CN115295178A - MOX fuel rod assembling method - Google Patents

MOX fuel rod assembling method Download PDF

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Publication number
CN115295178A
CN115295178A CN202210877423.6A CN202210877423A CN115295178A CN 115295178 A CN115295178 A CN 115295178A CN 202210877423 A CN202210877423 A CN 202210877423A CN 115295178 A CN115295178 A CN 115295178A
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CN
China
Prior art keywords
fuel rod
mox
pellets
cladding tube
length
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202210877423.6A
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Chinese (zh)
Inventor
田志强
屠振华
王军平
王良清
马绍州
李兵
于永龙
王树涛
王景
王宇飞
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404 Co Ltd China National Nuclear Corp
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404 Co Ltd China National Nuclear Corp
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Publication date
Application filed by 404 Co Ltd China National Nuclear Corp filed Critical 404 Co Ltd China National Nuclear Corp
Priority to CN202210877423.6A priority Critical patent/CN115295178A/en
Publication of CN115295178A publication Critical patent/CN115295178A/en
Pending legal-status Critical Current

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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
    • G21C3/30—Assemblies of a number of fuel elements in the form of a rigid unit
    • G21C3/32—Bundles of parallel pin-, rod-, or tube-shaped fuel elements
    • G21C3/326—Bundles of parallel pin-, rod-, or tube-shaped fuel elements comprising fuel elements of different composition; comprising, in addition to the fuel elements, other pin-, rod-, or tube-shaped elements, e.g. control rods, grid support rods, fertile rods, poison rods or dummy rods
    • G21C3/3262—Enrichment distribution in zones
    • G21C3/3267—Axial distribution
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
    • G21C3/30—Assemblies of a number of fuel elements in the form of a rigid unit
    • G21C3/32—Bundles of parallel pin-, rod-, or tube-shaped fuel elements
    • G21C3/33—Supporting or hanging of elements in the bundle; Means forming part of the bundle for inserting it into, or removing it from, the core; Means for coupling adjacent bundles
    • G21C3/331—Comprising hold-down means, e.g. springs
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
    • G21C3/30—Assemblies of a number of fuel elements in the form of a rigid unit
    • G21C3/32—Bundles of parallel pin-, rod-, or tube-shaped fuel elements
    • G21C3/334—Assembling, maintenance or repair of the bundles
    • 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

The invention relates to the technical field of nuclear fuel element manufacturing, and particularly discloses an MOX fuel rod assembling method, which comprises the following steps: step 1: assembling the cladding tube with the lower end plug; step 2: lower axial transition region UO 2 Loading the pellets into a tube; and step 3: loading tubes to the active area MOX pellets; and 4, step 4: upper axial transition region UO 2 Loading the pellets into a tube; and 5: and sealing the fuel rod. The method realizes the assembly of various pellets in the fuel rod, and meets the requirements of ensuring the total length of the pellet column and the UO in the lower conversion region in the MOX fuel rod 2 Length of the pellet column and quality of the active area MOX pellet column.

Description

MOX fuel rod assembling method
Technical Field
The invention belongs to the technical field of nuclear fuel element manufacturing, and particularly relates to an MOX fuel rod assembling method.
Background
The MOX fuel rod consists of an upper end plug, a compression spring, a cladding tube and an inner pellet (UO) 2 Core block and MOX core block) and a lower end plug. The cladding tube and the upper and lower end plugs are welded to form a sealed cavity, and a core block and a compression spring are accommodated in the cavity, as shown in fig. 1.
The MOX fuel assembly is different from the pressurized water reactor fuel assembly, and the assembly process of the fuel rod is greatly different from that of the pressurized water reactor fuel rod due to the high radioactivity and biological toxicity of the MOX fuel. The traditional fuel rod of pressurized water reactor is only provided with UO inside 2 Pellets, and a fuel assembly, generally only contains fuel pellets of one size, the tube loading process only requires the total length of the pellet column to be loaded, and the fuel rod assembly process is generally performed in an open space due to the low activity of the fuel pellets.
The pellets in the MOX fuel rod are generally provided with two types, one type is MOX pellets, and the other type is UO 2 And (3) a core block. Inside the MOX fuel rod, pellet column distribution space is divided into three sections: an upper axial conversion region, an active region, a lower axial conversion region, and a UO mounted between the upper axial conversion region and the lower axial conversion region 2 And (3) loading the MOX pellets in the middle active section, wherein the tube loading process of the MOX pellets is completely carried out in a closed glove box. In addition, the length of the pellet column in the MOX fuel rod (including the lengths of the pellet columns in the upper and lower conversion regions and the length of the pellet column in the active region) is specified, and the length of the pellet column in the lower conversion region and the mass of the pellet column in the active region are also specified, so that the tube loading process of pellets in the MOX fuel rod is complex.
In addition, due to UO 2 Material properties of core block, assembling processThe method does not cause contamination to the fuel rod in general, and does not cause alpha contamination on the surface of the fuel rod beyond the technical standard. The MOX pellets are rich in uranium 235 and plutonium 239 which are two elements with high radioactivity and high biotoxicity, the tube loading process is carried out in a sealed glove box with high aerosol and dust, and alpha pollution on the surface of the fuel rod is easily caused by the pellets in the tube loading process to exceed the technical conditions, so that the surface decontamination of the fuel rod is required after the fuel rod is assembled.
In summary, the assembling method of the MOX fuel rod is different from the assembling method of the existing pressurized water reactor fuel rod, and a new assembling method of the MOX fuel rod is needed.
Disclosure of Invention
The invention aims to provide an MOX fuel rod assembling method which meets the requirement of a fuel rod for tubulation.
The technical scheme of the invention is as follows:
a MOX fuel rod assembly method comprising the steps of:
step 1: assembling the cladding tube with the lower end plug;
step 2: lower axial transition region UO 2 Loading the pellets into a tube;
and step 3: loading tubes to the active area MOX pellets;
and 4, step 4: upper axial transition region UO 2 Loading the pellets into a tube;
and 5: and sealing the fuel rod.
And 6, decontaminating the surface of the fuel rod to remove alpha contamination on the surface of the fuel rod.
And 6, fully wetting gauze by using a decontamination solution of high-purity alcohol or petroleum sulfonic acid or a mixture of the high-purity alcohol and the petroleum sulfonic acid, and wiping the surface of the fuel rod by using the gauze so as to remove alpha pollution on the surface.
In the step 1, nondestructive detection is carried out on the cladding tube, and the cladding tube qualified in detection is welded with the lower end plug.
The nondestructive testing method is visual or eddy current testing.
In step 2, UO is introduced into a closed glove box 2 The core blocks are poured out of the container and are arranged in a row, and the core block column assembly in the lower axial conversion area specified by the technical requirements is measuredUO of length a 2 Core block, then a length of the above core block is loaded into the cladding tube.
In the step 3, pouring the MOX pellets out of the container in a closed glove box, weighing the MOX pellets with the mass m specified by the technical requirement, then arranging the weighed MOX pellets into a row, and measuring the length of the MOX pellets as b; finally, the above pellets of length b are loaded into the cladding tube.
In the step 4, the total length of the pellet column in the MOX fuel rod specified by the technical requirements is recorded as d, and the axial conversion area UO is calculated 2 Length of the pellet column c, c = d-lower axial transition UO 2 Length of pellet column-length of active area MOX pellet column;
then from the UO 2 Pouring out a certain amount of UO from pellet container 2 Core blocks arranged in a row, measuring UO with length of c 2 Core block, c length of the above core block is loaded into the cladding tube.
Step 5, loading a compression spring into the cladding tube to fully contact with the pellet columns, thereby compressing the three sections of pellet columns to ensure that the pellets are in a tightly attached state in the fuel rod;
and then pressing the upper end plug into the cladding tube, and welding and sealing the upper end plug and the cladding tube.
And welding and sealing the upper end plug and the cladding tube or welding and assembling the cladding tube and the lower end plug in an argon arc welding or pressure resistance welding mode.
The invention has the remarkable effects that:
(1) The method realizes the assembly of various pellets in the fuel rod, and meets the requirements of ensuring the total length of the pellet column and ensuring the UO in the lower conversion region in the MOX fuel rod 2 Length of the pellet column and quality of the active area MOX pellet column.
(2) The method provided by the invention aims at the problem that alpha pollution is easily caused to the surface of the fuel rod in the MOX fuel rod assembling process, provides a decontamination method, and improves the safety of the fuel rod.
(3) The method is experimentally applied to the first MOX fuel assembly experiment line in China, and the qualified MOX fuel rods and MOX fuel testing assemblies are developed, so that the method plays an important role in supplying materials to the fast reactor of the China experiment and ensuring the engineering research of the fast reactor of the China experiment.
Drawings
FIG. 1 is a schematic of a MOX fuel rod structure.
In the figure: 1-an upper end plug; 2-a compression spring; 3-upper axial transition region UO 2 A pellet column; 4-a cladding tube; 5-active zone MOX pellet column; 6-lower axial transition region UO 2 A pellet column; 7-lower end plug.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
A MOX fuel rod assembly method comprising the steps of:
step 1: assembly of cladding tube and lower end plug
Performing nondestructive detection on the cladding tube by using nondestructive detection methods such as visual inspection or eddy current and the like, and welding the cladding tube qualified in detection and the lower end plug in modes such as argon arc welding or pressure resistance welding;
step 2: lower axial transition region UO 2 Pellet tubulation
In a closed glove box, the UO is put in 2 The core blocks are poured out of the container and arranged in a row, and the UO of the total length a of the core block column in the lower axial conversion area specified by the technical requirement is measured by a steel plate ruler 2 A core block, and then the core block with the length of a is loaded into a cladding tube;
and step 3: active area MOX pellet tubulation
Pouring the MOX pellets out of the container in a closed glove box, weighing the MOX pellets with mass m specified by technical requirements by using a balance or other measuring tools, then arranging the weighed MOX pellets into a row, and measuring the length of the MOX pellets by using a steel plate ruler, wherein the length is marked as b; finally, the core blocks with the length of b are filled into a cladding tube;
and 4, step 4: upper axial transition region UO 2 Pellet tubulation
MOX pellet column containing active area, upper axial conversion area UO specified by technical requirements 2 Pellet column, lower axial conversion region UO 2 The total length of the pellet column in the MOX fuel rod of the pellet column is marked as d, and the upper axial conversion area UO is calculated according to the following formula 2 Length of pellet column c, c = d-a-b;
then from the UO 2 Pouring out a certain amount of UO from pellet container 2 Core blocks arranged in a row, measuring UO with length of c by steel plate ruler 2 A core block, wherein the core block with the length of c is arranged in the cladding tube;
and 5: fuel rod seal
A compression spring is arranged in the cladding tube and is fully contacted with the pellet columns, so that the three sections of pellet columns with the lengths of a, b and c are compressed, and the pellets are ensured to be in a tightly attached state in the fuel rod;
then pressing the upper end plug into the cladding tube, and welding and sealing the upper end plug and the cladding tube in an argon arc welding or pressure resistance welding mode;
step 6: decontamination of fuel rod surfaces
Fully wetting gauze by using high-purity alcohol or petroleum sulfonic acid or a mixed decontamination solution of the high-purity alcohol and the petroleum sulfonic acid, and wiping the surface of the fuel rod by using the gauze so as to remove alpha pollution on the surface;
the volume ratio of the high-purity alcohol to the petroleum sulfonic acid is 1: (0.3-5).
Examples
This example used an experimental fast reactor MOX fuel rod cladding tube, upper end plug, lower end plug, hold-down spring, MOX pellets, UO 2 Pellet, comprising the following steps:
step 1: assembly of cladding tube and lower end plug
Respectively carrying out visual detection on the cladding tube and the lower end plug, pressing the lower end plug into one end of Bao Keguan on the basis of qualification, and realizing the welding of the cladding tube and the lower end plug in a non-consumable electrode argon arc welding (TIG) mode;
step 2: lower axial transition region UO 2 Pellet tubulation
Transferring the assembly weldment of the cladding tube and the lower end plug into a glove box with shielding capacity, and enabling the UO to be in contact with the glove box 2 The core blocks are poured out of the container and are arranged in a row, and the UO with the total length of the core block column of 250mm in the lower axial conversion area specified by the technical requirement is measured by a steel plate ruler 2 Core block, then 250mm length of UO 2 The core block is loaded into the cladding tube；
And 3, step 3: active area MOX pellet tubulation
Pouring the MOX pellets out of the container in a closed glove box, weighing the MOX pellets with the mass of 82g specified by technical requirements by a balance or other measuring tools, then arranging the weighed MOX pellets into a row, measuring the length of the MOX pellets by a steel plate ruler, wherein the measured value is 460mm, and filling the MOX pellets with the length of 460mm into a cladding tube;
and 4, step 4: upper axial transition region UO 2 Pellet tubulation
Pellet column (including MOX pellet column and upper and lower axial conversion region UO) in MOX fuel rod specified by fuel rod technical requirements 2 Pellet column) has a total length of 800mm, and the upper axial conversion area UO is calculated 2 The length of the pellet column is 800-250-460=90mm; then from the UO 2 Pouring out a certain amount of UO from pellet container 2 The core blocks are arranged in a row, and the UO with the length of 90mm is measured by a steel plate ruler 2 A core block, the core block with the length of 90mm is loaded into a cladding tube;
and 5: fuel rod seal
The pressing spring is arranged in the cladding tube and is fully contacted with the pellet columns, so that the three sections of pellet columns are pressed tightly to ensure that the pellets are in a tightly attached state in the fuel rod;
then the upper end plug is pressed into the cladding tube, and the upper end plug and the cladding tube are welded and sealed in a non-melting electrode argon arc welding mode, so that the total length of the pellet column, the length of the pellet column in a lower axial conversion area and the quality of the MOX pellet column in an active area are ensured;
step 6: decontamination of fuel rod surfaces
Wiping the surface of the fuel rod with gauze wetted with petroleum sulfonic acid three times, wiping the surface of the fuel rod with gauze wetted with high-purity alcohol three times, and measuring that the alpha pollution on the surface of the fuel rod is reduced to 0.4Bq/cm 2 The index of (2) is as follows.
While there have been shown and described what are at present considered the fundamental principles of the invention, its essential features and advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof.
The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims (10)

1. A MOX fuel rod assembly method, characterized by: the method comprises the following steps:
step 1: assembling the cladding tube with the lower end plug;
step 2: lower axial transition region UO 2 Loading the pellets into a pipe;
and step 3: loading the active area MOX pellets into a tube;
and 4, step 4: upper axial transition region UO 2 Loading the pellets into a tube;
and 5: and sealing the fuel rod.
2. The MOX fuel rod assembly method of claim 1 wherein: and 6, decontaminating the surface of the fuel rod to remove alpha contamination on the surface of the fuel rod.
3. The MOX fuel rod assembly method of claim 2 wherein: in step 6, fully wetting gauze by using high-purity alcohol or petroleum sulfonic acid or a detergent mixed with the high-purity alcohol or the petroleum sulfonic acid, and wiping the surface of the fuel rod by using the gauze so as to remove alpha pollution on the surface.
4. The MOX fuel rod assembly method of claim 1 wherein: in the step 1, nondestructive detection is carried out on the cladding tube, and the cladding tube qualified in detection is welded with the lower end plug.
5. The MOX fuel rod assembly method of claim 4 wherein: the nondestructive testing method is visual or eddy current testing.
6. The MOX fuel rod assembly method of claim 1 wherein: in step 2, UO is introduced into a closed glove box 2 The pellets are poured out of the container and aligned in a row, and the UO of the total length a of the pellet column in the lower axial conversion region specified by the technical requirements is measured 2 Core block, then a length of the above core block is loaded into the cladding tube.
7. The MOX fuel rod assembly method of claim 1, wherein: step 3, pouring the MOX pellets out of the container in a closed glove box, weighing the MOX pellets with mass m specified by technical requirements, then arranging the weighed MOX pellets into a row, and measuring the length of the row as b; finally, the above pellets of length b are loaded into the cladding tube.
8. The MOX fuel rod assembly method of claim 1 wherein: in step 4, the total length of the pellet column in the MOX fuel rod specified by the technical requirements is recorded as d, and a calculation axial conversion area UO is calculated 2 Length of the pellet column c, c = d-lower axial transition UO 2 Length of pellet column-length of active area MOX pellet column;
then from the UO 2 Pouring out a certain amount of UO from the pellet container 2 Core blocks arranged in a row, measuring UO with length of c 2 And (3) a core block, and c length of the core block is loaded into the cladding tube.
9. The MOX fuel rod assembly method of claim 1 wherein: step 5, a compression spring is installed into the cladding tube to be in full contact with the pellet columns, so that the three sections of pellet columns are compressed to ensure that the pellets are in a close fit state in the fuel rod;
and then pressing the upper end plug into the cladding tube, and welding and sealing the upper end plug and the cladding tube.
10. The MOX fuel rod assembly method of claim 9, wherein: and welding and sealing the upper end plug and the cladding tube or welding and assembling the cladding tube and the lower end plug in an argon arc welding or pressure resistance welding mode.
CN202210877423.6A 2022-07-25 2022-07-25 MOX fuel rod assembling method Pending CN115295178A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210877423.6A CN115295178A (en) 2022-07-25 2022-07-25 MOX fuel rod assembling method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210877423.6A CN115295178A (en) 2022-07-25 2022-07-25 MOX fuel rod assembling method

Publications (1)

Publication Number Publication Date
CN115295178A true CN115295178A (en) 2022-11-04

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Country Status (1)

Country Link
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