Rod bundle channel boron transport measurement system

Abstract

The present invention provides a rod cluster channel boron transport measurement system, which relates to the field of nuclear reactor research and measurement technology and is designed to address the lack of research on the impact of two-phase mixing on boron transport. The system comprises a sub-channel rod cluster experimental section, a mixer, a water branch, an air branch, and a boric acid injection branch. The sub-channel rod cluster experimental section includes n sub-channel rods, where n is a natural number ≥ 2. A connecting area is provided between adjacent sub-channel rods. The mixer is connected to the bottom of the sub-channel rods, and the water branch, air branch, and boric acid injection branch are all connected to the mixer. The rod cluster channel boron transport measurement system provided by the present invention can simulate the mixing of coolant between sub-channels in a reactor and measure the impact of sub-channel mixing on boron transport.

Description

Technical Field

[0001] The present invention relates to the technical field of research and measurement of nuclear reactors, and in particular to a rod bundle channel boron transport measurement system. Background Art

[0002] Boron (B 10 ) elements, due to their large neutron absorption cross-section, affect the neutron flux in the reactor core. Typically, during long-term reactor operation, boron (in the form of boric acid) is required to control changes in core reactivity. Therefore, accurately determining the distribution of boron in different regions of the core is crucial for accurately regulating and controlling reactor power.

[0003] The reactor core is composed of multiple open subchannels (four fuel rods form one subchannel), including fuel rods. The open channels formed by the fuel rod bundles cause the coolant to exchange momentum and energy between adjacent subchannels, a phenomenon known as subchannel mixing. The causes of subchannel two-phase mixing include pressure-differential-driven lateral flow mixing, cavitation drift, and turbulent mixing. As the coolant exchanges energy and mass under the action of subchannel mixing, the boron concentration varies within different subchannels. Therefore, to accurately determine the distribution of boron within different subchannels, it is necessary to clarify the effects of lateral flow mixing, cavitation drift, and turbulent mixing on boron transport.

[0004] Currently, a large number of studies are still focused on the single-phase turbulent exchange between sub-channels. The mixing coefficient β is used to express the degree of mixing, and experimental research on the turbulent mixing coefficient mainly measures the turbulent mixing rate, usually based on the mass balance method (tracer method) and the energy balance method (thermal diffusion coefficient method). Among them, the mass balance method calculates the effective value of the turbulent mixing rate by measuring the change in the tracer concentration along the axial direction in the sub-channel, while the energy balance method uses a heating rod to heat the coolant in the surrounding sub-channels, and measures the temperature of the coolant in each sub-channel at different distances downstream or at the outlet, thereby calculating the turbulent mixing amount between the sub-channels.

[0005] As previously mentioned, during normal operation of a pressurized water reactor (PWR), two-phase mixing occurs between subchannels. This phenomenon is caused not only by turbulent mixing but also by pressure-differential-driven lateral mixing and cavitation drift. Turbulent mixing of two phases is more complex than single-phase turbulent mixing and is related to the cavitation fraction of each phase. However, research on this phenomenon is scarce, and it is unclear how lateral mixing, cavitation drift, and turbulent mixing affect boron transport. Summary of the Invention

[0006] The first object of the present invention is to provide a rod bundle channel boron transport measurement system to solve the technical problem in the prior art of insufficient research on the influence of two-phase mixing on boron transport.

[0007] The rod bundle channel boron transport measurement system provided by the present invention includes a sub-channel rod bundle experimental section, a mixer, a water branch, an air branch and a boric acid injection branch. The sub-channel rod bundle experimental section includes n sub-channel rods, where n is a natural number ≥2. A connecting area is provided between adjacent sub-channel rods. The mixer is connected to the bottom of the sub-channel rods, and the water branch, the air branch and the boric acid injection branch are all connected to the mixer.

[0008] The beneficial effects of the rod bundle channel boron transport measurement system of the present invention are:

[0009] By installing multiple subchannel rods, the area between fuel rods in an actual reactor can be simulated. Connecting the rods only through the connecting area, the rods can control subchannel mixing to a smaller area, allowing for more precise measurement of the subchannel mixing area and reducing the influence of other factors, such as gravity. Furthermore, by connecting water branches, gas branches, and boric acid injection branches to the mixer, the conditions in an actual nuclear reactor, where boric acid-containing coolant absorbs heat from the fuel rods and generates bubbles, can be simulated for experimental purposes.

[0010] In a preferred technical solution, each of the sub-channel rods is provided with at least two sampling ports of different heights, and each of the sampling ports is connected to an inductively coupled plasma mass spectrometer.

[0011] In a preferred technical solution, the rod bundle channel boron transport measurement system further comprises a high-speed camera, the high-speed camera is directed toward the connected area, and the material of the connected area is a transparent material.

[0012] In a preferred technical solution, the rod bundle channel boron transport measurement system further comprises a micro-pressure differential meter, which is connected to adjacent sub-channel rods at a position higher than the connecting area.

[0013] In a preferred technical solution, each of the sub-channel rods is provided with the mixer, and each of the mixers is independently connected to an air supply device and a liquid supply device.

[0014] In a preferred technical solution, each of the gas supply devices includes a first regulating valve, a gas flow meter and a first check valve arranged in series, and the first check valve is connected to the mixer.

[0015] In a preferred technical solution, the air branch circuit includes an air compressor, a second check valve, a buffer tank and a pressure reducing valve connected in series in sequence, and the outlet of the pressure reducing valve is connected to n first regulating valves.

[0016] In a preferred technical solution, each of the liquid supply devices includes a second regulating valve and a liquid flow meter arranged in series, and the liquid flow meter is connected to the mixer.

[0017] In a preferred technical solution, the water branch includes a water tank, a water pump and a water pressure gauge connected in series, and the outlet of the water pressure gauge is connected to n second regulating valves; the boric acid injection branch includes a boron-containing water tank, an injection pump and a check valve arranged in series in sequence, and the outlet of the check valve is connected to n second regulating valves.

[0018] In a preferred technical solution, the outlet of the water pump is further connected to the water tank via a stop valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the background technology, the following briefly introduces the drawings required for use in the embodiments or the background technology description. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0020] Figure 1 A schematic structural diagram of a rod bundle channel boron transport measurement system provided in an embodiment of the present invention;

[0021] Figure 2 A schematic structural diagram of a sub-channel rod bundle experimental section in a rod bundle channel boron transport measurement system provided by an embodiment of the present invention;

[0022] Figure 3 A schematic diagram of the structure of an inductively coupled plasma mass spectrometer for measuring boron concentration in a rod bundle channel boron transport measurement system provided by an embodiment of the present invention;

[0023] Figure 4 This is an image captured by a high-speed camera in the rod bundle channel boron transport measurement system according to an embodiment of the present invention;

[0024] Description of reference numerals:

[0025] 10-subchannel rod; 11-sampling port; 12-connecting area; 20-mixer; 31-air compressor; 32-second check valve; 33-buffer tank; 34-pressure reducing valve; 41-water tank; 42-water pump; 43-water pressure gauge; 44-stop valve; 51-boron-containing water tank; 52-injection pump; 53-check valve; 61-first regulating valve; 62-gas flowmeter; 63-first check valve; 71-second regulating valve; 72-liquid flowmeter; 91-floor drain. DETAILED DESCRIPTION

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] Example 1:

[0028] Figure 1 A schematic structural diagram of a rod bundle channel boron transport measurement system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the sub-channel rod bundle experimental section in the rod bundle channel boron transport measurement system provided by an embodiment of the present invention, wherein the local area where the connected area is located is partially enlarged, and below the locally enlarged image is a cross-sectional view of the cross section of the sub-channel rod where the connected area is located. Figure 1 and Figure 2 As shown, the rod bundle channel boron transport measurement system provided by the present invention includes a sub-channel rod bundle experimental section, a mixer 20, a water branch, an air branch and a boric acid injection branch. The sub-channel rod bundle experimental section includes n sub-channel rods 10, where n is a natural number ≥2. A connecting area 12 is provided between adjacent sub-channel rods 10, the mixer 20 is connected to the bottom of the sub-channel rods 10, and the water branch, the air branch and the boric acid injection branch are all connected to the mixer 20.

[0029] In this embodiment, n is 2. The corresponding communication region 12 is located between two adjacent sub-channel rods 10. In other implementations, n can be a natural number of 3, 4, 5, or even larger, depending on the number of sub-channels to be studied. For example, if adjacent fuel rods in a nuclear reactor are arranged in an equilateral triangle, n can be 3, with three sub-channel rods 10 arranged in an isosceles obtuse triangle with a vertex angle of 120°, and the communication region 12 located on both sides. Alternatively, n can be 4, with four sub-channel rods 10 arranged in a square, and the communication region 12 located on each side of the square.

[0030] Specifically, the internal cross-section of each sub-channel rod 10 is a chamfered cross, or what can be understood as a square with a quarter circle of equal size cut out from each of its four corners, with the two quarter circles not touching. Each quarter circle corresponds to a quarter of a fuel rod. Therefore, the internal space of each sub-channel rod 10 can simulate the space between fuel rods in a reactor.

[0031] The connecting area 12 is located in the upper-middle portion of adjacent sub-channel rods 10, and the mixer 20 is located at the bottom of each sub-channel rod 10. A return port is provided at the top of each sub-channel rod 10, through which the fluid flows to the floor drain 91 for subsequent processing. In an actual reactor, the fluid between the fuel rods absorbs heat from the fuel rods and flows upward. Therefore, the arrangement of the connecting area 12 and the mixer 20 fully simulates the actual flow conditions of fluid in a nuclear reactor.

[0032] By providing multiple subchannel rods 10, the area between fuel rods in an actual nuclear reactor can be simulated. Subchannel rods 10 are connected only through connecting regions 12, limiting subchannel mixing to a smaller area. This allows for more accurate measurement of the subchannel mixing area and reduces the influence of other factors, such as gravity. Furthermore, by connecting the water branch, the gas branch, and the boric acid injection branch to the mixer 20, the formation of bubbles caused by the boric acid-containing coolant absorbing heat from the fuel rods in an actual nuclear reactor can be simulated for experimental purposes.

[0033] like Figure 2 As shown, preferably, each sub-channel rod 10 is provided with at least two sampling ports 11 of different heights, and each sampling port 11 is connected to an inductively coupled plasma mass spectrometer (not shown in the figure).

[0034] It should be noted that each sub-channel rod 10 is provided with at least two sampling ports 11 of different heights, which means that the at least two sampling ports 11 in each sub-channel rod 10 are of different heights. However, the corresponding sampling ports 11 in each sub-channel rod 10 may be of the same height. For example, in the case of two sub-channel rods 10, each provided with two sampling ports 11, the lower sampling ports 11 of the two sub-channel rods 10 are of the same height, and the upper sampling ports 11 of the two sub-channel rods 10 are of the same height.

[0035] The inductively coupled plasma mass spectrometer can measure the boron concentration with an accuracy of ppb (parts per billion), which can meet the requirements for calculating the turbulent mixing rate. Figure 3 As shown, Figure 3 The horizontal axis is the actual weight of boron added to 1L of deionized water, while the vertical axis is the boron concentration measured by inductively coupled plasma mass spectrometry. It can be seen from the figure that the two match.

[0036] By measuring the boron concentration in the two sub-channel rods 10 and using the concentration balance equation, the turbulent mixing rate can be calculated.

[0037]

[0038] In the above equation, i and j represent the sub-channels in the two sub-channel rods 10, for example, Figure 2 The following table shows the sub-channel on the left, i represents the sub-channel on the right, j represents the sub-channel on the right, z represents the height in the sub-channel, and the corresponding m i and m j They represent the mass flow rates in the two sub-channels respectively. For example, Ci(z) represents, Figure 2The boron concentration at the z height of the left subchannel in the middle is in mg / L. W' represents the turbulent mixing rate, and the subscript letter behind it indicates the opposite direction, such as W' ij Indicates from Figure 2 The turbulent mixing rate of the flow from the left subchannel to the right subchannel is shown.

[0039] Since turbulent mixing does not cause a change in the net mass between adjacent sub-channels,

[0040] m i =m j

[0041] W' ij =W' ji =W (2)

[0042] Substitute formula (2) into (1):

[0043]

[0044] Since the heights of the sampling ports 11 in the two sub-channels are equal,

[0045] z=z1 C i (z) = C i (z1) C j (z) = C j (z1) (4)

[0046] z=z2 C i (z) = C i (z2) C j (z) = C j (z2) (5)

[0047] Substituting formula (4) and formula (5) into formula (3), we can obtain:

[0048]

[0049] For each sampling point, the mass flow rate m and the boron concentration C at different heights in each sub-channel are measured. i (z1), C i (z2), C j (z1), C j (z2) and the axial height z1 and z2, the turbulent mixing rate W' can be obtained by formula (6). Among them, the mass flow rate of the liquid phase in each sub-channel is kg / m 2 s is measured by the liquid flow meter 72 of the liquid phase branch. The unit of the axial height z1 and z2 is m. The sampling ports 11 corresponding to z1 and z2 are set at the upper and lower ends of the communication area 12.

[0050] By setting up inductively coupled plasma mass spectrometers at sampling ports at different heights, the boron concentration at different heights can be measured, and the turbulent mixing rate can be calculated, thereby obtaining the change in boron concentration caused by two-phase turbulent mixing.

[0051] Figure 4 This is an image captured by a high-speed camera in the rod bundle channel boron transport measurement system according to an embodiment of the present invention. Figure 4 As shown, preferably, the rod bundle channel boron transport measurement system further includes a high-speed camera (not shown in the figure), and the high-speed camera faces the connecting area 12, and the material of the connecting area 12 is a transparent material.

[0052] By setting a high-speed camera toward the connected area 12, the cavitation drift in the connected area 12 can be observed, that is, Figure 4 The phenomenon circled by the dotted ellipse in the middle connected area 12 can be used to analyze the effect of cavitation drift on boron concentration.

[0053] like Figure 2 As shown, preferably, the rod bundle channel boron transport measurement system further includes a micro-pressure differential meter, which is connected to adjacent sub-channel rods 10 at a position higher than the connecting area 12.

[0054] The two sub-channel rods 10 connected to the micro differential pressure gauge are at the same height to avoid a pressure difference caused by a height difference, which would cause measurement errors.

[0055] By setting a micro-differential pressure gauge at a position higher than the connecting area 12 and connecting adjacent sub-channel rods 10, the pressure difference of the solution of each sub-channel rod 10 above the connecting area 12 after lateral flow mixing can be measured, thereby obtaining the effect of lateral flow mixing on the boron concentration.

[0056] like Figure 1 and Figure 2 As shown, preferably, each sub-channel rod 10 is provided with a mixer 20, and each mixer 20 is independently connected to an air supply device and a liquid supply device.

[0057] It should be noted that each mixer 20 is independently connected to an air supply device and a liquid supply device. That is, taking two sub-channel rods 10 and each sub-channel rod 10 as an example, one mixer 20 is connected to an air supply device and a liquid supply device, and the other mixer 20 is connected to another air supply device and another liquid supply device. The air supply devices and liquid supply devices connected to the two mixers 20 are not mixed.

[0058] By providing a mixer 20 for each sub-channel rod 10 and independently connecting the gas supply device and the liquid supply device, the gas flow and liquid flow entering each mixer 20 can be controlled separately, so that in each mixer 20, two-phase working conditions consisting of different gas and liquid flow rates are mixed separately, and then boron transport under different two-phase working conditions is obtained in the sub-channel rod 10.

[0059] like Figure 1 As shown, preferably, each gas supply device includes a first regulating valve 61 , a gas flow meter 62 and a first check valve 63 arranged in series, and the first check valve 63 is connected to the mixer 20 .

[0060] Specifically, in this embodiment, the first regulating valve 61, the gas flow meter 62, and the first check valve 63 can be provided sequentially. Of course, in other implementations, the gas flow meter 62, the first regulating valve 61, and the first check valve 63 can also be connected in this order. Since the first regulating valve 61 and the gas flow meter 62 are connected in series, the flow rate through the first regulating valve 61 is necessarily the flow rate of the gas flow meter 62, and the gas flow meter 62 can still accurately reflect the flow rate of the gas supply device.

[0061] By arranging the first regulating valve 61 and the gas flowmeter 62 in series, the first regulating valve 61 can be used to adjust the gas flow rate in each gas supply device, thereby enabling multiple gas supply devices to have different gas flow rates to match the different liquid flow rates in the liquid supply device, thereby forming different two-phase operating conditions. The first check valve 63 connected to the mixer 20 can also prevent the two-phase mixture in the mixer 20 from flowing back into the gas flowmeter 62 and the first regulating valve 61.

[0062] like Figure 1 As shown, preferably, the air branch circuit includes an air compressor 31 , a second check valve, a buffer tank 33 and a pressure reducing valve 34 connected in series in sequence, and the outlet of the pressure reducing valve 34 is connected to n first regulating valves 61 .

[0063] Among them, the n in the n first regulating valves 61 here has the same meaning as the n sub-channel rods 10 mentioned above. Since there are n sub-channel rods 10, each sub-channel rod 10 is provided with a mixer 20, and each mixer 20 is independently connected to the air supply device, the number of first regulating valves 61 connected to the outlet of the pressure reducing valve 34 is also n, that is, the inlet ends of all the first regulating valves 61 are connected in parallel and connected to the outlet end of the pressure reducing valve 34.

[0064] By setting up an air compressor 31, the air is compressed and sent into the buffer tank 33 through the second check valve, which can prevent the pressure fluctuation of the air compressor 31 from directly causing the air pressure fluctuation in the subsequent links. The pressure is reduced by the pressure reducing valve 34 and then output to multiple first regulating valves 61, and the air is supplied to the mixer 20 by the air supply device.

[0065] like Figure 1 As shown, preferably, each liquid supply device includes a second regulating valve 71 and a liquid flow meter 72 arranged in series, and the liquid flow meter 72 is connected to the mixer 20.

[0066] By setting the second regulating valve 71 and the liquid flow meter 72 in series, the second regulating valve 71 can be used to adjust the liquid flow in each liquid supply device, so that multiple liquid supply devices have different liquid flow rates to match the gas flow in the gas supply device to form different two-phase working conditions.

[0067] like Figure 1 As shown, preferably, the water branch includes a water tank 41, a water pump 42 and a water pressure gauge 43 connected in series, and the outlet of the water pressure gauge 43 is connected to n second regulating valves 71; the boric acid injection branch includes a boron-containing water tank 51, an injection pump 52 and a check valve 53 arranged in series in sequence, and the outlet of the check valve 53 is connected to n second regulating valves 71.

[0068] Among them, the n in the n second regulating valves 71 here has the same meaning as the n sub-channel rods 10 mentioned above. Since there are n sub-channel rods 10, each sub-channel rod 10 is provided with a mixer 20, and each mixer 20 is independently connected to the liquid supply device, the number of second regulating valves 71 connected to the outlet end of the water pump 42 and the outlet end of the check valve 53 is also n, that is, the inlet ends of all the second regulating valves 71 are connected in parallel and connected to the outlet end of the water pump 42 and the outlet end of the check valve 53.

[0069] Specifically, the water in the water tank 41 may be deionized water.

[0070] By connecting water tank 41, water pump 42, and water pressure gauge 43 in series, deionized water can be pumped from water tank 41 using water pump 42. The pressure is then measured using water pressure gauge 43. This water is then mixed with the boric acid solution drawn from boron-containing water tank 51 by injection pump 52. The boron concentration in boron-containing water tank 51, the injection frequency of injection pump 52, and the flow rate of the liquid branch are then used to adjust the boric acid concentration for a typical pressurized water reactor core coolant—1300 ppm. The check valve prevents the deionized water and boric acid solution mixture from returning to injection pump 52 and boron-containing water tank 51, diluting the boric acid concentration in boron-containing water tank 51 and causing errors in subsequent testing.

[0071] like Figure 1 As shown, preferably, the outlet of the water pump 42 is also connected to the water tank 41 through a stop valve 44 .

[0072] By setting a stop valve 44 at the outlet of the water pump 42 to connect to the water tank 41, when the second regulating valve 71 limits the flow of the liquid supply device, the water output of the water pump 42 can flow back to the water tank 41 through the stop valve 44, thereby preventing the water pump 42 from being damaged due to excessive pressure.

[0073] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

[0074] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article, or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, article, or device that includes the element.

[0075] In the above embodiments, the descriptions of directions such as “upper” and “lower” are all based on the drawings.

[0076] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0077] Thus, the present invention will not be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A rod bundle channel boron transport measurement system, characterized in that: The invention comprises a sub-channel rod bundle experimental section, a mixer (20), a water branch, an air branch, a high-speed camera, a micro-differential pressure gauge and a boric acid injection branch, wherein the sub-channel rod bundle experimental section comprises n sub-channel rods (10), wherein n is a natural number ≥2, and a communication area (12) is provided between adjacent sub-channel rods (10), the mixer (20) is communicated with the bottom of the sub-channel rods (10), and the water branch, the air branch and the boric acid injection branch are all communicated with the mixer (20); Each of the sub-channel rods (10) is provided with at least two sampling ports (11) of different heights, and each of the sampling ports (11) is connected to an inductively coupled plasma mass spectrometer; The high-speed camera faces the connected area (12), and the connected area (12) is made of a transparent material; The micro-pressure differential gauge is connected to the adjacent sub-channel rods (10) at a position higher than the communication area (12).

2. The rod bundle channel boron transport measurement system according to claim 1, characterized in that: Each of the sub-channel rods (10) is provided with the mixer (20), and each of the mixers (20) is independently connected to an air supply device and a liquid supply device.

3. The rod bundle channel boron transport measurement system according to claim 2, characterized in that: Each of the gas supply devices comprises a first regulating valve (61), a gas flow meter (62) and a first check valve (63) arranged in series, wherein the first check valve (63) is connected to the mixer (20).

4. The rod bundle channel boron transport measurement system according to claim 3, characterized in that: The air branch circuit comprises an air compressor (31), a second check valve (32), a buffer tank (33) and a pressure reducing valve (34) connected in series in sequence, and the outlet of the pressure reducing valve (34) is connected to n first regulating valves (61).

5. The rod bundle channel boron transport measurement system according to claim 2, characterized in that: Each of the liquid supply devices comprises a second regulating valve (71) and a liquid flow meter (72) arranged in series, and the liquid flow meter (72) is connected to the mixer (20).

6. The rod bundle channel boron transport measurement system according to claim 5, characterized in that: The water branch comprises a water tank (41), a water pump (42) and a water pressure gauge (43) connected in series, and the outlet of the water pressure gauge (43) is connected to n second regulating valves (71); the boric acid injection branch comprises a boron-containing water tank (51), an injection pump (52) and a check valve (53) arranged in series in sequence, and the outlet of the check valve (53) is connected to n second regulating valves (71).

7. The rod bundle channel boron transport measurement system according to claim 6, characterized in that: The outlet of the water pump (42) is also connected to the water tank via a stop valve (44).

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