pipe need not be considered.

  The reactor pressure vessel water level estimation device 20 receives outputs from the pressure gauge 6, the flow meter 8, and the thermometer 9 to estimate the water level in the reactor pressure vessel 2. Further, the reactor pressure vessel water level estimation device 20 outputs the estimation result of the water level to the display device 30, and the display device 30 displays the estimation result.

  FIG. 2 is a block diagram showing the configuration of the reactor pressure vessel water level estimation apparatus 20 according to the first embodiment. The reactor pressure vessel water level estimation apparatus 20 includes a decay heat determination unit 22, a water injection state determination unit 23, a water injection flow determination unit 24, a saturation state determination unit 25, a water level storage unit 26, a steam generation amount calculation unit 27, and A water level determination unit 28 is provided.

  FIG. 3 is a block diagram showing a configuration of the decay heat determination unit 22 of the reactor pressure vessel water level estimation device 20. The decay heat determination unit 22 has a built-in clock 22a and receives a signal indicating that a reactor shutdown signal, which is an operation signal of a reactor shutdown system (not shown), is issued, and the time from when the reactor shuts down. Count. Moreover, the decay heat determination part 22 has the decay heat table 22b which matches the time after a nuclear reactor stop, and the decay heat Q. FIG. In this manner, the decay heat determination unit 22 determines the value of the decay heat Q generated from the core fuel after receiving the reactor shutdown signal.

  Note that the signal indicating that the reactor shutdown signal, which is the operation signal of the reactor shutdown system, is not necessarily required to be the reactor shutdown system signal. The clock 22a may be manually started by an operator, for example.

  Alternatively, when the reactor pressure vessel water level estimation device 20 is to be started when a considerable time has elapsed after the reactor shutdown, the elapsed time after the reactor shutdown at that time is input. Also good. In this case, it is considered that the inventory of the cooling water in the reactor pressure vessel 2 has changed from the normal operation state due to a transient event after the reactor shutdown, but by correcting this change, The subsequent water level can be estimated. In this case, the change in the initial inventory of a typical event is evaluated in advance by analysis or the like, stored in the memory in the reactor pressure vessel water level estimation device 20, and a value for the corresponding event is extracted. It can be used for correction.

  FIG. 4 is a block diagram showing a configuration of the water injection state quantity determination unit 23 of the reactor pressure vessel water level estimation device 20. The water injection state quantity determination unit 23 associates the compressed water density table 23a that associates the value of the compressed water density ρin with the value of the temperature of injected water, which is compressed water, and the value of the enthalpy Hin of the compressed water with respect to the temperature value. It has a compressed water enthalpy table 23b.

  For compressed water, since the influence of pressure is small, for example, the density and enthalpy of compressed water in the case of the pressure value on the outlet side of a pump (not shown) that pumps cooling water in the water injection pipe 7 are also errors. Is not big. The water injection state quantity determination unit 23 receives the temperature signal from the thermometer 9 provided in the water injection pipe 7, and cools down the water injection pipe 7 based on the compressed water density table 23 a with respect to the water injection temperature Tin. The density ρin of water is determined, and the enthalpy Hin of the cooling water flowing through the water injection pipe 7 is determined based on the compressed water enthalpy table 23b.

The water injection flow rate determination unit 24 receives the flow signal from the flow meter 8 provided for measuring the flow rate in the water injection pipe 7 and changes the water injection volume flow rate Gin to the water injection mass flow rate Win as shown in the following equation (1). Convert. The conversion to the water injection mass flow rate Win uses the water density ρin determined by the water injection state determining unit 23.
Win = ρin · Gin (1)

  FIG. 5 is a block diagram showing a configuration of the saturation state quantity determination unit 25 of the reactor pressure vessel water level estimation device 20. The saturated state quantity determination unit 25 includes a saturated water density table 25a, a saturated water enthalpy table 25b, and a saturated water evaporation latent heat table 25c.

  The saturated water density table 25a associates the saturated water density ρs with the saturation pressure Ps. The saturated water enthalpy table 25b makes the saturated water enthalpy Hf of the saturated water correspond to the saturation pressure Ps. The saturated water evaporation latent heat table 25c associates the evaporation latent heat Hfg with the saturation pressure Ps.

  FIG. 6 is a block diagram illustrating the contents of the steam generation amount calculation unit 27 and the water level determination unit 28 of the reactor pressure vessel water level estimation apparatus 20.

  The steam generation amount calculation unit 27 includes decay heat Q from the decay heat determination unit 22, density ρin and enthalpy Hin of water injection from the water injection state determination unit 23, water injection mass flow rate Win from the water injection flow determination unit 24, and saturation state The saturated water density ρs, saturated water enthalpy Hf and latent heat of vaporization Hfg from the quantity determining unit 25 are received as inputs.

The steam generation amount calculation unit 27 calculates the steam generation amount Wg based on the following equation (2) using these inputs.
Wg = [Q−Win (Hf−Hin)] / Hfg (2)

  Expression (2) is an expression that assumes a model in which the cooling water retained in the reactor pressure vessel 2 is sequentially completely mixed with the incoming water injection. Strictly speaking, the inside of the reactor pressure vessel 2 is in a subcooled state in the vicinity of the water injection, and complete mixing is a virtual state. First of all, however, it is important to be able to monitor changes in the water level with a simple model. In addition, a simple model is used because there is a means for improving the accuracy including the correction described later. Note that a two-point model of a subcool region and an evaporation region can also be used.

  The water level determination unit 28 includes a water level calculation unit 28a, a volume water level conversion table 28b, and a correction unit 28c. The volume water level conversion table 28b is a table for associating the volume occupied by water with the water level when the space in the reactor pressure vessel 2 is filled with water from the lower side. The volume may be a volume for a height higher than the assumed minimum level. Alternatively, on the basis of the operation reference water level, a volume lower than this water level may be a negative volume, and a volume higher than this water level may be a positive volume.

The water level determination unit 28 receives the steam generation amount Wg from the steam generation amount calculation unit 27, the injected water mass flow rate Win from the injected water flow rate determination unit 24, and the saturated water density ρs from the saturated state amount determination unit 25 as inputs. The water level calculation unit 28a calculates the amount of change in the retained mass M of the saturated water in the reactor pressure vessel 2 over time Δt based on the following equations (3) and (4).
dM / dt = Win−Wg (3)
ΔM = (dM / dt) × Δt (4)

Next, the water level calculation unit 28a converts the retained mass change ΔM of the saturated water into the retained volume change by the following equation (5), adds the previous saturated water retained volume Vn, and after Δt has elapsed. The new saturated water holding volume V _{n + 1} is calculated.
V _{n + 1} = V _n + ΔM / ρs (5)

Next, the water level calculation unit 28a estimates the water level in the reactor pressure vessel 2 corresponding to the volume Vn + 1 in the reactor pressure vessel 2 based on the following equation (6), that is, based on the volume water level conversion table 28b. Determine the value.
L = L (V) (6)

  Thus, the reactor pressure vessel water level estimation apparatus 20 according to the present embodiment can estimate the water level in the reactor pressure vessel 2 independently of the water level measurement by the water level gauge 4.

  FIG. 7 is a diagram illustrating an example of a screen display of the trend display of the measured value and estimated value of the reactor water level. The display device 30 displays such a trend. The estimated value is indicated by a solid line in the display of FIG. In addition, when the water level gauge 4 is healthy and can transmit a water level signal, the water level measurement value based on the signal of the water level gauge 4 is also displayed as indicated by a broken line, thereby causing an abnormality in the state of the water level gauge 4 You can confirm that you have not.

  The correction unit 28c (FIG. 6) accepts the determination result of the estimated water level of the water level determination unit 28 and the trend of the measurement result of the water level meter 4 from the water level storage unit 26. The correction unit 28c performs correction when receiving a correction command from the outside.

  FIG. 8 is a conceptual graph for explaining a method of correcting the estimated value based on the measured value of the reactor water level. In FIG. 8, a curved line A indicated by a broken line is a measurement result of the water level meter 4 from the water level storage unit 26. A curve B indicated by a solid line is a result of determination of the estimated water level by the water level determination unit 28. Now, it is assumed that there are two locations A1 and A2 that have characteristic changes in the curve A. Similarly, it is assumed that there are two locations B1 and B2 that are considered to correspond to A1 and A2 of the curve A at locations where characteristic changes occur in the curve B. Such a location corresponds to the height at which the cross-sectional area in the reactor pressure vessel 2 changes suddenly.

  As shown in FIG. 8, the time and water level at each location are expressed by combinations in parentheses, and A1 (tA1, LA1), A2 (tA2, LA2), B1 (tB1, LB1), B2 (tB2, LB2 ). A vector directed from the point A1 to the point A2 indicated by a two-dot chain line is a vector AA, and a vector directed from the point B1 to the point B2 indicated by a dashed-dotted line is a vector BB.

  When the directions and magnitudes of the vector AA and the vector BB coincide, that is, when one of them is translated and overlapped with the other, the time and the water level are only shifted. In this case, the curve A and the curve B match if they are corrected so as to shift each.

  When only the horizontal axis component of both vectors, that is, the time axis component is different and the horizontal axis component of the vector BB is larger than the horizontal axis component of the vector AA, the change in the estimated water level matches the tendency of the change in the actual water level. However, this is a change that is delayed in time. In this case, for example, the curve of the volume / water level conversion table 28b can be maintained and the correction can be made by setting the volume V on the horizontal axis to a small value or the vertical axis to a large value.

  Similarly, when only the horizontal axis, that is, the time axis component, of both vectors is different, for example, the curve of the volume water level conversion table 28b can be maintained and the scale of the vertical axis can be changed.

  In the case of the combination of the above cases, correction can be made by combining scale change and shift.

  Further, not only at the time of an accident at a nuclear reactor facility, but also during a normal shutdown, the water level measurement result of the water level gauge 4 and the water level estimation result by the water pressure estimation device 20 in the reactor pressure vessel are displayed and compared, thereby making the reactor It is possible to grasp the estimation accuracy of the pressure vessel water level estimation device 20. Or when deviation | shift is large, the improvement of the estimation precision of the reactor pressure vessel water level estimation apparatus 20 can be aimed at by grasping the cause and taking a countermeasure.

  FIG. 9 is a flowchart showing the procedure of the method for estimating the water level in the reactor pressure vessel according to the first embodiment. First, the following steps are repeated at a time interval of Δt until the end determination is made after a signal indicating that the reactor has stopped is started.

  First, the decay heat determination unit 22 starts time counting (step S01), and determines the decay heat at the time t (step S02). Next, based on the signal of the water injection temperature Tin from the thermometer 9, the water injection state quantity determining unit 23 determines the water injection density ρin and the water injection enthalpy Hin (step S03). Next, based on the measured value of the water injection volume flow rate Gin, the water injection flow rate determination unit 24 determines the water injection mass flow rate Win (step S04). Further, based on the saturation pressure Ps, the saturation state amount determination unit 25 determines the density ρs of saturated water, the saturated water enthalpy Hf, and the latent heat of evaporation Hfg (step S05).

  Here, step S04 needs to be after step S03, but the order of these, step S02, and step S05 is not limited.

  Next, the water level calculation unit 28a of the steam generation amount calculation unit 27 calculates the steam generation amount Wg based on the decay heat Q, the water injection mass flow rate Win, the enthalpy Hin, the saturated water enthalpy Hf, and the latent heat of evaporation Hfg (step S06). ).

  Next, the water level determination unit 28 receives the steam generation amount Wg from the steam generation amount calculation unit 27, the water injection mass flow rate Win from the water injection flow rate determination unit 24, and the saturated water density ρs from the saturation state amount determination unit 25, An estimated water level is determined (step S20).

  Specifically, first, the mass change amount ΔM in the reactor pressure vessel 2 at the time interval Δt is calculated based on the injected water mass flow rate Win and the steam generation amount Wg (step S07). Based on this, the volume V of water in the reactor pressure vessel 2 is calculated (step S08), and an estimated value of the water level L in the reactor pressure vessel 2 is determined from the volume V using a volume level conversion table (step S08). Step S09).

  Thereafter, an end determination is made (step S10), and if not ended (NO in step S10), step S02 is started at a timing of t + Δt from the previous time t, and step S02 and subsequent steps are repeated. Moreover, if it determines with complete | finishing (step S10 YES), it will complete | finish. Note that the time interval Δt may be a long time interval gradually because the change in the event becomes gradual as time elapses from the reactor shutdown.

  Thus, according to the water level estimation method in the reactor pressure vessel according to the present embodiment, the water level in the reactor pressure vessel 2 can be estimated independently of the water level measurement by the water level gauge 4.

  As described above, the reactor pressure vessel water level estimation device 20 and the reactor pressure vessel water level estimation method according to the present embodiment can reduce the load on the operator even in the event of an accident at the reactor facility. The reactor water level can be monitored.

[Second Embodiment]
FIG. 10 is a block diagram illustrating a configuration of a reactor pressure vessel water level estimation apparatus according to the second embodiment. This embodiment is a modification of the first embodiment. The second embodiment is a case where the leakage amount from the reactor pressure vessel 2 can be grasped for some reason. The case where the amount of leakage can be grasped is, for example, the case where the water level leaks to a specific location such as a sump pit and the water level of the cooling water accumulated at that location can be grasped. Or it is a case where it leaks out of the system via the piping part which has a flow meter.

In this case, when the leakage amount per unit time is W _L, the water level calculation section 28a of the water level determination unit 28, instead of the equation (3) of the first embodiment, calculates a ΔM by the following equation (7) To do.
dM / dt = (Win−Wg−W _L ) / ρs (7)
As a result, the estimation accuracy is further improved.

[Third Embodiment]
FIG. 11 is a block diagram showing a configuration of a reactor pressure vessel water level estimation apparatus according to the third embodiment. This embodiment is a modification of the first embodiment. The third embodiment is a case where the accuracy of the water pressure estimating device 20 in the reactor pressure vessel can be ensured to some extent and the water level meter 4 is healthy. The reactor pressure vessel water level estimation apparatus 20 according to the present embodiment further includes a leakage amount estimation unit 29.

  In this case, the measurement result by the water level meter 4 is necessarily higher than the estimation result of the transition by the reactor pressure vessel water level estimation device 20. Therefore, the leakage amount estimation unit 29 can grasp the transition of the leakage amount by calculating this difference as the leakage amount.

[Other Embodiments]
As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. For example, if the same light water cooled nuclear reactor, such as a pressurized water reactor (PWR), the water level can be estimated basically by the same apparatus or method as in the embodiment. However, since the pressure level of the PWR is measured by the pressurizer, the calibration part may not be applicable.

  Moreover, you may combine the characteristic of each embodiment. Furthermore, these embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Core, 2 ... Reactor pressure vessel, 3 ... Reactor containment vessel, 4 ... Water level meter, 4a ... Condensing tank, 5 ... Coolant, 5a ... Liquid phase part, 5b ... Gas phase part, 5c ... Liquid level, DESCRIPTION OF SYMBOLS 6 ... Pressure gauge, 7 ... Water injection piping, 8 ... Flow meter, 8a ... Flow measurement element, 9 ... Thermometer, 10 ... Steam piping, 20 ... Reactor pressure vessel water level estimation apparatus, 22 ... Decay heat determination part, 22a ... clock, 22b ... decay heat table, 23 ... water injection state quantity determining unit, 23a ... compressed water density table, 23b ... compressed water enthalpy table, 24 ... water injection flow rate determining part, 25 ... saturation state quantity determining part, 25a ... saturated water Density table, 25b ... saturated water enthalpy table, 25c ... saturated water evaporation latent heat table, 26 ... water level storage unit, 27 ... steam generation amount calculation unit, 28 ... water level determination unit, 28a ... water level calculation unit, 28b ... volume level conversion table , 28c ... corrector, 2 ... leakage amount estimating unit, 30 ... display unit

Claims (6)

Pressure measured by a pressure gauge installed in a reactor pressure vessel in which water is injected and steam flows out while containing the core, temperature measured by a thermometer installed in a water injection pipe for guiding the water injection, and volume flow by a flow meter A reactor pressure vessel water level estimation device that estimates temporal changes in the coolant level of the reactor pressure vessel based on the output of each measured value,
A decay heat determining unit for determining decay heat Q generated from the core for a time after receiving a reactor shutdown system operation signal;
A water injection state determination unit that determines the density ρin and enthalpy Hin of the water injection based on the measured value of the temperature of the water injection;
A water injection flow rate determining unit for determining a water injection mass flow rate Win based on the volumetric flow rate measurement value V and the density ρin of the water injection;
A saturated state quantity determining unit that determines the saturated water enthalpy Hf, the saturated water density ρs, and the latent heat of vaporization Hfg of the retained water in the liquid phase in the reactor pressure vessel based on the measured value of the pressure gauge;
A steam generation amount calculation unit for calculating the steam generation amount Wg of the steam from the decay heat Q, the injected water mass flow rate Win, the enthalpy Hin, the saturated water enthalpy Hf and the latent heat of evaporation Hfg;
A water level determination unit that determines an estimated water level in the reactor pressure vessel based on the water injection mass flow rate Win, the steam generation amount Wg, and the saturated water density ρs;
An apparatus for estimating a water level in a reactor pressure vessel, comprising: The said steam generation amount calculation part calculates the steam generation amount Wg of the said steam with the following formula | equation, The water level estimation apparatus in a reactor pressure vessel of Claim 1 characterized by the above-mentioned.
Wg = [Q-Win (Hf-Hin)] / Hfg   When the water level meter for measuring the water level in the reactor pressure vessel is healthy, the correction unit corrects the estimated water level based on the difference between the temporal change in the water level by the water level meter and the temporal change in the estimated water level. The apparatus for estimating a water level in a reactor pressure vessel according to claim 1 or 2, further comprising:   When the water level meter for measuring the water level in the reactor pressure vessel is healthy, the leakage amount of the cooling water from the reactor pressure vessel is estimated based on the difference between the water level by the water level meter and the estimated water level The apparatus for estimating a water level in a reactor pressure vessel according to any one of claims 1 to 3, further comprising a leakage amount estimating unit. Pressure measured by a pressure gauge installed in a reactor pressure vessel in which water is injected and steam flows out while containing the core, temperature measured by a thermometer installed in a water injection pipe for guiding the water injection, and volume flow by a flow meter A reactor pressure vessel water level estimation method for estimating a temporal change in the level of cooling water in the reactor pressure vessel based on the output of each measured value,
Decay heat determining unit determines decay heat Q generated from the core for a time after receiving a reactor shutdown system operation signal;
A water injection state quantity determining unit that determines a water injection mass flow rate Win based on the volume flow rate measurement value V and the density ρin of the water injection;
A saturated state quantity determination unit determines a saturated water enthalpy Hf, saturated water density ρs, and latent heat of evaporation Hfg of retained water in the liquid phase in the reactor pressure vessel based on a measurement value of the pressure gauge. Steps,
A steam generation amount calculation unit calculates a steam generation amount Wg of the steam from the decay heat Q, the water injection mass flow rate Win, the enthalpy Hin, the saturated water enthalpy Hf, and the latent heat of vaporization Hfg. Steps,
A water level determining step in which a water level determining unit determines an estimated water level in the reactor pressure vessel based on the injected water mass flow rate Win, the steam generation amount Wg, and the saturated water density ρs;
A method for estimating the water level in a reactor pressure vessel, comprising: The water level determining step includes:
A mass change amount calculating step in which the water level determining unit calculates a mass change amount ΔM in the reactor pressure vessel at a predetermined time interval based on the injected water mass flow rate Win and the steam generation amount Wg;
A volume calculating step in which the water level determining unit calculates a volume V of water in the reactor pressure vessel based on the mass change amount ΔM and the saturated water density ρs;
The water level determining unit determines an estimated value of the water level in the reactor pressure vessel from the volume using a volume water level conversion table;
The method for estimating a water level in a reactor pressure vessel according to claim 5, wherein:

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