Nuclear Safety

Garant předmětu:

Lecturer:

Tutor:

Supervisor:

Department of Nuclear Reactors

Synopsis:

Introduction: History and evolution of nuclear power plant safety. Classification of events, incidents, accidents, accident of US NPP TMI-2, accident of Chernobyl NPP. Basics of nuclear safety - legislative approach: safety principles of NPP, legislative frame of nuclear power plant safety, international requirements on NPP safety, defense-in-depth, safety culture, classification of NPP states and criteria of acceptance, safety analysis. Severe accidents of NPP with pressurized water reactors - engineering and physical approach: loss of coolant accident (LOCA), anticipated transient without scram (ATWS). Safety systems of modern NPP with pressurized water reactors: VVER, EPR, AP-1000.

The course consists of two parts: first is secured by prof. B. Heřmanský; the second one is secured by a group of external instructors from NRI and SONS coordinated by Z. Kříž (NRI). Instructors belong to notable experts in various fields of nuclear safety who works at least 30 years in the field, some of them have experience from international organizations- IAEA, NEA.

Requirements:

17ZAF, 17JARE, 17TER, 17DYR,17PRF

Syllabus of lectures:

1. Introductory lecture

Scope: 1 lecture

Role of the course within study-program, relationship to other courses, goals of the course. Issue of severe accidents with fuel meltdown. ALARA principle and issue of linearization of the radiation effects. Relationship of risks and costs in assuring safety. Evolution of safety philosophy.

2. Accident classification

Scope: 1 lecture

The importance of incidents and accidents classification. Classification of incidents and accidents according to engineering and physical aspects: I.- reactivity insertion accident , II.- loss of coolant accident, III.- heat removal accident, IV.- other accidents, V.- external effects. INES - International Nuclear Event Scale: seven levels, methods of incidents and accidents evaluation, examples of particular levels. List of initiating events for NPP accident analysis.

3. Accident of TMI-2 NPP

Scope: 1 lecture

Babcock-Wilcox reactors, their design and safety systems. A brief outline of the accident evolution and its immediate causes. The failure of the media and the failure of NPP information system. Technical aspects of the accident, time sequence of events, expected core damage, formation of hydrogen in the core, bubbles removal. Comparison with NPP Mülheim-Kärlich. Analysis of the accident evolution after ten years: reconstructed course of events and actual damage to the reactor. Conclusions and lessons learned.

4. Accident of Chernobyl NPP

Scope: 1 lecture

RBMK reactors, their design and safety systems. Advantages and disadvantages of channel-type reactor. Risks of RBMK reactors operation. The course of the accident and its immediate causes. The positive coefficient of reactivity and wrong design of the control rods. Additional analysis of the accident by an international expert group and new data on the causes of the accident. Corrective safety facilities. Sarcophagus construction and the current status. Consequences of the Chernobyl accident. Risks of further operation of the NPP with RBMK reactors. Can a similar accident occurs in an NPP with VVER reactor?

5. Basics of nuclear safety (legislative approach)

Scope: 2 lectures

Safety principles of nuclear power plants and the legislative framework for NPP safety: radiation protection, nuclear safety, physical protection, emergency preparedness. Atomic law, decree No. 195, European law and the use of nuclear energy. International requirements on projects of new nuclear power plants: IAEA Safety Standards Series, European Utility Requirements (EUR), WENRA association.

Safety analysis:

Classification of NPP states: Category I - normal operation, Cat II .- accidents with low frequency, Cat III .- rare accidents, Cat IV. - limiting accidents. Criteria of acceptance. Specific criteria of acceptance. ATWS. Limits and conditions for safe operation. Safety analysis: deterministic approach, probabilistic approach. Computational codes: verification and validation, experimental base (ISP), conservative approach, best estimate approach.

6. NPP defense-in-depth and safety culture

Scope: 1 lecture

Defence-in-depth principle. Basic physical barriers: fuel, cladding, primary loop pressure boundary, containment. Five levels of defense-in-depth: 1 - prevention of failure, 2 - systems for normal operation, 3 - safety systems, 4 - specialized safety systems, 5 - emergency plans. Gen. III reactors defense-in-depth. Safety culture: definition and nature, universal characteristics of safety culture, requirements on strategic level, safety culture indicators.

7. LOCA and severe accidents

Scope: 2 lectures

Phenomenological description of LBLOCA

Rupture of the main circulation piping on NPP with PWR (LBLOCA). Phenomenological description of the accident: blowdown, refill, reflood, and long-term core cooling. Fuel behavior during the accident. Specific LOCA criteria of acceptance. Analysis of LBLOCA for NPP Temelin. Calculation codes for LOCA analysis. New (probabilistic) approach to evaluation of safety analysis outcomes.

Serious NPP accident with fuel meltdown

High- and low- pressure sequence of serious accident with fuel meltdown. Phenomenological description of a typical low-pressure sequence. Processes inside reactor vessel melt-through, interaction of corium with concrete, processes inside containment. Examples of hypothetical accidents leading to low-pressure sequence.

8. Safety systems of NPP

Scope: 3 lectures

Safety systems of NPP with VVER reactors

Safety features of pressurized water reactors. Trends in safety systems of NPP with PWR. Evolution of safety systems of NPP with VVER reactors: specifics of NPP with VVER reactors evolution, VVER-440 /V-230 systems, Finnish NPP Loviisa, NPP with VVER-440 of the second Generation (V213), barbotage condenser system, further evolution of VVER safety systems. NPP Temelin safety systems: design, engineering and technological part, electrical part, I&C, construction part (containment). Safety systems of NPP with VVER of the III. generation.

Safety systems of gen. III NPP: EPR

Safety requirements on gen. III NPP (EUR). Safety systems of the European Pressurized-Water Reactor (EPR): basic characteristics, layout, safety concept, defense-in-depth. EPR safety systems.

Safety systems of gen. III NPP: AP-1000

Active and passive safety systems. Safety systems of US PWR AP-1000: basic characteristics, layout, safety concept, defense-in-depth. AP-1000 safety systems.

9. Nuclear safeguards (Z. Kříž)

Scope: 1 lecture

Surveillance as a necessary part of infrastructure, role of government, requirements on surveillance (independence, competence, financial security, etc.), main areas of evaluation activities, inspections, requirements, decisions, IAEA recommendations, historical trends and situation in the world and in Czech Republic - SONS

10. Approval process for nuclear facilities (J. Dušek)

Scope: 1 lecture

Main stages of approval process (siting, construction, operation) according to Atomic Act, requirements on safety documentation content, safety analysis and acceptance criteria, approval process for changes (life extension, power increase)SONS decisions with conditions

11. Probabilistic safety assessment (J. Dušek)

Scope: 1 lecture

Deterministic/probabilistic assessment, PSA method, types of PSA (1 - 3), fault and event trees, acceptance criteria, practical use of PSA (changes assessment, risk monitoring, risk -informed procedures

12.Nuclear fuel safty (M. Hrehor)

Scope: 1 lecture

Nuclear fuel requirements (standard operation, transients, accidents (LOCA), acceptance criteria (evolution, differences) and their verification, higher enrichment and higher burn-up impact

13. Research for safety (M. Gregor)

Scope: 1 lecture

National and international research programs (NEA, EU projects), safety research need, research topics (transients, materials, fuel, human factor), experiences and benefits for Czech nuclear programme

14. Personel in nuclear facilities (J. Egermayer)

Scope: 1 lecture

Research and experience with NPP personnel, requirements on personnel ( SONS edict no. 315/2002 Sb.), selected personnel, qualification verification of personnel - licenses (professional, health, psychological), practical experience

15. Principles for ensuring safety (A. Miasnikov)

Scope: 2 lectures

Basic principles for ensuring the fuel and core safety, their practical applications, requirements on material, construction, degradation mechanisms and reducing of their impact

16. Radioactive wastes (K. Jindřich)

Scope: 1 lecture

Basic principles - minimization, processing and storage of RA waste, waste types in term of state of matter, activity, hazardousness, radioactive waste repository, system of barriers, state conception for radioactive waste processing, present state and perspectives in Czech Republic

16.Utilizing of operational experience (Z. Kříž)

Scope: 2 lectures

Importance of operational experiences utilizing (events, accidents) for safety, requirements on experience utilizing system, main process stages (collection, analysis, causes, corrective actions, lessons learned), national and international experience exchange systems (IRS, WANO), practical example of NPP event analysis

Syllabus of tutorials:

-

Study Objective:

Orientation in classification and evolution of events, incidents and accidents of NPP. Detailed knowledge of causes, evolution and consequences of the two largest NPP accidents (TMI, Chernobyl). Knowledge of nuclear safety basics. Overview of NPP safety systems and their resistance against potential incidents and accidents.

Orientation in given issue, understanding of serious accident importance for nuclear power global safety. Overview of issues in assuring safety of gen. II (current NPPs) and gen. III (new nuclear source) NPPs.

Study materials:

Key references:

Heřmanský B.: „Nuclear reactor safety I., II., III., IV.“ Textbooks, 2009,

(in Czech)

Recommended references:

„Basic Safety Principles for NPP“, Rev.1. INSAG-12 report, IAEAVienna 1999

„European Utlities Safety Requirements“, Vol.1, Rev. C, state 5, April 2001

„Accident Analysis for Nuclear Power Plants“, IAEA, Vienna, December 2002

Note:

Further information:

No time-table has been prepared for this course

The course is a part of the following study plans: