NUCE 304: Evaluative Methods for Nuclear Non-proliferation and Security Lecture 12 PDF

NUCE 304: Evaluative Methods for Nuclear Non-proliferation and Security Nuclear Safety Dr. Ahmed Alkaabi 1  Introduction to Nuclear Safety There are two major aspects to Nuclear Safety – Safety Culture – Safety Enabli...

NUCE 304: Evaluative Methods for Nuclear Non-proliferation and Security Nuclear Safety Dr. Ahmed Alkaabi 1  Introduction to Nuclear Safety There are two major aspects to Nuclear Safety – Safety Culture – Safety Enabling Tools 2  Introduction to Nuclear Safety What is the definition of “nuclear safety”? 3  Introduction to Nuclear Safety Nuclear Safety Philosophy “…Before a plant is licensed to operate, the regulator must have “reasonable assurance that adequate protective measures can and will be taken (to protect the public) in the event of a radiological emergency.” 4  Introduction to Nuclear Safety There is no absolute safety because radionuclide release cannot be completely avoided. – Nuclear power, as with anything, involves some degree of risk – Releases during normal operation are kept as low as reasonably practical ALARA: As Low As Reasonably Achievable 5  Introduction to Nuclear Safety Question: How safe is safe enough? 6  Introduction to Nuclear Safety Nuclear reactor safety is considered in – Design of a reactor – Licensing and regulation – Construction – Operation – Maintenance – Operating experience evaluation – Accident management planning – Emergency response preparations 7  Introduction to Nuclear Safety Nuclear Safety - Per IAEA Guidelines Operating conditions, prevention of accidents/mitigation of consequences, resulting in the protection of workers, the public, and the environment from undue radiological hazards. Nuclear Safeguards Prevention and detection, through the use of material control and accountancy, of theft or diversion of special nuclear material from civilian facilities. Nuclear Security Prevention and detection of, and response to sabotage, unauthorized access, or other malicious acts involving nuclear material, other radioactive substances or their associated facilities. SAND2010-8826P 8  Safety Culture IAEA Defines Safety Culture as “…that assembly of characteristics and attitudes in organizations and individuals which establishes that, as an overriding priority, protection and safety issues receive the attention warranted by their significance.” References: 1.INTERNATIONAL ATOMIC ENERGY AGENCY, The Management System for Facilities and Activities, IAEA Safety Standards Series No. GS-R-3, IAEA, Vienna (2006). 2.INTERNATIONAL ATOMIC ENERGY AGENCY, Application of the Management System for Facilities and Activities, IAEA Safety Standards Series No. GS-G-3.1, IAEA, Vienna (2006). 9  SYSTEM: Responsible Nuclear Energy Program System Attributes ③ That balances: ② Through a: Responsible Nuclear Energy Program Under any condition/event (Real or hypothetical) ① Minimize risk to: Public Environment Infrastructure System Objective Utilize Nuclear Energy to improve standard of living 10  Introduction to Nuclear Safety Proposed Model for 3S Framework Recall our 3S Framework 3S Culture 3S Enabling Tools Model State and Apply the model Organizational Policies Technologies to Safety – Organizational replace “3S” Values and Processes with “Nuclear Commitment Knowledge Safety”; so we Individual and have Values and Commitment Experience 1) Safety Responsible Nuclear Energy Program Culture; 2) Safety Under any condition/event Enabling Under any (Real or condition/event hypothetical) (Real or hypothetical) Tools Minimize Risk to the: Public Environment Infrastructure 11  Safety Culture Per Our Model: Recall our Model for Creating a Balanced Integrated 3S Framework 12 12  Overview Safety Enabling Tools – Nuclear Safety Objectives – Safety Systems – Defense-in-Depth Concept – Safety Analysis – Records of Inventory and Location of Radioactive Material in the Nuclear Power Plant – Modeling of Dispersion of Radioactivity Releases 13  Safety Enabling Tools: Objectives of Nuclear Safety General Objective – To protect individuals, Nuclear Safety society and the Objectives environment from harm by establishing and maintaining, in nuclear General Complementary installations, effective Objective Objectives defenses against radiological hazards. Technical Safety Objective – Our model for Responsible Nuclear Energy Program (RNEP) is consistent with this objective Radiation Protection Objectives References: IAEA Safety of nuclear power plants: Design, NS-R-1, 31 October 2000. INTERNATIONAL ATOMIC ENERGY AGENCY, The Safety of Nuclear Installations, Safety Series No. 110, IAEA, Vienna (1993). 14  Safety Enabling Tools: Objectives of Nuclear Safety Technical Safety Objective: Nuclear Safety To take all reasonably practicable Objectives measures to prevent accidents and mitigate their consequences General Complementary To ensure with a high level of Objective Objectives confidence that any radiological consequences would be minor and below prescribed limits Technical Safety Objective To ensure that the likelihood of accidents with serious radiological consequences is extremely low. Radiation Protection Objectives References: IAEA Safety of nuclear power plants: Design, NS-R-1, 31, October 2000. INTERNATIONAL ATOMIC ENERGY AGENCY, The Safety of Nuclear Installations, Safety Series No. 110, IAEA, Vienna (1993). 15  Safety Enabling Tools: Objectives of Nuclear Safety Radiation Protection Objective: Nuclear Safety To ensure radiation exposure is kept Objectives below prescribed limits and as low as reasonably achievable; General Complementary To ensure mitigation of the Objective Objectives radiological consequences of any accidents. Technical Safety Objective Must Protect: – Workers (Personnel) – Environment Radiation Protection – Public Objectives References: IAEA Safety of nuclear power plants: Design, NS-R-1, 31 October 2000. INTERNATIONAL ATOMIC ENERGY AGENCY, The Safety of Nuclear Installations, Safety Series No. 110, IAEA, Vienna (1993). 16  Safety Enabling Tools: Safety Systems and Their Functions Included in the design, construction, and operation of the nuclear power plant (NPP) Can be a part of requirements both for operation of the reactor AND also for meeting the safety objectives – all three objectives Designed to cope with a set of accidental events (design basis accidents, or DBA) 17  Safety Enabling Tools: Safety Systems and Their Functions Three main objectives (1st): – Quick shutdown of chain reaction Control rods Insertion of neutron “poison” Ref. Tong and Weisman, Thermal Analysis of Pressurized Water Reactors, 3rd ed., 1996. 18  Safety Enabling Tools: Safety Systems and Their Functions Three main objectives (2nd): – Emergency cooling of the reactor after shutdown Remove the “decay” heat Emergency Core Cooling Systems (ECCS - Both Passive and Active ) 19  Safety Enabling Tools: Safety Systems and Their Functions Three main objectives (3rd): Primary Containment Steel Wall – Containment of radioactive products after accidental release from the reactor Combination of special Pressure buildings and engineered Boundary systems – “double containment” – negative pressure between primary and secondary containment – Isolation valves; – cooling and water Secondary spray systems, etc. Containment 20  Safety Enabling Tools: Defense-in-Depth (DID) in Nuclear Safety Defense-in-Depth (DID) concept – Provide multiple independent protections against the occurrence of accidents and their progression – Ensure that should one of them fail, at least another is present whose failure is independent from the operation of the first. “Independence” of barriers is only an objective – In reality, not always possible in every conceivable accident sequence. Reference: Nuclear Safety by Gianni Petrangeli, First Edition 2006; Required textbook for Weeks 7 and 8. IAEA TECDOC Implementation of Defence (Defense) in Depth for next generation light water reactors, No. 986, 21 November 1997. IAEA TECDOC Defence in Depth in nuclear safety, No. 10, 26 September 1996. IAEA INSAG Basic safety principles for nuclear power plants, 75-INSAG-3 Rev. 1, No. 12, 7 December 1999. 21  Safety Enabling Tools Defense-in-Depth in Nuclear Safety Defense-in-Depth is a “general defense principle”, which is – Implemented to the maximum technically feasible degree, and – Provides a ‘graded’ protection against a vast variety of: transients abnormal events and accidents – malfunction of components – human errors in the plant – events initiated externally 22  Safety Enabling Tools Defense-in-Depth in Nuclear Safety Defense-in-Depth is based on four principal barriers against the external release of radioactive products – fuel matrix – fuel cladding – reactor cooling circuit pressure boundary – containment system and on five defense levels in order to best use these barriers.* * IAEA TECDOC Implementation of Defence (Defense) in Depth for next generation light water reactors, No. 986, 21 November 1997. 23  Safety Enabling Tools: Defense-in-Depth in Nuclear Safety Secondary Containment Steel Wall Site Boundary Pressure Clad Boundary Population Distance Pellet 24 24  Safety Enabling Tools: Defense-in-Depth in Nuclear Safety Defense Objective Essential means level Level 1 Conservative design and high Prevention of abnormal operation quality of construction and of and of malfunctions. operation. Level 2 Control, limitation and protection Control of abnormal operation systems and other surveillance and detection of malfunctions. characteristics. Level 3 Control of accidents included in Engineered safety systems and the design basis. accident procedures. Level 4 Control of the severe accident conditions of the plant, including Additional measures and accident the prevention of accident management. progression and mitigation of consequences. Level 5 Mitigation of the radiological consequences of significant External site emergency plan. releases of radioactive products. Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) * IAEA TECDOC Implementation of Defence (Defense) in Depth for next generation light water 25 reactors, No. 986, 21 November 1997.  Safety Enabling Tools: Safety Analysis Objectives of Safety Analysis: – Help define and to confirm, through adequate analysis tools, the safety “basis” for the parts of the plant which are important for Event Tree safety – Ensure that the general design of the plant is capable of complying with the dose limits in force and with the radioactive releases specified for any plant conditions Fault Tree IAEA Safety Assessment and verification for Nuclear Power Plants, NS-G-1.2, 28 January 2002. Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module 26 of GNEII.)  Safety Enabling Tools: Safety Analysis Safety Analysis Used in Licensing: – Should proceed in parallel with the design – to continue to comply with dose limits for radioactive releases – Must be kept up to date during the life of the plant in order to account for the progress of knowledge and in case of plant or site modifications IAEA Safety Assessment and verification for Nuclear Power Plants, NS-G-1.2, 28 January 2002. Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 27  Safety Enabling Tools: Safety Analysis Deterministic Safety Analysis Approach: – Studies the behavior of the plant in operational states and under specific accident conditions or for compliance with the chosen criteria. – Usually uses conservative assumptions on input data, intermediate parameters for the analyses and on the behavior of plant systems (single failure, etc.). – Severe accidents are also part of the deterministic analyses; Very low probability Conservative assumptions used for DBAs are not used for severe accident analysis. “Best estimate” treatment of the phenomena is preferred. IAEA Safety Assessment and verification for Nuclear Power Plants, NS-G-1.2, 28 January 2002. Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module 28 of GNEII.)  Safety Enabling Tools: Safety Analysis Probabilistic Safety Analysis (PSA): – Has become common practice for new plants and for existing ones International requirements include that safety analysis reports include a summary of the PSA study of the plant – Is a complete and well-structured method for identifying accident scenarios and obtaining numerical risk estimates. – Use to demonstrate the compliance with numerical safety criteria is not advisable because of the uncertainties in methods, in data and, therefore, in their results – there is still a debate. IAEA Safety Assessment and verification for Nuclear Power Plants, NS-G-1.2, 28 January 2002. Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module 29 of GNEII.)  Safety Enabling Tools: Safety Analysis Probabilistic Safety Analysis (PSA): – Benefits of PSA: It forces the analyst to examine the complete set of possible sequences of events which may occur in a plant, without excluding any of them before-hand (as is done in the deterministic method); It affords a general vision of the plant from the safety point of view, highlighting specific weak points and, therefore, in particular during the design phase, allowing a well-balanced plant design to be conceived; The method gives an idea of the global risk and is useful for comparative considerations between different plants and, therefore, it contributes to the creation of a homogeneous reactor overview from the point of view of risk. IAEA Safety Assessment and verification for Nuclear Power Plants, NS-G-1.2, 28 January 2002. Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module 30 of GNEII.)  Safety Enabling Tools: Safety Analysis Probabilistic Safety Analysis (PSA): – PSA detects weak points of the plant where the normal design process had not been able to reveal weaknesses. – Probabilistic analyses are applicable to Levels 1, 2 or 3 (IAEA, 1992, 1995, 1996), because they examine the events up to core damage, up to the evaluation of radioactivity releases from the plant, or up to the external radiological consequences – The present trend for the support of plant safety decisions, involves a “blended approach” for safety analysis, including both deterministic and probabilistic. IAEA Safety Assessment and verification for Nuclear Power Plants, NS-G-1.2, 28 January 2002. Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 31  Safety Enabling Tools: Safety Analysis Event Tree: – A branched graph showing the possible sequences of plant events following the good operation or malfunction of safety systems. – Identifies the various final plant Event Tree situations, and the associated overall probabilities. IAEA Safety Assessment and verification for Nuclear Power Plants, NS-G-1.2, 28 January 2002. Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 32  Safety Enabling Tools: Safety Analysis Fault Tree: — Unlike the event trees, proceed backward from the final event (i.e. the fault of the component or system) to the various causes which may have originated it, with the corresponding probabilities. — Generally use Boolean algebra (the algebra of binary systems: 1s and 0s) - leads to the maximum simplification of the fault tree. Fault Tree IAEA Safety Assessment and verification for Nuclear Power Plants, NS-G-1.2, 28 January 2002. Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module 33 of GNEII.)  Safety Enabling Tools: Inventory and Location of Radioactive Material in the Nuclear Power Plant Location of radioactive material: – Almost all radionuclides are contained in the fuel: In the reactor core; In used fuel stored at the plant – Spent fuel pool – Dry storage containers for temporary storage Source: https://en.wikipedia.org/wiki/Dry_cask_ storage#/media/File:Nuclear_dry_storage.jpg IAEA Safety Assessment and verification for Nuclear Power Plants, NS-G-1.2, 28 January 2002. Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 34  Safety Enabling Tools: Inventory and Location of Radioactive Material in the Nuclear Power Plant Partial list of radionuclide inventory in a 1000 MWe PWR in equilibrium conditions (for certain operation time and condition) Half- Radioactivity Half- Radioactivity Nuclide life (Bq × Nuclide life (Bq × (MCi) (MCi) (days) 1018) (days) 1018) 85Kr 3950 2.072 56 86Rb 18.7 0.00096 0.026 85mKr 0.183 0.888 24 127Te 0.391 0.2183 5.9 87Kr 0.0528 1.739 47 127mTe 109 0.0407 1.1 88Kr 0.117 2.516 68 129Te 0.048 1.147 31 133Xe 5.28 6.29 170 129mTe 0.34 0.1961 5.3 135Xe 0.384 1.258 34 131mTe 1.25 0.481 13 131I 8.05 3.145 85 132Te 3.25 4.44 120 132I 0.0958 4.44 120 127Sb 3.88 0.2257 6.1 133I 0.875 6.29 170 129Sb 0.179 1.221 33 134I 0.0366 7.03 190 89Sr 52.1 3.478 94 135I 0.28 5.55 150 90Sr 11 030 0.1369 3.7 134Cs 750 0.2775 7.5 91Sr 0.403 4.07 110 136Cs 13 0.111 3 140Ba 12.8 5.92 160 137Cs 11 000 0.1739 4.7 Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 35  Safety Enabling Tools: Inventory and Location of Radioactive Material in the Nuclear Power Plant Partial list of radionuclide inventory in a 1000 MWe PWR in equilibrium conditions (for certain operation time and condition) Half- Radioactivity Half- Radioactivity Nuclide life (Bq × Nuclide life (MCi) (Bq × 1018) (MCi) (days) 1018) (days) 58Co 71 0.02886 0.78 141Ce 32.3 5.55 150 60Co 1920 0.01073 0.29 143Ce 1.38 4.81 130 99Mo 2.8 5.92 160 144Ce 284 3.145 85 99mTc 0.25 5.18 140 143Pr 13.7 4.81 130 103Ru 39.5 4.07 110 147Nd 11.1 2.22 60 105Ru 0.185 2.664 72 239Np 2.35 60.68 1640 106Ru 366 0.925 25 32 500 0.002109 0.057 105Ru 1.5 1.813 49 239Pu 8.9 × 0.000777 0.021 90Y 2.67 0.1443 3.9 106 91Y 59 4.44 120 240Pu 2.4 × 0.000777 0.021 95Zr 106 65.2 5.55 150 241Pu 5350 0.1258 3.4 97Zr 0.71 5.55 150 95Nb 241Am 1.5 × 0.0000629 0.0017 35 5.55 150 105 140La 1.67 5.92 160 Total activity Total activity (MCi) 5202 TOTAL (EBq) 193 Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 36  Safety Enabling Tools: Modeling Dispersion of Radioactivity Releases Three steps in the evaluation of the “consequences” of accidents: – Evaluation of the releases (the ‘source term; amount, chemical–physical form, trend with time). – Evaluation of the dispersion of releases in the environment. – Evaluation of the health consequences. 37  Safety Enabling Tools: Modeling Dispersion of Radioactivity Releases Objectives of Dispersion Modeling – Gaseous releases Most relevant for – the evaluation of the immediate accident consequences – the preparation of short-term emergency plans – Solid and liquid releases Less of concern for off-site environmental impact Important for on-site impact (workers and structure contamination) – Hence, dispersion modeling focuses on gaseous releases Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 38  Safety Enabling Tools: Modeling Dispersion of Radioactivity Releases Example of Plume Types Perspectives on Reactor Safety, NUREG/CR-6042, Rev. 2, SAND 93-0971, 2002, http://www.nrc.gov/reading-rm/doc-collections/nuregs/contract/cr6042/ (p. 39 5.1-16)  Safety Enabling Tools: Modeling Dispersion of Radioactivity Releases Modes of dispersion – Dispersion of a light cloud in the environment occurs by diffusion, generally in a turbulent regime – Dispersion of a heavy cloud occurs Firstly, by fall and gravitational spread Secondly, at a certain distance from the source, the heavy cloud is also dispersed by diffusion – Two parameters have an overwhelming influence on the atmospheric dispersion: The wind speed; The vertical thermal gradient (i.e. the change of temperature with height). Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 40  Safety Enabling Tools: Modeling Dispersion of Radioactivity Releases Dispersion Modeling: – Gaussian theory of diffusion is most commonly used – Dispersion is a function of: Wind speed Standard deviation of the Gaussian distribution Height of release Position of a point in space with reference to the Diffusion plume for (a) ground and release point (b) elevated release from a chimney Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 41  Safety Enabling Tools: Design Basis Accident (DBA) DBAs are accidents which the plant must be able to override and maintain a safe state. Usually, A DBA for a PWR is a complete break of a Cold Leg. A DBA for a BWR is a complete break of a Main Steam Line. http://www.nrc.gov /reactors/pwrs.html 42  Safety Enabling Tools: Design Basis Accident (DBA) Some Important Data for Accident Analysis – Initial conditions – Doppler coefficient – Coefficient of moderator temperature and of the voids – Reactivity of the boron content (content of boron in the cooling water) – Reactivity of the control rods – Reactivity of fission products (xenon and samarium) Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 43  Safety Enabling Tools: Design Basis Accident Additional considerations include: – Spurious opening of a pressurizer safety valve – Instantaneous power loss to all the primary pumps – Sudden expulsion of a control rod from the core – Break of the largest pipe of the primary system (large Loss of Cooling Accident (LOCA) – Fuel handling accident – Area accidents Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 44  Safety Enabling Tools: Beyond Design Basis Accident BDBAs have a low probability of occurrence Their margins of safety are rather smaller than those adopted for DBAs They are dealt with using specific prevention and mitigation measures Important examples are: – Transients without scram (ATWS – anticipated transients without scram); and – Total loss of external and internal electric power supplies (station blackout). Nuclear Safety; By Gianni Petrangeli, Copyright Gianni Petrangeli © 2006, Publisher: Elsevier Science and Technology Books, Inc. (The required textbook for this Module of GNEII.) 45  References Enrico Fermi Image Gallery, The University of Chicago Library Digital Activities & Collections, http://fermi.lib.uchicago.edu/fermiimages.htm Nero, Anthony V., A Guidebook to Nuclear Reactors, University of California Press, Berkeley, 1979. Tong, L. S., and J. Weisman, Thermal Analysis of Pressurized Water Reactors, 3rd ed., 1996. General Electric Company, BWR/6 General Description of a Boiling Water Reactor, 1980. The Westinghouse Pressurized Water Reactor Nuclear Power Plant, Westinghouse Electric Co. LLC, Pittsburgh, PA (2006) Perspectives on Reactor Safety, NUREG/CR-6042, Rev. 2, SAND 93-0971, 2002, http://www.nrc.gov/reading-rm/doc-collections/nuregs/contract/cr6042/ PWR Safety Systems Protection – RPS Setpoints, from Bill Burchill’s NUEN 609 lecture notes, 2005 Nuclear Safety Criteria for the Design of Stationary Pressurized Water Reactor Plants, ANSI/ANS-51.1-1983 10 CFR Appendix A to Part 50—General Design Criteria for Nuclear Power Plants, US NRC, http://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050- appa.html#6_appa 10 CFR Appendix I to Part 50 - —Numerical Guides for Design Objectives and Limiting Conditions for Operation to Meet the Criterion "As Low as is Reasonably Achievable" for Radioactive Material in Light-Water-Cooled Nuclear Power Reactor Effluents, US NRC, http://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-appi.html 46