CN-117993184-B - Oxygen concentration interval checking method

CN117993184BCN 117993184 BCN117993184 BCN 117993184BCN-117993184-B

Abstract

The invention provides an oxygen concentration interval checking method, which relates to the technical field of lead bismuth fast reactor oxygen concentration interval checking, and comprises the steps of establishing a lead bismuth fast reactor model, acquiring an initial oxygen concentration interval of the lead bismuth fast reactor model, and selecting a plurality of preset oxygen concentrations from the initial oxygen concentration interval; the method comprises the steps of carrying out physical field calculation on a fuel rod under each preset oxygen concentration to obtain physical field parameters corresponding to each preset oxygen concentration, wherein the physical field parameters comprise temperature distribution parameters, fuel rod geometric parameters, contact stress, cladding oxidation corrosion parameters and fission gas parameters, judging whether each preset oxygen concentration meets the use requirement of the fuel rod based on the physical field parameters corresponding to each preset oxygen concentration, and determining a qualified oxygen concentration interval based on each preset oxygen concentration meeting the use requirement of the fuel rod. The method and the device can obtain the qualified oxygen concentration interval by checking the initial oxygen concentration interval, and can avoid the problems that heat transfer is deteriorated, corrosion cannot be inhibited and long-term use of the fuel rod cannot be satisfied when the fuel rod is burnt.

Inventors

HE HUI
WANG SHIWEI
LIU XIAOJING
Chai xiang
ZHANG TENGFEI
CHEN JIAJIE

Assignees

上海交通大学

Dates

Publication Date: 20260508
Application Date: 20240122

Claims (9)

1. An oxygen concentration interval checking method is characterized by comprising the following steps: Establishing a lead-bismuth fast reactor model, obtaining an initial oxygen concentration interval of the lead-bismuth fast reactor model, and selecting a plurality of preset oxygen concentrations from the initial oxygen concentration interval, wherein the lead-bismuth fast reactor model comprises a fuel rod and a liquid lead-bismuth alloy, and the fuel rod comprises a pellet and a cladding; Performing physical field calculation on the fuel rod under each preset oxygen concentration to obtain physical field parameters corresponding to each preset oxygen concentration, wherein the physical field parameters comprise temperature distribution parameters, fuel rod geometric parameters, contact stress, cladding oxidation corrosion parameters and fission gas parameters; judging whether each preset oxygen concentration meets the use requirement of the fuel rod based on the physical field parameter corresponding to each preset oxygen concentration, and determining a qualified oxygen concentration interval based on each preset oxygen concentration meeting the use requirement of the fuel rod; the step of calculating the physical field of the fuel rod under each preset oxygen concentration to obtain physical field parameters comprises the following steps: Carrying out neutron physical field calculation on the fuel rod under the preset oxygen concentration to obtain neutron physical field parameters, wherein the neutron physical field parameters comprise radial neutron flux density, axial neutron flux density, nuclear concentration and volumetric heat release rate; Dividing the fuel rod into a plurality of sections along the axial direction, calculating radial neutron flux density section by section through a one-dimensional single group diffusion equation, , Wherein, the For neutron flux density at radius r, I and K are the first and second types of modified bessel functions, respectively, the indices 0 and 1 represent the order of the function, Is the radius of the inner side of the core block, The reciprocal of the neutron diffusion length, C is a constant; Multiplying the radial neutron flux density by an axial power factor to obtain an axial neutron flux density; the burnup equation is calculated to obtain the nuclear concentration, , Wherein, the The radial coordinate r is the nuclear concentration with the mass number equal to j, j is the mass number of any nuclide in six nuclides of 235U, 238U, 239Pu, 240Pu, 241Pu or 242Pu, For an average concentration of particles of mass number equal to j in the pellet, f (r) is the distribution function of plutonium, a is a constant coefficient, Is the absorption interface of a nucleus with a mass number equal to j, For a total interface of nuclei with a mass number equal to j, Is the increment of the burnup depth; The two-dimensional distribution function of the volumetric heat release rate based on the radial neutron flux density, the axial neutron flux density and the nuclear concentration is: , Wherein, the As a two-dimensional distribution function of the volumetric heat release rate, Is a constant coefficient of the power supply, For a concentration of nuclei with a mass number equal to j, The fissile section of the nuclide with the mass number j is the mass number of any nuclide in six nuclides of 235U, 238U, 239Pu, 240Pu, 241Pu or 242Pu, (R) is the neutron flux density at radius r, Is the axial neutron flux density at an axial height z.
2. The oxygen concentration interval checking method according to claim 1, wherein the step of acquiring the initial oxygen concentration interval of the lead bismuth fast reactor model includes: obtaining a lower limit value of the initial oxygen concentration interval according to the oxygen concentration when an oxide layer is stably generated and accumulated on the surface of the cladding of the fuel rod; and obtaining the oxygen concentration of the fuel rod when no oxide is precipitated in the liquid lead bismuth alloy, and obtaining the upper limit value of the initial oxygen concentration interval.
3. The oxygen concentration interval check method according to claim 1, wherein the step of determining whether each preset oxygen concentration satisfies the use requirement of the fuel rod based on the physical field parameter corresponding to each preset oxygen concentration includes: Judging whether each physical field parameter corresponding to the preset oxygen concentration is within a safety limit value corresponding to the physical field parameter; If each physical field parameter is within the corresponding safety limit value, determining that the preset oxygen concentration meets the use requirement of the fuel rod; if one or more parameters in the physical field parameters are not within the corresponding safety limit values, determining that the preset oxygen concentration does not meet the use requirement of the fuel rod.
4. The oxygen concentration interval check method according to claim 1, characterized in that the step of determining a qualified oxygen concentration interval based on each preset oxygen concentration that satisfies the use requirement of the fuel rod includes: obtaining each preset oxygen concentration which meets the use requirement of the fuel rod in the initial oxygen concentration interval, and obtaining a qualified oxygen concentration interval, wherein each oxygen concentration in the qualified oxygen concentration interval meets the use requirement of the fuel rod.
5. The oxygen concentration interval check method according to claim 1, characterized in that the step of determining a qualified oxygen concentration interval based on each preset oxygen concentration that satisfies the use requirement of the fuel rod includes: Obtaining each preset oxygen concentration which is continuously adjacent and does not meet the use requirement of the fuel rod in the initial oxygen concentration interval, obtaining an unqualified oxygen concentration interval, and removing the unqualified oxygen concentration interval in the initial oxygen concentration interval to obtain a qualified oxygen concentration interval, wherein each oxygen concentration in the qualified oxygen concentration interval meets the use requirement of the fuel rod.
6. The oxygen concentration interval check method according to claim 1, characterized by further comprising: and carrying out temperature field calculation on the fuel rod under the preset oxygen concentration based on the neutron physical field parameter to obtain the temperature field parameter, wherein the temperature field parameter comprises the maximum temperature of a cladding and the center temperature of a core block.
7. The oxygen concentration interval check method according to claim 6, characterized by further comprising: and carrying out cladding oxidation corrosion calculation on the fuel rod under the preset oxygen concentration to obtain cladding oxidation corrosion parameters, wherein the cladding oxidation corrosion parameters comprise the thickness of a magnet ore layer, the thickness of a spinel layer and the cladding corrosion thickness.
8. The oxygen concentration interval check method according to claim 7, characterized by further comprising: And calculating characteristic deformation and strain displacement fields of the fuel rod under the preset oxygen concentration to obtain the contact stress and the geometric parameters of the fuel rod, wherein the geometric parameters of the fuel rod comprise a core block inner side radius, a core block outer side radius, a cladding inner side radius, a cladding outer side radius, a gap size and a cladding thickness.
9. The oxygen concentration interval check method according to claim 8, characterized by further comprising: And performing fission gas behavior calculation on the fuel rod under the preset oxygen concentration to obtain fission gas parameters, wherein the fission gas parameters comprise gap gas pressure, concentration of intra-crystal bubbles, concentration of inter-crystal bubbles, intra-crystal gas swelling and inter-crystal gas swelling.

Description

Oxygen concentration interval checking method Technical Field The invention relates to the technical field of lead bismuth fast reactor oxygen concentration interval checking, in particular to an oxygen concentration interval checking method. Background The lead bismuth fast reactor is taken as one of fourth generation reactors with great development prospect, is widely paid attention at present, and due to the corrosion action of liquid lead bismuth alloy, a fuel rod is easy to lose efficacy due to the liquid metal embrittlement, liquid metal auxiliary damage and environment auxiliary cracking action of a cladding material, the problem of material compatibility becomes one of the problems to be solved in the development of the lead bismuth fast reactor, and in order to reduce the corrosion action of liquid metal on the cladding material of the fuel rod, the integrity of the fuel rod during long-term operation is ensured, and a plurality of different corrosion slowing methods are researched. At present, in lead bismuth fast reactor design, mainstream corrosion-slowing protection measures comprise (1) selecting corrosion-resistant metal material T91 alloy, (2) maintaining the surface of a fuel rod cladding to form a protective oxide layer by controlling the oxygen concentration of liquid metal so as to change the wettability of the liquid metal and prevent the liquid metal from further corrosion, and simultaneously, a gas phase and solid phase oxygen concentration control method is provided and has good effect in an experimental loop. However, the existing method is limited to the corrosion behavior of the lead bismuth fast reactor, and only simple fitting of experimental data is used for obtaining a result. In practical situations, although the existence of the protective oxide layer on the surface of the cladding can be ensured in the oxygen concentration interval, the oxide layer is heat resistance of heat transfer of the cladding, so that the heat transfer on the surface of the cladding is deteriorated, the complete temperature field distribution of the fuel rod is affected, in addition, the thickness of the corroded material of the cladding is weakened, the deformation of the fuel rod is affected by the thinning of the cladding, and meanwhile, due to the fact that obvious axial non-uniformity exists in the lead-bismuth fast reactor along the axial direction of the fuel rod, the axial correlation is generated in the corrosion behavior of the cladding, and the transmission of the influence of the oxidation corrosion of the fuel rod is a multi-physical process. The existing lead-bismuth fast reactor oxygen concentration control technology generally only selects a limit value or an intermediate value from an oxygen concentration interval, does not consider multiple physical properties of a fuel rod, but the existing oxygen concentration interval is obtained only based on a fuel rod material corrosion theory, the oxygen concentration interval is not accurately set, the setting range is wide, the oxygen concentration in the range cannot be ensured to meet the use requirement of the fuel rod, for example, the upper limit value of the oxygen concentration interval may have the problem that heat transfer is seriously deteriorated, the lower limit value of the oxygen concentration interval may have the problem that the oxide layer thickness is too low to inhibit corrosion, and the intermediate value of the oxygen concentration interval may still not meet the long-term use requirement of the fuel rod due to the fact that the effects have high nonlinearity. Therefore, the conventional oxygen concentration control technology also has the problems that the oxygen concentration interval is set inaccurately, and the oxygen concentration interval has an oxygen concentration value which does not meet the use requirement of the fuel rod, so that the heat transfer is easy to deteriorate or corrosion cannot be inhibited when the fuel rod is burnt, and the long-term use requirement of the fuel rod cannot be met. Disclosure of Invention The invention provides an oxygen concentration interval checking method, which aims to solve the technical problem that the existing oxygen concentration interval is not combined with multi-physical characteristic analysis. The invention provides an oxygen concentration interval checking method, which comprises the following steps: Establishing a lead-bismuth fast reactor model, obtaining an initial oxygen concentration interval of the lead-bismuth fast reactor model, and selecting a plurality of preset oxygen concentrations from the initial oxygen concentration interval, wherein the lead-bismuth fast reactor model comprises a fuel rod and a liquid lead-bismuth alloy, and the fuel rod comprises a pellet and a cladding; Performing physical field calculation on the fuel rod under each preset oxygen concentration to obtain physical field parameters corresponding to each preset oxygen concentratio