A Simplified Method for Overall Critical Safety Analysis of Pipeline Equipment Rooms

Abstract

The present invention relates to a method for simplifying the overall critical safety analysis of a pipeline equipment room, belonging to the technical field of nuclear critical safety analysis, and includes the following steps: screening all pipelines in the equipment room to be analyzed according to the medium in the pipeline, screening out the pipelines containing fissile material solution as effective pipelines, and calculating the total volume of the liquid material in the effective pipelines; establishing a simplified tube bundle model, with all pipelines arranged closely according to the minimum layout spacing; keeping the total volume of the liquid material in the tube bundle model unchanged, changing the number and height of the tube bundle models to obtain the tube bundle size with the maximum reactivity of the simplified tube bundle model; placing the simplified tube bundle model with the maximum reactivity closely beside the equipment with the maximum reactivity in the equipment room and arranging them closely in the way with the maximum interaction. The method provided by the present invention is much simpler than the process of establishing pipelines one by one in detail, improves the calculation and analysis efficiency, and avoids the problem that the calculation result exceeds the critical safety acceptance criterion due to the simple aggregation of the pipeline liquid material being overly conservative.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear critical safety analysis, and specifically relates to a simplified method for overall critical safety analysis of a pipeline equipment room. Background Art

[0002] When dealing with fissile materials in solution state, pipelines are often used to transfer the liquid of fissile materials between various processing equipment. Since the facilities for processing fissile materials in solution state usually have complex technological processes, high concentrations of fissile materials, a large number of pipelines arranged in the equipment room, a huge total amount of liquid, the overall critical safety problem of the equipment room containing pipelines has become a key issue that cannot be ignored. The overall critical safety analysis of the equipment room must consider the impact of these pipelines on critical safety. The pipeline layout in the equipment room has the following characteristics: complex layout and large quantity; different pipe diameters, with most pipes being relatively thin; most pipes are located between equipment and walls, and a small number are located between equipment rooms; there are both pipelines for transporting fissile materials and pipelines for transporting non-fissile materials. When performing the overall critical safety calculation and analysis of the equipment room considering the pipeline layout, refined analysis or conservative analysis methods are usually adopted. The refined analysis method is to establish a critical calculation model for each pipeline one by one according to parameters such as the starting position, diameter, wall thickness, length, pipe wall material, and liquid composition of each pipeline. The advantage of this method is that it considers the actual pipeline layout, but the disadvantages are that a large amount of pipeline modeling work is required, and when using the Monte Carlo program for critical calculation, the sampling of source neutrons needs to be reasonably distributed to each pipeline or equipment containing fissile materials. The randomness of Monte Carlo sampling cannot be guaranteed, and it also consumes a large amount of calculation time. In addition, the results of refined analysis do not have an enveloping property, and when the pipeline layout design changes, it is necessary to recalculate. Another commonly used method is to simply gather the liquid of fissile materials together to form a simple geometric body, such as a solution wall. The advantage of this conservative method is simple modeling, but the disadvantage is that it is difficult to meet the requirements of critical safety in calculation results when the total amount of pipeline liquid is large. Therefore, it is necessary to seek an overall critical safety analysis method for the equipment room considering the pipeline layout that is moderately conservative and has relatively simple modeling.

[0003] According to the retrieval of relevant patents, there are currently some invention patents on the critical safety analysis method or critical safety control method of equipment related to spent fuel reprocessing plants, such as "A critical safety control device for a spent fuel dissolver" (Application No.: CN201420325882.4), "A critical safety design method for fluidized beds in nuclear fuel reprocessing" (Application No.: CN201910899705.4), "A critical safety control method for a dissolver with annular solid neutron poison partition layout" (Application No.: CN201410271524.4), "A modeling method for the spent fuel shearing section of a dissolver for critical safety analysis" (Application No.: CN202010994165.0), etc. However, there is currently no method for the overall critical safety analysis of the equipment room of a spent fuel reprocessing plant including pipelines in China. Summary of the Invention

[0004] To solve the defects existing in the prior art, the purpose of the present invention is to provide a simplified method for the overall critical safety analysis of a pipeline equipment room, which can comprehensively evaluate the critical safety issues of a large number of pipelines and equipment arranged in the equipment room, improve the efficiency of calculation and analysis, and avoid the problem that the calculation results exceed the critical safety acceptance criteria caused by simply aggregating the pipeline liquid too conservatively.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A simplified method for the overall critical safety analysis of a pipeline equipment room, comprising the following steps:

[0007] S1. According to the medium in the pipeline, screen and analyze all the pipelines in the equipment room to be analyzed, select the pipelines containing fissile material solution as effective pipelines, and calculate the total volume of the liquid in all the effective pipelines;

[0008] S2. Establish a simplified tube bundle model, in which all the pipelines in the simplified tube bundle model are closely arranged according to the minimum layout spacing;

[0009] S3. Keep the total volume of the liquid in the tube bundle model unchanged, and search and calculate the tube bundle size with the maximum reactivity of the simplified tube bundle model by changing the number and height of the pipelines in the tube bundle model;

[0010] S4. Place the simplified tube bundle model with the maximum reactivity closely beside the equipment with the maximum reactivity in the equipment room and arrange it closely in the way of maximum interaction.

[0011] Further, in the simplified method for the overall critical safety analysis of a pipeline equipment room as described above, the specific screening and analysis of the pipelines in step S1 is:

[0012] Sift out the pipelines with the feed liquid being gas or a solution without fissile materials to obtain effective pipelines; for pipelines transporting multiple media, the gas situation is not considered.

[0013] Furthermore, for the simplified overall critical safety analysis method of the pipeline equipment room as described above, in step S1, the uranium and plutonium concentrations in the state of the feed liquid with the maximum reactivity are selected for analysis.

[0014] Furthermore, for the simplified overall critical safety analysis method of the pipeline equipment room as described above, in step S1, the total volume of the feed liquid in the effective pipeline is calculated using the outer diameter size of the effective pipeline, including the case where the envelope pipe wall is corroded.

[0015] Furthermore, for the simplified overall critical safety analysis method of the pipeline equipment room as described above, in step S2, all the pipeline lengths in the simplified tube bundle model are the same, and the pipeline diameter is the thickest diameter among the effective pipelines.

[0016] Furthermore, for the simplified overall critical safety analysis method of the pipeline equipment room as described above, in step S2, all the pipelines in the simplified tube bundle model are closely arranged according to the minimum layout spacing, specifically:

[0017] All the effective pipelines in the simplified tube bundle model are closely arranged in a triangular array to form a tube bundle shape with a hexagonal outline, and the pipeline spacing is calculated according to the actual minimum layout spacing of the thickest pipeline among the screened effective pipelines.

[0018] Furthermore, for the simplified overall critical safety analysis method of the pipeline equipment room as described above, the pipeline wall thickness in the simplified tube bundle model considers the set corrosion allowance.

[0019] Furthermore, for the simplified overall critical safety analysis method of the pipeline equipment room as described above, step S3 is specifically:

[0020] Keep the total volume of the feed liquid in the tube bundle model unchanged, gradually increase the number of turns of the hexagonal tube bundle, and correspondingly gradually decrease the length of the tube bundle. Finally, the hexagonal simplified tube bundle model with the maximum reactivity is obtained through search calculation.

[0021] Furthermore, for the simplified overall critical safety analysis method of the pipeline equipment room as described above, in step S4, the hexagonal simplified tube bundle model with the maximum reactivity is placed next to the equipment with the maximum reactivity in the equipment room, specifically:

[0022] Arrange the simplified hexagonal tube bundle model vertically beside the equipment with the maximum reactivity arranged vertically, and press one side of the hexagonal prism against the said equipment; if there are other equipment with relatively large reactivity near the equipment with the maximum reactivity, place the simplified hexagonal tube bundle model between the two pieces of equipment and press it against the equipment with the maximum reactivity; if there is an equipment room wall near the equipment with the maximum reactivity, place the simplified hexagonal tube bundle model between the equipment and the wall and press it against the equipment with the maximum reactivity.

[0023] Furthermore, for the overall critical safety analysis method of the simplified pipeline equipment room as described above, if there are pipelines in the effective pipelines with diameters exceeding the set upper limit value and the number is less than the set value, they can be individually modeled according to their actual sizes and actual positions, and the remaining effective pipelines with diameters not exceeding the set upper limit value are modeled and analyzed according to steps S2 - S4.

[0024] Adopting the overall critical safety analysis method of the simplified pipeline equipment room of the present invention has the following remarkable technical effects:

[0025] (1) It can avoid the cumbersome work of individually establishing a large number of pipeline models in the refined modeling, simplify the calculation and analysis process, and improve the calculation and analysis efficiency;

[0026] (2) It can avoid simply aggregating the pipeline liquid materials, resulting in over - conservatively considering the influence of pipeline layout on critical safety design, more reasonably analyze and evaluate the critical safety impact of pipeline layout, and improve the economy and rationality of the design.

[0027] The present invention can be applied to the nuclear critical safety design, analysis and evaluation of all facilities containing pipelines with fissile material solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a flowchart of the overall critical safety analysis method of the simplified pipeline equipment room provided in the specific embodiment of the present invention;

[0029] Figure 2 is a cross - sectional view of the simplified tube bundle model;

[0030] Figure 3 is a cross - sectional view of the equipment room layout with the simplified tube bundle pressed against the equipment with the maximum reactivity. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention will be further described below in conjunction with specific embodiments and the accompanying drawings of the specification.

[0032] Figure 1 The flowchart showing the overall critical safety analysis method of the simplified pipeline equipment room provided in the specific embodiment of the present invention includes the following steps:

[0033] Step S1: According to the medium in the pipeline, all pipelines in the equipment room to be analyzed are screened and analyzed. Pipelines containing fissile material solutions are selected as effective pipelines, and the total volume of the liquid in the effective pipelines is calculated.

[0034] In a preferred embodiment, the specific method for screening and analyzing the pipelines is as follows: Pipelines with gaseous liquid or pipelines without fissile material solutions are screened out to obtain effective pipelines. For pipelines that may transport multiple media, the gaseous state is not considered, and the uranium and plutonium concentrations in the liquid state with the highest reactivity are conservatively selected for analysis in various solution states.

[0035] When calculating the total volume of the liquid in the effective pipelines, it is conservatively calculated according to the outer diameter of the effective pipelines, including the case where the pipe wall is corroded.

[0036] Step S2: A simplified tube bundle model is established, and all the pipelines in the simplified tube bundle model are closely arranged together according to a set layout.

[0037] In a preferred embodiment, all the pipelines in the simplified tube bundle model have the same length, and the pipe diameter in the tube bundle is the thickest pipe diameter among the effective pipelines; all the effective pipelines are conservatively arranged in the tightest layout, that is, the pipelines are distributed in a triangular array, forming a tube bundle shape with a hexagonal outline. The cross-sectional view of the simplified tube bundle model is as Figure 2 shown. The pipe spacing is calculated according to the actual minimum layout spacing of the thickest pipeline among the selected effective pipelines; the liquid is considered according to the uranium and plutonium concentrations with the highest reactivity in the effective pipelines; the wall thickness of the pipeline is conservatively considered with a certain corrosion allowance.

[0038] Step S3: Keeping the total volume of the liquid in the tube bundle model unchanged, by changing the number and height of the tube bundle models, the tube bundle size with the highest reactivity of the simplified tube bundle model is searched and calculated.

[0039] In a preferred embodiment, the process of searching and calculating is as follows: Keeping the total volume of the liquid in the tube bundle model unchanged, the number of circles of the hexagonal tube bundle (i.e., the number of pipelines is gradually increased) is gradually increased, and the length of the tube bundle is gradually decreased. Through searching and calculating, the hexagonal simplified tube bundle model with the highest reactivity is finally obtained. The simplified tube bundle model with the highest reactivity envelopingly considers the effect of all pipelines gathering together, and conservative considerations are made for the pipe diameter, liquid composition, and pipe spacing.

[0040] Step S4: The simplified tube bundle model with the highest reactivity obtained by searching and calculating is placed closely beside the equipment with the highest reactivity in the equipment room to envelopingly consider the interaction between the pipelines and the equipment in the equipment room.

[0041] Place the simplified tube bundle model with the maximum reactivity close to the equipment with the maximum reactivity in the equipment room, and arrange it closely in the way with the maximum interaction. Specifically, there are the following situations: For example Figure 3 As shown, the hexagonal tube bundle is arranged vertically beside the vertically arranged cylindrical equipment with the maximum reactivity, and one side of the hexagonal prism is closely attached to the equipment; if there are other equipment with relatively large reactivity near the equipment with the maximum reactivity, the tube bundle should be placed between the two equipment and closely attached to the equipment with the maximum reactivity; if there is an equipment room wall near the equipment with the maximum reactivity, the tube bundle should be placed between the equipment and the wall and closely attached to the equipment with the maximum reactivity.

[0042] In steps S2 to S4, if there are pipes with larger diameters and smaller quantities in the effective pipes, they can be modeled separately according to their actual sizes and actual positions, and the remaining effective pipes with smaller diameters are modeled and analyzed according to steps S2 - S4.

[0043] To describe the technical solution of the present invention more clearly, here an equipment room is taken as an example for description.

[0044] There are more than 800 pipes arranged in an equipment room with pipes containing fissile material solution. After sorting out these pipes and not considering the pipes without fissile material such as gas, acid solution, pure water, organic solvent, etc., there are 450 effective pipes. The total volume of the liquid in the effective pipes is 385.7L. Select the uranium and plutonium concentrations of the liquid with the maximum reactivity in these pipe liquids. The largest diameter of these pipes is an outer radius of 2.415 cm and an inner radius of 2.047 cm, and the minimum actual pipe layout spacing is 13 cm.

[0045] Establish a hexagonal simplified tube bundle model according to the above parameters. The pipe lengths in the simplified tube bundle model are all the same. The pipe diameters in the tube bundle are the thickest diameters in the effective pipes (i.e., an outer radius of 2.415 cm and an inner radius of 2.047 cm). The pipe wall considers a corrosion of 0.2 cm, and the spacing is considered according to the actual minimum layout spacing of 13 cm of the thickest pipes. The pipes are distributed in a triangular array. Keeping the total volume of the liquid in the tube bundle model unchanged, gradually increase the number of turns of the hexagonal tube bundle. The length of the tube bundle gradually decreases, 1 turn (1 pipe), 2 turns (7 pipes), 3 turns (19 pipes), 4 turns (37 pipes), etc. Distribute the liquid volume into these limited pipes. According to the critical calculation results of the search, when the number of turns of the tube bundle is 8 turns (169 pipes), the effective multiplication factor k eff of the tube bundle itself is the largest. The k eff under the condition of 3.5 times the liquid concentration is 0.4723 ± 0.0005. The cross-sectional view of the tube bundle model is as Figure 2 shown.

[0046] In this equipment room, the k effis the largest, and there is another annular groove device near the device k eff is relatively large. The simplified tube bundle with the maximum reactivity obtained by search calculation is closely attached to k eff the largest device and leans towards the nearby device. The cross-sectional view (partial) of the equipment room is as shown in Figure 3 Figure. The overall critical safety calculation result k of the equipment room considering the pipeline layout under the condition of 3.5 times the feed liquid concentration eff is 0.7550 ± 0.0005, which is slightly larger than the critical calculation result of the equipment room 0.7407 ± 0.0005 without considering the pipeline, but still can meet the critical safety requirements.

[0047] The overall critical safety analysis method of the simplified pipeline equipment room provided by the present invention conservatively considers the model in which the pipelines containing fissile materials in the equipment room are centrally arranged and are adjacent to the device with the maximum reactivity, can envelope the actual layout situation, and also considers the pipe diameter, spacing, etc. of the actual pipeline layout, avoiding over-conservative analysis so as to obtain the situation where the critical calculation result exceeds the limit value. The process of calculation and analysis is much simpler than the process of establishing pipelines one by one in detail, improving the efficiency of calculation and analysis, and avoiding the problem that the calculation result exceeds the critical safety acceptance criterion due to the simple aggregation of pipeline feed liquid and over-conservatism.

[0048] The above embodiments are only illustrative examples of the present invention. The present invention can also be implemented in other specific ways or other specific forms without departing from the gist or essential characteristics of the present invention. Therefore, the described embodiments should be regarded as illustrative rather than restrictive in any aspect. The scope of the present invention should be defined by the appended claims, and any equivalent changes to the intention and scope of the claims should also be included within the scope of the present invention.

Claims

1. A method for simplifying the overall critical safety analysis of a pipeline equipment room, comprising the following steps: S1. According to the medium in the pipeline, screen and analyze all the pipelines in the equipment room to be analyzed, select the pipelines containing fissile material solution as effective pipelines, and calculate the total volume of the liquid in all the effective pipelines; S2. Establish a simplified tube bundle model. In the simplified tube bundle model, all the pipelines are closely arranged according to the minimum layout spacing, all the pipeline lengths are the same, and the pipeline diameter is the thickest diameter among the effective pipelines; The specific arrangement of all the pipelines in the simplified tube bundle model according to the minimum layout spacing is as follows: all the pipelines in the simplified tube bundle model are closely arranged in a triangular array to form a tube bundle shape with a hexagonal outline, and the pipeline spacing is calculated according to the actual minimum layout spacing of the thickest pipeline among the selected effective pipelines; S3. Keep the total volume of the liquid in the tube bundle model unchanged, and search and calculate the tube bundle size with the maximum reactivity of the simplified tube bundle model by changing the number and height of the pipelines in the tube bundle model; S4. Place the simplified tube bundle model with the maximum reactivity closely beside the equipment with the maximum reactivity in the equipment room and arrange it closely in the way with the maximum interaction.

2. The method for simplifying the overall critical safety analysis of a pipeline equipment room according to claim 1, characterized in that, the specific screening and analysis of the pipelines in step S1 is as follows: Screen out the pipelines with liquid as gas or without fissile material solution to obtain effective pipelines; for the pipelines transporting multiple media, the gas situation is not considered.

3. The method for simplifying the overall critical safety analysis of a pipeline equipment room according to claim 2, characterized in that, In step S1, the uranium and plutonium concentrations in the liquid state with the maximum reactivity are selected for analysis.

4. The method for simplifying the overall critical safety analysis of a pipeline equipment room according to claim 3, characterized in that, In step S1, the outer diameter size of the effective pipeline is used to calculate the total volume of the liquid in the effective pipeline, including the case where the envelope pipe wall is corroded.

5. The method for simplifying the overall critical safety analysis of a pipeline equipment room according to claim 1, characterized in that, The pipeline wall thickness in the simplified tube bundle model considers the set corrosion allowance.

6. The method for simplifying the overall critical safety analysis of a pipeline equipment room according to claim 5, characterized in that, Step S3 is specifically as follows: Keep the total volume of the liquid in the tube bundle model unchanged, gradually increase the number of circles of the hexagonal tube bundle, and correspondingly gradually reduce the length of the tube bundle, and finally obtain the hexagonal simplified tube bundle model with the maximum reactivity through search and calculation.

7. The method for simplifying the overall critical safety analysis of a pipeline equipment room according to claim 6, characterized in that, In step S4, placing the hexagonal simplified tube bundle model with the maximum reactivity closely beside the equipment with the maximum reactivity in the equipment room is specifically as follows: Arrange the simplified hexagonal tube bundle model vertically beside the equipment arranged vertically with the maximum reactivity, and closely attach one side of the hexagonal prism to the said equipment; if there are other equipment with relatively large reactivity near the equipment with the maximum reactivity, place the simplified hexagonal tube bundle model between the two equipment and closely attach it to the equipment with the maximum reactivity; if there is an equipment room wall near the equipment with the maximum reactivity, place the simplified hexagonal tube bundle model between the equipment and the wall and closely attach it to the equipment with the maximum reactivity.

8. The overall critical safety analysis method for the simplified pipeline equipment room according to any one of claims 5-7, characterized in that if there are pipelines in the effective pipelines with a diameter exceeding the set upper limit value and the number is less than the set value, they can be individually modeled according to their actual dimensions and actual positions, and the remaining effective pipelines with a diameter not exceeding the set upper limit value shall carry out modeling and analysis according to steps S2-S4.

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