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WO1995026556A1 - Sechage de dechets radioactifs ou toxiques humides ou d'autres dechets humides dangereux - Google Patents

Sechage de dechets radioactifs ou toxiques humides ou d'autres dechets humides dangereux Download PDF

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Publication number
WO1995026556A1
WO1995026556A1 PCT/EP1995/001123 EP9501123W WO9526556A1 WO 1995026556 A1 WO1995026556 A1 WO 1995026556A1 EP 9501123 W EP9501123 W EP 9501123W WO 9526556 A1 WO9526556 A1 WO 9526556A1
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WO
WIPO (PCT)
Prior art keywords
container
waste
radioactive
dryer
drying chamber
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/EP1995/001123
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English (en)
Inventor
Brian Thompson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sellafield Ltd
Original Assignee
British Nuclear Fuels PLC
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Filing date
Publication date
Application filed by British Nuclear Fuels PLC filed Critical British Nuclear Fuels PLC
Publication of WO1995026556A1 publication Critical patent/WO1995026556A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
    • G21F9/04—Treating liquids
    • G21F9/06—Processing
    • G21F9/08—Processing by evaporation; by distillation
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
    • G21F9/04—Treating liquids
    • G21F9/20—Disposal of liquid waste
    • G21F9/22—Disposal of liquid waste by storage in a tank or other container

Definitions

  • the present invention is concerned with a dryer and method for drying wet radioactive, toxic or other hazardous waste.
  • the description hereinbelow relates solely to drying radioactive waste, because that is the application for which the invention was developed.
  • the dryer and drying method are equally applicable to drying wet toxic, biologically dangerous or other hazardous waste, i.e. that is potentially harmful to humans or creatures on exposure to radiation from, or on contact with, such waste.
  • Radioactive waste divides into three categories, depending on the amount of radioactivity it contains - low, intermediate and high-level.
  • Low level wastes are ones that typically need to be handled by personnel wearing protective clothing, but no physical barrier of suitable construction, e.g. concrete, is additionally required to shield operating personnel from radiation.
  • High level waste on the other hand, has a high enough radioactive content that it continues to generate heat, due to radioactive decay, in sufficient quantities that special cooling measures are needed to prevent the temperature of the waste from rising to unacceptably high levels.
  • Intermediate level waste has radioactivity levels between these two extremes. Solid radioactive wastes are in fact categorised in the UK as follows (Radioactive Waste Management Advisory committee 5th Annual Report June 1984) :
  • High Level Waste significantly self heating wastes
  • Low Level Waste (LLW) : less than 4E9 Bq per te alpha and/or less than 12E9 Bq per t beta/gamma
  • intermediate level waste is produced in relatively large quantities and although it is not as difficult to handle as high level waste it requires more careful and specialised handling than low level waste. There is therefore a need for treating intermediate level waste in a manner which is both safe and able to handle a sufficient throughput.
  • intermediate level waste is characterised solely by an approximate range of radioactivity, any waste materials of the requisite radioactivity are classified as intermediate level wastes. Therefore, such wastes, in addition to solid or liquid waste resulting from the reprocessing of nuclear fuel, also include contaminated components and materials.
  • some types of radioactive waste e.g.
  • sludge-like product including magnesium, magnesium hydroxide, uranium, uranium hydride, uranium oxide, dissolved hydrogen and water, while other types of waste remain largely unaffected.
  • the waste product typically varies in moisture content (wet and runny to relatively dry and firm) , particle size distribution (coarse to colloidal) and components (e.g. % sludge, metallic items etc) .
  • moisture content wet and runny to relatively dry and firm
  • particle size distribution coarse to colloidal
  • components e.g. % sludge, metallic items etc
  • the term "sludge” will be understood to include a waste product resembling a clay.
  • a dryer for wet radioactive, toxic or other hazardous waste comprising a container for waste to be dried, a drying chamber in which the container is mounted, a heater located outside the drying chamber for heating a fluid, and means for conveying the heated fluid to the drying chamber for heating the container.
  • the heater is located outside the drying chamber, there is no risk of radioactive waste that may be spilled from the container coming into contact with the heater. Therefore there is no risk of fire caused in this way. Furthermore and because a fluid is used for transferring heat from the heater to the container, no hot spots can arise.
  • the fluid that is heated may be a liquid or a gas.
  • the fluid it is less desirable for the fluid to be a liquid because liquids that can withstand high temperatures (up to about 300°C is required) are generally oils.
  • the heating fluid be a gas, which for convenience is air, since radioactive contamination, e.g. contaminated dust particles, can easily be removed by suitable filters, which are well known in the art.
  • the heated air conveyed to the enclosure prefferably to be exhausted to the atmosphere, with or without mixing with the vapour that is released from the heated contaminated waste and with appropriate filtration prior to release into the atmosphere.
  • the exhausted air would be at relatively high temperature and represents an unnecessary heat loss.
  • mixing of the heated air and vapour is undesirable as it can lead to the spread of radioactive contamination.
  • the heated gas conveying means comprises a closed circuit including a fan operable for circulating the gas from the heater to the drying chamber and back to the heater, and at least one thermocouple for controlling the heat output of the heater.
  • thermocouple(s) and fan are only components of the closed heating system that will need periodic servicing and repair.
  • This repair is in general carried out by remote control, e.g. by a robot, since the dryer will need to be enclosed in a protective cell to protect operating personnel from radiation and radioactive contamination in the environment in which the dryer is located.
  • thermocouple(s) and fan they, along with an associated section of the closed circuit, preferably form a removable unit located to one side of the drying chamber.
  • the design of the enclosure should be such as to permit a container to be loaded with a quantity of radioactive sludge to be dried before the container is loaded into the drying chamber. Therefore, the enclosure may have a cover which is removable for loading the container into and from the drying chamber.
  • the container will also have a lid with an opening in it for the passage of vapourised liquid produced by the wet radioactive waste in the container, and a gas line is provided for conveying the vapour from the container to the exterior of the enclosure.
  • the seal can take the form of a water seal.
  • a lower end of a sealing member on the underside of the enclosure cover may be located around the opening in, and seal against, the container lid.
  • the sealing member can suitably be a sealing collar which is held captive on the cover and is vertically movable for adjusting to slight variations in the vertical position of the top surface of the lid of different containers of the same nominal size.
  • This sealing collar may be made of metal and merely rest, under its own weight, in metal-to-metal sealing contact with the lid of the container. Alternatively, in order to guarantee adequate sealing contact, the sealing collar may be biased against the lid of the container when the enclosure cover is in its closed position.
  • the enclosure be able to accommodate a plurality of containers, so that a number of containers can be dried at the same time using only a single circulating gas heater system.
  • the several containers are carried in a stillage which isitself removably held in the drying chamber. This means that the containers can firstly be positioned in the stillage, after which they are loaded at the same time, in the stillage, into the drying chamber. Conversely, they can be removed at the same time by lifting the stillage out through the top of the enclosure after previously removing its cover. Alternatively the containers can be loaded and unloaded individually without removing the stillage from the dryer.
  • Each container may be supported on a plurality of guide baffles mounted inside the stillage, for inducing spin in the flow of heated gas. This ensures uniform air and heat distribution and improves the heat transfer rate.
  • a manifold within each cover has respective inlet pipes, each connected to the opening in a respective container lid by means of a respective sealing member, and a single outlet pipe releasably connected to the above-mentioned gas line. This simplifies the pipework by avoiding the need for multiple gas lines for exhausting the vapour from the dryer.
  • the vapour typically includes a quantity of flammable gas, principally hydrogen, which could potentially result in an explosion if oxygen is present in sufficient proportion
  • the outlet pipes from the manifolds of the respective dryers lead to a common gas line including suitable separation means for removing radioactive contaminants before the vapour is released from the common gas line into the atmosphere.
  • the separation means conveniently can comprise a scrubber for removing dust and water vapour from the gas followed by high efficiency particulate air filters for removing extremely fine particles (about 1 micron in diameter and less) .
  • the dryers will be mounted within a sealed and ventilated cell for shielding operating personnel from radiation and contamination by the radioactive waste and means are provided for maintaining the interior of the cell at a predetermined pressure below that of its exterior.
  • means are provided for controlling the pressure in the common gas line so as to be at a predetermined pressure differential below the pressure in the cell.
  • the intended function of the cell is to physically isolate the environment surrounding the dryers from the operating personnel. Furthermore, the cell environment will normally be sealed from the radioactive vapours produced by heating the wet radioactive waste. In the most unlikely event that there is any defect which could result in radioactive contamination escaping into the cell interior or into the environment where the operating personnel are working, the cascaded pressure differentials will ensure that gas will flow through the defect in such a direction as to contain the radioactive contamination, thereby avoiding any danger to operating personnel.
  • a method of drying wet radioactive, toxic or other hazardous waste comprising placing the waste inside a container having a lid with an opening therein and circulating heated gas from a heat source to a drying chamber in which said container is mounted and back to the heat source, the heat source being located outside the drying chamber and the circulating gas in the drying chamber coming into contact with the container so as to heat the waste and produce vapourised liquid which passes out through the opening in the lid.
  • Figure 1 is a vertical sectional view through a dryer according to a preferred embodiment of the invention and is taken along the section line I-I of Figure 2;
  • Figures 2 and 3 are horizontal sectional views taken along the lines II-II and III-III, respectively in Figure 1;
  • Figure 4 is a vertical sectional view taken along the line IV-IV in Figure 1;
  • Figure 5 is a side elevational view of a stillage in which four containers of radioactive sludge are positioned, only two of these containers being visible in Figure 5;
  • Figure 6 is a schematic view of a system for handling and treating the offgas produced from a number of dryers located in a common protective cell.
  • a dryer 1 for drying wet, intermediate level, radioactive sludge comprises an enclosure 30 having a bottom wall 31 upright side walls 32 and a removable cover 33 which together define a drying chamber 60.
  • its bottom wall, side walls and cover are all of double-walled construction, comprising spaced apart outer and inner walls, e.g. of stainless steel, with heat insulating material 34 between them.
  • the dryer is designed to carry four containers 35 for intermediate level radioactive sludge, though it will be appreciated that the number of containers 35 for which the enclosure 32 is designed can be less than or greater than four. At the lower extreme, the enclosure can accommodate only a single container.
  • Each container 35 is in the form of a vertically disposed, cylindrical drum which is closed at both ends, its upper end or lid 36 being formed with a central hole 37 through which passes evaporated liquid or "offgas", generated as the radioactive sludge is heated in the dryer.
  • the four containers are removably carried on respective baffle assemblies, each comprising a plurality of guide baffles 41 whose function will be described hereinbelow, inside a stillage or crate 38 which fits snugly within the drying chamber 60, a rim 39 formed around the top peripheral edge of the stillage resting on an annular shoulder 40 formed on the inside of the side walls 34.
  • the stillage has its bottom formed with a high proportion of openings (not specifically referenced) for the passage of hot air through them.
  • a central conduit 42 extends vertically from a lower end 43 positioned just below the bottom of the stillage 38 to an upper end comprising an end plate 44 blanking off the upper end and four inlet apertures 45 equally spaced around the peripheral surface of the central conduit 42 adjacent to the end plate 44.
  • the conduit forms part of a closed loop, heated air, circulation system which is now to be described.
  • the enclosure 30 is extended to one side (i.e. the left side) to form an open-topped housing 46 in which is located a removable unit 47 which comprises a body 48 in which is mounted a conduit 49, comprising conduit sections 49a, 49b, 49c, an air heater unit 50 in the conduit section 49c, a fan unit 51 for maintaining air circulation through conduit 49 and temperature measuring thermocouples 52 which sense the temperature in the conduit section 49b.
  • a removable unit 47 which comprises a body 48 in which is mounted a conduit 49, comprising conduit sections 49a, 49b, 49c, an air heater unit 50 in the conduit section 49c, a fan unit 51 for maintaining air circulation through conduit 49 and temperature measuring thermocouples 52 which sense the temperature in the conduit section 49b.
  • the walls of the housing 46 and the removable unit 47 are of double-skin construction with insulation filling the space between the walls.
  • the electric motor section of the fan unit 51 extends above the upper surface of the removable unit so that all electrical connections to the fan unit are readily accessible from the exterior.
  • the particular means by which the removable unit is located in the housing 46 is not material, though it needs to be designed for easy replacement by a robot or remote control.
  • a plug-in fit can be provided between the removable unit 47 and the housing 46.
  • conduit section 49a air is drawn in to conduit section 49a by fan unit 51 from a conduit section 53 which is located in the bottom section of the enclosure 30 and is approximately U-shaped, having an upwardly angled inlet end 54, into which the lower, outlet end, of the central conduit 42 of the stillage 38 is received, an upwardly angled outlet end 55 which connects with the inlet end of conduit section 49a, and a central section 56 which connects the inlet and outlet angled sections 54, 55.
  • conduit section 49c air circulated by the fan 51 through conduit section 49b and heated by heater unit 50 passes through conduit section 49c into a short angled conduit section 57, whose inlet end is of the same shape and size as the outlet end of conduit section 49c.
  • This short angled conduit section 57 ( Figure 3) then leads into an air delivery chamber 58 which is defined within the bottom section of the enclosure 32, is positioned immediately beneath the drying chamber 60 and is of a similar shape and size, as seen in plan view, as the horizontal cross-sectional shape of both the drying chamber 60 and the stillage 38.
  • the heated air is circulated into the air delivery chamber 58 from the short, angled conduit section 57 and passes upwardly from the air delivery chamber through the openings in the bottom and side walls of the stillage 38, the curved guide baffles 41 serving to induce spin in the air flow to produce shearing and turbulence, which ensures good air- distribution and enhanced heat transfer.
  • the air flow then passes upwardly around the side walls of the containers 35, across the top surface of the container lids, through a small space 59 provided between the underside of the enclosure cover 33 and the top surface of each container lid 36 and then passes through the inlet apertures 45 of the central conduit 42. If desired, it may be appropriate to reverse the air flow direction of the heated air.
  • thermocouples 52 are connected to inputs of a controller (not shown) which controls the heat output of the heater unit 50, so that the temperature of the air in conduit section 49b is maintained at a predetermined value.
  • Heat from the hot air circulated through the drying chamber is conducted through the walls of the containers 35 and serves to heat the radioactive waste in the containers. This causes the liquid, principally water, contained in the waste to evaporate as offgas, containing principally water vapour and hydrogen, and the offgas passes through the hole 37 in the lid of each container under the action of suction applied to the offgas treatment system to be described below with reference to Figure
  • the hydrogen is produced primarily as a consequence of the corrosion of magnesium in water and hydrogen, which is greatly accelerated by the drying temperature.
  • enclosure cover 33 comprises a top wall, an underneath wall and connecting peripheral walls, which together define an internal space in which is mounted a manifold 61 having respective, downwardly angled, inlet pipes 62 which are each aligned at their lower end with the central opening 37 of the corresponding container 35.
  • cover 33 is removably fitted to the enclosure 30 is not material, but should be such that it can readily be released by a robot or by remote control. Suitable guidance and location means (not shown in the drawings) are provided for ensuring the correction location and orientation of the cover. A seal is provided between the cover and enclosure, a water seal 66 being preferred because it requires no maintenance and its integrity can readily be confirmed.
  • a metal sealing collar 63 is fitted around the outside of the lower end of inlet pipe 62 and is vertically slidable on the inlet pipe.
  • the sealing collar rests, under the effect of its own weight, in metal-to-metal sealing contact with, and located surrounding the hole in, the container lid 36. If greater sealing contact is required, then a biasing spring can be used for urging the sealing collar in the downward direction.
  • the upper end of the sealing collar is formed with an annular flange 64 for holding each sealing collar captive on the enclosure lid.
  • dilution air is added to the offgas.
  • One way in which this can be done is to introduce dilution air directly into each container, for example through an air inlet pipe (not shown) surrounding and arranged coaxially with the inlet end of each offgas inlet pipe 162.
  • a short pipe 63 passes through the removable cover 33 and opens into each inlet pipe 62. In this way, the offgas in the inlet pipe 62 passing the lower end of air pipe 63 draws in dilution air from the atmosphere of the environment in which the dryer is located.
  • the site and geometry of the offgas inlet pipe 62 and air pipe 63, together with the design flow rates of offgas and air, are such as to ensure that more than sufficient dilution air is mixed with the off gas to avoid any possible risk of a fire occurring.
  • the concentration of the flammable in gas the air-diluted offgas is kept at or below 25% of the lower flammable level.
  • the manifold 61 has a single outlet pipe 64 which leads to near one corner of the enclosure cover 33 where it is angled downwardly, leading into a vertical section 64a.
  • the lower end of the vertical section 64a is removably connected to the upwardly angled inlet end of an off gas line 65, which is secured to the enclosure and passes through one of its upright side walls 32. Therefore, the air-diluted offgas collected in manifold 61 passes through outlet pipe 64, vertical section 64a and offgas line 65 to the exterior of the dryer enclosure.
  • containers of wet radioactive waste are loaded into an empty stillage 38 and, with the enclosure cover 33 removed from the enclosure, the stillage and its four containers are then inserted into the dryer enclosure, its rim 39 seating on the annular shoulder 40.
  • the sealing collars 63 come into contact with the container lids and the enclosure cover can be finally located on the enclosure with the vertical pipe section 64a reconnected with the offgas line 65. The enclosure cover is then secured in position.
  • the fan and heater units are then switched on and heated air at a controlled temperature is circulated through the drying chamber 60 to heat up the radioactive sludge and drive off, as vapour, the liquid contained in the sludge. Since uranium hydride, which is typically present in radioactive waste, can ignite at temperatures as low as 350°C, the dryer temperature should be restricted to a maximum of about 300°C.
  • the offgas is collected in the manifold 61 and ducted away in the offgas line 65.. The drying process continues for a predetermined period of time (for example about 23 hours) that is found to be sufficient to produce a solid mass of a sufficient dryness. Lastly, the containers are unloaded in the stillage from the dryer ready for another set of drums containing wet radioactive waste for drying.
  • FIG. 6 is a diagrammatic view of a suitable plant.
  • the drying plant in this example comprises eight dryers 1, so that the total drying capacity is for thirty-two containers, though any other suitable number of dryers is possible.
  • the eight dryers are mounted within a single sealed and ventilated cell 70 for shielding operating personnel from radiation and contamination by radioactive waste.
  • the design and construction of such a cell is very well known in the art and will therefore not be further described.
  • this cell provides a sealed environment in which the eight dryers operate.
  • the pressure of this environment is maintained below the atmospheric pressure of the environment surrounding this cell in which operating personnel are working by a predetermined amount (e.g. -200Pa) . Therefore, in the most unlikely event of there being any defect in the cell wall, the pressure differential will cause an air flow from the outer environment where the personnel are working to the inner environment maintained within the cell 70. This avoids any risk of the personnel becoming contaminated.
  • a predetermined amount e.g. -200Pa
  • the respective offgas lines 65 (offgas temperatures up to 140°C) from the eight dryers 1 are combined and connected to a single, common gas line 71 leading to an inlet of a scrubber unit 72.
  • the hot offgas is intimately contacted with cold water sprays that remove radioactive dust down to a size of about 1 micron and also serve to condense water vapour in the offgas.
  • the resulting contaminated water collecting in the bottom of the scrubber is led away by pipework (not shown) to waste water storage tanks 73 for further treatment, while the cleaned offgas leaves overhead.
  • the tanks 73 are vented to a common vent line 74 so that vapours released from these tanks are sent to another inlet of the scrubber unit 72.
  • a compactor which is used for compacting the dry solid waste after it is removed from the drying plant.
  • the manner in which the dried sludge is transferred from the drying plant to the compactor does not form part of the present invention.
  • the compaction process serves to reduce the volume of the dry waste to a minimum by squeezing air voids from within its bulk, releasing quantities of air which are vented from the compactor and introduced into the scrubber unit 72 along vent line 76, so that radioactive dust in this vent air can be removed.
  • the warm, cleaned gas leaving the scrubber unit 72 overhead still contains a small quantity of tiny radioactive particles, typically of a size of one micron and less.
  • the cleaned gas is passed through a two-stage high efficiency filtration system comprising two high efficiency particulate air (HEPA) filters 77 and the clean air leaving these filters is drawn by the inlet suction of an exhaust fan 78, which maintains the space above the waste in each drum and the entire offgas treating system under reduced pressure, and exhausted through a stack into the atmosphere.
  • HEPA high efficiency particulate air
  • a monitoring device 79 monitors the relative humidity of the clean gas passing to the two-stage filtration unit and activates a heated air source 80 if the monitored relative humidity rises above a predetermined level. In this way, a flow of dry air is introduced into the gas flowing from the scrubber unit 72 to the two-stage filtration unit so as to maintain its relative humidity at an acceptably low level for the HEPA filters.
  • a differential pressure controller 81 monitors the pressure differential between the pressure of the environment maintained within the cell 70 and the (lower) pressure of the offgas in the common gas line 71. Depending on the monitored pressure differential, the pressure controller controls the opening of a damper 82, which adjusts the gas flow into the exhaust fan 78 so as to maintain the pressure in common gas line 71 at a predetermined amount below that of the cell environment.
  • the dryer plant is designed such that any one dryer 1 can be opened at any one time in order to enable the dried waste to be removed and further wet-sludge containing containers to be loaded into that dryer.
  • the enclosure cover of the dryer is removed, the pressure differential maintained between the space in the containers above the sludge and the cell environment, which pressure differential is monitored for each dryer by pressure measuring device 84, is lost and the air flow through the respective offgas line 65 increases.
  • the increased air flow is restricted by a respective restriction orifice 83 in the associated offgas line 65 and the design of the pipework from the offgas lines 65 to the exhaust fan 78 as well as the inlet suction of exhaust fan 78 are such that adequate offgas flows are maintained through the remaining seven offgas lines 65 and sufficient dilution air is drawn in to the dryers from the atmosphere maintained within cell 70.
  • the design allows any one dryer to be opened at any one time without affecting the continued reliable and safe evacuation of offgas from the remaining seven dryers and, very importantly, without using any flow control valves or other serviceable parts for isolating the one dryer which is open.
  • the differential pressure controller 81 sampling the pressure differential between the interior of cell 70 and the offgas in gas line 71, adjusts the setting of damper 82 to maintain the required pressure differential.
  • the geometry and pipe runs of the offgas lines 65 are made the same, to the extent that is practicable, and by preadjustment of the restriction orifices 83 in the offgas lines 65, the flow rates along the offgas lines 65 can be balanced.
  • each pressure measuring device 84 includes an alarm unit which generates an audible and/or visible alarm when the pressure measuring device detects an intermediate differential pressure value, indicating that the corresponding dryer cover is not fully in place.
  • the pressure measuring device 84 generates output signals indicating which of the three possible statuses each dryer cover has. These outputs signals are received by a control circuit (not shown) which is arranged to shut off the heater and fan unit of the corresponding dryers if two or more dryer covers have been removed.
  • the dryer concerned is isolated by removing the dryer cover and inserting a plug (not shown) into the open upper end of the offgas line 65. Then, while maintenance is being carried out on that one dryer, another dryer can be opened without a malfunction condition being detected and the respective fan and heating units being switched off.
  • the described individual dryer and the dryer plant both exhibit many advantages.
  • there is no risk of hot spots or fire resulting from spilled radioactive sludge from the drums coming into contact with any heating elements since the heater unit is mounted to one side of the dryer and circulating air serves to transfer heat from the heater unit to the drying chamber.
  • the sealing collars provide a simple and effective means for isolating the circulating hot air from the offgas produced from the waste-containing drums.
  • the side location for the removable unit, including the fan and heater unit facilitates repair and maintenance.
  • the dryer plant is intrinsically failsafe, because of the cascading of pressure differentials maintained between the operating environment for the operating personnel and the cell interior and between the cell interior and the drying chambers of the dryers.
  • the described offgas pipework and filtration system continues to operate safely and satisfactorily without the use of any moving or serviceable parts (apart from the exhaust fan) , such as isolating control valves, even when one of the dryers is open. Additional safety measures are provided by generating an alarm whenever the monitored dryer differential pressure relative to that of the cell environment indicates that one of the enclosure covers is not fitting properly. If any attempt is made to open two or more covers, then the corresponding fan and heater units are shut off.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Drying Of Solid Materials (AREA)

Abstract

Pour le séchage de déchets radioactifs ou toxiques humides ou d'autres déchets humides dangereux, en particulier les déchets radioactifs de niveau intermédiaire, on expose les déchets contenus dans un ou plusieurs fûts (35) à un fluide chauffé, de préférence de l'air, que l'on fait circuler dans la chambre de séchage (60) où sont placés les fûts (35). L'air est chauffé par un élément chauffant (50) situé en dehors de la chambre de séchage (60), plutôt que d'un côté de cette dernière. Le liquide libéré sous forme de vapeur (effluent gazeux) lors du chauffage de la boue radioactive dans les fûts (35) est recueilli dans un collecteur (61), dilué avec de l'air pour éviter tout risque d'explosion et traité par filtrage avant son dégagement dans l'atmosphère. Des précautions appropriées sont prises pour éviter tout risque d'une exposition du personnel à des radiations ou à une contamination radioactive.
PCT/EP1995/001123 1994-03-25 1995-03-24 Sechage de dechets radioactifs ou toxiques humides ou d'autres dechets humides dangereux Ceased WO1995026556A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9405924A GB9405924D0 (en) 1994-03-25 1994-03-25 Drying wet radioactive, toxic or other hazardous waste
GB9405924.3 1994-03-25

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WO1995026556A1 true WO1995026556A1 (fr) 1995-10-05

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2223227C2 (ru) * 2001-08-10 2004-02-10 Уральский электрохимический комбинат Установка для испарения гексафторида урана
RU2310609C1 (ru) * 2006-03-06 2007-11-20 Федеральное государственное унитарное предприятие УРАЛЬСКИЙ ЭЛЕКТРОХИМИЧЕСКИЙ КОМБИНАТ Установка для испарения гексафторида урана
US8065815B2 (en) * 2006-10-10 2011-11-29 Rdp Technologies, Inc. Apparatus, method and system for treating sewage sludge
GB2510798A (en) * 2012-10-19 2014-08-20 Nsg Environmental Ltd Process for drying radioactive waste containing water
CN114008723A (zh) * 2019-05-23 2022-02-01 西屋电气有限责任公司 屏蔽容器中产生的化学计量氢气和氧气的被动排气装置

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RU2223227C2 (ru) * 2001-08-10 2004-02-10 Уральский электрохимический комбинат Установка для испарения гексафторида урана
RU2310609C1 (ru) * 2006-03-06 2007-11-20 Федеральное государственное унитарное предприятие УРАЛЬСКИЙ ЭЛЕКТРОХИМИЧЕСКИЙ КОМБИНАТ Установка для испарения гексафторида урана
US8065815B2 (en) * 2006-10-10 2011-11-29 Rdp Technologies, Inc. Apparatus, method and system for treating sewage sludge
GB2510798A (en) * 2012-10-19 2014-08-20 Nsg Environmental Ltd Process for drying radioactive waste containing water
GB2510798B (en) * 2012-10-19 2016-10-26 Nsg Env Ltd Process for drying radioactive waste containing water
CN114008723A (zh) * 2019-05-23 2022-02-01 西屋电气有限责任公司 屏蔽容器中产生的化学计量氢气和氧气的被动排气装置

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