Method for determining actual internal pressure of heat source in service environment

Abstract

The embodiment of the invention provides a method for determining the actual internal pressure of a heat source in a service environment, and the method is used for a sealed radioactive isotope heat source, and comprises the following steps: setting the tentative internal pressure of the heat source, and calculating and obtaining the gas storage volume in the heat source through finite element simulation according to the tentative internal pressure; obtaining the calculated internal pressure of the heat source through a state equation according to the mole number of the released gas, the temperature and the gas storage volume; and determining the actual internal pressure according to the residual error of the tentative internal pressure and the calculated internal pressure and a residual error threshold value. The method for determining the actual internal pressure of the heat source is good in precision.

Description

Technical Field

[0001] The present application relates to the field of nuclear engineering technology, and in particular to a method for determining the actual internal pressure of a heat source in a service environment. Background Art

[0002] A radioactive isotope heat source (abbreviated as isotope heat source) is a device that uses the decay energy of radioactive nuclides to provide heat energy and is widely used in the field of deep space exploration. Isotope heat sources have a service life of several decades. Since the radioactive nuclides inside the isotope heat source are extremely toxic substances, they are generally sealed with metal cladding. For α-decay nuclides with high energy density (such as Pu-238, Po-210, etc.), helium will be produced after the nuclides decay. As time accumulates, the amount of helium gradually increases. Since the sealed isotope heat source does not have an exhaust function, the internal pressure begins to increase after the heat source is produced.

[0003] For isotope heat sources that adopt a sealed design, it is necessary to accurately calculate the internal pressure of the heat source, and then analyze the pressure-bearing capacity of the heat source shell based on the internal pressure to evaluate the safety of the heat source.

[0004] The current method for calculating the internal pressure of the heat source assumes that the storage volume V of helium is constant, and directly obtains the internal pressure of the heat source through the gas state equation. However, due to the correlation between the gas storage volume V and the safety assessment waiting period t, temperature T and mechanical properties of the cladding material of the heat source, the method for determining the internal pressure of the isotope heat source in related technologies has poor accuracy and cannot meet application requirements. Summary of the invention

[0005] In view of this, the main purpose of the embodiments of the present application is to provide a method for determining the actual internal pressure of a heat source in a service environment with better accuracy.

[0006] To achieve the above purpose, the technical solution of the embodiment of the present application is implemented as follows:

[0007] The embodiment of the present application provides a method for determining the actual internal pressure of a heat source in a service environment, which is used for a sealed radioisotope heat source. The method for determining the actual internal pressure includes the following steps:

[0008] Setting a test internal pressure of the heat source, and obtaining a gas storage volume of the heat source according to the test internal pressure;

[0009] Obtaining a calculated internal pressure of the heat source based on the number of moles of released gas, the gas temperature, and the gas storage volume;

[0010] The actual internal pressure is determined according to a residual between the tentative internal pressure and the calculated internal pressure and a residual threshold.

[0011] In one implementation manner, determining the actual internal pressure according to the residual between the trial internal pressure and the calculated internal pressure and a residual threshold value specifically includes:

[0012] Comparing the absolute value of the residual with the residual threshold;

[0013] If the absolute value of the residual is greater than the residual threshold, the value of the calculated internal pressure is used as the value of the trial internal pressure after iteration, the calculated internal pressure of the heat source corresponding to the trial internal pressure after iteration is obtained, and the absolute value of the residual between the trial internal pressure after iteration and the calculated internal pressure is compared with the residual threshold, and so on, the trial internal pressure and the residual are continuously updated through iterative calculation;

[0014] If the absolute value of the residual is less than the residual threshold, the calculated internal pressure is determined as the actual internal pressure.

[0015] In one embodiment, the heat source includes a cladding, and the actual internal pressure determination and safety assessment method further includes the following steps:

[0016] The actual stress of the heat source is calculated and obtained according to the actual internal pressure, and the safety factor of the heat source is obtained according to the actual stress and the allowable stress of the cladding.

[0017] In one embodiment, the step of obtaining the calculated internal pressure of the heat source according to the molar number of released gas, the gas temperature and the gas storage volume specifically includes:

[0018] The calculated internal pressure of the heat source is obtained according to the ideal gas state equation, which is:

[0019]

[0020] Wherein, P is the calculated internal pressure, N is the number of moles of the gas, R is the Avogadro constant, T r is the gas temperature, V try is the gas storage volume.

[0021] In one embodiment, the heat source includes an isotope heat source, and the method for determining the actual internal pressure further includes the following steps:

[0022] The molar number of gas released by the isotope heat source is determined according to the initial molar number of the nuclides of the isotope heat source, the safety evaluation waiting period of the isotope heat source and the half-life of the nuclides.

[0023] In one implementation, the calculation formula for determining the molar number of the gas is:

[0024]

[0025] Wherein, N is the molar number of the gas, N0 is the initial molar number of the nuclide, T 1 / 2 is the half-life of the nuclide, and t is the safety evaluation waiting period of the isotope heat source.

[0026] In one embodiment, the calculation formula for determining the initial molar number of the nuclide is:

[0027]

[0028] Wherein, N0 is the initial molar number of the nuclide, W0 is the initial heating power of the isotope heat source, C is the specific power of the nuclide, and M is the molar mass of the nuclide.

[0029] In one embodiment, the heat source includes a cladding, and the method for determining the actual internal pressure further includes the following steps:

[0030] Acquire the use environment temperature of the heat source, acquire the heat distribution of the cladding and determine the gas temperature of the heat source and the temperature of the cladding according to the heating power of the isotope heat source and the use environment temperature;

[0031] Obtaining the stress and deformation of the cladding according to the test internal pressure and the temperature of the cladding;

[0032] The coordinate information of the finite element nodes after the cladding is deformed is extracted, a geometric model of the cladding after the deformation is established, and the gas storage volume is obtained.

[0033] In one embodiment, the method for determining the actual internal pressure further comprises the following steps:

[0034] The heating power is determined according to the initial heating power of the isotope heat source, the safety evaluation waiting period of the isotope heat source and the half-life of the nuclide.

[0035] In one implementation, the calculation formula for determining the heating power is:

[0036]

[0037] Wherein, W is the heating power, W0 is the initial heating power of the isotope heat source, T 1 / 2 is the half-life of the nuclide, and t is the safety evaluation waiting period of the isotope heat source.

[0038] The embodiment of the present application provides a method for determining the actual internal pressure of a heat source in a service environment, which is used for a sealed radioisotope heat source. The method for determining the actual internal pressure includes the following steps: setting a test internal pressure of the heat source, and obtaining the gas storage volume of the heat source according to the test internal pressure; obtaining the calculated internal pressure of the heat source according to the number of moles of released gas, the gas temperature, and the gas storage volume; and determining the actual internal pressure according to the residual of the test internal pressure and the calculated internal pressure and the residual threshold. Thus, by comparing the residual of the test internal pressure and the calculated internal pressure with the residual threshold, the error of the calculated actual internal pressure can be reduced, making it closer to the actual value, so that the internal pressure safety of the sealed radioisotope heat source can be more accurately evaluated. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a flow chart of a method for determining the actual internal pressure of a heat source in a service environment according to the first embodiment of the present application;

[0040] Figure 2 This is a schematic structural diagram of a heat source according to a second embodiment of the present application;

[0041] Figure 3 This is a flow chart of a method for determining the actual internal pressure of a heat source in a service environment according to the third embodiment of the present application;

[0042] Figure 4 For this application Figure 3 Iterative calculation process of internal pressure in ;

[0043] Figure 5 For this application Figure 3 The changing process of iterative calculation residual in .

[0044] Description of Reference Numerals

[0045] 1. Source core; 2. Inner sealed cladding; 3. Outer sealed cladding; 4. Insulation layer; 5. Protective layer. DETAILED DESCRIPTION

[0046] See also Figure 2 The sealed radioactive isotope heat source includes a source core 1, an inner sealed cladding 2, an outer sealed cladding 3, an insulation layer 4 and a protective layer 5. According to the radionuclide decay equation and the ideal gas state equation, the relationship between the cladding internal pressure P and the storage or safety assessment waiting period t, the gas storage volume V, and the temperature T can be derived as follows:

[0047]

[0048] Among them, R, λ, T 1 / 2are constants, namely Avogadro's constant, decay constant and half-life of the nuclide, N0 is the initial molar number of the nuclide, V is the helium storage volume, which refers to the free space volume after deducting the volume of the source core itself from the internal space volume of the metal sealing shell.

[0049] For a fixed-model isotope heat source, its storage volume V at the initial moment is known. As the storage time or service time of the pressure heat source increases, the helium released from the nuclear core gradually accumulates, increasing the pressure inside the heat source. Since there is a complex relationship between the gas storage volume V and the safety assessment waiting period t, temperature T and mechanical properties of the cladding material, the functional relationship between V and pressure P cannot be determined by theoretical or empirical formulas.

[0050] The analysis method used in the relevant technology assumes that the storage volume V of helium is constant, that is, there is no mutual influence between V and the internal pressure P, so the pressure inside the heat source can be directly calculated according to (Equation 1). This analysis method is suitable for the situation where the helium yield is low in the early stage of the heat source. At this time, the deformation of the cladding material is extremely small, and the helium storage volume V hardly changes, so a more accurate analysis result can be obtained. However, as time goes on, the accumulation of internal helium causes the cladding to expand and the material to undergo plastic deformation, resulting in a large change in the helium storage volume V in the cladding. Therefore, during the period of long-term storage or service of the heat source, this internal pressure analysis method will have a large error.

[0051] An embodiment of the present application provides a method for determining the actual internal pressure of a heat source in a service environment, which is used for a sealed radioisotope heat source. Figure 1 , the method for determining the actual internal pressure includes the following steps:

[0052] Step S1: setting the test internal pressure of the heat source, and obtaining the gas storage volume of the heat source according to the test internal pressure.

[0053] Step S2: Obtain the calculated internal pressure of the heat source according to the molar number of released gas, the gas temperature and the gas storage volume.

[0054] Step S3: determining the actual internal pressure according to the residual between the tentative internal pressure and the calculated internal pressure and a residual threshold.

[0055] Specifically, the trial internal pressure refers to a pressure value randomly set in the process of determining the actual internal pressure of the heat source.

[0056] The gas storage volume refers to the size of the space in the heat source that can accommodate gas under the condition of set test internal pressure.

[0057] The gas mole number refers to the amount of gas generated and released by the isotope heat source within the heat source during the safety assessment waiting period.

[0058] The gas temperature refers to the temperature of the gas in the heat source at the end of the safety assessment waiting period.

[0059] The calculated internal pressure refers to the internal pressure value corresponding to the heat source during the safety evaluation waiting period, which is calculated based on the number of gas moles, gas temperature and gas storage volume.

[0060] Exemplarily, the calculated internal pressure of the heat source is obtained according to the moles of released gas, the gas temperature and the gas storage volume, specifically including:

[0061] The calculated internal pressure of the heat source is obtained according to the ideal gas state equation, which is:

[0062]

[0063] Where P is the calculated internal pressure, N is the number of moles of gas, R is Avogadro's constant, and T r is the gas temperature, V try is the gas storage volume.

[0064] The residual refers to the difference between the trial internal pressure and the calculated internal pressure. By comparing the residual with the residual threshold, the accuracy of the calculated internal pressure and the degree of its closeness to the actual internal pressure can be evaluated.

[0065] The residual threshold refers to a preset allowable residual range value. When the residual is within the residual threshold range, it can be considered that the calculated internal pressure is close enough to the actual internal pressure.

[0066] The embodiment of the present application provides a method for determining the actual internal pressure of a heat source in a service environment, which is used for a sealed radioisotope heat source. The method for determining the actual internal pressure includes the following steps: setting a test internal pressure of the heat source, and obtaining the gas storage volume of the heat source according to the test internal pressure; obtaining the calculated internal pressure of the heat source according to the number of moles of released gas, the gas temperature, and the gas storage volume; and determining the actual internal pressure according to the residual of the test internal pressure and the calculated internal pressure and the residual threshold. Thus, by comparing the residual of the test internal pressure and the calculated internal pressure with the residual threshold, the error of the calculated actual internal pressure can be reduced, making it closer to the actual value, so that the internal pressure safety of the sealed radioisotope heat source can be more accurately evaluated.

[0067] In one embodiment, please refer to Figure 1 , determining the actual internal pressure according to the residual between the trial internal pressure and the calculated internal pressure and the residual threshold, specifically includes the following steps:

[0068] The absolute value of the residual is compared with the residual threshold, and so on, and the trial internal pressure and residual are continuously updated through iterative calculation.

[0069] If the absolute value of the residual is greater than the residual threshold, the calculated internal pressure is used as the value of the trial internal pressure after iteration, the gas storage volume of the heat source corresponding to the trial internal pressure after iteration and the calculated internal pressure are obtained, and the absolute value of the residual between the trial internal pressure after iteration and the calculated internal pressure is compared with the residual threshold.

[0070] If the absolute value of the residual is less than the residual threshold, the calculated internal pressure is determined as the actual internal pressure.

[0071] Therefore, by iteratively comparing the residual and the residual threshold, the calculated internal pressure can be gradually made close to the actual internal pressure, so that the actual pressure inside the heat source can be determined more accurately, the internal pressure deviation caused by calculation errors can be reduced, and the internal pressure safety of the heat source can be evaluated more accurately.

[0072] Specifically, the comparison between the residual and the residual threshold refers to the comparison between the absolute value of the residual and the residual threshold.

[0073] When the absolute value of the residual is greater than the residual threshold, it means that the current calculated internal pressure is significantly different from the trial internal pressure, and the calculated internal pressure is not accurate enough. At this time, the value of the calculated internal pressure is used as the new trial internal pressure, and the gas storage volume and the new calculated internal pressure under the new trial internal pressure are recalculated. The absolute value of the residual between the new calculated internal pressure and the new trial internal pressure and the residual threshold are compared. The iterative process is repeated until the absolute value of the residual between the new calculated internal pressure and the new trial internal pressure is less than the residual threshold, at which point the new calculated internal pressure is determined to be the actual internal pressure.

[0074] In one embodiment, please refer to Figure 1 , the heat source includes the cladding, and the method for determining the actual internal pressure also includes the following steps:

[0075] The actual stress of the heat source is calculated and obtained according to the actual internal pressure, and the safety factor of the heat source is obtained according to the actual stress and the allowable stress of the cladding.

[0076] Therefore, by calculating the safety factor, the safety of the heat source can be quantitatively evaluated, allowing engineers and operators to intuitively understand the safety status of the heat source under the current internal pressure, and then discover potential safety hazards in advance and prevent accidents caused by excessive internal pressure or insufficient cladding strength.

[0077] Specifically, the calculation formula of the safety factor is:

[0078]

[0079] Where n is the safety factor, σ 许用 is the allowable stress value of the heat source shell of the safety factor, σ 实际 The safety factor is the actual stress value of the heat source cladding at the end of the safety evaluation waiting period.

[0080] In one embodiment, please refer to Figure 1 , the heat source includes an isotope heat source, and the method for determining the actual internal pressure also includes the following steps:

[0081] The molar number of gas released by the isotope heat source is determined based on the initial molar number of the nuclides in the isotope heat source, the safety assessment waiting period of the isotope heat source and the half-life of the nuclides.

[0082] Specifically, the initial molar number of nuclides refers to the amount of radioactive isotope material input during the production of the heat source.

[0083] The waiting period for safety assessment of isotope heat sources refers to the length of time from the production of the heat source to the time when its safety needs to be assessed. During this period, the isotope heat source may be in normal storage, transportation or service.

[0084] The half-life of a nuclide is the time required for half of the nuclei of the nuclide to decay.

[0085] The gas mole number refers to the amount of gas produced and released during the use of isotope heat source due to processes such as radioactive isotope decay.

[0086] It should be noted that radioactive isotopes produce gas during the decay process. As time goes by, the gas continues to accumulate, and the amount of gas produced is quantified by the number of moles of gas.

[0087] In one embodiment, please refer to Figure 1 , the calculation formula to determine the number of gas moles is:

[0088]

[0089] Where N is the number of moles of gas, N0 is the initial number of moles of nuclide, T 1 / 2 is the half-life of the nuclide, and t is the waiting period for safety evaluation of the isotope heat source.

[0090] In one embodiment, please refer to Figure 1 , the calculation formula for determining the initial molar number of the nuclide is:

[0091]

[0092] Among them, N0 is the initial molar number of the nuclide, W0 is the initial heating power of the isotope heat source, C is the specific power of the nuclide, and M is the molar mass of the nuclide.

[0093] Specifically, the initial heat generation power refers to the decay heat power of the radioactive nuclides inside the heat source.

[0094] In one embodiment, please refer to Figure 1, the heat source includes the cladding, and the method for determining the actual internal pressure and the safety assessment also includes the following steps:

[0095] The operating environment temperature of the heat source is obtained, and based on the heating power of the isotope heat source and the operating environment temperature, the thermal distribution of the cladding is obtained and the gas temperature of the heat source and the temperature of the cladding are determined.

[0096] The stress and deformation of the cladding are obtained based on the test internal pressure and the temperature of the cladding.

[0097] The coordinate information of the finite element nodes after the cladding deformation is extracted, and the geometric model of the cladding deformation is constructed through the processor to extract the gas storage volume.

[0098] Therefore, by using the ambient temperature and heating power to analyze the thermal distribution of the heat source's cladding and obtaining the stress and deformation of the heat source's cladding, the gas storage volume of the heat source can be obtained more accurately, thereby more accurately determining the internal pressure, and then more accurately evaluating the internal pressure safety of the sealed radioactive isotope heat source.

[0099] Specifically, the operating environment temperature refers to the temperature of the surrounding environment at the end of the heat source safety evaluation waiting period.

[0100] The heating power refers to the heating power of the isotope heat source at the end of the safety evaluation waiting period.

[0101] There is no limit to the method for determining the gas temperature and the cladding temperature. For example, according to the heating power and the ambient temperature, the finite element steady-state thermal analysis method is used to calculate the cladding heat distribution and determine the gas temperature and the cladding temperature.

[0102] The temperature of the cladding refers to the temperature of the heat source cladding itself.

[0103] There is no limitation on the method for obtaining the stress and deformation of the cladding, for example, the stress and deformation of the cladding can be obtained by a finite element analysis method.

[0104] The structural type of the processor is not limited, as long as the gas storage volume under the test internal pressure can be obtained according to the stress and deformation of the cladding.

[0105] For example, the processor includes CAD software. The geometric model of the heat source after plastic deformation is reconstructed by the CAD software to obtain the gas storage volume in the cladding under the test internal pressure.

[0106] In one embodiment, please refer to Figure 1 , the method for determining the actual internal pressure also includes the following steps:

[0107] The heating power is determined based on the initial heating power of the isotope heat source, the safety evaluation waiting period of the isotope heat source, and the half-life of the nuclide. Therefore, by accurately calculating the heating power, more accurate data can be provided for subsequent thermal analysis.

[0108] In one embodiment, please refer to Figure 1 , the calculation formula to determine the heating power is:

[0109]

[0110] Where W is the heating power at the end of the safety assessment waiting period, W0 is the initial heating power of the isotope heat source, T 1 / 2 is the half-life of the nuclide, and t is the waiting period for safety evaluation of the isotope heat source.

[0111] In a specific embodiment, please refer to Figure 3 , the cladding deformation is calculated by combining theoretical formula with finite element simulation, and the internal pressure value of the cladding of the heat source at a specific time point and environment is calculated through self-consistent iteration. The specific steps include:

[0112] S1: Determine the initial molar number of the radioactive nuclides in the isotope heat source. The initial molar number can be calculated based on the initial heating power of the isotope heat source, the specific power of the nuclides and the molar mass of the nuclides. The calculation formula is:

[0113]

[0114] Among them, N0 is the initial molar number of the nuclide, W0 is the initial heating power of the isotope heat source, C is the specific power of the nuclide, and M is the molar mass of the nuclide.

[0115] S2: Determine the safety evaluation waiting period of the isotope heat source, and calculate the heat generation power and the number of moles of released gas at the end of the safety evaluation waiting period of the nuclide according to the decay equation. The calculation formulas are:

[0116]

[0117] Where W is the heating power at the end of the safety assessment waiting period, W0 is the initial heating power of the isotope heat source, T 1 / 2 is the half-life of the nuclide, and t is the waiting period for safety evaluation of the isotope heat source.

[0118]

[0119] Where N is the number of moles of gas, N0 is the initial number of moles of nuclide, T 1 / 2 is the half-life of the nuclide, and t is the waiting period for safety evaluation of the isotope heat source.

[0120] S3: According to the heating power and the ambient temperature, the finite element steady-state thermal analysis method is used to calculate the cladding heat distribution and determine the gas temperature and metal cladding temperature.

[0121] S4: Assuming the trial internal pressure at the end of the safety assessment waiting period, the finite element analysis method is used to calculate the stress and deformation of the heat source cladding.

[0122] S5: Extract the coordinate information of the finite element nodes of the cladding after deformation, use CAD software to reconstruct the geometric model after plastic deformation, and obtain the gas storage volume in the cladding under the action of the test internal pressure.

[0123] S6: According to the ideal gas state equation, the internal pressure is calculated as follows:

[0124]

[0125] Where P is the calculated internal pressure, N is the number of moles of gas, R is Avogadro's constant, and T r is the gas temperature, V try is the gas storage volume.

[0126] S7: According to the absolute value of the residual between the trial internal pressure and the calculated internal pressure, determine whether the calculated internal pressure is the actual internal pressure. If it is satisfied, the calculated internal pressure is obtained to be the actual internal pressure. If not, the calculated internal pressure is set equal to the new trial internal pressure, and then return to S4 for the next round of analysis to obtain a new calculated internal pressure, until the absolute value of the residual between the new trial internal pressure and the new calculated internal pressure meets the self-consistent condition, which is:

[0127]

[0128] Where P is the calculated internal pressure, P try is the test internal pressure, and δ is the residual threshold.

[0129] S8: The stress distribution of the heat source cladding under the actual internal pressure is calculated by the finite element analysis method, and the safety factor of the cladding is calculated by the safety factor method to evaluate the internal pressure safety of the heat source. The safety factor is expressed as:

[0130]

[0131] Where n is the safety factor, σ 许用 is the allowable stress value of the heat source shell of the safety factor, σ 实际 The safety factor is the actual stress value of the heat source cladding at the end of the safety evaluation waiting period.

[0132] Therefore, by adopting a self-consistent iterative calculation method combining finite element simulation with theoretical calculation, there is no need to spend effort to construct a complex functional relationship between the internal pressure of the heat source and the internal gas storage volume. It is possible to accurately calculate the internal pressure of a sealed isotope heat source at a specific time point during its life cycle and under various temperature environments, and thus more accurately evaluate the internal pressure safety of a sealed radioactive isotope heat source.

[0133] In a specific embodiment, please refer to Figure 3 , Figure 4 and Figure 5 Taking the Pu-238 isotope heat source as an example, the actual internal pressure of the heat source is calculated and the safety of the heat source is evaluated, including:

[0134] The initial power of the heat source is 4W, the specific power is 0.55W / g, the heat source nuclide is Pu-238, and the half-life is 87.7 years. The calculated molar number of the initial nuclide is N0=4 / 0.55 / 238=0.03055mol; the safety evaluation waiting period t of the isotope heat source is 10 years. The heat generation power W of the nuclide at the end of the safety evaluation waiting period and the molar number of He atoms released are calculated according to the decay equation, N=0.00232mol, W=3.696W; the operating ambient temperature of the heat source is 1100℃. Based on the thermal conductivity data of the materials of each component of the heat source, the finite element steady-state thermal analysis method is adopted to establish a steady-state thermal analysis calculation model, and the reference temperature of helium in the heat source is calculated to be 1135℃; the finite element steady-state mechanics method is adopted, the initial trial internal pressure is given as 10Mpa, the stress and deformation of the heat source cladding are calculated, and the convergence residual of the calculation is set to 0.05MPa. The final cladding internal pressure obtained through self-consistent cycle iteration is 33.9 MPa. Table 1 shows the various parameters obtained in the iterative calculation process.

[0135] Table 1 Various parameters obtained by iterative calculation process

[0136]

[0137] The allowable stress of the metal cladding material is 335 MPa. The finite element method is used to calculate the stress-strain data of the heat source cladding under an internal pressure of 33.9 MPa, and the maximum stress of the cladding is obtained to be 208 MPa, so the safety factor n = 335 / 208 = 1.61.

[0138] In the description of the present application, the description with reference to the terms "in one embodiment", "in some embodiments", "in a specific embodiment", or "exemplary" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present application. In the present application, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine different embodiments or examples described in the present application and the features of different embodiments or examples without contradiction.

[0139] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A method for determining the actual internal pressure of a heat source in a service environment, for use in a sealed radioisotope heat source, characterized in that: The method for determining the actual internal pressure comprises the following steps: Setting a test internal pressure of the heat source, and obtaining a gas storage volume of the heat source according to the test internal pressure; Obtaining a calculated internal pressure of the heat source based on the number of moles of released gas, the gas temperature, and the gas storage volume; The actual internal pressure is determined according to a residual between the tentative internal pressure and the calculated internal pressure and a residual threshold.

2. The method for determining the actual internal pressure according to claim 1, characterized in that: The determining the actual internal pressure according to the residual between the trial internal pressure and the calculated internal pressure and a residual threshold value specifically includes: Comparing the absolute value of the residual with the residual threshold; If the absolute value of the residual is greater than the residual threshold, the value of the calculated internal pressure is used as the value of the trial internal pressure after iteration, the gas storage volume of the heat source corresponding to the trial internal pressure after iteration and the calculated internal pressure are obtained, and the absolute value of the residual between the trial internal pressure after iteration and the calculated internal pressure is compared with the residual threshold; If the absolute value of the residual is less than the residual threshold, the calculated internal pressure is determined as the actual internal pressure.

3. The method for determining the actual internal pressure according to claim 1 or 2, characterized in that: The heat source includes a cladding, and the method for determining the actual internal pressure also includes the following steps: The actual stress of the heat source is calculated and obtained according to the actual internal pressure, and the safety factor of the heat source is obtained according to the actual stress and the allowable stress of the cladding.

4. The method for determining the actual internal pressure according to claim 1 or 2, characterized in that: The step of obtaining the calculated internal pressure of the heat source according to the molar number of the released gas, the gas temperature and the gas storage volume specifically includes: The calculated internal pressure of the heat source is obtained according to the ideal gas state equation, which is: Wherein, P is the calculated internal pressure, N is the number of moles of the gas, R is the Avogadro constant, T r is the gas temperature, V try is the gas storage volume.

5. The method for determining the actual internal pressure according to claim 4, characterized in that: The heat source includes an isotope heat source, and the method for determining the actual internal pressure further includes the following steps: The molar number of gas released by the isotope heat source is determined according to the initial molar number of the nuclides of the isotope heat source, the safety evaluation waiting period of the isotope heat source and the half-life of the nuclides.

6. The method for determining the actual internal pressure according to claim 5, characterized in that: The calculation formula for determining the molar number of the gas is: Wherein, N is the molar number of the gas, N0 is the initial molar number of the nuclide, T 1 / 2 is the half-life of the nuclide, and t is the safety evaluation waiting period of the isotope heat source.

7. The method for determining the actual internal pressure according to claim 5, characterized in that: The calculation formula for determining the initial molar number of the nuclide is: Wherein, N0 is the initial molar number of the nuclide, W0 is the initial heating power of the isotope heat source, C is the specific power of the nuclide, and M is the molar mass of the nuclide.

8. The method for determining the actual internal pressure according to claim 4, characterized in that: The heat source includes a cladding, and the method for determining the actual internal pressure also includes the following steps: Acquire the use environment temperature of the heat source, acquire the heat distribution of the cladding and determine the gas temperature of the heat source and the temperature of the cladding according to the heating power of the isotope heat source and the use environment temperature; Obtaining the stress and deformation of the cladding according to the test internal pressure and the temperature of the cladding; The coordinate information of the finite element nodes after the cladding is deformed is extracted, a geometric model of the cladding after the deformation is established through a processor, and the gas storage volume is obtained.

9. The method for determining the actual internal pressure according to claim 8, characterized in that: The method for determining the actual internal pressure also includes the following steps: The heating power is determined according to the initial heating power of the isotope heat source, the safety evaluation waiting period of the isotope heat source and the half-life of the nuclide.

10. The method for determining the actual internal pressure according to claim 9, characterized in that: The calculation formula for determining the heating power is: Wherein, W is the heating power at the end of the safety evaluation waiting period, W0 is the initial heating power of the isotope heat source, T 1 / 2 is the half-life of the nuclide, and t is the safety evaluation waiting period of the isotope heat source.

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