Novel high-temperature gas cooled reactor cabin cooling system chemical additive process

Abstract

The invention belongs to the technical field of nuclear power chemistry, and particularly relates to a novel chemical additive process for a high-temperature gas cooled reactor cabin cooling system. Lithium hydroxide 7LiOH. H2O and hydrazine hydrate are added into the primary loop cabin cooling system through a nuclear island dosing device, and the concentration of lithium hydroxide 7LiOH. H2O and the concentration of hydrazine hydrate in the primary loop cabin cooling system are controlled in a coordinated manner, so that the requirement that the pH value of cooling water of the primary loop cabin cooling system is controlled to be 8.0-9.0 is met. The characteristics of lithium hydroxide 7LiOH. H2O are fully utilized to improve the pH value of cooling water of a primary loop cabin cooling system, hydrazine hydrate is added to maintain the reducing environment in the system, reduce the corrosion rate of low-carbon steel, reduce the radioactive dose in the primary loop cabin cooling water, reduce the generation amount of radioactive wastewater, reduce the irradiation dose of personnel and improve the operation safety of a nuclear power plant.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear power chemistry, and particularly relates to a chemical additive process for a new type of high-temperature gas-cooled reactor compartment cooling system. Background Art

[0002] The primary circuit compartment cooling system includes a reactor compartment cooling system and a shield cooling water system.

[0003] The main functions of the reactor compartment cooling system are: (1) During normal operation of the reactor, it performs the reactor compartment cooling function and, together with the shield cooling water system, ensures that the concrete temperature is below the specified limit. (2) Under accident conditions, it removes the residual heat of the reactor from the reactor compartment and transports it to the ultimate heat sink, ensuring that the temperature of the in-core components and the reactor pressure vessel is below the specified limit.

[0004] The reactor compartment cooling system adopts a passive design concept, relying on radiation, heat conduction, and natural convection to remove heat, and can discharge heat to the ultimate heat sink - the atmosphere without relying on external power. During normal operation of the reactor, it performs the reactor compartment cooling function, and after a reactor trip, it can continue to operate to remove heat without any operation.

[0005] The functions of the shield cooling water system are: (1) During normal operation of the reactor, ensure that the temperature of the compartment concrete (except for the local areas described in item (2)) does not exceed 65 °C; (2) During normal operation of the reactor, ensure that the temperature of the local areas such as penetrations, holes, and embedded parts on the compartment concrete does not exceed 93 °C; (3) During normal operation of the reactor, ensure that the atmosphere temperature in the upper part (above the top insulation layer) of the reactor compartment is below 90 °C.

[0006] The radioactive source in the primary circuit compartment cooling system is the induced radioactivity generated by the water and its impurities in the system under the action of neutrons escaping from the reactor pressure vessel. The impurities in the water are mainly the corrosion products on the surface of the cooler material.

[0007] Since the neutron fluence rate in the reactor compartment cooling water system is the highest and the water in it is in a closed loop, the radioactive concentration in the water is higher than that in other coolers. According to the calculation of the reactor main body shielding, the average thermal neutron fluence rate in the water of the reactor compartment cooling water system can be taken as 6.8×10 7 n / (cm 2 ·s). Therefore, the primary circuit compartment cooling system is subject to a strong neutron radiation field.

[0008] Currently, sodium molybdate and TTA are added in the design documents of the high-temperature reactor primary circuit compartment cooling system. In the environment of the neutron radiation field, sodium ions undergo a nuclear activation reaction with neutrons, and the reaction formula is:

[0009] Na 23+n → Na 24 +γ

[0010] Na 24 → Mg 24 +β + +v e

[0011] The activation reaction of sodium with neutrons is a nuclear reaction in which a sodium atomic nucleus captures a free neutron, becoming unstable and transforming into another element or isotope. When sodium (especially the sodium-23 isotope, as it is the only stable isotope existing in nature) captures a neutron, it forms the sodium-24 isotope. In this process, sodium-23 is transformed into sodium-24 through the (n,γ) reaction (i.e., capturing a neutron and releasing a gamma ray). Sodium-24 is an unstable isotope with a half-life of approximately 15 hours and transforms into the stable magnesium-24 isotope through β decay, accompanied by the emission of positrons or electron capture and the release of neutrinos. This leads to an increase in the radioactive dose in the primary loop compartment cooling water, an increase in the annual production of radioactive wastewater, and an increase in the radiation dose received by personnel at the same time. Summary of the Invention

[0012] The purpose of the present invention is to provide a chemical additive process for the primary loop compartment cooling system of a new type of high-temperature gas-cooled reactor, making full use of the characteristics of lithium hydroxide ( 7 LiOH·H2O) to increase the pH of the cooling water in the primary loop compartment cooling system. At the same time, hydrazine hydrate is added to maintain a reducing environment in the system, reduce the corrosion rate of carbon steel, reduce the radioactive dose in the primary loop compartment cooling water, reduce the production of radioactive wastewater, reduce the radiation dose received by personnel, and improve the safety of nuclear power plant operation.

[0013] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0014] A chemical additive process for the primary loop compartment cooling system of a new type of high-temperature gas-cooled reactor, adding lithium hydroxide 7 LiOH·H2O and hydrazine hydrate into the primary loop compartment cooling system through the nuclear island chemical dosing device, and coordinately controlling the concentrations of lithium hydroxide 7 LiOH·H2O and hydrazine hydrate in the primary loop compartment cooling system to meet the requirement of controlling the pH of the cooling water in the primary loop compartment cooling system at 8.0 - 9.0.

[0015] The specific steps include:

[0016] The first step: Prepare the drugs. Calculate the dosing amount in the laboratory, transfer the weighed lithium hydroxide 7 LiOH·H2O to dosing tank A and prepare the required concentration with demineralized water; transfer hydrazine hydrate to dosing tank B and prepare the required concentration with demineralized water;

[0017] Step 2: The chemicals used are lithium hydroxide 7 LiOH·H2O and hydrazine hydrate;

[0018] Step 3: Add lithium hydroxide 7 LiOH·H2O and hydrazine hydrate to the primary loop compartment cooling system through the nuclear island chemical dosing device;

[0019] Step 4: Sample the primary loop compartment cooling system through the sampling system, and analyze lithium hydroxide 7 according to "GBT 6906-2006 Analytical Methods for Boiler Water and Cooling Water - Determination of Hydrazine" and "GBT 23942-2009 General Rules for Inductively Coupled Plasma Atomic Emission Spectrometry of Chemical Reagents".

[0020] The concentration of lithium hydroxide 7 LiOH·H2O in the primary loop compartment cooling system is 1.0 - 5.0 mg / kg.

[0021] The concentration of hydrazine hydrate in the primary loop compartment cooling system is 5 - 200 mg / kg.

[0022] Lithium hydroxide 7 LiOH·H2O shall meet the analytical pure standard with the isotope Li 7 relative to the total Li > 99.9%.

[0023] Hydrazine hydrate shall meet the analytical pure standard.

[0024] Lithium hydroxide 7 The mass percentage of LiOH·H2O is 48% - 58%.

[0025] The mass percentage of hydrazine hydrate is 85%.

[0026] The beneficial effects achieved by the present invention are:

[0027] Effectively improving and balancing the control of the pH value of the primary loop compartment cooling system, improving the corrosion conditions of the equipment and pipelines in the compartment cooling system, reducing the radioactive dose in the primary loop compartment cooling water, reducing the generation amount of radioactive wastewater, reducing the irradiation dose of personnel, and improving the safety of nuclear power plant operation. Specific embodiments

[0028] The present invention will be described in detail below with reference to specific embodiments.

[0029] A chemical additive process for a new type of high-temperature gas-cooled reactor compartment cooling system. Add lithium hydroxide ( 7 LiOH·H2O) and hydrazine hydrate to the primary loop compartment cooling system, and coordinately control the lithium hydroxide in the primary loop compartment cooling system (7 The concentration of LiOH·H2O and hydrazine hydrate is adjusted to meet the requirement that the pH of the cooling water in the primary loop compartment cooling system is controlled within the range of 8.0 - 9.0.

[0030] In the primary loop compartment cooling system described above, lithium hydroxide ( 7 LiOH·H2O) has a concentration of 1.0 - 5.0 mg / kg.

[0031] In the primary loop compartment cooling system described above, hydrazine hydrate has a concentration of 5 - 200 mg / kg.

[0032] The lithium hydroxide ( 7 LiOH·H2O) should meet the analytical pure standard with the isotope Li 7 (relative to total Li) > 99.9%.

[0033] The hydrazine hydrate should meet the analytical pure standard.

[0034] The lithium hydroxide ( 7 LiOH·H2O) has a mass percentage of 48% - 58%.

[0035] The hydrazine hydrate has a mass percentage of 85%.

[0036] When implementing the present invention, the chemicals used are lithium hydroxide ( 7 LiOH·H2O) and hydrazine hydrate. With the aim of achieving the best anti-corrosion effect with the pH of the primary loop compartment cooling system controlled at 8.0 - 9.0, lithium hydroxide ( 7 LiOH·H2O) and hydrazine hydrate are added to the primary loop compartment cooling system through the chemical dosing device in the nuclear island. In the primary loop compartment cooling system described above, lithium hydroxide ( 7 LiOH·H2O) has a concentration of 1.0 - 5.0 mg / kg. In the primary loop compartment cooling system described above, hydrazine hydrate has a concentration of 5 - 200 mg / kg.

[0037] Step 1: Prepare the chemicals. Calculate the dosing amount in the laboratory. Transfer the weighed lithium hydroxide ( 7 LiOH·H2O) to dosing tank A and prepare the required concentration with demineralized water; transfer hydrazine hydrate to dosing tank B and prepare the required concentration with demineralized water.

[0038] Step 2: The chemicals used are lithium hydroxide ( 7 LiOH·H2O) and hydrazine hydrate. The lithium hydroxide ( 7 LiOH·H2O) should meet the analytical pure standard with the isotope Li 7 (relative to total Li) > 99.9%. The hydrazine hydrate should meet the analytical pure standard.

[0039] Step 3: Add lithium hydroxide ( 7 LiOH·H2O) and hydrazine hydrate to the primary loop compartment cooling system through the nuclear island chemical dosing device.

[0040] Step 4: Take samples from the primary loop compartment cooling system through the sampling system, and analyze the concentration of lithium hydroxide ( 7 LiOH·H2O) and the concentration of hydrazine hydrate in accordance with "GBT 6906-2006 Analytical Methods for Boiler Water and Cooling Water - Determination of Hydrazine" and "GBT 23942-2009 General Rules for Chemical Reagents - Inductively Coupled Plasma Atomic Emission Spectrometry".

Claims

1. A chemical additive process for the chamber cooling system of a new type of high-temperature gas-cooled reactor, characterized in that: Adding lithium hydroxide into the primary loop compartment cooling system through the nuclear island chemical dosing device 7 LiOH·H2O and hydrazine hydrate, and coordinately controlling the concentrations of lithium hydroxide 7 LiOH·H2O and hydrazine hydrate in the primary loop compartment cooling system to meet the requirement of controlling the pH of the cooling water in the primary loop compartment cooling system within the range of 8.0 - 9.

0.

2. The chemical additive process of the novel high-temperature gas-cooled reactor compartment cooling system according to claim 1, wherein: The specific steps include: Step 1: Prepare the medicines. Calculate the dosage in the laboratory. Transfer the weighed lithium hydroxide 7 LiOH·H2O to dosing tank A and prepare the required concentration with demineralized water; transfer hydrazine hydrate to dosing tank B and prepare the required concentration with demineralized water; Step 2: The chemicals used are lithium hydroxide 7 LiOH·H2O and hydrazine hydrate; Step 3: Add lithium hydroxide to the primary loop compartment cooling system through the nuclear island chemical addition device 7 LiOH·H2O and hydrazine hydrate; Step 4: Sample the primary loop compartment cooling system through the sampling system, and analyze lithium hydroxide in accordance with "GBT 6906-2006 Analytical Methods for Boiler Water and Cooling Water - Determination of Hydrazine" and "GBT 23942-2009 General Rules for Chemical Reagents - Inductively Coupled Plasma Atomic Emission Spectrometry". 7 Analyze the concentrations of LiOH·H2O and hydrazine hydrate.

3. The chemical additive process for the new high-temperature gas-cooled reactor compartment cooling system according to claim 2, characterized in that: Lithium hydroxide in the primary loop compartment cooling system 7 The concentration of LiOH·H2O is 1.0 - 5.0 mg / kg.

4. The chemical additive process of the novel high-temperature gas-cooled reactor compartment cooling system according to claim 2, wherein: The concentration of hydrazine hydrate in the primary loop compartment cooling system is 5 - 200 mg / kg.

5. The chemical additive process for the new high-temperature gas-cooled reactor compartment cooling system according to claim 2, wherein: Lithium hydroxide 7 LiOH·H2O shall conform to the analytical pure standard of isotope Li 7 with respect to the total Li>99.9% 6. The chemical additive process for the new high-temperature gas-cooled reactor compartment cooling system according to claim 2, characterized in that: The hydrazine hydrate shall meet the analytical pure standard.

7. The chemical additive process for the chamber cooling system of the new high-temperature gas-cooled reactor according to claim 2, characterized in that: Lithium hydroxide 7 The mass percentage of LiOH·H2O is 48% to 58%.

8. The chemical additive process for the novel high-temperature gas-cooled reactor compartment cooling system according to claim 2, wherein: The mass percentage of hydrazine hydrate is 85%.