Method for testing release rate of tritium in tritium-containing waste

Abstract

The invention relates to a method for testing the tritium release rate of a tritium-containing waste package, and the method comprises the steps: guiding tritium-containing waste gas released by the tritium-containing waste package in an exhaust hood to be continuously input into an ionization chamber online monitoring system, and determining the initial tritium activity concentration; when the first threshold value is lower than the first threshold value, the tritium-containing waste gas flows into an initial bubbling sampler after passing through a refrigerating system to collect tritiated water, and target gas is obtained; enabling the target gas to circularly pass through the operation of the initial bubbling sampler, and replacing a new bubbling sampler every time a first preset time is reached; after a second preset time is reached, stopping the cyclic operation, and testing the target tritium activity concentration of liquid in the bubbling sampler which is replaced for multiple times and the current bubbling sampler by adopting a liquid scintillation counter; and calculating the tritium release rate based on the target tritium activity concentration. Target gas is discharged into the exhaust hood again, tritiated water absorption is carried out on tritium-containing waste gas multiple times, and the technical effects that tritiated water absorption is more complete due to multiple times of cyclic absorption, and the tritium release rate detection result is more accurate are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tritium release rate testing, and particularly relates to a testing method for tritium release rate of a tritium-containing waste package. BACKGROUND

[0002] The tritium-containing waste package with cement as a solidification medium is an important low and intermediate level waste package to be disposed in China, and the tritium release rate thereof is a key index for evaluating the total amount of tritium released to the environment by the tritium-containing waste package during storage. Meanwhile, the accumulation of data on the total tritium activity of the tritium-containing waste and the tritium release rate of the waste package after being put into a barrel and the gradual understanding of the relationship between the two can provide a basis for the safe storage, disposal and management of the tritium-containing waste package.

[0003] In the related art, the tritiated water in the tritium-containing gas is absorbed by a bubble sampler, and then the tritium activity concentration is measured by a liquid scintillation counter, so as to measure the tritium release rate of the tritium-containing waste package.

[0004] However, the sampling efficiency of the bubble sampler is affected by multiple factors such as gas flow rate and tritium content in the gas, and the absorption of tritium elements cannot reach 100%, and in the related art, part of the tritium-containing waste gas that is not absorbed by the bubble sampler is discharged into the exhaust system, which leads to the inaccuracy of the tritium release rate test result of the tritium-containing waste package.

[0005] The above problems need to be solved. SUMMARY

[0006] The present application discloses a testing method for tritium release rate of a tritium-containing waste package, and aims to solve the technical problems in the prior art.

[0007] The present application adopts the following technical scheme: The application provides a method for testing tritium release rate of tritium-containing waste package, comprising: S1. Ionization chamber preliminary monitoring: guiding the tritium-containing waste gas released by the tritium-containing waste package in the exhaust hood to flow through the mass flow meter, and then continuously inputting into the ionization chamber online monitoring system to determine the initial tritium activity concentration in the tritium-containing waste gas; S2. Bubble generator sampling: when the initial tritium activity concentration is lower than a first threshold value, guiding the tritium-containing waste gas in the ionization chamber online monitoring system to flow through the refrigeration system and then enter the initial bubble sampling device to collect tritiated water in the tritium-containing waste gas, so as to obtain target gas, wherein the tritiated water is a compound containing tritium element, and part of the tritiated water remains in the initial bubble sampling device; S3. Replacing bubble sampling device: guiding the target gas to be discharged into the exhaust hood, and then flowing through the mass flow meter and then entering the ionization chamber online monitoring system again, and the steps S1 and S2 are cyclically operated; during the cyclic operation of the steps S1 and S2, the initial bubble sampling device is taken out and replaced with a new bubble sampling device every time a first predetermined time is reached; S4. Liquid scintillation counter test: after a second predetermined time is reached, the cyclic operation of the steps S1 and S2 is stopped, and the liquid in the bubble sampling device taken out for multiple times and the currently used bubble sampling device is tested for target tritium activity concentration by using a liquid scintillation counter; and the tritium release rate is calculated based on the target tritium activity concentration.

[0008] Optionally, the step S2 comprises: guiding the tritium-containing waste gas in the ionization chamber online monitoring system to flow through the first refrigeration system and then flow into the first initial bubble sampling device to collect tritium elements in the form of tritiated water in the tritium-containing waste gas, so as to obtain first gas; inputting the first gas into a catalytic bed, and catalytically converting tritium-containing small-molecule organic matters and hydrogen tritium in the first gas into the form of tritiated water, so as to obtain second gas; and guiding the second gas to flow through the second refrigeration system and then flow into the second initial bubble sampling device to collect tritium elements in the form of tritiated water in the second gas, so as to obtain target gas.

[0009] Optionally, the first initial bubble sampling device and the second initial bubble sampling device are both second-level bubble sampling devices; the volume of the sampling liquid in the initial bubble sampling device is 100-500 mL; the sampling liquid in the initial bubble sampling device includes but is not limited to water or ethylene glycol; and the first predetermined time range for replacing the initial bubble sampling device is 3-9 days.

[0010] Optionally, the method further comprises: in the step S1, when the initial tritium activity concentration is higher than or equal to the first threshold value, confirming that the initial tritium activity concentration measured by the ionization chamber online monitoring system is a target activity concentration; and determining the tritium release rate based on the target tritium activity concentration; wherein the tritium-containing waste gas is ionized in the ionization chamber online monitoring system to form an electric current, and the ionization chamber online monitoring system determines the initial tritium activity concentration in the tritium-containing waste gas based on the electric current.

[0011] Optionally, after step S4, the method further comprises: using compressed air to purge the exhaust hood at a predetermined flow rate, so that residual tritium-containing exhaust gas flows through the ionization chamber online monitoring system and the replaced bubble sampler in turn, and is discharged into the exhaust system.

[0012] Optionally, the predetermined flow rate of the compressed air is 500 mL / min to 5 L / min; and the purging time of the compressed air is 3 h to 12 h.

[0013] Optionally, the exhaust hood needs to meet the requirement of a leakage rate of less than 2.5 × 10 -3 h -1 .

[0014] Optionally, the first threshold range of the tritium activity concentration is 400 Bq / L to 4000 Bq / L.

[0015] Optionally, the flow rate range of the initial tritium-containing exhaust gas through the mass flow meter is 200 mL / min to 2 L / min.

[0016] Optionally, the second predetermined time is 1 to 12 months.

[0017] The technical solution adopted by the present application can achieve at least one of the following beneficial effects: In the embodiment of the present application, the tritium-containing exhaust gas released by the tritium-containing waste package in the exhaust hood is guided to continuously flow into the ionization chamber online monitoring system after flowing through the mass flow meter, so as to determine the initial tritium activity concentration in the tritium-containing exhaust gas; when the initial tritium activity concentration is lower than a first threshold value, the tritium-containing exhaust gas is guided to flow into the initial bubble sampler after flowing through the refrigeration system, so as to collect tritiated water in the tritium-containing exhaust gas, and obtain target gas, wherein the tritiated water is a compound containing tritium element, and part of the tritiated water remains in the initial bubble sampler; the target gas is guided to be discharged into the exhaust hood, and then flows through the mass flow meter again, and then enters the ionization chamber online monitoring system again, and the above operation is repeated, and the initial bubble sampler is replaced with a new bubble sampler every time the first predetermined time is reached; after the second predetermined time is reached, the liquid in the bubble samplers replaced multiple times and the currently used bubble sampler is tested for target tritium activity concentration by using a liquid scintillation counter; and the tritium release rate is calculated based on the target tritium activity concentration. The target gas is discharged into the exhaust hood again, and the operation of circulating through the bubble sampler is achieved, and the purpose of repeatedly absorbing the tritium element in the tritium-containing exhaust gas in the form of tritiated water is achieved, so that the tritiated water is close to complete absorption, and the technical effect of more accurate detection results is achieved, thereby solving the technical problem that the tritium release rate test result of the tritium-containing waste package is inaccurate because the tritium-containing exhaust gas not absorbed by the bubble sampler is discharged into the atmosphere. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows, which form a part of the present application. The illustrative embodiments of the present application and the description and explanation thereof do not constitute an improper limitation on the present application. In the drawings: Figure 1 is a flow chart of a testing method for tritium release rate of a tritium-containing waste package according to the present application; Figure 2 is a process flow chart of a device for a testing method for tritium release rate of a tritium-containing waste package according to the present application; Figure 3 is a flow chart of tritiated water absorption in a testing method for tritium release rate of a tritium-containing waste package according to the present application. DETAILED DESCRIPTION

[0019] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely in combination with specific embodiments of the present application and corresponding drawings. In the description of the present application, it should be noted that the term "or" is generally used in the sense of including "and / or" unless the context clearly indicates otherwise.

[0020] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection, can also be magnetic connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In addition, in the description of the present application, the terms "first", "second" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance. In the description of the present application, the meaning of "multiple" is at least two, for example, two, three or more, etc., unless otherwise explicitly specified and limited.

[0021] Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts fall within the scope of protection of the present application.

[0022] First, in order to facilitate the understanding of the embodiments of the present application, the following will explain and describe some terms or nouns involved in the present application: Tritium (³H) is a radioactive isotope of hydrogen, with an atomic nucleus containing one proton and two neutrons. It is a colorless, odorless gas with a density slightly higher than air (about 0.0899 kg / m³), a melting point of -259.14°C, and a boiling point of -252.87°C. It is not soluble in water, but can be combined with water through chemical reactions to form tritiated water (HTO).

[0023] The tritium release rate of a tritium-containing waste package refers to the amount of tritium released from the waste package into the environment per unit time, usually expressed in units of activity (Becquerel, Bq) or Curie (Ci).

[0024] To solve the problems in the prior art, the embodiments of the present application provide a test method for the tritium release rate of a tritium-containing waste package.

[0025] The embodiments provide a test method for the tritium release rate of a tritium-containing waste package, as shown in Figure 1 and Figure 2 , Figure 1 is a flowchart of a test method for the tritium release rate of a tritium-containing waste package, Figure 2 is a device process flowchart of a test method for the tritium release rate of a tritium-containing waste package, which comprises: Step S1, initial monitoring of ionization chamber: the tritium-containing waste gas released by the tritium-containing waste package in the exhaust hood is continuously input to the ionization chamber online monitoring system after passing through the mass flow meter, and the initial tritium activity concentration in the tritium-containing waste gas is determined; Optionally, the tritium-containing waste package is placed in the exhaust hood, and the gas in the exhaust hood is pumped out by a diaphragm pump. Then, the tritium-containing gas pumped out of the exhaust hood flows into a filter to filter aerosols carried in the tritium-containing waste gas. The tritium-containing waste gas passing through the filter flows through the mass flow meter to control the flow rate of the gas entering the subsequent measurement system. Then, the tritium-containing waste gas passes through the ionization chamber online monitoring system at a certain flow rate. The ionization chamber online monitoring system can automatically obtain the initial tritium activity concentration in the tritium-containing waste gas. The working principle of the ionization chamber online monitoring system is that radiation passes through the tritium-containing waste gas, ionizes the gas molecules, and generates positive and negative charge pairs. Under the action of the electric field in the ionization chamber, the positive and negative charge pairs move towards the electrodes to form an electric current. By measuring the size of the current signal, the initial tritium activity concentration is measured.

[0026] Optionally, the exhaust hood wraps the tritium-containing waste package, so that the tritium-containing waste gas released from the tritium-containing waste package can only be discharged into the exhaust hood and cannot be directly discharged into the exhaust system, ensuring that all tritium elements in the tritium-containing waste gas can enter the ionization chamber online monitoring system, effectively improving the accuracy of detection.

[0027] Optionally, due to the difference between the environment in the exhaust hood and the actual environment, and the need to change the environmental state value test disposal temperature environment, the actual environment also needs to be simulated under the disposal environment, and the temperature and humidity in the exhaust hood need to be adjusted to ensure that the tritium release rate of the tritium-containing waste package under the simulated test disposal environment temperature (minimum -35℃) is ensured. A circulating constant temperature system is added to the inner surface of the exhaust hood to simulate and analyze the tritium release rate of the tritium-containing waste package under different temperature conditions.

[0028] Optionally, the circulating constant temperature system adopts a secondary heat exchange mode to regulate the gas temperature in the exhaust hood. The circulating constant temperature system can be integrated with the exhaust hood in the form of a jacket, or it can be used as a heat preservation cavity, forming two independent systems with the exhaust hood. The circulating constant temperature system can heat or cool the gas in the exhaust hood.

[0029] Optionally, the circulating constant temperature system includes a temperature and humidity sensor and a pressure sensor for real-time monitoring of the temperature, humidity and pressure in the exhaust hood. The circulating constant temperature system also includes a temperature control assembly, which includes a heating resistance wire and a nitrogen cooling device, respectively used for heating or cooling the tritium-containing exhaust gas in the exhaust hood.

[0030] In some preferred embodiments, the flow rate of the tritium-containing exhaust gas through the mass flow meter is in the range of 200 mL / min to 2 L / min.

[0031] Optionally, the tritium-containing exhaust gas is introduced into the ionization chamber online monitoring system at a relatively fast rate, which may result in inaccurate data of the initial tritium activity concentration detected by the ionization chamber online monitoring system. Therefore, it is necessary to control the flow rate of the tritium-containing exhaust gas.

[0032] Optionally, in the case of slow flow rate of the tritium-containing exhaust gas, the entire experiment takes a long time, increasing the test cost. Therefore, it is necessary to control the flow rate of the tritium-containing exhaust gas in the range of 200 mL / min to 2 L / min.

[0033] In some preferred embodiments, the sealing property of the exhaust hood needs to meet the requirement that the hourly leakage rate is less than 2.5 × 10 -3 h -1 .

[0034] Optionally, the exhaust hood is in the form of a cylinder, and the structure is in the form of an upper cover and a lower barrel (the cover is above the barrel), or in the form of an upper barrel and a lower cover (the barrel is above the cover). By separating the barrel and the cover, the tritium-containing waste package can be taken out. The cover and the barrel are connected by bolts and are sealed to prevent tritium-containing exhaust gas from overflowing out of the exhaust hood.

[0035] Optionally, in order to ensure the sealing of the exhaust hood and the safety of the workers, avoid the leakage of tritium-containing exhaust gas leading to the danger of radioactive tritium elements to the workers, the sealing of the exhaust hood needs to be ensured to be at least 2.5 × 10 -3 h -1 .

[0036] Step S2, bubble sampler sampling: when the initial tritium activity concentration is lower than the first threshold value, the tritium-containing exhaust gas in the ionization chamber online monitoring system is guided to enter the initial bubble sampler after the refrigeration system, the tritium-containing exhaust gas is collected, and the target gas is obtained, wherein the tritium-containing water is a compound containing tritium elements, and part of the tritium-containing water remains in the initial bubble sampler; Optionally, the bubble sampler is suitable for the case where the initial tritium activity concentration is low, and the bubble sampler is more accurate in detection, but the sampling liquid in the bubble sampler can only absorb a certain amount of tritium-containing water each time, wherein the tritium-containing water (HTO, DTO, T2O) is a compound containing tritium elements. In the case that the sampling liquid reaches the saturation state, it can no longer absorb tritium elements, at which time the bubble sampler needs to be replaced, if the concentration is too high, the sampling liquid in the bubble sampler will soon reach saturation, the replacement frequency will be too high, the cost will increase, and it may cause the leakage of tritium-containing exhaust gas during the replacement process, which forms a certain hidden danger to the safety of the operators. Therefore, only in the case that the initial tritium activity concentration is lower than the first threshold value, and the replacement frequency of the bubble sampler is low, the method of using the bubble sampler and the liquid scintillation spectrometer is used for measurement.

[0037] Optionally, the bubble sampler is used for absorbing tritium-containing exhaust gas, when the tritium-containing exhaust gas flows through the initial bubble sampler, the tritium-containing water in the tritium-containing exhaust gas will dissolve in the sampling liquid of the initial bubble sampler, and the target gas discharged from the initial bubble sampler does not contain or contains a small amount of unabsorbed tritium elements.

[0038] In some preferred embodiments, the first threshold value range of the initial tritium activity concentration is 400 Bq / L to 4000 Bq / L.

[0039] Optionally, the tritium release rate test of the tritium-containing waste package is carried out according to the full tritium sampling and liquid scintillation spectrometer measurement method specified in GB 41930, if the tritium release rate of the tritium-containing waste package is large, the replacement frequency of the sampling liquid in the bubble sampler is fast, so the initial tritium activity concentration needs to be lower than the first threshold value range to use the bubble sampler for measurement, and the first threshold value range can be any threshold value in the range of 400 Bq / L to 4000 Bq / L.

[0040] In some preferred embodiments, as shown in Figure 3 , the initial tritium activity concentration is lower than the first threshold value range, and the bubble sampler is used for measurement. Figure 3The flowchart is a testing method for tritium release rate of tritium-containing waste package, and step S2 includes: the tritiated water in the tritium-containing waste gas is collected by the first initial bubble sampler after the tritium-containing waste gas flows into the first initial bubble sampler after passing through the first refrigeration system, and first gas is obtained; the first gas is input into the catalytic bed, and the tritium-containing small-molecule organic matter and hydrogen tritium in the first gas are catalytically converted into the form of tritiated water, and second gas is obtained; the tritiated water in the second gas is collected by the second initial bubble sampler after the second gas flows into the second initial bubble sampler after passing through the second refrigeration system, and target gas is obtained.

[0041] Optionally, when the initial tritium activity concentration is lower than the first threshold value, the closed loop test method of the catalytic bubble sampler and the liquid scintillation spectrometer is used to measure the tritium release rate of the tritium-containing waste package. That is, when the initial tritium activity concentration in the gas flowing through the ionization chamber online monitoring system is lower than the first threshold value, the gas is cooled to a certain temperature by the electromagnetic valve control after passing through the first refrigeration system, and then flows into the first initial bubble sampler to collect the tritiated water. The first gas flowing out of the first initial bubble sampler enters the catalytic bed to catalytically convert the tritium-containing small-molecule organic matter or hydrogen tritium into tritiated water, and then flows into the second initial bubble sampler for collection. The subsequent target gas returns to the exhaust hood.

[0042] Optionally, the tritiated water is more likely to condense into water in a low-temperature state, so that more tritiated water can be left in the first initial bubble sampler, thereby making the detection result more accurate.

[0043] Optionally, there may also be tritium-containing small-molecule organic matter or hydrogen tritium in the tritium-containing waste gas. The tritium-containing small-molecule organic matter or hydrogen tritium cannot be directly absorbed by the first initial bubble sampler, so the catalytic bed is used to catalytically convert the tritium-containing small-molecule organic matter or hydrogen tritium in the tritium-containing waste gas into the form of tritiated water, and then the second cooler and the second initial bubble sampler are used to absorb the tritiated water in the tritium-containing waste gas.

[0044] Optionally, the tritium element in the tritiated water is absorbed by the first initial bubble sampler, and the tritium element in the tritium-containing small-molecule organic matter or hydrogen tritium is absorbed by the second bubble sampler. At this time, the tritium elements in various forms in the tritium-containing waste gas have been absorbed, effectively improving the accuracy of the tritium release rate in the tritium-containing waste gas.

[0045] Optionally, a catalyst for converting tritium gas into tritiated water is placed in the catalytic bed, and the catalyst can be platinum or silver.

[0046] In some preferred embodiments, the first initial bubble sampler and the second initial bubble sampler are both second-level bubble samplers; the volume of the sampling liquid in the initial bubble sampler is 100-500 mL; the sampling liquid in the initial bubble sampler includes but is not limited to water or ethylene glycol; and the first predetermined time range for replacing the initial bubble sampler is 3-9 days.

[0047] Optionally, there are two sampling bottles in the secondary bubble sampler, and the tritiated water is collected multiple times to ensure more complete absorption of tritium elements. Tritiated water can be dissolved in water or ethylene glycol, and water solution or ethylene glycol solution can be placed in the secondary bubble sampler. It should be noted that the solution in the first stage and the second stage of the secondary bubble sampler needs to be consistent, and the absorption process of the secondary bubble sampler is stopped, and the liquid in the multiple replacement bubble samplers is measured by the liquid scintillation counter to measure the collected target tritium activity concentration.

[0048] Optionally, if the sampling liquid in the initial bubble sampler reaches the top of the bubble sampler, it may cause the sampling liquid to overflow after the tritium-containing waste gas is introduced. However, if the sampling liquid is less, it may cause the sampling liquid to quickly reach a saturated state, so the volume of the sampling liquid needs to be set at two-thirds of the initial bubble sampler, that is, the volume of the sampling liquid is 100-500 mL.

[0049] Step S3, replace the bubble sampler: guide the target gas into the exhaust hood, flow through the mass flow meter, and then enter the ionization chamber online monitoring system again, and operate steps S1 and S2 in a cycle; during the cycle operation of steps S1 and S2, the initial bubble sampler is removed and replaced with a new bubble sampler every time the first predetermined time is reached; Optionally, the sampling liquid in the initial bubble sampler will reach a saturated state as the tritium-containing waste gas is introduced, and the saturated bubble sampler needs to be replaced, that is, a bubble sampler containing sampling liquid that has not absorbed tritiated water is replaced. Because the initial tritium activity concentration in the tritium-containing waste gas is low, the initial bubble sampler reaches a saturated state in about three to nine days, so the first predetermined time is set to three to nine days.

[0050] Step S4, liquid scintillation counter test: stop the cycle operation of steps S1 and S2 when the second predetermined time is reached, and test the liquid in the multiple replacement bubble samplers and the currently used bubble sampler using a liquid scintillation counter to test the target tritium activity concentration; Optionally, when the second predetermined time is reached, the tritium elements in the tritium-containing waste gas have been absorbed by the multiple replacement bubble samplers, or there is a small amount of tritium elements that can be ignored, and the unabsorbed tritium elements have little effect on the accuracy of the entire experiment, so they can be ignored.

[0051] Optionally, at the second predetermined time, stop the diaphragm pump from pumping the gas in the exhaust hood again, stop the absorption process of the bubble sampler, and measure the collected target tritium activity concentration by using a liquid scintillation counter.

[0052] Optionally, the liquid scintillation counter is that when the radioactive particles (tritium elements in the sample liquid) enter the liquid scintillator (scintillation liquid), interact with the scintillator molecules, excite the molecules to the excited state. When the molecule returns to the ground state, it releases photons. These photons are captured by the photomultiplier tube (PMT) and converted into electrical signals, which are amplified and processed for counting. After counting the tritium elements, the target tritium activity concentration can be obtained.

[0053] In some preferred embodiments, the second predetermined time ranges from 1 to 12 months.

[0054] Optionally, the tritium-containing waste package continuously and uninterruptedly releases tritium-containing waste gas. As time increases, the tritium content in the tritium-containing waste gas gradually decreases until no tritium-containing waste gas is released. This process, under the influence of temperature and humidity, will have different time progress. In order to ensure that the release rate of tritium-containing waste gas tends to be stable, at least one month of time is required. When 12 months are reached, the release rate of tritium-containing waste gas is basically stable, so the range of the second predetermined time is set to 1 to 12 months.

[0055] In some preferred embodiments, after step S4, the method further comprises: using compressed air to purge the exhaust hood at a predetermined flow rate, and sequentially flowing the residual tritium-containing waste gas through the ionization chamber online monitoring system and the replaced bubble sampler, and discharging into the exhaust system.

[0056] Optionally, after the tritium release rate test is completed (after the second predetermined time is reached), compressed air is used to purge the exhaust hood at a certain flow rate, and the residual tritium-containing waste gas is sequentially purged through the ionization chamber online monitoring system, the two-stage bubble sampler, the catalytic bed, and the two-stage bubble sampler, and discharged into the exhaust system after treatment.

[0057] Optionally, after the entire device completes the experiment, the tritium elements in the tritium-containing waste gas are stored by the ionization chamber online monitoring system or the bubble sampler. At this time, the remaining tritium-containing waste gas in the device is released into the exhaust system. Specifically, compressed air is introduced to discharge the tritium-containing waste gas in the entire device to the exhaust system, and the inside of the device is cleaned to adapt to the next experiment.

[0058] Optionally, before the compressed air is introduced, the compressed air needs to be filtered. A second filter is provided to filter aerosols in the compressed air. There are many components in the air, and aerosols exist. The aerosols in the compressed air need to be removed before the compressed air is introduced into the device to prevent further contamination of the device. Therefore, a second filter is provided. The second filter is arranged at the next level of the compressed air inlet, which can effectively filter the aerosols in the compressed air.

[0059] In some preferred embodiments, the predetermined flow rate of the compressed air is 500 mL / min to 5 L / min; and the purging time of the compressed air is 3 h to 12 h.

[0060] Optionally, if the purging speed of the compressed air is too fast, part of the tritium-containing waste gas may not be completely discharged. If the purging speed of the compressed air is too slow, the entire purging time will be too long. Therefore, the flow rate of the compressed air is set to 500 mL / min to 5 L / min.

[0061] Optionally, in order to ensure that the compressed air can completely purge the tritium-containing waste gas, continuous and uninterrupted purging is required, and the purging time is at least three hours. If the purging time is more than 12 hours, there is basically no tritium-containing waste gas in the entire device, and further purging will waste costs. Therefore, the purging time is set to 3 h to 12 h.

[0062] Step S5: Tritium release rate calculation: calculate the tritium release rate based on the target tritium activity concentration.

[0063] Optionally, the bubble sampling method uses water or ethylene glycol as an absorbent, and the tritium-containing waste gas is introduced into a bubble sampler containing a sampling solution to collect tritiated water. When water is used as the sampling solution, the change of the tritiated water activity A in the bubbler with time (tritium release rate) during sampling can be expressed as: wherein C HTO is the target tritium activity concentration of tritiated water in the tritium-containing waste gas, w is the flow rate of the tritium-containing waste gas injected into the bubble sampler, is the absolute humidity of the tritium-containing waste gas flowing out of the bubble sampler, m t is the mass of water in the bubble sampler at time t. is the total activity of tritiated water entering the bubble sampler per unit time, is the total activity of tritiated water carried out of the bubble sampler by air per unit time.

[0064] In some preferred embodiments, the method further comprises: in step S1, when the initial tritium activity concentration is higher than or equal to the first threshold value, confirming that the initial tritium activity concentration measured by the ionization chamber online monitoring system is the target activity concentration; calculating the tritium release rate based on the target tritium activity concentration; wherein the tritium-containing waste gas is ionized in the ionization chamber online monitoring system to form an electric current, and the ionization chamber online monitoring system determines the initial tritium activity concentration in the tritium-containing waste gas based on the electric current.

[0065] Optionally, when the content of tritiated water is in the range of 400Bq / L to 4000Bq / L, the ionization chamber online monitoring system can be used for direct detection because the number of times of replacing the bubble sampler is large. In the detection process, the gas is ionized to separate the tritium element, so as to realize the detection of the tritium element. At the same time, the gas after detection can be discharged into the exhaust system for next step processing or released into the atmosphere.

[0066] Through the above steps S1 to S5, the target gas is re-discharged into the exhaust hood and circulates through the bubble sampler. The purpose of multiple absorption of tritium elements in the tritium-containing waste gas is achieved, so that the tritium element is nearly completely absorbed through multiple circulation absorption, and the detection result is more accurate. Technical effects are achieved, thereby solving the technical problems in the related art that the tritium-containing waste gas not absorbed by the bubble sampler is discharged into the atmosphere, resulting in inaccurate test results of the tritium release rate of the tritium-containing waste package.

[0067] Using the above test method of the tritium release rate of the tritium-containing waste package, the monthly tritium release rate of the tritium-containing waste package can be tested, and the relationship between the total activity of tritium in a single tritium-containing waste package and the tritium release rate is gradually established, providing a basis for the safe disposal, storage and management of the tritium-containing waste package. At the same time, the closed-loop circulation test method of the catalytic bubble sampler and the liquid scintillation counter can estimate the proportion of different forms of tritium released from the tritium-containing waste package, thereby providing data reference for possible chemical reactions of the tritium-containing waste package during storage.

[0068] The above is only the preferred embodiment of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, several improvements and refinements can be made, which should also be considered as the protection scope of the present application.

Claims

1. A method of testing the tritium release rate of tritium-containing waste, characterized in that, The method comprises: S1. Preliminary monitoring of ionization chamber After the tritium-containing waste gas stream released by the tritium-containing waste package in the exhaust hood passes through the mass flow meter, it is continuously input into the ionization chamber online monitoring system to determine the initial tritium activity concentration in the tritium-containing waste gas; S2. Bubble generator sampling When the initial tritium activity concentration is lower than a first threshold value, the tritium-containing waste gas in the ionization chamber online monitoring system is guided to enter an initial bubble sampler after passing through a refrigeration system, to collect tritiated water in the tritium-containing waste gas, and obtain a target gas, wherein the tritiated water is a compound containing tritium elements, and part of the tritiated water remains in the initial bubble sampler; S3. Replacement of bubble sampler The target gas is guided to be discharged into the exhaust hood, and after passing through the mass flow meter, it is again introduced into the ionization chamber online monitoring system, and steps S1 and S2 are cyclically operated; during the cyclic operation of steps S1 and S2, the initial bubble sampler is removed and replaced with a new bubble sampler every time a first predetermined time is reached; S4. Liquid scintillation counter test After a second predetermined time is reached, the cyclic operation of steps S1 and S2 is stopped, and the liquid in the bubble samplers taken out multiple times and the currently used bubble sampler is tested for target tritium activity concentration using a liquid scintillation counter; S5. Tritium release rate calculation The tritium release rate is calculated based on the target tritium activity concentration.

2. A method of testing the tritium release rate of a tritium-containing waste package according to claim 1, characterized in that, Step S2 comprises: The tritium-containing waste gas in the ionization chamber online monitoring system is guided to flow into a first initial bubble sampler after passing through a first refrigeration system, to collect tritium elements in the form of tritiated water in the tritium-containing waste gas, and obtain a first gas; The first gas is input into a catalytic bed, and the tritium-containing small-molecule organic matter and hydrogen tritium in the first gas are catalytically converted into the form of tritiated water to obtain a second gas; The second gas flows into a second initial bubble sampler after passing through a second refrigeration system, to collect tritium elements in the form of tritiated water in the second gas, and obtain a target gas.

3. The method according to claim 2, wherein: The first initial bubble sampler and the second initial bubble sampler are both secondary bubble samplers; The volume of the sampling liquid in the initial bubble sampler is 100-500 mL; The sampling liquid in the initial bubble sampler includes but is not limited to water or ethylene glycol; The first predetermined time range for replacing the initial bubble sampler is 3-9 days.

4. The method for testing the tritium release rate of tritium-containing waste according to claim 1, characterized in that, The method further comprises: In step S1, when the initial tritium activity concentration is higher than or equal to the first threshold value, the initial tritium activity concentration measured by the ionization chamber online monitoring system is confirmed as a target activity concentration; The tritium release rate is calculated based on the target tritium activity concentration; Wherein, the tritium-containing waste gas is ionized in the ionization chamber online monitoring system and forms an electric current, and the ionization chamber online monitoring system determines the initial tritium activity concentration in the tritium-containing waste gas based on the electric current.

5. The method of claim 1, wherein the tritium release rate is measured by the following equation: ###0001### where: t = time, s T = tritium release rate, g / s g = grams of tritium released, g T0 = initial tritium content, g After step S4, the method further comprises: The exhaust hood is purged with compressed air at a predetermined flow rate, and the residual tritium-containing waste gas sequentially flows through the ionization chamber online monitoring system and the replaced bubble sampler, and is discharged into the exhaust system. 6.The method of claim 5, wherein the predetermined flow rate of the compressed air is 500 mL / min to 5 L / min. The purging time of the compressed air is 3 h to 12 h. 7.The method of claim 1, wherein the predetermined flow rate of the compressed air is 500 mL / min to 5 L / min. 8.The method of claim 1, wherein the predetermined flow rate of the compressed air is 500 mL / min to 5 L / min. The exhaust hood needs to meet the requirement of less than 2.5 x 10 -3 h -1 . The first threshold range of the initial tritium activity concentration is 400 Bq / L to 4000 Bq / L. 9.The method of claim 1, wherein the flow rate of the tritium-containing waste gas through the mass flow meter is 200 mL / min to 2 L / min. 10.The method of claim 1, wherein the second predetermined time is 1 to 12 months. ​ ​ ​

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