Method for measuring phase transition temperature of molten salt using electrical conductivity

Abstract

The invention provides a phase transition temperature measuring method using electrical conductivity. Specifically, the present invention provides a phase transition temperature measurement method using electrical conductivity, comprising: a step of preparing a molten salt electrical conductivity change chart according to a temperature change; and performing at least one of the following mathematical analysis steps: (i) a step of first-order differentiation of the chart, (ii) a step of second-order differentiation of the chart, and (iii) determining the number of data (n) and resolution (T) on the basis of the chart and deriving Tn according to the following formula (1), performing a linear regression analysis of a linear interval, and detecting an abnormal value using the distance from the linear regression formula as a reference. Tn = Tmax-Tx n... Formula (1) (in formula (1), n is the number of data, and T is the resolution of the measured temperature interval).

Description

Technical Field

[0001] The invention relates to a method for measuring the phase transition temperature of a molten salt using electrical conductivity, and relates to a method for quickly and accurately measuring the solid solution phase transition temperature without using expensive special equipment. Background Art

[0002] Matter changes phase at its own temperature. The temperature at which a liquid solidifies is called the solidification temperature, and the temperature at which a solid melts is called the melting temperature. The temperature at which a liquid solidifies is called the liquidus temperature, and the temperature at which a solid melts is called the solidus temperature.

[0003] If the substance is pure and free of impurities, the temperature when the phase changes does not change, so the four phase transition temperatures are the same. When solid changes to liquid and liquid changes to solid, there is no temperature change and the same temperature is maintained. However, all substances contain impurities, so the four phase transition temperatures may be different. However, even if the temperature changes, the starting point does not change, so the liquidus temperature is also a constant value. Therefore, the international temperature standard uses the liquidus temperature of a specific substance as the ideal standard point.

[0004] Meanwhile, molten salt reactors (MSRs) use liquid fuel in the form of molten salt mixtures and have attracted widespread attention due to their inherent safety characteristics. The molten salt mixture remains liquid within the required temperature range and has a relatively low melting point to enable efficient heat transfer and fluid dynamics within the reactor. Since the selection of a molten salt mixture with an appropriate melting point affects the safety, efficiency, and overall performance of the reactor, it can be said that understanding the phase change behavior of various molten salt mixtures is crucial to the design and development of molten salt reactors.

[0005] In order to evaluate the safety and material corrosion of fuel salt in molten salt reactors like this, it is necessary to derive the phase equilibrium diagram of fuel salt based on the composition. The phase transition temperature value experimentally measured in high-temperature molten salt can be used as a standard data of the phase equilibrium diagram of fuel salt based on computational thermodynamics. In this regard, the DSC (differential scanning calorimetry) measurement method, which is a typical method for experimentally measuring the phase transition temperature, has the problem of requiring the use of expensive special reactor electrodes and the need to install large equipment in a small glove box in order to analyze molten salt that is very sensitive to moisture and oxygen in the atmosphere.

[0006] Meanwhile, Korean Patent No. 10-1412594B1 discloses a method for measuring the electrical conductivity of a solution, and therefore, if the method is suitable for use in actual process sites and can determine the phase transition temperature based on the electrical conductivity, it is expected to be widely used in related fields. Summary of the invention

[0007] Technical issues

[0008] One aspect of the present invention is to provide a method of determining electrical conductivity and based thereon determining phase transition temperature.

[0009] Technical Solution

[0010] According to one aspect of the present invention, there is provided a method for determining phase change using electrical conductivity, comprising: a step of preparing a graph of electrical conductivity change of a molten salt according to temperature change; and performing at least one of the following mathematical analysis steps: (i) a step of performing a first-order differentiation on the graph, (ii) a step of performing a second-order differentiation on the graph, and (iii) a step of determining the number of data (n) and a resolution (ΔT) based on the graph and deriving Tn according to the following formula (1), performing a linear regression analysis on a linear interval, and detecting anomalies based on the distance from the linear regression formula.

[0011] T n =T max -△T x n...Formula (1)

[0012] (In the above formula (1), n ​​is the number of data, and ΔT refers to the resolution of the measured temperature interval)

[0013] Beneficial Effects

[0014] The phase change temperature measurement method based on electrical conductivity of the present invention measures the electrical conductivity in the object, and based on this, a series of mathematical algorithms are used to determine the phase change temperature, so that the accurate phase change temperature value can be simply and quickly calculated. Therefore, according to the present invention, it is expected that the phase change temperature value measured by experiments in high-temperature molten salts, etc. can be used as standard data for phase equilibrium diagrams based on computational thermodynamics. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a flow chart showing a schematic algorithm for determining phase change temperature using electrical conductivity data.

[0016] Figure 2 Shows Figure 1 Definitions of the items recorded in the algorithm flowchart,

[0017] Figure 3The electrical conductivity-temperature curve measured in the (0.56LiCl-0.44KCl)-NdCl3 (30wt%) molten salt and the resulting graphs of (a) the first differential and (b) the second differential for determining the phase transition temperature are shown.

[0018] Figure 4 The electrical conductivity-temperature curve measured in the (0.56LiCl-0.44KCl)-NdCl3 (15wt%) molten salt and the resulting graphs of (a) the first differential and (b) the second differential for determining the phase transition temperature are shown. DETAILED DESCRIPTION

[0019] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0020] The phase change behavior of molten salt mixture is one of the most important basic characteristics that must be understood in determining the operating temperature that affects the safety, efficiency and overall performance of molten salt reactors. According to the present invention, a new method for determining the phase change temperature using electrical conductivity data is provided.

[0021] In the method for measuring phase transition temperature using electrical conductivity of the present invention, there is no particular limitation on the situation of measuring electrical conductivity, as long as the material for measuring electrical conductivity is a solid solution or molten salt having electrical conductivity, for example, the molten salt may include a material selected from 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, Sr The invention can be selected from the group consisting of Br2, BaBr2, AlBr3, UBr3, UBr4, PuBr3, ThBr3, ZrBr4, NdBr3, CeBr3, LaBr3, LiI, KI, NaI, RbI, CsI, CaI2, MgI2, SrI2, BaI2, AlI3, UI3, UI4, PuI3, ThI3, ZrI4, NdI3, CeI3, LaI3, LiI, KI, NaI, LiNO3, KNO3, NaNO3, RbNO3 and CsNO3, and can be preferably 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.

[0022] In more detail, the phase change temperature determination method using electrical conductivity of the present invention includes the following steps: a step of preparing a graph of electrical conductivity variation of the molten salt according to temperature variation; and a step of performing at least one mathematical analysis.

[0023] The mathematical analysis step applicable to the present invention may be at least one of the following: (i) a step of performing a first-order differentiation on the electrical conductivity change graph of the molten salt, (ii) a step of performing a second-order differentiation on the electrical conductivity change graph of the molten salt, and (iii) a step of determining the number of data (n) and the resolution (ΔT) based on the electrical conductivity change graph of the molten salt and deriving Tn according to the following formula (1), performing a linear regression analysis on the linear interval, and detecting abnormal values ​​based on the distance of the linear regression formula.

[0024] T n =T max -△T x n...Formula (1)

[0025] (In the above formula (1), n ​​is the number of data, and ΔT refers to the resolution of the measured temperature interval)

[0026] As a result of executing the above mathematical analysis steps, (i) the highest point of the value during the first-order differential processing in the case, (ii) the inflection point where the value becomes 0 during the second-order differential processing in the case, and (iii) the temperature corresponding to the abnormal value in the case can be determined as the phase transition temperature.

[0027] 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, it may be the liquidus temperature (T L ).

[0028] On the other hand, if the liquidus temperature (T L ) and solidus temperature (solidustemperature, T S ) is less than 25°C, that is, as their intervals become closer, it may be more difficult to distinguish and determine the liquidus temperature and the solidus temperature. In this case, if the step of performing the mathematical analysis of (iii) is included, a relatively accurate liquidus temperature (T L ).

[0029] The present invention first performs the step of preparing a graph of changes in electrical conductivity of the molten salt according to temperature changes. At this time, the device or method for measuring electrical conductivity is not limited, and can be measured by any known device or method.

[0030] Meanwhile, when preparing a graph of the electrical conductivity change of the molten salt according to the temperature change, the temperature change may be an increase or decrease in temperature. For example, when measuring the electrical conductivity while decreasing the temperature, the highest temperature (T m), and can be specified from the highest temperature, at which time the highest temperature is not particularly limited, for example, it can be the highest temperature that a high temperature furnace can withstand, but considering the process economy, the temperature can be cooled from the melting temperature of the molten salt of the analysis object to a temperature 50 to 500°C higher than the melting temperature to room temperature. Alternatively, the electrical conductivity can be measured while the temperature is raised to above the melting temperature starting from the solid phase salt. However, considering the accuracy of the data, when drawing a graph of the change in electrical conductivity of the molten salt according to the temperature change while the temperature is raised, it is preferably done slowly at a temperature increase rate of less than 20°C / h. Similarly, considering the time required for the analysis time and the accuracy, it is preferred to draw a graph while cooling the temperature from the melting temperature of the molten salt to a temperature 50 to 500°C higher than the melting temperature until room temperature.

[0031] In the formula (1) of (iii) above, n is the number of data, and its range is not particularly limited. Considering the reliability of the data, it is preferably an integer of 10 to 100, for example, 50 or less, or 30 or less. Meanwhile, ΔT can be a resolution represented by the interval of the measured temperature, which is also not particularly limited and can be adjusted as needed, but considering the reliability of the data and the required time, it is preferably 2 to 10°C.

[0032] Meanwhile, the step (iii) of detecting an abnormal value from the distance reference of the linear regression equation may be to detect an abnormal value when the absolute value of the distance constant representing the distance from the linear regression equation is greater than the discrimination standard value in Table 1. However, the discrimination standard value may also be adjusted as needed.

[0033] For example, the step of detecting an outlier based on the distance from the linear regression equation may be applied to at least one of the following equations A to E. That is, the distance from the linear regression equation may be detected by selecting at least one of the equations.

[0034] (Formula A)

[0035] (Formula B)

[0036] (Formula C)

[0037] (Formula D)

[0038] (Formula E)

[0039] In more detail, the algorithm is performed based on the discrimination criterion values ​​disclosed in Table 1 below.

[0040]

Table 1

[0041]

[0042] For example, in the case of applying all of Formulas A to E, when the selected formula is applied, if the absolute value of the distance constant is lower than the discrimination criterion value in Table 1, the linear regression analysis is performed again and n is increased to n+1, and the linear regression analysis is re-performed and n is increased by 1 again to perform the algorithm. At this time, it is not necessary to satisfy all of Formulas A to E, and it is independently confirmed whether it is lower than the discrimination criterion value according to each formula. If the absolute value of the distance constant according to Formulas A to E is greater than or equal to the discrimination criterion value, the point is determined as an abnormal value, and the temperature of the point can be determined as the liquidus temperature (liquidustemperature, T L ) steps.

[0043] Meanwhile, the step (iii) of detecting abnormal values ​​based on the distance of the linear regression equation may be performed at the liquidus temperature (T L ) changes to the solidus temperature (T S ) are the same, then the step ends.

[0044] For example, the present invention includes the following steps: preparing a graph of the change in electrical conductivity of the molten salt according to the increase in temperature while increasing the temperature of the solid molten salt; performing first-order or second-order differentiation on the graph of the change in electrical conductivity of the molten salt according to the increase in temperature to determine the solidus temperature (solidus temperature, T S ); a step of melting the molten salt at a temperature rise of 50 to 500° C. higher than the melting temperature of the molten salt; a step of preparing a graph of the electrical conductivity of the molten salt according to the temperature drop while cooling the temperature to room temperature; and a step of determining the number of data (n) and the resolution (ΔT) based on the graph of the electrical conductivity of the molten salt according to the temperature drop, and deriving T from the formula (1) n and performing a linear regression analysis on the linear interval, and taking the distance of the linear regression equation as a reference to detect an abnormal value, the step of detecting the abnormal value may include: when the absolute value of the distance constant determined by at least one equation selected from equations A to E is less than the discrimination standard value, performing the linear regression analysis again and increasing n to n+1, determining the abnormal value when the absolute value of the following distance constant is greater than the discrimination standard value, and determining the temperature of the point as the liquidus temperature (liquidustemperature, T L ),

[0045] The present invention will be described in more detail below through specific examples. The following examples are only examples to help understand the present invention, and the scope of the present invention is not limited thereto.

[0046] Example

[0047] 1. Materials and Equipment

[0048] To measure the electrical conductivity, a custom-made glass capillary electrode (1.5 mm inner diameter, 3 cm capillary length) was used, and a platinum (Pt) wire (1 mm diameter) was used for electrical contact between the capillary electrode and the highly conductive liquid. The electrical conductivity value was obtained by performing a step voltage measurement in microseconds using a potentiometer.

[0049] At the same time, the cell constant is a coefficient used to convert the measured resistance (or the reciprocal of the resistance) into conductivity. A capillary electrode with a cell constant in an appropriate range is selected. Generally, for liquids with high conductivity, a cell constant of 300 cm is recommended. -1 A KCl standard solution of known conductivity is placed in a capillary electrode, the electrode constant is measured in a constant temperature water bath at 291K, and determined using the following equation.

[0050] C=k×R

[0051] Where C is the electrode constant (cm- 1 ), k is the electrical conductivity of the solution (S cm -1 ), and R is the resistance of the solution, and the R value is determined by the slope of the current-voltage curve obtained from the step voltage measurement method in microseconds.

[0052] 2. Method for determining the phase transition temperature of molten salt

[0053] According to the present invention, in a molten salt mixture, the electrical conductivity measuring system as described above is used in the materials and equipment described in 1., the electrical conductivity is measured at certain intervals while the temperature is lowered, and a series of mathematical algorithms are applied to the measured values, so that an objective and accurate phase change temperature can be determined.

[0054] (1) Determination of electrical conductivity

[0055] To measure the electrical conductivity in a molten salt at high temperature, the molten salt mixture is placed in a quartz container and then placed in a high temperature furnace located in a glove box (99.999% argon, water and oxygen <1 ppm). The temperature of the high temperature furnace is controlled and monitored using a thermocouple, which is placed as close as possible to the end of the capillary to determine the exact temperature. To determine the phase change of the molten salt mixture, the molten salt mixture is placed in a quartz container and then placed in a high temperature furnace located in a glove box (99.999% argon, water and oxygen <1 ppm). The temperature of the high temperature furnace is controlled and monitored using a thermocouple, which is placed as close as possible to the end of the capillary to determine the exact temperature. The electrical conductivity is measured at regular intervals while decreasing the temperature within a certain range.

[0056] (2) Determine the phase transition temperature based on mathematical algorithms

[0057] 1) Second-order differential method

[0058] The measured electrical conductivity-temperature curve is subjected to first and / or second order differentiation, and the value at which the maximum value of the first order differentiation result and the inflection point in the second order differentiation result become 0 can be determined as the phase transition temperature. This method can distinguish the transition point that is difficult to determine with the intersection point of the simple linear regression equation, and appropriately adjust the temperature interval belonging to the decomposition energy, so that a more accurate temperature can be determined.

[0059] However, for example, at a solidus temperature (T S ) and liquidus temperature (T L ) in a molten salt system with two phase transition temperatures, when T S and T L When the temperature interval between them is narrow, inaccurate calculation may occur by differentiation depending on the situation. Therefore, the phase transition temperature can be determined by a phase transition temperature determination method based on a mathematical algorithm as shown below or by additionally executing this method.

[0060] 2) Analytical algorithms using linear regression and statistical data analysis

[0061] like Figure 1 As shown in the algorithm flow chart, the phase transition temperature can be determined by a systematic method of determining values ​​according to various statistical evaluation criteria of formulas A, B, C, D, and E.

[0062] At this time, the definitions of each record in the algorithm are as follows.

[0063] T0=T max : The maximum temperature at which the conductivity value is measured

[0064] T n = Minimum temperature in the linear range

[0065] T max = Maximum temperature

[0066] T L =Liquidus temperature

[0067] △T=resolution

[0068] n=minimum number of data

[0069] R 2 = Coefficient of determination

[0070] Z = distance constant

[0071] |Z| = absolute value of the distance constant

[0072] Z det = Criteria for determination

[0073] In addition, Formulas A, B, C, D, and E are exemplary statistical formulas that can evaluate how far a data value is from a linear regression formula, as follows.

[0074] (Formula A)

[0075] (Formula B)

[0076] (Formula C)

[0077] (Formula D)

[0078] (Formula E)

[0079] At this time, the definitions of the items described in each formula are as follows.

[0080] n: the number of data

[0081] k: The number of independent terms in the regression model (for example, in the case of a linear model, since y = ax + b, there are two, a and b)

[0082] y i : the i-th y value

[0083] Predicted ith y value

[0084] x i : the i-th x value

[0085] The average of the x values

[0086]

[0087]

[0088] df = nk-1

[0089]

[0090]

[0091] 3. Experimental example: Determination of phase transition temperature

[0092] LiCl-KCl molten salt is taken as the object of measurement, which is a chloride-based molten salt used for thermochemical reprocessing of spent nuclear fuel. Many researchers have studied various physical properties of the corresponding molten salts, for example, using thermal analysis methods, the melting temperature according to the KCl (or LiCl) composition has been determined in many studies.

[0093] In order to prove the rationality of the phase transition temperature determination method based on electrical conductivity, 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 :liquidus temperature).

[0094] As a result, all temperature values ​​determined were compared with previously reported reliable results.

[0095] Figure 3 The electrical conductivity-temperature curve (a) measured in LiCl-KCl-NdCl3 (30wt%) molten salt and the result chart of the first and second differentials for determining the phase transition temperature (b) are shown. Figure 4 The electrical conductivity-temperature curve (a) measured in LiCl-KCl-NdCl3 (15wt%) molten salt and the result chart (b) of the first and second differentials for determining the phase transition temperature are shown. At this time, wt% is the mass of NdCl3 compared to the total solution weight using the LiCl-KCl eutectic mixture as a solvent.

[0096] Said Figure 3 In Experimental Example 1 (Type I), if T S and T L If the interval between is wide enough, the exact transition temperature can be determined based on the first and / or second differentials of the corresponding curves. S It was confirmed to be 353℃ (first derivative), 352℃ (second derivative), and T L It was confirmed to be 420℃ (first derivative) and 417℃ (second derivative) and was confirmed to be consistent with the (T S : 355℃ and T L : 424℃) are very similar.

[0097] On the other hand, Figure 4 In the case of Experimental Example 2 (Type II), if T S and T L becomes narrower than 25°C, it may be difficult to clearly judge the temperature corresponding to T L Therefore, as shown in Table 1, the additional T that meets the statistical evaluation criteria proposed by the present invention is calculated. L,cal , and are compared in Table 2.

[0098] Table 2 shows the results obtained from statistical equations (A - E) of how much the evaluated data values deviate from the linear regression equation. In Table 2 below, the first column shows n, the second and third columns show T (absolute temperature, the value after adding 273 to the Celsius temperature) and x value (1 / T, the reciprocal of the absolute temperature) respectively, and the fourth column shows the y value (ln k). The fifth column represents the value predicted by the linear regression equation. The values calculated by substituting into the above equations are shown respectively in columns 6 to 10 recorded.

[0099]

Table 2

[0100]

[0101] For the electrical conductivity - temperature curve measured in the (0.56LiCl - 0.44KCl)-NdCl3(15wt%) salt, the T L values obtained from the analysis algorithm using linear regression and statistical data analysis are tabulated in Table 3 below.

[0102]

Table 3

[0103]

[0104] As a result, as can be confirmed from Table 3, in the case of the Figure 4 electrical conductivity - temperature curve, the % difference values calculated from the values reported in the literature show a difference of about 10%, and are confirmed to be in the order of C < E < D < A < B.

[0105] In addition, to confirm the objectivity and rationality of the evaluation methods according to equations A to E, 0.70LiCl - 0.30KCl salt with different compositions is used, and the T L values obtained from the analysis algorithm using linear regression and statistical data analysis for the conductivity - temperature curves with different result values are tabulated in Table 4 below.

[0106]

Table 4

[0107]

[0108] As a result, as can be confirmed from the above Table 4, the % difference values compared with the literature values show differences in the order of C, E < D < A < B. Commonly, it can be confirmed that the C and E methods show small differences from the literature values, while the A and B methods show relatively large differences.

[0109] Therefore, it can be expected that the method of integrating values according to various statistical evaluation criteria based on the present invention can provide objectivity, rationality, and sensitivity control levels for achieving the desired level of uncertainty.

[0110] That is, the phase transition temperature measurement system based on measuring electrical conductivity according to the present invention is very likely to become a new method for measuring the phase transition temperature of various multi-component molten salt systems, and the measurement system is simpler and faster than the existing thermal analysis technology. At the same time, such an analysis algorithm can measure the transition temperature with consistency under any conditions and environments.

[0111] Although the embodiments of the present invention have been described in detail above, the scope of rights of the present invention is not limited thereto, and it will be obvious to those skilled in the art that various modifications and changes can be made without departing from the technical idea of ​​the present invention set forth in the claims.

Claims

1. A method for measuring phase change temperature using electrical conductivity, comprising: The step of preparing a graph of changes in electrical conductivity of the molten salt as a function of temperature; as well as Perform at least one of the following mathematical analysis steps: (i) a step of first-order differentiation of said graph, (ii) a step of performing a second order differentiation of said graph, and (iii) determining the number of data (n) and the resolution (ΔT) based on the graph and deriving Tn according to the following formula (1), performing linear regression analysis on the linear interval, and detecting outliers based on the distance from the linear regression formula, T n =T max -△T x n...Formula (1), (In the above formula (1), n ​​is the number of data and ΔT is the resolution of the measured temperature interval).

2. The method for measuring phase transition temperature using electrical conductivity according to claim 1, wherein: The highest point of the value in the first-order differential processing in case (i), the inflection point where the value becomes 0 in the second-order differential processing in case (ii), and the temperature corresponding to the abnormal value in case (iii) are determined as phase transition temperatures.

3. The method for measuring phase change temperature using electrical conductivity according to claim 1, comprising: If the liquidus temperature (T L ) and solidus temperature (T S ) is less than 25°C, perform the mathematical analysis step (iii).

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

5. The method for measuring phase transition temperature using electrical conductivity according to claim 1, wherein: The molten salt includes at least one component selected from the group consisting of LiCl-KCl, NaCl-KCl, CsCl-KCl, LiCl-NaCl-CaCl2-BaCl2, NaCl-KCl-BaCl2, CaF2, NdCl3, CeCl3 and LaCl3.

6. The method for measuring phase transition temperature using electrical conductivity according to claim 1, wherein: The phase transition temperature is the liquidus temperature (T L ).

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

8. The method for measuring phase transition temperature using electrical conductivity according to claim 1, wherein: The method is that when one or more of the following formulas A to E are applied, if the absolute value of the distance constant is less than the criterion value, the linear regression analysis is performed again and n is increased to n+1. When the absolute value of the following distance constant is greater than the criterion value, it is determined to be an abnormal value, and the temperature of the point is determined as the liquidus temperature (T L ), (Formula A) (Formula B) (Formula C) (Formula D) (Formula E) (At this time, the definitions of the items recorded in each formula are as follows: n: the number of data, k: the number of independent terms in the regression model, y i : the i-th y value, The predicted ith y value, x i : the i-th x value, The mean of the x values, df = nk-1, 9. The method for measuring phase transition temperature using electrical conductivity according to claim 8, wherein: In the step (iii) of detecting an abnormal value based on the distance from the linear regression equation, an abnormal value is detected when the absolute value of the distance constant representing the distance from the linear regression equation is greater than the following discrimination standard values ​​of the distance constant derivation equations A to E. In this case, the discrimination standard values ​​are: Formula A: 2, Formula B: The smaller value between 6 / n and 0.99, Formula C: 2, Formula D: 1, Formula E: 1 when n is less than 30, 2 / n when n is greater than or equal to 30 0.5 .

10. The method for measuring phase transition temperature using electrical conductivity according to claim 8, wherein: In the step (iii) of detecting an abnormal value based on the distance of the linear regression equation, the liquidus temperature (T L ) and solidus temperature (T S ) are the same, end the step.

11. The method for measuring phase change temperature using electrical conductivity according to claim 1, comprising: The step of increasing the temperature of the solid molten salt and preparing a graph of changes in the electrical conductivity of the molten salt according to the increase in temperature; The solidus temperature (T S ) steps; The step of melting the molten salt by increasing the temperature to a temperature 50 to 500° C. higher than the melting temperature of the molten salt; A step of preparing a graph of changes in electrical conductivity of the molten salt according to a decrease in temperature while cooling the temperature to room temperature; The number of data (n) and the resolution (ΔT) are determined based on the graph of the change in electrical conductivity of the molten salt according to the temperature drop, and T is derived from the formula (1): n And perform linear regression analysis on the linear interval, and use the distance of the linear regression equation as the basis for detecting outliers. The step of detecting the abnormal value includes: when one or more of the following formulas A to E are applied, if the absolute value of the distance constant is less than the criterion value, then the linear regression analysis is performed again and n is increased to n+1, and when the absolute value of the following distance constant is greater than the criterion value, it is determined to be an abnormal value, and the temperature of the point is determined as the liquidus temperature (T L ), (Formula A) (Formula B) (Formula C) (Formula D) (Formula E) (At this time, the definitions of the items recorded in each formula are as follows: n: the number of data, k: the number of independent terms in the regression model, y i : the i-th y value, The predicted ith y value, x i : the i-th x value, The mean of the x values, df = nk-1, (At this time, in each distance constant derivation formula A to E, each discrimination standard value is as follows: Formula A: 2, Formula B: The smaller value of 6 / n and 0.99, Formula C: 2, Formula D: 1, Formula E: 1 when n is less than 30, 2 / n when n is greater than or equal to 30 0.5 ).

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