TS1-5: Revision of NS-G-2.15 and Its Implementation for Verification and Validation of Severe Accident Management Guidelines

Transcription

1 Technical Meeting on Verification and Validation of Severe Accident Management Guidelines for Nuclear Power Plants December 2016, Vienna, Austria TS1-5: Revision of NS-G-2.15 and Its Implementation for Verification and Validation of Severe Accident Management Guidelines Man KIM Safety Assessment Section Korea Institute of Nuclear Safety A. Ulses, N. Hiranuma Safety Assessment Section International Atomic Energy Agency

2 Outline of the presentation 1. Revision of NS-G-2.15: SAMP for NPPs Background Need for revision Activities taken for Draft Document Activities and work plan 2 Verification and validation of severe accident management guidelines (SAMGs) Guideline of SAMG V/V Examples of MSs Concluding Remarks 2

3 1. Background SAMG was developed after Three Mile Island (TMI) accident in 1979 because EOPs were inadequate to enable operator success in controlling/preventing/mitigating accidents at nuclear power into significant core damage accidents. Reactor owners groups likely the Westinghouse Owners Group (WOG) had been developed severe accident management guidelines (SAMG) by between 1991 and 1994 to assist operators; - to recover from accident conditions; - to prevent failure of any containment fission product boundaries; and - to return the plant to a controlled stable condition. 3

4 1. Background (cont d) IAEA developed a Safety Standard NS-G-215 for severe accident management programme for NPP published in to provide guidance and recommendations for the development and implementation of an SAMP aimed at preventing and/or mitigating the consequences of accidents including combination of events, external hazards not considered in the design basis. 4

5 2. Need for revision Aftermath of Fukushima Daiichi accident (FDA) in 2011, there was recognition to re-examine the NS-G to include lessons learned from FDA because it showed gaps with lessons from FDA in maintaining an appropriate level of the guidelines. According to the IAEA action plan for nuclear safety, the pilot exercise to assess the impact of changes to safety requirements requested by CSS in 2012 was conducted. CSS: Commission of Safety Standards 5

6 Gap Analysis of Lessons Learned from Fukushima Daiichi Accident <Accident Progression> Prevention of prolonged loss of off-site power Enhancement of plant monitoring and control functions Loss of communication & instrumentation functions DG: Diesel Generator Earthquake Reactor shutdown Emergency DGs / core cooling systems started Tsunami Core damage Hydrogen explosion in reactor building Design basis height: 5.7m Inundation height: 15.5m <Countermeasures> Enhancement of robustness against earthquake and tsunami Prevention of core damage Enhancement of emergency power supply and core cooling Prevention of containment failure Suppression of release and dispersion of radioactive materials Release of large amount of radioactive materials to environment

7 3. Activities taken for Draft Safety Guide DS483 1 Pilot exercise results presented at the 35th NUSSC Meeting in Requested to initiate the revision of NS-G-2.15 to incorporate the relevant feedback from Fukushima- Daiichi accident 2 The revision of NS-G-2.15 was initiated in 2013 to provide a comprehensive guidelines on accident management programme for MSs. Main approach for Revision - Consistency with revisions of relevant safety requirements; SSR-2/1, SSR-2/2, GSR Part 4 and GSR Part 7 being incorporated lessons learned from FDA - Feedback of international consensus from IEM-7 on Severe Accident Management in the light of the accident at the Fukushima Daiichi NPP on March Relevant review Committees comment and MSs comments ( ) 7

8 3. Activities taken (cont d) 3 Approval of DPP (Step 1-4): - Preparation of DPP (2013) - NS Coordination Committee (April 2013) - Review committees: NUSSC, WASSC, RASSC, NSGC (October-November 2013) - CSS (April 2014) 4 Preparing the draft (Step 5): - CS in May-June 2013 (Belgium, Canada, France, Netherlands, UK, USA) - CS in January 2014 (France, Germany, ENISS) - CS in April 2014 (Canada, Czech, France, Japan, USA) - CS in October 2014 (Canada, Czech, France, Korea, UK, USA) - CS in February 2015 (Canada, France, Japan, UK, USA, ENISS) NS: IAEA Nuclear Safety Department CSS: Commission of Safety Standards CS: Consultancy Meeting 8

9 3. Activities taken (cont d) 1st Revision of draft DS483 including lessons learned from Fukushima Daiichi Accident - Storing flex components: potable/mobile pump, DG, - Equipment qualification - Transfer of responsibility - Reliable communication network - Decision making line and qualification of decision maker - Multi-unit sites : sharing TSC and assign an overall emergency director, sharing equipment - Failure of commend control due to a loss of MCR by large land damage. Etc. 9

10 4. Activities taken (cont d): Revised Structure 1. Introduction Background, objective, scope, structure 2. General Guidance for the AMP Requirements Concept of AMP Main principles Equipment upgrades Forms of accident management guidance Preventive domain Mitigatory domain Both preventive and mitigatory domains Roles and responsibilities 3. Development and implementation of an SAMP Technical bases Identification of challenge mechanisms Identification of plant vulnerabilities. Identification of plant capabilities Development of SAM strategies and guidelines AM strategies for severe accidents SAMGs SAM for multi-unit sites Hardware provisions for SAM for multi-unit sites Instrumentation and control for SAM Analyses for development of SAMG Staffing, qualification and working conditions for SAM staffing and qualification working conditions Responsibilities, lines of authorization and interface with EPR for SAM Responsibilities and lines of authorization. Transfer of responsibility and authority Technical support centre Interfaces with EPR For multi-unit sites Verification and validation of SAMP/SAMG SAM training, exercises and drills Updating SAMP/SAMG Management of SAMP/SAMG 4. Execution of SAMGs References ANNEX I Examples of SAMG Implementation France, Germany, USA, Japan 10

11 Findings from OSART Mission All mode of operation 1.9 The accident management programme needs to consider all initial modes of operation before the accident, including combinations of events and failures that could cause failure of fuel cooling and ultimately significant radiological releases to the environment. Spent Fuel This Safety Guide provides recommendations for the development and implementation of a severe accident management programme for a nuclear power plant, taking into account all possible fuel locations, particularly the reactor and the spent fuel pool. 11

12 Findings from OSART Mission Multi-unit For a multi-unit nuclear power plant site where several units are co-located, the accident management programme should consider concurrent severe accidents on multiple units. Personnel should have adequate skills for using such equipment and implementing supporting procedures and adequate multi-unit emergency organization staffing plans should be developed. Plans for defining staffing needs should take into account situations where multiple units on the same site have been affected simultaneously and some plant personnel have been temporarily or permanently incapacitated. In the case of multi-unit site with shared safety related equipment or systems, the continued use of a unit that has not been affected should be taken into account in the accident management guidance. Special care for exist plants should be used to identify impact on any equipment or systems that might be shared between units, in particular from the point of view of adequate capacity of the shared systems. 12

13 Findings from OSART Mission All phenomena (thermal-hydraulic, structural) important for assessment of challenges to integrity of barriers against releases of radioactive materials as well as for source term assessment should be addressed. Multi-unit accidents should be analysed where sites have more than one unit. Where equipment (including both permanent and non-permanent) is installed for use in severe accident management, there should be consideration that severe accidents can occur simultaneously on more than one unit. 13

14 3. Activities taken (cont d) 5 Approval of draft DS483 by the Coordination Committee in 2015 (Step 6) - NSNI QA review (March 2015) - IEC review for interface with EPR (April 2015) - NS Coordination Committee (CC) review (April 2015) - Most of comments are addressed for clarity, terminology, abbreviations, duplication, location, editorial correction and accepted to the revised documents. NSNI: IAEA Nuclear Installation Safety Division IEC: IAEA Incident and Emergency Centre 14

15 3. Activities taken (cont d) 6 Approval by the review Committees for submission to MSs in 2015 (Step 7): comments received from NUSSC, WASSC, RASSC and NSGC - Most comments focussed on clarification/improvement of paragraphs having about 66% of total comments and editorial improvement is about 31% - Most comments (about 99%) are incorporated to improve quality of the revised document. 15

16 3. Activities taken (cont d) 7 MS s Review comment in 2015 (Step 9): - Received 346 comments from 12 member states and 1 international organization (ENISS) and there are any significant comments. - Many of comments are duplicated and addressed to editorial correction and clarification to the paragraphs. - About 90% of comments are accepted to enhance clarification of the documents. 16

17 4 Activities and work plan 8 Second review of the draft safety standard DS483 by the SSC(s) in June Submission to SSCs - NUSSC, WASSC, RASSC, EPReSC, NSGC - for approval of sending CSS for publication endorsement. 9 Endorsement of the draft safety standard by the CSS in For endorsement of publication in

18 Outline of the presentation 1. Revision of NS-G-2.15: SAMP for NPPs Background Need for revision Activities taken for Draft Document Activities and work plan 2 Verification and validation of accident management guidelines (SAMGs) Guideline of SAMG V/V Examples of MSs 18

19 1. DS483: Verification and Validation of SAMG Objectives: Verification and validation processes should assess the technical accuracy and adequacy of the SAMGs to be extent possible, and the ability of personnel to follow and implement them. Scope All SAMGs should be verified and validated. The verification process should confirm the compatibility of SAMGs with referenced equipment, user aids and supplies (e.g. non-permanent equipment, posted job aids and materials for strategy evaluation. Changes made to guidelines and procedures should be re-evaluated and re-validated, on a periodic basis, to maintain the adequacy of the severe accident management programme. 19

20 1. DS 483: Verification and Validation of SAMG (cont d) Methods Possible methods for validation of the procedures and guidelines are an engineering simulator including a full scope simulator (if available) or other plant analysis tool, or a table-top method. The most appropriate method or combination of methods should be selected considering the role of each functional group of personnel in an emergency. If a full scope simulator is used, validation should encompass the uncertainties in the magnitude and timing of phenomena (both from the accident progression and from recovery actions). Consideration should be given to simulating a degraded or unavailable instrumentation response, or a delay in obtaining the information. 20

21 1. DS 483: Verification and Validation of SAMG (cont d) Conditions Validation should be performed under conditions that realistically simulate the conditions present during an emergency and include simulation of other response actions, hazardous work conditions, time constraints and stress. Special attention should be paid to the use of portable and mobile equipment for multiple unit sites, to the practicality of using backup equipment that could be provided by other units. Test All equipment necessary for SAMNGs, including non-permanent equipment, should be tested in accordance with the importance of the equipment to fulfilling the fundamental safety functions. 21

22 1. DS 483: Verification and Validation of SAMG (cont d) Test Guidance should be prepared for testing the permanent and nonpermanent equipment to meet its planned performance. Tests should address the necessary local actions, contingencies and the proper connection of the non-permanent equipment to plant equipment, access to the site, off-site actions, emergency lighting, and the time needed to implement these actions, the possibility of events affecting multiple units. Staff involved in the validation of the procedures and guidelines should be different from those who developed the procedures and guidelines. The frequency and type of testing should be conducted in accordance with the manufacturer s recommendations. Guidance should be provided for maintenance and periodic testing to ensure the proper functioning of equipment. 22

23 2. SRS-32: Implementation of Accident Management Programmes in Nuclear Power Plants Validation of SAMGs can be approached in various ways to define credible plant conditions. a) The general approach: tabletop exercises, use of simulators or plant analysers, exercises and drills. b) The supporting analysis needs: the methods used to provide them, codes to be used, possible use of scenario templates, etc. 23

24 Example 1: Use of full scope simulators: Natural circulation capacity during SBO (Korea) 24

25 Example 2: S/G Tube Rupture (Korea) SPTA: Standard Post-trip Action: Optimal Recovery Procedures (ORP) 25

26 Example 3: Full-Scope and Analytic Simulators for NPP s: JSC VNIIAES, (Russia Federation) During severe accident modeling an operator can watch and perform due management to prevent (or reduce damage) the following stages of severe accidents: primary circuit pipeline rupture and subsequent draining of reactor vessel; increase of temperature of fuel rod assemblies, fuel rod clad melting; fuel rod deformation, trickling of corium on the lower core support plate; heating, melt-through of lower core support plate, corium flowing to the bottom of reactor pit; heating, melt-through of reactor pit bottom, corium flowing to the bottom of reactor vessel; heating, melt-through of reactor vessel. 26

27 Example 4: Functional Demonstration of Electrical and I&C equipment for SA (Dr.-Ing. Peter Waber AREVA GmbH), Germany) 27

28 Example 5: Equipment Qualification Experience of Works at NPPs with VVER: All-Russian Research Institute for NPP Operation (JSC VNIIAES, Russia Federation) 28

29 Example 6: Mobile Equipment Used at the VVER NPP Units (Russia Federation) Mobile equipment for mitigation of Fukushima-type beyond design basis accidents: Mobile diesel-generator facility (MDGF) MDGF-2,0 MW: power supply for equipment needed for power supply for instrumentation, accumulator batteries etc. Mobile pumping facilities (MPF): MPF150/900 (for boric acid supply to primary circuit) ; MPF500/50 for water supply from motor pumps to consumers (service water) and/or water pumping from minus elevations; MPF150/120 for water supply to steam generators; MPF40/50 for boric acid supply to the spent fuel pool and/or water pumping from minus elevations. MPF: flow rate (m 3 /hour)/pressure (head, m) Referred from presentation of national research centre kurchatov institute» 29

30 Example 6: (cont d) 30

31 Concluding Remarks IAEA Safety Guide Series No. NS-G-2.15, Severe Accident Management Plan (SAMP) for Nuclear Power Plants (NPPs) was issued in 2009 aimed to giving guidance to provide setting up an accident management programme and how they should be executed to the plant operators. Aftermath of Fukushima Daiichi accident in 2011, there is recognition to reexamine the current NS-G-2.15 that is provided to guidelines of SAMP for nuclear power plants with lessons learned from Fukushima accident experience because it showed many gaps in maintaining an appropriate level of this guidelines. Therefore, the revision of NS-G-2.15, DS483, is developing to incorporate lessons of Fukushima Daiichi accident and new requirements in relevant requirement in GSR Part 4, SSR-2/1 and SSR-2/2 aimed to providing recommendations for the development of an accident management programme. This guideline will give guidance on how to conduct V/V of SAMP/SAMG for MSs. 31

32 End of Presentation Thank you for your attention! 32