CN113869658A - Method for selecting uncertainty analysis parameters in safety evaluation and safety evaluation method - Google Patents
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Abstract
The invention provides a method for selecting uncertain analysis parameters in radioactive waste disposal safety evaluation, which comprises the following steps: obtaining key time nodes of all key positions in the radioactive waste disposal process according to the output result of the deterministic model; acquiring main influence parameters at key time nodes of each key position from a first parameter set of a deterministic model to form a second parameter set; and counting the frequency of each parameter in the second parameter set at all the key positions, and selecting a third parameter set from the second parameter set according to a preset parameter screening standard. Further, a safety evaluation method is also provided. The selection method can improve the objectivity, accuracy and representativeness of the selection of the uncertainty analysis parameters and can reduce the quantity of the parameters of the uncertainty analysis.
Description
Technical Field
The invention relates to the field of nuclear industry, in particular to a method for selecting uncertain analysis parameters in radioactive waste disposal safety evaluation and a safety evaluation method.
Background
The near-surface radioactive waste disposal is a complex system, safety evaluation needs to be carried out to ensure the safe disposal of the near-surface radioactive waste, and the evaluation period is usually hundreds to tens of thousands of years. The safety evaluation is limited by the evolution of natural environment and the development level of science and technology for a long time sequence, a lot of uncertainties exist in safety evaluation, wherein parameter uncertainties play an important role, the safety evaluation process involves dozens of to hundreds of parameters, and the number of the parameters is increased along with the increase of the complexity and the detailed degree of an evaluation system, and may reach thousands of parameters.
The existing near-surface radioactive waste safety evaluation technology mostly adopts a conservative assumption method when uncertainty is treated, and the conservative assumption sometimes shows a situation seriously inconsistent with reality and is inconvenient to communicate and understand. Therefore, parameter uncertainty analysis is carried out on the safety evaluation of the near-surface radioactive wastes, and in the prior art, probability density functions are given to 'relevant parameters', so that uncertainty calculation is carried out. The quality of the 'relevant parameter' selection directly influences the uncertainty analysis result, and if the parameter selection is insufficient, wrong guidance can be given to influence the credibility of the safety evaluation of the near-surface disposal facility; too much parameter selection often causes too large calculation amount and dilutes the influence of key parameters.
At present, the method for selecting uncertain parameters in the safety evaluation of near-surface radioactive waste disposal comprises the following steps: one method is to subjectively select relevant parameters, but the method is too subjective and is greatly influenced by different evaluators; another approach is by sensitivity analysis of the dose produced by the public after release, but the sensitivity of the parameters changes dynamically over time over a long evaluation period, with some parameters being sensitive at the beginning of the evaluation and insensitive at the end of the evaluation, it is not convenient to determine the parameters for uncertainty analysis and to understand the uncertainty of the whole near surface radioactive waste disposal system.
Disclosure of Invention
The invention aims to solve the technical problem of the prior art and provides a method for selecting uncertain analysis parameters in radioactive waste disposal safety evaluation and a safety evaluation method. The parameters obtained by the selection method have objectivity, accuracy and representativeness, and the number of the parameters for carrying out subsequent uncertainty analysis can be reduced.
The invention provides a method for selecting uncertain analysis parameters in radioactive waste disposal safety evaluation, which comprises the following steps: obtaining key time nodes of each key position in the radioactive waste disposal process according to the output result of the deterministic model, wherein the output result comprises the corresponding relation between the release rate/concentration of each nuclide and time; obtaining parameters with main influence at key time nodes of each key position from a first parameter set of a deterministic model to form a second parameter set, wherein the first parameter set comprises a plurality of input parameters to be subjected to uncertain analysis; and counting the occurrence frequency of each parameter in the second parameter set at all key positions, and selecting a third parameter set from the second parameter set according to a preset parameter screening standard to be used as an uncertainty analysis parameter in the radioactive waste disposal safety evaluation.
Preferably, the parameters having a main influence at the key time nodes of each key location are obtained from a first parameter set of the deterministic model to form a second parameter set, specifically: and selecting parameters with main influence at the key time nodes of each key position from the first parameter set of the deterministic model by adopting a local sensitivity analysis method to form a second parameter set.
Preferably, the selecting, by using a local sensitivity analysis method, parameters having a main influence at the key time nodes of each key position from the first parameter set of the deterministic model to form the second parameter set specifically includes: successively and respectively carrying out numerical value adjustment on each parameter in a first parameter set input by the deterministic model, wherein the range of the numerical value adjustment is smaller than the product of the first proportion and the initial numerical value of the parameter; obtaining the output result of the deterministic model at the key time node of each key position after the numerical value adjustment; according to the output result and the correlation coefficient of the parameter with the numerical value adjustment, the parameter with the absolute value of the local sensitivity index larger than the first threshold is selected and determined as the parameter with the main influence at the key time node of the key position, so as to form a second parameter set.
Preferably, the counting of the occurrence frequency of each parameter in the second parameter set at all the key positions, and selecting a third parameter set from the second parameter set according to a preset parameter screening standard specifically includes: counting the frequency of each parameter appearing at each key position respectively according to the frequency of the parameter appearing when the absolute value of the local sensitivity index of each parameter at the key time node of each key position in the second parameter set is larger than a first threshold value; summing the counted frequency of each parameter respectively to obtain the accumulated frequency of each parameter at all key positions; and selecting a third parameter set from the second parameter set according to a preset parameter screening standard and an accumulated frequency, wherein the preset parameter screening standard comprises corresponding relations between each key position in the radioactive waste disposal process and a key time node, the number of released nuclides and a selection standard, and the selection standard comprises a product of the accumulated frequency which is more than or equal to the sum of the second proportion and the number of released nuclides.
Preferably, the obtaining the key time node of each key position in the radioactive waste disposal process according to the output result of the deterministic model specifically includes: according to the output result of the deterministic model of the safety evaluation, counting time nodes corresponding to the peak values of the release rate/concentration of each nuclide at each key position in the radioactive waste disposal process, wherein the key positions comprise a disposal unit/reservoir bottom release interface, a nuclide entering a saturated zone interface from an unsaturated zone, and an underground water dew point; and determining time nodes corresponding to the peak values of the release rate/concentration as key time nodes of each key position, wherein the key time nodes comprise time nodes corresponding to the total release rate peak values of all nuclides on the release interface at the bottom of the disposal unit/reservoir, time nodes corresponding to the released nuclide peak values of the nuclides entering the saturated zone interface from the unsaturated zone, and time nodes corresponding to the nuclide concentration peak values at the groundwater exposure point.
Further, the invention also provides a safety evaluation method, which comprises the following steps: obtaining a third parameter set according to the method for selecting the uncertainty analysis parameters in the radioactive waste disposal safety evaluation; assigning corresponding probability density functions to the parameters in the third parameter set respectively, and assigning corresponding fixed values to the parameters which are not overlapped with the parameters in the third parameter set in the first parameter set respectively; inputting each probability density function and each fixed value into a safety evaluation model for uncertainty analysis and calculation to obtain a distribution interval of irradiation dose to human in the radioactive waste disposal process; and calculating the irradiation dose received by the polluted object according to the distribution interval so as to obtain the safety evaluation of the polluted object.
According to the method for selecting the uncertainty analysis parameters in the radioactive waste disposal safety evaluation and the safety evaluation method, the key positions and the key time nodes thereof are obtained, the parameters with main influence at each key time node are obtained, and the parameter set for subsequent uncertainty analysis is further screened out according to the frequency of the main influence parameters appearing at each key position. The parameter set obtained by the selection method can reduce the number of parameters for uncertainty analysis in security evaluation, thereby reducing the calculated amount of uncertainty analysis; and the parameters with representative influence at the key time nodes of the key positions are objectively and accurately screened out, so that the objectivity, the accuracy and the representativeness of the selected parameters are ensured.
Drawings
FIG. 1 a: a schematic diagram of nuclide migration paths and critical locations for safety evaluation of near-surface radioactive waste disposal provided by an embodiment of the present invention (the top plate of the disposal unit/reservoir is higher than the surface);
FIG. 1 b: the schematic diagram of nuclide migration paths and key positions for safety evaluation of near-surface radioactive waste disposal provided by the embodiment of the invention (the top plate of the disposal unit/reservoir is higher than the surface of the earth, and the bottom plate is lower than the surface of the earth);
FIG. 1 c: a schematic diagram of nuclide migration paths and critical locations for safety evaluation of near-surface radioactive waste disposal provided by an embodiment of the present invention (the top plate of the disposal unit/reservoir is lower than the surface);
FIG. 2: the embodiment of the invention provides a flow chart of a method for selecting uncertainty analysis parameters in radioactive waste disposal safety evaluation;
FIG. 3: the 7 species release rate curves at the bottom of a certain position unit/library (first key position) provided by the embodiment of the invention;
FIG. 4: a nuclide release rate curve for the interface (second critical location) between the unsaturated zone and the saturated zone provided by the embodiment of the present invention;
FIG. 5: the concentration curve of released nuclide for the groundwater exposure point (the third key position) provided by the embodiment of the invention;
FIG. 6: the key time node t of the first key position provided by the embodiment of the invention1A sensitivity storm map;
FIG. 7: the key time node t of the second key position provided by the embodiment of the invention2A sensitivity storm map;
FIG. 8: the key time node t of the third key position provided by the embodiment of the invention3Sensitivity storm map.
In the figure: 1-radioactive waste disposal unit/reservoir including, but not limited to, fig. 1a built on the surface of the earth and fig. 1b radioactive waste disposal facility shallowly buried in the ground; 2-disposal unit/reservoir bottom release interface; 3-nuclides enter a saturated band interface from a non-saturated band; 4-well digging, drinking water and irrigating; 5-groundwater exposure points including, but not limited to, springs, canals, etc.; 6-earth surface; 7-groundwater level; 8-unsaturated zone; 9-saturated zone, including but not limited to diving and confined water; 10-subsurface water bottom plate including but not limited to a permeable-to-water bed, other aquifer structure below; 11-ground water flow direction; 12-species migration path schematic.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.
Example 1:
take the parameter selection for the uncertainty analysis of the safety assessment of a near-surface treatment facility treatment unit/library as an example. Assuming that the disposal unit/reservoir contains 7 nuclides (respectively labeled nuclides 1-7), the disposal unit/reservoir is located on the earth's surface 6 (as shown in fig. 1 a) or the top plate of the disposal unit/reservoir is located above the earth's surface 6, the disposal unit/reservoir bottom plate is located below the earth's surface 6 (as shown in fig. 1 b) or the disposal unit/reservoir is located below the earth's surface 6 (as shown in fig. 1 c), the released nuclide is released via the disposal unit 1 → the disposal unit/reservoir bottom release interface 2 → the unsaturated zone 8 → the nuclide is entered from the unsaturated zone interface 3 → the saturated zone 9 → along with the groundwater flow direction 11 and the nuclide migration path 12 to the groundwater exit point 5. Wherein, the groundwater level 7 and the groundwater dew point 5 are at the same level, the groundwater bottom plate 10 is under the saturation zone 9, and the well-digging drinking water 4 can also release nuclide. In this embodiment, 16 parameters to be subjected to uncertainty analysis (i.e., the input of the deterministic model is 16 parameters) are described in detail.
As shown in fig. 2, the present embodiment provides a method for selecting uncertainty analysis parameters in radioactive waste disposal safety evaluation, including:
Optionally, step 101 specifically includes steps 1011 to 1012:
In this embodiment, the input to the deterministic model is a parameter (e.g., 16 parameters to be analyzed for uncertainty), and the output is the release rate/concentration of the species generated over time (e.g., as shown in fig. 3-5), the dose of radiation generated to the human being. It should be noted that the parameters input in the deterministic model are a set of parameters with initial values (or fixed values). The parameters in this embodiment include density (substances related to density include radioactive waste barrels, cement mortar, concrete unit walls, geological bodies of geological circles), porosity, initial activity of radioactive waste, effective diffusion coefficient of concrete, distribution coefficient of nuclear elements in concrete, concrete barrier thickness, migration distance of geological circles, groundwater flow velocity, mass of fish that are irradiated by human or water that is polluted by nuclides consumed by human, volume of disposal units (which can be understood as cement houses that store radioactive waste), and the like, and the number of parameters input in a deterministic model in the safety evaluation of radioactive waste disposal is generally large.
In order to reduce the number of parameters for subsequent uncertainty analysis and avoid the influence of excessive parameters on the evaluation result due to the fact that the key parameters can be diluted, the key time nodes of the key positions are obtained, so that the main influence parameters at the key time nodes can be conveniently obtained in the subsequent processing process, and the accuracy and the representativeness of the selected parameters are improved. The key positions in this embodiment include a first key position: disposal unit/reservoir bottom release interface 2; second key position: nuclides enter a saturated zone interface 3 from an unsaturated zone; the third key position: the groundwater outlet point 5 or the well drilling drinking water 4. The key time node in this embodiment includes a key time node t of a first key location1: the total release rate peak time of the unit/reservoir bottom nuclide is treated. Because more nuclides are released at the first critical position, in order to reduce the workload of safety evaluation personnel, the critical time node of the first critical position is selectedThe peak value of the total release rate corresponds to a time node. The key time node further comprises a key time node t of a second key location2: time of peak value of unsaturated zone nucleolin release rate, key time node t2The release rate peak times of the actually released nuclides can be subdivided according to the actual treatment cases into: peak release rate t of nuclide 12-1Peak release rate t of nuclide 22-2And so on. Acquired t2-1、t2-2And the like are all used as key time nodes for subsequent analysis. The key time node also comprises a key time node t of a third key position3: the peak time of the concentration of the nuclide at the position where the human beings can contact the radionuclide, such as the groundwater outlet point 5 or the well drilling drinking water 4. Key time node t3The peak time of the nuclide concentration can be subdivided according to the actual inclusion in the actual treatment case: peak release rate t of nuclide 13-1Peak release rate t of nuclide 23-2And so on.
For example, initial values of 16 parameters are input into the deterministic model, deterministic model calculation is carried out, and time nodes corresponding to "peaks" of release rates/concentrations at each key position are obtained. As shown in fig. 3, the release rate and total release rate (sum of release rates of the species) of the 7 species at the first critical location (bottom of the treatment unit/reservoir) are shown. As shown in Table 1, the peak value and the peak occurrence time of each nuclide release rate are counted to obtain the key time node t of the first key position1The year was 172.
TABLE 1 treatment Unit/reservoir bottom nuclide Release Rate Peak and time of occurrence
As shown in FIG. 4, the release rate of the nuclide at the second critical position (the unsaturated zone enters the saturated zone), and most of the nuclide is adsorbed due to the adsorption retardation of the unsaturated zone, such as the nuclides 1, 4,6. 7 are all adsorbed and less than 10 for the release rate-2The release rate of the Bq/a nuclide is negligible, and the nuclide with the release rate lower than the preset threshold value can be specifically omitted according to the actual situation. The peak value of the release rate and the occurrence time of the second key position are counted and shown in table 2, and a key time node t of the second key position is obtained2-1443 years, t2-21720 years, t2-3The number is 221 years.
TABLE 2 peak values of the release rate of unsaturated band nucleotides and the appearance time
| Name of nuclide | Disposal reservoir bottom release rate Peak (Bq/a) | Peak appearance time (year) |
| |
1.06E+05 | 443 |
| Nuclide 3 | 1.92E+10 | 1720 |
| Nuclide 5 | 3.44E+09 | 221 |
| Total release rate | 1.92E+10 | 1720 |
As shown in fig. 5Shown are the concentration peak of the nuclide at the third critical site (groundwater dew point) and its time of occurrence. The statistical concentration peak value and the appearance time of the nuclide are shown in Table 3, and a key time node t of a third key position is obtained3-1Is 802 years, t3-2For 4238 years, t3-3It was 274 years.
TABLE 3 nuclide concentration in groundwater dew point and concentration peak appearance time
| Name of nuclide | Peak concentration value (Bq/m)3) | Peak appearance time (year) |
| |
2.03E-04 | 802 |
| |
2.26E+05 | 4238 |
| Nuclide 5 | 2.59E+03 | 274 |
| Total release rate | 1.92E+10 | 1720 |
Optionally, a second parameter set is obtained from the first parameter set by a sensitivity analysis method or other mathematical analysis method, wherein the number of parameters in the second parameter set is less than the number of parameters in the first parameter set. The sensitivity analysis method includes a local sensitivity analysis and a global sensitivity analysis, and in this embodiment, it is preferable to select parameters having a main influence at the key time node of each key position from the first parameter set of the deterministic model by using the local sensitivity analysis method to form a second parameter set.
Optionally, selecting a second parameter set from the first parameter set by using a local sensitivity analysis method, specifically including steps 1021 to 1023:
step 1021, sequentially and respectively performing numerical adjustment on each parameter in the first parameter set input by the deterministic model, wherein the range of the numerical adjustment is smaller than the product of the first proportion (such as +/-5%) and the initial value of the parameter.
And step 1022, obtaining output results of the deterministic model at the key time nodes of each key position after the numerical value adjustment.
And 1023, selecting the parameter with the absolute value of the local sensitivity index larger than the first threshold according to the output result and the correlation coefficient of the parameter with the numerical value adjustment, and determining the parameter as the parameter with main influence at the key time node of the key position so as to form a second parameter set.
In this embodiment, because the sensitivity of the parameter in the long-time evaluation period has a characteristic of dynamically changing with time, and it is avoided that some acquired parameters are sensitive at the initial stage of evaluation and insensitive at the later stage of evaluation, which ultimately affects the accuracy of uncertainty analysis, the parameters having a large impact on the output result of the deterministic model are screened out by the local sensitivity analysis method, that is, the values of all uncertainty parameters to be analyzed (for example, 16 parameters) in the deterministic model are respectively changed by ± 5% (for example, if the initial value of the parameter a in the deterministic model is 10, then the parameter a alone is used to determine whether the uncertainty of the deterministic model is large or not)And respectively taking values of 5 and 15 when the secondary parameter changes), performing deterministic model calculation, and obtaining output results corresponding to key time nodes of each key position when the parameter changes once. It should be noted that a single calculation only changes a single parameter, and the other parameters maintain the initial values in the deterministic model. Specifically, after the 16 input parameters of the deterministic model are respectively subjected to numerical adjustment according to the numerical adjustment range (± 5% of the initial value), the output results of the deterministic model at the key time nodes of each key position (namely, the 172 th year of the first key position, the 443 th year, 1720, 221 th year of the second key position, and the 802 th year, 4238, 274 th year of the third key position) after the numerical adjustment are obtained. According to the output results at each time node and the correlation coefficient of the parameter with the numerical value adjustment, the parameter with the absolute value of the local sensitivity parameter larger than a first threshold (such as 0.001) is selected and determined as the parameter with the main influence at the key time node, wherein the positive and negative of the local sensitivity parameter represent positive correlation and negative correlation. T of the first key position is obtained through calculation and analysis of a deterministic model1The main influence parameters of analyzing the release rate of all nuclides in 172 years are shown in fig. 6, wherein the main influence parameters of the release rate of the nuclide 1 include parameter 1, parameter 2, parameter 3 and parameter 4; t of the second critical position2-1443 year, t2-21720 years, t2-3The main parameters of influence of the released nuclide release rate analyzed in 221 years are shown in fig. 7, wherein the main parameters of influence of the nuclide 2 release rate include parameters 5, 6, 7, 1, 2, 3, 8; t of the third key position3-1802 years, t3-24238 years old, t3-3The main parameters of influence of 274 year released species concentration are shown in fig. 8. From the results shown in fig. 6-8, a second set of parameters (a total of 15 parameters) is obtained from the first set of parameters (a total of 16 parameters to be analyzed for uncertainty). As can be seen from step 102, the number of parameters in the second parameter set obtained by the local sensitivity analysis method is still large, some of the parameters may have little effect on safety, it is not necessary to perform uncertainty analysis subsequently, dilution of important evaluation results is easily caused when performing uncertainty analysis, and therefore, the accuracy and the quality of the parameter set obtained at this time are highThe representativeness is still not high.
And 103, counting the occurrence frequency of each parameter in the second parameter set at all key positions, and selecting a third parameter set from the second parameter set according to a preset parameter screening standard to serve as an uncertainty analysis parameter in the radioactive waste disposal safety evaluation.
In this embodiment, since the number of parameters in the second parameter set obtained in step 102 is large, an accurate and representative parameter set needs to be further obtained from the second parameter set to be used as an uncertainty analysis parameter in the radioactive waste disposal safety evaluation. The preset parameter screening standard can facilitate further selection of parameters with more representativeness and accuracy. The preset parameter screening criteria comprise corresponding relations between each key position in the radioactive waste disposal process and a key time node, the number of released nuclides and the selection criteria respectively. The selection criterion includes an accumulated frequency greater than or equal to a product of the second ratio and a sum of the number of released nuclides. Specifically, as shown in table 4, the method includes a nuclide selection method for three key positions, a key time node selection method, a reference index calculation method, a selection criterion, and an accumulated frequency. The user can select a corresponding parameter selection method according to actual needs, and the table can assist in completing the selection of the near-surface radioactive waste disposal safety evaluation uncertainty analysis parameters.
Table 4 reference table for parameter screening criteria
Optionally, step 103 specifically includes step 1031 to step 1033:
step 1031, according to the frequency of occurrence of the parameter when the absolute value of the local sensitivity index of each parameter at the key time node of each key position in the second parameter set is greater than the first threshold (e.g. 0.001), counting the frequency of occurrence of each parameter at each key position respectively.
And 1032, summing the counted frequency of each parameter respectively to obtain the accumulated frequency of each parameter at all the key positions.
And 1033, selecting a third parameter set from the second parameter set according to preset parameter screening standards and accumulated frequency.
In this embodiment, the summary statistics is performed on the parameters having main influence at the key time nodes of each key location. And counting the frequency of the occurrence of each parameter as a main influence parameter at different key positions and key time nodes. As shown in fig. 6, 7, and 8, the statistical frequency of occurrence of each parameter is shown in table 5. The selection of parameters was performed according to the selection criteria of the accumulated frequency in the screening criteria reference table (table 4) presented in this example. Namely, the first key position selects 7 nuclides N1-7, the second key position selects 3 nuclides N2-3, the third key position selects 3 nuclides N3-3, and the total accumulated frequency index N4-N1 + N2+ N3. The parameters of 30% × N4 ═ 30% × 13 ═ 3.9 times, and the cumulative frequency of the statistics obtained from table 5 was greater than 3.9 times: parameters 1, 2, 3, 4, 5, 8. These 6 parameters are the parameters (i.e., the third parameter set) selected for the uncertainty analysis in this embodiment. The number of the parameters used for the uncertainty analysis is reduced from 15 to 6, and meanwhile, the key parameter sequence of the uncertainty analysis is given through the accumulated frequency, the frequency of the parameters 1, 2 and 3 is far higher than that of other parameters, and the key parameters are focused by a safety evaluator in use. Due to the fact that key parameter sequencing of uncertainty analysis is given, safety evaluation workers of the radioactive waste disposal facility can conveniently use and carry out related work.
TABLE 5 frequency chart of important influence parameters
| First key position | Second key location | Position of the third key | Accumulated frequency | |
| Parameter 1 | 7 | 3 | 3 | 13 |
| |
6 | 2 | 1 | 9 |
| |
6 | 2 | 2 | 10 |
| Parameter 4 | 4 | 1 | 1 | 6 |
| Parameter 5 | - | 3 | 3 | 6 |
| Parameter 6 | - | 2 | 1 | 3 |
| Parameter 7 | - | 2 | 1 | 3 |
| Parameter 8 | - | 3 | 1 | 4 |
| Parameter 9 | - | - | 3 | 3 |
| Parameter 10 | - | - | 2 | 2 |
| Parameter 11 | - | - | 3 | 3 |
| Parameter 12 | - | - | 3 | 3 |
| Parameter 13 | - | - | 3 | 3 |
| Parameter 14 | - | - | 1 | 1 |
| Parameter 15 | - | - | 1 | 1 |
Note: it should be noted that, when the absolute value of the local sensitivity index is smaller than 0.001, the preset parameter screening criteria (for example, table 4) have corresponding selection criteria (for example, the frequency of the parameter is greater than or equal to 50% N1) for each key position, and the selection criteria can be used to verify whether the result obtained by screening with the cumulative frequency is correct or to deduce how to assist in selecting the parameter at each key position in the previous period after screening with the cumulative frequency. In other words, when the frequency of occurrence of a parameter as a primary influencing parameter at all critical positions exceeds the product of the third proportion (e.g., 50%) and the number of nuclides released at the critical positions, it is said that the parameter needs to be selected as a parameter for subsequent uncertainty analysis.
The method for selecting the uncertainty analysis parameters in the radioactive waste disposal safety evaluation of the embodiment selects the parameters with main influence at the key time nodes of the key positions, so as to ensure that the screened parameters have sensitivity at important moments. Further, a third parameter set is obtained according to a preset parameter screening standard on the basis of the local sensitivity analysis result and is used as an uncertainty analysis parameter in the radioactive waste disposal safety evaluation, so that the obtained parameters are parameters which play an important role in safety influence and are reasonable in quantity. The method can improve the objectivity, accuracy and representativeness of the selected parameters, can reduce the number of the parameters of uncertainty analysis, and can help a user to select the parameters by the parameter screening standard.
Example 2:
the embodiment provides a security evaluation method, which includes:
step 201, a third parameter set is obtained according to the method for selecting uncertain analysis parameters in the radioactive waste disposal safety evaluation described in embodiment 1.
Step 202, assigning corresponding probability density functions to the parameters in the third parameter set, and assigning corresponding fixed values to the parameters in the first parameter set that are not overlapped with the parameters in the third parameter set.
And 203, inputting the probability density functions and the fixed values into a safety evaluation model for uncertainty analysis and calculation to obtain a distribution interval of the irradiation dose to the human in the radioactive waste disposal process.
And 204, calculating the irradiation dose received by the polluted object according to the distribution interval so as to obtain the safety evaluation of the polluted object.
By performing security evaluation of uncertainty analysis based on the parameters selected in embodiment 1, the credibility of the security evaluation result, that is, the maximum possibility of knowing which result is obtained is determined under all the possibilities of obtaining the uncertainty parameters. In addition, the method can be used for judging whether the result of the deterministic model evaluation is feasible or not.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.
Claims (6)
1. A method for selecting uncertainty analysis parameters in radioactive waste disposal safety evaluation is characterized by comprising the following steps:
obtaining key time nodes of each key position in the radioactive waste disposal process according to the output result of the deterministic model, wherein the output result comprises the corresponding relation between the release rate/concentration of each nuclide and time;
obtaining parameters with main influence at key time nodes of each key position from a first parameter set of a deterministic model to form a second parameter set, wherein the first parameter set comprises a plurality of input parameters to be subjected to uncertain analysis;
and counting the occurrence frequency of each parameter in the second parameter set at all key positions, and selecting a third parameter set from the second parameter set according to a preset parameter screening standard to be used as an uncertainty analysis parameter in the radioactive waste disposal safety evaluation.
2. The method for selecting uncertainty analysis parameters in radioactive waste disposal safety evaluation according to claim 1, wherein the parameters having major influence at the key time nodes of each key location are obtained from a first parameter set of a deterministic model to form a second parameter set, in particular: and selecting parameters with main influence at the key time nodes of each key position from the first parameter set of the deterministic model by adopting a local sensitivity analysis method to form a second parameter set.
3. The method for selecting uncertainty analysis parameters in radioactive waste disposal safety evaluation according to claim 2, wherein the selecting parameters having major influence at key time nodes of each key location from the first parameter set of the deterministic model by using a local sensitivity analysis method to form the second parameter set comprises:
successively and respectively carrying out numerical value adjustment on each parameter in a first parameter set input by the deterministic model, wherein the range of the numerical value adjustment is smaller than the product of the first proportion and the initial numerical value of the parameter;
obtaining the output result of the deterministic model at the key time node of each key position after the numerical value adjustment;
according to the output result and the correlation coefficient of the parameter with the numerical value adjustment, the parameter with the absolute value of the local sensitivity index larger than the first threshold is selected and determined as the parameter with the main influence at the key time node of the key position, so as to form a second parameter set.
4. The method for selecting uncertainty analysis parameters in the radioactive waste disposal safety evaluation according to claim 3, wherein the counting of the occurrence frequency of each parameter in the second parameter set at all the critical positions, and selecting a third parameter set from the second parameter set according to a preset parameter screening criterion specifically comprises:
counting the frequency of each parameter appearing at each key position respectively according to the frequency of the parameter appearing when the absolute value of the local sensitivity index of each parameter at the key time node of each key position in the second parameter set is larger than a first threshold value;
summing the counted frequency of each parameter respectively to obtain the accumulated frequency of each parameter at all key positions;
selecting a third parameter set from the second parameter set according to preset parameter screening criteria and accumulated frequency, wherein the preset parameter screening criteria comprise corresponding relations between each key position in the radioactive waste disposal process and a key time node, the number of released nuclides and a selection criterion respectively,
the selection criterion includes an accumulated frequency greater than or equal to a product of the second ratio and a sum of the number of released nuclides.
5. The method for selecting uncertainty analysis parameters in radioactive waste disposal safety evaluation according to claim 4, wherein obtaining the key time nodes of each key position in the radioactive waste disposal process according to the output result of the deterministic model specifically comprises:
according to the output result of the deterministic model of the safety evaluation, counting time nodes corresponding to the peak values of the release rate/concentration of each nuclide at each key position in the radioactive waste disposal process, wherein the key positions comprise a disposal unit/reservoir bottom release interface, a nuclide entering a saturated zone interface from an unsaturated zone, and an underground water dew point;
and determining time nodes corresponding to the peak values of the release rate/concentration as key time nodes of each key position, wherein the key time nodes comprise time nodes corresponding to the total release rate peak values of all nuclides on the release interface at the bottom of the disposal unit/reservoir, time nodes corresponding to the released nuclide peak values of the nuclides entering the saturated zone interface from the unsaturated zone, and time nodes corresponding to the nuclide concentration peak values at the groundwater exposure point.
6. A security evaluation method is characterized by comprising:
the method for selecting uncertainty analysis parameters in the radioactive waste disposal safety evaluation according to any one of claims 1 to 5 to obtain a third parameter set;
assigning corresponding probability density functions to the parameters in the third parameter set respectively, and assigning corresponding fixed values to the parameters which are not overlapped with the parameters in the third parameter set in the first parameter set respectively;
inputting each probability density function and each fixed value into a safety evaluation model for uncertainty analysis and calculation to obtain a distribution interval of irradiation dose to human in the radioactive waste disposal process;
and calculating the irradiation dose received by the polluted object according to the distribution interval so as to obtain the safety evaluation of the polluted object.
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