CN114093536A - Measuring method for monitoring leakage of steam generator of nuclear power plant - Google Patents
Measuring method for monitoring leakage of steam generator of nuclear power plant Download PDFInfo
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- CN114093536A CN114093536A CN202111222724.7A CN202111222724A CN114093536A CN 114093536 A CN114093536 A CN 114093536A CN 202111222724 A CN202111222724 A CN 202111222724A CN 114093536 A CN114093536 A CN 114093536A
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- 238000000034 method Methods 0.000 title claims abstract description 32
- 238000012544 monitoring process Methods 0.000 title claims abstract description 14
- 230000000694 effects Effects 0.000 claims abstract description 22
- YZCKVEUIGOORGS-NJFSPNSNSA-N Tritium Chemical compound [3H] YZCKVEUIGOORGS-NJFSPNSNSA-N 0.000 claims abstract description 18
- 229910052722 tritium Inorganic materials 0.000 claims abstract description 18
- 239000010865 sewage Substances 0.000 claims abstract description 8
- 239000000523 sample Substances 0.000 claims description 60
- 238000001514 detection method Methods 0.000 claims description 31
- 238000005259 measurement Methods 0.000 claims description 25
- FVAUCKIRQBBSSJ-UHFFFAOYSA-M sodium iodide Chemical compound [Na+].[I-] FVAUCKIRQBBSSJ-UHFFFAOYSA-M 0.000 claims description 24
- 239000007788 liquid Substances 0.000 claims description 18
- 239000012496 blank sample Substances 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 235000009518 sodium iodide Nutrition 0.000 claims description 8
- 238000011084 recovery Methods 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 241001125831 Istiophoridae Species 0.000 claims description 2
- 239000013589 supplement Substances 0.000 abstract description 3
- 239000000941 radioactive substance Substances 0.000 abstract description 2
- 230000002285 radioactive effect Effects 0.000 abstract 1
- 239000000956 alloy Substances 0.000 description 1
- 238000009614 chemical analysis method Methods 0.000 description 1
- 230000004992 fission Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
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Classifications
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C17/00—Monitoring; Testing ; Maintaining
- G21C17/002—Detection of leaks
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C17/00—Monitoring; Testing ; Maintaining
- G21C17/003—Remote inspection of vessels, e.g. pressure vessels
-
- 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
- G21C17/104—Measuring reactivity
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Measurement Of Radiation (AREA)
Abstract
The invention belongs to the field of nuclear power plant chemistry, and particularly relates to a measuring method for monitoring leakage of a steam generator of a nuclear power plant. Because of the huge pressure difference existing on the two sides of the first loop and the second loop of the nuclear power plant, radioactive substances in the first loop can be quickly diffused into the second loop and are brought to a steam turbine plant by steam, and radioactive leakage accidents occur, so that whether leakage of a steam generator to a certain degree exists or not is monitored regularly, and the nuclear power plant is important work. The method can be used for accurately and regularly monitoring whether the steam generator of the nuclear power plant leaks, is stable and reliable, is simple, and can be popularized and used subsequently. The method mainly comprises the following steps: the method comprises the following steps: measuring the total gamma of the sewage discharged by the steam generator; step two: the VVP tritium specific activity of the main steam circuit was measured. The leakage condition of the steam generator can be effectively monitored by using the method, and the leakage condition can be used as a supplement for verifying the accuracy of the KRT measuring channel signal in the steam generator.
Description
Technical Field
The invention belongs to the field of nuclear power plant chemistry, and particularly relates to a measuring method for monitoring leakage of a steam generator of a nuclear power plant.
Background
Steam generators are the primary equipment connecting the primary and secondary circuits of a nuclear power plant and play a very important role in the nuclear power plant as the pressure boundary of the primary circuit. Because steam generator inner structure is complicated, easily receive all kinds of impurity striking, corruption, pH etc. to influence and cause the leakage of certain degree, and in case steam generator tube sheet and heat transfer tube bank break, because the huge pressure differential that exists in one, two return circuits both sides, the radioactive substance of one loop can spread fast in two return circuits and is taken the steam turbine factory building by steam, takes place the radioactivity leakage accident, therefore whether regular monitoring steam generator has the leakage of certain degree is an important work of nuclear power plant.
This patent can cause the total gamma of steam generator blowdown water and the characteristic that main steam loop VVP tritium specific activity increases after leaking according to steam generator, adopts corresponding chemical analysis method to carry out periodic monitoring to it, can monitor steam generator's leakage situation effectively and as the replenishment of verifying nuclear power plant steam generator radioactivity detecting system (KRT) measurement channel signal accuracy. The invention relates to the field of nuclear power plant chemistry, whether a Steam Generator (SG) of a nuclear power plant leaks can be accurately and regularly monitored by using the method, and the method is stable and reliable, simple and can be popularized and used subsequently according to the principle of the method and the measurement result carried out during the normal operation period of a unit No. 1 of a Fangjiashan.
Disclosure of Invention
1. The purpose is as follows:
the invention aims to provide a novel combined measuring mode for regularly monitoring the leakage condition of a steam generator of a nuclear power plant, and the leakage condition of the steam generator can be effectively monitored by using the method and can be used as a supplement for verifying the accuracy of a KRT measuring channel signal in the steam generator.
2. The technical scheme is as follows:
a measurement method for monitoring leakage of a steam generator of a nuclear power plant comprises the following steps: the method comprises the following steps: measuring the total gamma of the sewage discharged by the steam generator; step two: the VVP tritium specific activity of the main steam circuit was measured.
The first step is as follows: the method for measuring the total gamma of the sewage discharged by the steam generator specifically comprises the following steps: (1) measuring a detection limit; (2) measuring an actual sample; (3) the values were compared.
The second step is that: measuring VVP tritium specific activity of the main steam loop, and specifically comprising: (1) measuring a detection limit; (2) measuring an actual sample; (3) and (6) analyzing the trend.
The measuring of the detection limit in the first step specifically includes: the efficiency of the probe of the sodium iodide gamma spectrometer is measured by a standard source, 1L of desalted water is placed in a Marlin cup and placed in the sodium iodide gamma spectrometer, the average blank value is obtained by measuring for 3 times, and the numerical values are substituted into a formula 1:
wherein: k: confidence coefficient (1.645, 95% confidence)
nb: blank sample count rate
T: time for measuring sample to be measured and blank sample
Epsilon: sample recovery
E: efficiency of detection
V: sample volume
The measuring of the actual sample in the first step specifically comprises: the activity concentration of the sample is obtained by conversion in formula 2:
a: activity concentration of sample
ns: sample measurement
nb: background measurement
E: efficiency of the instrument
V: sample volume
The comparison numerical value in the first step specifically comprises the following steps: comparing the activity concentration A of the sample with the detection line LLD, if A is less than or equal to LLD, the steam generator has no leakage.
The measuring of the detection limit in the second step specifically comprises: the efficiency of the liquid flash analyzer probe is measured through a standard source, a 10ml desalted water sample and 10ml scintillation liquid are placed in a liquid flash bottle and placed in the liquid flash analyzer, an average blank value is obtained by measuring for 3 times, and then the numerical value is brought into a formula 3 of a detection limit to be converted to obtain a detection limit value:
wherein: k: confidence coefficient (1.645, 95% confidence)
nb: blank sample count rate (cps)
T: time for measuring sample to be measured and blank sample
Epsilon: sample recovery
E: efficiency of detection
V: sample volume
The comparison numerical value in the second step specifically comprises the following steps:
a: activity concentration of sample
ns: sample measurement
nb: background measurement
E: efficiency of the instrument
V: sample volume
Analyzing the trend in the second step specifically comprises the following steps: and analyzing whether the tritium content in the VVP system for operation of the nuclear power plant is lower than 0.4MBq/t specified by the power plant or not, and analyzing the operation condition of a heat transfer pipe of a steam generator.
3. The effect is as follows:
the invention can effectively monitor the leakage condition of the steam generator and can be used as supplement for verifying the accuracy of the signal of the measurement channel of the SG radioactivity detection system (KRT) by measuring the total gamma of the discharged water of the steam generator and the VVP tritium specific activity of the main steam loop.
Drawings
FIG. 1 trend graph of tritium content of VVP system
Detailed Description
Periodically monitoring the total gamma of the sewage discharged by the steam generator and the VVP tritium specific activity of the main steam loop:
the measuring working condition and period of the total gamma of the discharged water of the steam generator are as follows: adopting an ORTEC sodium iodide gamma spectrometer model 905-4, measuring voltage 800v and measuring time 1000 s; and (3) period: once a month.
Measuring working conditions and periods of VVP tritium of the main steam loop are as follows: a PE company liquid flash analyzer 3180TR is adopted; and (3) period: once per week.
The specific implementation mode is as follows:
firstly, measuring the total gamma of the sewage discharged by the steam generator:
measurement of detection limit:
the efficiency of the probe of the sodium iodide gamma spectrometer is measured to be 11.4% through a standard source, 1L of demineralized water is placed in a Marin cup and placed in the sodium iodide gamma spectrometer, the average blank value is 3.86cps after 3 times of measurement, and then the value is brought into a general formula of a detection limit to be converted to obtain the detection limit value.
K: confidence coefficient (1.645, 95% confidence)
nb: blank sample count rate
T: time for measuring sample to be measured and blank sample
Epsilon: sample recovery
E: efficiency of detection
V: sample volume
The results obtained were: the detection limit of the NaI measuring instrument is as follows: 3.15Bq/L
(II) measurement of actual samples:
the activity concentration of the sample is obtained by conversion in the following formula:
a: activity concentration of sample
ns: sample measurement
nb: background measurement
E: efficiency of the instrument
V: sample volume
The regular measurement (once per month) of the total gamma of the sewage discharged by the 1SG1 after the machine No. 1 of the square jiashan 104 is overhauled regularly obtains that all the past results are less than the detection limit value of the instrument by 3.15Bq/L, and proves that the steam generator No. 1 of the square jiashan has no leakage and has good integrity.
Secondly, VVP tritium specific activity of the main steam loop:
measurement of detection limit:
the efficiency of the probe of the liquid flash analyzer is measured to be 21.3% through a standard source, 10ml of desalted water sample and 10ml of scintillation liquid are placed in a liquid flash bottle and placed in the liquid flash analyzer, the average blank value of 0.083cps is obtained after 3 times of measurement, and then the value is brought into a general formula of a detection limit to be converted to obtain the detection limit value of the liquid flash analyzer.
K: confidence coefficient (1.645, 95% confidence)
nb: blank sample count rate (cps)
T: time for measuring sample to be measured and blank sample
Epsilon: sample recovery
E: efficiency of detection
V: sample volume
The results obtained were: the limit of detection of tritium by the liquid scintillation counter is: 10.5 Bq/L.
(II) measurement of actual samples:
the activity and concentration of the sample are obtained by conversion in the following formula
A: activity concentration of sample
ns: sample measurement
nb: background measurement
E: efficiency of the instrument
V: sample volume
The method is characterized in that a background sample (10ml of desalted water and 10ml of scintillation liquid) and a measurement sample (10ml of scintillation liquid and 10ml of sample) are placed into a liquid scintillation counter to obtain a result DPM, the DPM is divided by 60 and 0.01L to obtain a measurement result, the measurement result is shown in figure 1, the trend graph of the tritium content of the Qin mountain nuclear power generation unit No. 1 in normal operation within 23 weeks after overhaul is shown, it can be seen from the graph that the tritium content in a VVP system is accumulated to a certain extent from the first lower than a detection line to the later stage along with the operation of a nuclear power plant, but the content value is far lower than 0.4MBq/t specified by the power plant, because an alloy material used by a steam generator has good penetration resistance to a ternary fission tritium heat transfer pipe, but has certain permeability, and if the water quality of a secondary loop is updated or the emission amount of small tritium concentration can generate a certain degree of rising phenomenon, so that the steam generator can operate perfectly, there is substantially no leakage of nuclear power plants from the primary circuit to the secondary circuit through the steam generator.
Claims (9)
1. A measuring method for monitoring leakage of a steam generator of a nuclear power plant is characterized by comprising the following steps: the method comprises the following steps: the method comprises the following steps: measuring the total gamma of the sewage discharged by the steam generator; step two: the VVP tritium specific activity of the main steam circuit was measured.
2. The method of claim 1, wherein the method comprises the steps of: the first step is as follows: the method for measuring the total gamma of the sewage discharged by the steam generator specifically comprises the following steps: (1) measuring a detection limit; (2) measuring an actual sample; (3) the values were compared.
3. The method of claim 1, wherein the method comprises the steps of: the second step is that: measuring VVP tritium specific activity of the main steam loop, and specifically comprising: (1) measuring a detection limit; (2) measuring an actual sample; (3) and (6) analyzing the trend.
4. The method of claim 2, wherein the method comprises the steps of: the measuring of the detection limit in the first step specifically includes: the efficiency of the probe of the sodium iodide gamma spectrometer is measured by a standard source, 1L of desalted water is placed in a Marlin cup and placed in the sodium iodide gamma spectrometer, the average blank value is obtained by measuring for 3 times, and the numerical values are substituted into a formula 1:
wherein: k: confidence coefficient (1.645, 95% confidence)
nb: blank sample count rate
T: time for measuring sample to be measured and blank sample
Epsilon: sample recovery
E: efficiency of detection
V: sample volume.
5. The method of claim 2, wherein the method comprises the steps of: the measuring of the actual sample in the first step specifically comprises: the activity concentration of the sample is obtained by conversion in formula 2:
a: activity concentration of sample
ns: sample measurement
nb: background measurement
E: efficiency of the instrument
V: sample volume.
6. The method of claim 2, wherein the method comprises the steps of: the comparison numerical value in the first step specifically comprises the following steps: comparing the activity concentration A of the sample with the detection line LLD, if A is less than or equal to LLD, the steam generator has no leakage.
7. A method of measuring leakage monitoring of a steam generator of a nuclear power plant according to claim 3, characterized in that: the measuring of the detection limit in the second step specifically comprises: the efficiency of the liquid flash analyzer probe is measured through a standard source, a 10ml desalted water sample and 10ml scintillation liquid are placed in a liquid flash bottle and placed in the liquid flash analyzer, an average blank value is obtained by measuring for 3 times, and then the numerical value is brought into a formula 3 of a detection limit to be converted to obtain a detection limit value:
wherein: k: confidence coefficient (1.645, 95% confidence)
nb: blank sample count rate (cps)
T: time for measuring sample to be measured and blank sample
Epsilon: sample recovery
E: efficiency of detection
V: sample volume.
8. A method of measuring leakage monitoring of a steam generator of a nuclear power plant according to claim 3, characterized in that: the comparison numerical value in the second step specifically comprises the following steps:
a: activity concentration of sample
ns: sample measurement
nb: background measurement
E: efficiency of the instrument
V: sample volume.
9. A method of measuring leakage monitoring of a steam generator of a nuclear power plant according to claim 3, characterized in that: analyzing the trend in the second step specifically comprises the following steps: and analyzing whether the tritium content in the VVP system for operation of the nuclear power plant is lower than 0.4MBq/t specified by the power plant or not, and analyzing the operation condition of a heat transfer pipe of a steam generator.
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