CN214693382U - Tritium removing equipment for tritium-containing heavy water of nuclear power station based on rectification - Google Patents
Tritium removing equipment for tritium-containing heavy water of nuclear power station based on rectification Download PDFInfo
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Abstract
The invention relates to a rectification-based tritium removing device for tritium-containing heavy water in a nuclear power station, which is a heavy water upgrading tower. The tritium removal equipment is used for a tritium removal process, has high safety, high automation degree and low energy consumption, can effectively reduce the tritium specific activity of tritium-containing heavy water of a nuclear power station, reduces the high tritium operation risk of a unit, and creates convenient conditions for pressure pipe replacement, thereby reducing the irradiation dose in personnel, reducing the environmental emission and protecting the public and the environment; high specific activity heavy water which cannot be used by the unit is converted into low specific activity heavy water, so that considerable economic benefit is generated for the nuclear power station; in addition, the method can be further extended to other fields needing to reduce the tritium specific activity of the nuclear power station, such as separation of super-semi-heavy water and light water, and the like, and has wide application prospect.
Description
Technical Field
The invention belongs to the technical field of nuclear power station tritium emission control, and particularly relates to a rectification-based tritium-containing heavy water tritium removal device for a nuclear power station.
Background
The heavy water reactor nuclear power station takes natural uranium as nuclear fuel and takes heavy water as a moderator. Heavy water as moderator inUnder neutron irradiation, according to nuclear reaction:2H+n→3h + γ, tritium is continuously generated. Heavy water reactor nuclear power plants produce large amounts of tritium annually. Tritium is a low toxicity nuclide that emits beta particles with a maximum energy of 18keV and has a half-life of 12.3 years. This radiation has a short range and so tritium presents little external radiation hazard to humans. Tritium molecules such as HT, DT, T due to monomeric form2The amount absorbed by lung tissue is less than one in a thousand and the amount through the skin is very small, thus being very harmful to the human body. But tritium oxides, e.g. HTO, DTO, T2O, etc. are more harmful than the same amount of tritium molecules in the form of monomers. Tritium-containing water vapor is almost completely absorbed by lung tissue and skin and distributed throughout the body to cause internal irradiation. Tritium has an effective half-life in vivo of 12 days. Tritium discharged from the heavy water reactor nuclear power station enters the human body through respiration and skin permeation, and edible vegetables, meat, animal products and marine products enter the human body, so that the irradiation in the human body constitution generates the influence of the whole body uniformity. Therefore, it is important to reduce the amount of tritium discharged, and the fundamental measure for reducing the tritium specific activity of heavy water as a moderator is to reduce the amount of tritium discharged.
The reduction of the tritium specific activity of heavy water as a moderator in a heavy water reactor nuclear power plant is a requirement for safe and stable operation of the heavy water reactor nuclear power plant. Along with the increase of the operation and stacking years of the heavy water stacking unit, the tritium specific activity of heavy water serving as a moderator is increased year by year, and the internal irradiation dose of workers is also gradually increased. Under the condition of high tritium operation of the heavy water reactor nuclear power station, even if tiny heavy water leakage occurs, tritium level in a nuclear island plant can be obviously increased, and the amount of discharged environmental tritium can be obviously increased, so even under the condition that leakage does not directly affect the operation of a heavy water reactor unit, shutdown maintenance is generally considered. During the high tritium operation of the heavy water reactor nuclear power station, if a heavy water leakage event serving as a moderator occurs, the annual operation index of the power station can be broken through, even the emission limit value regulated by the state is exceeded, and the influence on the surrounding environment and the negative influence on the society are great.
The tritium specific activity of heavy water used as a moderator in a heavy water reactor power station is reduced, and the requirement for replacement work of a pressure pipe of a heavy water reactor unit is also met. The heavy water reactor unit needs to regularly change the pressure pipe, if not remove tritium, then the moderator system washes work during the pressure pipe is changed and will lead to liquid tritium to discharge by a wide margin and surpass the national emission limit value.
At present, key equipment for treating heavy water containing tritium is monopolized by a few countries such as Canada and Korea.
The rectification technology is a mature separation technology, mainly realizes separation by utilizing the boiling point difference between separated components, and has the characteristics of mature process, relatively simple system, mature equipment, easy implementation of operation, maintenance and overhaul work and the like. The components separated are generally carried out using conventional rectification techniques, with boiling point differences generally above 2 ℃. For tritiated heavy water, D2The boiling point of O at normal pressure is 101.43 ℃, the boiling point of DTO at normal pressure is 101.48 ℃, DTO and D2The boiling point difference of O is very small, and the separation difficulty is high. At present, the rectification technology for DTO and D is not adopted at home and abroad2And O, equipment for separating.
Disclosure of Invention
Based on the equipment, the invention provides a rectification-based tritium removing equipment for tritium-containing heavy water in a nuclear power station, and the equipment is a heavy water upgrading tower.
Preferably, heavy water upgrading tower includes feeding circuit, rectification return circuit, bottom product return circuit, top product return circuit and vacuum circuit, feeding circuit includes feeding case, feeding control valve and feeding evaporimeter, the rectification return circuit includes rectifying column and circulating pump, the rectifying column includes rectifying column and circulating pump, feeding bottom of the case portion is connected with feeding flow control valve, feeding evaporimeter and rectifying column in proper order, inside regular packing and the distributor of copper oxide CY-700 type that all is equipped with of rectifying column, top condenser and top cold trap are equipped with at the rectifying column top, top cold trap respectively with vacuum circuit and top product return circuit connection, rectifying column tower cauldron is equipped with the re-heater, the rectifying column bottom is connected with the circulating pump, the circulating pump is connected with re-heater and bottom product return circuit respectively.
The working principle is as follows: sending tritium-containing heavy water into a feeding box, sending into a feeding evaporator under the action of gravity, and introducing into the feeding evaporatorHeating steam is added to ensure that the heavy water is heated and vaporized to form heavy water steam which is sent into the rectifying tower; the vacuum loop maintains the interior of the rectifying tower in a negative pressure state, and assists steam to be condensed and discharged to a waste liquid treatment system of a power station; the auxiliary steam of the power station is introduced into the tube side of the tower kettle reheater, so that the mixed liquid on the shell side is vaporized and enters the rectifying tower to ascend along the tower body, and the ascending mixed steam contains D2O and heat are transferred to the mixture on the filler layer, and D on the filler2And (3) evaporating the O, then ascending to the previous packing layer, simultaneously condensing DTO contained in the mixed steam on the packing layer when meeting cold, refluxing to the next packing layer, finally condensing the low tritium heavy water obtained at the tower top, sending the condensed low tritium heavy water into a top product loop, and sending the high tritium heavy water obtained at the tower bottom into a bottom product loop.
Preferably, the rectifying column includes upper tower, lower floor's tower, backwash pump and steam pipe, the regular packing of copper oxide CY-700 type and distributor are all equipped with to upper tower and lower floor's tower inside, liquid between upper tower and the lower floor's tower passes through the backwash pump and connects, gas between upper tower and the lower floor's tower passes through the steam pipe and connects, top condenser and top cold trap are equipped with to upper tower top, lower floor's tower cauldron is equipped with the re-heater, lower floor's tower bottom is connected with the circulating pump, upper tower is connected with the feeding evaporimeter.
Preferably, the top product loop comprises a top product cooler, a top product tank and a top product pump, the top product cooler, the top product tank and the top product pump being connected in series, the top product cooler being connected to a top cold trap. And the top product pump is connected with the unit and used for transmitting the low tritium heavy water in the top product box back to the unit.
Preferably, the bottom product loop includes a bottom product evaporator, a bottom product condenser, a bottom product cooler, a bottom product tank, a bottom product pump and a bottom cold trap, the bottom product evaporator is connected with the circulating pump and the bottom product condenser respectively, the bottom product condenser is connected with the bottom product cooler and the bottom product tank in sequence, the bottom product tank top is connected with the bottom cold trap, and the bottom product tank bottom is connected with the bottom product pump. The bottom cold trap is connected with a chimney, the bottom product pump is connected with the unit, and concentrated high tritium heavy water in the bottom product box is transmitted to the unit for storage.
Preferably, the vacuum circuit comprises a vacuum pump connected to the top cold trap.
Preferably, the heavy water upgrading tower further comprises a condensate loop comprising a condensate tank connected to the feed evaporator.
Compared with the prior art, the invention has the following advantages:
1. the tritium-containing heavy water tritium removal equipment based on rectification can reduce the tritium specific activity of tritium-containing heavy water in a nuclear power station through the rectification technology, reduce the running risk of high tritium of a unit, and create convenient conditions for pressure pipe replacement, thereby reducing the irradiation dose in personnel, reducing the environmental emission and protecting the public and the environment.
2. The tritium-containing heavy water tritium removal equipment based on rectification can convert high-specific-activity heavy water which cannot be used by a unit into low-specific-activity heavy water through the rectification technology, and generates considerable economic benefit for a nuclear power station.
3. The tritium-containing heavy water tritium removal equipment based on rectification has high automation degree, less required personnel and low operation cost.
4. When the tritium-containing heavy water tritium removal equipment based on rectification is used for the tritium-containing heavy water tritium removal process based on rectification, the tritium-containing heavy water tritium removal equipment belongs to a pure physical process, does not have electrolysis, catalytic exchange and hydrogen-oxygen compound processes, does not have hydrogen explosion risk, belongs to negative pressure operation, and has lower tritium gas leakage probability and higher safety.
5. When the tritium-containing heavy water tritium removal equipment based on rectification is used for the tritium-containing heavy water tritium removal process based on rectification, auxiliary steam of a power station is used, and because the temperature is not high (about 40-60 ℃), the energy consumption is relatively low for a nuclear power station, and the effective utilization of the auxiliary steam of the power station can be realized.
6. The tritium-containing heavy water tritium removal equipment based on rectification can also be applied to other nuclear power plants needing to be loweredThe field of tritium specific activity has wide application prospect, such as application to ultra-half heavy water (HTO) and light water (H)20) The separation of (2) realizes concentration times of dozens of times and concentration of higher tritium water, thereby greatly degrading the specific activity of the tritium of the unit and creating a safer method for controlling tritium discharge for inland construction of nuclear power stations.
7. The tritium-containing heavy water tritium removal equipment based on rectification fills the blank of domestic tritium-containing heavy water tritium removal equipment, and breaks through monopoly of foreign equipment.
Drawings
FIG. 1 is a schematic diagram of a heavy water upgrading tower overall circuit;
FIG. 2 is a schematic diagram of the heavy water upgrading column overhead product loop;
figure 3 is a schematic of the bottom product loop of the heavy water upgrading column.
Wherein, 1-a feeding box, 2-a feeding evaporator, 3-an upper tower, 4-a lower tower, 5-a top condenser, 6-a top cold trap, 7-a top product cooler, 8-a top product box, 9-a vacuum pump, 10-a bottom product evaporator, 11-a bottom product condenser, 12-a bottom product cooler, 13-a bottom product box, 14-a bottom cold trap, 15-a top product analyzer, 16-a reheater, and 17-a bottom product analyzer.
Detailed Description
In the embodiment, the heavy water reactor nuclear power station adopts a Qinshan three-phase heavy water reactor nuclear power station, which is two CANDU-6 heavy water reactor nuclear power units introduced from Canada in China, natural uranium is used as nuclear fuel, and heavy water is used as a moderator and a coolant.
The tritium specific activity of heavy water used as a moderator in two CANDU-6 heavy water reactor units of the Qinshan three-stage heavy water reactor nuclear power station is reduced, and the requirement for safe and stable operation of the two CANDU-6 heavy water reactor units is met. The main manifestations are as follows:
1. risk of personnel dosing: along with the increase of the operation and stacking years of two CANDU-6 heavy water reactor units of the Qinshan three-stage heavy water reactor nuclear power station, the tritium specific activity of heavy water serving as a moderator is increased year by year, the internal irradiation dose of workers is gradually increased, and the limit pressure of the tritium discharge of a power station is increased more and more.
2. Personnel receive excessive internal exposure risks in case of an accident: according to the tritium specific activity condition of heavy water currently used as a moderator in the Qinshan three-phase heavy water reactor nuclear power station, 2 g of heavy water taken as the moderator by workers can cause the internal irradiation dose to exceed the national limit (50mSv-INSAG nuclear secondary event). With the increasing tritium specific activity, the heavy water intake required for breaking through the same limit value is less and less, and the pressure of radiation protection of power stations is increasing.
3. And (4) safe operation risk of the power station: under the condition of high tritium operation of the existing Qinshan three-stage heavy water reactor nuclear power station, even if tiny heavy water leakage occurs, the tritium level in a nuclear island plant can be obviously increased, and the discharge dosage of environment tritium can be obviously increased. Shutdown maintenance is therefore usually considered even in cases where the leak does not have a direct effect on the operation of the unit. In recent years, heavy water leakage occurs to a CANDU-6 heavy water reactor unit for many times, so that the tritium level of a factory building rises to exceed a limit value, and the condition of shutdown and minor repair is caused. During the high tritium operation of the power station, if a moderator heavy water leakage event occurs, the annual operation index of the power station can be broken through, even the emission limit value specified by the state is exceeded, and the influence on the surrounding environment and the negative influence on the society are great.
4. Attention of regulatory authorities: after the accident of fukushima, the national nuclear safety administration carries out a series of safety checks on operating nuclear power plants. How to effectively prevent the high tritium operation risk of two CANDU-6 heavy water reactor units of the Qinshan three-stage heavy water reactor nuclear power station is set as key work. At present, the state environmental protection department has paid much attention to the tritium discharge condition of the Qin mountain three-phase heavy water reactor nuclear power station. The national limit on the tritium discharge of heavy water reactor power stations is also stricter and stricter. The tritium specific activity of heavy water used as a moderator in two CANDU-6 heavy water reactor units of the Qinshan three-stage heavy water reactor nuclear power station is reduced, and the requirement for replacing the pressure pipe is also met: according to design regulations, two CANDU-6 heavy water reactor units of the Qinshan three-phase heavy water reactor nuclear power station need to replace pressure pipes. If tritium removal is not performed, a moderator system flush operation during pressure pipe replacement will result in liquid tritium emissions that greatly exceed national emission limits.
The invention provides a rectification-based tritium removing device for tritium-containing heavy water in a nuclear power station, which is a heavy water upgrading tower.
The heavy water upgrading tower is an important facility of the Qinshan three-phase heavy water reactor nuclear power station and is designed for separating D2O and H2And O (the boiling point difference between D2O and H2O is 1.43 ℃, the separation coefficient is larger, and the separation is easier) is used for treating degraded heavy water generated in the daily operation process of the power station. Due to D2The boiling point difference between O and DTO is extremely small, the separation difficulty is high, and D cannot be realized through a heavy water upgrading tower of a Qinshan three-stage heavy water reactor nuclear power station under the conventional operation condition2And separating O and DTO. The invention uses heavy water (D) containing tritium2O and DTO) is sent into a heavy water upgrading tower of the Qinshan three-phase heavy water reactor nuclear power station, the operation pressure of the heavy water upgrading tower is adjusted to be in a negative pressure state, and D is realized2The separation of O and DTO is the first innovation.
Referring to fig. 1-3, the heavy water upgrading tower includes feeding return circuit, rectification return circuit, bottom product return circuit, top product return circuit and vacuum circuit, feeding return circuit includes feeding case 1, feed control valve and feeding evaporimeter 2, the rectification return circuit includes rectifying column and circulating pump, feeding case 1 bottom is connected with feed flow control valve, feeding evaporimeter 2 and rectifying column in proper order, rectifying column inside all is equipped with the regular packing of copper oxide CY-700 type and distributor, top condenser 5 and top cold trap 6 are equipped with to the rectifying column top, top cold trap 6 is connected with vacuum circuit and top product return circuit respectively, rectifying column cauldron is equipped with reheater 16, the rectifying column bottom is connected with the circulating pump, the circulating pump is connected with reheater 16 and bottom product return circuit respectively.
The working principle is as follows: sending tritium-containing heavy water into a feeding box, then sending the tritium-containing heavy water into a feeding evaporator under the action of gravity, introducing heating steam into the feeding evaporator, and heating and vaporizing the heavy water to form heavy water steam and sending the heavy water steam into a rectifying tower; the vacuum loop maintains the interior of the rectifying tower in a negative pressure state, and assists steam to be condensed and discharged to a waste liquid treatment system of a power station; the auxiliary steam of the power station is introduced into the tube side of the tower kettle reheater, so that the mixed liquid on the shell side is vaporized and enters the rectifying tower to ascend along the tower body, and the ascending mixed steam contains D2O and heat are transferred to the packing layerAnd D on the filler2And (3) evaporating the O, then ascending to the previous packing layer, simultaneously condensing DTO contained in the mixed steam on the packing layer when meeting cold, refluxing to the next packing layer, finally condensing the low tritium heavy water obtained at the tower top, sending the condensed low tritium heavy water into a top product loop, and sending the high tritium heavy water obtained at the tower bottom into a bottom product loop.
Preferably, the rectifying column includes upper tower 3, lower floor's tower 4, backwash pump and steam pipe, upper tower 3 and lower floor's tower 4 are inside all to be equipped with the regular packing of copper oxide CY-700 type and distributor, liquid between upper tower 3 and the lower floor's tower 4 passes through the backwash pump and connects, gas between upper tower 3 and the lower floor's tower 4 passes through the steam pipe and connects, top condenser 5 and top cold trap 6 are equipped with at upper tower 3 top, lower floor's tower 4 tower cauldron is equipped with reheater 16, lower floor's tower 4 bottom is connected with the circulating pump, upper tower 3 is connected with feeding evaporimeter 2.
Preferably, the top product circuit comprises a top product cooler 7, a top product tank 8 and a top product pump, the top product cooler 7, the top product tank 8 and the top product pump being connected in series, the top product cooler 7 being connected to the top cold trap 6. And the top product pump is connected with the unit and used for transmitting the low tritium heavy water in the top product box back to the unit.
Preferably, the bottom product loop comprises a bottom product evaporator 10, a bottom product condenser 11, a bottom product cooler 12, a bottom product tank 13, a bottom product pump and a bottom cold trap 14, the bottom product evaporator 10 is connected with the circulating pump and the bottom product condenser 11 respectively, the bottom product condenser 11 is connected with the bottom product cooler 12 and the bottom product tank 13 in sequence, the top of the bottom product tank 13 is connected with the bottom cold trap 14, and the bottom of the bottom product tank 13 is connected with the bottom product pump. The bottom cold trap 14 is connected with a chimney, the bottom product pump is connected with a unit, and concentrated high tritium heavy water in the bottom product box is transmitted to the unit for storage.
Preferably, the vacuum circuit comprises a vacuum pump 9, the vacuum pump 9 being connected to the top cold trap 6.
The equipment provided by the invention is used for two CANDU-6 heavy water reactor units of a Qinshan three-phase heavy water reactor nuclear power station, and has the following benefits:
1. heavy water benefit: due to the characteristics of high operating pressure (10MPa), multiple interfaces with an external system and the like, according to the annual statistics of the Qinshan three-phase heavy water reactor nuclear power station, the loss of heavy water leaked into the environment by a main heat transmission system (PHT) of two CANDU-6 heavy water reactor units of the Qinshan three-phase heavy water reactor nuclear power station due to normal operation or maintenance opening operation and the like is about 1.2 t-1.5 t every year. Due to factors such as maintenance, equipment defects, incomplete isolation of high and low tritium boundaries in a factory building and the like, long-term cross contamination of high and low tritium heavy water in the power station part of the Qinshan three-phase heavy water reactor nuclear power station is caused. About 1.0t of main heat transfer system (PHT) low tritium heavy water is polluted by high tritium and converted into moderator grade high tritium heavy water to be unusable every year. According to the design, the target reserve of the moderator grade high tritium heavy water of the power station is 10t, but up to now, the reserve of the existing moderator grade high tritium heavy water of the power station reaches 37t (increased from 8t at the initial operation stage of the unit to 37t at the current stage), exceeds the target value of 27t and is continuously rising due to the fact that the low tritium heavy water is continuously converted into the high tritium heavy water. The power station can convert about 1.0t of low tritium heavy water into high tritium heavy water every year and cannot use the high tritium heavy water, and considering factors such as service life prolonging after replacement of a unit pressure pipe, the heavy water is not used for 67t (the total loss amount of the high tritium moderator heavy water is less than 50kg every year and fresh heavy water purchased by the power station is used for supplementing main heat transmission heavy water) from about 40 years multiplied by 1.0 t/year to about 27t at the end of the service life of the power station from 2019. Therefore, if the heavy water with high tritium can be converted into heavy water with low tritium heat transfer, a power station can save a large amount of capital. If the heavy water rectification facility is built for production, the unusable 67t high tritium heavy water generated in the service life of the unit can be converted into main heat transmission (low tritium heavy water) for full utilization, and about 67t multiplied by 400 ten thousand yuan/t is 26800 ten thousand yuan for the capital saving of a power station.
2. Heavy water upgrade saved fuel bundle gains:
(1) after the facility is built, the concentration of the heavy water of the moderator can be improved, and the fuel cost is greatly saved. After the facility is built, the device can be used for reducing the specific activity of heavy water and tritium and also can be used for improving the concentration of heavy water of a moderator, thereby not only solving the hidden danger of pollution, but also greatly saving the fuel cost. According to calculation, the improvement of the purity of the moderator brings about the increase of the excessive reactivity of the reactor core or the improvement of the discharge fuel consumption of the unit by referring to the foreign conditions. For each 0.01 at% increase in the purity of the moderator, a reactivity of 0.34mk can be introduced into the core, and if the core excess reactivity is maintained, the discharge fuel consumption is increased by about 40MWd/Tu, the discharge fuel consumption is increased by about 0.5, and about 0.5% of fuel cost can be saved. Two trains will save 500 fuel rods each year.
(2) And (3) revenue calculation: the concentration of heavy water of a moderator of two heavy water reactor units of three-core in Qinshan is 99.85 wt% at present, if the concentration is increased to 99.95 wt%, a heavy water rectification facility is designed according to the service life of 40 years, the operation is conservative according to 20 years (considering that the previous 8 years of the facility are used for removing tritium, the concentration of tritium is reduced to a lower level, the facility is used for upgrading the heavy water of the moderator, considering that the upgrading needs about 5 years, and simultaneously, the factors such as the reduction of about 0.01 wt% per year after the upgrading to 99.95 wt%, and the like are conservative and the operation is calculated according to 20 years), the operation time of the unit after the heavy water upgrading is carried out, and each fuel is conservative according to 4.5 ten thousand yuan of RMB, so that the benefits of 500 × 45000 × 20 ═ 4.5 billion yuan can be saved.
3. Economic benefits generated by treating high-level solid waste: the drying agent of the heavy water vapor recovery system needs to be replaced every 5 years in the power station, and the replacement amount is 40m3The amount of replacement will exceed 500m over the life of the plant3This also excludes about 2m generated by annual filter cartridge changes in power stations3The solid waste of (2). These desiccants and solid wastes are contaminated with high tritium and can only be disposed of as high-level solid wastes. The treatment cost is about 8 ten thousand yuan/m 310 ten thousand yuan/m3. Thus, the capital cost of treating these solid wastes throughout the life of the plant will be in excess of 4000-5000 ten thousand dollars. If the heavy water is subjected to tritium removal, the waste can be treated as low-level waste, so that the treatment cost of 4000-5000 ten thousand yuan can be saved.
4. Inland construction of a pressurized water reactor: the technology of the invention can also be used for reducing the specific activity of the coolant tritium of the pressurized water reactor, and creates conditions for inland construction of nuclear power stations. A certain amount of tritium-containing waste liquid can be discharged from a primary circuit of a pressurized water reactor power station (about 1000 tons of tritium-containing waste liquid can be expected to be generated by one million kilowatt unit), and if the tritium-containing waste liquid is directly discharged, the requirement that the tritium specific activity at one kilometer position of a water outlet is lower than 100Bq/kg can not be met by the national requirement. If the storage decay is directly carried out, a large number of storage tanks are needed, the investment is large, the occupied area is large, and the management is difficult. After the technology of the invention is adopted, the waste liquid can be concentrated and volume-reduced (the concentration ratio can reach dozens, and the tritium removal efficiency can reach more than 99 percent), thereby greatly reducing the cost of storage and subsequent treatment.
5. The technology of the invention breaks monopoly of foreign tritium removal equipment and solves the problem of high tritium operation of the heavy water reactor unit.
Example 1
1. Starting the heavy water upgrading tower, starting the vacuum pump 9, confirming that the absolute vacuum degree at the top of the upper tower 3 is reduced to 13.3kPa, starting the reflux pump and the circulating pump, and confirming that the rectifying tower enters into a full reflux mode to operate;
2. sending heavy water containing tritium into a feeding box; manual feeding is carried out, so that feeding is stopped after the liquid levels of the bottom kettles of the upper-layer tower 3 and the lower-layer tower 4 reach 65%, and the loading requirement is met; after half an hour, confirming that the liquid level of the bottom kettles of the upper-layer tower 3 and the lower-layer tower 4 is reduced to 35%;
3. adjusting the absolute vacuum degree of the upper layer tower 3 to be reduced from 13.3kPa to 11.0 kPa; closely monitoring the temperatures of the top of the upper layer tower and the bottom of the lower layer tower, and confirming that the temperature of the top of the upper layer tower is gradually reduced to 49 ℃; sampling once every 4 hours, analyzing the concentration of heavy water tritium at the top of the upper layer tower and the concentration of heavy water tritium at the bottom of the lower layer tower, and finding that the concentration of heavy water tritium at the top of the upper layer tower slightly decreases and the concentration of heavy water tritium at the bottom of the lower layer tower slightly increases, but is not obvious;
4. continuously adjusting the absolute vacuum degree of the upper-layer tower 3, and reducing the absolute vacuum degree from 11kPa to 8 kPa; closely monitoring the temperatures at the top of the upper column 3 and the bottom of the lower column 4, confirming that the temperature at the top of the upper column 3 is gradually lowered to 46 ℃; sampling every 4 hours, analyzing and recording the concentration of heavy water tritium at the top of the upper-layer tower 3 and the concentration of heavy water tritium at the bottom of the lower-layer tower 4, and finding that an obvious separation phenomenon exists;
5. continuously adjusting the absolute vacuum degree of the upper-layer tower 3, and reducing the absolute vacuum degree from 8kPa to below 6 kPa; closely monitoring the temperatures at the top of the upper column and the bottom of the lower column, confirming that the temperature at the top of the upper column gradually decreases to below 39 ℃; sampling every 4 hours, analyzing and recording the concentration of heavy water tritium at the top of the upper layer tower and the concentration of heavy water tritium at the bottom of the lower layer tower, and finding that the separation rate is accelerated.
Example 1 shows that a heavy water upgrading column can achieve D with a very small boiling point difference by rectification technology2And (3) separating O and DTO, finally reducing the concentration of heavy water tritium at the top of the upper-layer tower 3 to be less than 20% of the feeding amount, and concentrating the concentration of heavy water tritium at the bottom of the lower-layer tower 4 to be more than 5 times of the feeding amount, so that the good separation is realized, the separation speed is accelerated along with the increase of the vacuum degree, and the separation effect is better.
Example 2
1. Starting the heavy water upgrading tower, starting the vacuum pump 9, and confirming that the absolute vacuum degree at the top of the upper-layer tower 3 is up to 13.3 kPa; starting a reflux pump and a circulating pump, and confirming that the rectifying tower enters a cascade mode to operate;
2. adjusting the set value of the absolute vacuum degree at the top of the upper-layer tower 3 to 6-8KPa, and confirming that the absolute vacuum degree of the upper-layer tower 3 is 6-8 KPa; sending tritium-containing heavy water with the heavy water concentration of 99.85 wt% into a feeding box 1; confirming that the liquid level of the feeding evaporator reaches 65%, and opening a heating steam valve; adjusting the feeding rate to 10-20kg/h, wherein the feeding point is a valve of the upper-layer tower I; adjusting the top discharging rate to 5-10 kg/h; and sampling and analyzing the change conditions of the specific activities of the heavy water and the tritium at the top of the upper-layer tower 3 and the bottom of the lower-layer tower 4.
As a result: the specific activity of heavy water tritium at the top of the upper-layer tower 4 is reduced to be below 10-20% of the fed material, and the specific activity of heavy water tritium at the bottom of the lower-layer tower 4 is more than 3 times of the fed material.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (6)
1. A tritium removing device for tritium-containing heavy water in a nuclear power station based on rectification is characterized in that the device is a heavy water upgrading tower, the heavy water upgrading tower comprises a feeding loop, a rectifying loop, a bottom product loop, a top product loop and a vacuum loop, the feeding loop comprises a feeding box, a feeding control valve and a feeding evaporator, the rectifying loop comprises a rectifying tower and a circulating pump, the bottom of the feeding box is connected with a feeding flow control valve, a feeding evaporator and a rectifying tower in sequence, the rectifying tower is internally provided with copper oxide CY-700 structured packing and a distributor, the top of the rectifying tower is provided with a top condenser and a top cold trap which are respectively connected with a vacuum loop and a top product loop, the rectifying tower is characterized in that a reheater is arranged in the tower kettle of the rectifying tower, the bottom of the rectifying tower is connected with a circulating pump, and the circulating pump is respectively connected with the reheater and a bottom product loop.
2. The nuclear power plant tritium-containing heavy water tritium removal equipment based on rectification as claimed in claim 1, wherein the rectification tower comprises an upper tower, a lower tower, a reflux pump and a steam pipe, the upper tower and the lower tower are both internally provided with copper oxide CY-700 structured packing and a distributor, liquid between the upper tower and the lower tower is connected through the reflux pump, gas between the upper tower and the lower tower is connected through the steam pipe, the top of the upper tower is provided with a top condenser and a top cold trap, the lower tower kettle is provided with a reheater, the bottom of the lower tower is connected with a circulating pump, and the upper tower is connected with a feeding evaporator.
3. The rectification-based heavy water tritium removal equipment for nuclear power plants containing tritium based on the nuclear power plant as recited in claim 1, wherein the top product loop comprises a top product cooler, a top product tank and a top product pump, the top product cooler, the top product tank and the top product pump are connected in sequence, and the top product cooler is connected with the top cold trap.
4. The rectification-based tritium-containing heavy water tritium removal equipment for nuclear power plants as claimed in claim 1, wherein the bottom product loop comprises a bottom product evaporator, a bottom product condenser, a bottom product cooler, a bottom product tank, a bottom product pump and a bottom cold trap, the bottom product evaporator is respectively connected with the circulating pump and the bottom product condenser, the bottom product condenser is sequentially connected with the bottom product cooler and the bottom product tank, the top of the bottom product tank is connected with the bottom cold trap, and the bottom of the bottom product tank is connected with the bottom product pump.
5. The rectification-based heavy tritium removal equipment for tritiated water in nuclear power plants according to claim 1, wherein the vacuum loop comprises a vacuum pump connected to a top cold trap.
6. The apparatus for tritium removal from heavy water containing tritium for a nuclear power plant based on rectification according to any one of claims 1 to 5, characterized in that the heavy water upgrading tower further comprises a condensed water loop, the condensed water loop comprises a condensed water tank, and the condensed water tank is connected with a feed evaporator.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202022008315.4U CN214693382U (en) | 2020-09-14 | 2020-09-14 | Tritium removing equipment for tritium-containing heavy water of nuclear power station based on rectification |
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| CN202022008315.4U CN214693382U (en) | 2020-09-14 | 2020-09-14 | Tritium removing equipment for tritium-containing heavy water of nuclear power station based on rectification |
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| CN214693382U true CN214693382U (en) | 2021-11-12 |
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