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In this stage were developed the following activities:
This stage, by establishing the decontamination methodologies to be applied to radioactive wastes generated by decommissioning of CANDU power plants, contributes to the opportunities arising in the minimisation of radioactive wastes, that are considered a better strategy to avoid, as much as possible, generation of unwanted secondary products from decommissioning, i.e. radioactive wastes. The final purpose of the decontamination and decommissioning procedures used for nuclear facilities is the unconditioned release or reuse of site, facilities or material for dissimilar purposes. Must be emphasised that in order to minimise the radioactive wastes volumes generated by decontamination operations for decommissioning of nuclear facilities, shall be included only those activities that remove or diminish the effects of all range of individual factors that are influencing the decommissioning. A recycling and reuse strategy must demonstrate a net benefit when are considered health and safety of personnel, population and environment. Therefore, an analyse performed for a recycling and reuse complete fuel cycle shall contain not only the radiologic impact but, also, the environment risk and impact related to the material generation and energy consumption. Diminution of waste volumes to be intermediate or final disposed will reduce the potential risks for population and environment; thus, will be diminished potential costs and future financial responsibilities. These savings are a substantial benefit. Main objective of reuse and recycling procedures, as part of the global concept regarding waste minimization, must reduce the impact on environment, as well as the total costs involved. Practically, usually exists a compensation between benefits arising from program implementation and total costs for the achievement of such benefits. Consequently, global optimization shall be considered a mean to improve the efficiency of selection process between various alternatives for radioactive wastes and materials management and supplementary to radiation protection. Global optimization must address to a wide range of problems, including non-radiological risks such as: chemical exposure health risks, industrial accidents and transport activities, non-radiologic impact on environment, soil, air, water and other natural resources, and social and economical impact (e.g. public acceptance, commercial factors and ethical issues). Within technical reports there were identified several radioactive waste treatment and conditioning methods that could be used for Cernavoda NPP wastes. From these based on cost benefit analysis performed in cooperation with EDATA were established the optimum technologies for treatment and conditioning of analysed wastes. National strategy on long and intermediate period regarding radioactive wastes and spent nuclear fuel management, inclusive final disposal and nuclear and radiological facilities decommissioning is part of the National Nuclear Plan, approved by Government Decision no. 1,259/2002, with the following objectives concerning radioactive wastes and spent nuclear fuel management: 1. Derived objectives on radioactive wastes management
2. European objectives on radioactive waste management
AN&DR strategy on low and intermediate level waste disposal, and, also for the mixed ones, states and has as objective the commissioning of final repository for low and intermediate level wastes (DFDSMA) until 2017. On the other hand wastes arising from Cernavoda NPP must be treated in order fulfil the acceptance criteria of DFDSMA. Corresponding Radioactive Waste Treatment Facility is in the responsibility of Cernavoda NPP. As a result this facility must achieve the conditioning and treatment of radioactive wastes that arise both from NPP operation and from future decommissioning activities of the nuclear facilities such as to comply with de receipt criteria of DFDSMA. In this stage there were applied management methodologies for intermediate level and mixed wastes from their arising during the decommissioning of nuclear power units (with reference to Cernavoda NPP) up to final disposal either by a surface repository (SITON proposed a possible location on Saligny site) or by a geologic repository; there is a specific case in which these wastes could be recovered and recycled if there is any restant economic value from this. Also, in order to realize a full evaluation were predicted management modalities for all waste categories including the following activities: reception, control – sorting, treatment, conditioning and waste disposal, that lead to several costs related to acquisition, rent and maintenance of equipments, materials, labour, utilities etc. Safety management, at industrial level, of radioactive wastes generated in Romania, is a high priority objective of the national policy in order to support sustainable development of nuclear energetic. National policy for radioactive waste management is totally compliant with the international requests, established by “Joint Convention of Safety Management of Spent Fuel and Radioactive Wastes”, approved by Law no. 105/1999, as well as with the management policy of radioactive wastes promoted by European Union. Main objective of the national policy for radioactive waste management is to assure a theoretic nul negative impact or a practical minimum reasonable impact of the waste management activities on population and environment. A first step in this direction refers to the conformity assurance for the management process with the IAEA principles, that lead to the development of Safety Series No. 111-F "Fundamental principles on radioactive waste management”. An another important objective of national policy consists in the harmonization of specific regulations with those employed in European Union. National strategy on intermediate and long term referring to safety management of radioactive wastes defines the general mode of organization and development of radioactive wastes management processes, the envisaged aim being the fulfilment of the following specific objectives:
Strategy is applied in all stages of management process and for all nuclear facilities. Strategy is not used for those radioactive wastes that are naturally born and originate outside the nuclear fuel cycle with the only exception of the case in which these are not closed sources of nuclear radiations or they are declared as radioactive wastes by the licensed bodies. Nowadays, most of radioactive wastes generated by Romania are due to nuclear activities related to power generation at Cernavoda NPP Unit 1, commissioned in 1996. By the commissioning in 2007 of Cernavoda NPP Unit 2, nuclear power production doubled, and as a result the radioactive waste volumes doubled for this industrial activity field. Use of radioisotopes in industry, medicine, research and other social and economical areas also contributes with a small quantity to the total volumes of radioactive wastes. Radioactive wastes generated by operation of CANDU 6 reactors are divided in two main categories: spent fuel and low and intermediate wastes. Spent fuel was not in the scope of this paper; for this waste type exists in this moment an acceptable solution for a period of 50÷100 years. The removal of low and intermediate level waste of type LILW-SL (short lived low and intermediate level wastes) by final disposal is nowadays a common industrial practice, both at international level and in European Union. The practices used for the management of these wastes are not adequate for the management of HLW (high level wastes), the latest leading to major risks on human health and environment. According to international regulations, for safety operation of Nuclear Power Plants, we must assure a proper management of radioactive wastes and effluents generated from activity. In any project regarding a Nuclear Power Plant (NPP), we must ensure that treatment-conditioning and storage of waste from the decommissioning process, is done safely, so that the foreseeable impact of the adverse effects on future generation not be greater than impact on the present generation. This work is a study of innovative technologies and strategies used in management of nuclear waste generated from decommissioning of CANDU nuclear facilities. The study is structured in following sections: General information on the main categories of radioactive waste considered;
Categories of radioactive waste Radioactive wastes are wastes containing artificial radionuclides. Radioactive waste, is the result of a process such as nuclear fission. According to the International Atomic Energy Agency (IAEA), the level of radioactivity and half-life are the main parameters used in next classification. The specific risk levels of different types of radionuclides and radiation emitted are also considered. International Atomic Energy Agency classification of radioactive waste.
In the following table and associated graph, we present estimated volumes of radioactive waste, which will be managed at national level, after Cernavodă NPP decommissioning. Radioactive waste volume estimated at Cernavodă NPP decommissioning
Innovative technologies used in treatment and conditioning of radioactive waste In this section of the study, the modern technologies of processing and conditioning of radioactive nuclear waste are analyzed. Technologies have been analyzed in terms of the costs, results obtained from parameterization and simulation of workflow processes, designed according to specific categories of waste. Into the study, Monte Carlo simulation methodology was used, simulation done with ProVision 6.1.1. instrument. In the study, we analyze following categories of waste:
For each such waste, were designed technological workflows used in treatment-conditioning activities, were loaded cost parameters, and after simulation, were generated corresponding reports. As example, below, we present analysis of spent filter cartridge waste.
Cost Distribution Grid
Conclusions There were analysed 5 alternatives for the development of Treatment Facility for Radioactive Wastes (STDR) to be part to the Final Repository for Low and Intermediate Level Wastes (DFDSMA) Saligny. STDR was first proposed for the conditioning and treatment of radioactive wastes generated during the operation of Cernavoda NPP, but its service life could be extended in order to process also the wastes to be generated by decommissioning activities of power plant units with consequent modification and upgrades. Used conditioning and treatment technologies will significant influence, as shown previous, the dimensioning of storage capacity of final surface repository DFDSMA Saligny. The 5 proposed technology alternatives by experienced organisations in this field have applicability both for low level wastes and also for intermediate level and mixed wastes. Within this paper, there were only shown, based on short description of mentioned technologies, those references at intermediate level and mixed wastes. Considering the arisings of wastes, the operation and decommissioning, especially for case of the nuclear power plants, are the most important source for low and intermediate level wastes worldwide. The volume of low and intermediate level wastes that result from decommissioning of four units CANDU 6 was estimated in this work. The processing and final disposal of decommissioning wastes utilise the bulk part of the total budget allocated for a facility and an extensive effort in order to diminish these costs is a key objective for the radioactive waste management. The minimization of waste quantities is a complex process that consists mainly in the minimization of the generated wastes and the minimization of the volume of wastes to be final disposed. . Intermediate level and mixed wastes produced by operation and decommissioning of 4 CANDU 6 units at Cernavoda NPP will be disposed either at Final Repository for Low and Intermediate Level Wastes (DFDSMA) Saligny (short lived intermediate level and mixed wastes) or at Long Life Geologic Repository (DGVL) (long lived intermediate level wastes); the conceptual project of this repository was shortly presented by this work. Also, for a full evaluation, it was emphasised and was proposed the route for very low level wastes disposal to a surface repository named final repository for low level wastes (DFDFSA). Safe evaluation of the decommissioning costs that must include also radioactive waste management costs is an important part of the Decommissioning Plan. Alternative technologies for radioactive wastes management can be evaluated and it can be performed a comparison based on efficiency and generated benefits versus a basis price. Also, they can be evaluated versus safety and benefits arising from their use. When this plan is fully developed these considerations regarding costs show that this is economically reasonable and could be financed by funds collection during Cernavoda NPP operation. It is noticed that currently the Decommissioning Plan for U1 and U2 at Cernavoda NPP is yet not approved by CNCAN due to the lack of data to justify the stages for decontamination and radioactive waste management. Also, the limited area available for DFDSMA Saligny imposes the routing of research – development efforts in order to manage as much effective the wastes generated by the decommissioning of Cernavoda NPP units that are about 2/3 from the total quantity of radioactive wastes generated by decommissioning. The treatment facility for radioactive wastes generated by decommissioning must achieve the transformation of radioactive wastes into the final form for disposal; conclusions to this work could be used for the design of this facility due to the fact that they demonstrated the effectiveness based on cost – benefits analyse for optimum proposed methods for treatment and conditioning. Must be noticed that nowadays radioactive wastes that are generated by the operation of two units at Cernavoda NPP are not adequately treated in order to be final disposed. Also, this paper identify optimum decontamination methods for main contaminated surfaces for a CANDU 6 power plant, i.e. metallic surfaces and concrete surfaces. There were identified optimum decontamination methods for the whole 65000 m2 concrete surfaces and 85000 m2 metallic surfaces that contain contamination at a CANDU 6 unit. The selected decontamination methods are based on cost – benefits analyses in which there were identified also secondary wastes, inclusive theirs treatment possibilities and that demonstrated the interconnections between the decontamination methods and radioactive waste management systems. Main results of this phase can be synthesised according to the following reported data. By decontamination and radioactive waste management generated by decommissioning of a CANDU nuclear power plant – particularly for Cernavoda NPP – the following aspects must be emphasised: a) From the point of decontamination of radioactive wastes - the following techniques, part of chemical decontamination methods: Chemical foams & Gels and TechXtract, are the most recommended for metallic surfaces
- the following techniques, part of physical decontamination methods: Strippable Coatings, Centrifugal Shot Blasting, Concrete Grinder, En-vac Robotic Wall Scabbler, Grit blasting and Soft Media Blast Cleaning (Sponge Blasting) are the most recommended for concrete surfaces
b) From the point of view of radioactive wastes conditioning/treatment the following aspects are to be emphasised: - for non-compactable wastes, such as: metallic wastes, including wastes from retubbing, the recommended methods for treatment cutting and shredding, and if available supercompaction; - for compactable wastes, such as: spent filter cartridges, certain concrete types, the recommended treatment methods are cutting and shredding and supercompaction, respectively; - for ionic resins it is recommended reagents treatment; - for mixed wastes, such as: tritiated solvents, tritiated oils, solid materials soaked with tritiated oils, tritiated scintillation liquids the recommended processes for treatment are emulsioning (permits encapsulation of liquid organic wastes within cement matrix) and as a particular case it is mentioned the combination solid wetted materials with tritiated oils - NOCHAR polimerization. Considering the importance of radioactive waste management that, for specific case of CANDU power plants, are 43% from total decommissioning costs versus the effective decommissioning costs that are of about 35%, it is obvious that the development of decontamination plans development and for radioactive waste management associated with decommissioning plan is a priority for the licensing of U1 and U2 operation as well as for U1 and U4 future commissioning. Both for radioactive waste management and for nuclear power plants decommissioning were founded separated funds in order to cover the related costs to these activities. Keeping in mind the funds that are engaged and developed by mobilisation of certain percentage from the total costs of produced electrical energy by nuclear power units, results the importance of cost-benefit analyses on radioactive waste management and decontamination. Keeping in mind that in future more than 40% from energy generated in Romania will be from nuclear power units, it is obvious the importance of this paper that can give a major contribution for the assessment of such funds with implications on final price of electricity at the consumer. In this context, the responsibility for development of more extended works has a major contribution on public acceptance regarding the expansion of nuclear power program in Romania.
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