People's Republic of China Nuclear Industry Standard
EJ794-93
1 Subject content and scope of application
This standard specifies the safety design principles and requirements for the tailings pond of the uranium hydrometallurgical plant.
This standard applies to the safety design of new construction, expansion (reconstruction) and decommissioning of tailings ponds in uranium hydrometallurgical plants. The safety design of the tailings pond containing uranium ( é’ ) element symbiotic ore should also be implemented.
2 Reference standard
GB 11216 General requirements for quality assurance programs for nuclear facility effluents and environmental radioactivity monitoring
GB 14586 Uygur Mining and Metallurgy Facilities Decommissioning Environmental Management Technical Regulations
EJ 348 uranium mining and metallurgy radiation protection design regulations
EJ 432 uranium mining and metallurgy radiation environmental monitoring regulations
SDJ 10 seismic design specification for hydraulic structures
SDJ 218 design code for roller compacted earth-rock dam
3 terms
3.1 uranium tailings pond safety
Refers to the safety of engineering safety, radiation protection safety and environmental protection of all structures in the warehouse.
3.2 tailings pond
The special facilities for sedimentation and storage of ore and slime in the tailings slurry of the water and metallurgical plant are surrounded by dykes. The reservoir is provided with drainage (Hong) structures to eliminate the tailings clarified water and rainwater in the reservoir.
3.3 tailings library crash
It refers to the collapse of the tailings dam due to flood or other reasons, and the tailings slurry rushing out of the dam, causing serious accidents of serious loss of vital materials and serious environmental pollution.
3.4 normal working conditions of tailings pond
It refers to the state that the water level in the tailings reservoir is in the normal working water level and forms a stable seepage.
3.5 tailings mine very working conditions
During the design of stormwater flooding, the tailings pond is saturated with the water level due to rising water level and rainwater infiltration or full saturation of the dam due to long-term rainfall; or earthquakes under normal working conditions.
3.6 auxiliary radiation protection monitoring distance
Refers to the distance between radiation protection and the scope of radiation monitoring between nuclear facilities, between nuclear facilities and residential areas, or between nuclear facilities and non-nuclear facilities.
4 General regulations
4.1 The design of the tailings pond must ensure safety and stability.
4.2 The grade of the tailings pond should be determined according to the effective storage capacity of the tailings pond and the downstream damage caused by the tailings reservoir.
Under normal circumstances, when the storage capacity is greater than 1×10 7 m 3 , it should be designed according to the Class II hydraulic structure; when it is less than 1×10 7 m 3 , it should be designed according to the Grade III hydraulic structure.
When might endanger the downstream tailings important town after the accident, when industrial and mining areas, railway trunk or other facilities of great political and economic significance should be based on probable maximum flood as much use of flood standard.
When the tailings pond has a small impact on the downstream after the accident, the level can be lowered, but it should be approved by the competent authority.
The flood standard for tailings ponds is shown in Table 1. The safety of the top of the dam is shown in Table 2.
Table 1 Flooding standards for tailings ponds
Tailings library level | Flood return period | |
Design flood return period | Check flood return period | |
II | 500 | 2000 |
III | 100 | 1000 |
Table 2 Earth-rock dam south top safety super high
Tailings library level | Flood return period | |
Design flood return period | Check flood return period | |
II | 1.0 | 0.5 |
III | 0.7 | 0.4 |
4.3 The tailings dam divides the design conditions into normal working conditions and extraordinary working conditions according to the working conditions and the nature of the applied forces (such as duration, probability of occurrence, etc.).
Very working conditions such as encountering an earthquake should be considered a very special case.
4.4 Radiation safety design of the tailings pond must comply with the principle of “Improvement of ionizing radiation practice, radiation protection optimization and personal dose limitationâ€, so that the individual dose and the collective dose can be reduced to a level that can be reasonably achieved.
4.5 When the long-term continuous exposure to tailings radiation, in order to limit the random effect, the annual effective dose equivalent limit of the radiation workers is 50mSv; in order to prevent non-random effects, the annual dose equivalent limit of the eye crystal is 150mSv, other single organs Or the organization's annual dose equivalent limit is 500mSv.
The lifetime average annual effective dose equivalent of the resident shall be lower than the dose limit assigned by the operating unit.
4.6 Hygienic standards for non-radioactive toxic and hazardous substances shall be subject to relevant national standards or regulations.
5 tailings pond
5.1 The location of the tailings pond should be avoided as far as possible from industrial enterprises and residential areas. The distance between the uranium tailings pond and industrial enterprises and residential areas should meet the requirements of 7.2.3 of EJ348-88, see Table 3. According to the storage capacity, radioactivity, local natural conditions and population distribution of the tailings pond, the distance can be appropriately increased or decreased.
Table 3 Distance between tailings pond and industrial enterprises and residential areas (m)
Types of | Drinking water source | Residential area | Metallurgical plant | Air intake |
Tailings pond | 1000 | 1000 | 500 | 500 |
The tailings pond should be reasonably placed on the upwind side of industrial enterprises and residential areas and downstream of nearby natural reservoirs and concentrated water intake points according to the local minimum frequency.
5.2 tailings pond should give priority to the small catchment area, small rain and flood flow, small amount of dam construction, and the effective storage capacity is the location of the reservoir.
5.3 The tailings pond should try to avoid the high seismic zone and choose the area where the mountain is stable, no landslide, no mudslide, good geological conditions, and small leakage of the bed to prevent the tailing water from polluting the groundwater and nearby rivers.
When there is sufficient evidence to indicate that the tailings water has contaminated the groundwater through the formation leakage, the anti-seepage layer of the bed should be designed, and the groundwater level and water quality monitoring holes should be properly considered.
5.4 The tailings pond should be equipped with the necessary blocking facilities and ionizing radiation signs.
6 tailings dam
6.1 The tailings dam shall consist of the initial dam and tailings accumulation dam, and its grade shall be consistent with the grade of the tailings pond.
6.2 The selected dam site of the tailings dam should have a small amount of construction (buried) dam, good engineering geological conditions and hydrogeological conditions, and the storage capacity is large, and the surface (under) water can be prevented and reduced to the maximum extent. The principle is based on factors such as the source of dam materials and construction conditions.
6.2.1 When the dam base layer has a large water permeability, causing the groundwater to be contaminated by leakage, affecting the stability or penetration stability of the dam body and the dam foundation, or the possibility of chemical dissolution, anti-seepage treatment is required.
6.2.2 The tailings dam site should avoid unfavorable geological structures such as landslides, faults and fracture zones, and should avoid the lava-producing areas as much as possible. If technical and economic comparisons are still selected in the above-mentioned areas, or if they cannot be avoided, technical and economic arguments should be carried out and appropriate measures should be taken.
6.2.3 If there is a soil layer in the dam foundation where earthquake liquefaction may occur, the seismic liquefaction possibility evaluation shall be carried out according to the method of Appendix 1 of SDJ10-78, and the treatment shall be done.
6.3 The initial dam can be divided into permeable dams and impervious dams.
6.3.1 When the permeable dam is selected for the initial dam, a protective layer shall be designed outside the inclined wall of the upstream slope filter layer to prevent the ore discharge water from damaging the filter layer and causing the leakage of the ore slurry to pollute the environment.
6.3.2 When the initial dam is selected as a homogeneous earth dam or a combined earth dam, an drainage facility must be designed in the dam body to prevent the immersion line from escaping on the outer dam slope to ensure the safety of the dam.
6.3.3 In order to increase the stability of the tailings dam, the permeable rockfill dam should be preferably used under the same conditions. Only the lack of stone material in the local area can be selected only when the earth dam is reasonable.
6.4 Dam construction methods for tailings accumulation dams include upstream damming method, midline damming method and downstream damming method.
6.4.1 The choice of damming method should be based on the physical and mechanical properties of the tailings, the topographic and geological conditions of the tailings pond, the climatic characteristics, the seismic cracking degree, the rising speed of the tailings dam, and the methods of preventing and controlling environmental pollution. , determined by technical and economic argumentation. In the case of similar conditions, the upstream damming method should be given priority so that the slope of the dam can be protected in time.
6.4.2 The outer slope of the tailings accumulation dam should be designed with a stable slope protection, but each time the tailings are used to raise the dam body, the slope vegetation is immediately protected.
6.5 The superelevation of the tailings dam crest above the static water level of the tailings pond sedimentation tank is determined by the following formula:
Y=h+R+e+A
Where: the difference between the normal working water level of the Y-dam crest and the sedimentation tank, m;
A-tune flood depth, m, determined by flood control calculation;
R-maximum wave climbing on the dam slope, m;
E-maximum wind surface height, m;
A-safety elevation, m; determined in accordance with Table 2 of Article 4.2.
R, e can be calculated according to the relevant chapters of SDJ218. Generally, the inner slope of the tailings accumulation dam (that is, the natural sedimentary slope) is very slow, and the R and e values ​​are small and negligible.
6.6 The wetting line of the tailings dam is not allowed to escape on the downstream slope. For this purpose, drainage equipment must be installed in the dam to reduce the saturation line and pore water pressure, increase the stability of the dam and prevent the deformation and damage.
6.6.1 The drainage equipment of the tailings dam body must meet the following requirements;
a. Have sufficient drainage capacity to ensure free discharge of all water seepage downstream;
b. Designed according to the requirements of drainage filtration to ensure that the dam body and foundation soil do not cause osmotic damage;
c. The design principles of drainage equipment shall be implemented in accordance with the provisions of SDJ218.
6.7 The tailings dam is subjected to different loads from construction to completion, storage to the dam, and the soil also has different shear strength. The stability of the tailings dam in the early, late and specific mid-terms should be calculated separately. The content of the stability analysis is generally:
a. Stability of the downstream slope of the initial dam working time;
b. Stability of the overall downstream slope of the tailings dam (initial dam + accumulation dam) under normal seepage conditions;
c. Stability of the tailings dam during long-term rainfall and ore mining period when the whole dam is fully saturated (take safety factor according to very working conditions);
d. The inner slope of the initial dam of the tailings is generally not subject to stability calculation except for the discharge after the reservoir. The slope can be the same as the downstream slope.
6.8 The static stability calculation can adopt the Swedish arc method without inter-block force. For the continuous thick tailings mud interlayer, the improved arc method can be used. For high dams and some complicated situations, the safety factor of dam slope stability should be combined with the simplified Bishop method or other strict methods to calculate the safety factor of dam slope stability. The above calculations are made with reference to the SDJ218-84 appendix.
The physical and mechanical properties of tailings may have different differences for different processes. When it is impossible to obtain relevant data in the design stage, the design can learn the stability safety factor of the dam by drawing on the tailings characteristic data of similar hydrometallurgical plants. After a certain period of production by the hydrometallurgical plant (that is, when the initial dam is full and the tailings dam rises by about 10 m), the survey is carried out, data is obtained, and the design is revised.
After the dam level is determined according to Article 4.2, the anti-sliding stability safety factor of the dam slope is not less than the value specified in 7.3.8 of SDJ218-84.
6.9 The seepage water discharged from the dam body and foundation shall be collected and returned to the dam or sent to the sewage treatment plant.
6.10 In order to prevent the scouring slope of the dam slope caused by the overflow of rainwater, the dam surface drainage ditch shall be provided. The drainage ditch shall be provided at the joint between the dam body and the rock slope. The water collecting area shall include the water collecting area of ​​the bank slope, and the section size of the ditch. Determined by calculation.
6.11 Observation facilities shall be provided for tailings dams exceeding 30 m (including initial dams). The observations should include:
a, dam body settlement and displacement;
b. Dam body wetting line (designed together with the dam body drainage facility);
c. Permeate water flow and turbidity, pH and other harmful elements.
7 discharge of tailings pond
7.1 The tailings pond must have a reliable flood discharge structure, and the stormwater turbulence generated in the catchment area of ​​the tailings pond will be discharged outside the dam to ensure that no flooding will occur over the dam crest.
7.2 The flood standard of the tailings pond should be based on the grade determined by the tailings pond. Divided into normal operation (design frequency) and very use (check frequency). Flood standards should be determined in accordance with Table 1 of Article 4.2.
7.3 The rainfall duration of the tailings pond design flood is generally calculated in 24h.
7.4 Under normal circumstances, it is necessary to avoid using flood interception ditch to reduce the catchment area of ​​the tailings pond. If it is to be adopted, detailed technical and economic arguments must be carried out to ensure reliable and safe operation of the intercepting ditch.
7.5 A clear and striking water level gauge should be set up in the tailings pond sedimentation tank or on the drainage (Hong) structure.
7.6 It is strictly forbidden to use the sub-dams piled up by tailings as a means of flood control.
8 tailings pond drainage
8.1 The clarification water of the tailings reservoir should be returned to the water and metallurgical plant as much as possible to reduce the amount of wastewater discharged from the tailings and prevent environmental pollution.
8.2 The content of radioactive materials and harmful substances in the clarified water discharged from the tailings pond shall comply with relevant state regulations. Otherwise, wastewater treatment facilities should be designed for disposal.
9 tailings warehouse decommissioning
9.1 Decommissioning of tailings ponds must be decommissioned in accordance with relevant regulations. Decommissioned tailings must be stabilized and harmlessly disposed of to prevent radioactivity and other harmful substances from polluting water, soil, living things and the atmosphere.
The decommissioning design of the tailings pond must be undertaken by the design unit A and B.
The decommissioning design of the tailings pond should include:
a. Prepare a feasibility study report on the decommissioning of the tailings pond;
b. Prepare the preliminary design of the decommissioning of the tailings pond;
c. Prepare the design of the decommissioning construction drawing of the tailings pond.
9.2 The tailings pond after decommissioning should have sufficient safety and stability. Its level is determined by 4.2.
9.3 The tailings dam shall be decommissioned for stable accounting, and its anti-sliding stability safety factor shall not be less than the value specified in 7.3.8 of SDJ218-84. See 6.7 for the calculation method.
The physical and mechanical indicators of the tailings should be determined based on the surveyed measurements.
9.4 The retired tailings pond shall be provided with a permanent rainwater drainage structure to ensure that the storm flood generated within the catchment area of ​​the tailings pond is systematically exported outside the reservoir. The flood standard can be determined in accordance with Article 4.2. If the original drainage structure is used to vent the storm flood in the reservoir, it needs technical and economic argumentation. The original drainage (Hong) structures that have not been utilized shall be reliably sealed.
9.5 The tailings dam slope and beach surface of the retired tailings pond shall be covered. The materials used should be implemented in accordance with the principle of local materials, but should be determined after technical and economic argumentation. The cover layer should have safety measures to prevent wind erosion and rain erosion.
9.6 After the final remediation of the retired tailings pond, the surface decantation rate does not exceed 0.74 Bq/m 2 ·s.
9.7 Quality assurance during the decommissioning of the tailings mine shall be carried out in accordance with the relevant contents of the quality assurance in the GB14586 standard.
10 Radiation monitoring
10.1 Radiation monitoring of tailings ponds shall include radioactive measurement and analysis of the tailings pond before operation, during normal operation, under accident conditions and after decommissioning of the tailings pond.
10.2 The content of radiation monitoring mainly includes the types, concentrations and emissions of radionuclides and toxic and hazardous substances in the medium.
10.2.1 For radiation monitoring media and projects, see the relevant content in EJ432.
10.2.2 The selection of sampling points shall be determined according to the range of possible contamination of the gas and liquid effluent of the tailings reservoir and the degree of pollution. The location of the sampling points shall be selected in a representative place and reflect the type of pollutants. Emissions and environmental quality conditions.
10.2.3 Tracking, sampling and analysis should be carried out under the conditions of accidents in the tailings pond.
10.2.4 The measurement and analysis methods for radionuclides and toxic and hazardous substances in the medium shall be carried out according to the corresponding monitoring and analysis methods specified by the State.
10.2.5 Radiation monitoring period of tailings pond, see Table 4.
Table 4 Radiation monitoring period (number of times / month)
Sampling point | Monitoring content | ||||
222 Rn and its children | 210 Pb, 210 Po, 226 Ra, 230 Th, 238 U | Tail dust | γ | Non-radioactive toxic and hazardous substances | |
Tailings pond | 1/2 | 1/3 | 1/2 | 1/3 | |
Tailings reservoir environment | 1/2 | 1/3 | 1/2 | 1/1 | 1/3 |
10.3 Radiation monitoring quality assurance shall implement the relevant contents of GB11216 and EJ432 quality assurance.
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