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International Nuclear Forum BULGARIAN NUCLEAR ENERGY – NATIONAL, REGIONAL AND WORLD SAFETY

Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 A. Ivanova, I. Ovcharova ( ENPRO CONSULT LTD ). International Nuclear Forum BULGARIAN NUCLEAR ENERGY – NATIONAL, REGIONAL AND WORLD SAFETY BULATOM , M ay 28-30, 2008 , Varna, Bulgaria.

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International Nuclear Forum BULGARIAN NUCLEAR ENERGY – NATIONAL, REGIONAL AND WORLD SAFETY

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  1. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2A. Ivanova, I. Ovcharova (ENPRO CONSULT LTD) International Nuclear Forum BULGARIAN NUCLEAR ENERGY – NATIONAL, REGIONAL AND WORLD SAFETY BULATOM, May 28-30, 2008, Varna, Bulgaria

  2. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 1 Introduction Following the Contract for joining the European Union, the Council of Ministers of the Republic of Bulgaria took a decision and shut down the first and second units at Kozloduy NPP (KNPP) on 31.12.2002in accordance with Decision № 848 of 19.12.2002. At present units 1 and 2 possess a license for operation in mode „Е” – storage of the spent fuel in the spent fuel pools. According to the order of BNSA, from the beginning of December 2006 the licenses for operation of KNPP units 1 and 2 have been modified; this does not change the current status – operation of the units in mode „Е”, but allows for dismantling of the systems and equipment, which are not important for safety and do not contain radioactive substances above the free release levels. The next step is obtaining a licence for Stage 1 decommissioning activities – Safe enclosure (SE) and dismantling in Turbine hall. The development of Decommissioning Safety Analysis Report (DSAR) is one of the documents needed for this license. BULATOM

  3. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 2 Specific features of units 1&2, related to the decommissioning Kozloduy NPP Units 1 and 2, type WWER 440, model B 230 have some design and structural peculiarities, which impact the SE. These are: • Equipment, which is common for the whole NPP site; • Buildings and systems, common for two or four WWER-440 units; • Some of the consumers of the First Boilers’ Unit of Unit 1 are common for the plant site and others are common for Units 1 and 2. During the preparation for decommissioning measures have been foreseen and implemented for all specific features, having an impact on decommissioning. A number of infrastructure projects have been realized, including the physical separation of Units 1&2 from Units 3&4, erection of buildings, etc. BULATOM

  4. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 3 The Option for KNPP Units 1 and 2 Decommissioning Kozloduy NPP approved an Updated Decommissioning Strategy for Units 1÷4 in June 2006. According to this “Continuous Dismantling Strategy”, the decommissioning of Units 1 and 2 will be done in two stages. The generalized schedule for continuous dismantling is the following: BULATOM

  5. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 Safe enclosure zone of units 1 ÷ 4 9 2 1 5 4 6 3 8 7 SE of Units 1&2 Rest of SE 1 – Reactor building 1 (Units 1 & 2) 2 Reactor building II (Units 3 & 4) 3 – Auxiliary building 1 4 – Auxiliary building 2 5 – Sanitary and laboratory building 1 6 – Sanitary and laboratory building 2 7 – Vent tube (stack) 1 8 – Vent tube (stack) 2 9 – Turbine hall BULATOM

  6. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 4 The scope and the structure of DSAR The content of the DSAR for decommissioning of Unit 1 is prepared in compliance with the documents: • “Regulatory guide for the preparation of a safety analysis report for decommissioning of nuclear reactors”, December 2006; • “Safety assessment for decommissioning of facilities using radioactive material”, IAEA Guide, DS376, 2007. This document is elaborated on the basis of the: • Decommissioning Plan for KNPP Units 1 and 2, December 2007; • Technical Design for decommissioning of KNPP Units 1 and 2, PHARE Contract BG-9809-02-03. The DSAR document is prepared for Stage 1 of the Decommissioning, which is planned for 2011-2018 and includes: • The preparatory activities for the safe enclosure of the reactor building of Units 1 and 2; • The dismantling of systems and equipment outside the Safe Enclosure Area; Safe Enclosure of RB. BULATOM

  7. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 DSAR consists of 13 chapters: • Chapter 1 “Introduction” is an introductory one to the rest of the document. It presents the regulatory framework for elaboration of the safety analysis report for decommissioning. • Chapter 2 “Description of the Facility” gives a general description of the unit and of the main systems and activities from the viewpoint of decommissioning. • Chapter 3 “Site Evaluation” presents the Kozloduy NPP site characteristics and the assessment of the potential external impacts. • Chapter 4 “Design Basis of the Decommissioning” includes the basic safety objectives and principles, the classification of the systems for the given state of decommissioning, the requirements with respect to the human factor, the fire and physical protection of the facility. BULATOM

  8. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 • Chapter 5 “Description and justification of the processes and the systems” provides information about the systems, important for radiation safety during decommissioning and about the new systems, installed for the specific decommissioning activities. • Chapter 6 “Safety Analysis” is still not finalized. It defines the relevant acceptance criteria for normal operation and for accidents, the methodology for accident analysis and the approach which is envisaged to be applied for the hazard analysis at the given stage of decommissioning. The chapter includes a summary of the analysis of the external hazards. • Chapter 7 “Decommissioning Activities” provides information about the main activities inside and outside the safe enclosure zone for the considered stage of decommissioning. Here the methods for decontamination and the techniques/equipment for dismantling and size reduction are included too. BULATOM

  9. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 • Chapter 8 “Safety Management” describes the organization for management of safety, the package of management tools (instructions, regulations, etc.), qualification and training of personnel, safety culture, etc. • Chapter 9 “Limiting Conditions of Operation” describes the specifics of the operational limits for the systems, important for radiation safety. • Chapter 10 “Radiation Protection” describes the application of the principle ALARA during the execution of all decommissioning activities, including the dose budgets estimation. • Chapter 11 “Emergency Preparedness” presents the emergency plan of Kozloduy NPP, which remains in force till the final shutdown of the last unit on the site. BULATOM

  10. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 • Chapter 12 “Radioactive Waste Management” describes the categorization of RAW and the management of the radioactive waste flows at Unit 1. • Chapter 13 “Quality Management” indicates the main principles, laid in the quality assurance program for decommissioning and for the related activities. BULATOM

  11. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 5 Design basis of the decommissioning 5.1 Safety objectives and safety principles The main safety objective, as defined in the IAEA standard SF-1 “Fundamental safety principles”, is to protect people and the environment from the harmful effects of ionizing radiation. To ensure that facilities are operated and activities conducted so as to achieve the highest standards of safety that can reasonably be achieved, measures have to be taken: • To control the radiation exposure of people and the release of radioactive material to the environment; • To restrict the likelihood of events that might lead to a loss of control over a nuclear reactor core, nuclear chain reaction, radioactive source or any other source of radiation; • To mitigate the consequences of such events if they were to occur. BULATOM

  12. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 The fundamental safety objective applies for all facilities and activities and for all stages over the life time including decommissioning. The same Standard SF-1 formulates ten safety principles, on the basis of which are developed the safety requirements and the safety measures to be implemented in order to achieve the fundamental safety objective.These principles are listed bellow: Principle 1: Responsibility for safety The prime responsibility for safety must rest with the person or organization responsible for facilities and activities that give rise to radiation risks. This aspect of the decommissioning process is addresses in Chapter 8 “Management of safety”. BULATOM

  13. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 Principle 2: Role of government An effective legal and governmental framework for safety, including an independent regulatory body, must be established and sustained. In Bulgaria these matters are settled by Chapter II “Government regulation” of the Act on the safe use of nuclear energy. This chapter of the law defines the functions, structure and financing of the Nuclear Regulatory Agency. Principle 3: Leadership and management for safety Effective leadership and management for safety must be established and sustained in organizations concerned with, and facilities and activities that give rise to, radiation risks. The problems of organization of safety, safety culture, ageing management etc. are addressed in Chapter 8 “Management of safety” of DSAR. Chapter 6 “Safety analysis” includes the analysis of hazards arising during decommissioning. BULATOM

  14. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 Principle 4: Justification of facilities and activities Facilities and activities that give rise to radiation risks must yield an overall benefit. In many cases, decisions relating to benefit and risk are taken at the highest levels of government, such as a decision by a State to embark on a nuclear power programme. This evaluation has been performed at the stage of decision making for the construction of Kozloduy NPP. At the stage of decommissioning it has to be demonstrated that the risk is not higher than in the stage of operation of the nuclear facility. The evaluation of the radiation risk is presented in Chapter 10 "Radiation protection” and Chapter 6 “Safety analysis”. Principle 5: Optimization of protection Protection must be optimized to provide the highest level of safety that can reasonably be achieved. BULATOM

  15. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 The problems of optimization of protection are addressed in Chapter 3 “Site evaluation”, Chapter 6 “Safety analysis” and Chapter 10 “Radiation protection”. Chapters 4 and 5 present the physical protection and the fire safety of decommissioning. Principle 6: Limitation of risks to individuals Measures for controlling radiation risks must ensure that no individual bears an unacceptable risk of harm. Chapter 10 “Radiation protection” presents the application of the ALARA principle to the radiation risk during decommissioning. The application of this principle shall provide the highest possible margin to the fulfilment of the dose criteria for the workers and for the population, as they are defined in the Regulation for the basic norms of radiation protection. BULATOM

  16. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 Principle 7: Protection of present and future generations People and the environment, present and future, must be protected against radiation risks. Radioactive waste management is a major component of the process of decommissioning. Chapter 12 “Radioactive waste management” addresses the topics of RAW treatment, minimization, etc. Principle 8: Prevention of accidents All practical efforts must be made to prevent and mitigate nuclear or radiation accidents. The most adverse consequences during decommissioning may arise as a consequence of loss of radioactive source or loss of control over a radioactive source. The principle of defence in depths is incorporated in the plant design. The assessment of the efficiency of the barriers against uncontrolled release of radioactivity to the environment is addressed in Chapter 10 "Radiation protection” and Chapter 6 “Accident analysis”. BULATOM

  17. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 Principle 9: Emergency preparedness and response Arrangements must be made for emergency preparedness and response for nuclear or radiation incidents. Emergency preparedness is addressed in Chapter 11 of DSAR. Principle 10: Protective actions to reduce existing or unregulated radiation risks Protective actions to reduce existing or unregulated radiation risks must be justified and optimized. Chapter 7 “Decommissioning activities” gives a complete review of all activities at the given stage of decommissioning. Both the nuclear and the industrial aspect of each activity is assessed. BULATOM

  18. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 5.2 Classification of structures, components and systems 5.2.1 Safety functions and related structures, components and systems The safety functions and the associated structures, systems and components (SSC) are defined both for the planned decommissioning activities, and for accident conditions. The safety functions required during decommissioning comprise a combination of safety functions that were needed during facility operation and additional functions that need to be delivered as a result of the specific decommissioning activities.During the decommissioning stage, which is a subject of DSAR, the following fundamental safety function shall be ensured (article 32 (2) of Regulation for Providing the Safety of Nuclear Power Plants): „Confinement of the radioactive products within the prescribed boundaries”. BULATOM

  19. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 In Section 5 of DSAR, the safety functions, specific for the different phases of Stage 1 of the decommissioning, are discussed in detail. According to the Regulation for Providing the Safety of Nuclear Power Plants and to the IAEA standard NS-R-1, the systems which remain in operation during both phases - preparation for safe enclosure and safe enclosure - of Units 1 and 2 ensure the fulfilment of the following safety functions: • To ensure integrity and tightness of the Reactor Building and the Auxiliary Building so that to avoid the exposure of the personnel and the environment; • To limit the staff and population exposure in case of release of radioactive substances from sources outside of the hermetic zone of the reactor installation; • To limit the release of liquid and gaseous radioactive substances (aerosols) within the licensed limits; BULATOM

  20. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 • To maintain the environmental conditions necessary for the safety systems functioning and for the staff service while performing safety-related operations; • To provide physical barriers to the uncontrolled release of radioactive materials to the environment; • To ensure effective radiation monitoring of the environment. • To ensure reliable electrical power supply; • To ensure reliable fire-alerting and fire extinguishing systems in order to prevent common cause failures of systems important to safety as a result of fire. Since the nuclear fuel is removed from the safe enclosure area and is transported to the spent fuel storage at the beginning of Stage 1, all safety functions related to control of reactivity, maintaining the reactor in a safe sub-critical state and decay heat removal are not relevant to the process of decommissioning. BULATOM

  21. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 The importance of a given safety function with respect to ensuring of safety defines the safety class of this function. The higher the class of a safety function is, the higher are the requirements to the SSCs that support it. The class of a safety function helps to define the level and type of testing, checks and maintenance of the respective SSCs. The class of the safety function of a given SSC has an impact on the assumptions with respect to this SSC in the safety assessment. BULATOM

  22. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 5.2.2 Classification of SSCs The classification of SSCs is presented in details in Chapter 9 of the Decommissioning plan for units 1 and 2 [4]. All existing systems are classified there in three categories: • I category – Systems, which are important for nuclear safety and radiation protection • II category- Systems, which are important for industrial safety and operation • III category - Not important systems, i.e. they can be isolated and/or dismantled. After the completion of the preparation stage the systems ensuring nuclear safety are not needed, therefore their category changes from I to III. BULATOM

  23. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 The use of the existing systems during the SE phase, as well as the use of the systems for the dismantling phase during and after the SE, was evaluated very prudently. This was done by answering to the following questions on all the systems: • Is the system needed for SE operation? • Do the system lifetime and capacity meet the SE operational requirements? • Is the system needed after SE (for dismantling of cranes and other transportation equipment after the end of the SE)? • Is it reasonable to conserve the system? A differentiation is made between categories I and II, since the requirements for the systems are different with respect to their functions. The systems in category III can be dismantled (or isolated, or conserved) after separation from the remaining systems. BULATOM

  24. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 Based on the above-mentioned questions, a second classification is adopted, where the systems from the three groups (I, II and III) were classified according to four additional criteria: • 1.Modification is required; • 2.Modification is not required; • 3.An unnecessary system; • 3a – to be isolated • 3b – to be conserved • 3c – to be dismantled • 4.New equipment. BULATOM

  25. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 6 The safety assessment approach A graded approach has been used for the safety assessment. According to this approach, the scope and the level of the detail in the analysis are relevant to type of the hazards. 6.1 The safety objectives for decommissioning • Ensuring of nuclear safety (for the phase of final shut down and operation in mode “E”, which are out of the scope of this document) • Nuclear fuel sub-criticality; • Nuclear fuel cooling. • Ensuring of adequate radiation protection • Defence in-depth • Implementation of approach of optimization of radiation protection, which is aimed at controlling of the dose intake below the prescribed limits (ALARA) • Avoiding of radioactive substances discharges above the admitted levels BULATOM

  26. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 • Ensuring of the occupational industrial safety of the workers • Fire safety. The nuclear safety requirements are not a subject of this document, because the stage after the removal of all the nuclear fuel is treated and the requirements are not applicable. The requirements for the industrial safety of the personnel do not change in connection with the decommissioning and these are also not treated in details in DSAR. The radiation safety is the subject of Chapter 10 “Radiation Protection” under normal operational conditions and of Chapter 6 “Safety Analyses” in case of deviation from the normal operation and in case of accidents. A description of the existing Fire Protection system is presented in Chapter 4 “Design Basis of the Decommissioning” and in Chapter 5 “Description and justification of processes and systems”. BULATOM

  27. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 6.2 Safety requirements and criteria The safety of nuclear power plants (NPP) is defined as a capability the impact of the plant to the population and the environment to be maintained within the frame of the established limits. This capability is based on sequentially positioned physical barriers that avoid the discharge of radioactive materials as well as on a great number of means that protect these barriers from damages. Safety requirements for NPP are a set of plant specific indicators and respective acceptance criteria, allowing for an objective safety assessment of the plant. Safety assessment of NPP is ananalysis of all the available data by the use of modern methods, aiming to confirm that the respective safety requirements have been met. BULATOM

  28. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 The main safety requirements and criteria during the considered decommissioning stage are related to the radiation protection. The objective of the safety analysis is to evaluate the radiological impact of the planned activities and potential accidents on the workers, public and environment. The objective of the safety analysis is: • To support the selection of the decommissioning strategy, the elaboration of the decommissioning plan and the relevant specific decommissioning activities; • To demonstrate that the radiological impact on the workers and public is within the prescribed limits, that it is as low as reasonably achievable (ALARA) and that the protective measures are optimized. BULATOM

  29. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 The hazards for the population, workers and environment, related to decommissioning, are: • Radiological – e.g. external exposure from direct and other radiation sources, internal exposure through inhalation, ingestion, or cuts and abrasions and loss of containment leading to the uncontrolled release of radionuclides; • Toxic and other dangerous – e.g. asbestos, flammable materials, carcinogens, chemicals used for decontamination purposes, asphyxiants; • Industrial – e.g. dropped loads, working at heights, fires, high temperatures, and high pressures. BULATOM

  30. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 Combined and additive effects of these hazards are considered to the extent to which they could give rise to radiological consequences to workers, public and environment. The safety criteria, applied for all decommissioning activities, are derived from the regulatory documents in force in Bulgaria. They define the limits for: • Doses for the workers; • Doses for the public; • Radioactive releases to the environment; • Impacts of chemicals and other non-radioactive hazards. The acceptance criteria for the radiological consequences are defined for normal operation and for anticipated operational occurrences. BULATOM

  31. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 The annual effective dose per an individual of the public, resulting from the discharge of liquid and gaseous material into the environment for all operational states and for all nuclear facility at the site shall be lower than 0.15 mSv. The main objective of the safety analysis is to demonstrate that the acceptance criteria are met for all credible initiating events. 6.3 Methodology for the analysis The methodology, which is applied for the analysis of the IEs includes the following steps: • Identification of hazards, screening and identification of scenarios; • Determining of the activity inventory, relevant for each scenario; • Calculation of the effective dose for the workers and for the public. BULATOM

  32. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 The goal of the process of hazards identification is to identify all locations within the facility where radioactive material exists (intentional and inadvertent accumulations of radioactive materials and radioactive waste, surface contamination, contaminated ground, sources, activated components and ventilation system filters). The identification process considers also the potential new sources of radiological exposure of the workers as a result of the planned decommissioning activities: • Internal initiating events at the facility or the site; • Human induced initiating events; • External initiating events – natural and man-made. The radiological consequences for the workers and for the public will be calculated for the identified bounding scenarios. BULATOM

  33. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 7 Regulatory frame and other referred documents The DSAR document is developed based on the following Bulgarian regulations: • Act on the Safe Use of Nuclear Energy, in force since 01.01.2005, State Gazette No. 63/28.08.2002, modifications and amendments in State Gazette No. 70/10.08.2004 • Environmental Protection Act, Prom. SG No 91 dated 25 September 2002, amended SG No 98 dated 18 October 2002 • Regulation for the procedure for issuing licenses and permits for safe use of nuclear energy, prom. SG No 41/18.05.2004 • Regulation for Providing the Safety of Nuclear Power Plants , State Gazette No. 66/ 30.07.2004, modifications and amendments in State Gazette No. 46 from 2007 • Regulation for the safety of the decommissioning of nuclear power plants, State Gazette No. 73/20.08.2004 BULATOM

  34. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 • Regulation on the conditions and procedure for transfer of radioactive waste to the state enterprise “Radioactive Waste”, State Gazette No. 64/23.07.2004 • Regulation for safe management of radioactive waste, State Gazette No. 72/18.05.2004 • Regulation for the procedure for assessment, collection, spending and control of the financial resources and definition of the contributions due to the "Nuclear Facilities Decommissioning" Fund, State Gazette No. 112/23.12.2003, modifications and amendments in State Gazette No. 78/2005, No. 20/2006, No. 110/21.12.2007 • Regulation for the procedure for assessment, collection, spending and control of the financial resources and definition of the contributions due to the "Radioactive Waste", State Gazette No. 112/23.12.2003 • Regulation on radiation protection during activities with sources of ionizing radiation, State Gazette No. 74/24.08.2004 BULATOM

  35. Safety Analysis Report for Decommissioning of KNPP Units 1 and 2 • Regulation of the conditions and procedure for establishing of zones with special status around nuclear facilities and sites with sources of ionizing radiation, SG State Gazette No. 69/06.08.2004 • Regulation for emergency planning and emergency preparedness in case of nuclear and radiation accident, No 189, 30.07.2004, State Gazette No. 71/ 13.08.2004 • Regulation on Providing the Physical Security Assurance of Nuclear Facilities, Nuclear Material and Radioactive Substances State Gazette No. 77/03.09.2004 • Health Law, State Gazette No. 70/10.08.2004, last amendment State Gazette No. 102/19.12.06 • Act on the healthy and safe working condition, State gazette No. 124/24.12.1997, last revision State gazette No. 40/18.05.2007 BULATOM

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