Treatment Centers for Radioactive Waste

Transcription

1 Treatment Centers for Radioactive Waste

2 TREATMENT CENTERS FOR RADIOACTIVE WASTE Introduction Nuclear facilities such as nuclear power plants, reprocessing plants, nuclear fuel cycle production units, laboratories and research institutes produce radioactive wastes during the course of normal operation. Waste is also generated when parts of plant are dismantled or scrapped or during complete plant decommissioning. Many of these nuclear facilities, especially the older types of nuclear reactors, have been designed without any waste treatment facilities. The liquid and solid radioactive waste have therefore been collected and stored, mainly in storage facilities of a very basic design. After several years of operation, these basic storage facilities become full and the waste becomes a safety problem for the operating staff of the NPP s. It can also pose a risk to the environment and in some cases, to the local population. In some facilities, the storage facilities are often in a poor condition and a short term solution is required to convert the waste into an environmentally safe condition that is compliant with the local and national requirements for conditioned waste, for acceptance into long term storage, or final disposal. NUKEM has developed a number of processes for waste treatment. According to the local requirements, the Waste Treatment Center (Fig. 1) may include some or all of the following waste treatment facilities and equipment: Sorting Facility Transport System Incineration Facility Evaporation Plant Cementation Facility Ash melting Facility High Force Compaction Nuclide Separation Plant Off-gas Monitoring System Waste Drum Measuring Complete treatment processes are available for the types of radioactive wastes listed; these include volume reduction and conditioning to meet the requirements for long term storage or for final disposal: Solid waste such as - Scrap metal, concrete, ash, - Textiles, paper, wood, filters, etc. Liquid waste such as - Organic solvents, aqueous solutions - Filter sludge, Ion exchange resins, etc. 1

3 Fig. 1 3-D model of Ignalina Waste Treatment Center 2

4 The Radioactive Waste Treatment Concept To treat complex radioactive waste streams efficiently, a comprehensive range of safe and economical waste treatment concepts have been fully developed and further processes are being developed. These waste treatment concepts form the basis for the design and layout of NUKEM s complete Waste Treatment Centers (WTC s). Depending on the client s exact requirements, the concepts provide an integrated system for the treatment of radioactive waste to provide safe and environmentally acceptable solutions. Principal stages include: sorting volume reduction stabilization concentration and conditioning NUKEM s complete WTC s are designed for the complete treatment of all types of radioactive waste encountered. Within the Waste Treatment Centers, the first stage of treatment is sorting different types of solid and liquid radioactive waste. The next stage is to reduce the volume of the wastes using the specialist facilities within the WTC. A key function of the WTC s is to condition and package the radioactive waste so it will meet the acceptance criteria for the long term storage or final disposal. Performance of Typical Waste Treatment Projects NUKEM is a world leader in the field of radioactive waste treatment and offers its clients a complete service for the design, engineering, fabrication and installation of waste treatment systems. The NUKEM service ranges from providing process equipment for a single, specialized application to the turnkey delivery and operation of multitechnology waste treatment centers. NUKEM s international competence in this field was acknowledged by the award of turnkey contracts for several radioactive waste treatment facilities in Eastern Europe and Russia, based on its experience and ability to provide complete and integrated waste treatment systems (please see the enclosed reference list). NUKEM is responsible for the design, engineering and construction of the waste treatment centers in addition to the procurement, delivery and start up of the individual waste treatment facilities. Following contract award, NUKEM prepares the basic and detail engineering design that is then agreed upon with the client. For the implementation phase, it is normal NUKEM practice to procure all hardware components, equipment and manufacturing services according to its Quality Assurance Manual. If possible or required, a high ratio of local subcontractor s supplies will be utilized. Then, after the necessary approvals have been given, the specifications for procurement of the required equipment and waste treatment facilities are prepared and issued. 3

5 As soon as the civil construction has been completed, the installation of the facilities and the special equipment begins. NUKEM specialists supervise the installation of equipment. After the installation has been completed, commissioning and start up of the facilities is carried out under supervision of NUKEM staff. At this stage, it is often a requirement to provide comprehensive training of the clients staff to enable them to safely operate and maintain the plant. The typical duration of such projects is in the range of 3 to 5 years, depending on the scope of service and the individual circumstances i.e. the financial situation of the customer, the approval procedure, etc. Waste Treatment Technologies It is important to recognize that only those processes and facilities that have been proven by extensive testing and successful operation will be considered for inclusion in the design of a new WTC. The technology will either have been used for several years in one of the many NUKEM-supplied plants (for example, at research facilities or nuclear power plants) or the technology will have been licensed to NUKEM (see Fig. 1: Radioactive Waste Streams in a Radioactive Waste Treatment Center). Sorting of Mixed Solid Radioactive Waste If possible, solid low-level radioactive waste will be pre-sorted at the place of origin and transported in a container to the Waste Treatment Center (WTC) sorting room for control sorting. Here, the waste is placed on the sorting table, unwrapped and transferred into the sorting box (see Fig. 2 and 3: Front and Back View of a Sorting Box). The waste is then sorted according to the following criteria: compactibility decontaminability combustibility The activity of the radioactive waste is measured by a dose rate check. In the case of higher level radioactive waste, remote handling techniques are used for sorting whereas low level waste can normally be handled directly. All sorting and cutting work is performed either in hot cells or in protective suits, depending on the activity level of the radioactive waste. The compactible waste is filled into litre drums that are docked to the sorting box. In order to obtain best utilization of the drum volume, pre-compacting takes place by means of an in-drum compactor integrated into the sorting box. The filled drums are closed with a lid and transported to the compaction facility. Decontaminable waste is collected in a transport container lined with foil, that also is docked to the sorting box. It is then transported for to a separate facility for decontamination. In the sorting box, combustible waste is loaded into plastic bags, sealed and transported to the incineration plant. 4

6 Fig. 1 Radioactive Waste Streams in a Radioactive Waste Treatment Center 5

7 Fig. 2 Front View of a Sorting Box 6

8 Fig. 3 Back View Picture of a Sorting Box Compaction An important part of the compaction facility is the High Force Compactor (see Fig. 4: High Force Compactor). The compactor is installed in the compaction room as a stationary unit. The compactor includes drum charge and pellet discharge systems together with the crane, the special pellet grip and drum grip; these are used to facilitate drum charging and pellet discharging. The bulk of waste produced in nuclear facilities is dry, low level and is either compactable or non-compactable. Compaction technology is therefore a suitable technology to reduce the waste volume of the former. Adequate treatment of pre-sorted combustible waste, by incineration, brings additional benefits in terms of safety and economy in subsequent storage or disposal. For detailed information about NUKEM s compaction system, please see also the NUKEM s Broschure: Compaction of Radioactive Waste Decontamination The waste to be decontaminated e.g. contaminated tools, process equipment and drums are transferred to the decontamination facility that is equipped with special decontamination devices such as: Containment cubicle fitted with additional ventilation system Ultrasonic cleaning unit 7

9 High pressure water decontamination unit Mechanical hoist Used decontamination solutions can be either transferred to the waste water collection system for treatment by the liquid effluent treatment plant or can be solidified by cementation with resins or evaporator concentrates. Incineration Incineration is the only proven method that provides the highest possible volume reduction factor for combustible radioactive waste from nuclear power plants, research centers and other nuclear facilities. The design of NUKEM s incinerator is based on that developed at the Research Center Karlsruhe, Germany. The basic design of the NUKEM incinerator can be readily adapted to meet the Client s exact requirements. In addition to that, NUKEM offers the service for design, delivery, erection and commissioning of the following systems that complete the incineration facility itself (see Fig. 5: Incinerator and Afterburner Chamber before Installation into the Building): α-tight system off-gas system Monitoring of emission For detailed information about NUKEM s Incineration Facility, please see also the NUKEM s Broschure: Incineration of Radioactive Waste. 8

10 Fig. 4 High Force Compactor 9

11 Fig. 5 Incinerator and Afterburner Chamber Melting of Incineration Residues Melting is available for the further treatment of radioactive residues from an incineration facility. NUKEM s melting furnace is a chamber type and is equipped with a brick-lined melting crucible that can be swiveled to assist with pouring the melt. Two top-mounted fuel/air plasma burners provide heat for the melting operation. After one hour s operation, the crucible containing the melted mass is swiveled to allow the melt to flow into a special container that is fitted to the bottom outlet of the furnace. The major advantage of the NUKEM melting process is the very low leach rate of the glass-like monolith product when compared with the products obtained with other conditioning processes (See Fig. 6: Melted Product Suitable for Final Storage). For detailed information about NUKEM s melting facility, please see also the NUKEM s booklet: Melting of Ashes and other Incineration Residues. 10

12 Treatment of Radioactive Liquids, Resins and Concentrates Aqueous radioactive wastes generated in nuclear facilities usually contain only a low concentration of soluble and/or insoluble solids. It is standard practice to concentrate the liquid waste of this type by means of an evaporator. This may use either one or two stage evaporation. Evaporation typically achieves a volume reduction of 100 so that the small volume of concentrates remaining can be stored in special storage tanks while awaiting the next conditioning campaign. The distillate from the process can be discharged into the conventional sewage system, assuming that the equipment guarantees a sufficient decontamination factor. Regarding volume reduction of the evaporator concentrates, NUKEM has developed 3 enhanced concentration process technologies named: ROBE RDA UGU The selection of the process technology, each having particular advantages, depends on the waste characteristics of the evaporator concentrates and on specific local requirements of the NPP (see Fig. 7: One Way Evaporator UGU). For detailed information about NUKEM s concentration facility, please see also the NUKEM s Broschure: Concentration of Evaporator Concentrates. 11

13 Fig. 6 Melted Product Suitable for Final Storage 12

14 Fig. 7 One Way Evaporator 13

15 Cementation In order to achieve a volume reduction of the evaporator concentrates it is necessary to concentrate them to a salt content of g/l. For this purpose, a one-way evaporator UGU is used. Concentrates and de-watered resins resulting from the treatment of the liquid radioactive wastes are solidified with cement for interim storage or final disposal. The waste/cement mixture is either filled into drums or used for filling up gaps and voids in containers filled with solid waste. Cementation is one of the methods commonly used for conditioning radioactive wastes since it provides an economical method for the encapsulation of various kinds of radioactive waste to produce a safe, solid waste form, suitable long term storage. To take account of different clients requirements, local requirements for intermediate or final storage, and methods of the loading of the cemented product, a number of cementation processes have been developed by NUKEM. The main types of facilities are: In drum cementation Cementation within a slant mixer High Shear Mixer (for example see Fig. 8: Cementation Facility - Slant Mixer): For detailed information about NUKEM s cementation facilities, please see also the NUKEM s booklet: Cementation of Radioactive Waste Monitoring of Final Waste Products NUKEM has developed a waste drum measuring system for the radiological characterization of the final waste products prior to final disposal. The measuring system includes the following features: Turntable for cylindrical drums Integrated weighing device system Elevator for detector Skid-mounted to allow easy transport of the system Detector and detector shielding Electronics, power supply units and software The waste drum measuring system can be used for measuring surface contamination of the drums in addition to measuring of the contact dose rate and the dose rate at the distance of 1 m. Additionally, the measuring system can be used to identify specific nuclides by gamma spectrometry. In most situations, a measuring the characteristics of each waste drum will be required to meet the regulatory requirements before transportation to an long term store or final disposal (see Fig. 9: Drum Radwaste Meter GME). For detailed information about NUKEM s monitoring systems see also NUKEM s booklet: Monitoring Systems and Services 14

16 Fig. 8 Cementation Facility Slant Mixer 15

17 Fig. 9 Drum Radwaste Meter (GME) 16

18 References Scope of supply Client Putting in operation in 1 Design and delivery of the Ignalina NPP Waste Treatment Center and delivery of the following equipment: Lot 1: - Retrieval facilities for the waste currently stored in storage silos Lot 2: - Sorting facility - Incinerator (100 kg/h) - Off-gas treatment technology - Transport system - High Force Compactor - Cementation facility - Container measurement system - Interim storage facilities for and LL waste Ignalina NPP, Lithuania anticipated Design of the Chernobyl NPP Waste Treatment Center and delivery of the following equipment: Lot 1: Retrieval facilities for the waste currently stored in Storage Silos Lot 2: Plant for Sorting/ Segregating and Processing of the waste: - Sorting facility - Incinerator (50 kg/h) - Off-gas treatment technology - Transport system - High Force Compactor - Cementation facility - Drum/Container measurement system Chernobyl NPP, Ukraine anticipated Lot 3: Near surface disposal facility 17

19 Scope of supply Client Putting in operation in 3 Design of the Kola NPP Liquid Waste Treatment Center and delivery of the following equipment: - Retrieval system for sludge, IER, NxBO 3 - Concentration system for evaporator concentrate - Radionuclide removal system - Cementation system for liquid waste - Drum measurement system Kola NPP, Russia 4 Design of the Balakovo NPP Waste Treatment Center and delivery of the following equipment: - Sorting facility - Incinerator (50 kg/h) - Off-gas treatment technology - Transport system - High Force Compactor - Cementation facility - Evaporation facility - Drum measurement system 5 Design of the Bohunice NPP Waste Treatment Center and delivery of the following equipment: - Sorting facility - Incinerator (50 kg/h) - Off-gas monitoring system - Transport system - High Force Compactor - Evaporation facility - Cementation facility - Drum measurement system Sarubeshatomenergostroi/ Atomenergoexport Balakovo NPP, Russia SE a.s./bohunice NPP, Slovakia

20 Scope of supply Client Putting in operation in 6 Design of the South Ukraine NPP Waste Treatment Center and delivery of the following equipment: - Sorting facility - Incinerator (50 kg/h) - Off-gas monitoring System - High Force Compactor - Transport system - Drum measurement system South Ukraine NPP, Ukraine Design of the Chmelnitzki NPP Waste Treatment Center and delivery of the following equipment: - Sorting facility - Incinerator (50 kg/h) - Off-gas monitoring system - Transport system - High Force Compactor - Evaporation facility - Cementation facility - Drum measurement system Chmelnitzki NPP, Ukraine

21 Industriestr Alzenau Germany T +49 (0) F +49 (0) E [email protected]

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