Method for measuring extension length of large sodium-cooled fast reactor control rod along with temperature

Abstract

The invention particularly relates to a method for measuring the extension length of a large sodium-cooled fast reactor control rod along with temperature, which comprises the following steps of: keeping a reactor to operate stably, and downwards inserting a target control rod to a rigid supporting surface recording meter display rod position; the change of the rod position displayed by the meter is the control rod position difference caused by the expansion of each structure; the rod position difference of the control rod is the deviation between the meter display rod position and the actual rod position of the control rod and is also the extension length of the control rod along with the temperature. According to the method, safe, controllable, effective and accurate measurement of the extension length of the large sodium-cooled fast reactor control rod along with the temperature is realized, so that accurate calculation of the reactivity of the reactor core is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of large-scale pool-type sodium-cooled fast reactor reactors, and in particular to a method for measuring the extended length of a control rod of a large-scale sodium-cooled fast reactor as the temperature increases. Background Art

[0002] With the continuous development of the nuclear energy industry, in order to further improve the safety, economy and reliability of nuclear reactors, countries around the world proposed the development of the fourth generation of advanced reactors in the early 21st century. Pool-type sodium-cooled fast reactor is one of the fourth generation of advanced reactors. To study and develop pool-type sodium-cooled fast reactors, it is necessary to study the thermal hydraulic process of pool-type sodium-cooled fast reactors. Among them, the sodium in the sodium pool is in a high temperature state under normal operating conditions and has complex thermal hydraulic behavior. The thermal stress caused by the large temperature gradient has an important impact on the safety of the solid structure in the flow field. Therefore, thermal analysis of the sodium pool and its structural equipment is very necessary.

[0003] After the power of a large-scale pool-type sodium-cooled fast reactor is increased, the control rod assembly, drive mechanism, core support, and main container will expand significantly due to the gradual increase in core temperature. The expansion effect will eventually lead to a deviation between the apparent rod position and the actual rod position of the control rod, and this deviation reaches the millimeter or even centimeter level. Since this deviation will be loaded on all control rods, the reactivity introduced is very significant, which in turn affects the calculation of core reactivity and design safety. Therefore, the control rod extension effect after the power of a large-scale pool-type sodium-cooled fast reactor cannot be ignored.

[0004] The theoretical calculation of the control rod extension length is a difficult problem for large-scale pool-type sodium-cooled fast reactors due to the complex reactor structure, temperature field, extension coefficients of different materials, material deformation, and limited measurement points. It is necessary to establish a safe, controllable, effective, and accurate test method to measure the extension length of control rods of large-scale pool-type sodium-cooled fast reactors with temperature. Summary of the invention

[0005] The object of the present invention is to provide a method for measuring the extended length of control rods of a large sodium-cooled fast reactor with temperature, so as to achieve safe, controllable, effective and accurate measurement of the extended length of control rods of a large sodium-cooled fast reactor with temperature, thereby ensuring accurate calculation of core reactivity.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for measuring the extended length of a control rod of a large sodium-cooled fast reactor as it changes with temperature comprises the following steps:

[0008] Keep the reactor running stably, insert the target control rod down to the rigid support surface and record the rod position;

[0009] The change in the apparent rod position is the control rod position difference caused by the expansion of various structures; the control rod position difference is the deviation between the apparent rod position and the actual rod position of the control rod, and is also the length of the control rod extended with temperature.

[0010] As one of the feasible ways, a method for measuring the extension length of a control rod of a large sodium-cooled fast reactor with temperature includes the following steps:

[0011] Step 101, the reactor operates stably at the target power step, the target control rod group is located at the center plane position of the reactor, the target compensation rod is located at the critical rod position, and the reactor temperature is kept stable;

[0012] Step 102: Under the target power step, the target control rod is lowered to the lower terminal position by lifting the target compensation rod;

[0013] Step 103, at the target power step, by lifting the target control rod, lower the target control rod to the rigid support surface, record the rod position, and repeat the measurement three times;

[0014] Step 104: Under the target power step, the target control rod is raised to the mid-plane position by inserting the target compensation rod or the target control rod, and the reactor is restored to the initial state;

[0015] The change in the apparent rod position is the control rod position difference caused by the expansion of each structure. The control rod position difference is the deviation between the apparent rod position and the actual rod position of the control rod, and is also the length of the control rod extended with temperature.

[0016] As one possible implementation method, before step 101, the following status needs to be verified:

[0017] (1) The reactor operates stably at the target power for a period of time and the reactor maintains a stable temperature; the nuclear detection detectors inside and outside the reactor work normally; and all control rods in the reactor are located at the target power operation position;

[0018] (2) The control rod drive mechanism operates normally;

[0019] (3) The reactor internal and external measurement systems ensure that there are more than two sets of detection signals.

[0020] As one achievable manner, before step 101 , it is necessary to verify that the reactor has been stably operating at the target power for at least 30 minutes.

[0021] As one of the feasible ways, before step 101, it is necessary to verify that the temperature fluctuation of the reactor at different target power platforms does not exceed ±1°C.

[0022] As one possible implementation method, steps 101-104 specifically include the following steps:

[0023] Step 201: The reactor operates stably at the target power platform for at least 30 minutes, and a No. 1 regulating rod and a No. 2 regulating rod are selected as target control rods. Both the No. 1 regulating rod and the No. 2 regulating rod are located at a position of (650-750) mm on the reactor midplane.

[0024] Step 202, both the No. 1 regulating rod and the No. 2 regulating rod are in working mode, and the No. 1 regulating rod is in automatic regulating mode, and the No. 2 regulating rod is in standby regulating mode; 6 compensation rods are selected as target compensation rods, and are gradually raised by (20-40) mm in sequence, while observing the rod position change and power level of the No. 1 regulating rod, until the rod position of the No. 1 regulating rod drops to (180-220) mm, and the compensation rod stops moving;

[0025] Step 203, both the No. 1 regulating rod and the No. 2 regulating rod are in working mode, and the No. 2 regulating rod is in automatic adjustment mode, and the No. 1 regulating rod is in manual adjustment mode; the No. 1 regulating rod is gradually inserted downward, and the rod position change and power level of the No. 2 regulating rod are observed at the same time, until the No. 1 regulating rod reaches the lower terminal position;

[0026] Step 204, the No. 1 regulating rod is switched from the working mode to the engaging mode, and the No. 1 regulating rod continues to be inserted step by step, while observing the rod position change and the power level of the No. 1 regulating rod. When the insertion instruction fails to cause the rod position change of the No. 1 regulating rod, the rod insertion is stopped, and it is considered that the No. 1 regulating rod has been inserted to the rigid support, and the rod position and related parameters are recorded.

[0027] Step 205, the position of the No. 1 regulating rod is gradually raised to (50-80) mm, and step 204 is repeated twice and the relevant parameters are recorded;

[0028] Step 206, the No. 1 regulating rod is switched from the bite mode to the material change mode; the No. 1 regulating rod is gradually raised to the lower terminal position, and the rod position change and the power level of the No. 2 regulating rod are observed at the same time;

[0029] Step 207, the No. 1 regulating rod is switched from the material changing mode to the working mode and the manual regulating mode; the No. 1 regulating rod continues to be gradually lifted, and the rod position change and the power level of the No. 2 regulating rod are observed at the same time, until the No. 2 regulating rod is inserted down to the rod position of step 1, and the No. 1 regulating rod is stopped from being moved;

[0030] Step 208, both the No. 1 regulating rod and the No. 2 regulating rod are in the working mode, the No. 2 regulating rod is in the standby regulating mode, and the No. 1 regulating rod is in the automatic regulating mode;

[0031] The compensating rods selected in step 209 and step 202 are inserted step by step by (20-40) mm, and the position change of regulating rod No. 1 and the power level are observed at the same time. When regulating rod No. 1 is lifted to the rod position in step 201, the compensating rod is stopped from being moved and the reactor returns to its initial state.

[0032] As one feasible method, in step 202, 6 compensation rods are selected as target compensation rods, which are gradually raised by 30 mm in sequence, while observing the rod position change and power level of adjustment rod No. 1, until the rod position of adjustment rod No. 1 drops to 200 mm, at which time the compensation rod stops moving.

[0033] As one possible implementation method, in step 205, the position of the No. 1 adjustment rod is gradually raised to 50 mm.

[0034] As one of the achievable ways, in steps 203 and 206, the lower terminal position of adjusting rod No. 1 is the lowest point of the working mode of adjusting rod No. 1, that is, the 100mm position of adjusting rod No. 1.

[0035] As one achievable method, in step 209, the compensating rods selected in step 202 are gradually inserted downward by 30 mm.

[0036] Beneficial technical effects of the present invention:

[0037] The method for measuring the extension length of a control rod of a large sodium-cooled fast reactor with temperature of the present invention has been debugged and verified. Through specific control rod operation steps, a target control rod is inserted to a rigid support surface at each target power step during the power increase of the reactor, the rod position is recorded and displayed, and the extension length of the target control rod caused by the expansion of various core structures at different temperatures is actually measured. The method achieves safe, controllable, effective and accurate control of the control rod position and the extension length of the control rod with temperature at each target power step during the power increase of the reactor, thereby ensuring accurate calculation of the core reactivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The present invention is a flow chart of an embodiment of a method for measuring the extended length of a large sodium-cooled fast reactor control rod as it changes with temperature. DETAILED DESCRIPTION

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0040] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0041] The technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings and specific embodiments.

[0042] This embodiment provides a method for measuring the extended length of a control rod of a large sodium-cooled fast reactor as the temperature changes, comprising the following steps:

[0043] Keep the reactor running stably, insert the target control rod down to the rigid support surface and record the rod position;

[0044] The change in the apparent rod position is the control rod position difference caused by the expansion of various structures; the control rod position difference is the deviation between the apparent rod position and the actual rod position of the control rod, and is also the length of the control rod extended with temperature.

[0045] refer to Figure 1 As one of the feasible methods, a method for measuring the extension length of a control rod of a large sodium-cooled fast reactor with temperature includes the following steps:

[0046] Step 101, the reactor operates stably at the target power step, the target control rod group is located at the center plane position of the reactor, the target compensation rod is located at the critical rod position, and the reactor temperature is kept stable;

[0047] Step 102: Under the target power step, the target control rod is lowered to the lower terminal position by lifting the target compensation rod;

[0048] Step 103, at the target power step, by lifting the target control rod, lower the target control rod to the rigid support surface, record the rod position, and repeat the measurement three times;

[0049] Step 104: Under the target power step, the target control rod is raised to the mid-plane position by inserting the target compensation rod or the target control rod, and the reactor is restored to the initial state;

[0050] The change in the apparent rod position is the control rod position difference caused by the expansion of each structure. The control rod position difference is the deviation between the apparent rod position and the actual rod position of the control rod, and is also the length of the control rod extended with temperature.

[0051] In this embodiment, as one of the achievable methods, before step 101, the following status needs to be verified:

[0052] (1) The reactor operates stably at the target power for a period of time and the reactor maintains a stable temperature; the nuclear detection detectors inside and outside the reactor work normally; and all control rods in the reactor are located at the target power operating position;

[0053] (2) The control rod drive mechanism operates normally;

[0054] (3) The reactor internal and external measurement systems ensure that there are more than two sets of detection signals.

[0055] In this embodiment, as one of the feasible ways, before step 101, it is necessary to verify that the reactor has been stably operating at the target power for at least 30 minutes.

[0056] In this embodiment, as one of the feasible ways, before step 101, it is necessary to verify that the temperature fluctuation of the reactor at different target power platforms does not exceed ±1°C.

[0057] In this embodiment, as one of the achievable methods, steps 101-104 specifically include the following steps:

[0058] Step 201: The reactor operates stably at the target power platform for at least 30 minutes, and a No. 1 regulating rod and a No. 2 regulating rod are selected as target control rods. Both the No. 1 regulating rod and the No. 2 regulating rod are located at a position of (650-750) mm on the reactor midplane.

[0059] Step 202, both the No. 1 regulating rod and the No. 2 regulating rod are in working mode, and the No. 1 regulating rod is in automatic regulating mode, and the No. 2 regulating rod is in standby regulating mode; 6 compensation rods are selected as target compensation rods, and are gradually raised by (20-40) mm in sequence, while observing the rod position change and power level of the No. 1 regulating rod, until the rod position of the No. 1 regulating rod drops to (180-220) mm, and the compensation rod stops moving;

[0060] Step 203, both the No. 1 regulating rod and the No. 2 regulating rod are in working mode, and the No. 2 regulating rod is in automatic adjustment mode, and the No. 1 regulating rod is in manual adjustment mode; the No. 1 regulating rod is gradually inserted downward, and the rod position change and power level of the No. 2 regulating rod are observed at the same time, until the No. 1 regulating rod reaches the lower terminal position;

[0061] Step 204, the No. 1 regulating rod is switched from the working mode to the engaging mode, and the No. 1 regulating rod continues to be inserted step by step, while observing the rod position change and the power level of the No. 1 regulating rod. When the insertion instruction fails to cause the rod position change of the No. 1 regulating rod, the rod insertion is stopped, and it is considered that the No. 1 regulating rod has been inserted to the rigid support, and the rod position and related parameters are recorded.

[0062] Step 205, the position of the No. 1 regulating rod is gradually raised to (50-80) mm, and step 204 is repeated twice and the relevant parameters are recorded;

[0063] Step 206, the No. 1 regulating rod is switched from the bite mode to the material change mode; the No. 1 regulating rod is gradually raised to the lower terminal position, and the rod position change and the power level of the No. 2 regulating rod are observed at the same time;

[0064] Step 207, the No. 1 regulating rod is switched from the material changing mode to the working mode and the manual regulating mode; the No. 1 regulating rod continues to be gradually lifted, and the rod position change and the power level of the No. 2 regulating rod are observed at the same time, until the No. 2 regulating rod is inserted down to the rod position of step 1, and the No. 1 regulating rod is stopped from being moved;

[0065] Step 208, both the No. 1 regulating rod and the No. 2 regulating rod are in the working mode, the No. 2 regulating rod is in the standby regulating mode, and the No. 1 regulating rod is in the automatic regulating mode;

[0066] The compensating rods selected in step 209 and step 202 are inserted step by step by (20-40) mm, and the position change of regulating rod No. 1 and the power level are observed at the same time. When regulating rod No. 1 is lifted to the rod position in step 201, the compensating rod is stopped from being moved and the reactor returns to its initial state.

[0067] In this embodiment, as one of the feasible methods, in step 202, 6 compensation rods are selected as target compensation rods, which are gradually raised by 30 mm in sequence, while observing the rod position change and power level of adjustment rod No. 1, until the rod position of adjustment rod No. 1 drops to 200 mm, and the compensation rod stops moving.

[0068] In this embodiment, as one of the feasible ways, in step 205, the position of the No. 1 adjusting rod is gradually raised to 50 mm.

[0069] In this embodiment, as one of the achievable ways, in steps 203 and 206, the lower terminal position of adjusting rod No. 1 is the lowest point of the working mode of adjusting rod No. 1, that is, the 100mm position of adjusting rod No. 1.

[0070] In this embodiment, as one of the feasible ways, in step 209, the compensating rods selected in step 202 are inserted downwards step by step by 30 mm.

[0071] The conditions for upgrading the working mode of the adjusting rod are: (1) the safety rods are all located at the upper terminal position; (2) there is no signal prohibiting the lifting of the rod; (3) the control rod operation mode is in working state; (4) the adjusting rod is selected; (5) the adjusting rod position measurement and display device is working normally; (6) there is no fault alarm of the adjusting rod spindle motor and drive device; (7) the adjusting rod gripper motor is not powered on; (8) the adjusting rod spindle motor is powered on; (9) the controller and IO card are operating normally.

[0072] When all conditions for lifting the regulating rod in working mode are met, the regulating rod has not reached the upper terminal position and there is no manual stop command, the regulating rod can be lifted in working mode.

[0073] When the working mode lifting of the adjusting rod is satisfied and the adjusting rod has not reached the upper terminal position, the adjusting rod can be lifted in the working mode by jogging, and the motor runs one step angle each time.

[0074] The conditions for the adjustment rod working mode to decline are: (1) the control rod operation mode is in working state; (2) the adjustment rod is selected; (3) the adjustment rod position measurement and display device is working normally; (4) the adjustment rod spindle motor and drive device have no fault alarm; (5) the adjustment rod gripper motor is not powered on; (6) the adjustment rod spindle motor is powered on; (7) the controller and IO card are operating normally.

[0075] When the conditions for the adjustment rod to descend in the working mode are met, the adjustment rod has not reached the lower end position and there is no manual stop command, the adjustment rod can be continuously descended in the working mode.

[0076] When the conditions for the adjustment rod to descend in working mode are met and the adjustment rod has not reached the lower end position, the adjustment rod can be moved downward in working mode, and the motor runs one step angle each time.

[0077] It is required that when operating in working mode, the descending action of the adjustment rod takes precedence over the ascending action, and manual control takes precedence over automatic control.

[0078] The upward stroke of the adjustment rod refueling mode is from the rigid support to the refueling terminal, and the downward stroke is from the lower terminal to the refueling terminal. Adjustment rod refueling mode conditions: (1) The control rod operation mode is in the refueling state; (2) The adjustment rod is selected; (3) The adjustment rod position measurement and display device works normally; (4) The adjustment rod spindle motor and drive device have no fault alarm; (5) The adjustment rod gripper motor is not powered on; (6) The adjustment rod spindle motor is powered on; (7) The controller and IO card are running normally.

[0079] When all conditions of the adjusting rod material changing mode are met, the adjusting rod has not reached the material changing terminal position and there is no manual stop command, the adjusting rod can be continuously lifted in the material changing mode.

[0080] When all the conditions of the adjustment rod material change mode are met, the adjustment rod has not reached the lower terminal position and there is no manual stop command, the adjustment rod can be continuously lowered in the material change mode.

[0081] Conditions for the control rod engagement mode to descend: (1) The control rod operation mode is in the engagement state; (2) The control rod No. 1 is selected; (3) The control rod position measurement and display device works normally; (4) There is no fault alarm on the control rod spindle motor and drive device; (5) The control rod gripper motor is not powered on; (6) The control rod spindle motor is powered on; (7) The controller and IO card components operate normally.

[0082] When the conditions for lowering the adjusting rod in bite mode are met, and the adjusting rod is below the lower terminal and has not reached the rigid support, the adjusting rod can be lowered in bite mode, and the single lowering distance shall not exceed (5±1) mm.

[0083] Conditions for the automatic adjustment mode of the adjustment rod: (1) All safety rods are at the upper terminal; (2) The nuclear measurement signal allows automatic operation; (3) The adjustment rod controller and the input and output board are working properly; (4) The adjustment rod is within the working stroke range; (5) The adjustment rod spindle motor and drive device are normal; (6) The adjustment rod position display device is working properly; (7) The adjustment rod spindle is powered on.

[0084] When all conditions for the automatic adjustment mode of the adjustment rod are met, the adjustment rod enters the standby / automatic state.

[0085] When the adjusting rods are switched from manual or standby mode to automatic mode by the operator, if another set of adjusting rods is in automatic adjustment mode, the set of adjusting rods will automatically switch to standby mode.

[0086] When one of the automatic adjustment mode conditions of the adjustment rod is not met, the adjustment rod will switch from the automatic adjustment mode to the manual adjustment mode, and at the same time, the other adjustment rod in standby will automatically transition to the automatic adjustment mode.

[0087] The manual speed of the adjustment rod is 20mm / s; the speed of the adjustment rod when working automatically is 4mm / s~70mm / s; for each adjustment rod, there are three adjustment modes: "manual\standby\automatic", and the three states are complete and mutually exclusive, that is, each power adjustment subsystem must and can only exist in one of the above three states; two adjustment rods are not allowed to be in automatic adjustment mode at the same time.

[0088] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for measuring the extended length of a large sodium-cooled fast reactor control rod with temperature, characterized in that: The steps include: Keep the reactor running stably, insert the target control rod down to the rigid support surface and record the rod position; The change in the apparent rod position is the control rod position difference caused by the expansion of each structure; the control rod position difference is the deviation between the apparent rod position and the actual rod position of the control rod, and is also the length of the control rod extended with temperature.

2. The method for measuring the extended length of control rods of a large sodium-cooled fast reactor with temperature according to claim 1, characterized in that: The specific steps include: Step 101, the reactor operates stably at the target power step, the target control rod group is located at the center plane position of the reactor, the target compensation rod is located at the critical rod position, and the reactor temperature is kept stable; Step 102: Under the target power step, lower the target control rod to the lower terminal position by lifting the target compensation rod; Step 103, at the target power step, by lifting the target control rod, lower the target control rod to the rigid support surface, record the rod position, and repeat the measurement three times; Step 104: Under the target power step, the target control rod is raised to the mid-plane position by inserting the target compensation rod or the target control rod, and the reactor is restored to the initial state; The change in the apparent rod position is the control rod position difference caused by the expansion of each structure. The control rod position difference is the deviation between the apparent rod position and the actual rod position of the control rod, and is also the length of the control rod extended with temperature.

3. The method for measuring the extended length of control rods of a large sodium-cooled fast reactor with temperature according to claim 2, characterized in that: Before step 101, the following status needs to be verified: (1) The reactor operates stably at the target power for a period of time and the reactor maintains a stable temperature; the nuclear detection detectors inside and outside the reactor work normally; and all control rods in the reactor are located at the target power operation position; (2) The control rod drive mechanism operates normally; (3) The reactor internal and external measurement systems ensure that there are more than two sets of detection signals.

4. The method for measuring the extended length of control rods of a large sodium-cooled fast reactor as a function of temperature according to claim 3, characterized in that: Before step 101, it is necessary to verify that the reactor has been operating stably at the target power for at least 30 minutes.

5. The method for measuring the extended length of control rods of a large sodium-cooled fast reactor with temperature according to claim 3, characterized in that: Before step 101, it is necessary to verify that the temperature fluctuation of the reactor at different target power platforms does not exceed ±1°C.

6. The method for measuring the extended length of control rods of a large sodium-cooled fast reactor with temperature according to claim 2, characterized in that: Steps 101-104 specifically include the following steps: Step 201: The reactor operates stably at the target power platform for at least 30 minutes, and a No. 1 regulating rod and a No. 2 regulating rod are selected as target control rods. Both the No. 1 regulating rod and the No. 2 regulating rod are located at a position of (650-750) mm on the reactor midplane. Step 202, both the No. 1 regulating rod and the No. 2 regulating rod are in working mode, and the No. 1 regulating rod is in automatic regulating mode, and the No. 2 regulating rod is in standby regulating mode; 6 compensation rods are selected as target compensation rods, and are gradually raised by (20-40) mm in sequence, while observing the rod position change and power level of the No. 1 regulating rod, until the rod position of the No. 1 regulating rod drops to (180-220) mm, and the compensation rod stops moving; Step 203, both the No. 1 regulating rod and the No. 2 regulating rod are in working mode, and the No. 2 regulating rod is in automatic adjustment mode, and the No. 1 regulating rod is in manual adjustment mode; the No. 1 regulating rod is gradually inserted downward, and the rod position change and power level of the No. 2 regulating rod are observed at the same time, until the No. 1 regulating rod reaches the lower terminal position; Step 204, the No. 1 regulating rod is switched from the working mode to the engaging mode, and the No. 1 regulating rod continues to be inserted step by step, while observing the rod position change and the power level of the No. 1 regulating rod. When the insertion instruction fails to cause the rod position change of the No. 1 regulating rod, the rod insertion is stopped, and it is considered that the No. 1 regulating rod has been inserted to the rigid support, and the rod position and related parameters are recorded. Step 205, the position of the No. 1 regulating rod is gradually raised to (50-80) mm, and step 204 is repeated twice and the relevant parameters are recorded; Step 206, the No. 1 regulating rod is switched from the bite mode to the material change mode; the No. 1 regulating rod is gradually raised to the lower terminal position, and the rod position change and the power level of the No. 2 regulating rod are observed at the same time; Step 207, the No. 1 regulating rod is switched from the material changing mode to the working mode and the manual regulating mode; the No. 1 regulating rod continues to be gradually lifted, and the rod position change and the power level of the No. 2 regulating rod are observed at the same time, until the No. 2 regulating rod is inserted down to the rod position of step 1, and the No. 1 regulating rod is stopped from being moved; Step 208, both the No. 1 regulating rod and the No. 2 regulating rod are in the working mode, the No. 2 regulating rod is in the standby regulating mode, and the No. 1 regulating rod is in the automatic regulating mode; The compensating rods selected in step 209 and step 202 are inserted step by step by (20-40) mm, and the position change of regulating rod No. 1 and the power level are observed at the same time. When regulating rod No. 1 is lifted to the rod position in step 201, the compensating rod is stopped from being moved and the reactor returns to its initial state.

7. The method for measuring the extended length of control rods of a large sodium-cooled fast reactor as a function of temperature according to claim 6, characterized in that: In step 202, 6 compensation rods are selected as target compensation rods and are gradually raised by 30 mm in sequence, while observing the rod position change and power level of No. 1 adjustment rod, until the rod position of No. 1 adjustment rod drops to 200 mm, and the compensation rod stops moving.

8. The method for measuring the extended length of control rods of a large sodium-cooled fast reactor as a function of temperature according to claim 6, characterized in that: In step 205, the position of the No. 1 adjusting rod is gradually raised to 50 mm.

9. The method for measuring the extended length of control rods of a large sodium-cooled fast reactor as a function of temperature according to claim 6, characterized in that: In steps 203 and 206, the lower terminal position of the No. 1 adjusting rod is the lowest point of the No. 1 adjusting rod position working mode, that is, the 100mm position of the No. 1 adjusting rod position.

10. The method for measuring the extended length of control rods of a large sodium-cooled fast reactor as a function of temperature according to claim 6, characterized in that: In step 209, the compensating rods selected in step 202 are gradually inserted downward by 30 mm.

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