Simplified Critical Safety Analysis Method for the Entire Piping Equipment Room

Abstract

The present invention relates to a simplified pipe equipment room whole criticality safety analysis method, which belongs to the field of nuclear criticality safety analysis, and includes the steps of: screening all the pipelines of the equipment room waiting for analysis based on the medium in the pipeline, screening the pipelines containing the material liquid that is easily split into effective pipelines, and calculating the total volume of the material liquid in the effective pipelines; constructing a simplified pipe model and closely arranging all the pipelines with a minimum arrangement pitch; keeping the total volume of the material liquid of the pipe model unchanged and changing the number and height of the pipe model pipelines to obtain the pipe dimensions with the maximum reactivity of the simplified pipe model; and closely arranging the simplified pipe model with the maximum reactivity next to the equipment with the maximum reactivity in the equipment room to maximize the interaction. The method provided by the present invention is much simpler than the process of constructing the pipes one by one by finely dividing them, improving the efficiency of the calculation analysis, and avoiding the problem of the calculation result exceeding the criticality safety acceptance standard due to the simple collection of the pipe material liquid and taking overly conservative measures.

Description

Technical Field

[0001] This disclosure claims the priority of a Chinese patent application with an application date of November 23, 2021, an application number of CN202111394652.4, and a title of "Simplified Whole Critical Safety Analysis Method for Pipeline Equipment Rooms". The present invention belongs to the technical field of nuclear critical safety analysis, and specifically relates to a simplified whole critical safety analysis method for pipeline equipment rooms.

Background Art

[0002] When processing materials that are prone to splitting in a solution state, it is often the case that a pipeline format is adopted to transport the material liquid of materials that are prone to splitting between various processing facilities. Facilities that process materials that are prone to splitting in a solution state often have a complex process flow, a high concentration of materials that are prone to splitting, a large number of pipelines arranged in the equipment room, and a huge total amount of material liquid. Therefore, the overall critical safety issue of the equipment room including pipelines becomes a problem that cannot be ignored, and the overall critical safety analysis of the equipment room must consider the impact on the critical safety of these pipelines. The pipeline layout in the equipment room is characterized by a complex arrangement, a large number, different pipe diameters, most pipes being thin, many pipelines being between the equipment and the wall, and a small number being between the equipment. In addition, there are pipes that transport materials that are prone to splitting and pipes that transport materials that do not contain materials that are prone to splitting in the pipes. When performing an overall critical safety calculation analysis of the equipment room considering the pipeline layout, usually a refinement analysis or a conservative analysis method is used. The refinement analysis method is to construct a critical calculation model of each pipe one by one based on parameters such as the starting position, diameter, wall thickness, length, pipe wall material, and material liquid components of each pipe. The advantage of this method is that it considers the actual layout of the pipes, and the disadvantage is that a large amount of pipe modeling work needs to be done. In addition, when using the Monte Carlo program for critical calculations, the sampling of source neutrons needs to be reasonably distributed among pipes and equipment containing materials that are prone to splitting, and the randomness of Monte Carlo sampling cannot be guaranteed, and a large amount of calculation time needs to be consumed. In addition, the results of the refinement analysis have no envelopability, and if there are changes in the pipe layout design, it must be recalculated. Another commonly used method is to simply collect the material liquid of materials that are prone to splitting to form a simple geometric body, such as a solution wall. The advantage of this conservative method is that the modeling is simple, and the disadvantage is that such an overly conservative method is difficult to meet the requirements of critical safety in the calculation results when the total amount of pipeline material liquid is large. Therefore, there is a need to find an overall critical safety analysis method for the equipment room that is moderately conservative, simple in modeling, and considers the pipeline layout. According to the search of related patents, currently, there are invention patents for the critical safety analysis method or critical safety control method of some facilities related to spent fuel reprocessing plants, for example, "Critical Safety Control Device for Spent Fuel Dissolver" (Application No.: CN20120325882.4), "Critical Safety Design Method for Fluidized Bed in Nuclear Fuel Reprocessing" (Application No.: CN201910899705.4), "Critical Safety Control Method for Dissolver with Annular Solid Neutron Poison Partition Arrangement" (Application No.: CN201410271524.4), "Modeling Method for Shear Segment of Spent Fuel in Dissolver for Critical Safety Analysis" (Application No.: CN20201099165.0), etc. However, currently, there is almost no method for the overall critical safety analysis of the equipment room in the spent fuel reprocessing plant including pipelines. Content of the Invention

[0003] The object of the present invention is to provide a simplified overall critical safety analysis method for pipeline equipment rooms in order to solve the defects existing in the prior art. This method can comprehensively evaluate the critical safety problems of a large number of pipelines and equipment arranged in the equipment room, improve the efficiency of calculation and analysis, and at the same time avoid the problem that the calculation results exceed the critical safety acceptance criteria due to easily collecting and overly storing the pipeline material liquid. In order to achieve the above object, the technical solution adopted by the present invention is as follows. A method for simplifying the overall critical safety analysis of a pipeline equipment room includes S1: Conduct screening analysis on all pipelines in the equipment room to be analyzed based on the medium in the pipeline, screen the pipelines containing the material liquid that is easy to fission as effective pipelines, calculate the total volume of the material liquid in all effective pipelines, S2: Construct a simplified pipe model, and all pipelines in the simplified pipe model are closely arranged at the minimum layout pitch, S3: Keep the total volume of the material liquid in the pipe model unchanged, change the number and height of the pipe model pipelines, and obtain the pipe dimensions with the maximum reactivity of the simplified pipe model through search calculation, S4: Adhere the simplified pipe model with the maximum reactivity closely to the equipment with the maximum reactivity in the equipment room and arrange it closely so that the interaction is maximized. including the steps. Furthermore, in the above-described simplified pipeline equipment room overall critical safety analysis method, in step S1, the screening analysis of the pipeline is specifically screening and removing pipelines that use the material liquid as gas or do not contain a material liquid that is prone to splitting, so as to screen the effective pipelines. For pipelines that transport multiple media, the gas situation therein is not considered. Furthermore, in the above-described simplified pipeline equipment room overall critical safety analysis method, in step S1, the uranium and plutonium concentrations in the material liquid state with the maximum reactivity are selected for analysis. Furthermore, in the above-described simplified pipeline equipment room overall critical safety analysis method, in step S1, the total volume of the material liquid in the effective pipeline is calculated using the outer diameter dimension of the effective pipeline, covering the situation where the pipe wall is corroded. Furthermore, in the above-described simplified pipeline equipment room overall critical safety analysis method, all the pipeline lengths in the simplified pipe model described in step S2 are the same, and the pipe diameter is the thickest pipe diameter among the effective pipelines. Furthermore, in the above-described simplified pipeline equipment room overall critical safety analysis method, the method of closely arranging all the pipelines in the simplified pipe model described in step S2 at the minimum arrangement pitch is specifically all the pipelines in the simplified pipe model are closely arranged in a triangular array to form a pipe shape with a hexagonal outline, and the pipeline pitch is calculated based on the actual minimum arrangement pitch of the thickest pipeline among the screened effective pipelines. Furthermore, in the above-described simplified pipeline equipment room overall critical safety analysis method, the corrosion allowance set for the pipeline wall thickness in the simplified pipe model is considered. Furthermore, step S3 of the above-described simplified pipeline equipment room overall critical safety analysis method is specifically keeping the total volume of the material liquid in the pipe model unchanged, gradually increasing the number of turns of the hexagonal pipe, and accordingly gradually reducing the final length of the pipe, and finally obtaining the hexagonal simplified pipe model with the maximum reactivity through search calculation. Furthermore, in the simplified pipeline equipment room overall critical safety analysis method described above, in step S4, the step of closely attaching the hexagonal simplified pipe model having the maximum reactivity to the vicinity of the equipment with the maximum reactivity in the equipment room is specifically The hexagonal simplified pipe model is arranged vertically near the equipment with the maximum reactivity in the vertical direction, with one side of the hexagonal prism being in close contact with the equipment. If there are other equipment with high reactivity near the equipment with the maximum reactivity, the hexagonal simplified pipe model is arranged between the two pieces of equipment and in close contact with the equipment with the maximum reactivity. If there is a wall of the equipment room near the equipment with the maximum reactivity, the hexagonal simplified pipe model is arranged between the equipment and the wall and in close contact with the equipment with the maximum reactivity. Furthermore, in the simplified pipeline equipment room overall critical safety analysis method described above, if there is a pipeline in the effective pipeline whose pipe diameter exceeds the set upper limit value and the number is less than the set value, it can be modeled independently based on its actual dimensions and actual position, and the remaining effective pipelines whose pipe diameters do not exceed the set upper limit value are modeled and analyzed according to steps S2 to S4. Using the simplified pipeline equipment room overall critical safety analysis method described in the present invention, the following remarkable technical effects are achieved. (1) It is possible to avoid the cumbersome operation of constructing a large number of pipe models one by one in the refined modeling, simplify the calculation and analysis process, and improve the calculation and analysis efficiency. (2) By simply collecting the pipeline material liquid, it is possible to avoid overly conservatively considering the influence of the pipeline layout on the critical safety design, more reasonably analyze and evaluate the critical safety influence of the pipeline layout, and improve the economy and rationality of the design. The present invention is applicable to the nuclear critical safety design and analysis evaluation of all easily fissile material liquid pipeline facilities.

Brief Description of the Drawings

[0004] Figure 1 is a flowchart of the simplified pipeline equipment room overall critical safety analysis method provided by a specific embodiment of the present invention. Figure 2 is a cross-sectional view of the simplified pipe model. Figure 3 is a cross-sectional view of the equipment room layout where the simplified pipe is in close contact with the equipment having the maximum reactivity. Specific Embodiments

[0005] The present invention will be further described below by combining specific embodiments with the drawings of the specification. In FIG. 1, a flowchart of a simplified pipeline equipment room overall critical safety analysis method provided by a specific embodiment of the present invention is shown, and the method includes the following steps. Step S1: Based on the medium in the pipeline, screening analysis is performed on all pipelines in the equipment room to be analyzed, pipelines containing materials that are prone to fission are screened as effective pipelines, and the total volume of the effective pipeline liquid is calculated. In one preferred embodiment, the specific method for screening and analyzing pipelines is to obtain effective pipelines by screening and removing pipelines in which the material liquid (i.e., the medium in the pipe) is a gas or pipelines that do not contain materials that are prone to fission. For pipelines that may convey multiple media, without considering the gas situation therein, the uranium and plutonium concentrations, which are the most reactive material liquid states from each solution state, are conservatively selected for analysis. When calculating the total volume of the effective pipeline liquid, it is conservatively calculated based on the outer diameter dimension of the effective pipeline, covering the situation where the pipe wall is corroded. Step S2: Construct a simplified pipe model. All pipelines in the simplified pipe model are closely arranged according to a set arrangement method. In one preferred embodiment, the lengths of all pipelines in the simplified pipe model are all the same, and the pipe diameter in the pipe is the thickest pipe diameter among the effective pipelines. All effective pipelines are conservatively arranged according to the most compact arrangement method, that is, the pipelines are distributed according to a triangular array, forming a pipe shape with a hexagonal contour. The cross-sectional view of the simplified pipe model is as shown in FIG. 2, and the pipe pitch is calculated based on the actual minimum arrangement pitch of the thickest pipeline among the screened effective pipelines. The material liquid is considered based on the uranium and plutonium concentrations with the maximum reactivity in the effective pipeline. The wall thickness of the pipe conservatively considers a certain corrosion allowance. Step S3: By keeping the total volume of the material liquid in the pipe model unchanged and changing the number and height of the pipe models, the pipe dimensions with the maximum reactivity of the simplified pipe model are obtained through search calculations. In this embodiment, the pipe model refers to the simplified pipe model obtained in Step S2, and the height refers to the length of the pipe. In one preferred embodiment, the search calculation is specifically as follows. Keep the total volume of the material liquid in the pipe model unchanged, gradually increase the number of turns of the hexagonal pipe (i.e., gradually increase the number of pipelines in the simplified pipe model), gradually decrease the length of the pipe, and finally obtain the hexagonal simplified pipe model with the maximum reactivity through search calculations, that is, obtain the pipe dimensions with the maximum reactivity of the simplified pipe model. The simplified pipe model with the maximum reactivity comprehensively considers the effect of all pipelines gathering together and conservatively considers the pipe diameter, material liquid components, and pipeline pitch. Step S4: By closely attaching the simplified pipe model with the maximum reactivity obtained through search calculations to the side of the equipment with the maximum reactivity in the equipment room, the interaction between the pipelines and the equipment in the equipment room is comprehensively considered. Closely attach the simplified pipe model with the maximum reactivity to the side of the equipment with the maximum reactivity in the equipment room and arrange it in a close contact manner so that the interaction is maximized. Specifically, there are the following several situations. As shown in Figure 3, the hexagonal pipe is arranged vertically beside the cylindrical equipment with the maximum reactivity in the vertical direction and is closely attached to the equipment on one side of the hexagonal prism. If there are other equipment with high reactivity near the equipment with the maximum reactivity, the pipe should be placed between the two pieces of equipment and closely attached to the equipment with the maximum reactivity. If there is a wall of the equipment room near the equipment with the maximum reactivity, the pipe should be placed between the equipment and the wall and closely attached to the equipment with the maximum reactivity. In steps S2 to S4, if there are pipelines in the effective pipelines with a large pipe diameter (for example, the pipe diameter exceeds the set upper limit value) and a small number (for example, the number is less than the set value), modeling is performed individually based on their actual dimensions and actual positions. The remaining effective pipelines with a smaller pipe diameter (for example, the remaining pipe diameters of the effective pipelines do not exceed the set upper limit value) are modeled and analyzed according to steps S2 to S4. For example, step S1 is executed to obtain N effective pipelines in the equipment room waiting for analysis. The pipe diameters of the N effective pipelines are arranged in descending order, and M effective pipelines with the top-ranked pipe diameter sequences are selected from the N effective pipelines. Based on the actual dimensions and actual positions of the pipelines, individual modeling is performed for each of the M effective pipelines to obtain the layout results of the M effective pipelines. For example, M = N * 0.5%. For the remaining effective pipelines, analysis is performed according to steps S2 to step S4 to obtain the layout results of the remaining effective pipelines. When the pipe diameters of a small number of pipelines in the effective pipelines are much larger than those of other pipelines, if the analysis and calculation are performed using the maximum pipe diameter, the conservativeness of the analysis results of the simplified pipe model is high. Therefore, by selecting a small number of pipelines with large pipe diameters and performing individual modeling, the conservativeness of the pipeline layout analysis can be reasonably reduced. To more clearly illustrate the technical solution of the present invention, here, an equipment room is taken as an example for explanation. In a certain equipment room for pipelines containing a material liquid that is prone to splitting, more than 800 pipelines are arranged. After sorting these pipelines and not considering the pipelines that do not contain materials prone to splitting such as gas, acid solution, pure water, and organic solvent, there are a total of 450 effective pipelines. The total volume of the material liquid in the effective pipelines is 385.7 L. The uranium and plutonium concentrations of the material liquid with the highest reactivity in the material liquid of these pipelines are selected. Among these pipelines, the maximum dimension of the diameter is an outer radius of 2.415 cm and an inner radius of 2.047 cm, and the actual pipeline layout pitch is at least 13 cm. Based on the above parameters, a hexagonal simplified pipe model is constructed. The pipeline lengths in the simplified pipe model are all the same. The pipe diameter in the pipe is the thickest diameter in the effective pipeline (i.e., outer radius 2.415 cm, inner radius 2.047 cm). Considering the corrosion of the pipe wall of 0.2 cm, the pitch is considered based on the actual minimum layout pitch of 13 cm of the thickest pipeline, and the pipelines are distributed in a triangular array. Keep the total volume of the material liquid in the pipe model unchanged, gradually increase the number of turns of the hexagonal pipe, and gradually decrease the length of the pipe. Distribute the volume of the material liquid to these limited pipelines one turn (1 piece), two turns (7 pieces), three turns (19 pieces), four turns (37 pieces), etc. According to the critical calculation results retrieved, when the number of pipe turns is 8 turns (169 pieces), the effective Proliferation factor keff is the largest. When the concentration of the material liquid is 3.5 times, keff is 0.4723 ± 0.0005, and the cross-sectional view of the pipe model is as shown in Figure 2. In the equipment room, the keff of a certain annular groove equipment is the largest, and the keff of another annular groove equipment is relatively large near the equipment. The simplified pipe with the maximum reactivity obtained from the search calculation is closely attached to the equipment with the largest keff and is close to the nearby equipment. The cross-sectional view (partial) of the equipment room is as shown in Figure 3. When the concentration of the material liquid is 3.5 times, the overall critical safety calculation result keff of the equipment room considering the pipeline layout is 0.7550 ± 0.0005, which is slightly larger than the critical calculation result 0.7407 ± 0.0005 of the equipment room without considering the pipeline, but still can meet the critical safety requirements. 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 filled with materials prone to fission in the equipment room are intensively arranged and adjacent to the equipment with the maximum reactivity, and can envelope the actual layout situation. Also, considering the pipe diameter, pitch, etc. of the actual pipeline layout, it avoids the situation that the critical calculation result exceeds the limit value due to overly conservative analysis. The process of calculation and analysis is greatly simplified compared to the process of constructing each pipe one by one in detail, improving the efficiency of calculation and analysis. Also, the problem that the calculation result exceeds the critical safety acceptance standard due to simply collecting the pipe material liquid and taking overly conservative measures is avoided. The above embodiments are merely illustrative descriptions of the present invention, and the present invention can also be implemented in other specific manners or other specific forms without departing from the gist or essential features of the present invention. Therefore, the described embodiments should be regarded as illustrative in any aspect and not restrictive. The scope of the present invention is defined by the appended claims, and any equivalent changes within the meaning and scope of any claim should be included in the scope of the present invention.

Claims

1. S1: Perform a screening analysis on all pipelines in the equipment room waiting for analysis based on the medium in the pipeline, screen the pipelines containing the material liquid that is prone to splitting as effective pipelines, calculate the total volume of the material liquid in all effective pipelines, S2: Construct a simplified pipe model, and all pipelines in the simplified pipe model are closely arranged at the minimum layout pitch, S3: Keep the total volume of the material liquid in the pipe model unchanged, and obtain the pipe size with the maximum reactivity of the simplified pipe model through search calculation by changing the number and height of the pipe model pipelines, S4: Adhere the simplified pipe model with the maximum reactivity closely to the equipment with the maximum reactivity in the equipment room and arrange it closely so that the interaction is maximized A simplified pipeline equipment room overall critical safety analysis method including the steps.

2. In step S1, the screening analysis of the pipeline is specifically Screen and remove the pipelines with the material liquid as gas or those not containing the material liquid that is prone to splitting to screen the effective pipelines. For the pipelines transporting multiple media, it means not considering the gas situation therein The simplified pipeline equipment room overall critical safety analysis method according to claim 1, characterized in that.

3. Analyze the uranium and plutonium concentrations in the material liquid supply state with the maximum reactivity selected in step S1 The simplified pipeline equipment room overall critical safety analysis method according to claim 2, characterized in that.

4. In step S1, calculate the total volume of the material liquid in the effective pipeline using the outer diameter dimension of the effective pipeline, and envelope the situation where the pipe wall is corroded The simplified pipeline equipment room overall critical safety analysis method according to claim 3, characterized in that.

5. In step S2, all pipeline lengths in the simplified pipe model are the same, and the pipe diameter of the pipeline is the thickest pipe diameter in the effective pipeline The simplified pipeline equipment room overall critical safety analysis method according to any one of claims 1 to 4, characterized in that...

6. In step S2, arranging all pipelines in the simplified pipe model tightly at the minimum layout pitch specifically means that... All pipelines in the simplified pipe model are tightly arranged in a triangular array to form a pipe shape with a hexagonal outline, and the pipeline pitch is calculated based on the actual minimum layout pitch of the thickest pipeline in the screened effective pipelines. The simplified pipeline equipment room overall critical safety analysis method according to claim 5, characterized in that...

7. The pipeline wall thickness in the simplified pipe model takes into account the set corrosion allowance. The simplified pipeline equipment room overall critical safety analysis method according to claim 6, characterized in that...

8. Step S3 specifically means that... Keep the total volume of the material liquid in the pipe model unchanged, gradually increase the number of rounds of the hexagonal pipes, and accordingly gradually reduce the length of the pipes finally, and finally obtain the hexagonal simplified pipe model with the maximum reactivity through search calculation. The simplified pipeline equipment room overall critical safety analysis method according to claim 7, characterized in that...

9. In step S4, closely attaching the hexagonal simplified pipe model with the maximum reactivity to the vicinity of the equipment with the maximum reactivity in the equipment room specifically means that... Arrange the hexagonal simplified pipe model vertically near the equipment with the maximum reactivity arranged vertically, and make one side of the hexagonal column close to the equipment. If there are other equipment with high reactivity near the equipment with the maximum reactivity, arrange the hexagonal simplified pipe model between the two equipment and make it close to the equipment with the maximum reactivity. If there is a wall of the equipment room near the equipment with the maximum reactivity, arrange the hexagonal simplified pipe model between the equipment and the wall and make it close to the equipment with the maximum reactivity. The simplified pipeline equipment room overall critical safety analysis method according to claim 8, characterized by the above.

10. When there are pipelines in the effective pipelines whose pipe diameters exceed the set upper limit value and the number is less than the set value, they can be modeled individually based on their actual dimensions and actual positions, and the remaining effective pipelines whose pipe diameters do not exceed the set upper limit value will carry out modeling and analysis according to steps S2 to S4. The simplified pipeline equipment room overall critical safety analysis method according to claim 6, characterized by the above.

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