Management of Radioactive Waste from NPP Prof. Dr. A.M. El- Kamash Hot Lab.& Waste Management Center AEAE firstname.lastname@example.org
Content • Introduction • Power reactor wastes • Fuel cycle wastes • Treatment of Radioactive waste, and • Waste management practice in Egypt
Introduction • At the end of the 20th century, nuclear energy supplied about 16% of the world electricity needs • The growth of the nuclear industry in different countries has been the natural consequence of an increasing need for electrical power.
Introduction • The future prospects of nuclear power are related to the following issues: • Public confidence, or at least tolerance, particularly on an accepted solution to the disposal of high level waste. • The competitiveness in terms of capital costs and construction periods. • Identification of appropriate linkages between nuclear power and environmental issues, such as global climate change, local air quality and regional rain acidification. • Lastly, the need for a global approach to some activities of nuclear power, such as nuclear waste management. These issues are related to the country’s energy policy and international co-operation and therefore belong to the governmental domain of competence.
Introduction Radioactive waste generated from NPP can be divided into • power reactor wastes, and • fuel cycle facility wastes, • Power reactors are responsible for the largest volume of LLW. • Fuel cycle plants, such as fuel enrichment plants and fuel fabrication plants, produce small volumes of LLW relative to power reactors.
Power Reactor Wastes • Component of NPP • Nuclear Power plant.exe
Power Reactor Wastes The majority of power reactor wastes are classified as: • Liquid radioactive wastes, • Wet solids (including slurries), • Dry active solid wastes (DAW), • Liquid organic wastes, and • Thermal waste.
Power Reactor Wastes 1) Liquid Radioactive Wastes • Liquid radioactive wastes are produced from recycled reactor core fluids, hydraulic fluid from equipment repairs, housekeeping activities, and laundering. • These wastes are treated to remove the maximum amount of radioactive contamination. • Treated liquids are then typically recycled or discharged to the environment under the control of the plant operating license and national regulations.
Power Reactor Wastes 2) Wet solids Radioactive wet solid wastes consist of solid wastes containing greater than 5% liquid. Most radioactive wet solid wastes are produced from cleaning aqueous processing systems at power reactors. • Spent Ion-Exchange Resins • Filter Sludge • Cartridge Filters
3) Dry active solid wastes Anticontaminant clothing Cloth (rags, mops, gloves) Contaminated dirt Contaminated tools and equipment, Filters Glass High density concrete block Miscellaneous metal, Aerosol cans, Buckets, Crushed drums, Fittings, Pipes and Valves Miscellaneous wood Plastic Bags, gloves, shoe covers, Sample bottles Rubber, Sweeping Compounds Irradiated metal alloys Flux wires, Flow channels, Fuel channels, In-core instrumentation, Poison channels, Shim rods. Power Reactor Wastes
4) Liquid organic wastes liquid organic wastes includes pump oil, lubricating oils, organic resins, liquid scintillation counting solutions, and decontamination solutions containing organic chelating agents. Liquid organic waste volumes are very small when compared to the total generated volume of LLW Power Reactor Wastes
Power Reactor Wastes 5) Thermal waste • This waste is common both to conventional and nuclear plants. • The quantity of thermal waste proportional to the size of the plant. • In a NPP with a PWR operates at a thermal power of 1000 MW must dispose of approximately 2.4 million Btu/s. If this quantity of heat were released into a river having a flow rate of 1000 cubic ft/s, the entire river temperature would rise by 33 degrees Fahrenheit.
Fuel Cycle Wastes Fuel cycle facility wastes include • Calcium fluoride generated from hydrogen fluoride gas scrubbers, • Filter sludge, • Contaminated equipment, and • Trash.
Objective of RWM • To collect, handle, treat, condition, store, transport, and dispose RW in a manner that protects the human and the environment without imposing undue burden on future generation.
Principles of RWM • Establishing a national legal framework, • Control of radioactive waste generation, • Safety of facilities, • Waste generator pays, • Sound decision-making based on scientific information, • Risk analysis and optimization of resources, • International cooperation
Requirements of National RWM System • Organizational structure • Safety requirements and conditions • International recommendations, standards and agreements • National legislation • Cost and funding • Technical capability of personnel • Public involvement and political acceptance • Other non-technical factors • Geographic conditions • Opportunity for international co-operation • Physical infrastructure
Generation Conditioning Transportation Characterization Treatment Pre-treatment WAC Discharge S.A. Disposal Activitiesin RWM System
Treatment Technology Treatment technologies of LLW and MLLW range from the very simple to extremely complex. These technologies could be divided into eleven broad categories as follows: Sizing Compaction Filtration Decontamination Evaporation Separation Incineration Vitrification Metal Recovery Immobilization/Stabilization Physical/Chemical Treatments.
Treatment of RW • Treatment of aqueous wastes. • Treatment of solid wastes.
Characterization of Liquid Waste • Liquid wastes are generally characterized by their chemical, physical, radiological and their biological properties. • Chemical properties: toxicity, chemical composition of the liquid, pH value, oxygen demand, and Zeta potential. • Physical properties: turbidity, density, viscosity, surface tension., conductivity, emulsifying ability • The radiological: affect the choice of the treatment process and and the radiological impact to operators and the surrounding environment.
Selection of Treatment System Selection of a liquid waste treatment system involves a set of decisions related to the following factors. • Characterization of arising waste, • Discharge requirements for decontaminated liquors, • Available technologies and their costs, • Conditioning of the concentrates, and • Storage and disposal of conditioned concentrates
Treatment Processes Selection of a process for liquid wastes treatment depends on the radiological and physico-chemical properties and the quantity of arising waste. The processes commonly used for treatment of liquid radioactive wastes fall generally into three main categories: • Chemical precipitation, • Ion exchange, and • Evaporation.
Ion Exchange Ion exchangers are insoluble solid materials which carry exchangeable ions. These ions can be exchanged by a stoichiometrically equivalent amount of other ions of the same sign when the ion exchanger is in contact with an electrolyte solution. Ion exchangers are generally classified according to their exchange function: • Cation Exchangers, • Anion Exchangers • Amphoteric Ion Exchangers
Advantagesof Ion Exchange • Treatment procedures are based on well proven, conventional process and equipment, • Suitable for ionic impurities, • High quality effluents are possible, • Adequate for separation of several radionuclides • High decontamination factor achievable giving low volumes of solid waste which can be readily conditioned for disposal, • Suitable for separation of colloids, and • Suitable for continuous and automatic operation.
Disadvantages of Ion Exchange • Salt content and suspended solids must be low, • Non electrolytes are not exchanged, colloids, and contaminants can cause difficulties, • Some exchangers are pH-sensitive, • Regeneration give rise to secondary wastes, • Some exchangers have low radiation tolerance, especially organic materials • Some exchangers (e.g. organic) are expensive, • Some exchangers have limited stability to heat
Evaporation • Types of Evaporators • Dot kettle. natural forced circulation, vaiour cothpression and wiped-filin evaporators. • Evaporators which can operate in the presence of solids appear to be the most suitable for the treatment of bearing waste streams, since actinide hydrolysis products are mainly associated with suspended particulates and colloidal materials in feeds that are weakly acidic or neutral.
Advantages of Evaporation • Large volume reduction for a range of effluents, • Good decontamination from non-volatile radionuclides, • Complete removal of all active and inactive salts from waste effluent allowing reuse of condensates and avoiding the problems caused by the build-up of inactive salts. • Unaffected by the presence of complex agents in waste effluents, unlike many of the alternative treatment processes
Limitations of Evaporation • Unsuitable for waste effluents containing large salt concentrations, • Expensive compared to other treatment processes due to the high energy needs. • The problems caused by corrosion, scaling and foam formation may prevent the successful application, The presence of some organics can result in explosions on evaporation and appropriate pretreatment is required, such as steam stripping.
Discharge Requirements for Decontaminated Liquors • Restrictions or limits on release of the decontaminated liquors should be carefully considered.Determination of these limits is done differently in various countries but does in all cases, require extensive analyses by both the waste producer and regulating authority to arrive at an agreement that the releases are acceptable.
Conditioning of Sludge, Concentrates and Ion Exchangers • Two methods have been used: cementation and bitumization. • For each matrix material, several techniques could be used in view of how the wastes are mixed with the matrix material. • Normally, immobilization is carried out in fixed installations at the site of waste generation, but also mobile systems have been developed for some applications
The management strategy for solid waste of small nuclear research centers in developing countries.
TreatmentTechnology Compaction A well proven volume reduction technology used to reduce the total volume of waste. This is accomplished by applying high pressures to the waste, which reduces void space. Compactor systems consist of a press, using horizontal or vertical rams to apply pressure to the waste in a drum or box-type container. Volume reduction achieved during compaction is a function of • Void space in the waste, • The force applied by the press, and • The bulk density of the material.
TreatmentTechnology Compaction Advantages of compaction include • Compaction is a proven process used throughout the world in the nuclear industry, • Compaction systems are simple, and tend to be reliable and trouble free, • Waste compaction is relatively inexpensive, and • The process is simple to operate.
TreatmentTechnology Compaction Disadvantages of compaction include • Most commercial compactor systems are not available with adequate exhaust equipment and must be modified, • Compactors cannot reduce the hazard of the incoming waste, and are therefore not appropriate for treating waste streams with hazardous constituents, • Compaction is not recommended for wastes containing free liquids, or with wastes containing explosives, and • Compaction should not be used on dense or bulky items where minimum volume reduction would be achieved.
Benefits of Solidification ► Prevent dispersion of fines and liquids during handling ► Minimize releases of radionuclides and hazardous constituents after disposal ► Reduce potential exposure to intruders, long term solution
Desirable properties of a solidification agent ► Availability ► Low cost ► Volumetric efficiency ► Simplicity of use ► Good waste form properties
Important properties of solidified waste forms ► Low leachability ► High chemical stability ► High compressive strength ► High radiation resistance ► High resistance to biodegradation ► High thermal stability ► Low solubility
Solidification agents currently in use ► Cement, with and without additives ► Blended Cements (Fly ash, slags, etc.) ► Bitumen ► Glass or ceramics ►Polymers
Conditioning of compatible radioactive solid wastes by in-drum compaction
Advantages and disadvantages of cement Advantages Disadvantages ● Technology and materials are well known and available ● Some wastes affect setting ● Compatible with many wastes ● Swelling and cracking may occur ● Volume increase and high density for shipping and disposal ● Low cost ● Good impact and compressive strength