WO2018009433A1

WO2018009433A1 - Flow rate detector

Info

Publication number: WO2018009433A1
Application number: PCT/US2017/040230
Authority: WO
Inventors: John L. HARLOW; Josef R. PARRINGTON
Original assignee: Elysium Industries Ltd.
Priority date: 2016-07-05
Filing date: 2017-06-30
Publication date: 2018-01-11

Abstract

Devices and methods for determining flow rate in a sealed vessel. In one aspect, the devices and methods can combine the use of a tapered tube, a radiation emitting float, and a collimating radiation detector to determine the flow rate of a fluid. In another aspect, the devices and methods can combine the use of a tapered tube and an electromagnetic transducer, such as a linear variable transducer, to determine the flow rate of a fluid. In either case, measurements of fluid flow rate can be made without needing to penetrate the vessel. The devices and methods can be used with any fluid in any system, including molten salts in the secondary coolant of a nuclear reactor system.

Description

FLOW RATE DETECTOR

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/353,363, filed July 5, 2016, entitled "Determining Flow Rate In Non-Nuclear and Nuclear Reactor Molten Salt Test Environments," and U.S. Provisional Patent No. 62/353,344, filed July 5, 2016, entitled "Radiation Emitting Flow Rate Detector." The entirety of each of the above- identified applications is incorporated by reference.

BACKGROUND

[0002] The global demand for energy has largely been fed by fossil fuels. This typically involves taking reduced carbon out of the Earth and burning it. However, those hydrocarbons are in limited supply and burning the hydrocarbons produces carbon dioxide. According to the U.S. Environmental Protection Agency, more than 9 trillion metric tons of carbon is released into the atmosphere each year. Nuclear power is appealing due to possibilities of abundant fuel and carbon-neutral energy production.

[0003] The predominant commercial nuclear reactor for electricity production is the light water reactor (LWR). LWR's have significant drawbacks however. They use solid fuel with long radioactive half-lives and have relatively inefficient fuel utilization. That means that LWR's produce dangerous and long-lived waste products. The fuel is also vulnerable to extreme accidents or conversion to nuclear weapons.

[0004] To improve on known light water reactor (LWR) technologies, molten salt reactors (MSRs) have been researched since the 1950s. MSRs are a class of nuclear fission reactors in which the primary coolant, or even the fuel itself, is a molten salt mixture such as fluoride or chloride salt. Compared to LWRs, MSRs offer projected lower per-kilowatt hour (kWh) levelized cost, comparatively benign fuel and waste inventory composition, highly efficient fuel utilization, and a combination of much higher accident resistance with a much lower worst-case accident severity.

[0005] Early development of MSRs primarily occurred in the 1950s and 1960s. Development of MSRs since the 1970s has taken a back seat, while the U.S. and other nations focused on the development of LWRs up until recent years. As LWR maintenance and upgrade costs continue to rise, older LWRs continue to shut down. And, as the world seeks more environmentally friendly, carbon-free energy, there is a significantly renewed interest in MSRs given the advantages over LWRs.

SUMMARY

[0006] One of the challenges that arise in operation of MSRs is the difficulty in conducting testing. This challenge arises from the juxtaposition of the need to obtain testing data with the need to prevent penetration of vessels holding and transporting the corrosive, high- temperature molten salt. Accordingly, there exists an ongoing need for the development of systems and methods for testing the flow rate of fluids which do not require vessel penetration and which can be applied in a molten salt nuclear reactor environment.

[0007] Embodiments of devices and methods for determining the flow rate of fluids are provided.

[0008] In one embodiment, the disclosed devices and methods can employ a Geiger Muller type collimating detector and a gamma emitting float. The devices and methods can combine the use of a tapered tube with a gamma emitting float disposed therein to determine the flow rate of a fluid without needing to penetrate a vessel containing and transporting the fluid. A Geiger Muller type detector can be used to detect the position of the float within the tapered tube. Displacement of the float can be used to determine the flow rate of the fluid flowing through the tapered tube. By relying on gamma emissions which pass through the molten salt (or other fluid), as well as the walls of the tapered tube or other container, flow information can be determined without the need to penetrate the container or vessel. The disclosed devices and methods can be used with any fluid in any system, including molten salt in the secondary coolant of a nuclear reactor system.

[0009] In one embodiment, a fluid flow detection device can include a tube configured to receive a flow of fluid therethrough. The tube can be tapered such that the fluid flows from an area of smaller circumference to an area of larger circumference. The device can also include a float within the tube. At least a portion of the float can be composed of a gamma ray emitting material. The float can have a shape that is curved to form at least one rounded circumference. [0010] The device can also include a linear detector positioned alongside the tapered tube. The linear detector can be configured to receive gamma ray emissions from the float. The linear detector can also be configured such that the position of the float can be determined based on electrical current from the detector.

[0011] In one embodiment, the linear detector can include a quartz tube filled with an inert gas such as neon as well as a quench gas. The tube can contains a high resistance wire running through the middle of the tube and the wire can be connected to a positive voltage source on one end and a ground or negative voltage source on the other such that there is a potential from one end of the high resistance wire to the other. A metal can be embedded in the quartz along the entire length of the tube having a negligible resistance and the metal is connected to the same ground or negative voltage source as the high resistance wire. An ammeter can be set up to measure the current in the system. As the gamma ray emitting float travels along the length of the glass tube of the linear detector, the detector can act as a Geiger Muller tube and it can cause an arc from the high resistance wire to the metal imbedded in the quartz tube at that location, thereby altering the total resistance of the electrical circuit. Based on the measured current and the known resistance of the high resistance wire and the low resistance imbedded metal, the position at which the arc occurred and the position of the float can be determined. Because the gamma radiation emitted from the float is able to pass through the fluid and the walls of the fluid container, the float position can be determined without physically penetrating the walls of the container, thereby maintaining vessel integrity and increasing safety.

[0012] In other embodiments, the device can be provided in another configuration that can include a series of stacked glass cups having a high voltage wire running through their center. The stacked cups can be sealed in a gas filled tube or envelope having a series of evaporated metal strips on one side corresponding to each of the stacked cups. Each set of cups can define an inert and quench gas filled space with a window on one side facing the flow tube and gamma emitter and a window facing the evaporated metal strip on the other side. The cups can be stacked in a linear fashion following the length of travel of the float in operation such that each space defined by the stacked cups can fire an electric pulse individually and correspond to a certain height or position of the float within the flow tube. Each evaporated metal strip can lead to a ground or negative voltage point such that a potential is established between the high voltage center wire and the metal strip. An ammeter can be further provided to measure current for each metal strip and it can be used to determine an arc occurrence in a particular cup-defined space and, therefore, the associated position of the float within the tube.

[0013] Methods for determining a flow rate of a fluid are also provided and can include flowing a fluid through a tube such that the fluid moves the float in the direction of the fluid flow. The flow tube can be positioned such that the force of gravity is counteracting the direction of flow (e.g., the direction of flow is approximately opposite the direction of the gravitational force). Therefore, the position of the float can be used along with drag characteristics of the float in the fluid and the force of gravity acting on the float to determine the fluid flow rate.

[0014] In another embodiment, a method for determining a flow rate of a fluid is provided. Steps of the method can include providing a device including a tube and a radiation emitting float within the tube, flowing the fluid through the tube such that the fluid moves the float in the direction of the fluid flow, measuring the position of the float as the fluid flows through the tube using a collimating radiation detector, and determining the flow rate of the fluid from the position of the float.

[0015] The tube can be tapered such that the fluid flows from an area of smaller

circumference to an area of larger circumference. The radiation emitting float can be configured to emit gamma radiation. I n certain embodiments, the collimating radiation detector can include a sealed vessel containing an inert gas and a quench gas. The inert gas can be neon.

[0016] In various embodiments, the sealed vessel can include a plurality of stacked cups defining an interior space between them that contains the inert gas and the quench gas; a wire running through the center of the plurality of stacked cups and attached to a voltage source; a conductive strip configured to carry current outside the sealed vessel from the interior space. The stacked cups can further define a window facing the tube and they can be configured to allow radiation from the radiation emitting float to enter the interior space; and a window facing the conductive strip. The sealed vessel can also include a terminal, coupled to the conductive strip and having a voltage less than the voltage source and an ammeter configured to measure a current in the conductive strip. In an embodiment, a corresponding method can include measuring the position of the float by identifying a presence of the current in the conductive strip.

[0017] In certain embodiments, the sealed vessel can include a resistance wire running through the center of the sealed vessel and it can be attached to a first terminal at one end and a second terminal at another end. The first terminal and second terminal can be configured such that a voltage potential exists between them. The sealed vessel can also include a conductive material embedded in a wall of the sealed vessel and connected to the second terminal, where the conductive material includes a resistance that is lower than a resistance of the resistance wire. The sealed vessel can additionally include an ammeter configured to measure a current in a circuit between the first and second terminals. The sealed vessel can be positioned alongside the tube and it can be configured to allow radiation from the radiation emitting float to enter the sealed vessel. Steps of the method may include measuring the position of the float by measuring the current in the circuit and determining a location of an arc within the sealed vessel from the resistance wire to the conductive material.

[0018] The float can have a shape that is curved to form at least one rounded circumference and, in certain embodiments, the float can be spherical. The fluid can be a molten salt. In some embodiments, the tube can be positioned such that direction of fluid flow is opposed by a known force. The known force can be gravity.

[0019] In another embodiment, devices and methods for determining flow rate of fluids in non-nuclear and nuclear reactor molten salt test environments can combine the use of a tapered tube and an electromagnetic transducer to determine the flow rate of a fluid without needing to penetrate a vessel containing and transporting the fluid. The devices and methods of the can be used with any fluid in any system, including molten salt in a nuclear reactor system.

[0020] In one embodiment, the device can include a tube configured to receive a fluid. The tube can be tapered such that a fluid can flow therethrough from an area of smaller circumference to an area of larger circumference. The device can also include a float within the tube. At least a portion of the float can be formed from a magnetic material. The float can have a shape that is curved to form at least one rounded circumference. [0021] Embodiments of the device can also include an electromagnetic transducer positioned around the tube. The float and the electromagnetic transducer can be electromagnetically coupled to each other and they can work in connection to determine the position of the float. The electromagnetic transducer can include an alternating coil system arranged axially around the tube. In one embodiment, the alternating coil system can include a first coil, a second coil and a third coil spaced axially along the tube such that a fluid received by the device can flow past the first coil first, the second coil second, and the third coil last.

[0022] Embodiments of the device can also include insulation for regulating or helping to regulate the temperature of the fluid during operation of the device. The insulation can be provided around the tube and it can be positioned between the tube and the electromagnetic transducer.

[0023] In another embodiment, a method for determining a flow rate of a fluid is provided. The method can include the steps of flowing a fluid through a tube (e.g., a tube of the above- discussed device) such that the fluid moves the float in the direction of the fluid flow and constantly measuring the position of the float as the fluid flows through the tube using an electromagnetic transducer. When the electromagnetic transducer includes the use of an alternating coil system, the method can includes the step of delivering a current to the second coil using an alternating current (AC) source. The alternating coil system can produce an output voltage that is representative of a differential voltage between the first coil and third coil and it can be dependent upon a position of the float within the tube. One of the advantages of the present disclosure lies in the ability of the devices and

[0024] An advantage of the present disclosure lies in the ability of the devices and methods to operate in a hot, corrosive, and optionally radioactive, environment, given that no penetration of the vessel is necessary to measure flow. This ability can allow for manipulation of the materials and operational parameters to fit the needs of the operating environment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] These and other features will be more readily understood from the following detailed description taken in conjunction with the accompanying drawings, in which: [0026] FIG. 1 is a cross sectional view of an exemplary embodiment of a device for measuring fluid flow rate.

[0027] FIG. 2 illustrates a linear collimating radiation detector according to one embodiment.

[0028] FIG. 3 illustrates a stacked cup collimating radiation detector according to one embodiment.

[0029] FIG. 4 shows a stacking cup according to one embodiment.

[0030] FIG. 5 shows a cut away, top view of a stacking cup within a sealed collimating radiation detector according to one embodiment.

[0031] FIG. 6 is a cross sectional front elevational view of another embodiment of a device for measuring fluid flow rate.

[0032] FIG. 7 is a partial cut away view of a device according to one embodiment.

[0033] FIG. 8 is a schematic drawing of the coil connections according to one

embodiment.

[0034] FIG. 9 is a schematic diagram depicting a molten salt reactor system consistent with the present disclosure.

[0035] FIG. 10 is a schematic diagram depicting the chemical processing plant of the molten salt reactor system of FIG. 6 in greater detail.

[0036] It is noted that the drawings are not necessarily to scale. The drawings are intended to depict only typical aspects of the subject matter disclosed herein, and therefore should not be considered as limiting the scope of the disclosure.

DETAILED DESCRIPTION

[0037] For a thorough understanding of the present disclosure, reference should be made to the following detailed description, including the appended claims, in connection with the above-described drawings. Although the present disclosure is described in connection with exemplary embodiments, the disclosure is not intended to be limited to the specific forms set forth herein. It is understood that various omissions and substitutions of equivalents are contemplated as

circumstances may suggest or render expedient.

[0038] Embodiments of the present disclosure present devices and methods for

determining flow rate of a fluid within closed environments. Exemplary embodiments are discussed in detail below with regards to flow of molten salt within a molten salt reactor (e.g., within the secondary coolant). However, a person skilled in the art will appreciate that the disclosed devices and methods can be used with any fluid in any system.

[0039] In one embodiment, the devices and methods can combine the use of a tapered tube and a radiation emitting float located therein to determine the flow rate of a fluid within the tube. In another embodiment, the devices and methods can combine the use of a tapered tube and an electromagnetic transducer to determine the flow rate of a fluid within the tube. The tapered tube can be placed such that a known force, such as gravity, can act on the float in opposition to the direction of fluid flow. Accordingly, based on known or measurable drag characteristics of the float in the fluid and the opposing force acting on the float (e.g., the force of gravity and the mass of the float), the flow rate of the fluid can be determined from the displacement of the float within the tube. By locating the float's position based on emitted radiation capable of passing through both the fluid and the walls of the vessel or using an electromagnetic transducer, the disclosed embodiments can allow for measurement of the float's displacement without physical penetration of the vessel by wires or other features.

Embodiment 1 - Radiation Emitting Float

[0040] FIG. 1 illustrates an exemplary embodiment of a fluid flow measurement device including a divergent-V or tapered tube 1007 through which the fluid to be measured is flowed. A radiation emitting float 1003 can be positioned within the tapered tube 1007 and fluid can flow from the smaller diameter end to the larger diameter end of the tapered tube 1007 as indicated by the arrows 1005. A collimating radiation detector 1001 can be positioned alongside the tapered tube 1007. Examples of the collimating radiation detector 1001 are shown and described in greater detail below in FIGS. 2 and 3. [0041] The float 1003 may be any shape with known drag characteristics in the fluid whose flow is intended to be measured. In an embodiment, the float 1003 can be formed in a shape that is curved and it can include at least one rounded circumference (e.g., a circular circumference) along a cross section taken perpendicular to a longitudinal axis of the tapered tube 1007. Examples of shapes suitable for the float 1003 can include, but are not limited to, spheres, tapered cylinders, tori with a closed middle hole, and cones. The dimensions of the float 1003 can be selected such that it has a diameter that is nearly identical to the diameter of the interior of the tapered tube 1007 at the end having the smallest circumference.

[0042] The float 1003 can be made out of any material or combination of materials that is suitable for prolonged contact with the fluid to be measured (e.g., a molten salt) with at least a portion of the float 1003 including a radiation emitting material. In certain embodiments, the float 1003 can be configured to emit gamma radiation.

[0043] In certain embodiments, the drag characteristics of the float 1003 can be determined experimentally to calibrate the system. The emitting float 1003 can "float" in the salt at a position in a tapered metal cylinder wherein the weight of the float 1003 down is balanced by the flowing salt induced drag up. FIG. 1 shows this condition pictorially. The position of the float 1003 can move up or down in the tapered tube 1007 in direct proportion to the drag/weight characteristics of the flow environment.

[0044] The position of the float 1003 can be determined using a collimating radiation detector 1001. The detector may be spaced axially along-side the tapered flow tube 1007. The localized gamma emission (inherent to the design of the float 1003) can crosses through the fluid (e.g., a molten salt), its containment and a thermal barrier, and enter the detector 1001. The gamma emission can be randomly oriented in three dimensions but the detector 1001 can be configured to attenuate emissions that are not aligned to a limited axial position of the detector. This can be accomplished by dividing the length of the detector into axial regions. FIGS. 2 and 3 illustrate detectors 1001 capable of this delineation.

[0045] The detectors 1001 can operate using the principles of a Geiger Muller tube. See Knoll, 2000, Radiation Detection and Measurement, Third Edition, hereby incorporated by reference in its entirety. In practice, the detectors 1001 can include a chamber filled with an inert gas at a low-pressure and two electrodes. A potential difference can be established between the electrodes (e.g., several hundred volts). The walls of the tube can be either metal or have their inside surface coated with an electrically conductive material to form the cathode, while the anode can be formed from a wire in the center of the chamber.

[0046] When ionizing radiation strikes the tube, some molecules of the gas can be ionized, either directly by the incident radiation or indirectly by secondary electrons produced in the walls of the tube. As a result, positively charged ions and electrons, known as ion pairs, can be created in the fill gas. The strong electric field created by the tube's electrodes can accelerate the positive ions towards the cathode and the electrons towards the anode. Close to the anode in the "avalanche region" the electrons can gain sufficient energy to ionize additional gas molecules and create a large number of electron avalanches, which can in turn spread along the anode and effectively throughout the avalanche region. This is the "gas multiplication" effect which gives the tube its characteristic of being able to produce a significant output pulse from a single ionizing event.

[0047] The production of multiple avalanches can result in an increased multiplication factor and it can produce a measurable amount of ion pairs. The avalanches, for common sizes of tubes, can completely ionize the gas around the anode in just a few microseconds, creating a short, intense pulse of current can be measured. Embodiments of the devices and methods disclosed herein can use this principle to identify radiation emitted from the float 1003. Accordingly, as discussed in greater detail below, collimating the radiation detected to determine an axial location of the radiation source (e.g., the float 1003 along the detector 1001 can facilitate determination of the flow velocity.

[0048] FIG. 2 illustrates one embodiment of the collimating radiation detector 1001. The detector 1001 can include a sealed vessel 2015 that contains a mixture of inert and quenching gases 2011. The sealed vessel may be formed from glass (e.g., quartz) or any other material configured to allow radiation from the float 1003 to pass through it while containing the gas mixture 2011.

[0049] Within the sealed vessel 2015, a high resistance wire 2009 is run lengthwise, with its ends connected to terminals 2003, 2007 with a voltage potential across them (V+/V-). A conductive strip 2001 (e.g., an evaporated metal film) can be embedded in the wall of the sealed vessel and it can have a resistance substantially lower than the high resistance wire 2009. An ammeter 2005 or current detector/sensor can be placed in the circuit such that a current may be measured. Based on the known potential difference across the two terminals 2003, 2007 and the known resistance of a given length of both the embedded conductive material 2001 and the high resistance wire 2009, the measured current can be used to determine the position at which the radiation entered along a length 2013 of the detector 1001. This position can correspond to the position of the radiation emitting float 1003 within the tapered tube 1007 of FIG. 1. These calculations may be performed as discussed in greater detail below.

[0050] The voltage potential or imposed voltage (Εχ) is the difference in voltage between the two terminals 2003, 2007. RT is the total resistance of the path traveled in the electric circuit, or some combination of the resistance of the high resistance wire 2009 and the embedded conductive material 2001, depending on where emitted radiation allowed the current to jump from the high resistance wire 2009 to the embedded conductive material 2001. The measured current is equal to Εχ divided by RT- Where the resistance of the embedded conductive material 2001 is essentially negligible compared to the high resistance wire 2009, the position of a radiation sensing electrical arc from the high resistance wire 2009 to the embedded conductive material 2001 can be determined as

RT = (resistance/unit length of the high resistance wire 2009) * length the electrical current traveled on the wire before jumping (LT)

Because the resistance/unit length is known or can be measured, the distance can be determined from the measured current.

[0051] Put another way, an emission that passes through the vessel can initiate a breakdown cascade that shorts the central high resistance wire 2009 to the imbedded conductive material 2001 at a specific axial point. The imbedded conductive material 2001 in the tube wall has a resistance that is negligible. The central wire 2009 is at potential V+ and can be formed of a material with very high resistance Rcw- In the condition where an emission has not passed through the window the current flowing in the wire to V- is I E = V+/Rcw- This is the minimum current flowing to V-. An emission allows current to be diverted to the imbedded wire bypass a portion of the high resistance central wire. The current can increases to I_e.

[0052] By forming a ratio between the minimum current, I E, and the current at the instant of emission cascade, I_e, the axial location of the emission and the emitter can be found. The emission from the emitter can be shielded to maximize lateral emissions. A statistical data gathering routine can be employed to localize the maximum emission point. Timed signal blocking can be used if the detector 1001 goes into full axial breakdown.

[0053] The radiation emission from the float 1003 is random in 3 dimensions but an algorithm can be used to account for the geometric corrections. A resistance can be found for the centerline of the float 1003 (RCL) such that position (LCL) of the float centerline along the length 2013 of the detector 1001 can be determined as:

LCL = Ra7(resistance/unit length of the high resistance wire 2009) or

[0054] The contained inert gas is preferably neon but may also be a gas such as helium, argon, or a Penning mixture. The quench gas may be, for example, 5- 10% of an organic vapor or halogen gas.

[0055] FIGS. 3-5 illustrate another embodiment of a collimating radiation detector 1001.

[0056] The division of the detector 1001 into axial active regions can help to diminish off alignment emissions which are attenuated more than aligned emissions. By controlling the breakdown voltage of the detector 1001 it is anticipated that the off-alignment emissions can avoid cascading and be "undetected." The separation into active regions can also reduce or substantially eliminate the entire central wire from breaking down.

[0057] In the detectors 1001 depicted in FIGS. 3-5, the active regions can be spaces defined between stacked cups 4001. As shown in FIG. 4, a central wire 3005 can pass through an opening 4007 in the center of each stacked cup 4001 with the wire 3005 sealed to the cup 4001 to prevent a radiation triggered cascade from migrating along the length of the detector 1001 , effectively collimating the radiation and allowing for the position of the radiation source to be determined. The detector 1001 can include a sealed vessel 3001 including a material such as quartz glass configured to contain the inert and quench gas mixture 2011 but allow for radiation from the float 1003 to pass through.

[0058] In certain embodiments, the sealed vessel 3001 can be formed from a material that does not permit the passage of emitted radiation. The vessel 3001 can include one or more radiation admitting windows 5003 formed from a material such as mica, as shown in FIG. 5. Such windows 5003 may allow for further delineation of the radiation source. [0059] The space defined by the cup 4001 can be filled with an inert and quench gas mixture 2011 as described elsewhere herein. The central wire 3005 can be coupled to a voltage source 2003. Each cup 4001 can include a window 4005 to permit the entrance of radiation into the space between cups 4001 as well as a window 4003 to permit the passage of electrical current in the case of a localized radiation induced ionization event and associated electrical arc. The wall of the vessel 3001 at a location corresponding to each window 4003 in each cup 4001 can also include a conductive strip 5001 such as an evaporated metal film. The conductive strip 5001 can be coupled to a terminal by an individual lead 3003 such that a potential exists between the voltage source 2003 and that terminal. Accordingly, a radiation induced ionization event in any one of the spaces between the cups 4001 can induce an electrical arc between the central wire 3005 and the conductive strip 5001 corresponding to that particular space. The cups 4001 can be stacked in a vertical manner so that each space corresponds to an axial location along the length of the tapered tube.

Therefore, by independently measuring the current for each strip 5001, the position of the radiation emitting float 1003 can be determined along with the flow of the fluid around the float 1003.

Embodiment 2 - Electromagnetic Transducer

[0060] FIG. 6 illustrates another exemplary embodiment of a fluid flow measurement device 300. The device 300 can include a tube 310 for transporting the fluid. The tube 310 can be tapered such that the fluid flows from an area of smaller circumference to an area of larger circumference, shown in FIG. 6 with the arrows indicating the flow direction. A float 320 can be located within the tube 310 such that it "floats," or is suspended, in the fluid when in operation.

[0061] An electromagnetic transducer can be positioned around the tube 310. In one embodiment, the electromagnetic transducer can include an alternating coil system 330 that is spaced axially up the tube 310. As shown, the alternating coil system 330 can include a first coil 332, as second coil 334, and a third coil 336. FIG. 1 also illustrates

[0062] A layer of insulation 340 can also be positioned around the tube 310. The insulation can be positioned in between an outer surface of the tube 310 and the alternating coil system 330. [0063] The tube 310 can be in the shape of a tapered cylinder having a longitudinal axis illustrated by the dotted line of FIG. 6. The tube 310 can be longitudinally tapered such that a circumference of the tube 310 increases from one end of the tube 310 to the other.

[0064] The tube 310 can be made out of any material that is suitable for containing fluid that flows through it. As an example, if the fluid is a molten salt, the material can be any material that is suitable for prolonged contact with molten salt. One example of a suitable material includes nickel-based alloys.

[0065] The float 320 can be configured to remain free within the tube 310, such that it does not make contact with the interior walls of the tube 310 when the device 300 is in operation. A diameter of the float 320 can be selected such that is nearly identical to a diameter of the interior of the tube 310 at its end having the smallest circumference.

[0066] In an embodiment, the float 320 can be formed in a shape that is curved and it can include at least one rounded circumference (e.g., a circular circumference) along a cross section taken perpendicular to a longitudinal axis of the tapered tube 310. Examples of shapes suitable for the float 320 can include, but are not limited to, spheres, tapered cylinders, tori with a closed middle hole, and cones. The dimensions of the float 320 can be selected such that it has a diameter that is nearly identical to the diameter of the interior of the tapered tube 310 at the end having the smallest circumference.

[0067] The float 320 can be made out of any material or combination of materials that is suitable for prolonged contact with the fluid to be measured (e.g., a molten salt) with at least a portion of the float 320 being formed from a magnetically permeable material. In certain embodiments, the magnetically permeable material can be a ferromagnetic material.

[0068] The insulation 340 can be provided around the outer circumference of the tube 310 and is positioned between the tube 310 and the alternating coil system 330. In certain embodiments, the insulation 340 can span an entire length of the alternating coil system 330 along the longitudinal axis. In other embodiments, the insulation 340 can span substantially an entire length of the tube 310. The insulation 340 can serve to decrease variations in temperature, such that the temperature is held mainly constant while flowing through tube 310 at the alternating coil system 330. The insulation 340 can be any material that can regulate or help regulate the temperature of the fluid during operation of the device 300, with the understanding that the material will be dependent upon the fluid and environment in which the device 300 will be located.

[0069] The alternating coil system 330 can include a support 338 for holding the three coils 332, 334 and 336 in place. The support 338 can be made out of any material that is capable of withstanding the environment in which the device 300 will be located, such as nuclear reactor molten salt test environments. In certain embodiments, a portion of the support 338 can include a magnetically permeable material. The alternating coil system 330, including the support 338, can avoid contact with the fluid during operation when the device 300 is properly maintained and operating properly.

[0070] In operation, the fluid (e.g. molten salt) can enter the tube 310 from the end having the smallest circumference. The fluid can then travel up the longitudinal axis through the tube 310. As the fluid travels up the tube 310, it can push the float 320 up the tube 310 until the float 320 reaches a point along the tube 310 where the flow area is large enough to allow the entire volume of fluid to flow past the float 320. At this position, the weight of the float 320 can be balanced by the upwards drag of the fluid. The flow capacity, or range (i.e., range that the float travels before reaching the balance point), can be adjusted by modifying the density of the float 320. In general, less dense materials can rise higher in the tube 310 and yield lower flow capacities for the same diameter of the tube 310. The flow range can also be adjusted by changing the diameter of the tube 310 and/or the size of the float 320.

[0071] The position of the float can be determined by the alternating coil system 330 that communicates with the float 320 using electromagnetic coupling. As shown in FIG. 6 and FIG. 7, the three coils can be axially arranged about the tube 310, with the second coil 334 acting as the primary (e.g., active) coil and the two outer coils, the first coil 332 and the third coil 336, acting as the secondary coils. Alternating current (AC) can be used to drive the primary coil 334 and it can also cause a voltage to be induced in each of the coils 332, 336. Any AC source capable of providing the proper current can be used in accordance with the present disclosure. As illustrated in FIG. 8, current can be driven through the second coil 334 at A, which can cause an induction current to be generated through the first coil 332 and the third coil 336 at B. The voltage induced in each of the first coil 332 and the third coil 336 can be proportional to the length of the float 320 that is linked to the first coil 332 and the third coil 336. [0072] The position of the float 320 can move up or down the tube 310 in proportion to the drag and weight characteristics of the flow environment. As shown in FIG. 7, the can fluid flow past the first coil 332 first, the second coil 334 second, and the third coil 336 last. As the float 320 moves through the tube 310, the linkage between the primary coil 334 and the first coil 332 and the third coil 336, changes. When the float 320 is situated towards the top of the tube 310, the voltage in the first coil 332 can increase as the voltage in the third coil 336 decreases. Conversely, when the float 320 is situated toward the bottom of the tube 310, the voltage in the third coil 336 can increase as the voltage in the first coil 332 decreases. The output voltage can be the difference between the first coil 332 voltage and the third coil 336 voltage. Accordingly, when the float 320 is located equidistant between the first coil 332 and the third coil 336, equal voltages can be induced, but the two signals can cancel, leaving an output voltage of approximately zero. The position at which the float 320 is balanced during operation of the device 300 can be accurately calibrated to the rate of flow of the given fluid.

[0073] In one aspect, the AC output voltage can be converted by suitable electronic circuitry to high level DC voltage or current, which can be more convenient to use. This output can then be converted to provide the flow rate of the fluid. In one embodiment, the raw data is electronically communicated to a processor that can be configured to calculate the flow rate and can also receive user input.

[0074] In certain embodiments, the devices 300, 1001 can be configured for use within a fast spectrum molten salt reactor (FS-MSR). As an example, the devices 300, 1001 can be positioned within the secondary coolant loop of an FS-MSR to measure flow therein. A FS- MSR, also sometimes referred to as a "fast neutron reactor" or simply a "fast reactor", can generally include a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons, as opposed to slow, or thermal, neutrons used in a thermal reactor. The term "thermal" can refer to a thermal equilibrium with the medium it is interacting with, the reactor's fuel, moderator and structure, which is much lower energy than the fast neutrons initially produced by fission.

[0075] Thermal reactors can rely on a neutron moderator for reducing the speed of neutrons so as to make them capable of sustaining a nuclear chain reaction. The moderator can slow neutrons until they approach the average kinetic energy of the surrounding particles (i.e., reducing the speed of the neutrons to low velocity thermal neutrons), thereby remaining uncharged and allowing them to penetrate deep in the target and close to the nuclei. Fast reactors, however, do not require a neutron moderator, but must rather use fuel that is relatively rich in fissile material when compared to that required for a thermal reactor.

[0076] FIG. 9 depicts a molten salt reactor system 100 configured for the generation of electrical energy from nuclear fission. The molten salt reactor system 100 can include a molten salt reactor 102 containing the molten fuel salt 104, which can include a mixture of chloride and fluoride salts. The molten fuel salt 104 can include fissile materials, fertile materials, and combinations thereof. Examples of fissile materials can include, but are not limited to, thorium (Th), protactinium (Pa), uranium (U), neptunium (Np), plutonium (Pu), americium (Am), curium (Cm). In certain embodiments, the fissile materials can include one or more of the following isotopes, in any combination: Th-225, Th-227, Th-229, Pa-228, Pa- 230, Pa-232, U-231, U-233, U-235, Np-234, Np-236, Np-238, Pu-237, Pu-239, Pu-241, Am- 240, Am-242, Am-244, Cm-243, Cm-245, and Cm-247). Examples of fertile materials can include, but are not limited to, 232 ThCl₄, 238 238

UCI₃ and UCI₄. In an embodiment, the molten fuel salt 104 can include a mixture of fissile materials including ²³³UC1₃, ²³⁵UC1₃, ²³³UC1₄,

and carrier salts including sodium chloride (NaCl), potassium chloride (KC1), and/or calcium chloride (CaC^).

[0077] Upon absorbing neutrons, nuclear fission can be initiated and sustained in the molten fuel salt 104, generating heat that elevates the temperature of the molten fuel salt 104 (e.g., about 650°C or about 1,200°F). The heated the molten fuel salt 104 can be transported from the molten salt reactor 102 to a heat exchange unit 106 via a pipe 107. The heat exchange unit 106 can be configured to transfer the heat generated by the nuclear fission from the molten fuel salt 104.

[0078] The transfer of heat from the molten fuel salt 104 can be realized in various ways. For example, the heat exchange unit 106 can include a pipe 108, through which the heated molten fuel salt 104 travels, and a secondary fluid 110 (e.g., a coolant salt) that surrounds the pipe 108 and absorbs heat from the molten fuel salt 104. Upon heat transfer, the temperature of the molten fuel salt 104 can be reduced in the heat exchange unit 106 and the molten fuel salt 104 can be transported from the heat exchange unit 106 back to the molten salt reactor 102. The system 100 can also include a secondary heat exchange unit 112 configured to transfer heat from the secondary fluid 110 to a tertiary fluid 114 (e.g., water), as the secondary fluid 110 is circulated through secondary heat exchange unit 112 via a pipe 116. The heat received from the molten fuel salt 104 may be used to generate power (e.g., electric power) using any suitable technology. For example, when the tertiary fluid 114 in the secondary heat exchange unit 112 is water, it can be heated to a steam and transported to a turbine 118. The turbine 118 can be turned by the steam and drive an electrical generator 120 to produce electricity. Steam from the turbine 118 can be conditioned by an ancillary gear 122 (e.g., a compressor, a heat sink, a pre-cooler, and a recuperator) and it can be transported back to the secondary heat exchange unit 112.

[0079] Additionally, or alternatively, the heat received from the molten fuel salt 104 can be used in other applications such as nuclear propulsion (e.g., marine propulsion), desalination, domestic or industrial heating, hydrogen production, or a combination thereof.

[0080] During the operation of the molten salt reactor 102, fission products can be generated in the molten fuel salt 104. The fission products can include a range of elements. The fission products can include, but are not limited to, rubidium (Rb), strontium (Sr), cesium (Cs), and barium (Ba), an element selected from lanthanides, palladium (Pd), ruthenium (Ru), silver (Ag), molybdenum (Mo), niobium (Nb), antimony (Sb), technetium (Tc), xenon (Xe), or krypton (Kr).

[0081] The buildup of fission products (e.g., radioactive noble metals and radioactive noble gases) in the molten fuel salt 104 can impede or interfere with the nuclear fission in the molten salt reactor 102 by poisoning the nuclear fission. For example, xenon- 135 and samarium- 149 can have a high neutron absorption capacity, and can lower the reactivity of the molten salt. Fission products can also reduce the useful lifetime of the molten salt reactor 102 by clogging components, such as heat exchangers or piping.

[0082] Therefore, it can be desirable to keep concentrations of fission products in the molten fuel salt 104 below certain thresholds to maintain proper functioning of the molten salt reactor 102. This goal can be accomplished by a chemical processing plant 124 configured to remove at least a portion of fission products generated in the molten fuel salt 104 during nuclear fission. During operation, molten fuel salt 104 can be transported from the molten salt reactor 102 to the chemical processing plant 124 (e.g., via pipe 109), which can process the molten fuel salt 104 so that the molten salt reactor 102 functions without loss of efficiency or degradation of components. [0083] In certain embodiments, the system 100 can also include an actively cooled freeze plug 126. The freeze plug 126 can be in fluid communication with the molten salt reactor 102 and it can be configured to allow the molten fuel salt 104 to flow into a set of emergency dump tanks 128 in case of power failure and/or on active command.

[0084] One or more of the devices 300, 1001 can be incorporated with the molten salt reactor system 100 to determine the rate of flow through the system 100. In one

embodiment, either of the devices 300, 1001 can be positioned in any one of the pipes (e.g., 107, 108, 109). In another embodiment, a bypass or arm (not shown) for

transporting the molten salt from the pipe, through the device 200, and back to the pipe, can be added at a position along any one of the pipes. In an embodiment, the devices 300, 1001 can be located at a position along a pipe that is oriented in the vertical

direction. That is, a pipe that is oriented with the flow of fluid in a direction opposite the direction of gravity.

[0085] FIG. 10 shows additional detail of the chemical processing plant 124. During a typical state of reactor operation, the molten fuel salt 104 can be circulated continuously (or near-continuously) by way of pump 202 from the molten salt reactor 102 through one or more of the functional sub-units of the chemical processing plant 124. As discussed below, examples of the sub-units can include, but are not limited to, a corrosion reduction unit 204, a froth floatation unit 206, and a salt exchange unit 208.

[0086] In an embodiment, the corrosion reduction unit 204 can be configured to limit or reduce the corrosion of the molten salt reactor 102 by the molten fuel salt 104. The molten salt reactor 102 can be constructed of metallic alloy including one or more of the following elements: iron (Fe), nickel (Ni), chromium (Cr), manganese (Mn), carbon (C), silicon (Si), niobium (Nb), titanium (Ti), vanadium (V), phosphorus (P), sulfur (S), molybdenum (Mo), nitrogen (N), any of the cermet alloys, or a variant thereof, stainless steels (austenitic stainless steel), or a variant thereof, zirconium alloy, or a variant thereof, or tungsten alloy, or a variant thereof.

[0087] During reactor operation, the molten fuel salt 104 can be transported from the molten salt reactor 102 to the corrosion reduction unit 204 and from the corrosion reduction unit 204 back to the molten salt reactor 102. The transportation of the molten fuel salt 104 can be driven by pump 202, which can be configured to adjust the rate of transportation. The corrosion reduction unit 204 can be configured to process the molten fuel salt 104 to maintain an oxidation reduction (redox) ratio, E(o)/E(r), in the molten fuel salt 104 in the molten salt reactor 102 (and elsewhere throughout the system 100) at a substantially constant level, where E(o) is an element (E) at a higher oxidation state (o) and E(r) is that element (E) at a lower oxidation state (r).

[0088] In one embodiment, the element (E) can be an actinide (e.g., uranium (U)), E(o) can be U(IV) and E(r) can be U(III). In this embodiment, U(IV) can be in the form of uranium tetrachloride (UC1₄), U(III) can be in the form of uranium trichloride (UCI₃), and the redox ratio can be a ratio E(o)/E(r) of UCI₄/UCI₃. Although UCI₄ can corrode the molten salt reactor 102, the existence of UCI₄ can reduce the melting point of the molten fuel salt 104.

Therefore, the level of the redox ratio, UCI₄/UCI₃, can be selected based on at least one of a desired corrosion reduction and a desired melting point of the molten fuel salt 104. For example, the redox ratio can be at a substantially constant ratio selected between about 1/50 to about 1/2000. More specifically, the redox ratio can be at a substantially constant level of about 1/2000.

[0089] The froth flotation unit 206 can be configured to remove at least part of insoluble fission products and/or dissolved gas fission products from the molten fuel salt 104.

Examples of insoluble fission products can include one or more of the following in any combination: krypton (Kr), xenon (Xe), palladium (Pd), ruthenium (Ru), silver (Ag), molybdenum (Mo), niobium (Nb), antimony (Sb), and technetium (Tc). Examples of gas fission products can include one or more of xenon (Xe) and krypton (Kr). As an example, the froth flotation unit 206 can generate froth from the molten fuel salt 104 that includes the insoluble fission products and/or the dissolved gas fission products. The dissolved gas fission products can be removed from the froth, and at least a portion of the insoluble fission products can be removed by filtration.

[0090] The salt exchange unit 208 can be configured to remove at least a portion of the soluble fission products dissolved in the molten fuel salt 104. Examples of the soluble fission products can include one or more of the following, in any combination: rubidium (Rb), strontium (Sr), cesium (Cs), barium (Ba), and lanthanides. The removal of soluble fission products can be realized through various mechanisms. [0091] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0092] The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described (or portions thereof), and it is recognized that various modifications are possible within the scope of the claims. Accordingly, the claims are intended to cover all such equivalents.

Incorporation by Reference

[0093] References and citations to other documents, such as patents, patent applications, patent publications, journals, books, papers, web contents, have been made throughout this disclosure. All such documents are hereby incorporated herein by reference in their entirety for all purposes.

Equivalents

[0094] Various modifications of the disclosed embodiments and many further embodiments thereof, in addition to those shown and described herein, will become apparent to those skilled in the art from the full contents of this document, including references to the scientific and patent literature cited herein. The subject matter herein contains important information, exemplification and guidance that can be adapted to the practice of the disclosed

embodiments in its various equivalents thereof.

Claims

CLAIMS What is claimed is:

1. A method for determining a flow rate of a fluid comprising:

providing a device comprising a tube and a radiation emitting float within the tube;

flowing a fluid through the tube such that the fluid moves the float in the direction of the fluid flow;

measuring a position of the float as the fluid flows through the tube using a collimating radiation detector; and

determining, from the position of the float, the flow rate of the fluid.

2. The method of claim 1, wherein the tube is tapered such that the fluid flows from an area of smaller circumference to an area of larger circumference.

3. The method of claim 1, wherein the radiation emitting float emits gamma radiation.

4. The method of claim 1, wherein the collimating radiation detector comprises a sealed vessel containing an inert gas and a quench gas.

5. The method of claim 4, wherein the inert gas is neon.

6. The method of claim 4, wherein the sealed vessel further comprises:

a plurality of stacked cups defining an interior space between them containing the inert gas and the quench gas, wherein the stacked cups further define a window facing the tube and configured to allow radiation from the radiation emitting float to enter the interior space;

a wire running through the center of the plurality of stacked cups and attached to a voltage source;

a conductive strip configured to carry current outside the sealed vessel from the interior space;

a window facing the conductive strip; and

a terminal, coupled to the conductive strip and having a voltage less than the voltage source; and an ammeter configured to measure a current in the conductive strip,

wherein measuring the position of the float further comprises identifying a presence of the current in the conductive strip.

7. The method of claim 4, wherein the sealed vessel further comprises

a resistance wire running through the center of the sealed vessel and attached to a first terminal at one end and a second terminal at another end, wherein the first terminal and second terminal are configured such that a voltage potential exists between them; a conductive material embedded in a wall of the sealed vessel and connected to the second terminal, wherein the conductive material comprises a resistance that is lower than a resistance of the resistance wire; and

an ammeter configured to measure a current in a circuit between the first and second terminals,

wherein the sealed vessel is positioned alongside the tube and configured to allow radiation from the radiation emitting float to enter the sealed vessel, and

wherein measuring the position of the float further comprises measuring the current in the circuit and determining a location of an arc within the sealed vessel from the resistance wire to the conductive material.

8. The method of claim 1, wherein the radiation emitting float is spherical.

9. The method of claim 1, wherein the float has a shape that is curved to form at least one rounded circumference.

10. The method of claim 1, wherein the fluid is molten salt.

11. The method of claim 1, wherein the tube is positioned such that direction of fluid flow is opposed by a known force.

12. The method of claim 11, wherein the known force is gravity.

13. A device for determining a flow rate of a fluid comprising:

a tube configured to receive a flow of fluid;

a radiation emitting float positioned within the tube;

a sealed vessel containing an inert gas and a quench gas and positioned aside the tube, the sealed vessel further comprising: a plurality of stacked cups defining an interior space between them containing the inert gas and the quench gas, wherein the stacked cups further define a window facing the tube and configured to allow radiation from the radiation emitting float to enter the interior space;

a conductive strip configured to carry current outside the sealed vessel from the interior space; and

a window facing the conductive strip;

a terminal, coupled to the conductive strip and having a voltage less than the voltage source; and

an ammeter configured to measure a current in the conductive strip.

14. The device of claim 13, wherein the inert gas is neon.

15. The device of claim 13, wherein the float has a shape that is curved to form at least one rounded circumference.

16. The device of claim 13, wherein the radiation emitting float emits gamma radiation.

17. A device for determining a flow rate of a fluid comprising:

a tube through which a fluid flows;

a radiation emitting float within the tube;

a sealed vessel containing an inert gas and a quench gas and positioned aside the tube, the sealed vessel further comprising:

a resistance wire running through the center of the sealed vessel and attached to a first terminal at one end and a second terminal at another end wherein the first terminal and second terminal are configured such that a voltage potential exists between them;

a conductive material embedded in a wall of the sealed vessel and connected to the second terminal, wherein the conductive material comprises a resistance that is lower than a resistance of the resistance wire; and

an ammeter configured to measure a current in a circuit between the first and second terminals, wherein the sealed vessel is positioned alongside the tube and configured to allow radiation from the radiation emitting float to enter the sealed vessel.

18. The device of claim 17, wherein the inert gas is neon.

19. The device of claim 17, wherein the float has a shape that is curved to form at least one rounded circumference.

20. The device of claim 17, wherein the radiation emitting float emits gamma radiation.