Presentation on theme: "Radioactive Waste Arising, Waste Classification, and Safety Requirements for Waste Disposal Day 9 – Lecture 6."— Presentation transcript:
1 Radioactive Waste Arising, Waste Classification, and Safety Requirements for Waste Disposal Day 9 – Lecture 6
2 ObjectivesTo provide an overview of radioactive waste arising and classification, waste characteristics and management options.To introduce the IAEA waste classification system.To discuss about the requirements for the protection of public and environment and assurance of safety for the waste disposal facilities during the operational and post-closure periodTo give examples of final disposal choicesThe purpose of this lecture is to provide an overview of radioactive waste arising and classification, waste characteristics and management options. It also includes an introduction to the IAEA waste classification system. It also gives requirements for the protection of public and environment and assurance of safety for the waste disposal facilities during the operational and post-closure period IAEA publication SSR-5 (2009)
3 Contents Sources of Radioactive Waste Waste Properties. Waste Management ApproachesWaste classificationIAEA Waste Classification SystemWaste Disposal OptionsRequirements for protection of public and environment and safety of waste disposal facilitiesThe purpose of this lecture is to provide an overview of radioactive waste arisings and classification, waste characteristics and management options. It also includes an introduction to the IAEA waste classification system. It also gives requirements for the protection of public and environment and assurance of safety for the waste disposal facilities during the operational and post-closure period IAEA publication SSR-5 (2009)
4 IntroductionRadioactive waste arises from many different activities, for example:Operation and decommissioning of nuclear facilities (e.g. nuclear power plants);Application of radionuclides in industry, medicine, and research;Cleanup of contaminated sites; andProcessing of raw materials containing naturally occurring radionuclides.Radioactive waste is associated with a variety of different industries. There are different risks depending on the nature of the wastes.Waste containing or contaminated with radionuclides arises from a number of activities involving the use of radioactive materials, such as the operation and decommissioning of nuclear facilities and the application of radionuclides in industry, medicine and research. Radioactive waste is also generated in the cleanup of sites affected by radioactive residues from various operations or from accidents, and can arise in the processing of raw materials containing naturally occurring radionuclides. The nature of this waste is likely to be such that its safe management must take into account radiation safety considerations. In addition to the waste that must be managed and eventually disposed of, some of the materials arising during the aforementioned activities are of value and may be reused or recycled.
5 Sources of Radioactive Waste (1) Nuclear fuel cycle - Power generationOperational wasteIon exchange resins, evaporation and filtering residuesMetal scrap, thermal insulation material, protective clothingVery low to medium level concentrations of RNSpent nuclear fuelLarge inventory, large number of radionuclidesDecommissioning wasteLarge amountsVery low to high concentrations - mainly activation productsRadioactive waste from the nuclear fuel cycle includes a diverse mix of liquid, gaseous, and solid wastes with a wide range of radioactivity levels.This waste includes, of course, the highly-radioactive spent nuclear fuel containing a wide range of radionuclides, among them uranium, plutonium and their decay products as well as a very broad range of fission products. This spent fuel in some countries is considered waste in itself; in other countries it is reprocessed to separate the economically useful U and Pu from the waste fission products. In either case the high-level waste is highly dangerous and requires sophisticated remote handling techniques, and disposal methods must take into account the significant heat generated and the need for shielding at all times.Operational waste includes a variety of lower-level wastes, either in the form of filtering residues (e.g. ion exchange resins) or as contaminated supplies (e.g. clothing) containing fission and activation products.Decommissioning of nuclear power stations gives rise to large volumes of contaminated material, including some highly-activated reactor components as well as structural materials that may be only slightly contaminated by activation products and/or fission products.
6 Sources of Radioactive Waste (2) Nuclear fuel cycle - VariousMining and milling and U ore extractionLarge quantitiesEnhanced levels naturally occurring radionuclidesRadium-226, radon-222Chemical refiningsmall amounts of wasteEnrichmentdepleted uranium a waste?Reprocessing of spent fuel.Other parts of the nuclear fuel cycle also produce wastes.These include very large volumes of milling wastes containing the decay products of natural uranium, such as radium and radon and radon daughters, often significantly concentrated compared to the original ore. These pose particular problems because of the very long lifetimes of some of the members of the radioactive decay chains, combined with high radioactivity of some of their daughter products.Facilities in the fuel cycle where the ore is refined, enriched and processed into fuel also result in radioactive waste, containing mostly uranium, but because of the economic value of the uranium, the volumes released as waste are usually relatively low. One exception to this would be in the case of depleted uranium tails from enrichment, which in some cases may be considered waste. This material will pose similar problems to naturally-occurring uranium, including not only the direct toxicity of the uranium but also the buildup on long time scales of daughter products (radium and radon).As mentioned in the previous slide, the HLW resulting from reprocessing of spent nuclear fuel in countries where that is part of the fuel cycle poses particular hazards.
7 Sources of Radioactive Waste (3) Industrial applicationsProduction of radioactive sourcesUse of radioactive sourcesSealed sourcesThickness, level and density gaugesIndustrial radiography, sterilization facilitiesLarge number of potentially hazardous sourcesUnsealed sourcesTracers, monitoringMostly short-lived radionuclidesCo-60, Cs-137, Ir-192, Am-241,…Radionuclides are used extensively in industrial research, quality control of materials and constructions, for measuring thickness, density or volume of materials, in geological exploration, agricultural research, and even in household devices like smoke detectors.Radionuclide applications usually involve use of:-small quantities of radionuclides as tracers to follow the fate of certain chemicals or chemical elements or-sealed sources, frequently with relatively high radioactivity levels, for irradiation of other materials to change their properties or as heat/power source.For the most part, these are relatively short-lived (as compared with naturally occurring radioisotopes), but some of them may be very highly radioactive and hazardous. Safety and security of sealed sources is of particular importance because of the possibility of accidental (or malicious) exposure of members of the public to radiation at hazardous levels if these sources are not kept safe and secure.
8 Sources of Radioactive Waste (4) Medical applicationsDiagnosis and treatmentLarge number of administrations and operationsShort-lived liquid and solid wasteLarge activity administrationsHigh-activity sealed sourcesTc-99m, I-131, P-32, Y-90, Sr-89Co-60, Ir-192, Cs-137Radionuclides are used extensively in the medical field for clinical measurements, clinical diagnosis and therapy, and biological research, in the form of sealed sources, substrata containing radioisotopes and marked molecules.Radionuclides commonly used in these applications tend to have relatively short half-lives (i.e. a few hours to about one year). Exceptions include 14C (with a half-life of about 5600 years), 60Co (with a half-life of about 5 years), 137Cs with a half-life of about 30 years, and, in the past, 226Ra with a half-life of 1600 years (and several progeny, including radon and radon daughters).
9 Sources of Radioactive Waste (5) Research and developmentWide variety of usesWide variety of techniquesOther:historical sources - radium processingdefense programs – legacy wastesCleanup of contaminated sites has proven to be a large source of radioactive waste and also poses a number of challenges in terms of predisposal waste management. Sites can become contaminated with radioactivity in a number of different ways. Accidents, such as the dispersal of Cs-137 from a disused piece of medical equipment that was broken into, resulted in a large amount of contamination in Goiania, Brazil. A dedicated disposal facility was constructed for those wastes. Nuclear research and weapons production activities are also the source of contaminated sites in a number of countries.
10 Sources of Radioactive Waste (6) Wastes containing naturally occurring radioactivity (NORM)Phosphate industryProduction of metalsRefractory materialsEnergy Production (Oil and Gas, Coal, Biomass, Geothermal)Usually large volumes, Ra-226, Rn-222Naturally Occurring Radioactive Materials (NORM) comprise materials whose radioactive component comes from natural sources. The most obvious example are wastes arising in the mining, milling and smelting of uranium. But there are many other sources. In some cases the radioactivity content may be increased by the processing – either deliberately or not - and you may hear these referred to as “Technologically Enhanced Naturally Occurring Radioactive Materials” or TENORM. IAEA does not use this nomenclature because of the difficulty in deciding what is NORM and what is TENORM so we won’t use this term again in this leacture. The radioactive properties of NORM may be incidental to their use, but, especially if the radioactivity is concentrated as a result of human activities, these materials may be sufficiently radioactive to be classed as ILW. NORM can require management as radioactive waste. A variety of potential hazards exist from relatively low activities in large amounts of waste (up to millions or billions of tons each year) (coal ash, phosphogypsum, mining and mineral processing waste and produced water) to relatively large activities in smaller amounts of waste (e.g., scales from oil and gas wells, drinking water treatment wastes, concentrated mining residues).(See IAEA Tech Report Series No. 419 and Safety Guide SR-34 on Oil and Gas Industry)NORM poses a radiological concern due to the long-lived nature of the radionuclides (Ra-226, Uranium, Thorium) found in NORM wastes and due to the difficulties and cost of managing the very large amounts of waste that can be produced. Often the wastes are managed in piles that are covered or placed back in mines. In some cases, liquids are dispersed on the ground for evaporative treatment. As the liquid evaporates, radionuclides become concentrated in the surface soils.Mining and mineral processing is the largest source of NORM wastes due to the scale of the operations involved.For radionuclides posing more significant hazards such as some scales from oil and gas wells, the waste may be managed as LILW and disposed in a licensed facility.
11 Waste Management Approaches Waste and materialsPre-treatmentEffluent dischargeTreatmentRecycling and re-useConditioningClearanceDisposal
12 Waste Management Approaches ‘Delay and Decay’ – hold waste in storage until sufficient decay has occurred for desired management approach‘Concentrate and Contain’ – reduce volume and condition and/or containerize waste to limit dispersion in the environmentThe principal approaches to the management of radioactive waste are commonly termed ‘delay and decay’, ‘concentrate and contain’ and ‘dilute and disperse’. ‘Delay and decay’ involves holding the waste in storage until the desired reduction in activity has occurred through radioactive decay of the radionuclides contained in the waste. This is effective for many short-lived wastes from radionuclide applications, but can also be used as a minimization approach in the nuclear fuel cycle, e.g. by removing the highest-activity shortest-lived isotopes from the need for further consideration.‘Concentrate and contain’ means reduction of volume and confinement of the radionuclide contents by means of a conditioning process to prevent dispersion in the environment.‘Dilute and disperse’ means discharging waste to the environment in such a way that environmental conditions and processes ensure that the concentrations of the radionuclides are reduced to such levels that the radiological impact of the released material is acceptable.Summary for three slides:In establishing policies regarding the choice of waste management approaches, consideration has to be given to the radiological impacts of the different options. From a radiological protection perspective, a balance has to be struck between the present exposures resulting from the dispersal of radionuclides in the environment and potential future exposures which could result as a consequence of radioactive waste disposal.The first two approaches (‘delay and decay’, ‘concentrate and contain’) require that radioactive waste be held in storage for varying lengths of time or placed in a disposal facility with a view to preventing its release to the environment. Radioactive waste must therefore be processed, as necessary, in such a way that it can be safely placed and held in a storage or disposal facility.The third approach (‘dilute and disperse’) is a legitimate practice in the management of radioactive waste when it is carried out within authorized limits established by the regulatory body.‘Dilute and Disperse’ – discharge waste in a manner that environmental conditions reduce concentrations to acceptable levels
13 Waste classification - Purpose Purpose - for safety, engineering, operational and regulatory aspects:Devising radioactive waste management strategies, planning, designing and operating waste management facilities;Facilitating record keeping and giving a broad indication of the potential hazards involved in the various types of waste at the operational level;Communication between interested parties by providing well understood terminology (e.g., Joint Convention)The purpose of a waste classification system is to aid in planning and communication. If every waste form is described in terms of a complete list of properties such as the one on the previous slide, it is very difficult to develop an overall strategy that covers all waste forms, and there is a danger that the management of the waste will be fragmented into a number of small facilities, which is inefficient, costly and can be less safe for the public and the environment.In addition, communication about waste is highly important, not only between different groups today, but also between this generation and succeeding generations who will need to have available to them records of wastes that have been disposed of. This communication is facilitated by having a common, understood terminology, and waste classification forms part of that common terminology.
14 Possible ways to classify Some of the possible ways to classify waste:Classification by originNuclear fuel cycle, isotope production,..Classification by physical stateSolid, liquid, gaseousClassification by activity concentrationVery Low Level waste (VLLW), Low Level Waste (LLW), Intermediate Level Waste (ILW), High level Waste (HLW)Classification by half-lifeShort-lived waste, long-lived wasteSome of the possible ways to classify waste are based on the most obvious and important properties of the waste: physical state, activity concentration and half-life. These attributes are directly related to safety and hazard assessment, and therefore classification based on them aids planning for safety of waste management.Some other possible choices, such as classification by origin, are less directly related to safety or to other technical requirements for management, and may be based instead on more administrative concerns such as determining who is financially responsible for their management. However, a system based on such a choice can obscure the safety issues which are most important in the long term, and thus make development of a comprehensive strategy more difficult.
15 Need for a classification system? Permits appropriate decisions to be made at each step of lifecycle management of wastes.Provides a systematic foundation for waste segregation programmes.Efficient management system for operators (otherwise decisions are ad hoc or made on case by case basis).Provides essential input for national WM policy & strategy.One might ask: Do we really need a classification system?In response to this question: if there is no classification system, a number of undesirable consequences are possible:Low and high activity wastes can get mixed – this increases the volume of waste that must be managed as high-level waste in order to assure safety, and this increase in volume, besides increasing costs, violates the fundamental principle of waste minimization.Without classification, there is a poor basis for decisions on treatment, packaging, storage & disposal.Poor segregation can lead to mixing of wastes in different categories, requiring all wastes to be treated as though they contained all hazards.It is difficult to structure a systematic RP programme for a system where the materials being processed are highly heterogeneous.Without clear classification there is a weak basis for planning national WM strategy.Lack of classification makes it difficult to measure performance for operational improvements.
16 Summary of IAEA Waste Classification System (GSG-1) ObjectivesTo set out a general scheme for classifying radioactive waste that is based primarily on considerations of long term safety, and thus, by implication, disposal of the waste.To identify the conceptual boundaries between different classes of waste and provides guidance on their definition on the basis of long term safety considerations.The objective of this Safety Guide is to set out a general scheme for classifying radioactive waste that is based primarily on considerations of long term safety, and thus, by implication, disposal of the waste. This Safety Guide, together with other IAEA safety standards on radioactive waste, will assist in the development and implementation of appropriate waste management strategies and will facilitate communication and information exchange within and among States. Disposal is considered the final step in the management of radioactive waste, as stipulated in Safety Requirements publications on predisposal management of radioactive waste and disposal of radioactive waste.The Safety Guide identifies the conceptual boundaries between different classes of waste and provides guidance on their definition on the basis of long term safety considerations. While the usefulness is recognized of classification schemes for the safe operational management of radioactive waste, including the transport of waste, such schemes are subject to different considerations and are not addressed in this Safety Guide.
17 Summary of IAEA System GSG - 1 The IAEA systemExempt waste(2) Very short lived waste (VSLW)(3) Very low level waste (VLLW)(4) Low level waste (LLW)(5) Intermediate level waste (ILW)(6) High level waste (HLW)The IAEA’s waste classification system is based on the radiological properties of the waste. It divides waste into six broad categories:(1) Exempt waste4 (EW): Waste that meets the criteria for clearance, exemption or exclusion from regulatory control for radiation protection purposes as described in GSR Part 3.(2) Very short lived waste (VSLW): Waste that can be stored for decay over a limited period of up to a few years and subsequently cleared from regulatory control according to arrangements approved by the regulatory body, for uncontrolled disposal, use or discharge. This class includes waste containing primarily radionuclides with very short half-lives often used for research and medical purposes.(3) Very low level waste (VLLW): Waste that does not necessarily meet the criteria of EW, but that does not need a high level of containment and isolation and, therefore, is suitable for disposal in near surface landfill type facilities with limited regulatory control. Such landfill type facilities may also contain other hazardous waste. Typical waste in this class includes soil and rubble with low levels of activity concentration. Concentrations of longer lived radionuclides in VLLW are generally very limited.(4) Low level waste (LLW): Waste that is above clearance levels, but with limited amounts of long lived radionuclides. Such waste requires robust isolation and containment for periods of up to a few hundred years and is suitable for disposal in engineered near surface facilities. This class covers a very broad range of waste. LLW may include short lived radionuclides at higher levels of activity concentration, and also long lived radionuclides, but only at relatively low levels of activity concentration.(5) Intermediate level waste (ILW): Waste that, because of its content, particularly of long lived radionuclides, requires a greater degree of containment and isolation than that provided by near surface disposal. However, ILW needs no provision, or only limited provision, for heat dissipation during its storage and disposal. ILW may contain long lived radionuclides, in particular, alpha emitting radionuclides that will not decay to a level of activity concentration acceptable for near surface disposal during the time for which institutional controls can be relied upon. Therefore, waste in this class requires disposal at greater depths, of the order of tens of metres to a few hundred metres.(6) High level waste (HLW): Waste with levels of activity concentration high enough to generate significant quantities of heat by the radioactive decay process or waste with large amounts of long lived radionuclides that need to be considered in the design of a disposal facility for such waste. Disposal in deep, stable geological formations usually several hundred metres or more below the surface is the generally recognized option for disposal of HLW.
18 Summary of IAEA System GSG - 1 In the classification scheme, the following options for management of radioactive waste are considered, with an increasing degree of containment and isolation in the long term:—Exemption or clearance;—Storage for decay;—Disposal in engineered surface landfill type facilities;—Disposal in engineered facilities such as trenches, vaults or shallow boreholes, at the surface or at depths down to a few tens of metres;—Disposal in engineered facilities at intermediate depths between a few tens of metres and several hundred metres (including existing caverns) and disposal in boreholes of small diameter;—Disposal in engineered facilities located in deep stable geological formations at depths of a few hundred metres or more.The degree of containment and isolation provided in the long term varies according to the disposal option selected. The classification scheme set out in this publication is based on the consideration of long term safety provided by the different disposal options currently adopted or envisaged for radioactive waste. In the classification scheme, the following options for management of radioactive waste are considered, with an increasing degree of containment and isolation in the long term:—Exemption or clearance;—Storage for decay;—Disposal in engineered surface landfill type facilities;—Disposal in engineered facilities such as trenches, vaults or shallow boreholes, at the surface or at depths down to a few tens of metres;—Disposal in engineered facilities at intermediate depths between a few tens of metres and several hundred metres (including existing caverns) and disposal in boreholes of small diameter;—Disposal in engineered facilities located in deep stable geological formations at depths of a few hundred metres or more.The depth of disposal is only one of the factors that will influence the adequacy of a particular disposal facility; all the safety requirements for disposal as established in SSR Part 5 will apply.
19 Exempt Waste (EW)Waste that has been cleared, exempted or excluded from regulation as described in Safety Guide RS-G-1.7 “Application of the Concepts of Exclusion, Exemption and Clearance” (2004)
20 Very Low Level Waste (VLLW) Waste containing material that can be slightly above the exempt region. Disposal facilities for such waste do not need a high level of containment and isolation and near surface landfill is generally suitable. Typical waste would include soil and rubble with activity low enough not to require shielding.
21 Very Short Lived Waste (VSLW) Waste that can be stored for decay over a limited period of up to a few years and subsequently cleared for uncontrolled disposal or discharge after a suitable period of storage. This would include radioactive waste containing short half life radionuclides typically used for research and medical purposes.
22 Low Level Waste (LLW)Waste that contains material with radionuclide content above clearance levels, but with limited amounts of long lived activity. It requires robust isolation and containing for periods of up to a few hundred years typically 300. It includes a very broad band of materials that includes very high activity waste with short half life that requires shielding and some long lived material at relatively low activity levels. Such waste would require up to around 300 years of control but would not be hazardous beyond that period of time. The radionuclides within the waste will decay to activity levels that are acceptably low from a radiological safety viewpoint, within a time period during which institutional controls can be relied upon.
23 Intermediate level waste (ILW) Waste which, because of its high radionuclide content and the potential mobility of the materials involved requires a higher level of containment and isolation than is provided by near surface disposal. However, needs little or no provision for heat dissipation during its handling, transportation and disposal. It may include long lived waste that will not decay to an acceptable activity level during the time which institutional controls can be relied upon.
24 High Level Waste (HLW)Waste with radioactivity levels intense enough to generate significant quantities of heat by the radioactive decay process or with large amounts of long lived activity which need to be considered in the design of a disposal facility for the waste. Disposal in deep, stable geological formations is the preferred option for its disposal. It includes spent reactor fuel which has been declared as waste, vitrified waste from the processing of reactor fuel and any other waste requiring the degree of containment and isolation provided by geological disposal.
25 IAEA Waste Classification System (2009) Half-lifeActivity contentVSLW very short lived waste (decay storage)HLW high level waste (deep geologic disposal)ILW intermediate level waste (intermediate depth disposal)LLW low level waste (near surface disposal)VLLW very low level waste (landfill disposal)EW exempt waste (exemption / clearance)GeologicalIntermediateNear surfaceLandfillClearance
26 Classification as Practiced Many member states still use their own system, customized to fit local needs.Disposal endpoint is what is most commonly used to define waste classes.As part of Joint Convention, each country reports on national system of waste classification and reports a national inventory of radioactive waste.The proposed IAEA classification system has been adopted in some countries, but most countries continue to use their own national system of classification. In many cases this is based on the disposal endpoint. When that disposal endpoint is not delayed, this may not be a problem, but if disposal is deferred, there is a risk that the waste acceptance criteria (WAC) for the final disposal system may not be the same as originally envisaged, and a classification system which does not supply enough additional information to ensure that the new WAC will be met will be inadequate.Within the international arena, the Joint Convention requires Contracting Parties (countries) to report on their national waste management systems and inventories. The use of different national classification systems makes the peer review process more difficult, a point which has been remarked upon in the summary reports on the review meetings under the Joint Convention.
27 Waste Disposal Options Surface DisposalWell injectionNear-Surface DisposalGeological DisposalThis slide provides some examples of disposal concepts. Mined areas can be used for surface disposal of mining wastes or in the case of the photo in the upper left, also the ash and residues (NORM) from a coal fired power plant. Well injection is a form of geological disposal that is used for ground-up scales from oil and gas (NORM) as shown in the figure in the upper right. Surface discharge, including planned blending with surface soil, is used for some sludges from the oil and gas industry as shown in the photo in the bottom right, near surface disposal is used for many LILW (can be vaults like the center photo or engineered pits), and geological disposal is also used for HLW as well as LILW, including long-lived LILW as shown in the example in the lower left.Surface Discharge
28 Selection of Management Options Selected options must be consistent with National policies for waste management;Need to consider interdependencies with other predisposal and final disposal options;Adequate characterization of waste is critical.National policies for radioactive waste management will be a critical factor when selecting options for predisposal waste management. The presence or absence of regulations for clearance is one example of a predetermined option. In many cases, selected types of predisposal waste management facilities will be available, thus, options may already be identified. For example, incineration may be identified as the chosen alternative for volume reduction of combustible waste.Interdependencies (or constraints) imposed by decisions already made in other steps of the waste management lifecycle must be clearly identified early in the process of selecting options.As many choices between options will depend on the characteristics of the waste, it is critical to have an effective waste characterization program in place.
29 Safe Disposal of Radioactive Waste Objective/Scope of IAEA Publication SSR-5The fundamental safety objective is to protect people and the environment from harmful effects of ionizing radiationTo achieve this objective this publication sets out requirements on the site selection and evaluation and design of a disposal facility, and on its construction, operation and closure, including organizational and regulatory requirements
30 DisposalThe term ‘disposal’ refers to the emplacement of radioactive waste into a facility or a location with no intention of retrieving the waste.(The term disposal implies that retrieval is not intended; it does not mean that retrieval is not possible.)Disposal options are designed to contain the waste by means of passive engineered and natural features and isolate it from the accessible biosphere to the extent necessitated by the associated hazard.
31 The specific aims of disposal: to contain the waste;to isolate the waste from the accessible biosphere andto substantially reduce the likelihood of and all possible consequences of inadvertent human intrusion into the waste;to inhibit, reduce and delay the migration of radionuclides at any time from the waste to the accessible biosphere.to ensure that the amounts of radionuclides reaching the accessible biosphere due to any migration from the disposal facility are such that possible radiological consequences are acceptably low at all times.WASTEBIOPHRCONTAINISOLATEINHIBIT, REDUCE, DELAYSOURCESAFETY FUNCTIONSRECEIPIENTOBJECTIVEACCEPTABLY LOW IMPACTIn its preamble, the disposal document lists four “aims” of geological disposal that help to set the requirements in context.The first is that disposal should To contain the waste until most of the radioactivity, and especially that associated with shorter lived radionuclides, has decayed. The same aim also applies to near-surface disposalThe second is to isolate the waste from the biosphere and to substantially reduce the likelihood of inadvertent human intrusion into the waste. Note the difference between “containment”, which is about radionuclides and “isolation” which is about the wastes and human intrusion. In geological disposal, isolation is achieved by placing the wastes at depth and by avoiding natural resources. Isolation is also an aim of near-surface disposal but here it is achieved through institutional control (i.e. guards, fences).The third aim is to delay any significant migration of radionuclides to the biosphere until a time in the far future when much of the radioactivity will have decayed;Finally the fourth aim is to ensure that any levels of radionuclides eventually reaching the biosphere are such that possible radiological impacts in the future are acceptably low.The paragraph on the aims of geological disposal ends with the statement written here: the aim of geological disposal is not to provide a guarantee of absolute and complete containment and isolation of the waste for all time. This acknowledges that containment of all time is an impossibility
32 Safety Requirements applies to all of the types of disposal and disposal facilities Specific landfill disposalNear surface disposalDisposal of intermediate level wasteGeological disposalBorehole disposalDisposal of mining and minerals processing wasteSafety Guides provide comprehensive guidance on and international best practices for meeting the requirements in respect of different types of disposal facility.
33 Protection of people and the environment (1) The IAEA Safety Fundamentals publication Fundamentall SafetyPrinciples sets out the fundamental safety objective and safety principlesthat apply for all facilities and activities in radioactive waste management, including the disposal of radioactive waste.The ICRP developed a System of Radiological Protection that applies to all facilities and activities, and this system was adopted in the International Basic Safety Standards.The ICRP has elaborated the application of the System of Radiological Protection to the disposal of solid radioactive waste in its Publications 77 and 81 which it reconfirmed in Publication 103.This provides a starting point for the safety considerations relation to disposal facilities.
34 Protection of people and the environment (2) Radiation protection in the operational periodThe radiation safety requirements and the related safety criteria for the operational period of a disposal facility are the same as for any nuclear facility or activity involving radioactive material, and are established in the GSR part 3.In radiological protection terms, the disposal facility is considered to be a source of radiation that is under regulatory control in a planned exposure situation.Expect no significant releases of radioactivity during the operational period; no doses to publicThe primary goal is to ensure that radiation doses are as low as reasonably achievable (ALARA) and within the applicable system of dose limitation.Starting with the first of these three themes we note thatthe requirements for radiological protection are the same as for any licensed nuclear facility and are derived from the GSR part 3we also note that sources are under control, and the primary goal is to keep doses – to workers and the public - as low as reasonably achievableat the same time expect no significant releases of radioactivity during the operational period and no doses to the public;workers will be handling radioactive materials of course so doses to workers are expected but these must be controlled and monitoredwe also need to consider accidents and emergency planningfinally transport of waste to the site is to be considered, just as with any other facility. The IAEA Transport Regulations will usually be applied
35 Protection of people and the environment (3) Post Closure Safety CriteriaSafety objective: A reasonable assurance has to be provided that doses and risks to members of the public in the long term will not exceed the dose constraints or risk constraints that were used as design criteria.The dose limit for members of the public from all planned exposure situations is an effective dose of 1 mSv in a year, and this or its risk equivalent are considered criteria not to be exceeded in the future.To comply with this dose limit, a disposal facility is designed so that the estimated dose or risk to the representative person who may be exposed in the future as a result of natural processes affecting the disposal facility does not exceed a dose constraint of 0.3 mSv in a year or a risk constraint of the order of 10-5 per year.(Risk due to the disposal facility in this context is to be understood as the probability of fatal cancer or serious hereditary effects.)Assumed that protection of people against the radiological hazards associated with a disposal facility will also satisfy the principle of protecting the environmentDose estimates are simply indicators, not predictionsAlso under the second theme, the dose criteria to be applied in the post-closure period also come from Appendix of the GSR part 3Here we have “The dose limit for members of the public from all practices is an effective dose of 1 mSv in a year , and this or its risk equivalent is considered a criterion not to be exceeded in the future. To comply with this dose limit, a geological disposal facility (considered as a single source) is designed so that the estimated average dose or average risk to members of the public who may be exposed in the future as a result of activities involving the disposal facility does not exceed a dose constraint of not more than 0.3 mSv in a year or a risk constraint of the order of 10–5 per year. It is recognized that radiation doses to individuals in the future can only be estimated and that the uncertainties associated with these estimates will increase for times farther into the future. Care needs to be exercised in using the criteria beyond the time where the uncertainties become so large that the criteria may no longer serve as a reasonable basis for decision making.”The reason why the dose constraint is set below the dose limit is to recognise that members of the public could receive doses from more than one nuclear facility. Regulatory bodies are free to set their own national dose constraints, which will always be lower that the BSS values.
36 Inadvertent human intrusion in the post-closure period If such intrusion is expected to lead to an annual dose of less than 1 mSv per year to those living around the site, efforts to reduce the probability of human intrusion or to limit its consequences are not warranted.If HI is expected to lead to an annual dose of more than 20 mSv per year to those living around the site, alternative disposal options are to be considered, for example disposal of the waste below the surface, or separation of the radionuclide content giving rise to the higher dose.If annual doses in the range 1 – 20 mSv are indicated, reasonable efforts are justified at the facility development stage to reduce the probability of intrusion or to limit its consequences by optimization of the facility design.< 1 mSvMeasures not warranted> 20 mSvAlternative disposal1 – 20 mSvMeasures considered
37 Protection of people and the environment (4) Environmental and non-radiological concernsThe scope of safety requirements for disposal of radioactive waste is the protection of the environment against radiological hazards associated with the radioactive material in the disposal facility.The assessment of conventional environmental impacts such as may occur in the construction and operational period for a disposal facility, e.g. impacts relating to traffic, noise, visual amenity, disturbance of natural habitats, restrictions on land use and social and economic factors, as well as non-radiological toxic hazard also has to be assessed where this is significant.If non-radioactive materials may affect the release and migration of radioactive contaminants from the radioactive waste, then such interactions have to be considered in the SA.The third general theme concerns environmental and non-radiological matters and here we aim to show the scope of the geological requirements documentThe disposal requirements document does not concern itself with the kind of environmental effects that might accompany construction and operation – we are thinking here about traffic, noise, visual amenity, disturbance of natural habitats and so on. The main focus of the document is on radiological effectsSecond the document assumes (along with ICRP 103) that, by choosing appropriate representative person (critical groups), protection of people against the radiological hazards associated with a geological disposal facility will also protect the environment. This is an issue that is under discussion internationallyNext we recognise that dose calculations are simply that – calculations. We do not truly know what the radiological impact will actually be but we expect that we can make an indicative estimate of it.Finally if the disposal facility contains non-radioactive toxic material (e.g. Pb) then this will need to be taken into account in the ass
38 Safety Requirements for safe disposal of Radioactive Waste In order to meet the basic objective, i.e., to ensure safety of waste disposal facilities, 26 requirements have been established in the IAEA publication SSR-5
39 List of 26 requirements (1/2) Safety Requirements for safe disposal of Radioactive WasteList of 26 requirements (1/2)government responsibilitiesregulatory body responsibilitiesoperator responsibilitiesimportance of safety in the development processpassive safety of the disposal facilityunderstanding of facility and for confidence in safetymultiple safety functionsContainment of radioactive wasteIsolation of radioactive wasteSurveillance and control of passive safety featuresstep by step development and evaluation of facilitiesPreparation and use of the safety case and safety assessmentscope of the safety case and safety assessmentdocumentation of the safety case and safety assessmentIn all there are 26 requirements and here they areRead out the list then continue to next slide
40 List of 26 requirements (2/2) Safety Requirements for safe disposal of Radioactive WasteList of 26 requirements (2/2)site characterization of disposal facilitydesign of a disposal facility designconstruction of a disposal facilityOperation of a disposal facilityclosure of a disposal facilitywaste acceptance in a disposal facilitymonitoring programmes in a disposal facilitythe period after closure and institutional controlsstate system of accounting for, and control of, nuclear materialrequirements in respect of nuclear securitymanagement systemsexisting disposal facilitiesFinish reading the listRemember that this has been taken from SSR-5, which relates to Disposal of Radioactive Waste. the list applies to all type of waste disposal. Thank you.
Your consent to our cookies if you continue to use this website.