Tecnatom Activities within the Framework of Long-Term Operation at Almaraz NPP

Transcription

1 1 Tecnatom Activities within the Framework of Long-Term Operation at Almaraz NPP M. Álvaro, M. Colomer (TEC) M. Baladía (CNAT) Fourth International Conference on Nuclear Power Plant Life October 2017, Lyon France

2 2 CONTENTS 1 Spanish Nuclear Power Plants Scenario Almaraz NPP: getting ready for LTO Resolution of Time-Limited Ageing Analyses EPRI MRP-227 Applicability Study 5 Conclusions

3 3 SPANISH NPP SCENARIO

4 4 Ageing of the Spanish Nuclear Power Plants Garoña BWR GE-3 X Ascó 1 PWR W Ascó 2 PWR W-3 Almaraz 1 PWR W Almaraz 2 PWR W-3 29 Trillo KWU Cofrentes BWR GE Vandellós II PWR W-3 We are turning 40 7 operational units. 5 over 30 years. 1 unit beginning its decommissioning. 20% generation is nuclear (2016 data). No plans for new build.

5 5 Nuclear Regulatory Framework in Spain The Spanish Regulatory Authority (CSN) develops the nuclear regulation in Spain. The CSN can also endorse standards from international organisations. Other regulations/standards come from the country where the technology was developed. Laws & Safety Instructions (IS) MANDATORY Generic Country of origin of technology Safety Guidelines (GS) GOOD PRACTICE Information Notices INFORMATION International Standards Technical Instructions (ITC) MANDATORY Plant Specific

6 6 Regulatory Requirements for Materials Ageing CSN Safety Guide, GS 1.10 Rev. 2: Periodic Safety Reviews (PSR) of nuclear power plants. CSN Safety Instruction, IS-22 Rev. 1: on safety requirements for ageing management and LTO of NPP, based on US NRC 10 CFR 54. General Licensing & Regulatory Aspects No legal lifetime limit for the Spanish NPP For each plant an Operating License is required and includes the due date for its renewal. All Spanish nuclear power plants have 40 years of lifetime. IS-22 Methodology based on NRC 10 CFR 54 to prepare the NPP license renewal applications. GS 1.10 Includes the need to develop and maintain updated plans of lifetime management.

7 7 ALMARAZ NPP: GETTING READY FOR LTO

8 8 Almaraz I and II: current situation NPP and Unit 1 st Connection to grid Next Periodic Safety Review LTO Required Documentation to CSN Updated Docum. to CSN Operating License validity up to Beginning of LTO (>40 years) Almaraz I th June 2017 March 2019 June Almaraz II th June 2017 March 2019 June Operating license renewal within the design life Part 1 Periodic Safety Review Operating Experience (OE) Review OE Analysis to Radiological Impact Regulatory Changes Analysis Equipment Performance Evaluation Design Modification Analysis Probabilistic Safety Analysis (PSA) Improvement and Safety Evaluation Programmes Part 2 New Regulation Analyses Cost benefit analysis for plan upgrading derived from new regulations analysis, proposed by the CSN

9 9 Operating license renewal after 40 years Part 1 Periodic Safety Review OE Review OE Analysis to Radiological Impact Regulatory Changes Analysis Equipment Performance Evaluation Design Modification Analysis Probabilistic Safety Analysis Improvement and Safety Evaluation Programmes Application for Long Term Operation Part 3 Ageing Evaluation and SSC Scoping and Screening Ageing Review Ageing Programme Time-Limited Ageing Analyses (TLAA) Part 2 New Regulation Analyses Cost benefit analysis for plan upgrading derived from new regulations analysis, proposed by the CSN Part 4 Radiological Impact Evaluation Updated Radiological Impact Report Waste Plan

10 10 Tecnatom activities related to LTO in Almaraz I and II One of the items required in the CSN Integrated Ageing & Evaluation Programme is the: identification, analysis and resolution of the Time-Limited Ageing Analyses. Within the Almaraz Lifetime Plant (LMP), an Ageing Programme (AMP) for the Reactor Vessel Internals (RVI) has already be defined. The CSN requires to include the MRP-227 and MRP-228 reactor vessel internals inspections: applicability study of MRP-227 to Almaraz NPP; design of a plant-specific inspection programme according to EPRI guidelines; based on economic and availability reasons.

11 11 RESOLUTION OF TLAA

12 12 Identification and resolution of TLAA in Almaraz NPP Those licensee calculations and analyses that: 1. Include systems, structures, and components (SSC) within the scope of ageing management. 2. Take into account the effects of time and the long-term operation. 3. Include assumptions based on a limited design life. 4. They conclude with the SSC availability or not, to continue operating, according to their functions defined, once the limited design life has been exceeded. 5. Were considered relevant in any safety assessment. 6. Are contained or incorporated by reference in the Current License Basis of the facility. The six criteria have to be satisfied to classify any analysis as a TLAA

13 13 Identification of TLAA in Almaraz NPP Preliminary screening: around 100 calculations identified as possible TLAA: Finally 39 analyses were classified as TLAA. 67% were related to METAL FATIGUE. 15% were related to REACTOR VESSEL NEUTRON EMBRITTLEMENT. 18% related to other issues.

14 14 Resolution of TLAA in Almaraz NPP Alternatives for TLAA resolution described in the IS-22: a) Verify that the analysis remains valid for the period of extended operation (60 years). b) Re evaluate the analysis for the period of extended operation and verify that the acceptance criteria are met. c) Demonstrate that the effects of ageing can be managed properly during the period of extended operation. 47% of the TLAA were solved directly by option a) 28% were solved by option b) 25% were solved by a combination of options a), b) and c)

15 15 Some conclusions of the neutron fluence TLAA EXTENDED BELTLINE (new materials to be included for the LTO) Inlet nozzles (95º, 215º and 335º) Upper shell to inlet nozzles welds Upper shell to 265º outlet nozzle weld Upper shell Upper shell longitudinal welds Upper to intermediate Shell welds Fluence threshold n/cm 2 (E>1MeV) defines the beltline zone TRADITIONAL BELTLINE Intermediate Shell Extended Beltline Traditional Beltline Lower shell Intermediate shell longitudinal welds 45º/225º Lower shell longitudinal welds 135º/315º Intermediate to lower Fourth shell International weld Conference on Nuclear Power Plant Life

16 16 EPRI MRP-227 APPLICABILITY STUDY

17 17 Applicability of MRP-227 in Almaraz I and II In the applicability study the following issues were taken into account: Scope and NDE inspection methods proposed in the guide. The material class of each functional component is as listed in MRP-191 (latest revision). 30 years of operation, as a base-loaded plant, with high-leakage core loading patterns followed by a low-leakage strategy for the remaining 30 years of operation (base-loaded). Effective Full Power Years (EFPY) of each Unit of Almaraz. Accessibility conditions for compliance with the requirements of MRP-228. Reactor Core Design CNA 1 CNA 2 High leakages Cycles 1 to 4 Cycles 1 and 2 Transition Cycles 5 to 7 Cycles 3 to 5 Low leakages Cycles 8 to 25 Cycles 6 to 24

18 18 MRP-227 Methodology Summary 8 age-related degradation mechanisms Stress corrosion cracking (SCC) Irradiation-assisted stress corrosion cracking (IASCC) Thermal ageing embrittlement Irradiation embrittlement Wear Fatigue Void swelling Irradiation-enhanced creep Categorize in 3 groups (FMECA) RVI placed into 4 functional groups A. Non-significant effects B. Moderately significant effects C. Potentially significant effects Primary Expansion Existing programmes No additional measures CRITICITY PRIMARY EXPANSION EXISTING PROGRAMMES NO ADDITIONAL MEASURES INSPECTION REQUIREMENTS (MRP-227)

19 19 Functionality Assessment Primary Components in Almaraz Almaraz NPP - Primary Components Alignment and Interfacing Components W8. Internals hold down spring Baffle-Former Assembly W6. Baffle-former bolts W7. Baffle and former plates W5. Baffle-edge bolts Control Rod Guide Tube Assembly W1. Guide plates W2. Lower flange welds Core Barrel Assembly W3. Upper flange Weld (UFW) Almaraz I and II 8 Primary 12 Expansion 6 Existing Programmes 6 No Additional Measures W4. Lower girth weld (LGW)

20 20 ISI Programme for Almaraz NPP based on MRP-227/228 Taking into account the following items: Prior visual inspections results of all the In-Service Inspections performed up to 04/2017. Coordination with the planned RVI extractions according to the ASME XI ISI Programme. Minimising the Critical Path during the refuelling outages. Operational Experience (OE) from USA fleet after application of MRP-227-A inspection requirements.

21 21 ISI Programme for Almaraz NPP based on MRP-227/228 Some of the advantages: All the inspections will be performed in two refuelling outages: AL1: R127 (April 2020) and R128 (October 2021) AL2: R226 (March 2021) and R227 (September 2022) MRP-227 inspections are finished prior to the beginning of LTO period (beyond 40 years). The core barrel extraction, required at the end of the 4 th interval, is used to perform the MRP-227 inspections. Human resources, time and economic costs are optimised.

22 22 CONCLUSIONS

23 23 Almaraz NPP is preparing its LTO by means of Submitting the AMP required by the CSN Identification, analysis and resolution of the TLAA for the extended period of operation. Almost half of the Almaraz TLAA remain valid for the period of extended operation. Designing a specific reactor vessel internals ISI Programme Based on the EPRI guidelines, MRP-227 and MRP-228. All the inspections will be performed in two refuelling outages before LTO period starts.

24 23-27 October 2017, Lyon France Marta Álvaro Marta Colomer Marta Baladía Tecnatom, S.A. Todos los derechos reservados. El contenido de esta obra está protegido por la Ley y no podrá ser reproducida, ni en todo ni en parte, ni transmitida, ni registrada por ningún sistema de recuperación de información, en ninguna forma ni por ningún medio, sin el consentimiento previo y por escrito de Tecnatom, S.A. y de sus autores. Tecnatom y el logotipo de Tecnatom son marcas registradas de Tecnatom, S.A.