CN-121994840-A - Gas-liquid two-phase flow on-line monitoring method and system for radioactive separation system

Abstract

The invention discloses a gas-liquid two-phase flow on-line monitoring method and a system for a radioactive separation system, which belong to the technical field of fluid detection, and comprise the steps of arranging a reference source for emitting gamma rays with two different energies at the outer side of a cleaning section of a pipeline to be detected, arranging a reference source detector at the opposite side of the pipeline, and measuring the transmittance of the reference source rays through the pipeline, fluid and sediment to obtain a transmission attenuation pair; the invention can realize real-time and high-precision online monitoring of the fluid radioactivity concentration under the working condition of the gas-liquid two-phase flow of the radioactive separation system, synchronously acquire the sediment attachment state parameters and provide reliable data support for system process control, pipeline cleaning management and control and radioactive waste emission compliance judgment.

Inventors

• GU LONG
• WANG GUAN
• Su Xingkang
• HUANG HUA

Assignees

• 福建睿斯科医疗技术有限公司

Dates

Publication Date

20260508

Application Date

20260407

Claims (10)

1. 1. The gas-liquid two-phase flow on-line monitoring method for the radioactive separation system is characterized by comprising the following steps of: a reference source for emitting two gamma rays with different energies is arranged at the outer side of a cleaning section of a pipeline to be tested, a reference source detector is arranged at the opposite side of the pipeline, and the transmittance of the two energies after the reference source rays penetrate through the pipeline, fluid and sediment is measured to obtain a transmission attenuation pair; Inversion is carried out on the basis of the transmission attenuation pair and a pre-acquired clean pipeline transmission reference to obtain the mass thickness of sediment in the pipeline; setting a main detector and a collimator with a narrow view field, so that the detection view field of the main detector is limited to the axis area of the pipeline, and measuring to obtain a main counting rate; Compensating the main counting rate by utilizing the mass thickness of the sediment and the attenuation coefficient of the radionuclide to be detected in the sediment, so as to obtain the compensated counting rate; Performing zero deposit verification at predetermined time intervals, updating the clean pipe transmittance reference and the detection efficiency of the primary detector; and calculating the true radioactive concentration of the flowing fluid according to the compensated counting rate and the updated detection efficiency, and outputting the mass thickness of the sediment.
2. 2. The method for on-line monitoring of a gas-liquid two-phase flow for a radioactive separation system of claim 1, wherein obtaining a transmission attenuation pair comprises: Two reference sources for emitting gamma rays with two different energies are arranged at 180-degree intervals along the circumferential direction outside a pipeline cleaning section, two detectors are arranged at opposite sides of the pipeline and opposite to each reference source, each detector receives rays which come from the opposite side reference source and linearly propagate along the diameter direction of the pipeline, and two transmission count pairs are obtained through measurement; based on the two transmission count pairs, respectively calculating the ratio of the two energy count rates received by each detector, comparing the ratio with an initial calibration ratio, and if the deviation exceeds a preset threshold, reversely correcting the original count rates of the two energies according to the deviation amount to obtain a corrected transmission count pair; The reference source is enabled to work in a pulse mode, the counting rate of the transmission signal and the background signal is obtained at the windowing time through time gating synchronous with the pulse source, the counting rate of the pure background signal is obtained at the windowing time, and the windowing counting rate is subtracted from the windowing counting rate in the same period to obtain the pure transmission attenuation pair.
3. 3. The on-line monitoring method for a gas-liquid two-phase flow of a radioactive separation system of claim 2, wherein inverting the mass thickness of the sediment in the pipe comprises: based on two groups of pure transmission attenuation pairs, respectively constructing attenuation characteristic vectors corresponding to each channel, performing space alignment comparison on the two groups of attenuation characteristic vectors, and reversely deducing the non-uniform distribution form of the sediment in the circumferential direction according to the comparison result; Dividing the cross section of the pipeline into a plurality of microcell areas based on the non-uniform distribution form of the sediment, substituting the parameters of the non-uniform distribution form of each microcell area into a physical constraint equation set based on the attenuation characteristics of two energies in the sediment and the fluid as known quantity, solving to obtain the local mass thickness of each microcell area, and carrying out space integration on all the local mass thicknesses to obtain the total mass thickness of the sediment.
4. 4. The method for online monitoring of a gas-liquid two-phase flow for a radioactive separation system of claim 3, wherein measuring the primary count rate comprises: Based on the circumferential non-uniform distribution morphological parameters of the sediment, adjusting the spatial direction of the detection view field to align the direction with the fluid equivalent center; On the basis of the detection view field aligning to the fluid equivalent center, the photons passing through the view field are screened based on energy-angle collaborative screening, and the screened photons are recorded to form a main counting rate after topological suppression.
5. 5. The method for on-line monitoring of a gas-liquid two-phase flow for a radioactive separation system of claim 4, wherein obtaining a compensated count rate comprises: sorting pulse signals corresponding to the main counting rate after topology inhibition according to amplitude, and constructing counting rates of a plurality of energy channels corresponding to the radionuclide characteristic energy to be detected; Calculating the thickness distribution of the sediment penetrated by rays reaching the detector from the fluid equivalent central area along different directions based on the circumferential non-uniform distribution form of the sediment and the spatial direction of the detection view field, and generating an attenuation correction factor corresponding to each energy channel by combining attenuation coefficients of all characteristic energy acquired in advance in the sediment; And performing preliminary compensation by using the counting rate of each energy channel and the corresponding attenuation correction factor, and then performing self-consistency iterative correction on the counting rate of each energy channel after preliminary compensation according to the branch ratio of each characteristic energy of the radionuclide to be detected, so as to eliminate the influence of scattering crosstalk among channels and obtain each energy counting rate after energy self-consistency correction.
6. 6. The method for on-line monitoring of a gas-liquid two-phase flow for a radioactive separation system of claim 5, wherein the compensated count rate is obtained, further comprising: based on the total mass thickness of the sediment, searching an energy spectrum hardening correction coefficient from a nonlinear mapping relation of the sediment thickness and the energy response, and carrying out secondary correction on each energy counting rate after energy self-consistent correction to obtain each energy counting rate after energy spectrum hardening correction; According to the spatial coverage of the detection view field and the non-uniform distribution form of the sediment, a contribution weight function of different spatial positions in the view field to the detector count is constructed, energy calculation rates after energy spectrum hardening correction are weighted and summed according to energy, and then the sum is divided by the integral of the weight function to the view field area, so that the total compensation count rate of spatial normalization is obtained; inverting the current fluid density by using the pure transmission attenuation, carrying out consistency check on the total spatial normalization compensation counting rate according to the association relation between the fluid density and the radioactive concentration, adjusting the energy spectrum hardening correction coefficient or the corresponding correction coefficient in the contribution weight function if the deviation exceeds a preset threshold value, re-executing the acquisition process of the total spatial normalization compensation counting rate until the deviation is converged in the threshold value, and outputting the checked final compensation counting rate.
7. 7. The online monitoring method for a gas-liquid two-phase flow of a radioactive separation system of claim 6, wherein performing a zero deposit check comprises: triggering zero deposit verification based on the total mass thickness of the deposit being below a preset threshold; in a zero sediment state, measuring the transmissivity of the reference source rays after penetrating through the pipeline and the fluid, obtaining updated clean pipeline transmissivity standard, and inverting the density of the fluid based on the transmissivity; And redirecting the detection view of the main detector to the direction of the reference source, and measuring the counting rate of the rays of the reference source to obtain the measurement counting rate of the main detector on the reference source.
8. 8. The online monitoring method for a gas-liquid two-phase flow of a radioactive separation system of claim 7, wherein performing a zero deposit check further comprises: calculating an attenuation correction coefficient of rays from the reference source to the main detector based on the fluid density and the transmissivity obtained in the zero sediment state in combination with the relative geometric positions of the reference source and the main detector, correcting the counting rate of the main detector on the reference source by using the attenuation correction coefficient, and determining the detection efficiency of the main detector according to the corrected counting rate and the known activity of the reference source; restoring the detection field of view of the main detector to the pipeline axis area, and storing the updated clean pipeline transmissivity reference and the detection efficiency of the main detector.
9. 9. The on-line monitoring method for a gas-liquid two-phase flow of a radioactive separation system of claim 8, wherein calculating the true radioactivity concentration of the flowing fluid comprises: based on the final compensation counting rate and the updated detection efficiency of the main detector, constructing a response matrix and combining and solving by utilizing a detection view field space weight distribution function and a pre-acquired branch ratio to obtain the radioactive concentration after preliminary geometric correction; Inverting to obtain fluid equivalent density based on the radioactive concentration and pure transmission attenuation pair after preliminary geometric correction, calculating expected concentration according to the fluid equivalent density, comparing the radioactive concentration after preliminary geometric correction with the expected concentration, if the deviation exceeds a preset threshold value, adjusting sediment attenuation coefficient used in the attenuation correction factor generation process, iteratively executing the process from the compensated counting rate to the radioactive concentration after preliminary geometric correction calculation until the deviation is converged in the threshold value, and outputting final radioactive concentration; based on the final radioactive concentration, the total mass thickness of the sediment and the circumferential non-uniform distribution form parameters thereof, the concentration change rate and the sediment growth rate are obtained by combining the historical time data, the sediment partial product index is calculated, and the parameters are integrated into a comprehensive state vector and output.
10. 10. The gas-liquid two-phase flow on-line monitoring system for the radioactive separation system is applied to the gas-liquid two-phase flow on-line monitoring method for the radioactive separation system, and is characterized by comprising a transmission measuring module, a transmission attenuation pair and a radiation detection module, wherein the transmission measuring module is used for arranging reference sources for emitting gamma rays with two different energies on the outer side of a cleaning section of a pipeline to be detected, arranging reference source detectors on the opposite sides of the pipeline, and measuring the two energy transmittances of the reference source rays after the reference source rays penetrate through the pipeline, fluid and sediment; the quality inversion module is used for inverting the quality thickness of sediment in the pipeline according to the transmission attenuation pair and the pre-acquired clean pipeline transmittance reference; The main measurement counting module is used for setting a main detector and a narrow view field collimator thereof, so that the detection view field of the main detector is limited to the pipeline axis area, and the main counting rate is obtained through measurement; the counting compensation module is used for compensating the main counting rate by utilizing the mass thickness of the sediment and the attenuation coefficient of the radionuclide to be detected in the sediment, which are acquired in advance, so as to obtain the compensated counting rate; the zero-settlement checking module is used for executing zero-settlement checking at preset time intervals and updating the transmissivity standard of the cleaning pipeline and the detection efficiency of the main detector; And the concentration calculation module is used for calculating the true radioactive concentration of the flowing fluid according to the compensated counting rate and the updated detection efficiency and outputting the mass thickness of the sediment.

Description

Gas-liquid two-phase flow on-line monitoring method and system for radioactive separation system Technical Field The invention relates to the technical field of fluid detection, in particular to a gas-liquid two-phase flow on-line monitoring method and system for a radioactive separation system. Background In the operation process of a radioactive separation system, a fluid medium often presents a gas-liquid two-phase flow state, for example, in links of radiolabeling synthesis, chromatographic separation column elution or waste liquid discharge and the like, in order to ensure the safe and stable operation of the system and ensure the product quality, real-time and accurate online monitoring of the radioactivity concentration in the fluid is required, and the prior online monitoring technology mostly adopts a non-contact type radioactivity detector, such as a gamma detector or a scintillator detector, which is arranged outside a pipeline, and estimates the radioactivity of the fluid by measuring gamma rays or beta rays emitted when the fluid flows through a visual field area of the detector. In practical application, the monitoring method has a remarkable problem that radioactive sediment on the inner wall of a pipeline is interfered, radioactive substances or other matrixes such as salts, organic matters and proteins carried in the fluid have adhesiveness, or the solubility is reduced due to temperature and pressure changes when the fluid flows in the pipeline, the radionuclide easily forms a layer of sediment on the inner wall of the pipeline, and under the working condition of gas-liquid two-phase flow, the fluid state is more complex, the fluctuation of a gas-liquid interface, the change of flow velocity and the generation and collapse of bubbles can aggravate the precipitation and the adhesion of solute on the pipe wall. The sediment layer has the same radioactivity characteristic as that of flowing fluid, namely the same nuclide and similar energy spectrum, but belongs to static attachments, when an online monitoring system measures, a radiation signal received by a detector is actually derived from two parts, namely one part is dynamic radiation of gas-liquid two-phase fluid flowing normally from the center of a pipeline, the other part is static radiation from a pipe wall sediment layer, the two parts are difficult to effectively distinguish from a mixed energy spectrum signal by the existing signal processing technology, the radioactivity reading displayed by the monitoring system is continuously higher due to the existence of the sediment layer, the deviation has accumulation and uncertainty, the thicker the sediment layer is, the more radioactivity is accumulated, the serious the interference on a measurement result is caused, the interference not only causes that an operator cannot acquire the real fluid radioactivity concentration, but also affects process control, such as separation efficiency judgment, product collection opportunity control, and the like, but also can cause erroneous judgment in links such as system cleaning verification, radioactive waste emission monitoring and the like, and cause false positive superscale or emission calculation errors, thereby causing unnecessary compliance problems. Disclosure of Invention Aiming at the problems existing in the prior art, the invention aims to provide the gas-liquid two-phase flow on-line monitoring method and system for the radioactive separation system, which can realize the real-time and high-precision on-line monitoring of the fluid radioactivity concentration under the working condition of the gas-liquid two-phase flow of the radioactive separation system, synchronously acquire the deposit adhesion state parameters, and provide the technical effects of reliable data support for the process control of the system, the cleaning management and control of the pipeline and the compliance judgment of radioactive waste emission. In order to solve the problems, the invention adopts the following technical scheme: In a first aspect, a gas-liquid two-phase flow on-line monitoring method for a radioactive separation system, comprising: a reference source for emitting two gamma rays with different energies is arranged at the outer side of a cleaning section of a pipeline to be tested, a reference source detector is arranged at the opposite side of the pipeline, and the transmittance of the two energies after the reference source rays penetrate through the pipeline, fluid and sediment is measured to obtain a transmission attenuation pair; Inversion is carried out on the basis of the transmission attenuation pair and a pre-acquired clean pipeline transmission reference to obtain the mass thickness of sediment in the pipeline; setting a main detector and a collimator with a narrow view field, so that the detection view field of the main detector is limited to the axis area of the pipeline, and measuring to obtain a main counting rate; Compensating