Reactor core power control method

Abstract

The invention discloses a reactor core power control method which comprises the following steps: during base load operation, inserting and / or lifting a T rod group for temperature regulation and compensation of reactor core reactivity change into and / or from a reactor core, and compensating reactor core temperature change caused by excess reactivity and burnup effect; during operation in a load tracking mode, the effect caused by power change and the coolant temperature change caused by xenon poison change effect are compensated by the T rod group, and the average temperature of the coolant is kept in an operation interval. According to the reactor core power control method disclosed by the invention, automatic control of the reactor core power and temperature in the reactor core operation process is realized only through insertion / lifting of the T rod group; the method is suitable for the reactor core with low linear power density, and under the condition of no axial power distribution control requirement, the reactor core axial power distribution under various normal operation and accident working conditions can still ensure the safety of the reactor core.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear reactor control, and in particular to a reactor core power control method. Background Art

[0002] There are two main methods for achieving core power control in pressurized water nuclear reactors: first, adjusting the boron concentration in the primary coolant to change core reactivity; second, adjusting the position of the control rods in the core to change core reactivity. The first method of regulating reactor power requires the chemical volume control system to inject water or a high-concentration boron solution into the primary coolant to dilute or borate the coolant. Because the primary coolant requires a certain amount of time to mix evenly after each dilution or boration, the boron concentration in the primary coolant changes slowly, and the reactor power is also adjusted slowly. In addition, when the reactor power needs to be increased or decreased frequently, if the boron concentration is adjusted alone to track these increases and decreases, the primary coolant must be frequently diluted and borated, which will generate a large amount of boron solution that needs to be recovered. The second method of regulating reactor power and temperature is to adjust the reactor power and temperature by moving control rods within the core. Its advantage is a relatively fast system response speed; however, under power operating conditions, the movement of control rods in the core will cause the axial power distribution of the core to be distorted, which will also cause problems such as unbalanced axial nuclear fuel consumption in the core. Therefore, the use of control rods to regulate reactor power also has a series of constraints.

[0003] The MODE G control mode, widely used in nuclear power plants, combines the two aforementioned control methods. Boron concentration is adjusted to compensate for long-term reactivity changes caused by xenon toxicity and burnup, while control rod movement is used to compensate for short-term reactivity changes caused by power fluctuations. In addition to the shutdown rod group, the control rod group includes a power compensation rod group and a temperature regulation rod group. Some control rod assemblies in the power compensation rod group utilize gray-body control rods with weaker neutron absorption. Under power operating conditions, the depth of insertion of the power compensation rod group into the core is a function of the power level, and overlapping steps are set between the power compensation rod groups. In this mode, movement of the power compensation rod group does not significantly distort the core's axial power distribution. Power regulation is coordinated by adjusting the boron concentration of the primary coolant to compensate for xenon toxicity.

[0004] The core's operating margin and safety margin are directly related to the shape of the power distribution. The core power distribution includes radial and axial power distributions. The radial power distribution varies little and lacks suitable control measures. The axial power distribution, affected by factors such as power variations, fuel burnup, control rod insertion depth, and xenon oscillation, is a key safety parameter for nuclear power plant operation monitoring. Control rods are the most important means of controlling the axial power distribution, so control rod groups are required in control mode design to control the axial power distribution. Therefore, existing core power management requires multiple control rod groups (such as T-rod groups and K-rod groups) to achieve radial and axial power distribution, which is cumbersome to operate. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an improved reactor core power control method.

[0006] The technical solution adopted by the present invention to solve the technical problem is to provide a reactor core power control method, comprising:

[0007] During base load operation, T-rods used for temperature regulation and compensation of core reactivity changes are inserted into and / or lifted from the core to compensate for core temperature changes caused by excess reactivity and burnup effects.

[0008] When operating in load following mode, the coolant temperature changes caused by the effects of power changes and xenon toxicity changes are compensated by the T-rod group to keep the average coolant temperature within the operating range.

[0009] In some embodiments, the control method during base load operation is:

[0010] The T-rod group is divided into at least one T-rod subgroup, and the T-rod subgroup is inserted into the core and / or lifted from the core.

[0011] In some embodiments, when the T-rod group is divided into two or more T-rod sub-groups, the multiple T-rod sub-groups are inserted into the core and / or lifted from the core according to a set sequence and overlapping steps.

[0012] In some embodiments, the T-bar group is divided into four T-bar subgroups, respectively named T1, T2, T3 and T4;

[0013] The order and overlapping method of the four groups of T-rod groups being inserted into the core are: T1 → T1+T2 → T2 → T2+T3 → T3 → T3+T4 → T4; or: T1 → T1+T2 → T1+T2+T3 → T2+T3 → T2+T3+T4 → T3+T4 → T4; or: T1 → T1+T2 → T1+T2+T3 → T1+T2+T3+T4 → T2+T3+T4 → T3+T4 → T4;

[0014] The order and overlapping method of lifting the four groups of T-rod groups from the core are: T4→T4+T3→T3→T3+T2→T2→T2+T1→T1 or: T4→T4+T3→T4+T3+T2→T3+T2→T3+T2+T1→T2+T1→T1; or: T4→T4+T3→T4+T3+T2→T4+T3+T2+T1→T3+T2+T1→T2+T1→T1.

[0015] In some embodiments, the control method when the load following mode is running is:

[0016] At the start of load tracking, the turbine load decreases and the temperature regulating T-rod group is inserted downward to compensate for the power feedback effect. When the low-power operating platform is reached, the accumulation of xenon introduces negative reactivity, causing the T-rod group to be pulled out. After the xenon peak, the T-rod group will be inserted again to compensate for the change in reactivity to maintain the average coolant temperature within the set operating range.

[0017] As the turbine load increases, the temperature-regulating T-rod group moves upward to compensate for the power feedback effect. When the high-power operating platform is reached, the consumption of xenon introduces positive reactivity, causing the T-rod group to be inserted into the core. After passing through the xenon valley, the T-rod group will move upward again to compensate for the change in reactivity to maintain the average coolant temperature within the set operating range.

[0018] In some embodiments, the T-bar group is divided into at least one T-bar sub-group.

[0019] In some embodiments, when the T-rod group is divided into two or more T-rod sub-groups, the multiple T-rod sub-groups are inserted into the core and / or taken out from the core according to a set sequence and overlapping steps.

[0020] In some embodiments, the T-bar group is divided into four T-bar subgroups, respectively named T1, T2, T3 and T4;

[0021] The order and overlapping method of the four groups of T-rod groups being inserted into the core are: T1 → T1+T2 → T2 → T2+T3 → T3 → T3+T4 → T4; or: T1 → T1+T2 → T1+T2+T3 → T2+T3 → T2+T3+T4 → T3+T4 → T4; or: T1 → T1+T2 → T1+T2+T3 → T1+T2+T3+T4 → T2+T3+T4 → T3+T4 → T4;

[0022] The order in which the four groups of T-rod sub-assemblies are pulled out of the core and the overlapping method is: T4 → T4 + T3 → T3 → T3 + T2 → T2 → T2 + T1 → T1; or: T4 → T4 + T3 → T4 + T3 + T2 → T3 + T2 → T3 + T2 + T1 → T2 + T1 → T1; or: T4 → T4 + T3 → T4 + T3 + T2 → T4 + T3 + T2 + T1 → T3 + T2 + T1 → T2 + T1 → T1.

[0023] In some embodiments, the reactor core power control method further includes: inserting an S-rod group as a shutdown rod to ensure that the reactor has sufficient shutdown margin at any power level.

[0024] The beneficial effects of the present invention are as follows: automatic control of the core power and temperature during the core operation process is achieved only by inserting / lifting a group of control rods (T-rod group), which can achieve core power and temperature control while reducing the core hot spot factor and ensuring core safety; it is suitable for cores with low linear power density, and in the absence of axial power distribution control requirements, the core axial power distribution under various normal operation and accident conditions can still ensure core safety; it simplifies the system design corresponding to the control method, improves the automation and intelligence level of the unit, and reduces human errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0026] Figure 1 1 is a schematic diagram of the distribution of T-rod groups in a reactor core power control method according to an embodiment of the present invention;

[0027] Figure 2 1 is a schematic diagram of a state in which T1 and T2 are increased by one step in the step-by-step region in a reactor core power control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0029] The reactor core power control method of the present invention comprises:

[0030] During base load operation, the T-rod group is inserted into the core and / or lifted from the core to compensate for core temperature changes caused by excess reactivity and burnup effects. The T-rod group has the function of temperature regulation to compensate for changes in core reactivity.

[0031] When operating in load following mode, the coolant temperature changes caused by the effects of power changes and xenon toxicity changes are compensated by the T-rod group to keep the average coolant temperature within the operating range.

[0032] The T-rod group can be divided into at least one T-rod subgroup. These subgroups can be inserted into the core to reduce power and / or lifted from the core to increase power. A T-rod subgroup includes at least one T-rod. The number of T-rod subgroups is determined based on the core power distribution. In some cases, increasing the number of subgroups can reduce core power distribution distortion.

[0033] During baseload operation, the control method is to insert and / or lift the T-rod assembly into the core. If the T-rod assembly is divided into two or more groups, the multiple T-rod groups are inserted and / or lifted from the core in a set sequence and with a set number of overlapping steps.

[0034] For example, a reactor core consisting of 37 fuel assemblies utilizes 21 control rod assemblies. Control rods are divided into two groups based on their function: the T-rod group for temperature regulation and the S-rod group for shutdown. The T-rod group is divided into four T-rod subgroups, designated T1, T2, T3, and T4, which are used to control the average core coolant temperature. The grouping and number of T-rod and S-rod groups are shown in Table 1.

[0035] Table 1

[0036]

[0037] like Figure 1 As shown, T1 is located in the center of the core, and T2, T3, and T4 are arranged in even numbers and symmetrically around T1. The order and overlap of the four T-rod groups for insertion into the core are: T1 → T1 + T2 → T2 → T2 + T3 → T3 → T3 + T4 → T4; the order and overlap of the four T-rod groups for lifting from the core are: T4 → T4 + T3 → T3 → T3 + T2 → T2 → T2 + T1 → T1. The number of overlapping steps between T-rod groups can be set according to actual needs; the distance of each overlapping step (corresponding to the movement distance during insertion or lifting) is also not limited and can be set according to actual needs.

[0038] refer to Figure 2 , which shows that after completing the promotion of T4→T4+T3→T3→T3+T2→T2, T1 and T2 are promoted by 1 step in the overlapping step area, that is, T2+T1→T1.

[0039] In other embodiments of the baseload operation control mode, the order and overlap of the four T-rod groups inserted into the core may be: T1 → T1+T2 → T1+T2+T3 → T2+T3 → T2+T3+T4 → T3+T4 → T4; or: T1 → T1+T2 → T1+T2+T3 → T1+T2+T3+T4 → T2+T3+T4 → T3+T4 → T4. The order and overlap of the four T-rod groups lifted from the core may be: T4 → T4+T3 → T4+T3+T2 → T3+T2 → T3+T2+T1 → T2+T1 → T1; or: T4 → T4+T3 → T4+T3+T2 → T4+T3+T2+T1 → T3+T2+T1 → T2+T1 → T1.

[0040] Similarly, when the T-rod group is divided into two T-rod sub-groups, three T-rod groups, or five T-rod groups or more, the order and overlapping method of insertion into the core and the order and overlapping method of lifting from the core can refer to the above-mentioned four T-rod groups.

[0041] In the control mode during base load operation, the T-rod group is first lifted up according to the initial state of the core, and then inserted according to the change of the core temperature; or, when some T-rod groups have a downward insertion margin in the initial state, they are first inserted into the core, and then lifted up according to the change of the core temperature. The specific operation is adjusted according to the change of the core temperature.

[0042] The control method when operating in load following mode is:

[0043] At the beginning of load tracking, the turbine load decreases and the temperature regulating T-rod group is inserted downward to compensate for the power feedback effect; when the low-power operating platform is reached, the accumulation of xenon introduces negative reactivity, causing the T-rod group to be slowly withdrawn; after passing the xenon peak, the T-rod group will be slowly inserted again to compensate for the change in reactivity to maintain the average coolant temperature within the set operating range.

[0044] As the turbine load increases, the temperature-regulating T-rod group moves upward to compensate for the power feedback effect. When the high-power operating platform is reached, the consumption of xenon introduces positive reactivity, causing the T-rod group to slowly insert into the core. After passing through the xenon valley, the T-rod group will slowly move upward again to compensate for the change in reactivity to maintain the average coolant temperature within the set operating range.

[0045] In the control method of the above-mentioned load following mode operation, in the operation of inserting or lifting the T-rod group, the T-rod group includes at least one T-rod sub-group; when the T-rod group includes two or more T-rod groups, the multiple T-rod groups are inserted into the core and / or lifted out from the core according to the set sequence and overlapping steps.

[0046] For example, a reactor core consisting of 37 fuel assemblies uses 21 control rod assemblies. These T-rod groups are divided into four T-rod subgroups, named T1, T2, T3, and T4, which are used to control the average core coolant temperature. The grouping and number of T-rod and S-rod groups are shown in Table 1.

[0047] For reference Figure 1 T1 is located in the center of the core, and T2, T3, and T4 are even-numbered and symmetrically distributed around T1. The order and overlap of the four T-rod groups for insertion into the core are: T1 → T1 + T2 → T2 → T2 + T3 → T3 → T3 + T4 → T4; the order and overlap of the four T-rod groups for lifting from the core are: T4 → T4 + T3 → T3 → T3 + T2 → T2 → T2 + T1 → T1. The number of overlapping steps between T-rod groups can be set according to actual needs; the distance of each overlapping step (corresponding to the movement distance during insertion or lifting) is also not limited and can be set according to actual needs.

[0048] In other embodiments of the control method for load following mode operation, the order and overlap of the four T-rod groups inserted into the core may be: T1 → T1+T2 → T1+T2+T3 → T2+T3 → T2+T3+T4 → T3+T4 → T4; or: T1 → T1+T2 → T1+T2+T3 → T1+T2+T3+T4 → T2+T3+T4 → T3+T4 → T4. The order and overlap of the four T-rod groups lifted from the core may be: T4 → T4+T3 → T4+T3+T2 → T3+T2 → T3+T2+T1 → T2+T1 → T1; or: T4 → T4+T3 → T4+T3+T2 → T4+T3+T2+T1 → T3+T2+T1 → T2+T1 → T1.

[0049] Similarly, when the T-rod group is divided into two T-rod sub-groups, three T-rod groups, or five T-rod groups or more, the order and overlapping method of insertion into the core and the order and overlapping method of lifting from the core can refer to the above-mentioned four T-rod groups.

[0050] In the control method of load tracking mode operation, according to the initial state of the T-rod group in the core, it is first lifted up and then inserted according to the change of the core temperature; or, according to the initial state, when some T-rod groups have a downward insertion margin, they are first inserted into the core and then lifted up according to the change of the core temperature. The specific operation is adjusted according to the change of the core temperature.

[0051] Furthermore, in some embodiments, the reactor core power control method further includes: inserting an S-rod group as a shutdown rod to ensure that the reactor has sufficient shutdown margin at any power level.

[0052] It can be understood that when the T-rod group is sufficient to control the shutdown, there is no need to insert the S-rod group.

[0053] In summary, the reactor core power control method of the present invention realizes automatic control of the core power and temperature during the operation of the core by only using one set of control rods (T-rod set).

[0054] The present invention is applicable to reactor cores with no axial power distribution control requirements and low linear power density. For such reactor cores, the core axial power distribution under various normal operation and accident conditions can still ensure core safety.

[0055] The present invention simplifies the system design corresponding to the control method, improves the automation and intelligence level of the unit, and reduces human errors.

[0056] The present invention is not only applicable to industrialization, but also to the field of scientific research.

[0057] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A reactor core power control method, characterized in that: include: During base load operation, T-rods used for temperature regulation and compensation of core reactivity changes are inserted into and / or lifted from the core to compensate for core temperature changes caused by excess reactivity and burnup effects. When operating in load following mode, the coolant temperature changes caused by the effects of power changes and xenon toxicity changes are compensated by the T-rod group to keep the average coolant temperature within the operating range.

2. The reactor core power control method according to claim 1, characterized in that: The control method during base load operation is: The T-rod group is divided into at least one T-rod subgroup, and the T-rod subgroup is inserted into the core and / or lifted from the core.

3. The reactor core power control method according to claim 2, characterized in that: When the T-rod group is divided into two or more T-rod sub-groups, the multiple T-rod sub-groups are inserted into the core and / or lifted from the core according to a set sequence and overlapping steps.

4. The reactor core power control method according to claim 3, characterized in that: The T-bar group is divided into four T-bar subgroups, named T1, T2, T3 and T4; The order and overlapping method of the four groups of T-rod groups being inserted into the core are: T1 → T1+T2 → T2 → T2+T3 → T3 → T3+T4 → T4; or: T1 → T1+T2 → T1+T2+T3 → T2+T3 → T2+T3+T4 → T3+T4 → T4; or: T1 → T1+T2 → T1+T2+T3 → T1+T2+T3+T4 → T2+T3+T4 → T3+T4 → T4; The order and overlapping method of lifting the four groups of T-rod groups from the core are: T4→T4+T3→T3→T3+T2→T2→T2+T1→T1; or: T4→T4+T3→T4+T3+T2→T3+T2→T3+T2+T1→T2+T1→T1; or: T4→T4+T3→T4+T3+T2→T4+T3+T2+T1→T3+T2+T1→T2+T1→T1.

5. The reactor core power control method according to claim 1, wherein: The control method when the load following mode is running is: At the start of load tracking, the turbine load decreases and the temperature regulating T-rod group is inserted downward to compensate for the power feedback effect. When the low-power operating platform is reached, the accumulation of xenon introduces negative reactivity, causing the T-rod group to be pulled out. After the xenon peak, the T-rod group will be inserted again to compensate for the change in reactivity to maintain the average coolant temperature within the set operating range. As the turbine load increases, the temperature-regulating T-rod group moves upward to compensate for the power feedback effect. When the high-power operating platform is reached, the consumption of xenon introduces positive reactivity, causing the T-rod group to be inserted into the core. After passing through the xenon valley, the T-rod group will move upward again to compensate for the change in reactivity to maintain the average coolant temperature within the set operating range.

6. The reactor core power control method according to claim 5, characterized in that: The T-bar group is divided into at least one T-bar sub-group.

7. The reactor core power control method according to claim 6, characterized in that: When the T-rod group is divided into two or more T-rod sub-groups, the multiple T-rod sub-groups are inserted into the core and / or taken out from the core according to a set sequence and overlapping steps.

8. The reactor core power control method according to claim 7, characterized in that: The T-bar group is divided into four T-bar subgroups, named T1, T2, T3 and T4; The order and overlapping method of the four groups of T-rod groups being inserted into the core are: T1 → T1+T2 → T2 → T2+T3 → T3 → T3+T4 → T4; or: T1 → T1+T2 → T1+T2+T3 → T2+T3 → T2+T3+T4 → T3+T4 → T4; or: T1 → T1+T2 → T1+T2+T3 → T1+T2+T3+T4 → T2+T3+T4 → T3+T4 → T4; The order in which the four groups of T-rod sub-assemblies are pulled out of the core and the overlapping method is: T4 → T4 + T3 → T3 → T3 + T2 → T2 → T2 + T1 → T1; or: T4 → T4 + T3 → T4 + T3 + T2 → T3 + T2 → T3 + T2 + T1 → T2 + T1 → T1; or: T4 → T4 + T3 → T4 + T3 + T2 → T4 + T3 + T2 + T1 → T3 + T2 + T1 → T2 + T1 → T1.

9. The reactor core power control method according to any one of claims 1 to 8, characterized in that: Also includes: The S-rod group is inserted as a shutdown rod to ensure that the reactor has sufficient shutdown margin at any power level.

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