A method for measuring the phase transition temperature of molten salts using electrical conductivity

Abstract

To provide a phase transition temperature measurement method using electric conductivity.SOLUTION: A phase transition temperature measurement method using electric conductivity, includes the stages of: providing an electric conductivity change graph for a molten salt according to a temperature change; and performing at least one mathematical analysis stage of (i) a stage of primarily differentiating the electric conductivity change graph, (ii) a stage of secondary differentiating the electric conductivity change graph, and (iii) a stage of determining the number (n) of data and resolution (▵T) on the basis of the electric conductivity change graph to derive Tn according the following formula (1), and performing linear regression analysis for a linear section to detect an abnormal value by using a distance from a linear regression formula as a reference. Tn=Tmax-▵Txn ... Formula (1) (In the formula (1), n is the number of data, and ▵T is an interval of measurement temperatures, which means resolution).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for measuring phase transition temperatures using electrical conductivity, and to a method for measuring the phase transition temperatures of solid solutions quickly and accurately without using expensive special equipment. [Background technology]

[0002] A substance changes phase at a specific temperature. The temperature at which a liquid substance solidifies is called the freezing temperature, and the temperature at which a solid substance melts is called the melting temperature. The temperature at which a liquid substance begins to solidify is called the liquidus temperature, and the temperature at which a solid substance begins to melt is called the solidus temperature.

[0003] If a substance is pure and free of impurities, the temperature does not change during the phase change, so the four phase change temperatures are the same. The same temperature is maintained without any change during the transition from solid to liquid and from liquid to solid. However, since all substances contain impurities, there is a possibility that the four phase change temperature values ​​may differ. However, even if the temperature changes, the starting point remains constant, so the liquidus temperature is a value that does not change. For this reason, international temperature standards consider the liquidus temperature of a specific substance to be the most ideal reference point.

[0004] Molten salt reactors (MSRs) use liquid fuel in the form of molten salt mixtures and have attracted much attention due to their inherent safety characteristics. The molten salt mixture must be maintained in a liquid state within a desired temperature range and have a relatively low melting point to enable efficient heat transfer and fluid dynamics within the reactor. Because selecting a molten salt mixture with an appropriate melting point affects the safety, efficiency, and overall performance of the reactor, understanding the phase transition behavior of various molten salt mixtures is crucial for the design and development of molten salt reactors.

[0005] To evaluate the safety and material corrosivity of fuel salts in molten salt reactors, it is essential to derive a phase equilibrium diagram for the fuel salt based on its composition. Experimentally measured phase transition temperatures for high-temperature molten salts can be very useful as reference data for computational thermodynamic-based fuel salt phase equilibrium diagrams. However, the DSC (differential scanning calorimetry) method, a representative method for experimentally measuring phase transition temperatures, requires the use of expensive specialized reactor cells. Furthermore, analyzing molten salts, which are highly sensitive to atmospheric moisture and oxygen, requires the installation of large equipment inside a small glove box.

[0006] Meanwhile, Korean Patent No. 10-1412594B1 (Patent Document 1) discloses a method for measuring the electrical conductivity of a solution, and if it is possible to determine the phase transition temperature based on electrical conductivity suitable for use in actual process sites, it is expected to be widely applicable in related fields. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Korean Patent Registration No. 10-1412594 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, one aspect of the present invention is to provide a method for measuring electrical conductivity and determining the phase transition temperature based on the electrical conductivity. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a method for producing a graph of electrical conductivity of a molten salt according to a change in temperature; (i) a step of first differentiating the graph, (ii) a step of second differentiating the graph, and (iii) a step of determining the number of data (n) and resolution (ΔT) based on the graph and calculating T by the following formula (1):n and performing a linear regression analysis on the linear section to detect an outlier based on the distance from the linear regression equation; A method for measuring a phase transition temperature using electrical conductivity is provided, comprising:

[0010] Tn=T max -△Txn...Equation (1) (In the above formula (1), n ​​is the number of data points, and △T is the interval between measured temperatures, which means resolution.) [Effects of the Invention]

[0011] The electrical conductivity-based phase transition temperature measurement method of the present invention can easily and quickly calculate accurate phase transition temperature values ​​by measuring the electrical conductivity of a target and then determining the phase transition temperature based on the measured electrical conductivity using a series of mathematical algorithms. Therefore, it is expected that the phase transition temperature values ​​experimentally measured for high-temperature molten salts according to the present invention can be used as reference data for computational thermodynamics-based phase equilibrium diagrams. [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows a general algorithm flow chart for determining phase transition temperatures using electrical conductivity data. [Figure 2] This shows the definitions of the items described in the algorithm flowchart in Figure 1. [Figure 3] The graphs show the electrical conductivity-temperature curve measured for a (0.56LiCl-0.44KCl)-NdCl3 (30 wt%) molten salt and the results of (a) the first derivative and (b) the second derivative to determine the phase transition temperature. [Figure 4] The graphs show the electrical conductivity-temperature curve measured for a (0.56LiCl-0.44KCl)-NdCl3 (15 wt%) molten salt and the results of (a) the first derivative and (b) the second derivative to determine the phase transition temperature. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below with reference to the accompanying drawings, in which: FIG. 1 is a block diagram of a semiconductor device according to a first embodiment of the present invention; FIG. 2 is a block diagram of a semiconductor device according to a first embodiment of the present invention; FIG. 3 is a block diagram of a semiconductor device according to a first embodiment of the present invention;

[0014] The phase transition behavior of a molten salt mixture is one of the most essential fundamental characteristics that must be understood in determining the operating temperatures that affect the safety, efficiency, and overall performance of a molten salt nuclear reactor. The present invention provides a new method for measuring the phase transition temperature using electrical conductivity data.

[0015] In the method for measuring a phase transition temperature using electrical conductivity of the present invention, when electrical conductivity is measured, there is no particular limitation on the substance as long as the substance can be measured for electrical conductivity, and it may be a solid solution or a molten salt having electrical conductivity, and for example, the molten salt may be LiPF6, LiF, KF, NaF, RbF, CsF, CaF2, MgF2, SrF2, BaF2, AlF3, UF3, UF4, PuF3, ThF3, ZrF4, NdF3, CeF3, LaF3, LiCl, KCl, NaCl, RbCl, CsCl, CaCl2, MgCl2, SrCl2, BaCl2, AlCl3, UCl3, UCl4, PuCl3, ThCl3, ZrCl4, NdCl3, CeCl3, LaCl3, LiBr, KCBr, NaBr, RbBr, CsBr, CaBr2, MgBr2, SrBr2, The compound may contain one or more selected from the group consisting of BaBr2, AlBr3, UBr3, UBr4, PuBr3, ThBr3, ZrBr4, NdBr3, CeBr3, LaBr3, LiI, KI, NaI, RbI, CsI, CaI2, MgI2, SrI2, BaI2, AlI3, U13, U14, PuI3, ThI3, ZrI4, NdI3, CeI3, LaI3, LiI, KI, NaI, LiNO3, KNO3, NaNO3, RbNO3 and CsNO3, and preferably one or more selected from the group consisting of LiCl-KCl, NaCl-KCl, NaCl-MgCl2, LiCl-NaCl-CaCl2-BaCl2, NaCl-KCl-BaCl2, CsI, UCl3, UCl4, NdCl3, CeCl3 and LaCl3.

[0016] More specifically, the method for measuring a phase transition temperature using electrical conductivity of the present invention includes the steps of preparing a graph of the change in electrical conductivity of a molten salt with temperature change and performing at least one mathematical analysis step.

[0017] The mathematical analysis step applicable to the present invention includes (i) a step of first differentiating the graph of change in electrical conductivity of the molten salt, (ii) a step of second differentiating the graph of change in electrical conductivity of the molten salt, and (iii) a step of determining the number of data (n) and resolution (ΔT) based on the graph of change in electrical conductivity of the molten salt, and calculating T by the following equation (1): nderiving the linear regression equation, performing a linear regression analysis on the linear section, and detecting an outlier based on the distance from the linear regression equation.

[0018] Tn=T max -△Txn...Equation (1) (In the above formula (1), n ​​is the number of data points, and △T is the interval between measured temperatures, which means resolution.)

[0019] As a result of the mathematical analysis step, the phase transition temperature can be determined as the point where the value is highest when the first derivative is calculated, the inflection point where the value is zero when the second derivative is calculated, and the temperature corresponding to the abnormal value in the case of (iii).

[0020] The phase transition temperature to be measured in the present invention is not particularly limited as long as it is a temperature at which the phase of a substance changes. For example, the liquidus temperature (T L ) may also be used.

[0021] On the other hand, liquidus temperature (T L ) and solidus temperature (T S If the difference between the liquidus temperature and the solidus temperature is 25°C or less, that is, the closer the interval is, the more difficult it may be to measure the liquidus temperature and the solidus temperature separately. In this case, if the mathematical analysis step (iii) is performed, it is possible to obtain a relatively accurate liquidus temperature (T L ) can be determined.

[0022] The present invention begins with the step of preparing a graph showing the change in electrical conductivity of the molten salt with temperature change. At this time, the device or method for measuring the electrical conductivity is not limited, and the measurement can be performed using any known device or method.

[0023] On the other hand, when a graph of the change in electrical conductivity of the molten salt due to the temperature change is prepared, the temperature change can be either an increase or a decrease in temperature. For example, when measuring electrical conductivity while decreasing the temperature, the maximum temperature (T m ) and start the determination from that maximum temperature. In this case, the maximum temperature is not particularly limited and may be, for example, the maximum temperature that the high-temperature furnace can withstand. However, considering the economic aspects of the process, the temperature may be cooled from the melting temperature of the molten salt to be analyzed or a temperature 50 to 500°C higher than the melting temperature to room temperature. Alternatively, starting with the salt in a solid phase, the electrical conductivity may be measured while increasing the temperature above the melting temperature. However, considering the accuracy of the data, when plotting a graph of the change in electrical conductivity of the molten salt with temperature change while increasing the temperature, it is preferable that the temperature increase rate be slow, at 20°C / h or less. Thus, considering the time required for analysis and accuracy, it is preferable to start from the melting temperature of the molten salt or a temperature 50 to 500°C higher than the melting temperature and plotting the graph while cooling to room temperature.

[0024] In the above-mentioned formula (1) of (iii), n is the number of data, and its range is not particularly limited, but in consideration of the reliability of the data, it is preferably 10 or more, and may be an integer of 100 or less, for example, 50 or less, or 30 or less. Meanwhile, ΔT is the interval between measurement temperatures and can represent resolution, and is also not particularly limited and can be adjusted as necessary, but in consideration of the reliability of the data and the required time, it is preferably 2 to 10°C.

[0025] Meanwhile, in the step (iii) of detecting an abnormal value based on the distance from the linear regression equation, an abnormal value may be detected when the absolute value of the distance constant indicating the distance from the linear regression equation is equal to or greater than the discrimination criterion value in Table 1. However, the discrimination criterion value may also be adjusted as necessary.

[0026] For example, in the step of detecting an abnormal value based on the distance from the linear regression equation, at least one of the following equations A to E may be applied. That is, at least one of the above equations may be selected to detect the distance from the linear regression equation.

[0027]

number

[0028] More specifically, the algorithm proceeds based on the discrimination criteria values ​​disclosed in Table 1 below.

[0029] [Table 1]

[0030] For example, when all of Equations A to E are applied, if the absolute value of the distance constant is less than the discriminant value in Table 1 when the selected equation is applied, the linear regression analysis is performed again, n is incremented as n+1, and the linear regression analysis is performed again, and 1 is incremented again to n. In this case, it is not necessary to satisfy all of Equations A to E, and it is checked independently for each equation whether it is less than the discriminant value. If the absolute value of the distance constant according to Equations A to E is equal to or greater than the discriminant value, the point is determined to be an abnormal value, and the temperature at the point is set to the liquidus temperature (T L ) can be performed.

[0031] Meanwhile, the step (iii) of detecting an abnormal value based on the distance from the linear regression equation is performed based on the liquidus temperature (T L ) is the solidus temperature (T S ) the stage may end when it becomes the same as

[0032] For example, the present invention provides a method for determining a solidus temperature (T) of a molten salt by first or second differentiation of the graph of electrical conductivity change of the molten salt with increasing temperature. S ), a step of increasing the temperature to a temperature 50 to 500°C higher than the melting temperature of the molten salt to melt the molten salt, a step of preparing a graph of the change in electrical conductivity of the molten salt with decreasing temperature while cooling the temperature of the molten salt to room temperature, and a step of determining the number of data (n) and resolution (△T) based on the graph of the change in electrical conductivity of the molten salt with decreasing temperature, and calculating T by the above formula (1). n and performing a linear regression analysis on the linear section to detect an abnormal value based on the distance from the linear regression equation. In the step of detecting an abnormal value, if the absolute value of the distance constant confirmed by at least one equation selected from equations A to E is less than the discrimination reference value, the linear regression analysis is performed again, n is incremented as n+1, and if the absolute value of the distance constant is equal to or greater than the discrimination reference value, the abnormal value is determined, and the temperature at that point is determined as the liquidus temperature (T L and determining:

[0033] The present invention will be described in more detail with reference to the following specific examples. The following examples are merely illustrative examples to aid in understanding the present invention, and are not intended to limit the scope of the present invention. [Example]

[0034] 1. Materials and Equipment A customized glass capillary cell (inner diameter 1.5 mm, capillary length 3 cm) was used to measure the electrical conductivity, with a Pt wire (diameter 1 mm) used for electrical contact between the capillary cell and the highly conductive liquid. The electrical conductivity values ​​were obtained by measuring the voltage stepwise in microseconds using a potentiometer.

[0035] On the other hand, the cell constant is a coefficient used to convert the measured resistance (or the reciprocal of the resistance) into conductivity. A capillary cell having a cell constant in an appropriate range is selected, and generally, for highly conductive liquids, a cell constant of 300 cm is used. -1 A cell with a value equal to or greater than this is recommended. The cell constant was determined by placing a KCl standard solution of known conductivity in a capillary cell and measuring it in a constant temperature water bath at 291 K, using the following equation:

[0036] C=k×R

[0037] where C is the cell constant (cm -1 ), k is the electrical conductivity of the solution (Scm -1 ), and R is the resistance of the solution, which was determined from the slope of the current-voltage curve obtained from the microsecond step voltmeter.

[0038] 2. Method for determining the phase transition temperature of molten salts According to the present invention, the electrical conductivity of a molten salt mixture is measured at regular intervals while the temperature is being lowered using the electrical conductivity measurement system described above in connection with the materials and equipment described in 1. above, and a series of mathematical algorithms are applied to the measured values ​​to objectively and accurately determine the phase transition temperature.

[0039] (1) Measurement of electrical conductivity To measure the electrical conductivity of the high-temperature molten salt, the molten salt mixture was placed in a quartz vessel and then placed in a high-temperature furnace inside a glove box (99.999% argon, moisture and oxygen <1 ppm). The temperature of the high-temperature furnace was controlled and monitored using a thermocouple, which was placed as close as possible to the edge of the capillary cell to measure the temperature accurately. To measure the phase transition of the molten salt mixture, the electrical conductivity was measured at regular intervals while the temperature was decreased in the range of 300–650 °C.

[0040] (2) Determination of phase transition temperatures based on mathematical algorithms 1) Second order differential method The measured electrical conductivity-temperature curve is differentiated first and / or second, and the point where the first derivative is the highest and the value where the second derivative has an inflection point of zero are determined as the phase transition temperatures. This method can identify transition points that are difficult to determine by the intersection of a simple linear regression equation, and more accurate temperatures can be determined by appropriately adjusting the temperature interval corresponding to the resolution.

[0041] However, for example, the solidus temperature (T S ) and liquidus temperature (T L In a molten salt system with a composition having two phase transition temperatures, T S and T L In the case where the temperature interval between is small, the calculation by differentiation may lead to inaccuracies in some cases, so the phase transition temperatures can be determined by a mathematical algorithm-based phase transition temperature determination method as described below, or by further carrying out such a method.

[0042] 2) Analysis algorithms using linear regression and statistical data analysis The phase transition temperatures can be determined in a systematic way, as shown in the algorithmic flow chart of FIG. 1, by determining values ​​according to various statistical criteria in equations A, B, C, D, and E.

[0043] At this time, the definitions of the following statements in the above algorithm are as follows: T0=T max : The maximum temperature at which conductivity measurement begins T n = minimum temperature in the linear section T max = maximum temperature T L =liquidus temperature △T = resolution n = minimum number of data R 2 = Coefficient of determination Z = distance constant |Z| = absolute value of the distance constant Z det =Discrimination criteria

[0044] Furthermore, the above formulas A, B, C, D, and E are exemplary statistical formulas that can evaluate how far the data values ​​are from the linear regression formula, as follows:

[0045]

number

[0046] In this case, the definitions of the items described in each formula are as follows:

[0047] n: number of data k: The number of independent terms in the regression model (for example, in the case of a linear model, y = ax + b, so a and b are two)

number

[0048] 3. Experimental Example: Determining Phase Transition Temperature The LiCl-KCl molten salt is a chloride-based molten salt used in the thermochemical reprocessing of spent nuclear fuel. Various physical properties of the molten salt have been investigated by several researchers. For example, the melting temperature of KCl (or LiCl) depending on the composition has been measured in various studies using thermal analysis methods.

[0049] To verify the validity of the electrical conductivity-based method for determining the phase transition temperature, electrical conductivity-temperature curves were obtained from LiCl-KCl-based molten salt mixtures, and the solidus temperature (T S : solidus temperature) and liquidus temperature (T L The liquidus temperature was determined.

[0050] As a result, all measured temperature values ​​were compared with previously reported reliable results.

[0051] Figure 3 shows the electrical conductivity vs. temperature curve (a) measured for a LiCl-KCl-NdCl3 (30 wt%) molten salt and the graph (b) showing the first and second derivatives used to determine the phase transition temperature. Figure 4 shows the electrical conductivity vs. temperature curve (a) measured for a LiCl-KCl-NdCl3 (15 wt%) molten salt and the graph (b) showing the first and second derivatives used to determine the phase transition temperature. Here, wt% represents the mass of NdCl3 relative to the mass of the total solution, using a LiCl-KCl eutectic mixture as the solvent.

[0052] Experimental Example 1 (Type I) in Figure 3 above is T S and T L If the interval between T and T is sufficiently large, the exact transition temperature can be determined based on the first and / or second derivative of the curve. S are 353℃ (first derivative), 352℃ (second derivative), and T L were confirmed to be 420°C (first derivative) and 417°C (second derivative), which are consistent with the values ​​presented in the literature (T S : 355℃ and T L It was confirmed that the temperature was very similar to that of the original temperature (424°C).

[0053] On the other hand, as in the case of Experimental Example 2 (Type II) in Figure 4 above, T S and T L When the interval between the L Therefore, it may be difficult to clearly determine the inflection point corresponding to the statistical evaluation criteria proposed in this invention. L、cal The values ​​were calculated as in Table 1 and compared in Table 2.

[0054] Table 2 shows the results obtained from statistical equations (A-E) that evaluate how far data values ​​deviate from a linear regression equation. In Table 2 below, column 1 shows n, columns 2 and 3 show T (absolute temperature, the number obtained by adding 273 to the Celsius temperature) and x value (1 / T, the reciprocal of absolute temperature), respectively, and column 4 shows y value (lnk). Column 5 shows the predicted value from the linear regression equation.

number

[0055] [Table 2]

[0056] Regarding the conductivity - temperature curve measured with the (0.56LiCl - 0.44KCl)-NdCl3(15wt%) salt, the T obtained from the analysis algorithm using linear regression and statistical data analysis L values are summarized in Table 3 below.

[0057] [Table 3]

[0058] As a result, as can be confirmed from Table 3 above, in the case of the conductivity - temperature curve in Figure 4, the % difference values calculated from the values reported in the literature showed a difference of around 10%, and were confirmed in the order of C < E < D < A < B.

[0059] Furthermore, in order to confirm the objectivity and suitability of the evaluation methods for formulas A to E, using the 0.70LiCl - 0.30KCl salt with different compositions, for the conductivity - temperature curves with different result values, the T obtained from the analysis algorithm using linear regression and statistical data analysis L values are summarized in Table 4 below.

[0060] [Table 4]

[0061] As a result, as can be confirmed from Table 4 above, the % difference values compared with the literature values showed differences in the order of C, E < D < A < B. Commonly, it can be confirmed that the C and E methods have less difference from the literature values, and the A and B methods show relatively large differences.

[0062] Thus, the method of aggregating values ​​according to various statistical criteria according to the present invention can be expected to provide a controlled level of objectivity, rationality, and sensitivity to achieve a desired level of uncertainty.

[0063] That is, the phase transition temperature measurement system based on electrical conductivity measurement according to the present invention is very promising as a new methodology for measuring the phase transition temperatures of various multi-component molten salt systems, and this technique is much simpler and faster than conventional thermal analysis techniques. Meanwhile, such an analysis algorithm enables consistent measurement of transition temperatures under any conditions and environments.

[0064] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and it will be obvious to those skilled in the art that various modifications and variations are possible within the scope that does not deviate from the technical idea of ​​the present invention described in the claims.

Claims

1. preparing a graph showing the change in electrical conductivity of the molten salt depending on the temperature; (i) first differentiating the graph; (ii) taking the second derivative of the graph; and (iii) Based on the graph, the number of data (n) and the resolution (ΔT) are determined and calculated by the following formula (1): ｎ and performing a linear regression analysis on a linear section to detect an outlier based on the distance from the linear regression equation; A method for measuring a phase transition temperature using electrical conductivity, wherein the phase transition temperature is determined as the point where the value is highest when the first derivative is calculated, as the inflection point where the value is zero when the second derivative is calculated, or as the temperature corresponding to the abnormal value when the second derivative is calculated, or as the temperature corresponding to the abnormal value when the second derivative is calculated. T ｎ =T ｍａｘ -△Txn .. .. .. .. .. Formula (1) (In the above formula (1), n ​​is the number of data, T max is the maximum temperature at which conductivity measurement starts, and ΔT is the interval between measurement temperatures, which means resolution.)

2. liquidus temperature (T Ｌ ) and solidus temperature (T Ｓ 2. The method for measuring a phase transition temperature using electrical conductivity according to claim 1, further comprising the step of performing the mathematical analysis step (iii) when the difference between the measured temperature and the measured temperature is 25°C or less.

3. 2. The method for measuring a phase transition temperature using electrical conductivity according to claim 1, wherein the temperature change is performed by cooling the molten salt to room temperature from the melting temperature of the molten salt to be analyzed or from a temperature 50 to 500°C higher than the melting temperature, or by increasing the temperature of a solid molten salt to a temperature equal to or higher than the melting temperature.

4. The molten salts are LiCl-KCl, NaCl-KCl, CsCl-KCl, LiCl-NaCl-CaCl ２ -BaCl ２ , NaCl-KCl-BaCl ２ , CaF ２ , NdCl ３ , CeCl ３ and LaCl ３ 2. The method for measuring a phase transition temperature using electrical conductivity according to claim 1, wherein the phase transition temperature is determined by measuring the electrical conductivity of the solution containing at least one component selected from the group consisting of:

5. The phase transition temperature is the liquidus temperature (T Ｌ 2. The method for measuring a phase transition temperature using electrical conductivity according to claim 1 .

6. 2. The method for measuring a phase transition temperature using electrical conductivity according to claim 1, wherein in the formula (1) of (iii), n is an integer of 10 to 100, and ΔT is 2 to 10°C.

7. When one or more of the following formulas A to E for deriving a distance constant (Z) are applied, if the absolute value of the distance constant (Z) indicating the distance from the linear regression formula is less than the discrimination reference value, the linear regression analysis is performed again, n is added as n+1, and if the absolute value of the following distance constant is equal to or greater than the discrimination reference value, it is determined to be an abnormal value, and the temperature at that point is determined to be the liquidus temperature (T Ｌ 2. The method for measuring a phase transition temperature using electrical conductivity according to claim 1, further comprising the step of determining whether the temperature is above 100° C. or above 100° C. [Equation 1] (The definitions of the items in each formula are as follows: n: number of data k: number of independent terms in the regression model [Equation 2]

8. In the step (iii) of detecting an abnormal value based on the distance from the linear regression equation, if the absolute value of the distance constant indicating the distance from the linear regression equation is equal to or greater than each of the following discrimination criteria in the derivation formulas A to E of the distance constant, the abnormal value is detected. In this case, the discrimination criteria are: Formula A: 2 Formula B: The smaller of 6 / n and 0.99 Formula C:2 Formula D: 1 Formula E: When n is less than 30, it is 1, and when n is 30 or more, it is 2 / n ０．５ The method for measuring a phase transition temperature using electrical conductivity according to claim 7, wherein

9. The step (iii) of detecting an abnormal value based on the distance from the linear regression equation is performed using a liquidus temperature (T Ｌ ) is the solidus temperature (Solidus Temperature, T Ｓ 8. The method for measuring a phase transition temperature using electrical conductivity according to claim 7, wherein the step ends when the value of the electric conductivity becomes equal to the value of the electric conductivity.

10. a graph showing the change in electrical conductivity of the molten salt with increasing temperature while increasing the temperature of the solid molten salt; The graph of the change in electrical conductivity of the molten salt with increasing temperature is first or second differentiated to obtain the solidus temperature (T Ｓ ) determining Melting the molten salt by increasing the temperature to a temperature 50 to 500° C. higher than the melting temperature of the molten salt; While cooling the temperature to room temperature, a graph of the change in electrical conductivity of the molten salt according to the temperature decrease is obtained; The number of data (n) and resolution (ΔT) are determined based on the graph of the change in electrical conductivity of the molten salt due to the temperature drop, and T is calculated using the formula (1). ｎ and detecting an outlier based on the distance from the linear regression equation by performing a linear regression analysis on the linear section; The step of detecting an abnormal value may include applying one or more of the following equations A to E to derive a distance constant (Z), and if the absolute value of the distance constant (Z) indicating the distance from the linear regression equation is less than a reference value, re-performing the linear regression analysis and incrementing n by n+1. If the absolute value of the distance constant is equal to or greater than the reference value, the abnormal value is determined, and the temperature at that point is calculated as the liquidus temperature (T Ｌ 2. The method for measuring a phase transition temperature using electrical conductivity according to claim 1, comprising the step of determining: [Equation 3] (In this case, the definitions of the items described in each formula are as follows: n: number of data k: number of independent terms in the regression model [Equation 4] In this case, the respective discrimination criteria in the derivation formulas A to E of the respective distance constants are as follows: Formula A: 2 Formula B: The smaller of 6 / n and 0.99 Formula C:2 Formula D: 1 Formula E: When n is less than 30, it is 1, and when n is 30 or more, it is 2 / n ０．５ ).

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