CN116994785A - Method for measuring burnup depth of fuel element of pebble-bed reactor on line - Google Patents
Method for measuring burnup depth of fuel element of pebble-bed reactor on line Download PDFInfo
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- CN116994785A CN116994785A CN202311145257.1A CN202311145257A CN116994785A CN 116994785 A CN116994785 A CN 116994785A CN 202311145257 A CN202311145257 A CN 202311145257A CN 116994785 A CN116994785 A CN 116994785A
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- 239000000446 fuel Substances 0.000 title claims abstract description 61
- 238000000034 method Methods 0.000 title claims abstract description 16
- 230000000694 effects Effects 0.000 claims abstract description 64
- 239000003758 nuclear fuel Substances 0.000 claims abstract description 6
- 238000001228 spectrum Methods 0.000 claims description 21
- 230000004992 fission Effects 0.000 claims description 14
- 238000009826 distribution Methods 0.000 claims description 5
- 238000004088 simulation Methods 0.000 claims description 5
- 238000004364 calculation method Methods 0.000 claims description 4
- 238000012937 correction Methods 0.000 claims description 4
- 229910052732 germanium Inorganic materials 0.000 claims description 4
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 4
- 230000005855 radiation Effects 0.000 claims description 4
- 238000005259 measurement Methods 0.000 abstract description 5
- 239000008188 pellet Substances 0.000 description 4
- 238000001816 cooling Methods 0.000 description 3
- 229910052770 Uranium Inorganic materials 0.000 description 2
- 230000005251 gamma ray Effects 0.000 description 2
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004422 calculation algorithm Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 229910052572 stoneware Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C17/00—Monitoring; Testing ; Maintaining
- G21C17/10—Structural combination of fuel element, control rod, reactor core, or moderator structure with sensitive instruments, e.g. for measuring radioactivity, strain
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C17/00—Monitoring; Testing ; Maintaining
- G21C17/10—Structural combination of fuel element, control rod, reactor core, or moderator structure with sensitive instruments, e.g. for measuring radioactivity, strain
- G21C17/108—Measuring reactor flux
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Monitoring And Testing Of Nuclear Reactors (AREA)
Abstract
The application provides a method for measuring the burnup depth of a fuel element of a pebble-bed reactor on line, and relates to the technical field of pebble-bed high-temperature gas cooled reactor fuel element measurement. The application is realized by measuring 134 Cs and 95 the fuel abundance is determined by the activity of Zr, and then by 134 The activity of Cs was calculated as burnup. Compared with the prior art 137 661.66keV of Cs, the application 134 The 795keV of Cs is located in a higher energy region, the background count is obviously lower, and no strong interference nuclides exist nearby, so that the accurate activity is easy to measure, and further the burnup is obtained. And is also provided with 134 The activity of Cs increases in an ultra-linear manner along with the deepening of burnup, and high-precision burnup data can be easily measured in a high burnup area, so that the method has realizability for measuring the burnup condition of the fuel element of the pebble-bed reactor.
Description
Technical Field
The application relates to the technical field of measurement of fuel elements of a pebble-bed high-temperature gas cooled reactor, in particular to a method for measuring the burnup depth of the fuel elements of the pebble-bed reactor on line.
Background
The nuclear power station of Shandong Shi island bay in China is built with a high-temperature gas cooled Reactor, adopts a ball bed modular Reactor core structure (High Temperature gas-cooled Reactor-Pebble bed Modules, HTR-PM), adopts fuel balls with the abundance of 4.2% for initial charge, and adopts fuel balls with the abundance of 8.5% for subsequent charge. After the fuel ball of the fuel ball briefly measures the gamma energy spectrum outside the reactor, the fuel ball passes through 137 The burning depth of the fuel ball is calculated by the activity of Cs 95 Judging the initial abundance of uranium by the activity of Zr, and further judging that the burnup depth isIf the fuel ball meets the waste standard, the fuel ball is subjected to re-stacking irradiation or waste treatment, and the principle is shown in figure 1.
This approach has the advantage of simplicity of the algorithm because 137 The activity of Cs is basically proportional to the burnup depth, and the burnup depth is easily calculated by proper correction after measuring the activity. However, since the cooling time from the ejection of the fuel pellet to the measurement is usually less than 10 days, there are several fission products of short life in the fuel pellet, in 137 The Cs has a plurality of strong interference peaks near the characteristic peak energy 661.6keV, and is easy to pair 137 The measurement of Cs causes serious interference, and it is difficult to obtain accurate and reliable measurement in a short time (usually less than 1 minute) 137 The Cs activity, which is difficult to measure the burning depth of the fuel pellet, is a great need for developing new measurement techniques.
Disclosure of Invention
The application aims to provide a method for measuring the burnup depth of a fuel element of a pebble-bed reactor on line, which has the advantages of easiness in detection and high burnup data precision.
In order to solve the technical problems, the application adopts the technical scheme that:
the application provides a method for measuring the burnup depth of a fuel element of a pebble-bed reactor on line, which comprises the following steps:
s1, modeling a pebble-bed reactor fuel element, and the distribution and boundary conditions in the reactor, and performing neutron transport Meng Ka simulation to obtain an in-reactor neutron energy spectrum phi and obtain an in-reactor average neutron fluence rate according to reactor power;
s2, calculating the contents of the two kinds of abundant fuel balls by utilizing neutron energy spectrum, average neutron fluence rate and fission section along with neutron energy change curve 235 U、 238 U、 239 The number of Pu atoms and the burning depth change curve along with the irradiation time;
s3, combining the accumulated fission yield-neutron energy relation curve, and calculating the positions of the two abundance fuel spheres 133 Cs、 95 A change curve of atomic number and activity of Zr with irradiation time;
s4, according to 133 Neutron radiation capturing reaction section meter for CsCalculate two kinds of abundance fuel balls 134 A change curve of the number and the activity of Cs atoms along with the irradiation time;
s5, establishing the two kinds of abundance fuel balls 134 A relationship between Cs activity and burnup depth;
s6, establishing 134 Activity of Cs, 95 Two-dimensional plot between Zr activities;
s7, adopting a high-purity germanium gamma spectrometer to measure the gamma energy spectrum of the fuel sphere on line to obtain 134 Cs、 95 Activity of Zr;
s8, according to 134 Activity of Cs, 95 Judging the abundance of the fuel sphere by using the Zr activity two-dimensional graph;
s9, checking the corresponding type according to the abundance type 134 The Cs activity-burnup relationship table yields the burnup depth.
Compared with the prior art, the embodiment of the application has at least the following advantages or beneficial effects:
1. for shorter cooling times (shorter than 10 days), the gamma ray energy spectrum of the fuel sphere contains contributions of shorter life nuclides with stronger interference around 661.6keV, resulting in 137 The activity of Cs is difficult to measure. The application is realized by 134 Activity of Cs and 95 Zr/ 103 ru activity ratio to determine fuel abundance, then by 134 The activity of Cs was calculated as burnup. Relative to 137 661.66keV of Cs, the application 134 The 795keV of Cs is located in a higher energy region, the background count is obviously lower, and no strong interference nuclides exist nearby, so that the accurate activity is easy to measure, and further the burnup is obtained.
2. Compared with the prior art 137 The activity-burn-up linear relationship of Cs, 134 the activity of Cs increases in an ultra-linear manner along with the deepening of burnup, and high-precision burnup data can be easily measured in a high burnup area, so that the method has realizability for measuring the burnup condition of the fuel element of the pebble-bed reactor.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an on-line monitoring layout of the burnup depth of an HTR-PM stack type fuel sphere in the prior art;
FIG. 2 is a neutron spectrum of the embodiment S1 under different core temperature conditions;
FIG. 3 is a plot of the rate of cracking, burn depth, and full power day for the 4.2% abundance fuel sphere of example S2;
FIG. 4 is a step S5 of the embodiment 95 Zr activity 134 Relationship curve of Cs activity;
FIG. 5 is a view showing the depth of burn-up in step S6 of the embodiment 134 Relationship curve of Cs activity.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The present application will be described in detail with reference to specific examples.
A method of measuring in-line the burnup depth of a fuel element of a pebble-bed reactor, comprising the steps of:
s1, modeling a pebble-bed reactor fuel element, and the distribution and boundary conditions in the reactor, and performing neutron transport Meng Ka simulation to obtain an in-reactor neutron energy spectrum phi and obtain an in-reactor average neutron fluence rate according to reactor power;
s2, calculating the contents of the two kinds of abundant fuel balls by utilizing neutron energy spectrum, average neutron fluence rate and fission section along with neutron energy change curve 235 U、 238 U、 239 Pu atomA change curve of the number and the burnup depth along with the irradiation time;
s3, combining the accumulated fission yield-neutron energy relation curve, and calculating the positions of the two abundance fuel spheres 133 Cs、 95 A change curve of atomic number and activity of Zr with irradiation time;
s4, according to 133 Calculation of neutron radiation capture reaction cross section of Cs in two kinds of abundance fuel balls 134 A change curve of the number and the activity of Cs atoms along with the irradiation time;
s5, establishing the two kinds of abundance fuel balls 134 A relationship between Cs activity and burnup depth;
s6, establishing 134 Activity of Cs, 95 Two-dimensional plot between Zr activities;
s7, adopting a high-purity germanium gamma spectrometer to measure the gamma energy spectrum of the fuel sphere on line to obtain 134 Cs、 95 The activity of Zr is subjected to decay correction to obtain the saturation activity in the reactor core;
s8, according to 134 Activity of Cs, 95 Judging the abundance of the fuel sphere by using the Zr activity two-dimensional graph;
s9, checking the corresponding type according to the abundance type 134 The Cs activity-burnup relationship table yields the burnup depth.
In some embodiments of the application, the two abundances are divided into 4.2% and 8.5%.
In some embodiments of the application, in the step S7 134 The activity of Cs is obtained from 795keV, which 95 The activity of Zr was obtained from 724keV and 757 keV.
The features and capabilities of the present application are described in further detail below in connection with the examples.
Examples
The embodiment provides a method for measuring the burnup depth of a fuel element of a pebble-bed reactor on line, which comprises the following steps:
s1, modeling the pebble-bed reactor fuel element, the reactor internal distribution, the boundary conditions and the reactor core temperature, carrying out neutron transport Meng Ka simulation to obtain an in-reactor neutron energy spectrum phi, and obtaining the in-reactor average neutron fluence rate according to the reactor power.
The method comprises the following steps: the fuel pellet has a composition of 7 g uranium and 254 g graphite, a filling rate of 0.61, a core diameter of 3 m and a length of 11 m, and an average density of 1.4 g/cm 3 . The core temperature was simulated from 700 ℃ to 1600 ℃ at 100 ℃ intervals to obtain 9 neutron energy spectra, see fig. 2. According to the obtained energy spectrum, an average fission section can be obtained by combining a fission section curve, the fission rate can be derived from the core thermal power and the contribution of single fission to heat production, and the average neutron fluence rate can be calculated by combining the number of U-235 atoms in the reactor and the average fission section. The energy spectrum of different core temperatures needs to be simulated because the temperature affects the distribution and proportion of low-energy components of the energy spectrum, has a larger influence on the nuclear reaction, in particular 134 And (3) generating Cs. Burnup at different temperatures 134 The Cs activity curves are also different. Simulation and calculation are required based on the core temperature at which the reactor is actually operated. The calculation related to the application is carried out according to neutron energy spectrum simulated under the condition of 1000 ℃.
S2, calculating the abundance (4.2% and 8.5%) of the two kinds of fuel balls by utilizing neutron energy spectrum, average neutron fluence rate and fission section along with neutron energy change curve 235 U、 238 U、 239 The change curve of Pu atomic number and burnup depth with irradiation time is shown in FIG. 3; 4.2% and 8.5% were chosen because these two abundances were used for fuel spheres used in the shandong stoneware bay nuclear power plant.
S3, calculating the two abundances (4.2% and 8.5%) in the fuel sphere by combining the cumulative fission yield-neutron energy relation curve 133 Cs、 95 A change curve of atomic number and activity of Zr with irradiation time;
s4, according to 133 Neutron radiation capture reaction cross section of Cs calculates the abundance (4.2% and 8.5%) within the fuel sphere of two species 134 A change curve of the number and the activity of Cs atoms along with the irradiation time;
s5, establishing two kinds of abundance (4.2% and 8.5%) fuel balls 134 Relation between activity of Cs and burnup depth 134 The relationship of Cs activity is shown in fig. 4;
s6, establishing 134 Cs、 95 A two-dimensional map of the Zr-s, 95 zr activity 134 The relation curve of Cs activity is shown in FIG. 5 and is used for judging the abundance type of the fuel sphere;
s7, adopting a high-purity germanium gamma spectrometer to measure the gamma energy spectrum of the fuel sphere on line, and obtaining the fuel sphere from 795keV 134 The activity of Cs is obtained from 724keV and 757keV 95 The activity of Zr and decay correction are carried out to obtain the saturation activity in the reactor core;
s8, according to 134 Cs、 95 Judging the abundance of fuel balls by a two-dimensional graph among Zr;
s9, according to 134 The Cs-burnup relationship is then used to obtain the burnup depth.
In summary, the method for online measuring the burnup depth of the fuel element of the pebble-bed reactor according to the embodiment of the application has the following advantages:
1. for shorter cooling times (shorter than 10 days), the gamma ray energy spectrum of the fuel sphere contains contributions of shorter life nuclides with stronger interference around 661.6keV, resulting in 137 The activity of Cs is difficult to measure. The application is realized by 134 Activity of Cs and 95 Zr/ 103 ru activity ratio to determine fuel abundance, then by 134 The activity of Cs was calculated as burnup. Relative to 137 661.66keV of Cs, the application 134 The 795keV of Cs is located in a higher energy region, the background count is obviously lower, and no strong interference nuclides exist nearby, so that the accurate activity is easy to measure, and further the burnup is obtained.
2. Compared with the prior art 137 The activity-burn-up linear relationship of Cs, 134 the activity of Cs increases in an ultra-linear manner along with the deepening of burnup, and high-precision burnup data can be easily measured in a high burnup area, so that the method has realizability for measuring the burnup condition of the fuel element of the pebble-bed reactor.
The embodiments described above are some, but not all embodiments of the application. The detailed description of the embodiments of the application is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Claims (3)
1. A method of measuring the burnup depth of a fuel element of a pebble-bed reactor on-line, comprising the steps of:
s1, modeling a pebble-bed reactor fuel element, and the distribution and boundary conditions in the reactor, and performing neutron transport Meng Ka simulation to obtain an in-reactor neutron energy spectrum phi and obtain an in-reactor average neutron fluence rate according to reactor power;
s2, calculating the contents of the two kinds of abundant fuel balls by utilizing neutron energy spectrum, average neutron fluence rate and fission section along with neutron energy change curve 235 U、 238 U、 239 The number of Pu atoms and the burning depth change curve along with the irradiation time;
s3, combining the accumulated fission yield-neutron energy relation curve, and calculating the positions of the two abundance fuel spheres 133 Cs、 95 A change curve of atomic number and activity of Zr with irradiation time;
s4, according to 133 Calculation of neutron radiation capture reaction cross section of Cs in two kinds of abundance fuel balls 134 A change curve of the number and the activity of Cs atoms along with the irradiation time;
s5, establishing the two kinds of abundance fuel balls 134 A relationship between Cs activity and burnup depth;
s6, establishing 134 Activity of Cs, 95 Two-dimensional plot between Zr activities;
s7, adopting a high-purity germanium gamma spectrometer to measure the gamma energy spectrum of the fuel sphere on line to obtain 134 Cs、 95 The activity of Zr is subjected to decay correction to obtain the saturation activity in the reactor core;
s8, according to 134 Activity of Cs, 95 Judging the abundance of the fuel sphere by using the Zr activity two-dimensional graph;
s9, checking the corresponding type according to the abundance type 134 The Cs activity-burnup relationship table yields the burnup depth.
2. The method of on-line measuring the burnup depth of a pebble bed reactor fuel element of claim 1 wherein said two abundances are divided into 4.2% and 8.5%.
3. The method for in-line measuring the burnup depth of a fuel element of a pebble bed reactor as recited in claim 1, wherein in said step S7 134 The activity of Cs is obtained from 795keV, which 95 The activity of Zr was obtained from 724keV and 757 keV.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311145257.1A CN116994785A (en) | 2023-09-06 | 2023-09-06 | Method for measuring burnup depth of fuel element of pebble-bed reactor on line |
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| CN202311145257.1A CN116994785A (en) | 2023-09-06 | 2023-09-06 | Method for measuring burnup depth of fuel element of pebble-bed reactor on line |
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| CN202311145257.1A Pending CN116994785A (en) | 2023-09-06 | 2023-09-06 | Method for measuring burnup depth of fuel element of pebble-bed reactor on line |
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