CN111292863B - Tritium measuring system and method for pool reactor - Google Patents
Tritium measuring system and method for pool reactor Download PDFInfo
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- CN111292863B CN111292863B CN202010105635.3A CN202010105635A CN111292863B CN 111292863 B CN111292863 B CN 111292863B CN 202010105635 A CN202010105635 A CN 202010105635A CN 111292863 B CN111292863 B CN 111292863B
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C17/00—Monitoring; Testing ; Maintaining
- G21C17/02—Devices or arrangements for monitoring coolant or moderator
- G21C17/022—Devices or arrangements for monitoring coolant or moderator for monitoring liquid coolants or moderators
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- 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
Abstract
Embodiments of the invention provide a tritium measurement system (100) for a pool reactor, comprising: -an attenuation module (10) arranged in connection with a coolant circuit of the pool reactor, from which coolant flows into the attenuation module (10), the attenuation module (10) attenuating the coolant; a measuring module (11) arranged in connection with the attenuation module (10) for measuring the tritium activity of the attenuated coolant flowing out through the attenuation module (10); and a circulation module (12) which is connected to the measurement module (11) and discharges the coolant after the measurement to the coolant circuit of the pool reactor. According to the tritium measuring system provided by the embodiment of the invention, the tritium measuring precision is improved, the environment-friendly performance and the safety of measurement are improved, the long-term measuring operation cost can be reduced, and the personnel investment is reduced.
Description
Technical Field
The invention relates to the technical field of radioactivity monitoring, in particular to a tritium measuring system and a tritium measuring method for a pool reactor.
Background
Tritium is a radioactive isotope of hydrogen and has wide applications in the fields of medicine, research, industry, and especially the nuclear industry (e.g., as the main light material for nuclear fusion reactions). However, in the nuclear industry, tritium-containing waste gases and waste waters are discharged to the environment in low concentrations during tritium-related production activities. Tritium in the environment can be directly taken by human beings through air and water, can be absorbed by plants and animals, and is transmitted into human bodies through animal and plant foods, so that the human health is harmed. Therefore, how to effectively monitor the radioactivity level of tritium generated in the nuclear reaction process becomes a hot spot problem of tritium radiation protection.
For example, during operation of a heat-fed reactor, the primary sources of tritium include reactor nuclear fuel fission generation, and deuterium activation generation in coolant water; the tritium thus produced enters the environment in liquid and gaseous form, adversely affecting the nuclear reactor personnel and the public. In order to reduce the irradiation dose of workers and the public, the radioactivity level of tritium generated in the nuclear reaction process is effectively monitored in time, which is a necessary prerequisite for implementing protection.
In a nuclear reactor coolant loop, due to the presence of other high-activity radionuclides and the relatively low radioactivity of tritium, if the radioactivity level of tritium from the coolant loop is directly measured, the measurement is prone to be inaccurate, and therefore, the application provides a related measurement device or method to improve the problem.
Disclosure of Invention
Embodiments of the invention provide a tritium measurement system for a pool reactor, comprising: an attenuation module disposed in connection with a coolant circuit of the pool reactor, into which coolant flows from the coolant circuit, the attenuation module attenuating the coolant; a measurement module configured to be coupled to the attenuation module to measure tritium activity of the attenuated coolant flowing out through the attenuation module; and the circulating module is connected with the measuring module and used for discharging the coolant after the measurement is finished to the coolant loop of the pool type reactor.
According to the measuring system provided by the embodiment of the invention, the tritium activity level of the coolant in the reactor coolant loop is measured, and the coolant is measured after being attenuated, so that the interference of other radionuclides in the coolant can be effectively eliminated, and the tritium measurement precision is improved; meanwhile, the coolant after the measurement is introduced into the coolant loop again through the circulating module, so that the measurement environmental protection performance can be improved, and the irradiated dose level of related personnel is reduced. Furthermore, according to the measuring system provided by the embodiment of the invention, the cost of long-term measuring operation can be reduced, and the input of personnel is reduced.
The measurement system according to the embodiment of the present invention may further have the following technical features:
according to one embodiment of the invention, the attenuation module comprises a first vessel into which the coolant flows and in which it stays for a preset time.
According to an embodiment of the invention, when the tritium measurement system is used to measure the coolant of the first loop of the coolant loop, the preset time is greater than zero; the first circuit is connected to the pool reactor and provides circulation of coolant for conducting heat away from the core.
According to one embodiment of the invention, when the tritium measurement system is used to measure the coolant of the second or third circuit of the coolant circuit, the preset time is zero; the second loop is connected with the first loop to form a closed second loop; the third loop is connected with the second loop to form a closed third loop, and the third loop is a heat supply loop.
According to one embodiment of the invention, the passage formed by the first container is rectilinear.
According to one embodiment of the invention, a baffle is provided in the first container for extending the decay time of the coolant.
According to one embodiment of the invention, the channel formed by the first container is helical.
According to one embodiment of the invention, the measuring module comprises a second container, a detection device and a processing device; the coolant flowing out of the attenuation module flows into the second container, the detection device measures tritium activity of the coolant, and measurement data are transmitted to the processing device to be processed.
According to one embodiment of the invention, the detection device is a liquid scintillation detection device.
According to another aspect of the present invention, there is provided a tritium measurement system for a pool reactor, comprising: a sampling module disposed in connection with a coolant circuit of the pool reactor, coolant flowing from the coolant circuit to the sampling module; an attenuation module configured to be coupled to the sampling module to attenuate the coolant flowing out through the sampling module; a measurement module configured to be coupled to the attenuation module to measure tritium activity of the attenuated coolant flowing out through the attenuation module; and the circulating module is connected with the measuring module and used for discharging the coolant after the measurement is finished to a coolant loop of the pool type reactor.
According to another aspect of the present invention, there is provided a tritium measurement method for a pool reactor, using the above tritium measurement system, the tritium measurement method including the steps of: introducing coolant in a coolant circuit of the pool reactor into the attenuation module, attenuating the coolant; introducing the decayed coolant to the measurement module, and measuring tritium activity of the coolant; after the measurement is finished, the coolant is discharged into a coolant loop of the pool reactor through the circulation module.
According to the measuring method provided by the embodiment of the invention, the coolant from the coolant loop is attenuated and then measured, so that the interference of other radioactive nuclides in the coolant can be effectively eliminated, and the tritium measuring precision is improved; meanwhile, the circulating module is adopted to discharge the coolant after the measurement is finished, so that the measurement environmental protection performance can be improved, and the irradiated dose level of related personnel is reduced.
According to one embodiment of the invention, the step of attenuating the coolant comprises: when the coolant flows into the first container of the attenuation module, the coolant stays in the first container for a preset time.
According to an embodiment of the invention, the preset time is greater than zero when the coolant comes from the first loop of the coolant loop of the pool reactor; the preset time is zero when the coolant is from the second or third circuit of the coolant circuits of the pool stack.
According to one embodiment of the invention, the step of measuring the tritium activity of the coolant comprises: introducing the coolant flowing out of the first container into a second container of the measurement module, measuring a level of the coolant within the second container; and when the liquid level reaches a preset value, measuring the tritium activity of the coolant by adopting a detection device of the measurement module, and transmitting measurement data to a processing device of the measurement module for processing.
Drawings
Other objects and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings, and will assist in a comprehensive understanding of the invention.
FIG. 1 is a schematic diagram of a tritium measurement system according to one embodiment of the invention;
FIG. 2 is a schematic diagram of a tritium measurement system according to another embodiment of the invention.
It is noted that the drawings are not necessarily to scale and are merely illustrative in nature and not intended to obscure the reader.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention. It should be apparent that the described embodiment is one embodiment of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.
First, the structure of the pool reactor according to an embodiment of the present invention is described.
The pool reactor comprises a reactor pool, a core and a coolant loop, wherein the core is arranged at the bottom of the reactor pool, and the coolant loop provides coolant for the core so that the coolant carries out heat generated by the core.
The reactor pool may be located, for example, underground (below the horizon), with the core located at the bottom of the reactor pool, and with a certain negative pressure maintained above the pool level, in order to improve the safety of the reactor operation. The water (coolant) in the reactor pool enters the reactor core from the lower part, is heated in the reactor core and then enters a primary pump room outside the pool along the ascending cylinder, and is pumped back into the pool by the pump after passing through the heat exchange device, thereby forming a first loop.
Further, when the heat that the pool type reactor produced was used for regional heat supply, can set up the coolant return circuit into a plurality of circulation circuit, can improve the security that the heat transfer was implemented to the coolant return circuit on the one hand, on the other hand will be close to the coolant return circuit of reactor core and keep apart with the heat supply network to guarantee can not bring the radioactivity to city heat supply network.
In particular, the coolant circuit comprises, for example, three circulation circuits: a first loop, a second loop, and a third loop. The first loop is connected with the reactor pool to form a circulation loop, so that coolant is provided for the reactor core, the reactor core is kept at a normal temperature, and heat generated by the reactor core is carried out in time; the second loop is connected with the first loop and the urban heat supply network, and the first loop is isolated from the urban heat supply network, so that radioactivity of the urban heat supply network can be avoided under the accident condition. The third loop is connected with the urban heat supply network. Heat exchange devices are arranged between the first loop and the second loop and between the second loop and the third loop to implement heat exchange, so that heat generated by the reactor is transferred to the second loop through the first loop via the heat exchange devices, then transferred to the third loop via the heat exchange devices, and finally transferred to a heat supply network for heat supply.
Compared with the traditional heat sources (coal and petroleum), the nuclear energy is used for supplying heat to the area, so that the pollution emission can be effectively reduced, the heat supply safety is guaranteed, the situation of increasingly serious energy supply shortage is favorably relieved, and the method has positive significance for protecting the environment and the health of people, relieving the coal transportation pressure and the like.
According to the pool reactor provided by the embodiment of the invention, the heat of the reactor core is carried out by using the coolant to supply heat for cities, and in the process, the radioactivity level of the radioactive nuclide in the coolant needs to be considered, so that safety guarantee is provided for workers and the public of the nuclear power station. For the coolant loop, especially the first loop (i.e. the coolant main loop), the coolant is directly contacted with the reactor core and is easily activated by neutrons to generate a plurality of radioactive activation products, so that the level of radioactivity of the coolant from the first loop is high and becomes a main object for monitoring; the radioactivity levels of the second and third circuits are relatively low.
Meanwhile, for example, in a light water reactor, the radioactivity of an activated product such as nitrogen 16 in coolant water (oxygen 16 in water is activated to generate nitrogen 16, the half-life of the nitrogen 16 is short, the radioactivity is high, and interference on the measurement of tritium is easily caused) is much greater than that of tritium (the concentration of tritium is called as activity of tritium in water quality analysis), and if the radioactivity of tritium in the coolant is directly measured, the measurement result is easily interfered by other radionuclides, so that it is necessary to eliminate the interference, and a more accurate measurement system and method of tritium activity are provided.
Referring to fig. 1, a tritium measurement system 100 for a pool reactor according to an embodiment of the present invention includes: an attenuation module 10 provided in connection with a coolant circuit of the pool reactor, the coolant flowing from the coolant circuit into the attenuation module 10, the attenuation module 10 attenuating the coolant; a measuring module 11, which is connected to the attenuation module 10 and measures the tritium activity of the attenuated coolant flowing out of the attenuation module 10; and a circulation module 12 connected to the measurement module 11 and configured to discharge the coolant after the measurement to a coolant circuit of the pool reactor.
Tritium is a low-energy beta decay nuclide, the energy of the beta particle released by the tritium is low, and interference factors existing in tritium measurement need to be eliminated in order to improve the measurement accuracy of the tritium.
Specifically, for avoiding directly carrying out tritium measurement on the coolant in the coolant loop, attenuation module 10 is arranged before measurement module 11, namely, the coolant flows out of the coolant loop and then is attenuated through attenuation module 10, then flows into measurement module 11 to be measured, and finally, for improving the measurement environmental protection performance, the coolant after the measurement is discharged through circulation module 12 and flows back to the coolant loop, so that the radioactive substances in the coolant are prevented from being discharged into the environment to cause pollution.
Further, the attenuation module 10 is used for attenuating radionuclides (mainly nitrogen 16, with a half-life of 7.11s) other than tritium in the coolant, so that the radioactivity level of the coolant passing through the attenuation module 10 is attenuated, and the tritium is a low-energy nuclide and has a long half-life (with a half-life of 12.33 years), so that the attenuation module 10 does not affect the coolant, and the tritium is measured at the measurement module 11, and the measurement accuracy is improved.
Further, the attenuation module 10 includes, for example, a pipe, a valve, and a pump, the pipe is connected to a corresponding pipe of the coolant circuit, and the coolant is led out from the coolant circuit, and the flow rate, the flow velocity, and the like of the coolant are controlled by the valve and the pump. The attenuation module 10 can set the flowing time of the coolant, so that the radioactive nuclides such as nitrogen 16 in the coolant are sufficiently attenuated, interference factors for measuring the activity of tritium are eliminated, and the measurement precision is improved.
Further, the measurement module 11 is used for measuring the activity of tritium, realizes the radioactivity level monitoring of tritium in the coolant to in time survey the emergence of abnormal state according to the activity level that obtains, propose safeguard measure etc. avoid it to discharge in the environment, cause the harm to relevant personnel. Tritium-based radiation energy is low, and the key to the measurement of radioactivity lies in eliminating interference factors, improving detection efficiency and the like.
Similarly, pipes, valves, pumps are provided between the attenuation module 10 and the measurement module 11 to control the flow of the coolant.
Further, the circulation module 12 flows the coolant to form a circulation loop, which is connected to the measurement module 11 and the coolant loop, so that the coolant discharged from the measurement module 11 flows into the coolant loop. The circulation module 12 includes, for example, pipes, valves, and pumps, the valves adopt, for example, one-way valves to prevent the coolant in the coolant loop from flowing directly into the measurement module 11 to damage the equipment thereof (the undamped coolant contains multiple radionuclides and has a high radiation level), and accordingly, only allow the coolant to flow from the measurement module 11 into the coolant loop through the valves.
It will be appreciated that the pipes, valves, pumps used to connect the modules to each other may be shaped or numbered as appropriate to achieve a controlled flow of coolant.
In one embodiment, the attenuation module 10 includes a first vessel 101, and the coolant flows into the first vessel 101 and stays in the first vessel 101 for a predetermined time.
Referring to fig. 1, in order to extend the decay time of the coolant, the decay module 10 is provided with a first container 101 so that the coolant stays for a predetermined time while flowing through the first container 101 through a pipe, and then flows into the measurement module 11.
Specifically, the first container 101 is, for example, a storage container having a certain capacity. The material of the first container 101 is lead, for example, to shield radioactivity. Lead wall thickness and the like may be set according to radioactivity level (e.g., nitrogen 16 has high radioactivity and the energy of the gamma photons generated is strong).
Meanwhile, reasonable residence time is set according to different decay periods of interference factors (radionuclides such as nitrogen 16) so as to realize sufficient attenuation.
In one embodiment, when the tritium measurement system 100 is used to measure coolant of a first loop of a coolant loop, the preset time is greater than zero; the first loop is connected to the pool reactor and provides for circulation of coolant for conducting heat away from the core.
As can be seen from the above, the coolant in the first loop contacts the reactor core, the coolant is activated by the reactor core neutrons to generate a plurality of radionuclides, for example, the activity of nitrogen 16 generated by activating oxygen 16 in water is high, and is likely to interfere with the measurement of tritium with lower activity, and in order to eliminate the interference, the attenuation module 10 is adopted to attenuate the nuclides such as nitrogen 16, so as to reduce the activity level (for example, the activity level can be reduced by several orders of magnitude).
Specifically, the coolant from the first circuit is introduced into the first container 101 and is left for a predetermined time, for example, 1 minute, 5 minutes, 10 minutes, 30 minutes, 1 hour, 10 hours, etc., depending on the degree of attenuation to be achieved. Therefore, when the first-loop coolant is attenuated in the first container 101 and then enters the measuring module 11 to measure tritium, the measuring precision can be improved.
In one embodiment, when the tritium measurement system 100 is used to measure coolant in a second or third loop of the coolant loop, the preset time is zero; the second loop is connected with the first loop to form a closed second loop; the third loop is connected with the second loop to form a closed third loop, and the third loop is a heat supply loop.
Because the second loop or the third loop coolant and the first loop coolant are mutually isolated, the coolant from the second loop or the third loop has low activation level, and the decay time can be reduced, so that the tritium is measured in real time, and the activity level of the tritium is monitored.
Specifically, when measuring the coolant of the second circuit or the third circuit, the coolant can be controlled to flow directly through the pipe, the first container 101, and into the measurement module 11 for measurement.
In one embodiment, the channels formed by the first container 101 are linear.
In order to set the decay time, the shape of the channel formed by the first container 101 is set. When the decay time needs to be set short, the passage is set to be linear (such as rectangular or cylindrical), for example, so that the coolant flows into the first container 101 and continues to flow after a predetermined time. Alternatively, when measuring the coolant of the second or third circuit, there is no need to attenuate the coolant to provide a convenient passage for the coolant to flow.
In one embodiment, a baffle is provided within the first container 101 to extend the decay time of the coolant.
Specifically, when measuring the coolant of the first circuit, in order to extend the coolant decay time, when the passage of the first tank 101 is linear, a partition plate is provided in the first tank 101 to increase the distance over which the coolant flows while reducing the flow rate thereof, ensuring sufficient decay of the coolant. The separator is provided in plural, for example, in a shape to increase a distance over which the coolant flows. The separator plates are provided with, for example, passages to facilitate the flow of coolant therethrough.
It will be appreciated that the location and number of baffles within the first vessel 101, the shape of the baffles, etc. may be arranged as desired to achieve sufficient attenuation of the coolant.
In one embodiment, the channel formed by the first container 101 is helical.
Specifically, in order to increase the coolant flow distance, the channel of the first container 101 may be provided in a spiral shape. When the coolant flow distance increases, the time for the coolant to stagnate in the first reservoir 101 (i.e., close the valve between the pipes of the attenuation module 10 and the measurement module 11 without allowing the coolant to flow into the measurement module 11) can be reduced accordingly, or the coolant can be made to flow directly through the first reservoir 101 (with the attenuation satisfied) to the measurement module 11.
In one embodiment, the first container 101 has a conduit S therein, which includes an inlet and an outlet, which are connected to respective conduit ports for the flow of coolant into and out of the first container 101, such that coolant flows through the conduit S as it flows through the first container 101. The pipe S is, for example, a bent pipe structure, as shown in fig. 1, and it is advantageous to increase the distance of the coolant flow while reducing the flow rate of the coolant when the coolant flows through the pipe S, thereby achieving the attenuation in a desired time.
It will be appreciated that the channels formed by the first container 101 may be arranged in the manner described above or otherwise, and that the conduits S may be arranged in the manner described above or otherwise, provided that sufficient attenuation of the coolant is achieved. Meanwhile, according to the arrangement of the channel of the first container 101, the residence time of the coolant in the first container 101 is reasonably adjusted to improve the operation flexibility.
In one embodiment, the measurement module 11 comprises a second container 111, a detection device 112 and a processing device 113; the coolant flowing out of the attenuation module 10 flows into the second container 111, and the detection device 112 measures the tritium activity of the coolant and transmits the measurement data to the processing device 113 for processing.
Referring to fig. 1, tritium activity measurements are taken after the coolant enters measurement module 11 via decay module 10. Specifically, the second container 111 provides a measurement space for the coolant, so that the detection device 112 can conveniently perform measurement, and meanwhile, the influence of the contact of the coolant and the detection device 112 on equipment (tritium has strong penetrability) is reduced; further, a processing device 113 is arranged outside the pipeline so as to process and analyze the measured data in time and prepare for subsequent protection work.
The second container 111 is, for example, a storage container, and is convenient for storing the coolant and performing operations such as level adjustment. The detection means 112 is used to measure the activity of the tritium in radioactivity (e.g. by measuring the energy of the beta particles). The processing device 113 is used for signal conversion, data calculation, analysis, and the like.
In one embodiment, the detection device 112 is a liquid scintillation detection device.
The liquid scintillation detection principle is that a sample to be detected and scintillation liquid are mixed and interact to generate a fluorescence effect, the detection method can avoid sublimation and self-absorption of the sample, and has the advantages of high detection efficiency and the like for low-energy beta particles.
In a preferred embodiment, the detection device is a Quantulus 1220 liquid scintillation counter. The instrument has low noise background value, and has the advantage of accurate measurement especially for counting low-radioactivity samples which need to be measured for a long time. The measurement principle is as follows: the radioactive sample to be measured is mixed with the scintillation material, the radiation energy generated by the radioactive sample is converted into light energy by the scintillation material such as fluorescent agent, and the light emitted by the scintillation pulse is converted into electric pulse by the photomultiplier tube, thereby achieving the purpose of measuring the energy and the quantity of the radiation rays.
Referring to fig. 1, the detecting device 112 includes, for example, a detecting probe 1120, a light collecting portion 1121, a photomultiplier 1122 and a counter 1123, the detecting probe 1120 is filled with a scintillation liquid, the scintillation liquid interacts with a β -ray of tritium to be detected to emit fluorescence photons, the fluorescence photons are received and converted by the photomultiplier 1122 through the light collecting portion 1121 to be photoelectrons, the photoelectrons are multiplied, collected on an anode of the photomultiplier, and the photoelectrons are transmitted to the counter 1123 in a form of pulse signals for counting; thus, the level of beta radiation is measured by the detection device 112 to obtain the activity of tritium.
According to the tritium measurement system 100 for the pool reactor, provided by the embodiment of the invention, the attenuation module 10 is utilized to reduce the interference of nitrogen 16 and other radioactive nuclides with short decay period in the coolant on tritium, and improve the tritium measurement precision; meanwhile, the circulating module 12 is used for processing the coolant after the measurement is finished so as to improve the environmental protection of the measurement.
In other embodiments, a tritium measurement system 200 for a pool reactor includes: a sampling module 20 disposed to be connected to a coolant circuit of the pool reactor, the coolant flowing from the coolant circuit to the sampling module 20; an attenuation module 21, which is connected to the sampling module 20 and attenuates the coolant flowing out through the sampling module 20; a measuring module 22, arranged in connection with the damping module 21, for measuring the tritium activity of the damped coolant flowing out through the damping module 21; and a circulation module 23 connected to the measurement module 22 and configured to discharge the coolant after the measurement to a coolant circuit of the pool reactor.
Specifically, referring to fig. 2, measurement system 200 is compared to measurement system 100 with a sampling module 20 positioned before attenuation module 21. The sampling module 20 thus draws coolant from the coolant circuit, which then flows into the attenuation module 21 and the subsequent modules. The sampling module 20 includes, for example, pipes, valves, and pumps, which are connected to the relevant pipes of the coolant circuit from which the coolant is drawn, while the flow rate, and the like of the coolant are controlled using the valves and pumps.
The sampling module 20 is, for example, a branch from the coolant circuit for the withdrawal of the coolant (sample) to be measured without affecting the operation between the coolant circuit and the core. The speed and time of the coolant (sample) to be measured flowing through the sampling module 20 are controlled by adjusting the opening of the valve on the pipeline, and correspondingly, the attenuation time of the coolant at the attenuation module 21 is adjusted, so that flexible control is realized according to the setting of a measuring system.
Further, pipes and valves are arranged between the sampling module 20 and the attenuation module 21 to control the flow of the coolant. According to needs, the pipeline of sampling module 20, the pipeline between sampling module 20 and the decay module 21 can set up different length, realize the nimble control of coolant flow, for example the pipeline of sampling module 20 sets up longer to make decay module 21, measurement module 22 keep away from the first circuit that is close to the reactor core, reduce the radiation of reactor core to staff, improve the operational safety.
Referring to fig. 2, in other embodiments, the decay module 21 provides a first container 211 that is used to extend the decay time of the coolant to eliminate interference with tritium measurements by radionuclides such as nitrogen 16 in the coolant.
Further, the passage of the first container 211 may be provided in a linear shape, a spiral shape, etc. so as to adjust a flow distance, a flow time, etc. of the coolant to achieve sufficient attenuation of the coolant.
Further, the measurement module 22 comprises a second container 221, a detection device 222 and a processing device 223; the coolant flowing out of the attenuation module 21 flows into the second container 221, and the detection device 222 measures the tritium activity of the coolant and transmits the measured data to the processing device 223 for processing.
Further, the circulation module 23 is used for discharging and introducing the coolant after the measurement is finished into the coolant loop, so as to prevent radioactive substances in the coolant from being discharged into the environment and causing pollution. The circulation module 23 includes, for example, pipes, valves, and pumps, the valves adopt, for example, one-way valves to prevent the coolant in the coolant loop from directly flowing into the measurement module 22 to damage the equipment thereof (the undamped coolant contains multiple radionuclides and has a high radiation level), and accordingly, only allow the coolant to flow from the measurement module 22 into the coolant loop through the valves.
It is understood that the modules in the measurement system 100 and the measurement system 200 may be configured in the same or different structures to meet different measurement requirements.
Based on the tritium measurement system of the embodiment of the invention, the invention also provides a tritium measurement method for the pool reactor, which is explained as follows by taking the tritium measurement system 100 as an example.
A tritium measurement method according to an embodiment of the present invention includes the steps of: introducing the coolant in the coolant circuit of the pool reactor into the attenuation module 10 for attenuating the coolant; introducing the decayed coolant into a measuring module 11, and measuring tritium activity of the coolant; after the measurement is finished, the coolant is discharged into the coolant circuit of the pool reactor by means of the circulation module 12.
Referring to fig. 1, a coolant sample to be measured flows into a branch by opening a valve on a pipe connected to a coolant loop of an attenuation module 10, and is attenuated in the attenuation module 10; subsequently, a valve between the attenuation module 10 and the measurement module 11 is opened to allow coolant to flow into the measurement module 11 for the coolant tritium activity measurement; finally, the valves and pumps on the pipelines of the circulation module 12 are adjusted to discharge the measured coolant into the coolant loop again, so that the flow circulation is realized.
The tritium measuring method provided by the embodiment of the invention is simple in operation method and beneficial to improving the tritium measuring precision and the measuring safety.
In one embodiment, the step of attenuating the coolant comprises: when the coolant flows into the first container 101 of the attenuation module 10, it stays in the first container 101 for a preset time.
To ensure that the radionuclide such as nitrogen 16 in the coolant is attenuated, the valve between the first container 101 and the measurement module 11 is closed to allow the coolant to stay in the first container 101 when the coolant flows into the first container 101; the dwell time can be set according to the species of nuclide, the degree of attenuation required.
In one embodiment, the preset time is greater than zero when the coolant is from the first loop of the coolant loop of the pool reactor; the preset time is zero when the coolant comes from the second or third circuit of the coolant circuits of the pool stack.
As can be seen from the above, there are various nuclides in the first loop coolant that interfere with the tritium measurement, thereby allowing the coolant to remain there, for example, for 1 minute, 5 minutes, 10 minutes, 30 minutes, 1 hour, 10 hours, etc., when the first loop coolant flows into the first vessel 101, to reduce the activity of the nuclides such as nitrogen 16 in the coolant; the coolant of the second loop or the third loop is isolated from the coolant of the first loop, and the activation degree of the coolant is very small, so that the attenuation step can be omitted, the coolant is directly measured, and the tritium activity is monitored in real time.
In one embodiment, the step of measuring the tritium activity of the coolant comprises: introducing the coolant flowing out of the first container 101 into the second container 111 of the measuring module 11, measuring the level of the coolant in the second container 111; when the liquid level reaches a preset value, the tritium activity of the coolant is measured by the detection device 112 of the measurement module 11, and the measurement data is transmitted to the processing device 113 of the measurement module 11 for processing. The requirement for measuring the liquid level is that the liquid level is higher than the heights of all probes in the detection device so as to improve the measurement precision.
In particular, the measurement module 11 provides a convenient operating environment for tritium measurement, while ensuring the safety of the operator (reducing the dose level of the radiation to the operator) and reducing the influence of the radiation on the detection device.
In a preferred embodiment, the detection device 112 may be a liquid scintillation detection device, such as a Quantulus 1220 liquid scintillation counter, utilizing a static radiation shield formed by a detection probe and a dynamic shield formed by a photomultiplier tube to increase the signal-to-noise ratio and thus the detection efficiency.
Further, when the measurement is finished, the pipe valve of the circulation module 12 is opened, and the coolant is returned to the coolant loop by using a pump, so that the radioactive substances in the coolant are prevented from being discharged into the environment and endangering the health of personnel.
The tritium measuring method applied to the tritium measuring system 100 or the tritium measuring system 200 may further include the steps of: after the coolant has finished decaying at the decay module and enters the measurement module, gamma rays are measured in the coolant before the tritium activity is measured. Therefore, interference of gamma rays on measurement of beta rays in tritium activity measurement is eliminated, and measurement accuracy is improved.
In a preferred embodiment, the tritium measurement method and the calculation mode are described in combination with the structure, the operation mode and the like of the pool reactor.
According to the pool type reactor disclosed by the embodiment of the invention, the reactor is a deep water pool type low-temperature heat supply reactor, the heat source is provided by utilizing nuclear energy to realize urban regional heat supply, the reactor can work under the conditions of low temperature and low pressure, the characteristics of simple equipment and system, safety, reliability, low investment and the like are achieved, and the problems of high cost, serious pollution and the like existing in a coal-fired heat supply mode can be solved.
Specifically, the pool reactor has a coolant system including a plurality of coolant circulation loops, such as a first loop, a second loop and a third loop, the first loop constitutes a coolant main loop, the second loop isolates the first loop from the third loop (as a heat supply loop) to prevent radioactive water in the first loop from leaking into the heat supply network and causing harm to the public, and the second loop is also a closed circulation loop.
For the pool reactor described above, the main sources of tritium include: (1) core fuel fission generation; (2) deuterium is formed by neutron activation in the main loop coolant water.
Before tritium is measured using the measurement system of the present invention, a reference value can be provided for the measurement by calculating the activity level of tritium from the source.
This fraction is of lesser yield for tritium produced by core fuel fission (uranium nuclear fission). Most of the tritium is contained in the fuel element cladding, with only a small portion entering the primary loop coolant through cracks or fissures, or through diffusion. The activity of tritium produced by fuel fission is about 1.63E +13Bq/a per year, and if the fraction of tritium entering the primary loop coolant is 2%, the activity of this fraction of tritium is 3.26E +11Bq/a, as calculated by the ORIGEN2 program.
For tritium formed by activation of deuterium by neutrons in the main loop coolant water, the rate of tritium generation can be represented by the following formula:
P＝λ·σ·φ·Ab·NA·m/M
wherein, P is the generation rate and the unit is Bq/s; λ is the decay constant of T (tritium); sigma is a reaction section and is expressed in the unit of barn; phi is neutron flux density in cm-2s-1(ii) a Ab is the natural abundance of the mother nucleus; m is the mass of the mother nucleus; m is the molar mass;
wherein, if the total mass of the coolant in the active zone is 2288.25L, the thermal neutron flux density of the active zone is 2.6 x 1013cm-2s-1Reaction cross section of 5.7X 10-4The natural abundance of deuterium in the coolant was taken to be 0.015% for barn, and the rate of tritium production was 601.65Bq/s, i.e. 1.89E +10Bq/a, as calculated by the above formula.
Thus, the amount of tritium produced in the main circuit coolant per year is shown in the following table:
further conversion results in that the specific activity level of tritium in the main loop coolant is 2.09E +05Bq/kg per year.
The theoretical calculation provides reference for actually measuring the activity level of the tritium, and is convenient for comparing an actually measured value with a theoretical value, so that whether the activity level of the tritium is abnormal or not is analyzed, and the purposes of monitoring and protection are achieved.
When tritium activity is measured using a liquid scintillation measurement method, the activity level of tritium is characterized by measuring the energy of the beta particle, e.g., the beta particle interacts with the scintillation material to emit photons, the number of which can be calculated by the following formula:
N＝εE/e
in the formula, N is the number of photons, E is the energy of tritium, E is the energy of photons, and epsilon is the reaction cross section.
Wherein the photon energy is wavelength dependent:
e＝hv＝hc/λ
in the formula, h is Planck constant, c is light speed, and lambda is photon wavelength.
Further, the actual measurement result of tritium is obtained by converting the optical signal into an electrical signal, amplifying, analyzing, and the like.
It is understood that other methods may be used to measure tritium activity to meet the actual application requirements.
It should also be noted that, in the case of the embodiments of the present invention, features of the embodiments and examples may be combined with each other to obtain a new embodiment without conflict.
The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and the scope of the present invention is subject to the scope of the claims.
Claims (14)
1. A tritium measurement system (100) for a pool reactor, comprising:
-an attenuation module (10) arranged in connection with a coolant circuit of the pool reactor, from which coolant flows into the attenuation module (10), the attenuation module (10) attenuating the coolant, the attenuation module (10) being adapted to attenuate radionuclides other than tritium in the coolant;
a measuring module (11) arranged in connection with the damping module (10) for measuring the tritium activity of the damped coolant flowing out through the damping module (10); and
a circulation module (12) connected to the measurement module (11) and configured to discharge the coolant after the measurement to the coolant circuit of the pool reactor.
2. Tritium measurement system (100) according to claim 1, wherein,
the attenuation module (10) comprises a first container (101), wherein the coolant flows into the first container (101) and stays in the first container (101) for a preset time.
3. Tritium measurement system (100) according to claim 2, wherein,
when the tritium measurement system is used to measure coolant of a first loop of the coolant loop,
the preset time is greater than zero;
the first circuit is connected to the pool reactor and provides circulation of coolant for conducting heat away from the core.
4. Tritium measurement system (100) according to claim 3, wherein,
when the tritium measurement system is used to measure coolant of a second or third of the coolant circuits,
the preset time is zero;
the second loop is connected with the first loop to form a closed second loop;
the third loop is connected with the second loop to form a closed third loop, and the third loop is a heat supply loop.
5. Tritium measurement system (100) according to claim 2, wherein,
the channel formed by the first container (101) is linear.
6. Tritium measurement system (100) according to claim 5, wherein,
a baffle plate for prolonging the decay time of the coolant is arranged in the first container (101).
7. Tritium measurement system (100) according to claim 2, wherein,
the channel formed by the first container (101) is spiral.
8. The tritium measurement system (100) of claim 1,
the measuring module (11) comprises a second container (111), a detection device (112) and a processing device (113);
the coolant flowing out of the attenuation module (10) flows into the second container (111), the detection device (112) measures the tritium activity of the coolant and transmits the measured data to the processing device (113) for processing.
9. A tritium measurement system (100) according to claim 8,
the detection device (112) is a liquid scintillation detection device.
10. A tritium measurement system (200) for a pool reactor, comprising:
a sampling module (20) arranged in connection with a coolant circuit of the pool reactor, from which coolant flows into the sampling module (20);
an attenuation module (21) connected with the sampling module (20) and used for attenuating the coolant flowing out through the sampling module (20), wherein the attenuation module (21) is used for attenuating radionuclides except tritium in the coolant;
a measuring module (22) arranged in connection with the attenuation module (21) for measuring the tritium activity of the attenuated coolant flowing out through the attenuation module (21); and
and a circulation module (23) which is connected to the measurement module (22) and discharges the coolant after the measurement to a coolant circuit of the pool reactor.
11. A tritium measurement method for a pool reactor, employing the tritium measurement system (100) of claim 1, the tritium measurement method comprising the steps of:
-introducing coolant in a coolant circuit of the pool reactor into the attenuation module (10), attenuating the coolant;
introducing the decayed coolant to the measurement module (11), measuring the tritium activity of the coolant;
after the measurement is finished, discharging the coolant into a coolant loop of the pool reactor through the circulation module (12);
wherein attenuating the coolant includes attenuating radionuclides other than tritium in the coolant.
12. A tritium measurement method according to claim 11, wherein,
the step of attenuating the coolant includes:
when the coolant flows into the first container (101) of the attenuation module (10), the coolant stays in the first container (101) for a preset time.
13. A tritium measurement method according to claim 12, wherein,
the preset time is greater than zero when the coolant is from a first of the coolant loops of the pool reactor;
the preset time is zero when the coolant is from the second or third circuit of the coolant circuits of the pool stack.
14. A tritium measurement method according to claim 12, wherein,
the step of measuring the tritium activity of the coolant comprises:
-introducing the coolant flowing out of the first container (101) into a second container (111) of the measuring module (11), measuring the level of the coolant inside the second container (111);
and when the liquid level reaches a preset value, measuring the tritium activity of the coolant by using a detection device (112) of the measurement module (11), and transmitting the measurement data to a processing device (113) of the measurement module (11) for processing.
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