A method for measuring the mass of a high-temperature molten salt

Abstract

The application discloses a kind of high-temperature molten salt mass measurement methods, by continuously cumulatively in molten salt base salt join certain known mass of same molten salt as element tracer, and by ICP-MS to each molten salt base salt element tracer is monitored concentration.By calculating the ratio of the added element tracer mass and the concentration measured, the total mass of the initial molten salt base salt is calculated.The advantages of the present application are: first, the element tracking method is first proposed to measure the total mass of high-temperature molten salt;Second, the measurement method of the present application can measure the mass of high-temperature molten salt in extremely harsh environment, such as measuring the mass of molten salt in high radiation environment;Third, the measurement method can measure the mass of high-temperature molten salt with unknown density in irregular container.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high-temperature molten salt mass measurement, and particularly relates to a method for measuring the mass of high-temperature molten salt with unknown density in an irregular container by means of element tracking dilution. BACKGROUND

[0002] The molten salt reactor is one of the latest reactors in the world at present, in which the molten salt is used as the liquid fuel in the molten salt reactor and is used as both the nuclear fuel and the coolant of the molten salt reactor. Compared with the traditional solid fuel, the molten salt fuel containing actinides needs a higher level of safety protection method. Because the plutonium-239 in the molten salt reactor can be directly used or converted into the raw material of nuclear weapons, it is necessary to detect the mass of the plutonium-239 in the molten salt reactor. Since the molten salt in the molten salt reactor is used as the carrier of the fissile material, the mass measurement of the plutonium-239 in the molten salt reactor can be divided into the measurement of the plutonium concentration and the measurement of the total mass in the molten salt reactor.

[0003] At present, there are many methods for measuring the plutonium concentration in the molten salt reactor, including laser-induced breakdown spectroscopy (LIBS), electrochemical analysis method, and inductively coupled plasma mass spectrometer (ICP-MS) and the like. However, it is difficult to measure the total mass of the molten salt in the molten salt reactor.

[0004] Generally, the mass of the molten salt can be determined by the liquid level measurement and the molten salt density measurement or calculation. However, for the high-temperature molten salt reactor, the liquid level measurement has no effect when the molten salt flows through the tortuous pipeline and the heat exchanger. Meanwhile, it is difficult to assign a single density to the molten salt in the molten salt reactor due to the difference in the temperature around the high-temperature molten salt and the variability caused by the nuclear fuel fission. In summary, the measurement of the mass of the molten salt in the molten salt reactor is less concerned and quite challenging. SUMMARY

[0005] The present application provides a method for measuring the mass of the high-temperature molten salt in the irregular container in view of the difficulty in measuring the mass of the high-temperature molten salt in the existing high-temperature molten salt reactor. The unknown density of the high-temperature molten salt in the irregular container can be effectively measured by using the present application.

[0006] To achieve the above-mentioned purpose, the present application provides a high-temperature molten salt mass measurement method, which comprises the following steps:

[0007] A. Obtaining experimental data

[0008] A specified molten salt is used as an element tracking agent, and a part of the molten salt bottom salt with the mass to be measured is selected as a bottom salt sample, wherein the specified molten salt contains an element that is not contained in the molten salt bottom salt with the mass to be measured;

[0009] The specified molten salt and the base salt sample are weighed and mixed in a certain proportion;

[0010] The above mixture is added to an alumina crucible and heated to a molten state, which is referred to as molten salt system 1;

[0011] A stainless steel full-thread rod is inserted into the above molten salt system 1 in a molten state, and rapid sampling is performed, and the collected molten salt sample is referred to as molten salt sample 1;

[0012] The molten salt system 1 is cooled to room temperature;

[0013] The specified molten salt is weighed again and added to the above molten salt system 1 cooled to room temperature, and mixed and heated to a molten state, which is referred to as molten salt system 2;

[0014] A stainless steel full-thread rod is inserted into the above molten salt system 2 in a molten state, and rapid sampling is performed, and the collected molten salt sample is referred to as molten salt sample 2;

[0015] The molten salt system 2 is cooled to room temperature;

[0016] The specified molten salt is repeatedly added to the cooled molten salt system n, and after heating to a molten state, it is referred to as molten salt system n+1, and then a stainless steel full-thread rod is used for rapid sampling and is marked as molten salt sample n+1, and then the molten salt system is cooled to room temperature, where n is an integer greater than or equal to 2;

[0017] The collected molten salt samples 1 to n+1 are subjected to concentration detection of the trace elements, and the mass of the base salt sample at the beginning of the mixing is calculated according to the detected concentration of the trace elements and the actual mass of the trace elements added, the calculated mass of the base salt sample is compared with the mass of the base salt sample weighed at that time, the mass error is calculated, and when the mass error is a set value, the corresponding concentration of the trace element is obtained, which is marked as the reference value;

[0018] According to the data obtained from the molten salt samples 1 to n+1, the functional relationship between the mass of the added element tracer, the detected concentration, and the mass of the base salt is obtained;

[0019] B. On-site measurement of high-temperature molten salt mass

[0020] A known mass of specified molten salt is added to the molten salt base salt to be measured in several times, and after each addition of specified molten salt, the actual concentration of the trace element in the molten salt base salt is detected by sampling; when the actual concentration is greater than or equal to the reference value, the addition of specified molten salt is stopped, and the total mass of the specified molten salt added so far is recorded; according to the actual concentration of the trace element, the total mass of the specified molten salt, and the functional relationship, the mass of the molten salt base salt to be measured is calculated.

[0021] Preferably, in step A, when the added molten salt element tracer reaches the concentration of the reference value, the steps of repeatedly adding the element tracer, heating, sampling and cooling are stopped.

[0022] Preferably, the specified molten salt comprises one of potassium chloride, cerium chloride, and the molten salt base salt is sodium chloride-calcium chloride.

[0023] Preferably, the purity of the molten salt is: potassium chloride ≥ 99.0%, cerium chloride ≥ 99.9%, sodium chloride ≥ 99.99%, and calcium chloride ≥ 99.99%.

[0024] Preferably, the alumina crucible containing the specified molten salt and the molten salt base salt is a 100-ml alumina crucible of Advalue Technology Company, model AL-2100, and a 250-ml alumina crucible is used to contain the 100-ml alumina crucible to prevent the high-temperature molten salt from flowing out after the 100-ml alumina crucible breaks.

[0025] Preferably, the entire experimental process is carried out in a glove box filled with argon protective gas, and the H2O concentration and O2 concentration in the glove box are less than 1 ppm.

[0026] Preferably, the heating process parameters of the molten salt system are as follows: the temperature is 650°C, and the heating rate is 100°C / h.

[0027] Preferably, after the molten salt system is heated to 650°C, it is kept at the set temperature of 650°C for 3 hours, and a tungsten rod is used to stir the molten state of the molten salt system for 3 minutes to ensure the uniformity of the molten salt system.

[0028] Preferably, the stainless steel full-thread rod is a 316SS rod.

[0029] Preferably, the molten salt sample is collected in an amount of 50 mg each time, and is stored separately in a clean glass bottle and sealed for preservation. When the concentration is detected, it is all dissolved in 2 vol% concentration nitric acid, and then ICP-MS element detection is performed.

[0030] The high-temperature molten salt quality measurement method provided by the present application is to continuously and cumulatively add a certain known mass of the same molten salt as an element tracer into the molten salt base salt, and to monitor the concentration of the element tracer added into the molten salt base salt each time by ICP-MS. The ratio of the added element tracer mass to the measured concentration is calculated to calculate the total mass of the original molten salt base salt. In the process of measuring the mass of the high-temperature molten salt, the present application is not affected by the extreme environment of high-temperature radiation, and can accurately measure the mass of the molten salt and the molten salt mixture with unknown density in an irregular container. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1Part of flow diagram of a high-temperature molten salt quality measurement method according to the present application is shown in the figure;

[0032] Figure 2 ICP-MS detection results of element cerium in the sodium chloride-calcium chloride molten salt in Example 1 are compared with the theoretical calculation results.

[0033] Figure 3 ICP-MS detection results of element potassium in the sodium chloride-calcium chloride molten salt in Example 2 are compared with the theoretical calculation results. DETAILED DESCRIPTION

[0034] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are intended to be illustrative only and are not limiting of the present application.

[0035] Example 1

[0036] Cerium chloride was used as a specified molten salt, element cerium as an element tracer, and sodium chloride-calcium chloride as a molten salt base salt to measure the quality thereof. 84.7 g of the sodium chloride-calcium chloride molten salt base salt was divided into 11 portions, and cerium chloride was added as an element tracer. The sodium chloride-calcium chloride molten salt base salt and the element tracer cerium chloride were mixed uniformly and placed in a 100-ml alumina crucible, and heated in a muffle furnace. Stainless steel full-thread rods were used for batch sampling, and the entire experimental process was carried out in a glove box. A total of 2.14 g of cerium chloride was added, the molten salt system was heated to 650℃, and the heating rate was 100℃ / h.

[0037] Table 1 shows the mass of cerium chloride added each time, the total mass of cerium chloride added, and the percentage of cerium chloride in the molten salt system. According to the calculation, when the concentration of cerium chloride is greater than 1.1wt%, the error rate of using potassium chloride as an element tracer to measure the quality of the sodium chloride-calcium chloride molten salt is 2.39%.

[0038] Table 1

[0039]

[0040]

[0041] Example 2

[0042] Potassium chloride was used as the specified molten salt, and elemental potassium was used as the elemental tracer. The mass of the molten salt was measured using sodium chloride-calcium chloride as the base salt. 38.5 g of the sodium chloride-calcium chloride molten salt base salt was added with 10 portions of potassium chloride as the elemental tracer. The sodium chloride-calcium chloride molten salt base salt and the elemental tracer potassium chloride were mixed and placed in a 100-ml alumina crucible. The crucible was heated in a muffle furnace, and stainless steel full-thread rods were used to take samples in batches. The entire experiment was performed in a glove box. A total of 1.06 g of potassium chloride was added, and the molten salt system was heated to 650°C at a rate of 100°C / h.

[0043] Table 2 shows the mass of the potassium chloride added each time, the total mass of the cerium chloride added, and the percentage of the cerium chloride in the molten salt system. According to the calculation, when the concentration of the potassium chloride is greater than 1.1 wt%, the error rate of the measurement of the sodium chloride-calcium chloride molten salt using potassium chloride as the elemental tracer is 1.82%.

[0044] Table 2

[0045] Sample Name mass of CeCl3 added (g) Cumulative mass of CeCl3 added (g) Concentration of CeCl3 (wt%) NCK-001 +0.1028 0.1028 0.267％ NCK-002 +0.0990 0.2018 0.522％ NCK-003 +0.1088 0.3106 0.801％ NCK-004 +0.1012 0.4118 1.059％ NCK-005 +0.1063 0.5181 1.329％ NCK-006 +0.1077 0.6258 1.601％ NCK-007 +0.0854 0.7112 1.816％ NCK-008 +0.1123 0.8235 2.096％ NCK-009 +0.0930 0.9165 2.328％ NCK-010 +0.1455 1.0620 2.687％

Claims

1. A method for measuring the mass of high-temperature molten salt, characterized in that, Includes the following steps: A. Obtaining experimental data Using a specified molten salt as an element tracer, a portion of the molten salt substrate of the mass to be tested is selected as the substrate sample, wherein the specified molten salt contains elements not present in the molten salt substrate of the mass to be tested; Weigh and mix the specified molten salt and bottom salt samples in a certain proportion; The above mixture was added to an alumina crucible and heated to a molten state, which was called molten salt system 1; A stainless steel threaded rod is inserted into the molten salt system 1 in the molten state described above, and a rapid sample is taken. The collected molten salt sample is called molten salt sample 1. Cool molten salt system 1 to room temperature; Weigh the specified molten salt again and add it to the molten salt system 1 that has been cooled to room temperature. Mix and heat until it melts, and call it molten salt system 2. A stainless steel threaded rod is inserted into the molten salt system 2 in the molten state described above, and a rapid sample is taken. The collected molten salt sample is called molten salt sample 2. Cool the molten salt system 2 to room temperature; The specified molten salt is repeatedly added to the cooled molten salt system n and heated to a molten state. This system is called molten salt system n+1. A sample is then taken quickly using a stainless steel threaded rod and marked as molten salt sample n+1. The molten salt system is then cooled to room temperature. Here, n is an integer greater than or equal to 2. The concentration of the tracking element is detected in the collected molten salt samples 1 to molten salt samples n+1. The mass of the bottom salt sample at the beginning of the mixing is calculated based on the detected concentration of the tracking element and the actual mass of the tracking element added. The calculated mass of the bottom salt sample is compared with the mass of the bottom salt sample weighed at that time to calculate the mass error. The concentration of the tracking element corresponding to the mass error is obtained when the mass error is the set value. This concentration is marked as the baseline value. Based on the data obtained from molten salt samples 1 to n+1, the functional relationship between the mass of the added elemental tracer, the detected concentration, and the mass of the bottom salt was obtained. B. On-site measurement of the mass of high-temperature molten salt Add a known mass of a specified molten salt to the molten salt substrate to be tested in portions. After each addition of the specified molten salt, stir thoroughly and take a sample to detect the actual concentration of the tracking element in the molten salt substrate. When the actual concentration is greater than or equal to the reference value, stop adding the specified molten salt and record the total mass of the specified molten salt added up to this point. Calculate the mass of the molten salt substrate to be tested based on the actual concentration of the tracking element, the total mass of the specified molten salt, and the functional relationship.

2. The method according to claim 1, characterized in that, In step A, when the added molten salt element tracer reaches the concentration of the baseline value, the steps of repeatedly adding the element tracer, heating, sampling, and cooling are stopped.

3. The method according to claim 1, characterized in that, The specified molten salt includes one of potassium chloride and cerium chloride, and the bottom salt of the molten salt is sodium chloride-calcium chloride.

4. The method according to claim 3, characterized in that, The purity of the molten salt is as follows: potassium chloride ≥ 99.0%, cerium chloride ≥ 99.9%, sodium chloride ≥ 99.99%, and calcium chloride ≥ 99.99%.

5. The method according to claim 1, characterized in that, The alumina crucibles used to hold the specified molten salt and molten salt base salt are 100-ml alumina crucibles from Advalue Technology, model: AL-2100. A 250-ml alumina crucible is also used to hold the 100-ml alumina crucible to prevent the high-temperature molten salt from flowing out in case of breakage.

6. The method according to claim 1, characterized in that, The entire experiment was conducted in a glove box filled with argon protective gas, while the concentrations of H2O and O2 in the glove box were less than 1 ppm.

7. The method according to claim 1, characterized in that, The heating process parameters for the molten salt system are as follows: temperature is 650℃, and heating rate is 100℃ / h.

8. The method according to claim 7, characterized in that, After the molten salt system is heated to 650°C, it is kept at the set temperature of 650°C for 3 hours, and the molten salt system in the molten state is stirred with a tungsten rod for 3 minutes to ensure the uniformity of the molten salt system.

9. The method according to claim 1, characterized in that, The stainless steel fully threaded rod is a 316SS rod.

10. The method according to claim 1, characterized in that, Each molten salt sample was collected in 50 mg portions and stored separately in clean, sealed glass bottles. When performing concentration testing, the samples were completely dissolved in 2 vol% nitric acid and then subjected to ICP-MS elemental analysis.

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