Method for purifying helium of high-temperature gas cooled reactor

Abstract

The invention belongs to the technical field of nuclear energy application, and particularly relates to a method for purifying helium of a high-temperature gas cooled reactor. Comprising the following steps: step 1, calculating the total flow of helium needing purification column treatment; 2, the number of purification columns needing to be started is calculated; 3, the maximum helium purification amount of the helium purification system is calculated; and 4, processing according to a calculation result. The system and the method have the beneficial effects that the single high-temperature gas cooled reactor is simultaneously purified by a plurality of purification series, the equilibrium concentration of radionuclides or harmful substances of the high-temperature gas cooled reactor can be greatly reduced, the radionuclide emission of a unit and the collective radiation dose of personnel are reduced, and the safe and stable operation of the unit is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear energy application, and in particular relates to a method for purifying helium in a high-temperature gas-cooled reactor. Background Art

[0002] The nuclear island of the high-temperature gas-cooled reactor unit is designed with single-module (double reactors in a single module) and multi-module combined operation modes. The unit capacity is flexible and can be constructed in standard modularization to shorten the construction period. During normal operation, the high-temperature gas-cooled reactor will produce more fission and activation products in the primary circuit. Most of these radioactive substances are deposited on the inner surface of the primary circuit system during the circulation of the primary circuit coolant helium in the primary circuit system, especially on the colder surface of the steam generator, which increases the radiation field intensity of the equipment and pipelines, and will cause the dose rate of the operation and maintenance personnel to increase; because tritium has a strong penetration ability under the high temperature and high pressure conditions of the primary circuit of the high-temperature gas-cooled reactor, it can also penetrate through the steam generator heat transfer tube into the secondary circuit, which may affect the discharge of wastewater from the secondary circuit.

[0003] At present, in order to maintain the purity of coolant helium to meet the requirements and control the level of chemical impurities in helium under normal operating conditions, a helium purification system is set up in high-temperature gas-cooled reactors. It is mainly composed of dust filters, electric heaters, copper oxide beds, pipeline filters, medium-temperature helium / helium heat exchangers, water / helium coolers, normal gas / water separators, molecular sieve beds, low-temperature helium / helium heat exchangers, low-temperature adsorbers and diaphragm compressors, etc., to remove harmful chemical impurities (H2O, O2, CO2, CO, H2, CH4, N2, etc.), tritium and solid particles (mainly graphite dust) in helium. The maximum flow rate of a single-row purification bed is designed to be 150kg / h, and the average impurity removal efficiency is ≥95%. The original design has two normal purification trains for each helium purification module. When the reactor is operating normally, each reactor has a normal purification train to serve it; when a normal purification train stops operating for a short period of time due to regeneration or maintenance, the impurity concentration in the primary circuit helium of the reactor connected to it will increase, and a normal purification train in operation (two normal purification trains are not arranged to be regenerated at the same time) can also be used to serve the two reactors in turn for a short period of time. The single purification series of the above design cannot serve two reactors at the same time, nor can two purification series serve one reactor at the same time. In addition, in the original design, the helium flow rate flowing through the cryogenic adsorption bed when the helium purification system is normally operating is 1 / 4 of the purification flow rate of the helium purification system.

[0004] At present, the activatable elements other than uranium in various material components of high-temperature gas-cooled reactors have been strictly controlled. The existing process technology can no longer significantly reduce the content, nor can it reduce the equilibrium concentration level of radioactive nuclides produced. Taking the tritium concentration of a proposed nuclear power plant as an example, the activity of tritium in the primary coolant is calculated to be 1.4E×10 11Bq, the design value of the secondary circuit leakage rate (total replacement rate) is 2.142t / h~21.42t / h. Through calculation, it is deduced that the equilibrium concentration of tritium in the secondary circuit water caused by the tritium penetration pathway is about 1.46×10 5 Bq / kg~1.46×10 6 Bq / kg, which is still at a relatively high level. In addition, if radionuclides or hazardous substances overflow from the fuel ball to the primary circuit in a reactor at an excessive level, it is also necessary to quickly reduce the concentration of radionuclides or hazardous substances to within the allowable range to ensure safe and stable operation of the unit. Therefore, it is necessary to optimize the operation method of the high-temperature gas-cooled reactor helium purification system, reduce the emission of radionuclides and the collective radiation dose of personnel, and ensure safe and stable operation of the unit. Summary of the invention

[0005] The purpose of the present invention is to provide a method for purifying helium of a high temperature gas-cooled reactor, which can realize multiple purification series to purify a single high temperature gas-cooled reactor at the same time, and can greatly reduce the equilibrium concentration of radioactive nuclides and harmful substances in the high temperature gas-cooled reactor.

[0006] The technical solution of the present invention is as follows: A method for purifying helium in a high temperature gas-cooled reactor comprises the following steps:

[0007] Step 1: Calculate the total helium flow rate to be processed by the purification column;

[0008] Step 2: Calculate the number of purification columns to be started;

[0009] Step 3: Calculate the maximum helium purification capacity of the helium purification system;

[0010] Step 4: Perform processing based on the calculation results.

[0011] The step 1 includes that for a unit with N high temperature gas-cooled reactor modules, if a single reactor failure occurs and causes the equilibrium concentration level of radionuclides in helium to increase, the total helium flow rate Q to be treated by the purification column is:

[0012]

[0013] Where: Q a Helium circulation flow rate of a single reactor, kg / h; C a The equilibrium concentration of radionuclides in helium under a single reactor failure condition, Bq / L; the equilibrium concentration of radionuclides in helium that needs to be achieved for normal operation of the C reactor, Bq / L; the equilibrium concentration of radionuclides in helium at the outlet of the C0 purification train, Bq / L.

[0014] The step 2 includes selecting n helium purification trains to simultaneously purify the helium in the failed reactor. A single purification train is operated at a flow rate L. The number of purification trains to be started is:

[0015]

[0016] The n≤2N.

[0017] The maximum helium purification amount Q of the helium purification system in step 3 m for:

[0018] Q m =2NL (3).

[0019] In step 4, when the total amount of helium to be treated by the purification column calculated by the control system Q>Q m At the time, it was the largest purification reactor in the purification series.

[0020] In step 4, corresponding actions are taken according to the requirements for radionuclides or hazardous substances in the operation technical specifications.

[0021] The beneficial effects of the present invention are: realizing multiple purification series to purify a single high-temperature gas-cooled reactor at the same time, which can greatly reduce the equilibrium concentration of radioactive nuclides or harmful substances in the high-temperature gas-cooled reactor, reduce the emission of radioactive nuclides of the unit and the collective radiation dose of personnel, and ensure the safe and stable operation of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the high-temperature gas-cooled reactor purification system.

[0023] In the figure: 1. High temperature gas-cooled reactor No. 1; 2. High temperature gas-cooled reactor No. 2; 3. Helium purification series 1; 4. Helium purification series 2; 5. Membrane press No. 1; 6. Membrane press No. 2. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Taking the high-temperature gas-cooled reactor module combination as an example, the system for high-temperature gas-cooled reactor helium purification operation described in the present invention includes high-temperature gas-cooled reactor No. 1 stack 1, high-temperature gas-cooled reactor No. 2 stack 2, helium purification 1 series 3, helium purification 2 series 4, membrane press No. 1 5, membrane press No. 2 6, and N helium purification series and membrane presses.

[0026] During the design, any helium purification series is allowed to have the ability to maintain long-term operation in the entire range of greater than 1 / 4 (37.5kg / h) to full flow (150kg / h), and the helium purification series is allowed to purify any high-temperature gas-cooled reactor. Taking the helium purification series 1 purifying high-temperature gas-cooled reactor No. 1 as an example, it normally operates at 1 / 4 flow. When the radioactivity level of the unit increases, the helium purification series 1 flow can be correspondingly increased, and the maximum is a single series full flow operation, until the radioactivity level of the high-temperature gas-cooled reactor No. 1 drops to the normal allowable equilibrium concentration value. If the full flow operation of the helium purification series 1 still cannot reduce the radioactivity level of the high-temperature gas-cooled reactor No. 1 to the normal allowable equilibrium concentration value, stop the helium purification series 2 to purify the high-temperature gas-cooled reactor No. 2, and put the helium purification series 2 and the helium purification series 1 into operation at the same time to purify the high-temperature gas-cooled reactor No. 1, and adjust the flow of the two purification series accordingly, up to the full flow operation of the two series, until the radioactivity level of the high-temperature gas-cooled reactor No. 1 drops to the normal allowable equilibrium concentration value.

[0027] The operation process of this system is as follows:

[0028] A certain series of helium purification is normally operated at 1 / 4 flow rate to purify a certain high temperature gas-cooled reactor. When the purification is balanced, the theoretical allowable concentration value of the reactor is C. Due to the abnormal release of radionuclides or harmful substances, the actual concentration value increases to C a ;

[0029] In order to reduce the concentration to the allowable value C, the total flow value Q of the helium purification series that needs to be put into operation can be calculated by formula 1;

[0030] If the total flow of all purification series that can be put into operation is Q>Q m , put the required number of purification series and the corresponding total flow rate into the purification of a certain number of high temperature gas-cooled reactors until the concentration drops to the normal allowable equilibrium value;

[0031] If the total flow rate of all purification series that can be put into operation is Q<Q m , put all purification systems into operation at maximum flow to purify a certain high-temperature gas-cooled reactor, and take corresponding actions according to the requirements for radionuclides or hazardous substances in the operating technical specifications.

[0032] A method for purifying helium of a high temperature gas-cooled reactor comprises the following steps:

[0033] Step 1: Calculate the total helium flow rate to be handled by the purification column

[0034] For a unit with N high-temperature gas-cooled reactor modules, if a single reactor failure causes the equilibrium concentration level of radionuclides in helium to increase, the total helium flow rate Q that needs to be treated by the purification train is:

[0035]

[0036] Where: Qa : Helium circulation flow rate of a single reactor, kg / h; C a : equilibrium concentration of radionuclides in helium under single reactor failure condition, Bq / L; C: equilibrium concentration of radionuclides in helium required for normal operation of the reactor, Bq / L; C0: equilibrium concentration of radionuclides in helium at the outlet of the purification train, Bq / L.

[0037] Step 2: Calculate the number of purification columns to be started

[0038] In this regard, n (n≤2N) helium purification trains can be selected to simultaneously purify the helium in the failed reactor. If a single purification train runs at a flow rate of L, the number of purification trains that need to be started is:

[0039]

[0040] Step 3: Calculate the maximum helium purification capacity of the helium purification system

[0041] The maximum helium purification capacity of this helium purification system is Q m for:

[0042] Q m =2NL (3)

[0043] Step 4: Perform processing based on the calculation results.

[0044] When the total amount of helium that needs to be treated by the purification column calculated by the control system Q>Q m When doing so, the largest cleanup reactor in the series can be used and appropriate actions can be taken according to the requirements for radionuclides or hazardous substances in the operating technical specifications.

Claims

1. A method for purifying helium in a high temperature gas-cooled reactor, characterized in that: The steps include: Step 1: Calculate the total helium flow rate to be processed by the purification column; Step 2: Calculate the number of purification columns to be started; Step 3: Calculate the maximum helium purification capacity of the helium purification system; Step 4: Perform processing based on the calculation results.

2. A method for purifying helium of a high temperature gas-cooled reactor according to claim 1, characterized in that: The step 1 includes that for a unit with N high temperature gas-cooled reactor modules, if a single reactor failure occurs and causes the equilibrium concentration level of radionuclides in helium to increase, the total helium flow rate Q to be treated by the purification column is: Where: Q a Helium circulation flow rate of a single reactor, kg / h; C a The equilibrium concentration of radionuclides in helium under a single reactor failure condition, Bq / L; the equilibrium concentration of radionuclides in helium that needs to be achieved for normal operation of the C reactor, Bq / L; the equilibrium concentration of radionuclides in helium at the outlet of the C0 purification train, Bq / L.

3. A method for purifying helium of a high temperature gas-cooled reactor according to claim 1, characterized in that: The step 2 includes selecting n helium purification trains to simultaneously purify the helium in the failed reactor. A single purification train is operated at a flow rate L. The number of purification trains to be started is:

4. A method for purifying helium of a high temperature gas-cooled reactor as claimed in claim 3, characterized in that: The n≤2N.

5. The method for purifying helium of a high temperature gas-cooled reactor according to claim 1, characterized in that: The maximum helium purification amount Q of the helium purification system in step 3 m for: Q m =2NL (3)。 6. A method for purifying helium of a high temperature gas-cooled reactor according to claim 1, characterized in that: In step 4, when the total amount of helium to be treated by the purification column calculated by the control system Q>Q m At the time, it was the largest purification reactor in the purification series.

7. A method for purifying helium of a high temperature gas-cooled reactor according to claim 6, characterized in that: In step 4, corresponding actions are taken according to the requirements for radionuclides or hazardous substances in the operation technical specifications.

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