CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/371,052, filed August 4, 2016, entitled "Determination Of Dynamic Viscosity In High Temperature Molten Salt Using A 'Pulled' Ball." This application is also related to U.S. Provisional Application No. 62/358,361, filed July 5, 2016, entitled "Determination Of Dynamic Viscosity In High Temperature Molten Salt Using A 'Pulled' Ball." The entirety of each of these applications is incorporated by reference.

Field

[0002] Embodiments of the present disclosure are generally related to determination of dynamic viscosity and density in fluids, such as high temperature molten salts.

BACKGROUND

[0003] The global demand for energy has largely been fed by fossil fuels. This can involve taking reduced carbon out of the Earth and burning it. However, those hydrocarbons are in limited supply and burning the hydrocarbons can produce 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.

[0004] 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. As a result, LWR's can produce dangerous and long-lived waste products. The fuel can also be vulnerable to extreme accidents or conversion to nuclear weapons.

[0005] To improve on 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 can 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.

[0006] 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

[0007] Molten salts can possess thermal physical characteristics that can have significant influences on heat transfer and heat storage. As an example, one characteristic that can have an important effect on heat transfer and reactor fluid mechanics is viscosity. There are several standard methods for measuring viscosity, including capillary flow, vibration, falling, dropped ball, and rotary methods. However, dynamic viscosity measurement at high temperatures can be difficult. In addition, it can be desirable to protect the corrosive molten salt medium from atmospheric contamination. Accordingly, there is a need to develop an apparatus and method for measuring the dynamic viscosity of high temperature molten salt.

[0008] Embodiments of the present disclosure can include apparatus and methods for determining dynamic viscosity in fluids, including high temperature molten salt. The apparatus and methods can use a motor assembly configured to raise or lower a sphere of a desired size and weight up through a fluid in order to determine the dynamic velocity of the fluid. Beneficially, test cylinders of extreme length are not required. Furthermore, the disclosed apparatus and methods can provide rapid data acquisition and can be used with any fluid in any system, including molten salt in a nuclear reactor system.

[0009] In an embodiment, an apparatus for determining dynamic velocity in a fluid is provided and it can include a cylinder for holding the fluid, the cylinder having an interior cavity, a sphere suspended in the cylinder by a wire, and a motor assembly configured to raise the sphere up through the interior cavity of the cylinder via the wire. [0010] In another embodiment, the cylinder has a height that is greater than a diameter of the cylinder. This configuration can ensure that the sphere has ample distance to travel along the motor driven longitudinal axis of the cylinder.

[0011] In another embodiment, the apparatus further includes a sensor for detecting force. The sensor can be located on the wire at a position between the motor assembly and the cylinder.

[0012] In another embodiment, the motor assembly can be a drum motor or motor driven linear slide. The motor assembly can have variable speed.

[0013] In another embodiment, the apparatus can include a heater surrounding the cylinder around an outer circumference of the cylinder. The heater can be configured to regulate and maintain the temperature of a fluid contained within the cylinder. The heater can be a clam shell heater.

[0014] In another embodiment, the fluid can be a molten salt.

[0015] In another embodiment, the apparatus can include sensor for detecting the drag force of the sphere being pulled through the fluid. The sensor can be being located at the end of the wire at a position between the motor assembly and the cylinder or at the attachment point of the wire to the motor assembly (e.g., a linear slide).

[0016] In another embodiment, the apparatus can include a sleeve located at a top surface of the cylinder and it can have a central bore along a longitudinal axis. The sleeve can be formed from a ceramic material. In certain embodiments, the sleeve can be configured to reduce friction as the wire moves through the bore as-well-as restricting the influx of atmospheric contaminant gases.

[0017] In an embodiment, a method for determining dynamic viscosity in fluids using the apparatus is provided. The method can include pulling or lowering the wire and the sphere within the cylinder through the fluid using the motor assembly. Concurrently, measurements of the drag force of the sphere being pulled or lowered through the fluid, as well as the velocity, or rate, at which the sphere is being displaced through the fluid can be made. The drag force can be measured using a force sensor of the appropriate sensitivity that is attached to the wire between the motor assembly and the sphere. Terminal velocity can then be calculated given the weight of the sphere, which can then be used to determine dynamic viscosity. [0018] In addition to eliminating the need for a test cylinder of extreme length and ensuring rapid data acquisition, one of the advantages of the present disclosure lies in the inherent versatility of the design of the apparatus, such that the velocity of the ball displacement and the magnitude of applied force can easily be adjusted. This versatility allows for more accurate viscosity determinations.

[0019] In one embodiment, a method of determining dynamic viscosity in a fluid is provided. The method can include providing an apparatus. The apparatus can include a cylinder having an interior cavity, a sphere suspended in the cylinder by a wire, and a motor assembly attached to the wire. The method can also include filling the cylinder with the fluid. The method can additionally include raising the sphere up through the interior cavity of the cylinder via the wire by using the motor assembly.

[0020] In another embodiment, the method can include heating the cylinder and the fluid to an approximately constant temperature.

[0021] In another embodiment, the cylinder can be heated using a heater that surrounds the cylinder around an outer circumference of the cylinder.

[0022] In another embodiment, the method can include providing a sensor along the wire at a location between the cylinder and the motor assembly.

[0023] In another embodiment, the method can include measuring a pull force using the sensor as the wire, sensor and sphere are wound up the cylinder by the motor assembly.

[0024] In another embodiment, the method can include providing an inert gas to the cylinder.

[0025] In another embodiment, the method can include passing the wire through a sleeve as it is wound up the cylinder.

[0026] In another embodiment, the wire and sphere can be pulled up the cylinder at a constant velocity.

[0027] In another embodiment, the fluid can be a molten salt. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] These and other features will be more readily understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0029] FIG. 1 is a cross sectional front elevational view of one exemplary embodiment of an apparatus according to an embodiment of the disclosure.

[0030] FIG. 2A is a plot illustrating measurements of density of distilled water using the apparatus of FIG. 1.

[0031] FIG. 2B is a plot illustrating measurements of density of sodium nitrate using the apparatus of FIG. 1.

[0032] FIG. 3 is a schematic diagram depicting an exemplary embodiment of a molten salt reactor system suitable for use with the present disclosure.

[0033] FIG. 4 is a schematic diagram depicting a chemical processing plant of the molten salt reactor system of FIG. 3.

[0034] 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

Dynamic Viscosity Measurements

[0035] Embodiments of the present disclosure provide systems and methods for determining dynamic viscosity in fluids, such as molten salts. Dynamic viscosity can have an important effect on heat transfer and heat storage performance but such measurements can be difficult to obtain in such harsh environments. Dynamic (or shear) viscosity μ can be understood as the resistance of a fluid to shearing flows, where adjacent layers of fluid move parallel to each other with different speeds. Furthermore, in liquids, forces between molecules become important. These forces can lead to an additional contribution to the shear stress. Typically, viscosity can be independent of pressure and tends to fall as temperature increases. [0036] Various methods have been developed for measuring dynamic velocity of fluids, including liquids. One of these methods is called the "dropped ball," or "falling ball," method. In this method, a ball having a certain weight and size is dropped in a vessel containing the fluid, often at an angle to allow for variation in the driving force. To ensure accurate measurement of terminal velocity, both the ball and the vessel can be sized to ensure that the ball reaches a constant velocity for a length of time. The method applies Newton's law of motion under force balance on a falling sphere ball when it reaches a terminal velocity. In Newton's law of motion for a falling ball, there exists a buoyancy force, a weight force, and a drag force, and these three forces reach a net force of zero. The sample viscosity can correlates with the time required by the ball to drop a specific distance, and the test results are given as dynamic viscosity. See Yuan et al., "Measurement of Viscosity in a Vertical Falling Ball Viscometer," American Laboratory, Oct 27, 2008, which is hereby incorporated by reference in its entirety. Viscosity can be calculating using Equations 1 and 2, below:

F _G = m - g = p - V - g (1) where FQ is the effective component of gravity, m is mass, g is the acceleration of gravity, and p is density.

V = K - {p _b - p _s ) = t _r (2) where η is dynamic viscosity, K is a proportionality constant, p _b is density of the ball, p _s is density of the sample, and t _r is rolling time of the ball.

[0037] However, this method has deficiencies. In one aspect, it can require a vessel of a certain height in order for the ball to reach constant velocity for a length of time. In another aspect, the length of time to run the test should be long enough for the ball to reach constant velocity.

[0038] Accordingly, embodiments of the disclosure provide systems for the determination of dynamic viscosity of a fluid without the need for a vessel of substantial height and can decrease the time which is needed to obtain the desired reading. Generally, the apparatus can include a sphere that is configured to be pulled upward (e.g., by a motor assembly) through a fluid contained in a cylinder. When the force required to lift the ball is twice the ball weight (corrected for wire weight and drag on the wire, likely negligible), the lift velocity can be the inverse of the dropping terminal velocity. That is, when the pull rate reaches an upwards velocity such that the drag is equal to the weight of the sphere, the sphere is at terminal velocity and the force sensor will read two times the weight of the sphere. Conversely if the sphere is lowered at a rate such that the force sensor reads a near zero weight (a slight positive weight is required to prevent the wire from going slack), then the steady state falling velocity can be the terminal velocity. The terminal velocity determined in this manner can be used to calculate the dynamic viscosity.

[0039] FIG. 1 is a schematic illustration of an exemplary embodiment an apparatus 300 for determining dynamic viscosity according to the present disclosure. As shown, the apparatus 300 can include a cylinder 350 for containing a fluid 380 in an inert cover gas environment 390. A sphere 370 can be suspended within the cylinder 350 by a thin wire 340. The cylinder 350 can have a height that is larger than its diameter and the wire 340 can extend out of the cylinder 350 through a sleeve 330. The wire 340 can also be attached to a motor assembly 310 on the opposite end of the wire 340 from the sphere 370. A sensor 320 can also be attached to the wire 340. In certain embodiments, the sensor 320 can be attached to the wire 340 at a point on the wire 340 between the sphere 370 and the motor assembly 310. A heater 360 can also be provided around the outer circumference of the cylinder 350.

[0040] The cylinder 350 can be made out of any material that is compatible for use with the fluid 380 for which the viscosity is being determined. For example, if molten salt is the fluid 380 being tested, the material can be formed from a material capable of withstanding prolonged contact with the molten salt (e.g., temperatures greater than or equal to about 1200°F). One example of a suitable material can include nickel-based alloys.

[0041] The wire 340 and the sphere 370 can also to be chosen for compatibility with the fluid 380 to be tested, such as a molten salt. The diameter of the sphere 370 can be smaller than a diameter of an inner surface of the cylinder 350. This configuration can allow the sphere 370 to rise freely within the fluid 380 without touching the inner surface of the cylinder 350. The size and weight of the sphere 370 can be varied as necessary to provide additional viscosity measurements.

[0042] The sleeve 330 can fit into an opening along the top of the cylinder 350, with a portion of the sleeve 330 resting on the top of the cylinder 350. The sleeve 330 can include a bore 332 (e.g., a cylindrical bore) that extends along a longitudinal axis of the apparatus 300 from the top surface to the bottom surface of the sleeve 330. The wire 340 can moves in and out of the apparatus 300 through the bore 332 in the sleeve 330. The sleeve 330 can be made out of any material compatible with the fluid 380 to be tested, such as molten salt, and it can be formed out of ceramic material. The sleeve 330 is to be designed to minimize friction on the wire 340 as it is pulled through the sleeve 330.

[0043] The sensor 320 can be any sensor configured to detect force. As an example, the sensor 320 can be a load cell. Load cells are transducers that can convert force into measurable electrical outputs. Different types of load cells can include, but are not limited to, hydraulic, strain-gage, pneumatic, piezoelectric, and capacitive load cells. In an embodiment, the sensor 320 can be a high precision force sensor, such as those force sensors provided by manufacturers such as HBM, Futek, and Baumer.

[0044] The motor assembly 310 can be any motor assembly that is capable of pulling the sphere 370 upward through the fluid 380 in a controlled manner. In an embodiment, the motor assembly 310 can be a motor driven linear rail or a drum motor. A drum motor can include an electrical motor (typically AC) and a gear box, both of which are fixed to a shaft. A drum motor can also include a rotating cover, or shell, that encloses and protects the components. As such, failure of the motor due to exposure to harmful environmental conditions can be reduced. The shell can be formed from any material compatible with the environment in which the fluid 380 will be tested. In operation, the motor and gear shaft can coordinate to rotate the shell. As the shell rotates, it can either wind the wire 340 up around or unwind the wire 340 and let it down, depending on the direction of rotation. A linear rail can operate in a similar manor and it can use a motor driven lead screw to drive a bearing mounted stage along the axis of the wire 340.

[0045] The heater 360 can be any heater that is capable of controlling the temperature of the fluid 380 within the cylinder 350. As noted above, viscosity of a liquid can be dependent on temperature. As the temperature of the liquid falls, its viscosity increases and, conversely, as the temperature of the liquid rises, its viscosity decreases. In an embodiment, the heater 360 can be a clam shell heater or heater that surrounds the cylinder 350 around its outer circumference. As shown in FIG. 1, the heater 360 can include heating elements 362 running throughout the heater 360 in a circumferential direction. The height of the heater 360 can be approximately the same as the height of the cylinder 350 or can be shorter than the height of the cylinder 350, such that the height of the heater 360 is 50%, 60%, 70%, 80%, 90%, or 95% of the height of the cylinder 350.

[0046] In operation, the fluid 380 (e.g. molten salt) can enter the cylinder 350 by a number of entry points. Suitable entry points can include, but are not limited to, the bore 332 of the sleeve 330, the opening within the top of the cylinder 350 in which the sleeve 330 is fitted, and at least one inlet (not shown) in the side or through the bottom of the cylinder 350. Fluid 380 can be added to the cylinder 350 until it fills at least a portion of the cylinder 350. As an example, the fluid 380 can fill the cylinder 350 up to at least 50%, 60%, 70%, 75%, 80%, 90%, or 95% of the interior capacity of the cylinder 350.

[0047] The remaining interior capacity of the cylinder 350 can be filled with an inert gas which can help protect the fluid 380 from atmospheric contamination. Inert gases can be gases which do not undergo chemical reactions under a set of given conditions. These gases can be used to avoid unwanted chemical reactions that can degrade the fluid 380 (e.g., a molten salt). Examples of inert gases can include argon and nitrogen. However, any inert gas that does not react with the molten salt can be used in accordance with embodiments of the disclosure.

[0048] In operation, the sphere 370 can be suspended within the cylinder 350 by the wire 340, as discussed above. The motor assembly 310 can be used to raise the sphere 370 (and the sensor 320) up through the central cavity of the cylinder 350 at a desired constant lift velocity. In order to ensure that there is enough distance on the wire 340 between the motor assembly 310 and the sensor 320, the sensor 320 can be spaced along the wire 340 at a distance that is greater than or equal to the distance that the sphere 370 will need to move through the fluid 380 during determination of viscosity. The sensor 320 can measure the pull force as the sphere 370 is raised up the internal cavity of the cylinder 350 or the force reduction during lowering of the sphere 370. As the wire 340 is led out of the cylinder 350, it can pass through the sleeve 330. As noted above, the sleeve 330 can be designed to minimize friction on the wire 340. Additionally the heater 360 can be used to ensure that the fluid 380 is kept at an approximately constant.

[0049] As described above, the force, or drag, pull rate, and weight of the sphere 370 can be used to calculate the dynamic velocity of the fluid 380. Measurements of force and pull velocity can be electronically communicated to a computing device including a processor (not shown) and the processor can calculate the terminal velocity and dynamic viscosity. The weight and density of the sphere 370 can be independently measured and provided to the computing system in order to calculate the velocity and viscosity.

Density Measurements

[0050] Embodiments of the apparatus 300 can also be employed for measurement of density of fluids, such as high temperature molten salts. Measurement of the density of molten salts can present challenges similar to those involved with measurement of viscosity, namely developing hardware that can survive elevated temperatures while ensuring that the hardware possesses desired accuracy and precision.

[0051] For density, the mass of the sphere 370 can be measured before and after it is inserted into the fluid 380, which can possess an unknown density. The mass difference before and during insertion into the fluid 380 can be the buoyancy force exerted by the liquid on the sphere 370, and this buoyancy can be the product of the density p of the fluid 380 and the volume of the sphere 370, as illustrated in Equation 3: p = AM /V _s (3) where ΔΜ is the weight change of the sphere 370 on insertion in the fluid 380 and V _s is the volume of the sphere 370.

[0052] To evaluate the apparatus 300 for measurement of liquid density, experiments were performed using a steel sphere 370 with distilled water and sodium nitrate. The apparatus 300 was filled with distilled water or sodium nitrate and the heater 360 was employed to vary the temperature. The mass of the sphere 370 when submerged within water or sodium nitrate was measured using the sensor 320. The volume of the sphere 370 was measured outside of the apparatus 300 and corrected to account for thermal expansion with temperature. Density values were calculated according to Equation 3, above.

[0053] FIG. 2A is a plot of density as a function of temperature for distilled water. Mass measurements were acquired for the distilled water between about 20°C and about 95°C at intervals of about 10°C. As shown, the density measurements for water agree with known literature values quite well. [0054] FIG. 2B is a plot of density as a function of temperature for sodium nitrate. Mass measurements were acquired for the sodium nitrate between about 310°C and about 385°C at intervals of about 10°C. Literature values for sodium nitrate (not shown) range between about 1.88 g/cm ³ to about 1.93 g/cm ³ at its melting point, which agree with the measurements illustrated in FIG. 2B. Literature results also show a linear decrease in density with temperature, sloping about -0.000715 g/cm ³ per °C, also in agreement with the observed slope of about -0.0007.

[0055] In one embodiment, the apparatus 300 can be configured for use within a fast- spectrum molten-salt reactor (FS-MSR) system for viscosity and/or density measurements. An FS-MSR, also sometimes referred to as a "fast neutron reactor" or simply a "fast reactor," can include nuclear reactors 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 the neutrons interact with, the reactor's fuel, and moderator and structure, which is at a much lower energy than the fast neutrons initially produced by fission.

[0056] 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 an 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.

[0057] Fast reactors, however, do not require a neutron moderator, and can use fuel that is relatively rich in fissile material when compared to that required for a thermal reactor. FIG. 3 shows 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 core 102 containing the molten fuel salt 104 (e.g., 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, ThCl ₄ , UCI ₃ and UCI ₄ . In an embodiment, the molten fuel salt 104 can include a mixture of fissile materials including ²³³ UC1 ₃ , ²³⁵ UC1 ₃ , ²³³ UC1 ₄ , ²³⁵ UC1 ₄ , and ²³⁹ PuCl ₃ ; and carrier salts including sodium chloride (NaCl), potassium chloride (KC1), and/or calcium chloride (CaC^).

[0058] Upon absorbing neutrons, nuclear fission can be initiated and sustained in the molten fuel salt 104 by chain-reaction in the fuel salt 104 within the core 102, generating heat that elevates the temperature of the molten fuel salt 104 (e.g., to about 650°C or about 1,200°F). The heated the molten fuel salt 104 can be transported from the molten salt reactor core 102 to a heat exchange unit 106. The heat exchange unit 106 can be configured to transfer the heat generated by the nuclear fission from the molten fuel salt 104.

[0059] The heat exchange unit 106 can be provided in a variety of configurations. In various embodiments, the heat exchange unit 106 can be either internal or external to a reactor vessel that contains the core 102. In additional embodiments, the system 100 can be configured such that first-stage heat exchange (e.g., heat exchange from the fuel salt 104 to a different fluid) can occur both internally and externally to the reactor vessel. In other embodiments, the system 100 can be provided such that the functions of nuclear fission and first-stage heat exchange can be integral to the core 102. That is, heat exchange fluids can be passed through the core 102. In the embodiment of the system 100 of FIG. 1, the heat exchange unit 106 is internal to the reactor vessel.

[0060] In general, fluids of three types can be contained in and/or circulated through the reactor vessel, namely fuel, coolant, and moderator (e.g., any substance that slows neutrons). Various fluids can perform one or more of the fuel, coolant, and moderator functions simultaneously. One or more fluids, including more than one fluid of each functional type, can be contained within or circulated through the core 102. Examples of fluids contained within or circulated through the core 102 in various embodiments can include, but are not limited to, liquid metals, molten salts, supercritical H ₂ O, supercritical CO ₂ , and supercritical N ₂ 0.

[0061] 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 core 102.

[0062] 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 shown in FIG. 3, the secondary fluid 110 can be circulated through secondary heat exchange unit 112 via a pipe 116.

[0063] Additionally or alternatively, in another embodiment (not shown), heat exchange can occur within the core 102 prior to heat exchange within the secondary heat exchange unit 112. As an example, heat from the molten fuel salt 104 can pass to a solid moderator, then to a liquid coolant circulating through the core 102. Subsequently, the liquid coolant circulating through the core 102 can be transported to the secondary heat exchange unit 112. As required by basic thermodynamics, after one or more stages of exchange, heat can be finally delivered to an ultimate heat sink, e.g., the overall environment (not shown).

[0064] Heat received from the molten fuel salt 104 can 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.

[0065] 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 combinations thereof.

[0066] During the operation of the molten salt reactor core 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). [0067] 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 core 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 core 102 by clogging components, such as heat exchangers or piping.

[0068] 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 core 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 core 102 to the chemical processing plant 124, which can process the molten fuel salt 104 so that the molten salt reactor core 102 functions without loss of efficiency or degradation of components. As shown in FIG. 3, the chemical processing plant 124 can be contained within the reactor vessel along with the reactor core 102 and the heat exchange unit 106. However, in alternative embodiments, at least one of the heat exchange unit 106 and the fuel-conditioning plant can be external to the reactor vessel.

[0069] 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 core 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.

[0070] FIG. 4 illustrates 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 from the molten salt reactor core 102 through one or more of the functional sub-units of the chemical processing plant 124 (e.g., using a pump 202). 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.

[0071] In an embodiment, the corrosion reduction unit 204 can be configured to prevent or mitigate corrosion of the molten salt reactor core 102 by the molten fuel salt 104. At least a portion of the molten salt reactor core 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.

[0072] During reactor operation, the molten fuel salt 104 can be transported from the molten salt reactor core 102 to the corrosion reduction unit 204 and from the corrosion reduction unit 204 back to the molten salt reactor core 102. The transportation of the molten fuel salt 104 can be driven by the 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), of the molten fuel salt 104 in the molten salt reactor core 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).

[0073] 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 (UC1 ₄ ), U(III) can be in the form of uranium trichloride (UCI ₃ ), and the redox ratio can be a ratio E(o)/E(r) of UCI ₄ /UCI ₃ . Although UCI ₄ can corrode the molten salt reactor core 102, the existence of UCI ₄ can reduce the melting point of the molten fuel salt 104. Therefore, the level of the redox ratio, UCI ₄ /UCI ₃ , 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 substantially constant and 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.

[0074] 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.

[0075] 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.

[0076] When the apparatus 300 used in a molten salt reactor system or plant (e.g., 100), the molten salt can be sampled from various locations within the reactor system. In one embodiment, the apparatus 300 can be in fluid communication with one or more areas of the reactor system through the use of pipes, for example, that transport the molten salt from the a chosen location within the reactor system to an inlet (not shown) in the apparatus 300. Valves can also be used to regulate flow into the apparatus 300 from one or more locations. In certain embodiments, multiple devices can be employed within a molten salt reactor system for testing viscosity at more than one location in the reactor system.

[0077] All references cited throughout this application, for example patent documents including issued or granted patents or equivalents, patent application publications, and non-patent literature documents or other source material, are hereby incorporated by reference herein in their entireties, as though individually incorporated by reference, to the extent each reference is at least partially not inconsistent with the disclosure in this application. For example, a reference that is partially inconsistent is incorporated by reference except for the partially inconsistent portion of the reference.

[0078] One of ordinary skill in the art will appreciate that starting materials, biological materials, reagents, synthetic methods, purification methods, analytical methods, assay methods, and biological methods other than those specifically exemplified can be employed in the practice of embodiments of the disclosure without resort to undue experimentation. All art-known functional equivalents, of any such materials and methods are intended to be included in the disclosed embodiments. [0079] When a group of substituents is disclosed herein, it is understood that all individual members of that group and all subgroups, including any isomers, enantiomers, and diastereomers of the group members, are disclosed separately.

[0080] When a Markush group, or other grouping is used herein, all individual members of the group and all combinations and sub-combinations possible of the group are intended to be individually included in the disclosure.

[0081] When a compound is described herein such that a particular isomer, enantiomer, or diastereomer of the compound is not specified, for example, in a formula or in a chemical name, that description is intended to include each isomers and enantiomer of the compound described individual or in any combination. Additionally, unless otherwise specified, all isotopic variants of compounds disclosed herein are intended to be encompassed by the disclosure. For example, it will be understood that any one or more hydrogens in a molecule disclosed can be replaced with deuterium or tritium. Isotopic variants of a molecule are generally useful as standards in assays for the molecule and in chemical and biological research related to the molecule or its use. Methods for making such isotopic variants are known in the art. Specific names of compounds are intended to be exemplary, as it is known that one of ordinary skill in the art can name the same compounds differently.

[0082] As used herein, and in the appended claims, the singular forms "a," "an," and "the" include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to "a cell" includes a plurality of such cells and equivalents thereof known to those skilled in the art, and so forth. Additionally, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein.

[0083] As used herein, the term "comprising" is synonymous with "including," "having," "containing," and "characterized by" and each can be used interchangeably. Each of these terms is further inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0084] As used herein, the term "consisting of excludes any element, step, or ingredient not specified in the claim element. [0085] As used herein, the term "consisting essentially of does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. In each instance herein any of the terms "comprising", "consisting essentially of," and "consisting of can be replaced with either of the other two terms.

[0086] The embodiments illustratively described herein suitably can be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.

[0087] The expression "of any of claims XX-YY" (where XX and YY refer to claim numbers) is intended to provide a multiple dependent claim in the alternative form and in some embodiments can be interchangeable with the expression "as in any one of claims XX-YY."

[0088] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the disclosed embodiments belong.

[0089] Whenever a range is given in the specification, for example, a temperature range, a time range, a composition range, or a concentration range, all intermediate ranges and subranges, as well, as all individual values included in the ranges given, are intended to be included in the disclosure. As used herein, ranges specifically include the values provided as endpoint values of the range. For example, a range of 1 to 100 specifically includes the end point values of 1 and 100. It will be understood that any subranges or individual values in a range or sub-range that are included in the description herein can be excluded from the claims herein.

[0090] In the descriptions above and in the claims, phrases such as "at least one of or "one or more of can occur followed by a conjunctive list of elements or features. The term "and/or" can also occur in a list of two or more elements or features. Unless otherwise implicitly or explicitly contradicted by the context in which it is used, such a phrase is intended to mean any of the listed elements or features individually or any of the recited elements or features in combination with any of the other recited elements or features. For example, the phrases "at least one of A and Β;" "one or more of A and Β;" and "A and/or B" are each intended to mean "A alone, B alone, or A and B together." A similar interpretation is also intended for lists including three or more items. For example, the phrases "at least one of A, B, and C;" "one or more of A, B, and C;" and "A, B, and/or C" are each intended to mean "A alone, B alone, C alone, A and B together, A and C together, B and C together, or A and B and C together." In addition, use of the term "based on," above and in the claims is intended to mean, "based at least in part on," such that an unrecited feature or element is also permissible.

[0091] 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, but it is recognized that various modifications are possible within the scope of the claimed embodiments. Thus, it should be understood that although the present application can include discussion of preferred embodiments, exemplary embodiments and optional features, modification and variation of the concepts herein disclosed can be resorted to by those skilled in the art. Such modifications and variations are considered to be within the scope of the disclosed embodiments, as defined by the appended claims. The specific embodiments provided herein are examples of useful embodiments of the present disclosure and it will be apparent to one skilled in the art that they can be carried out using a large number of variations of the devices, device components, and methods steps set forth in the present description. As will be obvious to one of skill in the art, methods and devices useful for the present methods can include a large number of optional compositions and processing elements and steps.

Embodiments of the disclosure can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting on the subject matter described herein.