Safety goals according to the safety requirements for nuclear power plants in Germany

Transcription

1 Safety goals according to the safety requirements for nuclear power plants in Germany H. P. Berg Bundesamt für Strahlenschutz (BfS), Willy-Brandt-Str. 5, Salzgitter IAEA Technical Meeting on Development of a TECDOC on Development and Application of a Safety Goals Framework for Nuclear Installations Vienna, July 8 12,

2 Content of the presentation Introduction Safety requirements for nuclear power plants Safety goals in German regulations Application of the safety goals framework Concluding remarks 2

3 Introduction (1) The catastrophic event in Fukushima, Japan, on March 11, 2011, strongly influenced the public opinion for an earlier phase-out of nuclear energy production in Germany. The Federal Government and the Minister-Presidents of the Federal States decided to subject all Germany s nuclear power plants to a plant-safety review. This specific safety review had to be performed until June 2011 under the leadership of the German Reactor Safety Commission. Besides, the seven oldest German nuclear power plants, which started their operation before the end of 1980, have immediately been taken off the grid for three months. At that time, 17 nuclear power plants (11 PWR and 6 BWR) were licensed for operation in Germany. 3

4 Introduction (2) A catalogue of requirements to be investigated within this plant-specific safety review has been issued by the German Reactor Safety Commission on March, 30, 2011, requiring that measures and installations have to be available to avoid events and failures (first and overriding principle) and to control accidents (second principle). This review has been performed within two months. 4

5 Introduction (3) The German government decided to phase out the use of nuclear power for commercial generation of electricity in Germany at the earliest date possible. The decision takes into account basically both the outcome of the deliberations in the Ethics Commission on a Secure Energy Supply set up by the government and the safety reviews of all German nuclear power plants by the Reactor Safety Commission. 5

6 Introduction (4) No No Name Abbrev. Reactor type Power MWe (gross) Power MWe (gross) In commercial operation since Shut- down date according to the Atomic Energy Act as of 31 July Neckarwestheim-1 GKN 1 PWR Philippsburg-1 KKP 1sd BWR Isar-1 KKI 1 BWR Biblis-A KWB A PWR Biblis-B KWB B PWR Unterweser KKU PWR Brunsbüttel KKB BWR Krümmel KKK BWR Grafenrheinfeld KKG PWR Gundremmingen-B KRB-II-B BWR Philippsburg-2 KKP 2 PWR Gundremmingen-C KRB-II-C BWR Grohnde KWG PWR Brokdorf KBR PWR Neckarwestheim-2 GKN 2 PWR Isar-2 KKI 2 PWR Emsland KKE PWR Total Power

7 Introduction (5) In the past, the safety concept of nuclear power plants as well as licensing decisions were mainly based on deterministic principles, such as safety features to prevent or control anticipated operation conditions and incidents, passive barriers against radioactivity releases in case of an incident, redundancy and diversity of safety systems to ensure high reliability. 7

8 Introduction (6) It is the overall requirement to perform a probabilistic safety assessment essentially in the framework of the Periodic Safety Reviews mainly as a supplement to the deterministic safety analysis. The main objectives are to check the overall safety level of the plant and analyse if the engineered safety features designed to cope with safety relevant incidents are well balanced. The evaluation has to be performed taking into consideration quantitative as well as qualitative results of the analysis. Currently, no specific probabilistic quantitative safety goals are determined; however, the authorities and their expert groups have to assess also the quantitative results of PSA provided in the frame of (periodic) safety reviews as in the past. 8

9 Introduction (7) The recently issued German safety requirements for nuclear power plants expand the use of probabilistic safety assessment complementary to deterministic safety demonstrations to assess the safety significance in case of modifications of measures, equipment or the operating mode of the plant, as well as of findings that have become known from safety-relevant events or phenomena that have occurred and which can be applied to the nuclear power plants in Germany that are referred to in the scope of application of the "Safety Requirements for Nuclear Power Plants" for which a significant influence of the results of the PSA can be expected. 9

10 German regulatory framework Federal Legislator Federal Government, Federal Council Basic Law Atomic Energy Act Ordinances General administrative provisions generally binding binding for authorities Federal Government, Länder authorities Advisory bodies KTA Industry BMU publications - Safety requirements for nuclear power plant - Guidelines and recommendations RSK guidelines, RSK and SSK recommendations KTA safety standards Technical specifications for components and systems Organisation and operating manuals binding by specification in the licence and/or by supervisory decision in the individual case 10

11 German Safety Requirements for Nuclear Power Plants (1) 15 years ago it was decided to develop a modern consistent regulatory framework including actual topics like safety management, digital I&C etc. Moreover, the application of defence in depth should be addressed in more detail and more systematically. These activities resulted in an iterative process in the latest document entitled Safety Requirements for Nuclear Power Plants. 11

12 German Safety Requirements for Nuclear Power Plants (2) The document entitled Safety Requirements for Nuclear Power Plants contains of a main part and the following five annexes: Annex 1: Annex 2: Annex 3: Annex 4: Annex 5: Terms and definitions, Events to be considered, Requirements for the protections against internal and external hazards as well as very rare man-made external hazards, Principles for applying the single failure criterion and the maintenance, Requirements for safety demonstration and documentation. 12

13 Defence in depth concept as applied in Germany For the safe confinement of the radioactive materials in the nuclear power plant, a defence-in-depth safety concept is realised. Level of defence 1: normal operation Level of defence 2: anticipated operation occurrences Level of defence 3: accidents Level of defence 4a: very rare events Level of defence 4b: events involving multiple failure of safety equipment Level of defence 4c: accidents involving severe fuel assembly damages 13

14 German Safety Requirements for Nuclear Power Plants (2) Hazards, which are relevant concerning their radiological impacts and against which precautions must be taken in terms of engineered safeguards or countermeasures are also defined in the Safety Requirements. 14

15 High-level safety goals in Germany In the German Atomic Energy Act it is stated that the aim of the act is to protect life, health and real assets against the hazards of nuclear energy and the harmful effects of ionising radiation and to provide compensation for damage and injuries caused by nuclear energy or ionising radiation. The fundamental safety goal described in the Radiation Protection Ordinance is the protection of man and environment against the harmful effects of ionising radiation. 15

16 Hierarchy of safety goals (1) Primary safety goal: To protect people and the environment from harmful effects of ionizing radiation Upper level safety goal: Ensuring adequate protection in all operational modes of the nuclear power plants as well as of the facilities and installations at a site Examples: To protect workers, the public and the environment Any early or large releases into the environment of the plant and their radiological consequences should be limited to a limited spatial and temporal extent 16

17 Hierarchy of safety goals (2) Intermediate level safety goals O1 Q1: O1 D1: A1 Q1: A1 D1: A1 D3: A2 P1: Integrated Management system, leadership and safety culture Meeting radiological criteria for workers by providing adequate radiation protection measures Maintaining effective defence-in-depth Maintaining allowed doses for workers in DBAs Containment withstanding an aircraft crash according to a specified impact-load-time diagram Intervention reference levels for sheltering and evacuation 17

18 Hierarchy of safety goals (3) Typical examples of deterministic low level safety goals which have to be fulfilled are No critical boiling at cladding tube or maintaining of an appropriate temperature-time criterion of the cladding tube, Cladding tube temperature < 1200 C, Amount of shutdown reactivity. Probabilistic low level safety goals are e.g. Plant modifications shall not lead to an increase of the actual core damage frequency evaluated 18

19 Concluding remarks (1) The definition of safety goals for nuclear installations, in particular nuclear power plants, is an important prerequisite for planning, constructing and operating these installations. These safety goals should consist of high-level and intermediate safety goals and should result in derived lower-level safety goals, both qualitative and quantitative. An international common determination of probabilistic safety goals would be helpful, but only in case that scope and quality of the PSAs are comparable. Moreover, keeping the quantitative values should not inhibit possible safety improvements in the future (dynamic precaution). 19

20 Concluding remarks (2) In case of introducing quantitative safety goals, it is important that they are chosen in an appropriate manner and that they are valid for all types of supervisory assessments (periodic safety review, evaluation of operational changes and assessment of safety improvements in the frame of long-term safety) and decisions by the licensees. The hierarchy of safety goals as provided in Table 8 of the draft TECDOC is generally applicable for nuclear power plants in Germany. In Germany, one or two nuclear power plants are at one site, in some cases also an interim storage facility for high level waste. The separation into site-wide/technology-neutral and technologyspecific/installation-specific safety goals is in general a reasonable approach, but not fully implemented in Germany. However, the intervention reference levels for sheltering and evacuation are sitewide/technology-neutral. 20