Method for removing hydrogen after hydrogen rebound of primary loop in descending period of nuclear power plant during overhaul

Abstract

The invention belongs to the technical field of pressurized water reactor nuclear power plants, and particularly relates to a hydrogen removal method after rebounding of primary loop hydrogen in a descending period of overhaul of a nuclear power plant, and the method comprises the following steps: step 1, evaluating a descent rate of dissolved hydrogen, and determining a hydrogen removal mode; 2, confirming conditions before chemical dehydrogenation; 3, calculating and controlling the addition amount of hydrogen peroxide, and carrying out chemical hydrogen removal; and step 4, determining a dehydrogenation mode according to the dissolved hydrogen content of the main system until the dissolved hydrogen content of the main system meets the requirement. According to the method, the content of dissolved hydrogen in a primary loop can be rapidly eliminated, the main line occupying time is greatly shortened, and generation of radioactive gas is reduced; and meanwhile, a hydrogen removal scheme of adding a small amount of hydrogen peroxide for multiple times is adopted, so that the risk of hydrogen explosion caused by large rise of dissolved oxygen in a primary loop due to one-time excessive addition of hydrogen peroxide is avoided, and safe, economical and effective hydrogen removal is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of pressurized water reactor nuclear power plants, and particularly relates to a method for removing hydrogen after hydrogen rebound in the primary loop during the overhaul of a nuclear power plant when the power is being reduced. Background Art

[0002] In a nuclear reaction pressurized water reactor system, when the reactor is operating at power, the primary coolant (RCP) is affected by irradiation, causing water to decompose into hydrogen and oxygen. The oxygen produced by this decomposition may damage the integrity of the structural materials and increase the corrosion risk of the equipment. To solve this problem, hydrogen is added to the primary coolant to dissolve a certain amount of hydrogen in the water. Under normal power operation conditions, the expected value of the dissolved hydrogen control content in the main system is 25 - 35 ml / L.H2O, and the limit is 20 - 50 ml / L.H2O.

[0003] Currently, 7 days before the power reduction during the overhaul, the vapor space of the pressurizer (PZR) is connected to the pre-storage tank (TEP001BA or TEP008BA) of the boron recovery system for scavenging, and during the subsequent process of temperature and pressure reduction, nitrogen purging of relevant containers is used to reduce the dissolved hydrogen content in the main system. At different stages of the power reduction during the overhaul, the control targets for the concentration of dissolved hydrogen will be different. 24 hours before the power reduction, the dissolved hydrogen concentration in the main loop and the pressurizer is controlled between 15 ml / L.H2O and 20 ml / L.H2O. As the overhaul progresses, this concentration gradually decreases until it meets the index of ≤3 ml / L.H2O before oxidation operation, thus ensuring the safety requirements during the overhaul. However, before oxidation operation, the water level in the primary loop needs to be raised to submerge the vapor space of the pressurizer to eliminate the gas space inside the pressurizer. In the vapor space of the pressurizer, the hydrogen in the PZR gas phase will dissolve into the main system, resulting in the frequent occurrence of hydrogen rebound in the main system. Currently, after hydrogen rebound occurs in each power plant, generally physical methods such as supplementing nitrogen through the volume control tank (RCV002BA) for replacement and starting the degassing tower (TEP001 / 002DZ) of the boron recovery system to remove hydrogen are used to reduce the dissolved hydrogen content. However, this traditional method is inefficient and is only suitable for cases where the index exceeds ≤3 ml / L.H2O by a small amount. If the excess is large, using this method will cause a delay in the oxidation operation work during the overhaul, greatly affecting the main line time of the unit's power reduction and significantly increasing the cost; at the same time, long-term purging will greatly increase the generation of radioactive waste gas, bringing great pressure to emissions. Summary of the Invention

[0004] The object of the present invention is to provide a method for removing hydrogen after the hydrogen rebound in the primary circuit during the down period of the nuclear power plant overhaul. This method can quickly eliminate the dissolved hydrogen content in the primary circuit, greatly shorten the time occupying the main line, and reduce the generation of radioactive gases. At the same time, the hydrogen removal scheme of adding hydrogen peroxide in small amounts and multiple times is adopted to avoid a large increase in the dissolved oxygen in the primary circuit caused by excessive addition of hydrogen peroxide at one time, increase the risk of hydrogen explosion, and achieve safe, economical and effective hydrogen removal.

[0005] The technical solution for achieving the object of the present invention: A method for removing hydrogen after the hydrogen rebound in the primary circuit during the down period of the nuclear power plant overhaul, the method comprising: Step 1, evaluate the decline rate of dissolved hydrogen and determine the hydrogen removal method; Step 2, confirm the conditions before chemical hydrogen removal; Step 3, calculate and control the addition amount of hydrogen peroxide and perform chemical hydrogen removal; Step 4, determine the hydrogen removal method according to the dissolved hydrogen content in the main system until the dissolved hydrogen content in the main system meets the requirements.

[0006] The said Step 1 includes: Step 1.1, calculate the expected time for the dissolved hydrogen in the primary circuit to decline by using the degassing method combining TEP001 / 002DZ degassing + RCV002BA purging; Step 1.2, compare the expected time for the dissolved hydrogen in the primary circuit to decline with the reserved time of the critical path and determine the hydrogen removal method.

[0007] The calculation formula for the expected time for the dissolved hydrogen to decline in the said Step 1.1 is: T = (V / V1×ln C0 / C) / η In the formula, T: the expected time for the dissolved hydrogen in the primary circuit to decline after the steam cavity of the pressurizer is extinguished, h; V: the water inventory in the primary circuit after the residual heat removal system is incorporated, m 3 ; V1: the letdown flow rate of the chemical and volume control system, m 3 / h; C0: the current dissolved hydrogen content in the primary circuit, ml / L.H2O; C: the target dissolved hydrogen content in the primary circuit, ml / L.H2O; η: the degassing efficiency; if only RCV002BA purging is carried out, this efficiency is set to 60%; it can also be calculated according to the actual purging situation.

[0008] The said Step 1.2 is specifically: After the hydrogen rebound occurs in the unit, according to the degassing method combining "TEP001 / 002DZ degassing + RCV002BA purging", if the expected time for the dissolved hydrogen in the primary circuit to decrease greatly exceeds the reserved time of the critical path, chemical hydrogen removal is carried out; After the hydrogen rebound occurs in the unit, according to the degassing method combining "TEP001 / 002DZ degassing + RCV002BA purging", if the expected time for the dissolved hydrogen in the primary circuit to decrease is within the reserved time of the critical path, "TEP001 / 002DZ degassing + RCV002BA purging" hydrogen removal is carried out.

[0009] The said step 2 includes: Step 2.1, confirmation of the instrument status before chemical hydrogen removal; Step 2.1.1, confirm that the on-line dissolved hydrogen meter in the primary circuit is available; Step 2.1.2, confirm that the portable dissolved hydrogen meter has been connected to the primary circuit coolant and can continuously monitor the hydrogen content in the primary circuit coolant; Step 2.1.3, confirm that the portable dissolved oxygen meter has been connected to the primary circuit coolant and can continuously monitor the oxygen content in the primary circuit coolant; Step 2.2, confirmation of the primary circuit temperature and hydrogen content before chemical hydrogen removal; Step 2.2.1, confirm that the primary circuit is at a temperature plateau of 80°C to 90°C; Step 2.2.2, confirm the hydrogen content in the relevant containers of the primary circuit: the H2 content in the pressurizer loop, pressurizer relief tank, reactor coolant drain tank, volume control tank, pre-storage tank before the boron recovery system, and gas cavity of the degassing tower in the boron recovery system is <2%.

[0010] The said step 3 includes: Step 3.1, calculation of the hydrogen peroxide addition amount; Step 3.2, determine the hydrogen peroxide addition amount, add hydrogen peroxide, and carry out chemical hydrogen removal.

[0011] The calculation formula for the hydrogen peroxide addition amount in the said step 3.1 is: In the formula, V2: the volume of hydrogen peroxide required at normal temperature, L; C0: the current dissolved hydrogen content in the primary circuit, ml / L.H2O; C: the target dissolved hydrogen content in the primary circuit, ml / L.H2O; V: the water inventory in the primary circuit after the residual heat removal system is incorporated, m 3 ; M: the relative molecular mass of hydrogen peroxide, g / mol; F: the molar volume of gas, 22.4 L / mol; ρ: The density of hydrogen peroxide, which is 1.1 kg / L under normal temperature and pressure; η2: The mass percentage of hydrogen peroxide, %.

[0012] The specific content of step 3.2 is as follows: If the calculated result of the volume V2 of hydrogen peroxide ≤ 6.0 L, then add hydrogen peroxide according to the actual calculated result; If the calculated result of the volume V2 of hydrogen peroxide > 6.0 L, then add 6.0 L of hydrogen peroxide; After adding hydrogen peroxide, continue to use "TEP001 / 002DZ degassing + RCV002BA purging". After reacting for a period of time, when the dissolved hydrogen content in the primary system decreases slowly and reaches basic stability, measure the dissolved hydrogen content in the primary system.

[0013] The specific content of step 4 is as follows: If the dissolved hydrogen content in the primary system measured in step 3.2 ≤ 3 ml / L.H2O, then stop adding hydrogen peroxide; if the dissolved hydrogen content in the primary system measured in step 3.2 > 3 ml / L.H2O, then according to the dissolved hydrogen content in the primary loop, repeat steps 1 - 3, and select physical purging such as "TEP001 / 002DZ degassing + RCV002BA purging" or chemical hydrogen removal until the dissolved hydrogen content in the primary system ≤ 3 ml / L.H2O.

[0014] The beneficial technical effects of the present invention are as follows: 1. The present invention uses hydrogen peroxide as a chemical additive to eliminate the excess dissolved hydrogen content after the steam - extinguishing cavity of the primary circuit pressurizer. Compared with the existing container purging method, it greatly shortens the time occupying the main line; at the same time, adopting the hydrogen - removal scheme of adding hydrogen peroxide in small amounts and multiple times can avoid a large increase in dissolved oxygen in the primary circuit caused by excessive addition of hydrogen peroxide at one time and increase the risk of hydrogen explosion, realizing safe, economical and effective hydrogen removal.

[0015] 2. Based on the principle that hydrogen reacts with hydrogen peroxide to generate water, the present invention does not generate any radioactive waste gas during the hydrogen - removal process and has no impact on emissions.

[0016] 3. The present invention is simple to operate and has strong applicability, and can be widely promoted and used. Description of the Drawings

[0017] Figure 1 It is a process flow chart of a hydrogen - removal method after the hydrogen rebound in the primary circuit during the downward phase of the nuclear power plant overhaul provided by the present invention. Detailed Embodiments

[0018] The following further elaborates the present invention in detail with reference to the drawings and embodiments.

[0019] A hydrogen - removal method after the hydrogen rebound in the primary circuit during the downward phase of the nuclear power plant overhaul provided by the present invention includes: Step 1. Evaluate the decreasing rate of dissolved hydrogen and determine the de-hydrogenation method; Step 1.1. Calculate the expected time for the dissolved hydrogen in the primary circuit to decrease when using the degassing method of combining TEP001 / 002DZ degassing + RCV002BA purging; After the steam space of the pressurizer is flooded and the hydrogen rebound occurs in the unit, for the purging method of the dissolved hydrogen in the primary circuit, according to the degassing method of combining "TEP001 / 002DZ degassing + RCV002BA purging", the calculation formula for the time required for the dissolved hydrogen in the primary circuit to decrease from the initial content to the target content (i.e., the expected time for the dissolved hydrogen to decrease) is: T = (V / V1×ln C0 / C) / η Formula (1) In the formula, T: The expected time for the dissolved hydrogen in the primary circuit to decrease after the steam cavity of the pressurizer is extinguished, h; V: The water inventory in the primary circuit after the Residual Heat Removal System (RRA) is incorporated, m 3 ; V1: The letdown flow rate of the Chemical and Volume Control System (RCV), m 3 / h; C0: The current dissolved hydrogen content in the primary circuit, ml / L.H2O (STP); C: The target dissolved hydrogen content in the primary circuit, ml / L.H2O (STP); η: The degassing efficiency; if only RCV002BA purging is carried out, this efficiency is set to 60%; it can also be calculated according to the actual purging situation.

[0020] Step 1.2. Compare the expected time for the dissolved hydrogen in the primary circuit to decrease with the reserved time of the critical path and determine the de-hydrogenation method; After the hydrogen rebound occurs in the unit, according to the degassing method of combining "TEP001 / 002DZ degassing + RCV002BA purging", if the time required for the dissolved hydrogen in the primary circuit to decrease from the initial content to the target content (i.e., the expected time for the dissolved hydrogen to decrease) greatly exceeds the reserved time of the critical path, chemical de-hydrogenation is carried out; After the hydrogen rebound occurs in the unit, according to the degassing method of combining "TEP001 / 002DZ degassing + RCV002BA purging", if the time required for the dissolved hydrogen in the primary circuit to decrease from the initial content to the target content (i.e., the expected time for the dissolved hydrogen to decrease) is within the reserved time of the critical path (acceptable), then "TEP001 / 002DZ degassing + RCV002BA purging" de-hydrogenation is carried out.

[0021] Among them, the target dissolved hydrogen content of the primary coolant is generally that the dissolved hydrogen concentration reaches the descending parameter requirement (≤3.0 ml / L.H2O (STP)).

[0022] Step 2. Confirm the conditions before chemical de-hydrogenation; Step 2.1. Confirmation of Instrument Status before Chemical Dehydrogenation; Step 2.1.1. Confirm that the in-loop dissolved hydrogen meter (REN013MG) is available; Step 2.1.2. Confirm that the portable dissolved hydrogen meter has been connected to the RCP and can continuously monitor the hydrogen content of the RCP; Step 2.1.3. Confirm that the portable dissolved oxygen meter has been connected to the RCP and can continuously monitor the oxygen content of the RCP.

[0023] Step 2.2. Confirmation of the Primary Loop Temperature and Hydrogen Content before Chemical Dehydrogenation; Step 2.2.1. Confirm that the primary loop is at a temperature plateau of 80°C to 90°C; Step 2.2.2. Confirm the hydrogen content in the relevant primary loop containers: the hydrogen content in the PZR annulus, the PZR relief tank (RCP002BA), the reactor coolant drain tank (RPE001BA), the volume control tank (RCV002BA), the pre-storage tank of the boron recovery system (TEP001BA / 008BA), and the degassing tower of the boron recovery system (TEP001DZ / 002DZ) gas chamber is <2%.

[0024] Step 3. Calculate and Control the Hydrogen Peroxide Dosage, and Conduct Chemical Dehydrogenation; Step 3.1. Calculate the Hydrogen Peroxide Dosage; Utilize the characteristics of hydrogen peroxide. Under the above-mentioned conditions being met, inject a certain amount of hydrogen peroxide into the main system for chemical dehydrogenation. The specific calculation formula for the hydrogen peroxide dosage is as follows: Formula (2) In the formula, V2: The volume of hydrogen peroxide required at room temperature, L; C0: The current dissolved hydrogen content in the primary loop, ml / L.H2O; C: The target dissolved hydrogen content in the primary loop, ml / L.H2O; V: The water inventory in the primary loop after the RRA is incorporated, m 3 ; M: The relative molecular mass of hydrogen peroxide, g / mol; F: The molar volume of gas, 22.4 L / mol; ρ: The density of hydrogen peroxide, 1.1 kg / L (at room temperature and normal pressure); η2: The mass percentage of hydrogen peroxide, %.

[0025] Step 3.2. Determine the Hydrogen Peroxide Dosage, Add Hydrogen Peroxide, and Conduct Chemical Dehydrogenation; To prevent the risk of hydrogen explosion caused by a violent reaction between hydrogen peroxide and hydrogen after hydrogen peroxide is added to the primary circuit, the hydrogen removal plan is implemented according to the principle of "gradual, small amount, multiple times", avoiding adding a large amount or excessive amount of hydrogen peroxide at one time.

[0026] The hydrogen removal plan adopts the principle of "gradual, small amount, multiple times", specifically: by calculating the required amount of hydrogen peroxide to be added before each addition and evaluating the amount of hydrogen peroxide added each time, to avoid excessive addition at one time. If too much hydrogen peroxide is added at one time, it will cause a significant increase in the dissolved oxygen in the primary circuit, and hydrogen-oxygen mixing may occur in the containers connected to the main system. At the same time, hydrogen peroxide itself is also a strong oxidant and will react violently with hydrogen under certain conditions, posing a risk of hydrogen explosion.

[0027] In the specific implementation process, if too much hydrogen peroxide is added at one time (exceeding 6.0 L), it will cause a significant increase in the dissolved oxygen in the primary circuit, and hydrogen-oxygen mixing may occur in the containers connected to the main system. At the same time, hydrogen peroxide itself is also a strong oxidant and will react violently with hydrogen under certain conditions, posing a risk of hydrogen explosion. Therefore, the maximum value of the one-time addition amount of hydrogen peroxide used to remove dissolved hydrogen by the hydrogen peroxide method after hydrogen rebound in the unit is 6.0 L.

[0028] If the calculated result of the volume V2 of hydrogen peroxide ≤ 6.0 L, then add hydrogen peroxide according to the actual calculated result; If the calculated result of the volume V2 of hydrogen peroxide > 6.0 L, then add 6.0 L of hydrogen peroxide.

[0029] After adding hydrogen peroxide, continue to use "TEP001 / 002DZ degassing + RCV002BA purging". After reacting for a period of time, when the dissolved hydrogen content in the main system decreases slowly and reaches a basic stability, measure the dissolved hydrogen content in the main system.

[0030] Step 4: Determine the hydrogen removal method according to the dissolved hydrogen content in the main system until the dissolved hydrogen content in the main system meets the requirements; If the dissolved hydrogen content in the main system measured in step 3.2 ≤ 3 ml / L.H2O, then stop adding hydrogen peroxide; if the dissolved hydrogen content in the main system measured in step 3.2 > 3 ml / L.H2O, then according to the dissolved hydrogen content in the primary circuit, repeat steps 1-3, and select "TEP001 / 002DZ degassing + RCV002BA purging" physical purging or chemical hydrogen removal until the dissolved hydrogen content in the main system ≤ 3 ml / L.H2O.

[0031] Example 1 In February 2024, during the 7th 207 major overhaul of Unit 2 of Fangjiashan Nuclear Power Plant in Qinshan Nuclear Power, the chemical hydrogen removal and control method after hydrogen rebound in the primary circuit was as follows Figure 1 shown, including: At 17:00 on February 22, 2024, after the vapor removal cavity of the pressurizer was completed, the dissolved hydrogen content in the primary system increased from 2.2 ml / L.H2O at 16:00 to 9.9 ml / L.H2O, showing a hydrogen rebound phenomenon. After the operating personnel determined the hydrogen rebound, they increased the purging work of the relevant containers in the primary loop. At 0:00 on the 23rd, the dissolved hydrogen content in the primary system decreased to 7.2 ml / L.H2O. At this time, purging had been carried out for 7 hours, and there was still a gap from the specification value of ≤3 ml / L.H2O required before oxidation operation.

[0032] Step 1: Evaluate the rate of decrease of dissolved hydrogen and determine the de-hydrogenation method; Step 1.1: Calculate the expected time for the decrease of dissolved hydrogen in the primary loop using the degassing method combining TEP001 / 002DZ degassing + RCV002BA purging; ① The average efficiency during purging is obtained through the conversion formula (1) as: η = (V / V1×ln C0 / C) / T = 98.8% In the formula, T: The time for the decrease of dissolved hydrogen in the primary loop after the vapor removal cavity of the pressurizer, 7h; V: After RRA is incorporated into the primary loop, the water inventory in the primary loop is 300 m 3 ; V1: The average RCV letdown flow rate, 13.8 m 3 / h; C0: The current dissolved hydrogen content in the primary loop, 9.9 ml / L.H2O (STP); C: The target dissolved hydrogen content in the primary loop, 7.2 ml / L.H2O (STP); ② Calculated at a purging efficiency of 98.8%, the expected time to reach the target specification value of dissolved hydrogen is: T = (V / V1×ln C0 / C) / η = 19.26 h In the formula, V: After RRA is incorporated into the primary loop, the water inventory in the primary loop is 300 m 3 ; V1: The RCV letdown flow rate, 13.8 m 3 / h; C0: The current dissolved hydrogen content in the primary loop, 7.2 ml / L.H2O (STP); C: The target dissolved hydrogen content in the primary loop, 3.0 ml / L.H2O (STP); η: The degassing efficiency is 98.8%.

[0033] Step 1.2: Compare the expected time for the decrease of dissolved hydrogen in the primary loop with the reserved time of the critical path to determine the de-hydrogenation method; As calculated in Step 1.1, it will take at least 19.26 hours to reduce the dissolved hydrogen content to ≤3.0 ml / L.H2O by purging, which greatly exceeds the reserved time of the critical path. Meanwhile, a large amount of radioactive waste gas will be generated. Therefore, the following chemical hydrogen removal plan is adopted.

[0034] Step 2: Confirmation of conditions before chemical hydrogen removal; Step 2.1: Confirmation of instrument status before chemical hydrogen removal Step 2.1.1: Confirm that the in-loop online dissolved hydrogen meter REN013MG is available; Step 2.1.2: Confirm that the portable dissolved hydrogen meter is connected to the RCP and can continuously monitor the hydrogen content of the RCP; Step 2.1.3: Confirm that the portable dissolved oxygen meter is connected to the RCP and can continuously monitor the oxygen content of the RCP.

[0035] Step 2.2: Confirmation of the in-loop temperature and hydrogen content before chemical hydrogen removal Step 2.2.1: Confirm that the in-loop is at a temperature platform of 80°C to 90°C; Step 2.2.2: Confirm the hydrogen content in the relevant in-loop containers: At 0:00 on the 23rd, sampling and analysis showed that the H2 content in the PZR annulus, RCP002BA, RPE001BA, RCV002BA, TEP001BA / 008BA, and the gas cavities of TEP001DZ / 002DZ was <2%, meeting the conditions.

[0036] Step 3: Calculation and control of the hydrogen peroxide addition amount for chemical hydrogen removal; Step 3.1: Calculation of the hydrogen peroxide addition amount; Utilizing the characteristics of hydrogen peroxide, under the above-mentioned satisfied conditions, a certain amount of hydrogen peroxide is injected into the main system for chemical hydrogen removal. The specific calculation formula for the hydrogen peroxide addition amount is as follows: In the formula, V2: The volume of hydrogen peroxide required at normal temperature, L; C0: The current in-loop dissolved hydrogen content, 7.2 ml / L.H2O; C: The target in-loop dissolved hydrogen content, 2.8 ml / L.H2O (STP); V: After the RRA is incorporated into the in-loop, the in-loop water inventory is 300 m 3 ; M: The relative molecular mass of hydrogen peroxide, 34 g / mol; F: The molar volume of gas, 22.4 L / mol; ρ: The density of hydrogen peroxide, 1.1 kg / L (under normal temperature and pressure); η2: Mass percentage of hydrogen peroxide, 30%.

[0037] Step 3.2: Determine the addition amount of hydrogen peroxide, add hydrogen peroxide, and perform chemical hydrogen removal. According to the principle of "step - by - step, small - amount, multiple - times" addition, if the calculated result of V2 is 6.1L > 6.0L, then add 6.0L.

[0038] At 0:57 on February 23rd, 6L of hydrogen peroxide was injected into the primary loop for chemical hydrogen removal work.

[0039] Step 4: Determine the hydrogen removal method according to the dissolved hydrogen content in the main system until the dissolved hydrogen content in the main system meets the requirements. At 1:30, the dissolved hydrogen content in the main system decreased to 2.87 ml / L.H2O, meeting the index before oxidation operation (≤3 ml / L.H2O). Using this method (which takes 33 minutes) is more than 30 times more efficient than using the traditional physical purging method (which takes 19.26 hours) in reducing dissolved hydrogen, greatly shortening the occupation time of the main line and reducing the emission of radioactive waste gas.

[0040] The present invention has been described in detail above in conjunction with the drawings and embodiments. However, the present invention is not limited to the above - mentioned embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention. Contents not described in detail in the present invention can all adopt the prior art.

Claims

1. A method for removing hydrogen from a primary circuit after hydrogen rebound during a nuclear power plant overhaul downtime, characterized in that: The method comprises: Step 1, evaluate the decline rate of dissolved hydrogen and determine the hydrogen removal method; Step 2: Confirmation of pre-conditions for chemical dehydrogenation; Step 3: Calculate and control the amount of hydrogen peroxide added to perform chemical dehydrogenation; Step 4: Determine the hydrogen removal method according to the dissolved hydrogen content of the main system until the dissolved hydrogen content of the main system meets the requirements.

2. The method for removing hydrogen from a primary circuit after hydrogen rebound during a nuclear power plant overhaul downtime according to claim 1, characterized in that: The step 1 comprises: Step 1.1, calculate the expected time for the dissolved hydrogen in the first circuit to decrease by using the degassing method of TEP001 / 002DZ degassing + RCV002BA purging; Step 1.2: Compare the expected time for the dissolved hydrogen in a circuit to decrease with the reserved time of the critical path and determine the method for removing hydrogen.

3. The method for removing hydrogen from a primary circuit after hydrogen rebound during a nuclear power plant overhaul downtime according to claim 2, characterized in that: The calculation formula for the expected time for dissolved hydrogen to decrease in step 1.1 is: T = (V / V1×ln C0 / C) / η In the formula, T: expected time for dissolved hydrogen in the primary circuit to decrease after the steam chamber of the pressurizer is extinguished, h; V: Water volume of the first circuit after the waste heat removal system is incorporated, m 3 ; V1: chemical and volume control system discharge flow, m 3 / h; C0: current dissolved hydrogen content in the first circuit, ml / L.H2O; C: target content of dissolved hydrogen in the first circuit, ml / L.H2O; η: Degassing efficiency; if only RCV002BA is used for purging, this efficiency is set to 60%; it can also be calculated based on the actual purging situation.

4. The method for removing hydrogen from a primary circuit after hydrogen rebound during a nuclear power plant overhaul downtime according to claim 3, characterized in that: The step 1.2 is specifically as follows: After hydrogen rebound occurs in the unit, according to the degassing method combined with "TEP001 / 002DZ degassing + RCV002BA purging", if the expected time for the primary circuit dissolved hydrogen to decrease greatly exceeds the critical path reserved time, chemical dehydrogenation is performed; After hydrogen rebound occurs in the unit, the degassing method of "TEP001 / 002DZ degassing + RCV002BA purging" is used. If the expected time for the dissolved hydrogen in the first circuit to decrease is within the reserved time range of the critical path, "TEP001 / 002DZ degassing + RCV002BA purging" is used to remove hydrogen.

5. The method for removing hydrogen from a primary circuit after hydrogen rebound during a nuclear power plant overhaul downtime according to claim 1, characterized in that: The step 2 comprises: Step 2.1, confirm the instrument status before chemical dehydrogenation; Step 2.1.1, confirm that the primary circuit online dissolved hydrogen meter is available; Step 2.1.2, confirm that the portable dissolved hydrogen meter has been connected to the primary coolant circuit and can continuously monitor the hydrogen content of the primary coolant circuit; Step 2.1.3, confirm that the portable dissolved oxygen meter has been connected to the primary coolant circuit and can continuously monitor the oxygen content of the primary coolant circuit; Step 2.2: Confirm the temperature and hydrogen content of the first circuit before chemical dehydrogenation; Step 2.2.1, confirm that the primary circuit is at the temperature platform of 80℃~90℃; Step 2.2.

2. Confirm the hydrogen content in the related containers of the primary circuit: the H2 content in the pressurizer ring pipe, pressurizer pressure relief box, reactor coolant drain tank, volume control box, boron recovery system front storage tank, and boron recovery system degassing tower gas cavity is <2%.

6. The method for removing hydrogen from a primary circuit after hydrogen rebound during a nuclear power plant overhaul downtime according to claim 1, characterized in that: The step 3 comprises: Step 3.1, calculation of the amount of hydrogen peroxide added; Step 3.2: Determine the amount of hydrogen peroxide to be added, add hydrogen peroxide, and perform chemical dehydrogenation.

7. A method for removing hydrogen from a primary circuit after hydrogen rebound during a nuclear power plant overhaul downtime according to claim 6, characterized in that: The calculation formula for the amount of hydrogen peroxide added in step 3.1 is: In the formula, V2: volume of hydrogen peroxide required at room temperature, L; C0: current dissolved hydrogen content in the first circuit, ml / L.H2O; C: target content of dissolved hydrogen in the first circuit, ml / L.H2O; V: Water volume of the first circuit after the waste heat removal system is incorporated, m 3 ; M: relative molecular mass of hydrogen peroxide, g / mol; F: gas molar volume, 22.4 L / mol; ρ: Density of hydrogen peroxide, 1.1 kg / L at room temperature and pressure; η2: mass percentage of hydrogen peroxide, %.

8. A method for removing hydrogen from a primary circuit after hydrogen rebound during a nuclear power plant overhaul downtime according to claim 7, characterized in that: The step 3.2 is specifically as follows: If the calculated volume of hydrogen peroxide V2 is ≤6.0L, add hydrogen peroxide according to the actual calculated result; If the calculated volume of hydrogen peroxide V2 is greater than 6.0L, add 6.0L of hydrogen peroxide; After adding hydrogen peroxide, continue to use "TEP001 / 002DZ degassing + RCV002BA purging". After a period of reaction, when the dissolved hydrogen content in the main system decreases slowly and reaches a basic stability, measure the dissolved hydrogen content in the main system.

9. A method for removing hydrogen from a primary circuit after hydrogen rebound during a nuclear power plant overhaul downtime according to claim 8, characterized in that: The step 4 is specifically as follows: if the dissolved hydrogen content of the main system measured in step 3.2 is ≤3 ml / L.H2O, stop adding hydrogen peroxide; if the dissolved hydrogen content of the main system measured in step 3.2 is >3 ml / L.H2O, repeat steps 1-3 according to the dissolved hydrogen content of the main loop, and select "TEP001 / 002DZ degassing + RCV002BA purging" physical purging or chemical dehydrogenation until the dissolved hydrogen content of the main system is ≤3 ml / L.H2O.

Images