Calculation method of transient source item of filter after accident, and wastewater discharge method and device

Abstract

The invention discloses a post-accident filter transient source item calculation method and a wastewater discharge method and device, and belongs to the technical field of nuclear power energy. The method comprises the steps that a first activity component, a second activity component and a third activity component of nuclide m in a second control body are obtained, the first activity component refers to an activity component from incoming flow of the nuclide m, and the second activity component refers to an activity component from nuclide m-2 and nuclide m-1 which are decayed into nuclide m and incoming flow of the nuclide m; the second control body is used for simulating a filter element of the filter, nuclides enter the second control body from the first control body, and the first control body is used for simulating an incoming flow with nuclide activity in exponential decline; and summing the three activity components to obtain a result of a nuclide m transient source item in the filter. The method can solve the problems that a calculation result obtained based on a steady-state working condition is too conservative and low in accuracy in the prior art.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear power energy, and in particular relates to a method and device for calculating transient source terms of a filter after an accident in a nuclear power plant, and a method and device for discharging wastewater after an accident in a nuclear power plant. Background Art

[0002] After a nuclear power plant accident, handling contaminated wastewater is a complex process involving several major steps:

[0003] (1) Wastewater collection and treatment: All contaminated water needs to be collected, including coolant leaks, precipitation, groundwater, etc., which is usually stored in special containers or storage tanks.

[0004] (2) Preliminary treatment: The wastewater is filtered and sedimented to remove suspended solids.

[0005] (3) Removal of radioactive substances: Use ion exchange, reverse osmosis, evaporation concentration or advanced chemical treatment technology to reduce the specific activity of wastewater.

[0006] (4) Trough discharge and monitoring: The treated water is strictly monitored to ensure that it meets national standards before being discharged into the environment in an orderly manner.

[0007] (5) Solid waste treatment: Solid waste generated during the purification process, such as filter materials and sediments, contains a large amount of radioactivity and needs to be safely handled or stored.

[0008] (6) Continuous monitoring: Wastewater or solid waste needs to be monitored over a long period of time until the radioactivity is reduced to a safe level. At the same time, the environmental impact and the safety of workers must also be continuously evaluated and monitored.

[0009] The occasional occurrence of nuclear accidents has put forward more stringent requirements for the design of nuclear power plants. At the same time, the design must consider the storage capacity and purification capacity of radioactive wastewater after nuclear power plant accidents, as well as the requirements for radiation shielding. Radiation shielding design is a complex process aimed at protecting workers from harmful radiation. The radioactive nuclides in the wastewater are purified by the filter, which actually allows the radioactive nuclides to settle and remain on the filter element of the filter to achieve the purpose of filtering and purification. The amount of radioactive nuclides retained on the filter element becomes the equipment source term, which is the basis of radiation shielding design and the basis for calculating solid waste source terms.

[0010] At present, the calculation of equipment source terms is based on steady-state conditions, assuming that the incoming flow is a constant flow, and ignoring the influence of the decay chain. However, under actual accident transient conditions, the inlet flow or the inlet nuclide activity concentration changes with time. Therefore, the equipment source terms calculated based on steady-state conditions have the problem of overly conservative calculation results and low accuracy. Summary of the invention

[0011] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art and to provide a method and device for calculating the transient source terms of filters after a nuclear power plant accident, and a method and device for discharging wastewater after a nuclear power plant accident, which can obtain the dynamic activity of nuclides and take into account the influence of decay chains, so that the calculation results of the transient source terms of the equipment that are more consistent with the actual situation and more accurate can be obtained.

[0012] In a first aspect, the present invention provides a method for calculating a transient source term of a filter after an accident in a nuclear power plant, comprising: obtaining a first activity component of a nuclide m in a second control volume;

[0013] The second activity component The third activity component in, Refers to the activity component derived from the incoming flow of nuclide m, Refers to the activity component derived from the decay of nuclide m-2 and nuclide m-1 into nuclide m and its incoming flux. Refers to the activity component derived from the decay of nuclide m-2 into nuclide m-1, nuclide m, and the incoming flow. The second control body is used to simulate the filter element. The nuclide enters the second control body from the first control body. The first control body is used to simulate the incoming flow with exponentially decreasing nuclide activity. The first activity component The second activity component The third activity component Sum and obtain the result of the transient source term of nuclide m in the filter.

[0014] Preferably, the first activity component satisfy:

[0015]

[0016] Among them, Q m satisfy:

[0017]

[0018] g is the flow rate from the first control body to the second control body, m 3 / h;

[0019] is the initial activity of nuclide m in the first control volume, Bq;

[0020] is the fraction of nuclide m entering the second control volume from the inlet flow;

[0021] is the equivalent decay constant of nuclide i in the first control volume, h -1, i = m, m-1, m-2;

[0022] is the equivalent decay constant of nuclide i in the second control volume, h -1 ;

[0023] t is time, h.

[0024] Preferably, the second activity component satisfy:

[0025] when hour:

[0026]

[0027] when hour:

[0028]

[0029] in:

[0030]

[0031] in, is the equivalent decay constant of nuclide m in the first control volume, h -1 ;

[0032] is the equivalent decay constant of nuclide m in the second control volume, h -1 ;

[0033] λ m is the decay constant of nuclide m, h -1 ;

[0034] is the deposition coefficient of nuclide m;

[0035] is the fraction of nuclide mk entering the second control volume from the inlet flow;

[0036] is the ratio of nuclide mk decaying into nuclide m;

[0037] λ m-k is the decay constant of the nuclide mk, h -1 ;

[0038] is the initial activity of the nuclide mk in the first control volume, Bq;

[0039] is the equivalent decay constant of nuclide j in the first control volume, h -1 , j = m, m-1, m-2;

[0040] is the equivalent decay constant of nuclide j in the second control volume, h -1 .

[0041] Preferably, the third activity component satisfy:

[0042] when hour:

[0043]

[0044] when hour:

[0045]

[0046] Preferably, the first activity component of the nuclide m in the second control volume is obtained The second activity component The third activity component Previously, the calculation method also included: constructing a dual control body model with a first control body and a second control body as application objects according to the decay of nuclides in the storage device and the accumulation process in the filter.

[0047] Preferably, before constructing the dual control body model with the first control body and the second control body as the application objects, the calculation method also includes: setting the inlet flow of the first control body to zero; setting the flow from the first control body to the second control body to be a constant; setting the inlet specific activity of the second control body to be the outlet specific activity of the first control body, and changing it with time; setting the nuclide decay to include the decay of the nuclide m, the decay of the parent nucleus and the alternate-generation parent nucleus in the dual control body model.

[0048] In a second aspect, the present invention also provides a method for discharging wastewater after a nuclear power plant accident, comprising: predicting the transient source term results of a target period according to the calculation method of the transient source term of the filter after a nuclear power plant accident described in the first aspect; and determining a wastewater discharge plan according to the transient source term results of the target period.

[0049] In a third aspect, the present invention also provides a calculation device for a transient source term of a filter after an accident in a nuclear power plant, comprising: an acquisition module for acquiring a first activity component of the nuclide m in the second control volume The second activity component The third activity component in, Refers to the activity component derived from the incoming flow of nuclide m, Refers to the activity component derived from the decay of nuclide m-2 and nuclide m-1 into nuclide m and its incoming flux. Refers to the activity component derived from the decay of nuclide m-2 into nuclide m-1, nuclide m, and the incoming flow. The second control body is used to simulate the filter element. The nuclide enters the second control body from the first control body. The first control body is used to simulate the incoming flow with exponentially decreasing nuclide activity. The calculation module is connected to the acquisition module and is used to convert the first activity component The second activity component The third activity component Sum and obtain the result of the transient source term of nuclide m in the filter.

[0050] In a fourth aspect, the present invention further provides a device for discharging wastewater after an accident in a nuclear power plant, comprising the device for calculating the transient source term of the filter after an accident in a nuclear power plant as described in the third aspect, and a determination module. The device for calculating the transient source term of the filter after an accident in a nuclear power plant is used to predict the transient source term result of the target period. The determination module is connected to the calculation device and is used to determine the wastewater discharge plan according to the transient source term result of the target period.

[0051] In a fifth aspect, the present invention further provides an electronic device, comprising: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to execute the method for calculating the transient source term of the filter after the nuclear power plant accident described in the first aspect or the method for discharging wastewater after the nuclear power plant accident described in the second aspect.

[0052] The present invention provides a method and device for calculating the transient source term of a filter after an accident in a nuclear power plant, and a method and device for discharging wastewater after an accident in a nuclear power plant. The method and device calculate the sum of three activity components of nuclide m with the filter as the second control body, and obtain the result of the transient source term of nuclide m in the filter, wherein the three activity components include the activity component of the nuclide m inflow from the storage device as the first control body, the activity component of nuclide m-2 and nuclide m-1 decaying to nuclide m in the first control body and the second control body, and the activity component of nuclide m-2 decaying to nuclide m-1 and nuclide m in the first control body and the second control body in sequence. Since the activities of nuclide m in the two control bodies both consider the three-generation decay chain, and consider the exponentially decreasing trend of the inflow from the first control body under transient conditions, that is, the nuclide concentration changes with time, which is consistent with the actual situation, the calculation result of the transient source term is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a flow chart of a method for calculating transient source terms of a filter after an accident in a nuclear power plant according to Embodiment 1 of the present invention;

[0054] Figure 2 This is a schematic diagram of a dual control body model according to Example 1 of the present invention. DETAILED DESCRIPTION

[0055] In order to enable those skilled in the art to better understand the technical solution of the present invention, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0056] It should be understood that the specific embodiments and drawings described herein are only used to explain the present invention rather than to limit the present invention.

[0057] It can be understood that, in the absence of conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other.

[0058] It can be understood that, for the convenience of description, the drawings of the present invention only show the parts related to the present invention, while the parts irrelevant to the present invention are not shown in the drawings.

[0059] It can be understood that each unit and module involved in the embodiments of the present invention may correspond to only one physical structure, or may be composed of multiple physical structures, or multiple units and modules may be integrated into one physical structure.

[0060] It can be understood that, without conflict, the functions and steps marked in the flowcharts and block diagrams of the present invention may occur in an order different from that marked in the drawings.

[0061] It is understood that the flowcharts and block diagrams of the present invention illustrate the possible architectures, functions, and operations of the systems, devices, equipment, and methods according to the various embodiments of the present invention. Each box in the flowchart or block diagram may represent a unit, module, program segment, or code, which contains executable instructions for implementing the specified functions. Moreover, each box or combination of boxes in the block diagram and flowchart may be implemented by a hardware-based system that implements the specified functions, or may be implemented by a combination of hardware and computer instructions.

[0062] It can be understood that the units and modules involved in the embodiments of the present invention can be implemented by software or hardware. For example, the units and modules can be located in a processor.

[0063] According to the transient process of wastewater passing through the filter in the storage equipment after the nuclear power plant accident, the mass exchange, retention and decay processes of radionuclides were considered, and reasonable and conservative assumptions were adopted to establish a physical model that conforms to the actual process, solve the differential equations, and then give the transient source term of the filter.

[0064] Embodiment 1:

[0065] like Figure 1As shown, this embodiment provides a method for calculating the transient source term of the filter after an accident in a nuclear power plant, which is applicable to the scenario of a pressurized water reactor nuclear power plant, and is not only applicable to the calculation of the transient source term of the filter after an accident, but also applicable to considering the radioactive decay in the fuel rods after shutdown, and calculating the source term leaking out of the fuel rods. Compared with the normal operating conditions of a nuclear power plant (i.e., steady-state conditions), the accident transient conditions emphasize the process of change. For the filter, the inlet flow rate and the nuclide activity concentration are generally constants during normal operation, while the inlet flow rate or the nuclide activity concentration at the inlet changes with time under the accident transient conditions, generally showing an exponential downward trend.

[0066] The calculation method of transient source term of filter after nuclear power plant accident includes:

[0067] Step 101, obtaining the first activity component of nuclide m in the second control volume The second activity component The third activity component in, Refers to the activity component derived from the incoming flow of nuclide m, Refers to the activity component derived from the decay of nuclide m-2 and nuclide m-1 into nuclide m and its incoming flux. It refers to the activity component derived from the decay of nuclide m-2 into nuclide m-1, nuclide m, and its incoming flow. The second control body is used to simulate the filter element. The nuclide enters the second control body from the first control body. The first control body is used to simulate the incoming flow with exponentially decreasing nuclide activity.

[0068] In this embodiment, the nuclide m is used to characterize one nuclide or multiple nuclides. Figure 2 As shown, the first control body is connected to the second control body, the first control body is used to simulate the storage equipment, the activity in the first control body shows an exponential downward trend, the second control body is used to simulate the filter, and the dual control body model formed by the first control body and the second control body is used to simulate the attenuation of nuclides in the storage equipment and the deposition of radioactive nuclides on the filter after the nuclear power plant accident.

[0069] Optionally, before step 101, the method for calculating transient source terms of filters after nuclear power plant accidents further includes: constructing a dual control body model with a first control body and a second control body as application objects according to the decay of nuclides in storage equipment and the accumulation process in the filter.

[0070] In this embodiment, a dual control body model that conforms to the actual process is constructed, and the differential equations of each control body model are solved to provide the transient source term of the filter.

[0071] Step 102: convert the first activity component The second activity component The third activity component Sum and obtain the result of the transient source term of nuclide m in the filter.

[0072] In this embodiment, the transient source term of nuclide m in the filter is the sum of three activity components of nuclide m, and the result of the transient source term of nuclide m in the filter is obtained based on the sum of the three activity components.

[0073] Optionally, the first activity component satisfy:

[0074]

[0075] Among them, Q m satisfy:

[0076]

[0077] g is the flow rate from the first control body to the second control body, m 3 / h;

[0078] is the initial activity of nuclide m in the first control volume, Bq;

[0079] is the fraction of nuclide m entering the second control volume from the inlet flow;

[0080] is the equivalent decay constant of nuclide i in the first control volume, h -1 , i = m, m-1, m-2;

[0081] is the equivalent decay constant of nuclide i in the second control volume, h -1 ;

[0082] t is time, h.

[0083] In this embodiment, g, Input parameters are known quantities that can be obtained through calculation or measurement. To find the solution.

[0084] Optionally, the second activity component satisfy:

[0085] when hour:

[0086]

[0087] when hour:

[0088]

[0089] in:

[0090]

[0091] in, is the equivalent decay constant of nuclide m in the first control volume, h -1 ;

[0092] is the equivalent decay constant of nuclide m in the second control volume, h -1 ;

[0093] λ m is the decay constant of nuclide m, h -1 ;

[0094] is the deposition coefficient of nuclide m;

[0095] is the fraction of nuclide mk entering the second control volume from the inlet flow;

[0096] is the ratio of nuclide mk decaying into nuclide m;

[0097] λ m-k is the decay constant of the nuclide mk, h -1 ;

[0098] is the initial activity of the nuclide mk in the first control volume, Bq;

[0099] is the equivalent decay constant of nuclide j in the first control volume, h -1 , j = m, m-1, m-2;

[0100] is the equivalent decay constant of nuclide j in the second control volume, h -1 It should be noted that the upper right corner value of the equivalent attenuation constant is used to characterize the control volume, and the lower right corner value is used to characterize the specific nuclide.

[0101] In this embodiment, λ m , λ m-k , Input parameters are known quantities that can be obtained through calculation or measurement. To find the solution.

[0102] Optionally, the third activity component satisfy:

[0103] when hour:

[0104]

[0105] when hour:

[0106]

[0107] In this embodiment, is the quantity to be solved. The other parameters are input parameters, which are known quantities that can be obtained through calculation or measurement.

[0108] Optionally, before constructing a dual control body model with the first control body and the second control body as application objects, the calculation method of the transient source term of the filter after the nuclear power plant accident also includes:

[0109] Setting the inlet flow rate of the first control body to zero;

[0110] Setting the flow rate from the first control body to the second control body to be constant;

[0111] Setting the inlet specific activity of the second control body to the outlet specific activity of the first control body and changing it with time;

[0112] The nuclide decay is assumed to include the decay of nuclide m in the double control body model, the decay of the parent nucleus and the decay of the alternate-generation parent nucleus.

[0113] In this embodiment, by setting reasonable conditions, the analysis of the dual control body model is facilitated, and by focusing on key factors, noise or irrelevant interference is eliminated, thereby improving the accuracy of the calculation results. It should be noted that the dual control body model of this embodiment has a variety of application objects, and is used for the nuclide migration and decay process of the transient working conditions of nuclear power plant accidents. It is not only applied to the calculation of the transient source term of the filter, but also can be applied to the process that meets the set conditions of this embodiment, such as the radioactive decay in the fuel rod after shutdown and the transient source term leaking out of the rod.

[0114] The calculation method of the transient source term of the filter after the nuclear power plant accident provided in this embodiment obtains the result of the transient source term of the nuclide m in the filter by calculating the sum of the three activity components of the nuclide m with the filter as the second control body, wherein the three activity components include the activity component of the nuclide m inflow from the storage device as the first control body, the activity component of the nuclide m-2 and nuclide m-1 in the first control body and the second control body decaying into the nuclide m, and the activity component of the nuclide m-2 in the first control body and the second control body decaying into the nuclide m-1 and the nuclide m in sequence. Since the activities of the nuclide m in the two control bodies both consider the three-generation decay chain, and consider the exponential decline trend of the inflow from the first control body under the transient working condition, that is, the nuclide concentration changes with time, which is consistent with the actual situation, the present embodiment can obtain the dynamic activity and the transient source term calculation result considering the influence of the decay chain, thereby improving the accuracy of the transient source term result and providing a calculation basis for the orderly discharge of radioactive wastewater. In addition, the calculation method of the transient source term of this embodiment is applicable to other dual control body models that meet the set conditions and has a wide range of applications.

[0115] Embodiment 2:

[0116] This embodiment provides a method for calculating the transient source term of a filter after a nuclear power plant accident, which is essentially the first activity component in Embodiment 1. The second activity component The third activity component The derivation process.

[0117] This embodiment establishes a dual control body model, such as Figure 2 As shown, the first control body is connected in series with the second control body. The first control body is used to simulate the incoming flow with exponentially decreasing activity. The setting is:

[0118] (1) The inlet flow rate of the first control body is zero;

[0119] (2) The flow rate from the first control body to the second control body is constant;

[0120] (3) The inlet specific activity of the second control body is the outlet specific activity of the first control body and changes with time;

[0121] (4) When dealing with the decay of radioactive nuclides, the decay of the nuclides in the dual control body model and the decay of the parent nucleus and the alternate generation parent nucleus should be considered.

[0122] The dual control body model is used to simulate the attenuation of nuclides in storage tanks and the deposition of radioactive nuclides on filters after a nuclear power plant accident. The first control body is used to simulate the storage tank, and the second control body is used to simulate the filter.

[0123] The calculation method of transient source term of filter after nuclear power plant accident includes:

[0124] S1, calculate the equivalent decay constant of the nuclides in the first control volume and the second control volume according to the decay of the nuclides themselves, the removal by the circulation filtration and the emission share;

[0125] The equivalent decay constants of the nuclides in the first control volume and the second control volume satisfy:

[0126]

[0127] in, is the equivalent decay constant of the first control nuclide m, h -1 ;

[0128] is the equivalent decay constant of nuclide m in the second control volume, h -1 ;

[0129] λ m is the decay constant of nuclide m, h -1 ;

[0130] G (1) is the circulating filtration flow rate of the first control body, m 3 / h;

[0131] G (2) is the circulating filtration flow of the second control body, m 3 / h;

[0132] ε m (1) is the circulation filtration coefficient of the first control body;

[0133] ε m (2) is the circulation filtration coefficient of the second control body;

[0134] F (1) is the discharge flow rate of the first control body, m 3 / h;

[0135] F (2) is the discharge flow rate of the second control body, m 3 / h;

[0136] V (1) is the volume of the first control volume, m 3 ;

[0137] V (2) is the volume of the second control volume, m 3 .

[0138] In this embodiment, the parameters on the right side of the equation are known quantities. To solve the quantity, The solution method is the existing technology.

[0139] S2, based on the fact that the activity change rate of nuclide m in the first control volume is equal to the decay amount of nuclide m, calculate the component of the residual activity of nuclide m in the first control volume after t time, where the initial activity of nuclide m is

[0140] Specifically, the differential equation is established:

[0141]

[0142] The boundary conditions are: when t = 0,

[0143] The solution is:

[0144]

[0145] A m is the activity of nuclide m in the first control volume, Bq;

[0146] is the component of the residual activity of nuclide m in the first control volume after time t, Bq;

[0147] t is time, h;

[0148] is the initial activity of nuclide m in the first control volume, Bq.

[0149] S3, based on the decay of nuclides m-1 and m-2 into nuclides m, calculate the residual activity component of nuclides mk in the first control body that decays into nuclides m after t time, k=1, 2.

[0150] Specifically, the differential equation is established:

[0151]

[0152] The boundary conditions are: when t = 0, A m =0.

[0153] The solution is:

[0154]

[0155] make:

[0156]

[0157] but:

[0158]

[0159] A m is the activity of the first control nuclide m, Bq;

[0160] is the ratio of nuclide mk decaying into nuclide m;

[0161] λ m-k is the decay constant of the nuclide mk, h -1 ;

[0162] A m-k is the activity of the nuclide mk in the first control volume, Bq;

[0163] is the initial activity of the nuclide mk in the first control volume, Bq;

[0164] is the residual activity component of nuclide mk in the first control body after the nuclide m decays to nuclide m after t time, Bq;

[0165] is the equivalent decay constant of nuclide i in the first control volume, h -1 , i = m, m-1, m-2;

[0166] is the equivalent decay constant of nuclide j in the first control volume, h -1 , j=m, m-1, m-2.

[0167] S4, according to the nuclide m-2 decaying into nuclide m-1 and nuclide m in sequence, calculate the residual activity component of nuclide m in the first control body after t time when nuclide m-2 decays into nuclide m-1 and then decays into nuclide m.

[0168] Specifically, the differential equation is established:

[0169]

[0170] The boundary conditions are: when t = 0, A m =0.

[0171] From step S3, we can know that the nuclides from the decay of m-1→m are:

[0172]

[0173] Therefore, the nuclide from the decay of m-2→m-1 is:

[0174]

[0175] Solved:

[0176]

[0177] but:

[0178]

[0179] make:

[0180]

[0181] A m is the activity of nuclide m in the first control volume, Bq;

[0182] A m-1 is the activity of nuclide m-1 in the first control body, Bq;

[0183] is the ratio of nuclide m-2 decaying into nuclide m-1;

[0184] is the residual activity component of nuclide m-2 in the first control body after decaying to nuclide m-1 and then decaying to nuclide m after t time, Bq;

[0185] j=m, m-1, m-2, i=m, m-1, m-2.

[0186] S5, according to the sum of the incoming flow of nuclide m in the first control body and the decay amount of nuclide m in the second control body being equal to the activity change rate of nuclide m in the second control body, the activity component of nuclide m in the second control body is calculated, that is, the first activity component of nuclide m in the second control body is calculated The initial activity of the nuclide m in the second control volume is 0.

[0187] Specifically, the differential equation is established:

[0188]

[0189] The boundary conditions are: when t = 0, A m =0.

[0190] Multiply both sides of the equation by the integrating factor

[0191]

[0192] It can be seen that the solution of the equation is divided into two cases. hour:

[0193]

[0194] when hour:

[0195]

[0196] make:

[0197]

[0198] but:

[0199]

[0200] A m is the activity of nuclide m in the second control volume, Bq;

[0201] g is the flow rate from the first control body to the second control body, m 3 / h;

[0202] is the fraction of the inlet flow entering the second control body;

[0203] i = m, m-1, m-2;

[0204] is the activity component of nuclide m in the second control volume, that is, the first activity component, Bq.

[0205] S6, according to the decay of nuclides m-1 and m-2 in the second control body into nuclides m, and the decay of nuclides m-1 and m-2 in the first control body into nuclides m, and then entering the second control body, calculate the components of nuclides m in the second control body derived from decay and incoming flow, that is, calculate the second activity component of nuclides m in the second control body

[0206] Specifically, the differential equation is established:

[0207]

[0208] From step S5, we can see that:

[0209]

[0210] From step S3, we can see that:

[0211]

[0212] The boundary conditions are: when t = 0, A m =0.

[0213] Solved:

[0214] when hour:

[0215]

[0216] when hour:

[0217]

[0218] in:

[0219]

[0220] A m is the activity of nuclide m in the second control volume, Bq;

[0221] is the deposition coefficient of nuclide m;

[0222] is the component of nuclide m in the second control body that comes from decay and incoming flow, Bq.

[0223] S7, according to the nuclide m-2 in the second control body decaying into nuclide m-1 and nuclide m in sequence, and the nuclide m-2 in the first control body decaying into nuclide m-1 and nuclide m in sequence, and then entering the second control body, calculate the component of the nuclide m in the second control body derived from the decay of m-2→m-1→m and the incoming flow, that is, calculate the third activity component of the nuclide m in the second control body

[0224] Specifically, the differential equation is established:

[0225]

[0226] From step S6, we can see that:

[0227] when hour:

[0228]

[0229]

[0230] when hour:

[0231]

[0232] From step S4, we can see that:

[0233]

[0234] Solved:

[0235] when hour:

[0236]

[0237] when hour:

[0238]

[0239] is the component of nuclide m in the second control body that comes from m-2→m-1→m decay and the incoming flow, Bq.

[0240] S8, the activity of nuclide m in the second control volume is equal to the sum of the components of each source, that is, the transient source term of nuclide m in the filter is equal to the first activity component The second activity component The third activity component sum:

[0241]

[0242] A m is the activity of nuclide m in the second control volume, Bq.

[0243] The calculation method of the transient source term of the filter after the nuclear power plant accident provided in this embodiment establishes a set of dual control body mathematical models, simulates the decay of radioactive nuclides in the storage tank and the accumulation process on the filter element, and provides a reasonable calculation model and calculation method. It can also provide dynamic activity and consider the influence of the decay chain, thereby improving the accuracy of the calculation results and providing suggestions for the storage and orderly discharge of radioactive waste liquid.

[0244] Embodiment 3:

[0245] This embodiment provides a method for discharging wastewater after a nuclear power plant accident, comprising:

[0246] Step 301: predict the transient source term results of the target period according to the calculation method of the transient source term of the filter after the nuclear power plant accident described in Example 1 or Example 2.

[0247] Step 302, determining a wastewater discharge plan according to the transient source term results during the target period.

[0248] In this embodiment, there are strict standards for the discharge of radioactive wastewater, with monthly, quarterly, and annual limits, requiring uniform and orderly discharge. If the concentration of radioactive wastewater is predicted (i.e., transient source term), the discharge period and discharge amount are determined according to the concentration. For example, if the predicted concentration exceeds the first threshold, the discharge amount is reduced, and if the predicted concentration is less than the first threshold, the discharge amount is increased.

[0249] Specifically, step 302 includes: determining whether the transient source item result of the target time period is less than a first threshold value; in response to being less than the first threshold value, determining the wastewater discharge amount to be a second threshold value; in response to being greater than the first threshold value, determining the wastewater discharge amount to be a third threshold value, wherein the second threshold value is greater than the third threshold value.

[0250] Embodiment 4:

[0251] This embodiment provides a calculation device for transient source terms of a filter after an accident in a nuclear power plant, comprising:

[0252] An acquisition module is used to acquire the first activity component of the nuclide m in the second control volume The second activity component The third activity component in, Refers to the activity component derived from the incoming flow of nuclide m, Refers to the activity component derived from the decay of nuclide m-2 and nuclide m-1 into nuclide m and its incoming flux. It refers to the activity component derived from the decay of nuclide m-2 into nuclide m-1, nuclide m, and its incoming flow. The second control body is used to simulate the filter element. The nuclide enters the second control body from the first control body. The first control body is used to simulate the incoming flow with exponentially decreasing nuclide activity.

[0253] A calculation module is connected to the acquisition module and is used to convert the first activity component The second activity component The third activity component Sum and obtain the result of the transient source term of nuclide m in the filter.

[0254] In this embodiment, the first activity component The second activity component The third activity component The expression of is as described in Example 1 or Example 2 and will not be repeated here.

[0255] Embodiment 5:

[0256] This embodiment provides a discharge device for wastewater after a nuclear power plant accident, including the calculation device for the transient source term of the filter after a nuclear power plant accident described in Example 4, and a determination module.

[0257] The calculation device of the transient source term of the filter after the nuclear power plant accident is used to predict the transient source term result of the target period. The determination module is connected to the calculation device and is used to determine the wastewater discharge plan according to the transient source term result of the target period.

[0258] Embodiment 6:

[0259] The present embodiment provides a device for calculating radioactive nuclide decay, comprising: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method for calculating the transient source term of a filter after a nuclear power plant accident described in Embodiment 1 or Embodiment 2, or the method for discharging wastewater after a nuclear power plant accident described in Embodiment 3, by executing the computer instructions.

[0260] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for calculating transient source terms of filters after a nuclear power plant accident, characterized in that: include: Get the first activity component of nuclide m in the second control volume The second activity component The third activity component in, Refers to the activity component derived from the incoming flow of nuclide m, Refers to the activity component derived from the decay of nuclide m-2 and nuclide m-1 into nuclide m and its incoming flux. Refers to the activity component derived from the decay of nuclide m-2 into nuclide m-1, nuclide m, and the incoming flow. The second control body is used to simulate the filter element. The nuclide enters the second control body from the first control body. The first control body is used to simulate the incoming flow with exponentially decreasing nuclide activity. The first activity component The second activity component The third activity component Sum and obtain the result of the transient source term of nuclide m in the filter.

2. The method according to claim 1, characterized in that The first activity component satisfy: Among them, Q m satisfy: g is the flow rate from the first control body to the second control body, m 3 / h; is the initial activity of nuclide m in the first control volume, Bq; is the fraction of nuclide m entering the second control volume from the inlet flow; is the equivalent decay constant of nuclide i in the first control volume, h -1 , i = m, m-1, m-2; is the equivalent decay constant of nuclide i in the second control volume, h -1 ; t is time, h.

3. The method according to claim 2, characterized in that The second activity component satisfy: when hour: when hour: in: in, is the equivalent decay constant of nuclide m in the first control volume, h -1 ; is the equivalent decay constant of nuclide m in the second control volume, h -1 ; λ m is the decay constant of nuclide m, h -1 ; is the deposition coefficient of nuclide m; is the fraction of nuclide mk entering the second control volume from the inlet flow; is the ratio of nuclide mk decaying into nuclide m; λ m-k is the decay constant of the nuclide mk, h -1 ; is the initial activity of the nuclide mk in the first control volume, Bq; is the equivalent decay constant of nuclide j in the first control volume, h -1 , j = m, m-1, m-2; is the equivalent decay constant of nuclide j in the second control volume, h -1 .

4. The method according to claim 3, characterized in that The third activity component satisfy: when hour: when hour:

5. The method according to claim 3, characterized in that: In obtaining the first activity component of the nuclide m in the second control volume The second activity component The third activity component Previously, it also included: According to the decay of nuclides in storage equipment and the accumulation process in filters, a double control body model with a first control body and a second control body as application objects is constructed.

6. The method according to claim 5, characterized in that Before constructing the dual control body model with the first control body and the second control body as application objects, the method further includes: Setting the inlet flow rate of the first control body to zero; Setting the flow rate from the first control body to the second control body to be constant; Setting the inlet specific activity of the second control body to the outlet specific activity of the first control body and changing it with time; The nuclide decay is assumed to include the decay of nuclide m in the double control body model, the decay of the parent nucleus and the decay of the alternate-generation parent nucleus.

7. A method for discharging wastewater after a nuclear power plant accident, characterized in that: include: Predict the transient source term results of the target period according to the calculation method of the transient source term of the filter after the nuclear power plant accident according to any one of claims 1 to 6; Determine wastewater discharge plans based on transient source term results during the target period.

8. A device for calculating transient source terms of filters after a nuclear power plant accident, characterized in that: include: An acquisition module is used to acquire the first activity component of the nuclide m in the second control volume The second activity component The third activity component in, Refers to the activity component derived from the incoming flow of nuclide m, Refers to the activity component derived from the decay of nuclide m-2 and nuclide m-1 into nuclide m and its incoming flux. Refers to the activity component derived from the decay of nuclide m-2 into nuclide m-1, nuclide m, and its incoming flow. The second control body is used to simulate the filter element. The nuclide enters the second control body from the first control body. The first control body is used to simulate the incoming flow with exponentially decreasing nuclide activity. A calculation module is connected to the acquisition module and is used to convert the first activity component The second activity component The third activity component Sum and obtain the result of the transient source term of nuclide m in the filter.

9. A discharge device for wastewater after a nuclear power plant accident, characterized in that: The device for calculating the transient source term of the filter after the accident of the nuclear power plant as claimed in claim 8, and the determination module, The calculation device of transient source term of filter after nuclear power plant accident is used to predict the transient source term results of target period. A determination module is connected to the computing device and is used to determine a wastewater discharge plan according to transient source term results during a target period.

10. An electronic device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method for calculating the transient source term of a filter after an accident in a nuclear power plant as described in any one of claims 1 to 6 or the method for discharging wastewater after an accident in a nuclear power plant as described in claim 7 by executing the computer instructions.

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