DE1223963B - Evaporator device for radioactive solutions - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

G 21c

German class: 21 g - 21/20

Number: 1223 963

File number: C 33875 VIII c / 2 Ig

Filing date: September 9, 1964

Opening day: September 1, 1966

The invention relates to a vaporizer device for radioactive solutions, in particular for concentrating plutonium solutions.

It is often necessary to concentrate radioactive solutions to make a concentrated residual solution as well to get a little contaminated distillate. The main difficulty in concentrating such Solutions consists in the risk of becoming critical, which was previously the maximum volume to be treated at once the solution has narrowly limited.

The invention is based on the object of creating a relatively simple device, with which, with a high throughput and volume of the solutions, one can can achieve rapid concentration of radioactive solutions.

According to the invention, the vaporizer device consists of one of the ones to be concentrated Solution partially filled bladder, from at least one thermosiphon, the one below, with the Bottom of the bubble connected tube, a heating tube and an upper, tangential opening into the bubble Return tube comprises a solvent vapor removal tube connected to the top of the bladder, a feed pot for the solution to be concentrated and an outlet pot for the concentrated solution.

The bubble to be filled by the solution to be concentrated has a flattened cylindrical shape Shape made by a perforated and a layer of Raschig rings, e.g. B. made of boron glass, supporting plate stainless sheet metal is divided into two superimposed compartments, the bladder with the Thermosiphon through an annular tube containing at least in its inner part a neutron having absorbent material, is connected. Optionally, the outer part can consist of a die Neutron absorbing material exist.

According to a particular embodiment, the heating tubes have a bulged, advantageously having three lobes cross-section, each lobing of substantially is occupied along the axis of the bulge arranged heating devices.

The term "thermosiphon" used in the description is to be understood in a special sense, namely in such a way that the liquid circulation in it caused by its heating occurs essentially as a result of an ascending layer of boiling point that forms vapor bubbles. In this latter case, when the device is not in use, the liquid level only reaches the bottom of the flat bubble radioactive vaporizer device
solutions

Applicant:

Commissariat ä! 'Energie Atomique, Paris

Representative:

Dr. H. U. May, patent attorney,

Munich 2, Ottostr. 1 a

Named as inventor:

Pierre Auchapt,

Georges Bouzou,

Roger Sauteray, Bagnols / ceze, Gard (France)

Claimed priority:

France of 19 September 1963 (948 082),
dated January 30, 1964 (962 029)

or is even below the level of the upper tube leading back to the bladder. Just during operation, the boil, and the bladder, increase the volume of the liquid is partially filled by the liquid.

The invention is explained in more detail using two exemplary embodiments. It shows

F i g. 1 shows a schematic representation, partly in section, of a first embodiment of an inventive device trained evaporator device,

2 shows a schematic side view, partly in section, of a second embodiment of an inventive device trained evaporator device and

F i g. 3 is a schematic view in section along the line II-II in FIG. 2 of part of the FIG F i g. 2 shown device on an enlarged scale.

The in the F i g. The first embodiment of an evaporator device shown in FIG. 1 has a bladder 2 which is partially filled by the solution to be evaporated. The bladder 2 is provided in its lower part with a vertical pipe 4 and in its upper part with a vapor discharge line 6; one of the heating circuits 14 comprises a lower pipe 16 connected to the pipe 4, an ascending heating pipe 20 and an upper return pipe 22 which is tangential substantially at half height

609 658/323

3 4

the bladder 2 opens into this. The heating tube 20 tion of certain organic components of the solution consists of a tube of larger diameter to which carbon dioxide gas could occur. On the lower part than the tubes 16 and 22, in which a heating rod 28, the feed pot 78 are two lines vorz. B. of silicon dioxide attached. In the heating, one line 96 of which is the feed rod, electrical heating resistors suitable for the solution held in store in the container 98, which are fed by supply lines 30, are arranged by means of the pump 100 and the other line 102 . Between the heating rod 28 and which is used to supply the solution to the pipeline 72. Wall of the tube 20 there is a radial intermediate the discharge pot 80 also has two lines space, in which the to be concentrated solution environmentally on that work by overflow and runs of which, wherein the heating circulation of the liquid io a line 104 The lower part of the pot 80 connects to the tube 72 by creating an ascending film of and the other line causes liquid and vapor bubbles and the heating 106, the upper end 108 of which is at the level of the general tube 20 so from a mixture of liquid my liquid level 54 is located, with her and steam is flowing through it. At the lower steam end in a cooler 108 and the concentrate discharge 6, a heat exchanger 42 is connected to the outlet 110 opens. The height of these pots 78 closed, which plays the role of the condenser and and 80 is adjustable and allows on the one hand the legs outlet 44 for draining the liquid phase observation of the general liquid level and has. on the other hand, the regulation of this level in

The bladder 2 consists of a cylindrical part of the density of the concentrate.
50, which is covered by a spherical cap-shaped 20 In a preferred, for the concentration of oxal part 52. Both parts are made of stainless. acid mother liquors specific embodiment steel made. Slightly below the upper part of a device according to the invention, in the following Zylinders50, approximately at the level of the general to be by way of example with reference to the Fig. 1 _T liquid level 54 of the solution, a is written perforated, there is a bladder 2 made of a Sheet metal 56 made of stainless steel, arranged, which carries a 25 cylinder 50 made of stainless steel of 225 mm through a layer of glass Raschig rings, the schematic diameter and 40 mm height ^ the table for the liquid is indicated with 58; Purpose of this arrangement offers evaporation surface of 398 cm ² . 35 mm voltage is, the entrainment of liquid droplets in from the bottom of the bubble is a sheet metal, the gas phase and any risk of criticality made of stainless steel 3 mm thick, which has holes except in the exceptional case that the liquid level 30 has 8 mm diameter. This sheet helps prevent the bladder from rising. The upper part 52 is a layer 58 of 60 mm or more _: thickness of the bladder is, apart from the vapor discharge 6, 10 x 10 mm Raschig rings made of glass with 12.90 ° / ό provided with two further "pipe sockets, of which B ₂ O ₃ content, ie 4% boron.

one, 60, plays a role described below . Two pass through the heat exchanger 42 , while the other, 62, is provided with a tap 64, 35 stainless steel coils of 13 m in total, allowing decontamination. length, which has an exchanger surface of 4.150 cm ²

The discharge pipe socket 6 is to provide a knee 66 ; with a cooling water volume of 5251 / hour,

connected to a cyclone 68 of known design, a water inlet temperature of 74 of 20 ° C

which is used by centrifugal action to reduce the temperature and an exit temperature of 76 of 40 ° C

possibly 40 entrained by the vapor phase can produce 10,500 kcal / hour. be discharged.

Separate droplets of liquid. The pots 78 and 80 each consist of one aps

a very good steam decontamination glass tube of 75 mm diameter and 125 mm

factor and can - as far as possible of radio - height that is clamped between two metal flanges

active substances, especially plutonium, is exempt from the safety probes that connect to the

Obtain distillate. The bottom of the cyclone 68 is 45 pressure equalization and the inlet and outlet of the

carry through a curved tube 70 with the supply liquid.

connected pipe 72 through which the outflowing flow- The heating bundle is made entirely of stainless steel

liquids are fed into the heating circuit. built and carries three tubes 20, which are parallel to each other

The upper part of the cyclone 68 is with the heat on the other with its ends on two collecting plates 112

exchanger 42, which are welded in a known manner as 50 and for the passage of the liquid

Snake cooler is built and in which a double. Leave 20 mm thick openings free. In the

Stainless steel snake with a certain distance of at least 40 cm from the bladder

Immersion heaters 28 entering at 74 and exiting cooling elements 28 consist of quartz

amount of water is supplied, connected. and are with the help of six not shown, am

The supply and discharge of the solution takes place 55 bottom of each tube 20 welded corner plates by means of two similar pots 78 and 80, which are centered from. Seals, also not shown, made of glass tetrafluoroethylene clamped between two metal flanges are made in the upper part of the tubes 20 , with the upper flange securing this and the immersion heater 28 inserted, carrying measuring sensors 82, 84 and 86, 88 , which are inserted into the the distance between the wall of the top or bottom of the two pots is sufficient. ⁶ ° boiler and the pipe walls is 10 mm and the upper parts of these two pots are allowed to pass through liquid. The three heating rods are connected to elastic hoses 90 and 92, each with a power of 4 kW at a Hochsteiner joint, in a cooler 94 and from there voltage of 220 V, with their three resistors in the pipe socket 60 of the bladder 2 leading off are provided in a star connection to the secondary coil of a three-branch; This closes a pressure phase transformer with multiple output equalizing between the two pots and the bladder. Each immersion heater contains in its enables to get strong. Changes in the liquid's own circuit have a cut-off switch to avoid the level in the level of the liquid caused by the decomposition and discharge pots 78 and 80

Safety probes is controlled, and an alarming ammeter that completely stops the apparatus causes when a resistor is out of order.

By means of the three-phase transformer with an output of 30 kW you can change the heating output, by changing the voltage at the terminals of the heating resistors. Using one of You can determine the terminal voltage of each resistor with a hand-adjustable voltmeter.

Apart from heat losses, which are small and in are of the order of 3%, the volume of liquid distilled is essentially equal to electrical power supplied to the resistors. The following table gives the hourly distilled Volume as a function of the electrical power consumed.

power Distilling performance (kW) (1 H.) 12th 15.5 . 11 14.3 10 13.0 9 11.7. 8th 10.4 7th 9.1 6th 7.8 5 6.5 4th 5.2

30th

Several measurements of total heat recovery were made and the results were intermediate 93 and 97%.

The total amount of liquid contained in the device described is 4.41.

The measuring sensors 82 and 84 of the pot 78 serve to compensate for the fluctuations in the delivery rate of the metering pump 100 which may occur. When this dispensing rate decreases, the liquid level in the pot 78 drops and the probe 84 appears, causing the heating to be interrupted and a control lamp to light up. In contrast, if the delivery rate of the pump 100 increases, the liquid level in the pot 78 rises and reaches the sensor 82, thus causing the system to shut down and an alarm signal to light up. A corresponding safety system comes into operation in the pot 80 via the measuring sensors 86 and 88 in the event of crystallization in the concentrate. In addition, if crystallization occurs in the evaporator bubble itself and the liquid no longer circulates, the evaporation is interrupted, and safety devices are, for example, in the form of contact thermometers provided at the cooling water outlet of the heat exchanger 42 and on the tubes 14 of the heating bundle, which ensure the complete shutdown of the system and triggering an alarm signal cause S ₀ .

F i g. 2 shows a second embodiment of an evaporator device designed according to the invention, which is intended for installation in a “hot” cell separated into two compartments B and C by a tight wall A. Department B contains the actual evaporator and the devices intended for separating the liquid droplets entrained by the evaporated solvent and for returning them to the evaporator. Department C contains the ancillary equipment, such as the heat exchanger for recovering the solvent and equipment for supplying the solution to be concentrated and for discharging the concentrated solution.

The vaporizer device comprises a bladder 202 of substantially cylindrical shape and small height in relation to the diameter, which is composed of two pieces. During operation, the liquid flowing through to be concentrated occupies the bottom of this bubble in a sufficiently thin layer to eliminate the risk of becoming critical. Above the liquid flowing through, the bladder contains boron Raschig rings 236 in order to hold back droplets of the solution which may be entrained by the evaporated solvent.

In its lower part, the bladder 202 is provided with a pipe that is thin-walled in relation to its diameter and runs vertically. 204 and provided with a solvent vapor discharge line 206 in its upper part. The end of the conduit 204 is connected to a conduit 212 for filling the bladder with the liquid to be concentrated and for returning the droplets entrained by the vapor. This line is provided with a device (not shown) corresponding to the feed pot 78 in FIG. 1, in order to be able to regulate the liquid level of the bladder 222.

Two heating circuits 214 and 214 ' are connected to one another in the bladder 202 , but this number is not a limit. Since these circles are similar, only circle 214 will be described. The circle 214 consists of a lower tube 216 (FIGS. 2 and 3) with two branches 218 going out from a common trunk, two ascending heating tubes 220 and an upper tube 222, also with two branches 224, which are in a common one into the bladder 202 return trunk. Each pipe 220 is connected to two branches 218 and 224 .

The recovery of the concentrated solution is done by means of a with a not shown, the pot 80 of FIG. 1 corresponding outlet pot provided with suction devices connected line 226.

The heating tubes 220 consist of lines with a bulged cross section. An immersion heater 228, e.g. B. made of silicon dioxide, which is equipped with electrical heating resistors supplied by the supply lines 230 of suitable power, attached. Between the immersion heater 228 and the wall of the tube 220 there is an intermediate space in the radial direction through which the solution to be concentrated flows. When the immersion heater 228 is switched on, there is a liquid cycle in the sense of the arrows / because of the rising hot film of liquid and gas bubbles. This cycle can be accelerated by the provision of a pump, but this complication of the system is generally undesirable.

By using heating samples with a bulged and non-cylindrical cross-section one obtains a small volume for the same amount used for heating, which in the Is beneficial in terms of getting critical.

The lower and upper tubes 216 and 222 have a flattened rectangular cross-section, that is, their height is less than their width, in order to reduce the risks of criticality.

The circles 214 and 214 ′ shown in FIG. 2 open into the bladder 202 tangentially in opposite zones and in opposite directions.

To complete the separation of the liquid and vapor phase triggered by the boron-containing Raschig rings, the vapor discharge pipe 206 opens into a cyclone separator 234 of any conventional design. The evaporated solvent flows in the direction of the dashed arrows (FIG. 2) and is dehumidified by the swirling flow in the separator. The vapor phase, freed from liquid droplets that may be entrained, leaves the separator through a line 237 passed through the partition A and opening into a heat exchanger 242. The droplets retained in the cyclone return to the line 212 through a line 238 provided with a hydraulic shut-off device 240 (arrows f in Fig. 2). The condensed solvent is drawn off through the discharge nozzle 244 provided with a tap 246 .

The pressures in the supply and discharge pots (not shown) and in the bladder 202 are balanced by a line 248 (FIG. 2) corresponding to the line 90-92 of FIG.

To prevent neutron interactions between the various bodies of the Evaporator devices are certain walls with a material with a large neutron capture cross-section disguised. For example, the walls can be provided with plated cadmium foils.

Through the measures and arrangements described you can on the one hand for each component and on the other hand, for the entirety of the evaporator device with less bulkiness slightly below stay within the critical limit. The following numerical values are given as an example, those of a device for the continuous treatment of utonium solutions with an evaporation rate of the order of 601 / hour. correspond.

The characteristics of the device are such that each component, with regard to the solution it contains, meets at least one of the following conditions:

Volume less than 41;

Diameter smaller than 120 mm (cylindrical content;

Liquid layer thickness less than 40 mm.

The bladder 202 consists of a cylindrical vessel 450 mm in diameter, the bottom of which is covered by the solution up to a maximum layer thickness of 35 mm during operation and the upper part of which is occupied by boron-containing Raschig rings over a height of approximately 60 mm.

Each heating circuit comprises two heating tubes with a triple bulged cross-section, each of which is equipped with three immersion heaters of 4 kW. The lower and upper tubes 216 and 222 have a height of 20 mm and a length of mm, while the pipe socket 204 has an outer diameter of 160 mm and a thickness of mm.

Each component therefore fulfills at least one of the conditions to be below the critical limit stay. To prevent significant neutron interaction between the various Components a mutual distance of

ίο 400 mm, which is included in the device described is far exceeded. The presence of absorbent linings (cadmium or polyethylene) further reduces the interaction. In fact, the geometric design of the plant allows the placement of blocks of polyethylene or some material of the same kind between them same components in order to the absorption of neutrons and of in the cadmium by the neutrons to contribute generated gamma rays. Such blocks

so 250, 252 and 254 are shown schematically in phantom in FIGS. 2 and 3.

Claims (6)

Patent claims: 1. Evaporator device for radioactive solutions, characterized by a Bladder (2) to be partially filled by the solution to be concentrated, at least one thermosiphon, a lower tube (4) connected to the bottom of the bladder, a heating tube (20) and an upper return tube (22) opening tangentially into the bladder, one with the Solvent vapor discharge pipe (66) connected to the upper part (52) of the bladder (2), a feed pot (78) for the solution to be concentrated and an outlet pot (80) for the concentrated Solution. 2. Apparatus according to claim 1, characterized in that the bladder (2) is a flattened one has a cylindrical shape and with the lower tube (4) of the or each thermosiphon through a pipe with an annular cross-section is connected. 3. Apparatus according to claim 2, characterized in that the inner wall of the annular designed pipeline having a neutron absorbing material. 4. Apparatus according to claim 1, characterized in that the heating tube or the Heating tubes (20) have a bulged, advantageously three bulges Cross-section, with each bulge being substantially along the axis of the bulge arranged heating devices is occupied. 5. Apparatus according to claim 1, characterized in that the solvent vapor discharge (66) one after the other a cyclone (68), the lower part of which with the lower tube (72) of the thermosiphon is connected, and has a heat exchanger (42). 6. Apparatus according to claim 1, characterized in that that between the bubble, the heating tubes and / or the pipe sockets or pipelines neutrons and gamma rays absorbent components are arranged. 1 sheet of drawings 609 658/323 8.66 © Bundesdruckerei Berlin