CN111524620B

CN111524620B - Device and method for simulating tiny gas diffusion and collection at break opening in off-line sipping of fuel assembly

Info

Publication number: CN111524620B
Application number: CN202010336073.3A
Authority: CN
Inventors: 章静; 于启帆; 苏光辉; 秋穗正; 巫英伟; 田文喜
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2020-04-25
Filing date: 2020-04-25
Publication date: 2021-10-19
Anticipated expiration: 2040-04-25
Also published as: CN111524620A

Abstract

A simulation fuel assembly sips the device that the tiny gas diffusion of the cut collects in the suction off line, the device includes an inner cylinder to simulate fuel element, an outer cylinder to simulate water circuit, there is a rod core including simulating fuel element pellet in the inner cylinder, there is tracer gas in the inner cylinder, the outer cylinder contains water and inner cylinder, and the outer cylinder can control the temperature and pressure of the water bath environment; the inner barrel and the outer barrel are provided with the crevasse opening and closing device, so that the pressurized locking of the crevasse, the crevasse opening and the size change of the crevasse can be realized, and the simulation of the offline sipping process of the fuel elements with different damage degrees can be realized.

Description

Device and method for simulating tiny gas diffusion and collection at break opening in off-line sipping of fuel assembly

Technical Field

The invention relates to the field of sipping during reactor shutdown and refueling, in particular to a device and a method for simulating tiny gas diffusion collection at a crevasse in off-line sipping of a fuel assembly.

Background

High temperature and high radiation conditions in nuclear reactors can cause the fuel element cladding to be damaged, and therefore sipping tests are used to perform damage leakage inspection on nuclear fuel assemblies during reactor shutdown and refueling. The sipping test involves isolating the fuel assembly in a defined container, heating the fuel assembly by its own decay heat or by a heater to allow soluble fission products or fission gases to escape, and then taking the sample and analyzing it with a radiation detector.

According to the current reactor operation experience, the sipping devices of the fuel assembly are mainly divided into two types: an online sipping device and an offline sipping device. The on-line sipping device is arranged on a loading and unloading machine of a reactor factory, a semi-closed environment formed when a fuel assembly is lifted to enter an inner barrel of the loading and unloading machine is utilized, compressed air is injected from the bottom of the inner barrel through an air blowing pipe, airflow carries fission gas leaked from a fuel rod to rise to the water surface in the inner barrel, then a water sample or a gas sample in the air flow is extracted, and the integrity of a cladding of the fuel rod is determined by analyzing the level of the fission gas radionuclide. The on-line sipping device has higher environmental requirements for realizing sipping, namely the sipping is completed in the unloading process, and the power for promoting the fission gas 133Xe to be released from the damaged port of the fuel rod is only the height change of the fuel assembly in the reactor core and the refueling water pool, so that the pressure difference inside and outside the rod of the fission gas in the fuel rod is increased.

The off-line sipping device mainly comprises a water loop and an air loop, wherein an on-line gamma spectrometer is arranged on the air loop and is used for continuously detecting the activity of 133 Xe. When the fuel assembly is placed in the sipping chamber, the electric heating source is immediately started to heat water in the loop, when the temperature rises to a specified temperature platform, the heater is closed, the condenser is started, and the stability of the temperature in the sipping chamber is maintained through the combined action of the waste heat of the fuel assembly and the condenser. At this time, the gas or liquid in the fuel rod is released from the breach to the sipping chamber, wherein the fission gas flows to the upper gas space of the sipping chamber along with the compressed air of the gas loop, and thereafter the gas is collected for radioactive measurement. The sipping process of the off-line sipping device has longer time, more stable measuring environment and higher measuring precision.

Disclosure of Invention

The invention aims to design a device for simulating the collection and measurement of micro gas diffusion at the opening of a component in the off-line sipping of a fuel component.

In order to achieve the purpose, the invention adopts the following technical scheme:

a device for simulating micro gas diffusion collection at a breach in off-line sipping of a fuel assembly comprises a rod core 101, an inner barrel 102 and an outer barrel 105, wherein the rod core 101 is used for simulating fuel element pellets, the rod core 101 is placed in the inner barrel 102, and the inner barrel 102 is used for simulating a gas space containing fission gas in a fuel element; a crevasse opening and closing device 103 is arranged on the side surface of the inner cylinder 102 and is used for simulating crevasses of fuel elements; the bottom of the inner cylinder 102 is connected with a gas supply system so as to inject mixed gas mixed with tracer gas into the inner cylinder 102; the inner barrel 102 is arranged in the outer barrel 105, the outer barrel 105 is used for simulating a water loop in an off-line sipping process, water bath environments with different temperatures are provided for the inner barrel, and meanwhile, the top of the outer barrel 105 contains a part of air space; a thermocouple 124 and a pressure gauge 125 are arranged inside the outer cylinder 105, and are respectively used for monitoring the temperature and the pressure of the outer cylinder 105; the gas space above the top cover of the outer cylinder 105 is connected with a top ball valve 111, the bottom is connected with a bottom ball valve 119, and the top ball valve 111 and the bottom ball valve 119 are used for connecting the outer cylinder 105 with a circulating carrier gas loop to form circulating carrier gas of the gas loop.

The crevasse opening and closing device 103 is positioned between the inner cylinder 102 and the outer cylinder 105 and comprises a replaceable crevasse gasket 201, a sealing ring 202, a flexible plug 203, a rotating shaft 204, a locking thread 205 and a crevasse opening and closing operating lever 206; the locking thread 205 is arranged at an opening on the side wall of the outer barrel 105; the tail part of the rotating shaft 204 is inserted into the opening of the side wall of the outer cylinder 105, and when the crevasse opening and closing device 103 is closed, the flexible plug 203 at the head part of the rotating shaft 204 seals the opening of the side wall of the inner cylinder 102 through the replaceable crevasse gasket 201 and the sealing ring 202; the working mode is that the flexible plug 203 at the head of the rotating shaft is driven to compress to realize the under-pressure locking of the crevasses by rotating the crevasse opening and closing operating rod 206 to screw into the locking thread 205, the crevasses are opened by reverse operation, and meanwhile, the crevasse size can be changed by replacing the crevasse gasket 201.

When the device for simulating the collection of the micro gas diffusion at the break port in the off-line sipping of the fuel assembly simulates the measurement of the micro gas diffusion in the off-line sipping process, firstly, the rod core 101 is placed into the inner barrel 102, the inner barrel 102 is placed into the outer barrel 105, then, the break port opening and closing device 103 is closed, and the outer barrel 105 is sealed; heating the water in the outer cylinder 105 to a required temperature T, and then filling a group of preheated mixed gas containing tracer gas into the inner cylinder 102; slowly opening the top ball valve 111, observing the pressure gauge 125 on the outer cylinder 105, and quickly closing the top ball valve 111 when the reading reaches a set pressure value P1; by operating the crevasse opening and closing lever 206, the rotating shaft 204 is rotated to open the crevasse opening and closing device 103, and the outer cylinder 105 is allowed to sufficiently stand in an environment with a pressure of P1; the top ball valve 111 and the bottom ball valve 119 are opened to circulate the carrier gas, and when the pressure reaches the set pressure value P2, the measurement is performed.

Compared with the prior art, the invention has the following advantages:

1. the experimental device for simulating the collection of the micro gas diffusion in the off-line sipping process has a simple structure, can accurately simulate the diffusion and the collection of the off-line sipping under the real condition, and can realize the simulation of more fuel element states and the off-line sipping environment by changing the experimental temperature environment, the pressure environment, the gas ratio and the size of a break port; the whole experimental device has small design scale, high reduction degree in the process of collecting the experimental simulation offline sipping gas, simple and easy operation, and higher safety and economical efficiency.

2. The crevasse opening and closing device provided by the invention realizes opening and closing of the crevasse by external control through the design of the external connecting rod, and simulates diffusion and collection of fission gas in the process of real offline sipping of the fuel rod. The sealing performance of the inner cylinder for simulating the fuel element during inflation and deflation is guaranteed, meanwhile, the replaceable crevasse gasket is adopted, and simulation and measurement work of different crevasse sizes of the fuel element is realized by changing the simulated crevasse size.

In a word, the experimental device for simulating the collection of the micro gas diffusion in the off-line sipping process has the advantages of accurate simulation reduction, stable measurement environment and various measurement working conditions, and can well realize the simulation of the off-line sipping process.

Drawings

FIG. 1 is a schematic diagram of an apparatus for simulating micro gas diffusion collection at a break in an off-line sipping of a fuel assembly according to the present invention.

FIG. 2 is a view of the crevasse opening and closing device of the present invention.

Detailed Description

The invention is described in detail below with reference to the following figures and detailed description:

as shown in fig. 1, the device for simulating micro gas diffusion collection at a breach in off-line sipping of a fuel assembly of the present invention includes a rod core 101, an inner barrel 102 and an outer barrel 105, wherein the rod core 101 is used for simulating fuel element pellets, the rod core 101 is placed in the inner barrel 102, and the inner barrel 102 is used for simulating a gas space containing fission gas inside a fuel element; a crevasse opening and closing device 103 is arranged on the side surface of the inner cylinder 102 and is used for simulating crevasses of fuel elements; the bottom of the inner cylinder 102 is connected with a multipurpose gas system; an outer cylinder 105 of the simulated water circuit, wherein the inner cylinder 102 of the simulated fuel element is placed in the outer cylinder 105, the outer cylinder 105 is used for simulating the water circuit in the off-line sipping process, water bath environments with different temperatures are provided for the inner cylinder 102, and meanwhile, the top of the outer cylinder 105 contains a part of air space; a thermocouple 124 and a pressure gauge 125 are arranged inside the outer cylinder 105, and are respectively used for monitoring the temperature and the pressure of the outer cylinder 105; the gas space above the top cover of the outer drum 105 is connected to a top ball valve 111 and the bottom is connected to a bottom ball valve 119, the top ball valve 111 and the bottom ball valve 119 being used to connect the outer drum 105 to a circulating carrier gas circuit.

As shown in fig. 2, the crevasse opening and closing device is located between the inner cylinder 102 and the outer cylinder 105, and includes a replaceable crevasse gasket 201, a sealing ring 202, a flexible plug 203, a rotating shaft 204, a locking thread 205 and a crevasse opening and closing operating lever 206, and the working mode is that the flexible plug 203 at the head of the rotating shaft is driven to compress to realize the pressurized locking of the crevasse by rotating the crevasse opening and closing operating lever 206 to screw into the locking thread 205, and the crevasse opening and closing device is reversely operated to realize the crevasse opening, and meanwhile, the replaceable crevasse gasket 201 realizes the change of the size of the crevasse.

When the device for simulating the collection of the micro gas diffusion at the break port in the off-line sipping of the fuel assembly simulates the measurement of the micro gas diffusion in the off-line sipping process, firstly, the rod core 101 is placed into the inner barrel 102, the inner barrel 102 is placed into the outer barrel 105, then, the break port opening and closing device 103 is closed, and the outer barrel 105 is sealed; heating the water in the outer cylinder 105 to a required temperature T, and then filling a group of preheated mixed gas containing tracer gas into the inner cylinder 102; slowly opening the ball valve 111, observing the pressure gauge 125 on the outer cylinder 105, and quickly closing the top ball valve 111 when the reading reaches a set pressure value P1; by operating the crevasse opening and closing lever 206, the rotating shaft 204 is rotated to open the crevasse opening and closing device 103, and the outer cylinder 105 is allowed to sufficiently stand in an environment with a pressure of P1; the top ball valve 111 and the bottom ball valve 119 are opened to circulate the carrier gas, and when the pressure reaches the set pressure value P2, the measurement is performed.

While the invention has been described in further detail with reference to specific preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A device for simulating the collection of micro gas diffusion at a breach in off-line sipping of a fuel assembly, comprising: the device comprises a rod core (101), an inner barrel (102) and an outer barrel (105), wherein the rod core (101) is used for simulating pellets of a fuel element, the rod core (101) is placed in the inner barrel (102), and the inner barrel (102) is used for simulating a gas space containing fission gas in the fuel element; a crevasse opening and closing device (103) is arranged on the side surface of the inner cylinder (102) and is used for simulating crevasses of fuel elements; the bottom of the inner cylinder (102) is supplied with gas by a multipurpose gas system and is used for injecting mixed gas mixed with tracer gas into the inner cylinder (102);

an inner barrel (102) is arranged in the outer barrel (105), the outer barrel (105) is used for simulating a water circuit in an off-line sipping process, water bath environments with different temperatures are provided for the inner barrel (102), and meanwhile, the top of the outer barrel (105) contains a part of air space; a thermocouple (124) and a pressure gauge (125) are arranged inside the outer cylinder (105) and are respectively used for monitoring the temperature and the pressure of the outer cylinder (105); the gas space above the top cover of the outer cylinder (105) is connected with the top ball valve (111), the bottom is connected with the bottom ball valve (119) and the check valve (123), and the top ball valve (111) and the bottom ball valve (119) are used for connecting the outer cylinder (105) with a circulating carrier gas loop to form circulating carrier gas of the gas loop.

2. The apparatus of claim 1, wherein the simulated fuel assembly offline sipping comprises a means for collecting micro-gas diffusion at a break-away opening of the simulated fuel assembly, wherein the means for collecting micro-gas diffusion at the break-away opening comprises: the crevasse opening and closing device (103) is positioned at an opening penetrating through the outer cylinder (105) and arranged at the side wall of the inner cylinder (102), and comprises a replaceable crevasse gasket (201), a sealing ring (202), a flexible plug (203), a rotating shaft (204), a locking thread (205) and a crevasse opening and closing operating lever (206); the locking thread (205) is arranged at an opening of the side wall of the outer barrel (105); the tail part of the rotating shaft (204) is inserted into the opening of the side wall of the outer cylinder (105), when the crevasse opening and closing device (103) is closed, the flexible plug (203) at the head part of the rotating shaft (204) seals the opening of the side wall of the inner cylinder (102) through the replaceable crevasse gasket (201) and the sealing ring (202); the flexible plug (203) at the head of the rotating shaft is driven to compress to realize the under-pressure locking of the crevasse by rotating the crevasse opening and closing operating lever (206) and screwing in the locking thread (205), the crevasse opening is realized by reverse operation, and the crevasse size is changed by replacing the crevasse gasket (201).

3. The method of claim 2, wherein said simulating the fuel assembly off-line sipping comprises: when the micro gas diffusion measurement in the off-line sipping process is simulated, firstly, the rod core (101) is placed into the inner barrel (102), the inner barrel (102) is placed into the outer barrel (105), then the crevasse opening and closing device (103) is closed, and the outer barrel (105) is sealed; heating the water in the outer cylinder (105) to a required temperature T, and then filling a group of mixed gas containing tracer gas and preheated into the inner cylinder (102); slowly opening a top ball valve (111), vacuumizing a gas space at the top of the outer cylinder (105) through a vacuum pump in a circulating carrier gas loop connected with the top ball valve (111), observing a pressure gauge (125) on the outer cylinder (105), and quickly closing the top ball valve (111) when the reading reaches a set pressure value P1; by operating the crevasse opening and closing operating lever (206), the rotating shaft (204) is rotated, the crevasse opening and closing device (103) is opened, and the outer cylinder (105) is fully kept still under the environment with the pressure of P1; the top ball valve (111) and the bottom ball valve (119) are opened to circulate the carrier gas, and when the pressure reaches a set pressure value P2, the measurement is carried out.