A method for estimating the radioactivity concentration of desalinated water of a nuclear energy seawater desalination plant

Abstract

The application discloses a method for estimating radioactivity concentration of desalinated water of a nuclear energy seawater desalination device, which comprises the following steps: firstly, according to the technological process of the nuclear energy thermal method seawater desalination device, the flowing direction of the medium and the migration direction of the radioactive substances are sorted out; then, according to the approach of the radioactive substances entering and removing in the intermediate loop fluid, the nuclide balance equation of the intermediate loop fluid is established, and then the radioactivity concentration calculation model of the intermediate loop water and the radioactivity concentration calculation model of the flash steam of the flash tank are obtained; then, according to the technological scheme of the MED device, the radioactivity concentration calculation model of the steam and the condensed water generated by each heat exchanger is established; then, the radioactivity level of the steam and the condensed water generated by each heat exchanger of the MED is calculated; finally, whether the desalinated water can meet the radioactivity control index is evaluated. The method can accurately calculate the radioactivity activity concentration of the desalinated water, and provides a reliable basis for the safety evaluation of the nuclear energy thermal method seawater desalination device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear energy, in particular to a method for estimating the radioactivity concentration of desalinated water of a nuclear energy seawater desalination device. BACKGROUND

[0002] Nuclear energy, as a safe, clean and carbon-free energy source, can significantly reduce pollutant emissions and play an increasingly important role in energy saving and emission reduction. Nuclear energy heating can not only meet the growing energy demand of economic and social development, effectively improve the energy structure, and alleviate the increasingly serious energy supply shortage, but also promote comprehensive economic strength and industrial technology level, and has great significance in protecting the environment and achieving the "double carbon" goal.

[0003] In coastal areas lacking fresh water resources and lacking conventional energy or having difficulty transporting conventional fuels, using nuclear energy to desalinate seawater is a good choice. The demand for seawater desalination is increasing, and desalinated seawater will become a source of water supply in coastal water-scarce areas, and nuclear energy heat seawater desalination technology can achieve low-carbon or zero-carbon desalinated water supply.

[0004] How to ensure the safe operation of the seawater desalination device and the safe use of the user is a difficulty, and nuclear safety is the primary consideration. Only by calculating the radioactivity concentration in the nuclear energy heating process can the radioactivity risk be evaluated to protect the safety of the environment and human health. However, there is no method in the prior art to calculate the radioactivity concentration of the intermediate loop fluid, so as to calculate the radioactivity concentration of the desalinated water. SUMMARY

[0005] The present application solves the technical problems of the prior art, and provides a method for estimating the radioactivity concentration of desalinated water of a nuclear energy seawater desalination device, which can accurately calculate the radioactivity concentration and provide a reliable basis for safety evaluation of the nuclear energy heat seawater desalination device.

[0006] In a first aspect, the present application provides a method for calculating the radioactivity concentration of an intermediate loop fluid, the intermediate loop being arranged between a main steam system of a nuclear power plant and a MED (Multiple Effect Distillation, MED for short) device, the intermediate loop being used to transport steam generated by flashing desalted water heated by the two-loop steam in a flash tank to the MED device, and collect condensate water generated by a first effect heat exchanger of the MED device in a condensate tank, the intermediate loop being provided with a heat energy conversion device, a flash tank and a condensate tank;

[0007] The method comprises the following steps:

[0008] Step D1: obtaining intermediate loop design parameters and nuclide information; the intermediate loop design parameters and nuclide information include secondary loop steam radioactivity concentration, intermediate loop heat energy conversion device leakage rate, intermediate loop liquid charge, decay constant, MED device first effect heat exchanger leakage rate, cumulative running time and flash tank flash fraction;

[0009] Step D2: calculating radioactivity concentration of intermediate loop gaseous fluid and liquid fluid respectively according to the intermediate loop design parameters and nuclide information; wherein the intermediate loop liquid fluid is intermediate loop water, and the intermediate loop gaseous fluid is steam obtained by flash tank flashing;

[0010] According to formula (1), the radioactivity concentration of the intermediate loop water is calculated:

[0011]

[0012] Wherein:

[0013] C0 represents the radioactivity concentration of the intermediate loop water;

[0014] A represents the secondary loop steam radioactivity concentration;

[0015] L0 represents the leakage rate of the intermediate loop heat energy conversion device; the intermediate loop heat energy conversion device is a heat exchanger or a heat pump in the intermediate loop;

[0016] W S represents the liquid charge of the intermediate loop;

[0017] λ represents the decay constant;

[0018] L1 is the leakage rate of the first effect heat exchanger of the MED device;

[0019] T is the cumulative running time;

[0020] F HC is the flash fraction of the flash tank;

[0021] The formula for calculating the radioactivity concentration of the steam obtained by the flash tank is as follows:

[0022] S0 = C0·F HC

[0023] Wherein, S0 represents the radioactivity concentration of the steam obtained by the flash tank.

[0024] Further, before the step D1, it further includes a step D0,

[0025] Step D0: constructing a nuclide balance equation, the nuclide balance equation is used to solve the radioactivity concentration of the intermediate loop water;

[0026] The nuclide balance equation is derived based on the flow direction of the medium and the radioactive migration direction, and is shown in equation (2):

[0027]

[0028] in, This indicates that C0 is the derivative of time t.

[0029] Furthermore, the calculation of the radioactivity concentration of the intermediate loop water includes:

[0030] When the intermediate loop heat energy conversion equipment is in normal operating condition and the first-effect heat exchanger of the MED device is in normal operating condition, the first calculation of the radioactivity concentration of the intermediate loop water; or,

[0031] The second calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop heat conversion equipment is in normal operating condition and the first-effect heat exchanger of the MED device is in a broken condition; or,

[0032] The third calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop heat energy conversion equipment is in a broken working condition and the first-effect heat exchanger of the MED device is in a normal working condition.

[0033] The fourth calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop heat energy conversion equipment is in a broken condition and the first-effect heat exchanger of the MED device is in a broken condition.

[0034] The calculation formula for the first calculation is formula (3):

[0035]

[0036] The calculation formula for the second calculation is formula (4):

[0037]

[0038] The calculation formula for the third calculation is formula (5):

[0039]

[0040] The calculation formula for the fourth calculation is formula (6):

[0041]

[0042] in,

[0043] L C0 This indicates the leakage rate of the intermediate circuit heat energy conversion equipment under normal operating conditions.

[0044] L A0 leakage rate of the intermediate circuit thermal energy conversion device in the intermediate circuit break condition;

[0045] L C1 leakage rate of the MED device first effect heat exchanger in the MED device first effect heat exchanger normal condition;

[0046] L A1 leakage rate of the MED device first effect heat exchanger in the MED device first effect heat exchanger break condition.

[0047] In a second aspect, the present application provides a method for calculating the radioactivity concentration of a heat exchanger fluid of a MED device, the MED device being provided with an intermediate circuit between a main steam system of a nuclear power plant, the intermediate circuit being used to transport steam generated by flashing desalted water heated by two-loop steam in a flash tank to the MED device, and to collect condensate water generated by a first effect heat exchanger of the MED device in a condensate tank, the intermediate circuit being provided with a thermal energy conversion device, a flash tank and a condensate tank, the method comprising the following steps:

[0048] Step S1: obtaining the radioactivity concentration of the intermediate circuit water by using the method for calculating the radioactivity concentration of the intermediate circuit fluid according to the first aspect;

[0049] Step S2: obtaining the radioactivity concentration of a fluid of any effect heat exchanger of the MED device according to the radioactivity concentration of the intermediate circuit water; the MED device has i effect heat exchangers, and i is greater than or equal to 2.

[0050] Further, the step S2 specifically comprises the following steps:

[0051] Step S21: calculating the radioactivity concentration of seawater of a first effect heat exchanger of the MED device according to the radioactivity concentration of the intermediate circuit water, and calculating the radioactivity concentration of steam of the first effect heat exchanger of the MED device based on the radioactivity concentration of the seawater of the first effect heat exchanger of the MED device;

[0052] The calculation formula of the radioactivity concentration of the seawater of the first effect heat exchanger of the MED device is formula (7):

[0053]

[0054] wherein,

[0055] C1 represents the radioactivity concentration of the seawater of the first effect heat exchanger of the MED device;

[0056] C0 represents the radioactivity concentration of the intermediate circuit water;

[0057] L1 is the leakage rate of the first effect heat exchanger of the MED device;

[0058] F 0_1 represents the seawater flow rate of the first effect heat exchanger;

[0059] B represents the radioactivity concentration of the seawater at the water intake;

[0060] The formula for calculating the radioactivity concentration of the steam of the first effect heat exchanger of the MED device is formula (8):

[0061] S1=C1·F HS (8)

[0062] wherein,

[0063] S1 represents the radioactivity concentration of the steam of the first effect heat exchanger of the MED device;

[0064] F HS is the steam-water distribution factor;

[0065] Step S22: Based on the radioactivity concentration of the seawater of the first effect heat exchanger of the MED device and the radioactivity concentration of the steam of the first effect heat exchanger, the radioactivity concentration of the seawater of the second effect heat exchanger of the MED device and the radioactivity concentration of the steam of the second effect heat exchanger are calculated; and in turn, until the radioactivity concentration of the seawater of the i-th effect heat exchanger of the MED device and the radioactivity concentration of the steam of the i-th effect heat exchanger are calculated;

[0066] The formula for calculating the radioactivity concentration of the seawater of the i-th effect heat exchanger is formula (9):

[0067]

[0068] The formula for calculating the radioactivity concentration of the steam of the i-th effect heat exchanger is formula (10):

[0069] S i =C i ·F HS (10)

[0070] wherein,

[0071] C i is the radioactivity concentration of the seawater in the i-th effect heat exchanger;

[0072] C i-1 is the radioactivity concentration of the seawater in the (i-1)-th effect heat exchanger;

[0073] Li is the leakage rate of the i-th effect heat exchanger;

[0074] F 0_i is the seawater flow rate of the i-th effect heat exchanger;

[0075] Si is the radioactivity concentration of the steam in the i-th heat exchanger.

[0076] Further, the calculation of the radioactivity concentration of the seawater in the i-th heat exchanger comprises:

[0077] the calculation of the radioactivity concentration of the seawater in the i-th heat exchanger in normal condition; or,

[0078] the calculation of the radioactivity concentration of the seawater in the i-th heat exchanger in break condition;

[0079] the calculation of the radioactivity concentration of the seawater in the i-th heat exchanger in normal condition is shown in formula (11)

[0080]

[0081] wherein, L Ci is the leakage rate of the i-th heat exchanger in normal condition;

[0082] the calculation of the radioactivity concentration of the seawater in the i-th heat exchanger in break condition is shown in formula (12)

[0083]

[0084] wherein, L Ai is the leakage rate of the i-th heat exchanger in break condition.

[0085] In a third aspect, the present application provides a method for calculating the radioactivity concentration of desalinated water, wherein the desalinated water is the condensed water output by a nuclear energy heat method seawater desalination coupling device.

[0086] The method comprises the following steps:

[0087] Step K1: using the activity concentration calculation method of the fluid in the heat exchanger of the MED device according to the second aspect, to calculate the radioactivity concentration of the fluid in the heat exchanger of the MED device;

[0088] Step K2: according to the radioactivity concentration of the fluid in the heat exchanger of the MED device, to calculate the radioactivity concentration of the condensed water of the steam in the heat exchanger of the MED device, so as to obtain the radioactivity concentration of the desalinated water.

[0089] Further, the step K2 specifically comprises:

[0090] According to the radioactivity concentration of the desalinated water in the heat exchanger of the MED device, to calculate the radioactivity concentration of the condensed water of the steam in the second heat exchanger of the MED device; and in the same way, to calculate the radioactivity concentration of the condensed water of the steam in the i-th heat exchanger of the MED device;

[0091] The calculation formula of the radioactivity concentration of the steam condensate water of the second effect heat exchanger is shown in formula (13) :

[0092] W2=S1·D W (13)

[0093] wherein,

[0094] W2 represents the radioactivity concentration of the steam condensate water of the second effect heat exchanger;

[0095] S1 represents the radioactivity concentration of the steam of the first effect heat exchanger of the MED device;

[0096] Dw represents the density of the desalination water;

[0097] The calculation formula of the radioactivity concentration of the steam condensate water of the i-th effect heat exchanger is shown in formula (14) :

[0098] W i i =S i-1 i-1 ·D W (14)

[0099] wherein,

[0100] W i i represents the radioactivity concentration of the steam condensate water of the i-th effect heat exchanger;

[0101] S i-1 i-1 represents the radioactivity concentration of the steam of the i-1-th effect heat exchanger of the MED device.

[0102] In a fourth aspect, the application provides a method for evaluating the radioactivity concentration of desalination water, which comprises the following steps:

[0103] The radioactivity concentration of the steam condensate water of the heat exchanger of the MED device is calculated by using the method for calculating the radioactivity concentration of desalination water according to the third aspect;

[0104] According to the radioactivity concentration of the steam condensate water of the heat exchanger of the MED device, it is evaluated whether the steam condensate water of the heat exchanger of the MED device can be introduced into the desalination water pipe.

[0105] Further, according to the radioactivity concentration of the steam condensate water of the heat exchanger of the MED device, it is evaluated whether the steam condensate water of the heat exchanger of the MED device can be introduced into the desalination water pipe, which specifically comprises:

[0106] The radioactivity concentration of the steam condensate water of the heat exchanger of the MED device is compared with a preset control index to determine whether the radioactivity concentration of the steam condensate water of the heat exchanger of the MED device meets the requirements of relevant regulations and standards:

[0107] If the radioactivity concentration of the MED device heat exchanger steam condensate water is not within the preset control index range, it is evaluated that the MED device heat exchanger steam condensate water cannot be introduced into the desalination water pipe; if the radioactivity concentration of the MED device heat exchanger steam condensate water is within the preset control index range, it is evaluated that the MED device heat exchanger steam condensate water can be introduced into the desalination water pipe.

[0108] The beneficial effects of the present application are as follows:

[0109] 1. The present application can accurately calculate the radioactivity concentration of the intermediate loop fluid, providing a reliable basis for safety evaluation of the nuclear energy heat method seawater desalination device.

[0110] 2. The present application comprehensively considers the radioactivity risk in the entire system, making safety management more comprehensive.

[0111] 3. The present application can timely discover potential radioactivity risks, helping to timely discover and handle possible radioactivity risks, thereby ensuring the safety and stability of system operation.

[0112] 4. The present application can improve the evaluation and management level of system radioactivity risks, providing more reliable protection for system operation.

[0113] 5. The present application first calculates the radioactivity concentration of the intermediate loop water, then calculates the radioactivity concentration between the MED device heat exchanger fluids, and finally calculates the activity concentration of the condensate water, the entire process is more comprehensive and complete.

[0114] 6. The present application can directly evaluate whether the steam condensate water meets the radioactivity standard for being introduced into the desalination water pipe, providing a simple and effective evaluation means for the operator, and helping to implement system monitoring and management.

[0115] 7. The present application can quickly judge whether the radioactivity concentration of the steam condensate water is within the control index range, thereby quickly making a decision on whether to introduce it into the desalination water pipe. BRIEF DESCRIPTION OF DRAWINGS

[0116] Figure 1 The flow chart for estimating the desalination water radioactivity concentration of the nuclear energy heat method seawater desalination coupling device in the embodiment of the present application;

[0117] Figure 2 The process scheme schematic diagram of the nuclear energy heat method seawater desalination coupling device in the embodiment of the present application. DETAILED DESCRIPTION

[0118] To enable those skilled in the art to better understand the technical solutions of the present application, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0119] It can be understood that the specific embodiments and drawings described herein are merely intended to explain the present application, but not to limit the present application.

[0120] It can be understood that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0121] It can be understood that, for the convenience of description, only the parts related to the present application are shown in the drawings of the present application, and the parts irrelevant to the present application are not shown in the drawings.

[0122] It can be understood that each unit and module involved in the embodiments of the present application can correspond to only one entity structure, or can be composed of multiple entity structures, or multiple units and modules can be integrated into one entity structure.

[0123] It can be understood that the functions and steps marked in the flowcharts and block diagrams of the present application can occur in an order different from that marked in the drawings without conflict.

[0124] It can be understood that in the flowcharts and block diagrams of the present application, the architecture, functions and operations of the possible implementations of the system, device, equipment and method according to the embodiments of the present application are shown. Each block in the flowchart or block diagram can represent a unit, module, program segment, code, which contains executable instructions for realizing the specified functions. Moreover, each block or combination of blocks in the block diagram and flowchart can be realized by a hardware-based system for realizing the specified functions, or by a combination of hardware and computer instructions.

[0125] It can be understood that the units and modules involved in the embodiments of the present application can be realized in the form of software or hardware, for example, the units and modules can be located in a processor.

[0126] Embodiment 1:

[0127] As Figure 1As shown, the embodiment provides a method for estimating the radioactivity concentration of desalinated water of a nuclear energy heat method seawater desalination coupling device. The method first combs the flow direction of the medium and the migration direction of the radioactive substances according to the process flow of the nuclear energy heat method seawater desalination device, then establishes the nuclide balance equation of the intermediate loop fluid according to the approach of the radioactive substances entering and removing in the intermediate loop fluid, and further obtains the radioactivity concentration calculation model of the intermediate loop water and the radioactivity concentration calculation model of the flash steam of the flash tank, then establishes the radioactivity concentration calculation model of the steam and the condensed water generated by each heat exchanger according to the process scheme of the MED device, then calculates the radioactivity level of the steam and the condensed water generated by each MED, and finally evaluates whether the desalinated water can meet the radioactivity control index. The method can accurately calculate the radioactivity activity concentration of the desalinated water, and provides a reliable basis for the safety evaluation of the nuclear energy heat method seawater desalination device. The method comprises the following steps:

[0128] First step: comb the flow direction of the medium and the migration direction of the radioactive substances according to the process flow of the nuclear energy heat method seawater desalination device.

[0129] The specific process flow is as shown in Figure 2 In the nuclear energy heat method seawater desalination coupling scheme of the nuclear power plant two-loop steam extraction and the low-temperature multi-effect seawater desalination device, the steam turbine extraction is used as the heating steam source to heat the seawater for evaporation treatment. Since the two-loop has potential radioactivity, the normal operation leakage and accident leakage of the pressurized water reactor two-loop, and the normal operation leakage and accident leakage of the heat exchanger and the multi-effect distillation (MED) device need to be considered, which may cause the radioactive substances to migrate into the desalinated water with the heating medium. In order to block the direct leakage of the radioactive substances carried by the heating gas source into the MED device, an intermediate loop is added between the heating gas source and the MED device, and a flash tank is arranged to generate the heating gas source of the seawater desalination device.

[0130] Second step: establish the nuclide balance equation of the intermediate loop fluid according to the approach of the radioactive substances entering and removing in the intermediate loop fluid, and obtain the radioactivity concentration calculation model of the intermediate loop fluid and the radioactivity concentration calculation model of the flash steam of the flash tank;

[0131] The approach of the radioactive substances entering and removing in the intermediate loop fluid is determined according to the flow direction of the medium and the migration direction of the radioactive substances.

[0132] The nuclide balance equation is obtained based on the flow direction of the medium and the migration direction of the radioactive substances. The formula of the nuclide balance equation is:

[0133]

[0134] Wherein, represents the derivative of C0 with respect to time t.

[0135] Solving the nuclide balance equation, the radioactivity concentration of the intermediate loop water is obtained as:

[0136]

[0137] The radioactivity concentration of the steam obtained by flashing through the flash tank is:

[0138] S0=C0·F HC

[0139] Wherein:

[0140] C0 represents the radioactivity concentration of the intermediate loop water;

[0141] A represents the radioactivity concentration of the secondary loop steam;

[0142] L0 represents the leakage rate of the intermediate loop heat conversion device, which is a heat exchanger or a heat pump in the intermediate loop;

[0143] W S represents the liquid charge of the intermediate loop;

[0144] λ represents the decay constant;

[0145] L1 is the leakage rate of the first effect heat exchanger of the MED device;

[0146] T is the cumulative operating time;

[0147] F HC is the flashing fraction of the flash tank;

[0148] The calculation formula of the intermediate loop gaseous fluid is as follows:

[0149] S0=C0·F HC

[0150] Wherein, S0 represents the intermediate loop gaseous fluid.

[0151] As a specific embodiment, the radioactivity concentration calculation of the intermediate loop water includes:

[0152] The first calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop heat conversion device is in normal condition and the first effect heat exchanger of the MED device is in normal condition; or,

[0153] The second calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop heat conversion device is in normal condition and the first effect heat exchanger of the MED device is in break condition; or,

[0154] The third calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop heat energy conversion device is in a break condition and the first effect heat exchanger of the MED device is in a normal condition;

[0155] The fourth calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop heat energy conversion device is in a break condition and the first effect heat exchanger of the MED device is in a break condition;

[0156] The calculation formula of the first calculation is as follows:

[0157]

[0158] The calculation formula of the second calculation is as follows:

[0159]

[0160] The calculation formula of the third calculation is as follows:

[0161]

[0162] The calculation formula of the fourth calculation is as follows:

[0163]

[0164] L C0 L represents the leakage rate of the intermediate loop heat energy conversion device in a normal condition;

[0165] L A0 L represents the leakage rate of the intermediate loop heat energy conversion device in a break condition;

[0166] L C1 L represents the leakage rate of the first effect heat exchanger of the MED device in a normal condition;

[0167] L A1 L represents the leakage rate of the first effect heat exchanger of the MED device in a break condition.

[0168] Step 3: According to the process scheme of the MED device, a radioactivity concentration calculation model is established for the steam and condensate produced by each effect MED heat exchanger.

[0169] First, the radioactivity concentration of the intermediate loop water is obtained by using the steps in Step 2; then, the radioactivity concentration of each effect fluid of the MED device is obtained according to the radioactivity concentration of the intermediate loop water; the MED device includes an i-effect heat exchanger, and i is greater than or equal to 2.

[0170] The process of obtaining the radioactivity concentration of each effect fluid of the MED device is as follows:

[0171] Step S21: calculating the radioactivity concentration of seawater of the first effect heat exchanger of the MED device and the radioactivity concentration of steam of the first effect heat exchanger;

[0172] The formula for calculating the radioactivity concentration of seawater of the first effect heat exchanger of the MED device is as follows:

[0173]

[0174] Wherein,

[0175] C1 represents the radioactivity concentration of seawater of the first effect heat exchanger of the MED device;

[0176] C0 represents the radioactivity concentration of intermediate loop water;

[0177] L1 is the leakage rate of the first effect heat exchanger of the MED device;

[0178] F 0_1 represents the seawater flow rate of the first effect heat exchanger;

[0179] B represents the radioactivity concentration of seawater background;

[0180] The formula for calculating the radioactivity concentration of steam of the first effect heat exchanger of the MED device is as follows:

[0181] S1 = C1·F HS

[0182] Wherein,

[0183] S1 represents the radioactivity concentration of steam of the first effect heat exchanger of the MED device;

[0184] F HS is the steam-water distribution factor;

[0185] Step S22: based on the radioactivity concentration of seawater of the first effect heat exchanger of the MED device and the radioactivity concentration of steam of the first effect heat exchanger, the radioactivity concentration of seawater of the second effect heat exchanger of the MED device and the radioactivity concentration of steam of the second effect heat exchanger are calculated; and the same is sequentially performed until the radioactivity concentration of seawater of the i-th effect heat exchanger of the MED device and the radioactivity concentration of steam of the i-th effect heat exchanger are calculated;

[0186] The formula for calculating the radioactivity concentration of seawater of the i-th effect heat exchanger is as follows:

[0187]

[0188] The formula for calculating the radioactivity concentration of steam of the i-th effect heat exchanger is as follows:

[0189] S i = C i• F HS

[0190] wherein,

[0191] C i is the radioactivity concentration of seawater in the i-th heat exchanger;

[0192] C i-1 is the radioactivity concentration of seawater in the i-1-th heat exchanger;

[0193] Li is the leakage rate of the i-th heat exchanger;

[0194] F 0_i is the seawater flow rate of the i-th heat exchanger;

[0195] S i is the radioactivity concentration of steam in the i-th heat exchanger.

[0196] However, in specific implementation, there can be different working conditions, so the calculation of the radioactivity concentration of seawater in the i-th heat exchanger includes:

[0197] the calculation of the radioactivity concentration of seawater in the i-th heat exchanger under normal working conditions; or,

[0198] the calculation of the radioactivity concentration of seawater in the i-th heat exchanger under break condition;

[0199] The calculation of the radioactivity concentration of seawater in the i-th heat exchanger under normal working conditions is as follows:

[0200]

[0201] wherein, L Ci is the leakage rate of the i-th heat exchanger under normal working conditions;

[0202] The calculation of the radioactivity concentration of seawater in the i-th heat exchanger under break condition is as follows:

[0203]

[0204] wherein, L Ai is the leakage rate of the i-th heat exchanger under break condition.

[0205] Fourthly, determine the analysis working condition, decay constant λ, nuclear power plant secondary loop steam source term, seawater radioactivity concentration at the water intake, intermediate loop: leakage rate L C0 under normal working condition, leakage rate L A0 under break condition, flash fraction F HC of the flash tank, intermediate loop normal operation time t1, break duration t2, intermediate loop water volume W S ; first effect: seawater flow rate F0_1 leakage rate L in normal operation C1 leakage rate L in break condition A1 sea water flow F in the second effect 0_2 leakage rate L in normal operation C2 leakage rate L in break condition A2 sea water flow F in the third effect 0_3 leakage rate L in normal operation C3 leakage rate L in break condition A3 density D of the desalinated water W steam-water distribution factor F in the steam condensation process of the MED device HS and other parameters.

[0206] In the fifth step, based on the above model and parameters, the radioactivity concentration of the intermediate loop fluid and the flash steam is calculated and analyzed, and the radioactivity level of the steam and the condensed water generated by each effect of the MED is calculated step by step.

[0207] First, the activity concentration calculation method of the fluid in the MED device heat exchanger is used to calculate the radioactivity activity concentration of the desalinated water in the MED device heat exchanger; then, the radioactivity activity concentration of the desalinated water in the MED device heat exchanger is obtained.

[0208] As a specific implementation, the process of obtaining the radioactivity activity concentration of the steam condensed water in the MED device heat exchanger includes:

[0209] The radioactivity activity concentration of the steam condensed water in the second effect heat exchanger of the MED device is obtained according to the radioactivity activity concentration of the desalinated water in the MED device heat exchanger; and the radioactivity activity concentration of the steam condensed water in the i-th effect heat exchanger of the MED device is obtained by analogy;

[0210] The calculation formula of the radioactivity activity concentration of the steam condensed water in the second effect heat exchanger is as follows:

[0211] W2=S1·D W

[0212] Wherein,

[0213] W2 represents the radioactivity activity concentration of the steam condensed water in the second effect heat exchanger;

[0214] S1 represents the radioactivity activity concentration of the steam in the first effect heat exchanger of the MED device;

[0215] Dw represents the density of the desalinated water;

[0216] The calculation formula of the radioactivity activity concentration of the steam condensed water in the i-th effect heat exchanger is as follows:

[0217] Wi = S i-1 · D W

[0218] wherein,

[0219] W i represents the radioactivity concentration of steam condensate of the i-th heat exchanger of the MED device;

[0220] S i-1 represents the radioactivity concentration of steam of the i-1-th heat exchanger of the MED device.

[0221] In the sixth step, whether the desalinated water can meet the radioactive control index is evaluated according to the analysis result of the condensate water of each evaporator of the MED device.

[0222] According to the radioactivity concentration of the steam condensate of the heat exchanger of the MED device, whether the steam condensate of the heat exchanger of the MED device can be introduced into the desalinated water pipe is evaluated, which specifically comprises:

[0223] The radioactivity concentration of the steam condensate of the heat exchanger of the MED device is compared with the preset control index to determine whether the radioactivity concentration of the steam condensate of the heat exchanger of the MED device meets the requirements of the relevant regulations and standards:

[0224] If the radioactivity concentration of the steam condensate of the heat exchanger of the MED device is not within the preset control index range, it is determined that the radioactivity concentration of the steam condensate of the heat exchanger of the MED device cannot meet the requirements of the relevant regulations and standards, so that it is evaluated that the steam condensate of the heat exchanger of the MED device cannot be introduced into the desalinated water pipe; if the radioactivity concentration of the steam condensate of the heat exchanger of the MED device is within the preset control index range, it is determined that the radioactivity concentration of the steam condensate of the heat exchanger of the MED device can meet the requirements of the relevant regulations and standards, so that it is evaluated that the steam condensate of the heat exchanger of the MED device can be introduced into the desalinated water pipe.

[0225] The preset control index is set in advance according to the requirements of the relevant regulations and standards.

[0226] Specifically, the desalinated water produced by a nuclear energy thermal method seawater desalination coupling device of a certain nuclear power plant is taken as an example to calculate the radioactivity concentration of the desalinated water of the nuclear energy thermal method seawater desalination coupling device, which specifically comprises:

[0227] First, the analysis condition is determined to be normal operation for 364.5 days, and then the first-level alarm threshold of the steam generator leakage rate is superimposed with the intermediate loop heat exchanger break, and the first effect of the MED device is superimposed with the break, and the break duration is 12 hours. Take I-132 and H-3 as examples, the decay constant λ of I-132 is 3.01E-01h -1 , and the decay constant λ of H-3 is 6.59E-06h-1 The radioactivity concentration (A) of steam source item I-131 in the secondary loop of the nuclear power plant is 100 Bq / kg, and that of H-3 is 5000 Bq / kg. The radioactivity concentration (B) of the seawater at the intake point is analyzed to be 1.0E-04 Bq / kg for I-131 and 1 Bq / kg for H-3. Intermediate loop: Leakage rate L under normal operating conditions. C0 The leakage rate L under the broken surface condition is 0.5 t / h. A0 For a capacity of 50 t / h, the flash fraction F of the flash tank HC The concentrations are 0.4 (for iodine) and 1 (for tritium). The normal operating time t1 of the intermediate loop is 364.5 days, the breakage duration t2 is 10 hours, and the water volume W in the intermediate loop is... S 10000m 3 First effect: Seawater flow rate F 0_1 For a capacity of 1000 t / h, the leakage rate L under normal operating conditions C1 The leakage rate L under the broken surface condition is 0.25 t / h. A1 250t / h; Second effect: seawater flow rate F 0_2 For a capacity of 1000 t / h, the leakage rate L under normal operating conditions C2 The leakage rate L under the broken surface condition is 0.15 t / h. A2 For a flow rate of 150 t / h, the third effect is: seawater flow rate F 0_3 Leakage rate L under normal operating conditions of 1000t / h C3 The leakage rate L under the broken surface condition is 0.15 t / h. A3 The desalinated water has a flow rate of 150 t / h and a density D. W The steam-water distribution factor F during the steam condensation process of the MED unit is 1 kg / L. HS Parameters include 0.01 (for iodine) and 1 (for tritium);

[0228] Based on the above model and parameters, the concentration of the intermediate loop fluid is I-132:

[0229] The radioactivity concentration of flash steam is 8.49E+00 Bq / kg, H-3: 2.55E+03 Bq / kg. The radioactivity concentration of flash steam is I-132: 3.40E+00 Bq / kg, H-3: 2.55E+03 Bq / kg. The concentration of steam produced by the first effect of the MED is I-132: 8.50E-04 Bq / kg, H-3: 6.47E+01 Bq / kg; the concentration of steam produced by the second effect is I-132: 1.00E-06 Bq / kg, H-3:

[0230] 1.01E+00Bq / kg, condensate concentration is I-132: 8.50E-04Bq / L, H-3:

[0231] 6.47E+01 Bq / L; the steam concentration produced by the third effect is I-132: 1.00E-06 Bq / kg, H-3: 1.01E+00 Bq / kg, and the concentration of the condensed water is I-132: 1.00E-06 Bq / L, H-3: 1.01E+00 Bq / L; the calculation method of the radioactivity concentration of the steam and the condensed water of the fourth effect, the fifth effect, and the like is the same as that of the third effect.

[0232] Finally, the product fresh water treated by the seawater desalination facility needs to meet the drinking water hygiene indicators, and the radioactivity index requirements of seawater desalination water intake need to be considered. According to the requirements of the water quality indicators and limits in the national standard GB 5749-2022 "Drinking Water Health Standards", the radioactivity index screening value of drinking water is that the total alpha radioactivity is not more than 0.5 Bq / L, and the total beta radioactivity is not more than 1 Bq / L. China has no drinking water radioactivity index for tritium, and can refer to the water quality radioactivity index of tritium given by the European Union, which is not more than 100 Bq / L. According to the calculation results above, the radioactivity concentration of the condensed water produced by the third effect evaporator and the subsequent evaporators is far lower than the radioactivity control index, and can be used for daily drinking. The concentration of H-3 in the condensed water produced by the first effect evaporator is 64.7 Bq / L, which is lower than the tritium provision in the water quality radioactivity index of the European Union, but is far higher than the radioactivity level of background tritium. Whether the first effect condensed water is introduced into the desalination water pipe can be determined according to the use scenario.

[0233] Embodiment 2

[0234] The embodiment provides a method for calculating the radioactivity concentration of an intermediate loop fluid, the intermediate loop being arranged between a main steam system of a nuclear power plant and a MED (Multiple Effect Distillation, referred to as MED) device, the intermediate loop being used for conveying steam produced by flashing of desalted water heated by two-loop steam to the MED device, and collecting condensed water produced by a first effect heat exchanger of the MED device in a condensed water tank, and the intermediate loop being provided with a heat energy conversion device, a flash tank and a condensed water tank.

[0235] The method comprises the following steps:

[0236] Obtaining intermediate loop design parameters and nuclide information, the intermediate loop design parameters and nuclide information comprising a two-loop steam radioactivity concentration, a leakage rate of the intermediate loop heat energy conversion device, a liquid volume of the intermediate loop, a decay constant, a leakage rate of the first effect heat exchanger of the MED device, a cumulative operation time and a flashing share of the flash tank.

[0237] According to the intermediate loop design parameters and the nuclide information, the radioactivity concentration of the gaseous fluid and the liquid fluid of the intermediate loop is calculated respectively.

[0238] The intermediate circuit liquid fluid is intermediate circuit water, because the produced desalinated water is domestic water, and water is used as the medium, which is the most secure.

[0239] The intermediate circuit gaseous fluid is steam obtained by flash tank flashing. The steam here is water vapor, and the intermediate circuit medium is desalinated and deoxygenated water. The main steam is used as the heating gas source, which is heated into steam.

[0240] In addition, the intermediate circuit steam has temperature and pressure requirements. The specific temperature is obtained by software simulation based on the flow rate on both sides of the heat exchanger, the temperature and pressure of the hot side fluid, and the like. The flash fraction F of the gaseous and liquid state carrying radioactive substances under different temperatures and pressures HC is different, but the sensitivity of the flash fraction to temperature and pressure is relatively small, and the change of the flash fraction is small in a large temperature and pressure range.

[0241] The radioactivity concentration of the intermediate circuit water is calculated according to the following formula:

[0242]

[0243] Wherein:

[0244] C0 represents the radioactivity concentration of the intermediate circuit water;

[0245] A represents the radioactivity concentration of the secondary circuit steam;

[0246] L0 represents the leakage rate of the intermediate circuit heat energy conversion device, which is a heat exchanger or a heat pump in the intermediate circuit;

[0247] W S represents the liquid load of the intermediate circuit;

[0248] λ represents the decay constant;

[0249] L1 is the leakage rate of the first-effect heat exchanger of the MED device;

[0250] T is the cumulative running time;

[0251] F HC is the flash fraction of the flash tank;

[0252] The formula for calculating the radioactivity concentration of the steam obtained by the flash tank is as follows:

[0253] S0 = C0·F HC

[0254] Wherein, S0 represents the radioactivity concentration of the steam obtained by the flash tank.

[0255] The calculation of the radioactivity concentration of the intermediate circuit water is obtained based on the nuclide balance equation,

[0256] wherein the nuclide balance equation is obtained based on the flow direction of the medium and the radioactive migration direction, and the nuclide balance equation is as follows:

[0257]

[0258] wherein, represents the derivative of C0 with respect to time t.

[0259] As a specific embodiment, the calculation of the radioactivity concentration of the intermediate loop water comprises:

[0260] the first calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop thermal energy conversion device is in normal condition and the MED device first-effect heat exchanger is in normal condition; or,

[0261] the second calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop thermal energy conversion device is in normal condition and the MED device first-effect heat exchanger is in break condition; or,

[0262] the third calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop thermal energy conversion device is in break condition and the MED device first-effect heat exchanger is in normal condition;

[0263] the fourth calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop thermal energy conversion device is in break condition and the MED device first-effect heat exchanger is in break condition;

[0264] the calculation formula of the first calculation is as follows:

[0265]

[0266] the calculation formula of the second calculation is as follows:

[0267]

[0268] the calculation formula of the third calculation is as follows:

[0269]

[0270] the calculation formula of the fourth calculation is as follows:

[0271]

[0272] wherein,

[0273] L C0 represents the leakage rate of the intermediate loop thermal energy conversion device when the intermediate loop is in normal condition;

[0274] L A0 leakage rate of the intermediate circuit thermal energy conversion device under the intermediate circuit break condition;

[0275] L C1 leakage rate of the MED device first effect heat exchanger under the MED device first effect heat exchanger normal condition;

[0276] L A1 leakage rate of the MED device first effect heat exchanger under the MED device first effect heat exchanger break condition.

[0277] Embodiment 3:

[0278] The embodiment provides a method for calculating the radioactivity concentration of a heat exchanger fluid of a MED device, the MED device being provided with an intermediate circuit between a main steam system of a nuclear power plant, the intermediate circuit being used for transporting steam generated by flashing desalted water heated by two-loop steam in a flash tank to the MED device, and collecting condensate water generated by a first effect heat exchanger of the MED device in a condensate tank, the intermediate circuit being provided with a thermal energy conversion device, the flash tank and the condensate tank, and the method comprising the following steps:

[0279] Step S1: obtaining the radioactivity concentration of the intermediate circuit water by using the method for calculating the radioactivity concentration of the intermediate circuit fluid in the embodiment 1.

[0280] Step S2: obtaining the radioactivity concentration of the fluid of any effect heat exchanger of the MED device according to the radioactivity concentration of the intermediate circuit water; the MED device has i effect heat exchangers, and i is greater than or equal to 2.

[0281] As a specific implementation, the step S2 specifically comprises the following steps:

[0282] Step S21: calculating the radioactivity concentration of seawater of a first effect heat exchanger of the MED device according to the radioactivity concentration of the intermediate circuit water, and calculating the radioactivity concentration of steam of the first effect heat exchanger of the MED device based on the radioactivity concentration of the seawater of the first effect heat exchanger of the MED device.

[0283] The calculation formula of the radioactivity concentration of the seawater of the first effect heat exchanger of the MED device is as follows:

[0284]

[0285] wherein,

[0286] C1 represents the radioactivity concentration of the seawater of the first effect heat exchanger of the MED device;

[0287] C0 represents the radioactivity concentration of the intermediate circuit water;

[0288] L1is the leakage rate of the first-effect heat exchanger of the MED device;

[0289] F 0_1 represents the seawater flow rate of the first-effect heat exchanger;

[0290] B represents the radioactivity concentration of the seawater at the water intake;

[0291] The formula for calculating the radioactivity concentration of the steam of the first-effect heat exchanger of the MED device is as follows:

[0292] S1= C1· F HS

[0293] wherein,

[0294] S1represents the radioactivity concentration of the steam of the first-effect heat exchanger of the MED device;

[0295] F HS is the steam-water distribution factor;

[0296] Step S22: Based on the radioactivity concentration of the seawater of the first-effect heat exchanger of the MED device and the radioactivity concentration of the steam of the first-effect heat exchanger, the radioactivity concentration of the seawater of the second-effect heat exchanger of the MED device and the radioactivity concentration of the steam of the second-effect heat exchanger are calculated; and the same is sequentially performed until the radioactivity concentration of the seawater of the i-effect heat exchanger of the MED device and the radioactivity concentration of the steam of the i-effect heat exchanger are calculated.

[0297] The formula for calculating the radioactivity concentration of the seawater of the i-effect heat exchanger is as follows:

[0298] The formula for calculating the radioactivity concentration of the steam of the i-effect heat exchanger is as follows:

[0299] S i = C i · F HS

[0300] wherein,

[0301] C i is the radioactivity concentration of the seawater in the i-effect heat exchanger;

[0302] C i-1 is the radioactivity concentration of the seawater in the i-1-effect heat exchanger;

[0303] Liis the leakage rate of the i-effect heat exchanger;

[0304] F 0_i is the seawater flow rate of the i-effect heat exchanger;

[0305] S iThe radioactivity concentration of the steam in the i-th heat exchanger.

[0306] As a specific embodiment, the calculation of the radioactivity concentration of the seawater in the i-th heat exchanger comprises:

[0307] The calculation of the radioactivity concentration of the seawater in the i-th heat exchanger in normal operation; or,

[0308] The calculation of the radioactivity concentration of the seawater in the i-th heat exchanger in a break condition;

[0309] The calculation of the radioactivity concentration of the seawater in the i-th heat exchanger in normal operation is as follows

[0310]

[0311] Wherein, L Ci The leakage rate of the i-th heat exchanger in normal operation;

[0312] The calculation of the radioactivity concentration of the seawater in the i-th heat exchanger in a break condition is as follows

[0313]

[0314] Wherein, L Ai The leakage rate of the i-th heat exchanger in a break condition.

[0315] Embodiment 4:

[0316] The present embodiment provides a method for calculating the radioactivity concentration of desalinated water, which is the condensed water output when desalinated by a nuclear energy heat method seawater desalination coupling device;

[0317] The method comprises the following steps:

[0318] Step K1: using the activity concentration calculation method of the MED device heat exchanger fluid of the second aspect to calculate the radioactivity concentration of the MED device heat exchanger fluid;

[0319] Step K2: according to the radioactivity concentration of the MED device heat exchanger fluid, calculate the radioactivity concentration of the MED device heat exchanger steam condensate, thereby obtaining the radioactivity concentration of the desalinated water.

[0320] As a specific embodiment, the step K2 specifically comprises:

[0321] According to the radioactivity concentration of the desalinated water in the MED device heat exchanger, the radioactivity concentration of the MED device second-effect heat exchanger steam condensate is calculated; and so on, the radioactivity concentration of the MED device i-th heat exchanger steam condensate is calculated;

[0322] The calculation formula of the radioactivity concentration of the steam condensate water of the second effect heat exchanger is as follows:

[0323] W2=S1·D W

[0324] Wherein,

[0325] W2 represents the radioactivity concentration of the steam condensate water of the second effect heat exchanger;

[0326] S1 represents the radioactivity concentration of the steam of the first effect heat exchanger of the MED device;

[0327] Dw represents the density of the desalination water;

[0328] The calculation formula of the radioactivity concentration of the steam condensate water of the i-th effect heat exchanger is as follows:

[0329] W i i =S i-1 i-1 ·D W

[0330] Wherein,

[0331] W i i represents the radioactivity concentration of the steam condensate water of the i-th effect heat exchanger;

[0332] S i-1 i-1 represents the radioactivity concentration of the steam of the i-1-th effect heat exchanger of the MED device.

[0333] Embodiment 5:

[0334] The embodiment provides a method for evaluating the radioactivity concentration of desalination water, and the method comprises the following steps:

[0335] The radioactivity concentration of the steam condensate water of the heat exchanger of the MED device is calculated by using the calculation method for the radioactivity concentration of desalination water according to the third aspect;

[0336] According to the radioactivity concentration of the steam condensate water of the heat exchanger of the MED device, it is evaluated whether the steam condensate water of the heat exchanger of the MED device can be introduced into the desalination water pipe.

[0337] As a specific implementation, according to the radioactivity concentration of the steam condensate water of the heat exchanger of the MED device, it is evaluated whether the steam condensate water of the heat exchanger of the MED device can be introduced into the desalination water pipe, and the evaluation specifically comprises:

[0338] The radioactivity concentration of the steam condensate water of the heat exchanger of the MED device is compared with a preset control index to determine whether the radioactivity concentration of the steam condensate water of the heat exchanger of the MED device meets the requirements of relevant regulations and standards:

[0339] If the radioactivity concentration of the MED device heat exchanger steam condensate water is not within the preset control index range, it is determined that the radioactivity concentration of the MED device heat exchanger steam condensate water cannot meet the requirements of relevant regulations and standards, so it is evaluated that the MED device heat exchanger steam condensate water cannot be introduced into the desalinated water pipe; if the radioactivity concentration of the MED device heat exchanger steam condensate water is within the preset control index range, it is determined that the radioactivity concentration of the MED device heat exchanger steam condensate water can meet the requirements of relevant regulations and standards, so it is evaluated that the MED device heat exchanger steam condensate water can be introduced into the desalinated water pipe.

[0340] The preset control index is preset according to the requirements of relevant regulations and standards.

[0341] It can be understood that the above embodiments are only exemplary embodiments for illustrating the principles of the present application, but the present application is not limited thereto. Various modifications and improvements can be made by those of ordinary skill in the art without departing from the spirit and essence of the present application, and these modifications and improvements are also considered to be within the protection scope of the present application.

Claims

1. A method for calculating the radioactivity concentration of an intermediate loop fluid, characterized in that, The intermediate loop is located between the main steam system of the nuclear power plant and the MED unit. The intermediate loop is used to transport the demineralized water generated by the secondary loop steam heating to the MED unit via the steam generated by the flash tank, and the condensate generated by the first effect heat exchanger of the MED unit is collected by the condensate tank. The intermediate loop is equipped with heat energy conversion equipment, flash tank and condensate tank. The method includes the following steps: Step D1: Obtain intermediate loop design parameters and nuclide information; the intermediate loop design parameters and nuclide information include the secondary loop steam radioactivity concentration, the leakage rate of the intermediate loop heat conversion equipment, the liquid volume of the intermediate loop, the decay constant, the leakage rate of the first-effect heat exchanger of the MED device, the cumulative operating time, and the flash fraction of the flash tank. Step D2: Calculate the radioactivity concentrations of the intermediate loop gaseous fluid and liquid fluid based on the intermediate loop design parameters and nuclide information; wherein the intermediate loop liquid fluid is water, and the intermediate loop gaseous fluid is steam obtained from flash evaporation in the flash tank. Calculate the radioactivity concentration of the intermediate loop water according to formula (1): in: C0 represents the radioactivity concentration of the water in the intermediate loop; A represents the radioactivity concentration of the secondary loop steam; L0 represents the leakage rate of the intermediate loop heat energy conversion device; the intermediate loop heat energy conversion device is a heat exchanger or heat pump in the intermediate loop. W S Indicates the liquid volume in the intermediate loop; λ represents the decay constant; L1 is the leakage rate of the first-effect heat exchanger in the MED unit; T represents the cumulative running time; F HC The flash fraction of the flash tank; The formula for calculating the radioactivity concentration of the steam obtained by flash evaporation in the flash tank is as follows: S0=C0·F HC Wherein, S0 represents the radioactivity concentration of the steam obtained by flash evaporation in the flash tank.

2. The method for calculating the radioactivity concentration of the intermediate loop fluid according to claim 1, characterized in that, Before step D1, there is also step D0. Step D0: Construct a nuclide balance equation, which is used to solve for the radioactivity concentration of the water in the intermediate loop; The nuclide balance equation is derived based on the flow direction of the medium and the radioactive migration direction, and is shown in equation (2): in, This indicates that C0 is the derivative of time t.

3. The method for calculating the radioactivity concentration of the intermediate loop fluid according to claim 1, characterized in that, The calculation of the radioactivity concentration of the intermediate loop water includes: When the intermediate loop heat energy conversion equipment is in normal operating condition and the first-effect heat exchanger of the MED device is in normal operating condition, the first calculation of the radioactivity concentration of the intermediate loop water; or, The second calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop heat conversion equipment is in normal operating condition and the first-effect heat exchanger of the MED device is in a broken condition; or, The third calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop heat energy conversion equipment is in a broken working condition and the first-effect heat exchanger of the MED device is in a normal working condition. The fourth calculation of the radioactivity concentration of the intermediate loop water when the intermediate loop heat energy conversion equipment is in a broken condition and the first-effect heat exchanger of the MED device is in a broken condition. The calculation formula for the first calculation is formula (3): The calculation formula for the second calculation is formula (4): The calculation formula for the third calculation is formula (5): The calculation formula for the fourth calculation is formula (6): in, L C0 This indicates the leakage rate of the intermediate circuit heat energy conversion equipment under normal operating conditions. L A0 This indicates the leakage rate of the intermediate circuit heat energy conversion equipment when the intermediate circuit is broken. L C1 This represents the leakage rate of the first-effect heat exchanger in the MED unit under normal operating conditions. L A1 This indicates the leakage rate of the first-effect heat exchanger in the MED unit when the first-effect heat exchanger is in a broken state.

4. A method for calculating the radioactivity concentration of a heat exchanger fluid in a MED device, characterized in that, An intermediate loop is provided between the MED unit and the main steam system of the nuclear power plant. The intermediate loop is used to transport the demineralized water generated by the secondary loop steam heating to the MED unit via the steam generated by the flash tank, and the condensate generated by the first effect heat exchanger of the MED unit is collected by the condensate tank. The intermediate loop is equipped with heat energy conversion equipment, flash tank and condensate tank. The method includes the following steps: Step S1: Using the method for calculating the radioactivity concentration of the intermediate loop fluid according to any one of claims 1 to 3, obtain the radioactivity concentration of the intermediate loop water; Step S2: Based on the radioactivity concentration of the intermediate loop water, obtain the radioactivity concentration of the fluid in any effect heat exchanger of the MED device; the MED device has i effect heat exchangers, where i is greater than or equal to 2.

5. The method for calculating the radioactivity concentration of the heat exchanger fluid in the MED device according to claim 4, characterized in that, Step S2 specifically includes the following steps: Step S21: Calculate the radioactivity concentration of the seawater in the first-effect heat exchanger of the MED device based on the radioactivity concentration of the intermediate loop water; and calculate the radioactivity concentration of the steam in the first-effect heat exchanger of the MED device based on the radioactivity concentration of the seawater in the first-effect heat exchanger of the MED device. The formula for calculating the radioactivity concentration of seawater in the first-effect heat exchanger of the MED device is formula (7): in, C1 represents the radioactivity concentration of the seawater in the first-effect heat exchanger of the MED device; C0 represents the radioactivity concentration of the water in the intermediate loop; L1 is the leakage rate of the first-effect heat exchanger in the MED unit; F 0_1 This indicates the seawater flow rate of the first-effect heat exchanger; B represents the background radioactivity concentration of the seawater at the water intake; The formula for calculating the radioactivity concentration of the steam in the first-effect heat exchanger of the MED device is formula (8): S1=C1·F HS (8) in, S1 represents the radioactivity concentration of the steam in the first-effect heat exchanger of the MED device. F HS For carbonated beverage partition factor; Step S22: Based on the radioactivity concentration of the seawater in the first-effect heat exchanger and the radioactivity concentration of the steam in the first-effect heat exchanger of the MED device, calculate the radioactivity concentration of the seawater in the second-effect heat exchanger and the radioactivity concentration of the steam in the second-effect heat exchanger of the MED device; and so on, until the radioactivity concentration of the seawater in the i-th effect heat exchanger and the radioactivity concentration of the steam in the i-th effect heat exchanger of the MED device are calculated. The formula for calculating the radioactivity concentration of the seawater in the i-th effect heat exchanger is formula (9): The formula for calculating the radioactivity concentration of the steam in the i-th effect heat exchanger is formula (10): S i =C i ·F HS (10) in, C i The radioactivity concentration of seawater in the i-th effective heat exchanger; C i-1 The radioactivity concentration of seawater in the (i-1)th effect heat exchanger; Li represents the leakage rate of the i-th effective heat exchanger; F 0_i The seawater flow rate for the i-th effective heat exchanger; S i The radioactivity concentration of the steam in the i-th effect heat exchanger.

6. The method for calculating the radioactivity concentration of the heat exchanger fluid in a MED device according to claim 5, characterized in that, The calculation of the radioactivity concentration of the seawater in the i-th effect heat exchanger includes: Calculation of the radioactivity concentration of seawater in the i-th effect heat exchanger under normal operating conditions; or, Calculation of radioactivity concentration of seawater in the i-th effective heat exchanger under breach conditions; The radioactivity concentration of the seawater in the i-th effect heat exchanger under normal operating conditions is calculated as shown in formula (11). Among them, L Ci The leakage rate of the i-th effective heat exchanger under normal operating conditions; The radioactivity concentration of the seawater in the i-th effect heat exchanger under the breach condition is calculated as shown in formula (12). Among them, L Ai The leakage rate of the i-th effective heat exchanger under the broken condition.

7. A method for calculating the radioactivity concentration of desalinated seawater, characterized in that, The desalinated water is the condensate output from the desalination of seawater using a nuclear thermal seawater desalination coupling device; The method includes the following steps: Step K1: Calculate the radioactivity concentration of the heat exchanger fluid in the MED device using the activity concentration calculation method described in any one of claims 4 to 6. Step K2: Calculate the radioactivity concentration of the steam condensate in the MED device heat exchanger based on the radioactivity concentration of the fluid in the heat exchanger, thereby obtaining the radioactivity concentration of the desalinated water.

8. The method for calculating the radioactivity concentration of desalinated seawater according to claim 7, characterized in that, In step K2, the radioactivity concentration of the steam condensate in the MED device heat exchanger is calculated based on the radioactivity concentration of the desalinated water in the heat exchanger. This specifically includes: Based on the radioactivity concentration of the desalinated water in the heat exchanger of the MED unit, the radioactivity concentration of the steam condensate in the second-effect heat exchanger of the MED unit is calculated; and so on, the radioactivity concentration of the steam condensate in the i-th-effect heat exchanger of the MED unit is calculated. The formula for calculating the radioactivity concentration of the steam condensate in the second-effect heat exchanger is shown in formula (13): W2=S1·D W (13) in, W2 represents the radioactivity concentration of the steam condensate from the second-effect heat exchanger; S1 represents the radioactivity concentration of the steam in the first-effect heat exchanger of the MED device. Dw represents the density of desalinated water; The formula for calculating the radioactivity concentration of the steam condensate of the i-th effect heat exchanger is as follows: (14) W i =S i-1 ·D W (14) in, W i This represents the radioactivity concentration of the steam condensate from the i-th effective heat exchanger. S i-1 This indicates the radioactivity concentration of the steam in the (i-1)th effect heat exchanger of the MED device.

9. A method for assessing the radioactivity concentration of desalinated seawater, characterized in that, The method includes the following steps: The radioactivity concentration of the desalinated seawater is calculated using the method described in claim 7 or 8. Based on the radioactivity concentration of the steam condensate from the heat exchanger of the MED unit, assess whether the steam condensate from the heat exchanger of the MED unit can be introduced into the desalination water pipe.

10. The method for assessing the radioactivity concentration of desalinated seawater according to claim 9, characterized in that, The assessment of whether the steam condensate from the MED unit's heat exchanger can be introduced into the desalination water pipe, based on the radioactivity concentration of the heat exchanger steam condensate, specifically includes: The radioactivity concentration of the steam condensate from the MED unit's heat exchanger was compared with preset control targets to determine whether the radioactivity concentration of the steam condensate from the MED unit's heat exchanger met the requirements of relevant regulations and standards. If the radioactivity concentration of the steam condensate from the heat exchanger of the MED unit is not within the preset control index range, it is assessed that the steam condensate from the heat exchanger of the MED unit cannot be introduced into the desalination water pipe; if the radioactivity concentration of the steam condensate from the heat exchanger of the MED unit is within the preset control index range, it is assessed that the steam condensate from the heat exchanger of the MED unit can be introduced into the desalination water pipe.

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