A method for determining the state of fuel elements based on temperature sensing

Abstract

This invention belongs to the field of reactor fuel damage detection technology, specifically relating to a method for determining the condition of fuel elements based on temperature sensing. It includes the following steps: Step 1: Monitoring the temperature within the air gap between the fuel cladding and the pellets to determine a reference value for the rate of temperature change in the air gap under different puncture sizes in the cladding; Step 2: Determining the condition of the fuel element; Step 3: After determining that a fuel element is damaged, estimating the puncture size in the fuel cladding. The beneficial effects of this invention are: This invention, based on temperature sensing to determine the condition of fuel elements, can improve the accuracy of fuel element condition determination, reflect the fuel element condition in real time, shorten the fuel element condition determination process, and independently monitor the condition of each fuel element, enabling accurate location of damaged fuel and facilitating subsequent maintenance.

Description

Technical Field

[0001] This invention belongs to the field of reactor fuel damage detection technology, specifically relating to a method for determining the state of fuel elements based on temperature sensing. Background Technology

[0002] Fuel elements are the core components and power source of a reactor, and also the first line of defense against radioactive fission products. If a fuel element ruptures, radioactive material within it will leak into the reactor coolant, significantly increasing the coolant's radioactivity level and posing radiation safety risks to normal reactor operation and shutdown maintenance. Therefore, timely and accurate monitoring of fuel element rupture is crucial for reactor operational safety.

[0003] Currently, the methods for monitoring nuclear fuel cladding damage during reactor shutdown and unloading are relatively flexible. Online damage monitoring methods mainly rely on detecting the fission products or decay products released from damaged components, which has certain uncertainties and cannot quickly and accurately locate the damaged area. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining the state of fuel elements based on temperature sensing, which can achieve real-time online accurate monitoring of the state of rod-type fuel elements.

[0005] The technical solution of the present invention is as follows: A method for determining the state of a fuel element based on temperature sensing, comprising the following steps:

[0006] Step 1: Monitor the temperature in the air gap between the fuel cladding and the pellet to determine the reference value for the rate of change of air gap temperature under different rupture sizes in the cladding;

[0007] Step 2: Determine the status of the fuel element;

[0008] Step 3: After determining that the fuel element is damaged, estimate the size of the puncture in the fuel casing.

[0009] In step 1, during the fuel element production process, a temperature sensor is installed inside the fuel casing to monitor the temperature in the air gap between the fuel casing and the fuel pellet.

[0010] In step 1, fuel element test pieces with different gap sizes are prepared in advance, and the rate of change of their air gap temperature is measured under normal operating conditions in the reactor.

[0011] Step 1 uses a theoretical model simulation method to determine the reference value of the air gap temperature change rate under different rupture sizes in the shell.

[0012] In step 2, during reactor operation, the gas gap temperature is monitored in real time by a temperature sensor to determine the condition of the fuel element: when the gas gap temperature remains stable, the fuel element is considered intact; when the gas gap temperature is below 320°C, the fuel element is considered damaged.

[0013] In step 2, the air gap temperature is kept stable with fluctuations within ±5%.

[0014] In step 3, the rate of change of the measured air gap temperature is analyzed and compared with the reference value of the rate of change of air gap temperature under different rupture sizes obtained in step 1.

[0015] The beneficial effects of this invention are as follows: This invention judges the state of fuel elements based on temperature sensing, which can improve the accuracy of fuel element state judgment, reflect the state of fuel elements in real time, shorten the fuel element state judgment process, and perform state monitoring independently for each fuel element, which can realize accurate location of damaged fuel and facilitate subsequent maintenance. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a method for determining the state of a fuel element based on temperature sensing provided by the present invention.

[0017] Figure 2 A schematic diagram illustrating the estimation of the breach size using the rate of change in air gap temperature. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] The air gap between the cladding and the pellet of a rod-type fuel element is typically filled with helium. When the fuel element cladding is intact, the temperature within the air gap should remain relatively stable; however, if the cladding is damaged, coolant will rapidly enter the air gap through the rupture, causing a sharp drop in the temperature within the air gap.

[0020] This invention discloses a method for determining the state of fuel elements based on temperature sensing. This method utilizes temperature sensors to continuously monitor the temperature within the air gap between the fuel element cladding and the pellets online. During reactor operation, when a rapid change in the temperature of the air gap within the fuel element is detected, it can be determined that the fuel element cladding has been damaged. After determining that the fuel element has been damaged, the size of the rupture can be estimated by the rate of change of the air gap temperature, and the development trend of the rupture can be continuously analyzed.

[0021] like Figure 1 As shown, during the fuel element manufacturing process, a temperature sensor is installed inside the fuel element to monitor the temperature in the air gap between the cladding and the pellet.

[0022] Reactor operators can determine the condition of fuel elements by observing changes in the temperature of the gas gaps within the fuel elements.

[0023] During reactor operation, the gas gap temperature should be maintained at a stable value or with slight fluctuations. If the temperature sensor inside the fuel element detects that the gas gap temperature is significantly lower than the design value P0, it can be determined that the fuel element cladding has been damaged.

[0024] like Figure 2 As shown, a reference value for the rate of change of air gap temperature under different puncture sizes of fuel elements can be set through research; after determining that the fuel element has been damaged, the puncture size can be estimated by analyzing the rate of change of air gap temperature, and the trend of puncture change can be continuously analyzed.

[0025] A method for determining the state of a fuel element based on temperature sensing includes the following steps:

[0026] Step 1: During the fuel element production process, a temperature sensor is installed inside the fuel cladding to monitor the temperature in the air gap between the fuel cladding and the pellet (hereinafter referred to as "air gap temperature"). In advance, fuel element test pieces with different puncture sizes are made, and the rate of change of their air gap temperature is measured under normal operating conditions in the reactor. Alternatively, a reference value for the rate of change of air gap temperature under different puncture sizes in the cladding is determined by theoretical model simulation (the rate of change of air gap temperature corresponding to different puncture sizes).

[0027] Step 2: During reactor operation, the gas gap temperature is monitored in real time by temperature sensors to determine the condition of the fuel elements: when the gas gap temperature remains stable (fluctuation within ±5%), the fuel elements are considered intact; when the gas gap temperature is below 320℃, the fuel elements are considered damaged.

[0028] Step 3: After determining that a fuel element has been damaged, the rate of change of the measured air gap temperature over time can be analyzed and compared with the reference values ​​for the rate of change of air gap temperature under different rupture sizes obtained in Step 1. When the rate of change of the measured air gap temperature is close to a certain reference value, the current cladding rupture size can be estimated as the rupture size corresponding to that reference value. The trend of rupture size change can be continuously analyzed, and reactor emergency measures such as continuous observation or power reduction shutdown can be taken.

[0029] The above is merely one embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for determining the state of a fuel element based on temperature sensing, characterized in that, Includes the following steps: Step 1: Monitor the temperature in the air gap between the fuel cladding and the pellets. In advance, by manufacturing fuel element test pieces with different puncture sizes, measure the rate of change of the air gap temperature under normal operating conditions in the reactor, or by using theoretical model simulation, determine the reference value of the rate of change of the air gap temperature under different puncture sizes in the cladding. Step 2: During reactor operation, the gas gap temperature is monitored in real time by temperature sensors to determine the condition of the fuel elements: when the gas gap temperature remains stable, the fuel elements are considered intact. When the air gap temperature is below 320℃, the fuel element is considered damaged. Step 3: After determining that the fuel element is damaged, the size of the puncture in the fuel cladding is estimated by analyzing the rate of change of the air gap temperature measurement and comparing it with the reference value of the rate of change of air gap temperature under different puncture sizes obtained in Step 1.

2. The method for determining the state of a fuel element based on temperature sensing as described in claim 1, characterized in that: In step 1, during the fuel element production process, a temperature sensor is installed inside the fuel casing to monitor the temperature in the air gap between the fuel casing and the fuel pellet.

3. The method for determining the state of a fuel element based on temperature sensing as described in claim 1, characterized in that: In step 2, the air gap temperature is kept stable with fluctuations within ±5%.

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