The main radioactive waste disposal points for accident waste are the Buriakovka, Podlesny and III line of ChNPP sites. These three near-surface disposal sites were established after the accident to dispose of RAW from remediation actions carried out during the first year following the accident. These sites were chosen and designed for the disposal of higher level acci­dent waste than the RAW located in the temporary RAW store points.

Buriakovka, built in 1987, is the only disposal facility currently in opera­tion in the ChEZ. It comprises 30 trenches covered with a 1 m clay layer (see Fig. 11.4). Up to 590,000 m3 of RAW has been disposed of, with a total

radioactivity of 2.5 x 1015Bq of solid short-lived low and intermediate level waste. It consists of metal, soil, sand, concrete and wood contaminated with 90Sr, 137Cs, 134Cs, 238,239,240Pu, 154,155Eu and 241Am.

The Podlesny vault-type disposal facility was commissioned in December 1986 and closed in 1988. The facility was designed for the disposal of HLW with a dose rate 0.1 m from the surface in the range of 0.05-2.5 Gy h-1. The total RAW volume of 11,000 m3 of building material, metal debris, sand, soil, concrete and wood was placed in two vaults. The disposal facility was covered with concrete at its closure. In 1990 the estimated total radioactivity of the disposed waste was 2,600TBq.

The III line of ChNPP vault-type facility was based on reconstructed facilities of the unfinished units 5 and 6 at the ChNPP site. This facility was in operation from October 1986 until 1988 and was designed for low and intermediate level waste corresponding to dose rates up to 0.01 Gy tr1 at 0.1 m from the surface of the waste container. More than 26,200 m3 of solid waste with a total activity of 4 x 1014 Bq was disposed of in 18,000 containers and later covered with sand and clay. This waste is mainly sand, concrete, metal, construction material and bricks. Due to the high level of groundwa­ter at different periods of the year, the facility is flooded 0.5-0.7 m above its bottom.

This book examines the extensive international experience of the manage­ment of radioactive wastes. Part I introduces in nine chapters the back­ground to, and principles of, radioactive waste (RAW) management and contaminated site clean-up including waste types and sources of contamina­tion, along with processes and technologies for decommissioning, decon­tamination and immobilisation as well as consideration of international safety standards. Part II, the bulk of the book, contains 15 chapters sum­marising the current status of management and clean-up in countries from across the world including a separate chapter covering the Fukushima inci­dent of March 2011. While we endeavoured to cover the whole planet, we were unable to find authors from all countries who were available in the timescale required and so, for example, India is a regrettable omission. Nonetheless, the book presents a thorough and clear view of the interna­tional state of play in this area, which is so crucial for the environment and the future of civil nuclear power which it seems can never be separated from politics and the always appropriate but sometimes ill-informed con­cerns of the public over safety. Thus, for example, England and Wales are covered in a separate chapter from Scotland, whose government has chosen a different path for the management of its wastes. Part III, comprising just three chapters, covers clean-up of sites contaminated by weapons pro­grammes in the USA and the former USSR. Undoubtedly there are others but either we are unaware of them or no-one was willing to provide infor­mation about them. While the nuclear community recognises the need for openness and transparency, particularly in the civil nuclear sector, this does not yet, understandably, always fully extend to the military.

Editing a book of this size is an enormous undertaking but it does give the editors an excellent overview and the opportunity to detect key themes in the field. Those which have emerged for us include the importance of developing new waste forms for some of the difficult wastes which to date have been left in the ‘too difficult for now, leave until later’ category. Plutonium (Pu), iodine (I) and technecium (Tc) are radionuclides which are difficult to incorporate into stable solids and some wastes are ill-defined

so that creativity as well as scientific soundness and engineering pragmatism are needed when developing waste forms to immobilise them. Chapter 6 highlights key new waste form developments using room temperature (non­thermal) and thermal techniques, in particular for production of glass com­posite materials (GCMs).

Safety is obviously the most important concern when dealing with radio­activity and the need for international agreements and collaborations is crucial, as described in Chapter 3. Underpinning safety, and our understand­ing of the future behaviour and stability of waste forms, temporary stores and permanent geological disposal facilities, and the transportation mecha­nisms of radionuclides in the biosphere, is a swathe of computer modelling and performance assessment codes. Developments in theory and simulation and modelling are having significant impact in all areas of technology, and RAW management, with its enormous scales of size, time and complexity, will undoubtedly benefit from these developments.

The book is intended as an introductory overview for post-graduate students and researchers in this field but will also be useful for undergradu­ates studying physics, chemistry, materials, geography, geology, and environ­mental or other engineering disciplines with an interest in the welfare of the planet. It will also be a valuable resource for training programmes in new nuclear countries. Inevitable in an edited book with many interna­tional authors there are differences of style and approach. There is some repetition between chapters but we believe this is tolerable in order for each to remain as a stand alone resource. We asked each author to include a map of their region to give a better understanding of the geography and to indicate further sources of information for the interested reader. We acknowledge the enormous efforts made by the authors of each chapter and also the team at Woodhead Publishing for their help and support over the three years it has taken to put this book together.

Professor William (Bill) Lee Professor Michael Ojovan Dr Carol M. Jantzen

The VLLW category comprises the wastes for which the activity concentra­tion is slightly higher than that required for EW, but VLLW does not need a high level of containment and isolation. Landfill type facilities with limited regulatory control, used, for example, for other non-radioactive hazardous waste, can be used for disposal. A typical source of such waste is decom­missioning of nuclear facilities, when large volumes of very low contami­nated soil, rubble, concrete, thermal insulation, etc., are generated. Concentrations of long-lived radionuclides (e. g., nuclear fuel components) in VLLW are generally very limited.

The main safety requirements for protection of workers, the public and the environment during all stages of decommissioning as set down in the international safety standards [41] emphasise the importance of considering both radiological and non-radiological hazards in an integrated manner. Decommissioning activities are considered to be part of the original prac­tice, and the safety requirements of the Basic Safety Standards [38] apply to all decommissioning activities.

It is important that a safety culture is fostered and maintained in both the operating organisation and that individuals responsible for decommis­sioning activities are trained to appropriate levels of awareness of health, safety and environmental matters. Safety needs to be maintained during the entire decommissioning process and beyond if a facility is to be in compli­ance with the site release criteria [43]. As with pre-disposal and disposal, the safety requirements for decommissioning apply to governments, opera­tor organisations and the regulatory body.

The national legal framework for decommissioning needs to include provisions for the use, possession, storage and handling of all radioactive material generated during decommissioning.

All phases of decommissioning, from the initial plan to the final release of the facility from regulatory control, must be regulated. The regulatory body responsible for all phases of decommissioning must establish the safety standards and requirements for decommissioning, and carry out activities to ensure that the regulatory requirements are met.

The operating organisation is responsible for all aspects of safety and environmental protection during the decommissioning activities and must provide financial assurances and resources to cover the costs associated with safe decommissioning, including management of the resulting radio­active waste.

The operating organisation is also required to define a decommissioning strategy consistent with national decommissioning and waste management policy. The preferred decommissioning strategy is immediate dismantling; however, if another practical strategy is selected it needs to be based on evaluation of factors such as: the availability of waste disposal or long-term storage capacity for decommissioning waste; the availability of a trained workforce; the availability of funds; co-location of other facilities on the same site requiring decommissioning; technical feasibility; and optimisation of the radiation protection of workers, the public and the environment. The strategy must be justified and it must be demonstrated that in the future no undue burdens will be imposed on future generations.

It is important that the strategy includes provisions to ensure that, if final shutdown occurs earlier than expected, the facility shall be brought to a safe configuration and a decommissioning plan is in place for approval and implementation.

It is essential that appropriate means are available to manage waste (including pre-disposal and disposal) of all categories [3] in a timely manner, with account taken of the overall decommissioning strategy. This involves the application of the concept of clearance [44] of material resulting from decommissioning activities, i. e. material or items released from regulatory control. For sites with more than one facility, a global decommissioning programme needs to be developed for the entire site that ensures interde­pendences are taken into account in the planning for individual facilities.

It is important that the operating organisation prepares and maintains a decommissioning plan throughout the lifetime of the facility (from the design stage to termination of activities) that shows that the decommission­ing can be accomplished safely to meet the defined end state. For existing facilities where a decommissioning plan does not yet exist, a suitable plan for decommissioning needs to be prepared as soon as possible.

The decommissioning plan has to be supported by an appropriate safety assessment covering the planned decommissioning activities and any abnor­mal events that may occur during decommissioning. The assessment must address occupational exposure and potential releases of radioactive ma­terial with resulting exposure of the public.

A graded approach needs to be applied to development of the decommis­sioning plan commensurate with the type and extent of hazards. The initial plan must be reviewed and updated periodically, at least every five years or as prescribed by the regulatory body, or when specific circumstances warrant, such as if changes in an operational process lead to significant changes to the plan. The plan must address all relevant safety aspects (see [45-47]) such as carrying out a baseline survey of the site, retaining key staff and ensuring that institutional knowledge about the facility is maintained.

Prior to the implementation phase of decommissioning (about 2 years), a final decommissioning plan must be prepared and submitted to the regula­tory body for approval. Interested parties have to be provided with an opportunity to review the final decommissioning plan and to provide com­ments on the plan to the regulatory body prior to its approval.

National legislation must set out the responsibilities with respect to finan­cial provisions for decommissioning (e. g., mechanism for adequate financial resources for safe and timely decommissioning). It is very important that adequate finances for safe decommissioning, including the management of the resulting waste, are available when needed, even in the event of prema­ture shutdown of the facility, and financial assurances to provide for the required resources have to be in place before authorisation to operate the facility is given. If financial assurance for the decommissioning of an exist­ing facility has not yet been obtained, suitable funding provision needs to be put in place as soon as possible. Provision for financial assurance is required prior to licence renewal or extension.

Where the decommissioned facility is released with restrictions on its future use, financial assurance adequate to ensure that all necessary controls remain effective have also to be obtained before authorisation is terminated by the regulatory body.

An organisation for the management and implementation of decommis­sioning has to be established as part of the operating organisation, with the responsibility for ensuring that decommissioning will be conducted safely. Regardless of the type of organisational arrangements, the ultimate respon­sibility for safety remains with the operating organisation, although it is permissible to delegate the performance of specific tasks to a subcontractor. The operator must ensure that individuals responsible for performing activ­ities during the decommissioning process have the necessary skills, expertise and training to complete the decommissioning process safely. This must be in line with a comprehensive quality assurance programme under the oper­ating organisation’s management system [48] and be applied to all phases of decommissioning. It is important that the management of the decommis­sioning project is tailored to the project’s complexity and size and to the associated potential hazards.

The operating organisation must implement the decommissioning and related waste management activities in compliance with the national safety standards and requirements. The operating organisation must also inform the regulatory body prior to shutting down the facility permanently and the implementation of the decommissioning plan can only start after regulatory approval is issued.

In the case of deferred dismantling, the operating organisation has to ensure that the facility has been placed, and will be maintained, in a safe configuration and will be appropriately decommissioned in the future. To provide an adequate level of safety, the operating organisation must, inter alia, prepare and implement appropriate safety procedures; apply good engineering practice; ensure that staff are properly trained and qualified and are competent; and keep and submit records and reports as required by the regulatory body.

Decontamination and dismantling techniques must be chosen such that the protection of workers, the public and the environment is optimised and the hazards and the generation of waste are minimised.

It is important that prior to using any new or untried decommissioning methods, the use of such methods must be justified and addressed within an optimisation analysis supporting the decommissioning plan. Such analyses must be subject to review and approval by the regulatory body.

Emergency planning arrangements, commensurate with the hazards, need to be established and maintained and incidents significant to safety reported to the regulatory body in a timely manner. A proper waste man­agement path for all waste streams arising from decommissioning activities must also be provided.

Upon completion of decommissioning, it must be demonstrated that the end state criteria as defined in the decommissioning plan and any additional regulatory requirements have been met. The operating organisation can only be relieved of further responsibility for the facility after approval by the regulatory body [43].

A final decommissioning report must be prepared that records, in par­ticular, the end state of the facility or site, and this report must be submitted to the regulatory body for review. In this respect, a system must be estab­lished to ensure that all records are maintained in accordance with the records retention requirements of the quality assurance system and the regulatory requirements. If waste remains stored on the site after decom­missioning, a revised or new, separate authorisation, including requirements for decommissioning, must be issued for the facility. If a facility cannot be released for unrestricted use, appropriate controls need to be maintained to ensure protection of human health and the environment. These controls must be specified and approved by the regulatory body.

The history of recycling of used nuclear fuels traces its lineage back to the 1940s and the Manhattan Project (Rhodes, 1986). Having begun with co­precipitation technologies, the multiple advantages of solvent extraction — based processing significantly improved the efficiency and throughput of recycling. Introduction of solvent extraction methods also dramatically reduced the amount of HLW produced during recycling operations. During the first several decades of this enterprise, the principal driver for reprocess­ing was plutonium production to support the weapons programs of the nuclear nations. Dating from the mid-1950s, the system of choice for pluto­nium isolation and recovery from dissolved used fuel has been the PUREX (plutonium uranium recovery by extraction) process. When introduced, the PUREX process represented a significant leap forward in efficiency over the solvent extraction processes that it replaced (REDOX and BUTEX; Nash et al, 2006).

In PUREX, contact of a 3-6 m HNO3 solution containing all but the most volatile products of fission with an immiscible kerosene solution of tributyl phosphate (TBP) allowed selective extraction of UO2(NO3)2 and Pu(NO3)4 from a mixture of fission products and mixed actinides. With careful control of the conditions of extraction, all fission products, the transplutonium actinides and neptunium remain in the aqueous raffinate for ultimate dis­posal as high level wastes. Operation of the solvent extraction system with multiple stages and a counter-current flow of aqueous and organic phases results in a high purity Pu/U nitrate organic solution almost completely devoid of fission products or minor actinides (Np, Am, Cm).

From this solution the plutonium is readily (and selectively) removed with the application of a suitable reducing agent (early applications employed Fe(II) sulfamate, more recently U(IV) or HN2OH/N2H4 have been employed as reducing agents). The resulting pure Pu product is well suited to further purification to the metallic state or the creation of MOX ceramic fuel in combination with fresh UO2. Most of the uranium is removed from the TBP phase by reducing the acidity; the remainder is scrubbed with complexants to allow the extractant to be recycled back to the head end of the process. Because the isotopic distribution of the uranium is altered during its time in the reactor, this material is not at present recycled back to the MOX fuel, but rather stored for future use. The PUREX process has seen more than 50 years of process improvements and remains today the standard for Pu/U recycle. Various adaptations of this extraction system include options for extraction of Np(VI or IV) and the preparation of mixed U/Np/Pu mixtures to increase the proliferation resistance of the fissile material.

Historically, the crystallization of vitreous waste forms has always been regarded as undesirable, as it has the potential to alter the composition (and hence, durability) of the remaining continuous glass phase, which would (eventually) come into contact with water. However, there has been a recent trend toward higher crystallinity in ostensibly vitreous waste forms so that they are more correctly termed GCMs. This is particularly apparent in the development of hosts for more difficult waste or where acceptable durability can be demonstrated even where significant quantities of crystals (arising from higher waste loadings) are present. Acceptable durability will result if the active species are locked into the crystal phases that are encap­sulated in a durable, low-activity glass matrix. The GCM option is being considered in many countries, including Australia, France, Russia, South Korea, the UK, and the US. The processing, compositions, phase assem­blages, and microstructures of GCMs may be tailored to achieve the neces­sary material properties.

Joule heated melters are relatively intolerant of crystal growth in the melt which causes slag formation [161]. Recently, Sellafield has shown the ability to go to 38 wt% waste loading [162] from 25 wt% waste loading [163] by allowing spinel formation in the melt, but the Sellafield melter is induction heated not a JHM design. However, 1-2% crystallization of spinels is planned for Hanford ’s HLW AJHM and it is anticipated that the spinel crystals will stay buoyant from the melt pool agitation afforded by the bub­blers [164, 165] ’ This strategy can be made to work unless during long maintenance outages when the melter is idled, the crystals grow larger than the size that the agitation can sustain. Otherwise, the melt pool will have to be diluted with components that dilute the spinel-forming tendencies because JHMs and AJHMs cannot be drained without causing damage to the electrodes. In addition, the spinels that form cannot be redissolved into the melt except at >1,400°C, which is a temperature that cannot be achieved with the Inconel® electrodes in the AJHM. Therefore, cold crucible induc­tion-heated melters (CCIM), which are already being pursued in Russia, France, and the US, will have to be substituted as an alternative to JHM and AJHM melter technology. The major advantages of CCIM over JHM/ AJHM are higher productivity, higher temperatures, longer lifetime, smaller dimensions, can be drained as the heating is external, and can be stirred which allows higher waste loadings while maintaining the same product quality. Thus CCIM is robust in terms of producing GCMs and mineral waste forms by a melt and controlled crystallization route.

Advances in the techniques to measure and quantify how and where radionuclides are bonded in glasses and glass ceramics will enable GCMs to be tailored to sequester the desired radionuclides in the ceramics phases and either minimize or prevent the radionuclides from migrating to the glassy encapsulating phase. This will allow the crystalline and glass struc­tures based on MRO and LRO to be used to model glass and GCM behav­ior and properties.

Mineral waste forms will advance using novel processing techniques like templating. Hybrid waste forms, e. g. glass-ceramics instead of glass vs. ceramic, geopolymeric cements combining geopolymers and cement, or methods that combine thermal treatment (calcining, FBSR) with encapsula­tion in geopolymers or cements will provide double barrier composites for troublesome waste species.

The organization responsible for implementing the remediation activities should have, or should have access to, competent staff to cover the following areas adequately:

• safety requirements of any permits or authorizations issued;

• regulatory standards and issues;

• radiation protection;

• conventional industrial hazards;

• data collection and evaluation;

• environmental monitoring;

• quality assurance and quality control;

• radiochemical analysis;

• geological and hydrogeological expertise;

• waste management;

• site security;

• project management (IAEA, 2006a); and

• skills and (human, technical and scientific) resources to tackle the ER challenges safely and cost-effectively.

In many cases contractors may be used to perform some or all steps of the remediation plan; however, the responsible party (licencee), as identified by the regulatory body, is required to remain responsible for the safety of all activities, including those performed by contractors. Non-radiological hazards, such as hazards due to chemical contamination, may also be present, and existing staff may not be familiar with the various aspects of the requirements for protection against these hazards. Appropriate levels of control, supervision and training should be provided to ensure the safety of workers (including contractors) with regard to all hazards.

All persons involved in the remediation should be made familiar with the contaminated area, the hazards and the safety procedures for the safe and effective performance of their duties. Specialized training may be needed in certain areas of work. For some activities, the use of mock-ups and models in training can enhance efficiency and safety. The requirements for a basic training programme and for re-training should be stated in the remediation plan.

Moscow has the world’s first system of radiation-ecological monitoring (REM) [29], on the basis of observations taken of the environmental radia­tion characteristics of an area (Fig. 10.11).

The introduction of an analytical REM system [30] using information from radio-ecological data processing units has helped to solve the prob­lems posed by integrated radio-ecological data processing. The system col­lects and analyses data from a variety of sources, including the subdivisions of the radiation emergency service, radiation-hygienic control, regional systems of RAW and RAM accounting, laboratory complexes, automated radiological control systems, and systems for monitoring the radon content in public buildings.

Studies on the detection of centres of radioactive contamination were all carried out in one facility in Moscow, which carried out accounting and monitoring of RAM and RAW and analysed the information that indicated the level of radiation present in the city, thereby ensuring the radiation safety of the population. A number of other projects were completed in the same facility, with the aim of providing radiation safety from natural radionuclides, by means of observation and control of natural sources of irradiation — (housing, industrial buildings, construction sites, and so on). Radiation-ecological monitoring of the environment was carried out

Stationary post of radiation monitoring (atmospheric air, precipitation)

Stationary range (surface water, bottom deposits)

Monitor-post (soil, snow cover, vegetation)

Aqueous monitor-post (surface water, bottom deposits)

Automatic gauge of the radiation background

in annual cycles by means of a system of stationary locations for monitoring radiation levels in the ground, air and water, while the individual radiation doses of Moscow citizens were also analysed.

Overall, a number of measures aimed at ensuring the population’s radia­tion safety during the removal of RAW from the city were successfully developed. The work carried out in the REM framework 8 led to the acqui­sition of significant experience in developing radiation monitoring systems, which in turn has led to the optimization of the organization of environ­mental radiation control [31].

While the above highlights the need for a clear end-point (permanent geo­logical disposal), political will and public support, much radioactive waste management must be done prior to disposal. Radioactive waste manage­ment approaches vary from country to country. However, a key aspect is to know what waste you have. A national inventory must be collected as is done in the UK (NDA, 2010a) and all other countries.

Figure 1.8 shows a flowchart for solid radioactive waste management prior to disposal, i. e., pre-disposal (Ojovan, 2011). Figure 1.9 reveals that all activities concerned with radioactive waste are conventionally divided into pre-disposal and disposal stages.

Disposal is the final step in managing radioactive wastes whereas pre­disposal includes activities such as decommissioning, pre-treatment, treat­ment, conditioning, immobilisation, storage and transport. While various disposal options are available, it is most likely that immobilised wastes will be disposed of in GDFs of one sort or another.

Waste management requires a series of steps:

• pursuing opportunities for waste minimisation

• re-use and recycling

• waste treatment

• packaging

• storage

• transport and then final disposal where required.

This waste hierarchy indicates the preferred options in the managing of waste where disposal is very much the last option; it can be represented as in Fig. 1.10 .

Waste minimisation is a process of reducing the amount and activity of waste materials to a level as low as reasonably achievable. Waste minimisa­tion is now applied at all stages of nuclear processing from power plant design through operation to decommissioning. It consists of reducing waste generation as well as recycling, reuse and treatment, with due

for both primary wastes from the original nuclear cycle and secondary wastes generated by reprocessing and clean-up operations. Waste minimisa­tion programmes were largely deployed in the 1970s and 1980s. The largest volume of radioactive waste from nuclear power production is LLW. Waste minimisation programmes have achieved a remarkable tenfold decrease of LLW generation over the past 20 years, reducing LLW volumes to approxi­mately 100 m3 annually per 1 GW(e).

Recycling means recovery and reprocessing of waste materials for use in new products. Recycled waste can be substituted for raw materials reducing the quantities of wastes for disposal as well as potential pollution of air, water, and land resulting from mineral extraction and waste disposal. However, recycling has certain limitations when applied to radioactive materials. Due to their inherent radiation, radionuclides are much more difficult to recover from contaminated materials. Recovery usually pre­sumes concentration of species into a smaller volume even though this may result in more dangerous materials. Waste radionuclides recovered from contaminated materials are difficult to recycle in new devices or com­pounds. Hence even materials which contain large amounts of radioactive constituents (e. g., SRS) often are immobilised (conditioned) and safely stored and disposed of rather than recycled.

One example of recycling in the nuclear industry is of spent fuel. There are 435 currently operating NPPs in 30 countries which produce 368.2 GWe. A typical NPP generating 1 GW(e) produces annually approximately 30 t of SF. The annual discharges of spent fuel from the world’s power reactors total about 10,500 tonnes of heavy metal (t HM) per year and the total amount of SF that has been discharged globally is approximately 334,500 tHM (Bychkov, 2012). During use, only a fraction of fuel is burnt, generating electricity but also forming transmutation products that may poison it. After use, the fuel elements may be placed in storage facilities with a view to permanent disposal or be reprocessed to recycle their reus­able U and Pu. Most of the radionuclides generated by the production of nuclear power remain confined within the sealed fuel elements. Currently only a fraction of SF is reprocessed in countries such as France and the UK, although countries with large nuclear power programmes such as Russia and China plan to significantly increase the reprocessing capacity (Table 1.7). Also the US is reviewing the approach to open nuclear fuel cycle con­sidering reprocessing as a viable option.

Despite the complexity of such a process, recycling of fissile elements (U, Pu) from SF results in a significant reduction of toxicity of the radioactive wastes (Fig. 1.11 ).

Another potential example of recycling in the nuclear industry is of mili­tary grade Pu, much of which is stockpiled in the US, Russia and the UK; a legacy of the Cold War. Since 1972, world production of plutonium has exceeded demand for all purposes. The total world plutonium inventory is not reported but a rough calculation indicates at least 2,000 metric tonnes at the beginning of the twenty-first century. It is technically possible to convert this material into a mixed U/Pu oxide (MOX) reactor fuel so that it can be used to generate energy in a suitable nuclear reactor. MOX nuclear fuel consists either of UO2 and PuO2 either as two phases or as a single phase solid solution (U, Pu)O2 (Burakov et al., 2010). The content of PuO2 may vary from 1.5 to 25-30 wt% depending on the type of nuclear reactor. Whereas most efficient burning of plutonium in MOX can only be achieved in fast reactors, it is currently used in thermal reactors to provide energy, although the content of unburnt plutonium in spent MOX fuel remains significant (>50%).

Key aspects of waste management are to reduce the hazards associated with wastes and the volume of the waste material. Hazard can be reduced substantially by converting highly mobile liquid or gaseous wastes into stable solid forms using the techniques indicated in Figs 1.8 and 1.9. Immobilisation reduces the potential for migration or dispersion of con­taminants including radionuclides. The IAEA defines immobilisation as the conversion of a waste into a waste form by solidification, embedding or

encapsulation. It facilitates handling, transportation, storage and disposal of RAW. Another term closely linked with immobilisation is conditioning.

Treatment of primary RAW includes operations intended to benefit safety and economy by changing the waste characteristics. Three basic treat­ment objectives are:

• volume reduction

• removal of radionuclides

• change of physical state and chemical composition.

As seen in Figs 1.8 and 1.9 , such operations include: incineration of com­bustible waste or compaction of dry solid waste (volume reduction); evapo­ration, filtration or ion exchange of liquid waste streams (radionuclide removal); and neutralisation, precipitation or flocculation of chemical species (change of composition). The waste volume reduction factor (VRF) of a treatment process is defined as the ratio of initial volume of the treated waste V0 to the final volume after treatment V/. VRF = VJVf. The higher the VRF, the more efficient is the treatment process. However, volume reduction inevitably leads to concentration of radionuclides which may impact on the safety and economics of the process. Treatment may lead to

Time, years

1.11 Relative radiotoxicity of SF and resulting HLW on reprocessing and recycling. FP, fission products; MA, minor actinides. The time required to achieve the initial toxicity of uranium ore is significantly reduced on recycling and transmutation of MA.

several types of secondary RAW such as contaminated filters, spent resins and sludges. After treatment, depending on the radionuclide content in the waste, it may or may not require immobilisation.

The final objective of waste processing is to transform ‘as generated’ waste to the form suitable for final disposal, providing for high safety and avoiding any significant burden to the environment and population. Several tech­nologies have been developed and implemented to process various types of waste and waste streams. All of them are generally aimed at reducing the original waste volume and providing sufficiently stable and durable waste forms, suitable for long-term storage and ultimate disposal.

Basically two approaches can be applied for the reduction of ‘as gener­ated’ waste volumes:

1. Removal (concentration) of radionuclide contamination from the waste and processing of the small volume of concentrate as higher (intermedi­ate) level radioactive waste. After removal of radioactive material from the waste, the bulk of the original waste volume can be managed as non-radioactive (cleared from regulatory control) or very low radioac­tive material at common conventional landfills, or discharged to water reservoirs (sea, river). Significant reduction of liquid waste volume can be achieved in this way. However, some complications should be expected in relation to handling and further processing of the waste concentrate as intermediate level waste.

2. Reduction of volume of ‘as generated’ waste (e. g., by evaporation of liquid waste or thermal treatment/pyrolysis of solid waste) for further conditioning into a waste form suitable for disposal. The waste matrix in this case represents the bulk of the processed waste volume and, therefore, more space is required in the storage or disposal facility.

Selection of a waste processing route and a decision on its implementation is a complicated process, where technical, economic, safety and other aspects as well as level of industrial development, size of nuclear industry, availabil­ity and type of waste disposal options available in a country should be considered and evaluated. Typical examples of different approaches to waste storage and disposal, leading to different waste processing approaches are, on one hand, the Netherlands, where controlled long-term (100 years) storage of processed waste in special surface storage facility is implemented, while, on the other hand, Germany, where deep geological disposal is the only considered option for all kinds of waste. This latter approach could benefit from higher flexibility in selection of waste processing tech­nologies. And the third, classic example is the case of several European countries, operating near-surface repositories for disposal of processed low and intermediate level waste, where strict WAC requirements must be obeyed.