CN114496321A

CN114496321A - Radioactivity on-line monitoring system of nuclear reactor primary circuit

Info

Publication number: CN114496321A
Application number: CN202210049529.7A
Authority: CN
Inventors: 赵家伟
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-01-17
Filing date: 2022-01-17
Publication date: 2022-05-13

Abstract

The invention relates to the technical field of radioactivity online monitoring, in particular to a radioactivity online monitoring system of a nuclear reactor primary circuit, which is used for online monitoring of fuel element breakage. The device structurally comprises an object to be detected, wherein a loop pipeline is arranged in the object to be detected, a main detector and a spectrum analyzer are arranged on the outer side of the loop pipeline, the main detector adopts a high-purity germanium detector, the main detector and the spectrum analyzer are electrically connected with a workstation, the workstation is used for performing energy spectrum analysis and online diagnosis of a fuel cladding damage state, and an electromagnetic valve and a flow control valve are arranged on the loop pipeline. The invention discloses an on-line radioactivity monitoring system of a nuclear reactor primary circuit, which solves the problems of complex source items and strong interference rays in the on-line measurement of the primary circuit, greatly improves the measurement precision and detection limit of fission product nuclide, and finally reaches or even exceeds the detection level of off-line sampling measurement.

Description

Radioactivity on-line monitoring system of nuclear reactor primary circuit

Technical Field

The invention relates to the technical field of radioactivity online monitoring, in particular to a radioactivity online monitoring system of a nuclear reactor primary circuit, which is used for online monitoring of fuel element breakage.

Background

At present, in the field of nuclear power or nuclear power, a radioactivity monitoring system (KRT) in a nuclear island region adopts various technical means and facilities to take on-line monitoring measures on various radioactivity of a primary circuit, a plant, a steam generating device and even a drainage pipeline, and provides systematic safety guarantee for the safe operation of a nuclear reactor.

The reactor core generates huge heat energy due to fission of nuclear fuel, water pumped into the reactor core by a main pump is heated into high-temperature high-pressure water with 327 ℃ and 155 atmospheric pressures, the high-temperature high-pressure water flows through a heat transfer U-shaped pipe in the steam generator, the heat energy is transferred to two-loop cooling water outside the U-shaped pipe through a pipe wall, and the high-temperature high-pressure water is returned to the reactor core by the main pump after releasing the heat energy and is reheated and then enters the steam generator. The water thus continuously circulates in a closed circuit, referred to as a circuit.

In order to monitor the damage condition of the fuel element, an on-line energy spectrum measuring technology is adopted for a loop pipeline, however, a commonly adopted detector is either NaI (sodium iodide detector) or LaBr (lanthanum bromide detector), the energy resolution is low, and the activity of a key nuclide cannot be accurately measured.

In recent years, a measurement system adopting an HPGe (high purity germanium) detector has appeared, so that the measurement accuracy and the detection limit are greatly improved, but due to the particularity of a measurement object, for example, a strong corrosion activation product exists on the inner wall, or a high-energy activation product with an extreme service life exists, so that the energy spectrum is seriously interfered, the measurement of the activity of a fission product is seriously influenced, and the detection limit of each nuclide is far inferior to the measurement level of off-line sampling, so that the measurement effect is restricted.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides an on-line radioactivity monitoring system of a nuclear reactor primary circuit, which solves the problems of complex source items and strong interference rays in the on-line measurement of the primary circuit, greatly improves the measurement precision and detection limit of fission product nuclide, and finally reaches or even exceeds the detection level of off-line sampling measurement.

The technical scheme adopted by the invention is as follows:

the system comprises an object to be detected, wherein a loop pipeline is arranged in the object to be detected, a main detector and a spectrum analyzer are arranged outside the loop pipeline, the main detector adopts a high-purity germanium detector, the main detector and the spectrum analyzer are electrically connected with a workstation, the workstation is used for performing energy spectrum analysis and online diagnosis of a fuel cladding damage state, and an electromagnetic valve and a flow control valve are arranged on the loop pipeline.

Preferably, the object to be measured is a pipe to be measured or a container to be measured.

Preferably, an anti-well-being ring detector is arranged beside the main detector.

Preferably, the main detector and the anti-resonant ring detector are laterally provided with shielding devices.

Preferably, the solenoid valve is a remotely controllable solenoid valve.

Preferably, a slit mechanism is provided between the outside of the primary loop pipe and the primary probe.

Preferably, the object to be measured is a container to be measured, and a coating is arranged on the inner surface of the container to be measured.

Preferably, the object to be measured is a pipeline to be measured, and a lining pipe is arranged inside the pipeline to be measured.

Preferably, the coating is gold plating, platinum plating, silver plating or high polymer material coating.

The invention relates to a radioactivity online monitoring system of a nuclear reactor primary circuit, which firstly reduces interfering nuclides from the source, and the method is to carry out special treatment on the inner wall of a container, so that corrosion activation products are not easy to attach. The specific method can be gold plating, silver, platinum and other substances with the best chemical stability on the inner surface of the metal, and can also be coated with high polymer materials with good stability, even a sleeve is additionally arranged inside the sleeve.

Secondly, the purpose of reducing interference is achieved by prolonging the arrival time of water. By reasonably designing the pipe diameter, the length of the pipeline and the flow velocity, the time for water to flow from the reactor core to a measuring position is adjusted to 3-5 minutes, and N-16 can be basically eliminated, so that the aim of reducing the background is fulfilled.

In addition to reducing interference, the effect can be amplified. By adopting the diameter changing method, the pipeline is enlarged, the detection efficiency can be effectively improved, and the detection limit is directly improved.

Efficiency is improved and is fit for the measurement of low radioactivity, and under the special circumstances, the radioactivity probably improves a lot in a return circuit, in order to control the dead time of system at reasonable within range, set up slit mechanism between water sample and detector, adopt two high atomic number materials that can relative movement, place on step motor driven forward and reverse tooth lead screw, measure under wide-open and different width slit modes, can expand the activity measurement range greatly.

Since the lowest energy gamma rays in the key nuclear species of interest are as low as 81keV, stainless steel tube walls above 2 mm absorb more than half. In order to reduce absorption, the pipe wall material is replaced by aluminum alloy or carbon fiber composite material, and the low-energy region detection efficiency can be effectively improved after modification.

And in the occasion of slight environmental interference, an anti-health ring detector can be adopted. The anti-healthy ring detector is arranged around the main detector, and NaI, BGO or plastic scintillators and other detectors are adopted to be matched with an anti-coincidence electronic circuit or a digital signal processing system, so that the background of an energy spectrum is further reduced, and the measurement precision and the detection limit are improved.

A high atomic number shielding material of sufficient thickness is required to be disposed on the side of the detector so as to reduce the interference of ambient rays as much as possible.

The technical scheme provided by the invention has the beneficial effects that:

according to the mechanism and the principle that part of fission gas and volatile fission products are released into a primary circuit coolant after a fuel rod cladding is damaged, the integrity of the fuel rod cladding is monitored by online measurement and analysis of the types and the activity of the fission products released into the primary circuit coolant, and the damage property is evaluated when the fuel rod is damaged.

The nuclear reactor primary circuit radioactivity online monitoring system can continuously measure the activity of various radioactive nuclides in a primary circuit coolant of a pressurized water reactor in real time and monitor the damage condition of fuel rods online; when the abnormal condition appears, whether the fuel rod is damaged or not is judged at the first time, and meanwhile, after the damage of the fuel rod is confirmed, the damage trend is continuously monitored in real time and displayed on line, technical decision data are provided for continuous operation of the nuclear reactor, and the chemical sampling workload and the integral dosage burden are reduced. Compared with the traditional method for manually taking a loop water sample to measure the activity of fission products and monitoring fuel damage of a nuclear reactor, the on-line monitoring intelligent system is a more rapid, complete and safe fuel rod damage monitoring and analyzing means.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a system schematic diagram of a radioactivity online monitoring system of a primary circuit of a nuclear reactor according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example one

As shown in fig. 1, the system for online monitoring radioactivity of a nuclear reactor primary circuit of the present embodiment includes an object to be measured 1, a primary circuit pipeline 2 is disposed in the object to be measured 1, a main detector 3 and a spectrum analyzer 4 are disposed outside the primary circuit pipeline 2, the main detector 3 employs a high purity germanium detector, the main detector 3 and the spectrum analyzer 4 are electrically connected to a workstation 5, the workstation 5 is used for performing energy spectrum analysis and online diagnosis of a damaged state of a fuel cladding, and an electromagnetic valve and a flow control valve are disposed on the primary circuit pipeline.

In this embodiment, the object to be measured is a container to be measured, and a coating is disposed on an inner surface of the container to be measured.

The coating can be gold plating, silver, platinum and other substances with the best chemical stability on the inner surface of the metal, and can also be coated with high polymer materials with good stability.

Example two

In this embodiment, an anti-healthy ring detector is arranged beside the main detector, and the detectors such as NaI, BGO, or plastic scintillator are adopted, and in cooperation with an anti-coincidence electronic circuit or a digital signal processing system, the background of the energy spectrum is further reduced, and the measurement accuracy and the detection limit are improved.

EXAMPLE III

The difference between this embodiment and the first and second embodiments is that shielding devices are arranged on the sides of the main detector and the anti-resonant ring detector so as to reduce the interference of ambient rays as much as possible.

Example four

The difference between this embodiment and the first embodiment is that the solenoid valve is a remotely controllable solenoid valve, which adds an off-line measurement capability to the measurement device and improves the measurement accuracy or detection limit for long-life nuclides.

EXAMPLE five

The difference between the present embodiment and the first embodiment is that a slit mechanism is provided between the outside of the loop pipe and the main probe. The slit mechanism is made of a high atomic number material and is arranged on a slide block driven by a stepping motor, so that the detection efficiency is properly reduced when the activity is too high after a loop has a specific event, and the normal work of a measurement system is ensured.

Example six

The difference between this embodiment and the first embodiment is that the object to be measured is a pipe to be measured, and a lining pipe is disposed inside the pipe to be measured.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. The system is characterized in that a main detector and a spectrum analyzer are arranged outside the loop pipeline, the main detector adopts a high-purity germanium detector, the main detector and the spectrum analyzer are electrically connected with a workstation, the workstation is used for performing energy spectrum analysis and online diagnosis of a damaged state of a fuel cladding, and an electromagnetic valve and a flow control valve are arranged on the loop pipeline.

2. An on-line radioactivity monitoring system of a primary loop of a nuclear reactor as claimed in claim 1, wherein the object to be measured is a pipe or a container to be measured.

3. An on-line radioactivity monitoring system of a loop of a nuclear reactor as claimed in claim 1, wherein a reactive loop detector is disposed adjacent to said primary detector.

4. An on-line radioactivity monitoring system of a loop of a nuclear reactor as claimed in claim 3, wherein the main detector and the anti-health loop detector are laterally provided with shielding devices.

5. An on-line radioactivity monitoring system of a primary circuit of a nuclear reactor as claimed in claim 1, wherein said solenoid valve is a remotely controllable solenoid valve.

6. An on-line radioactivity monitoring system in a primary loop of a nuclear reactor as claimed in claim 1, wherein a slit mechanism is provided between the outside of the primary loop and the primary detector.

7. An on-line radioactivity monitoring system of a primary loop of a nuclear reactor as claimed in claim 1, wherein the object to be tested is a container to be tested, and a coating is provided on an inner surface of the container to be tested.

8. An on-line radioactivity monitoring system of a primary loop of a nuclear reactor as claimed in claim 1, wherein said object to be tested is a pipe to be tested, and a lining pipe is disposed inside said pipe to be tested.

9. An on-line radioactivity monitoring system of a primary loop of a nuclear reactor as claimed in claim 7, wherein said coating is gold, platinum, silver or polymer coating.