FRENCH NUCLEAR PLANT LIFE MANAGEMENT STRATEGY REACTOR PRESSURE VESSEL ASSESSMENT

Transcription

1 FRENCH NUCLEAR PLANT LIFE MANAGEMENT STRATEGY REACTOR PRESSURE VESSEL ASSESSMENT AND STEAM GENERATORS LIFE MANAGEMENT STRATEGY. CONTENT REACTOR PRESSURE VESSEL PLIM STEAM GENERATORS STRATEGY vessel head SG SG pressurizer SG Georges BEZDIKIAN elbows primary pump confinement containment 1 /16

2 NUCLEAR PLANTS LIFE LIFE MANAGEMENT INTRODUCTION The capability of nuclear electricity generation by French Utility s (EDF Electricité de France) is 80% of global generation, 58 PWR units are in operation, 34 units three-loop, 20 units four-loop (1300MWe) and 4 units four-loop (1450MWe). The Status of Nuclear Plants Life Management is depending of the following objectives : To maintain current operating performances (safety, availability, costs, security, environment) in the long term, and possibly improve on some aspects ; wherever possible, to operate the units throughout their design lifetime, in other words 40 years, and after 40 years ; To consolidate Mormal and Exceptionnal Maintenance and long term Prediction. The Nuclear Plants Life Management Policy will take into account the category of the components and structure ; and strategic choices in relation with prediction of Aging Management 2 /16

3 REACTOR PRESSURE VESSEL LIFE MANAGEMENT AT FRENCH PWR PLANTS PWR in FRANCE. FLAMANVILLE PALUEL 4 units GRAVELINES 6 units PENLY. PARIS NOGENT-sur-SEINE DAMPIERRE 4 units CHOOZ CATTENOM 4 units SAINT-LAURENT CHINON 4 units CIVAUX LE BLAYAIS 4 units GOLFECH TRICASTIN 4 units FESSENHEIM BELLEVILLE LE BUGEY 4 units SAINT-ALBAN CRUAS 4 units 900 MW unit (34) 1300 MW unit (20) 1450 MW unit (2) (4) 3 /16

4 REACTOR PRESSURE VESSEL INTEGRITY ASSESSMENT The lifetime of a nuclear power plant may be affected by three main factors : normal wear of its components and systems - called aging - that depends particularly on their age, operating conditions and maintenance conditions applied to them ; the safety level, that must consistently comply with the safety requirements applicable to the power stations at all times, and which could change as a function of new regulations ; competitiveness, which must remain satisfactory compared with the competitiveness of other production means. The general strategy is based on the following two points : the ten-year safety reassessment process for each ten years period PSR, the implementation of two structured programmes in order to make sure that all technical and industrial actions necessary to achieve a lifetime of at least 40 years are actually implemented. 4 /16

5 . Reactor coolant fluid PTS Integrity Analysis Calculation Safety Injection Fluid Cladding Neutron Core zone Neutron Action on Vessel Wall and Degradation mode under irradiation Defect Defect postulated Core zone Inspected 5 /16

6 EVALUATION APPROACHES CARRIED OUT SPECIFIC VESSEL by VESSEL EVALUATION. Results of irradiation surveillance program A Initial RT NDT + RTNDT during operating lifetime RT NDT 30 years 40 years 50 years Chemical composition parameters for each vessel prediction Formula Fluence reduce -15 % irradiation during operating lifetime Size of defect postulated at the maximum fluence situation or Results of in service inspection RT NDT values comparison B Margins of code criteria for in operation units Thermal-hydraulic & Mechanical Analysis RT NDT of each vessel Results of transients analyses and most severe transient 6 /16

7 Assessment of RPV integrity : fluence calculations at EDF Level A = 2nd category of situation => Sc =2 level C = 3rd category of situation => Sc = 1.6 Level D = 4th category of situation => Sc = 1.2 Cladding Defect Defect fluid temperature time Transient Fluence Toughness initial properties of steel BRITTLE Initial transition temperature DUCTILE Temperature of the vessel steel T(x,t) and σ (x,t) distribution Stress intensity factor K CP - computation at crack tips Toughness K 1C - computation at crack tips KCP = KI plastic correction Margin factor K CP / K Ic 7 /16

8 2 - FLUENCE FIGURE 3 : PROJECTIONS DE FLUENCE A 40 ANS. Fluence en n/cm Years Fluence fluence de Basic conception Design Fluence fluence updated réactualisée 15 à years 15 ans of projection de fluence - 20 % of projection de fluence - 40 % Years années of projection de fluence -15% The actual fluence for 40 years lifetime (considering the reduction of fluence) is : 3 loop Reactors : 6.5 x 1019 n/cm2 4 - Loop RPV (1300 MWe) fluence at 40 years lifetime : 4.65 x 1019 n/cm2 8 /16

9 RTNDT RTNDTVALUES --RPV RPV SURVEILLANCE PROGRAMME. SURVEILLANCE PROGRAMME Capsule V Time of Duration in vessel (years) Capsule Capsule Capsule Capsule 1 (u) 2 (V) 3 (Z) 4 (Y) Capsule W Capsule U Equivalent time of irradiation of Vessel (Years) Capsule X Capsule Z Capsule Y Extension of the RPV irradiation surveillance : introduction of reserve irradiation capsules in the French plants since 1999 for all reactors. Two reserve capsules W and X in place of capsules U and Z after removing from reactor these capsules U and Z. CP1 CP2 Series Plants 9 /16 RTNDT RTNDT = C C ->CP0 ->CP0 units units RTNDT RTNDT = 73 C 73 C -> -> CP1/CP CP1/CP. units.

10 . CORE ZONE INSPECTION VPM 10 /16

11 STEAM GENERATOR REPLACEMENT PROGRAMME and STRATEGY The global Life Management strategy and Maintenance Program of Steam Generators are in relation with: The importance of the inspection Programme The on-going actions during NPPs time in operation normal and current Maintenance To anticipate the exceptional maintenance To anticipate to order the strategic components Classification of plants with SG Replacement strategy PERIODIC INSPECTIONS OF STEAM GENERATOR Technical SG End of Life SG Plugging Rate max: 12,5 or 15% Planning schedule in function of intervention on Plants (industrial capability, Availability of reserve of SG spare parts) Connection with SGR and 10-years outages 11 /16

12 Group 1 12 /16 Classification of PWR plants in relation with SR Replacement strategy Units with SG affected by dégradations and SGR is will be carry out in futur (date of SGR estimated) Group 2 Units with SG lifetime evaluation is with incertainties (evolution of dégradations is unknown, treat on SGR Planed with 3rd 10-years outage Group 3 Units with SG Lifetime = Plant lifetime GROUP 1 DAMPIERRE 2, DAMPIERRE 4 GRAVELINES 3 BUGEY 2, BUGEY 3, BUGEY 4 FESSENHEIM 2 BLAYAIS 1 GROUP 2 CHINON B1, CHINON B2 BLAYAIS 2, BLAYAIS 3, BLAYAIS 4 GROUP Mwe : 21 units CRUAS GRAVELINES 5 6 CHINON B3 B4 Units with SG replaced in past 1300 MWe: all 20 units 1450 MWe : all 4 units

13 SYNTHESIS of DURATION FRENCH SGR D U R A T DURÉES en JOURS I O N I N D A Y S DAM1 SG In 2 Parts BUG5 Heures en zone Total hours in controled zone Durée Outagede total l'arrêt Duration (jours) Durée SGR Duration du RGV (jours) dont environ hours10000 on CVCS de RCV RPV Inspection Core Zone VPM GRA1 SLB1 DAM3 GRA2 TRI2 TRI1 GRA4 TRI3 SG In 2 Parts 0 FES T O T A L D U R A T I O N HEURES en ZONE I N Z O N E 13 /16

14 PLANNING OF SG REPLACEMENT DAM1 DA3 SLB1 BUG5 GRA1 GRA2 GRA4 SLB2 TRI2 TRI1 TRI3 FES1 TRI4 DAM SGR Carried out Réalisées 14 /16 Futur SGR SLB2 DAM2 BUG 4 TRI4 BUG4 CHB1, DAM4, BLA1, DAM4, GRA3,...? A venir

15 Example SGR One Piece Monobloc. ~ 20 m 320 tons in weight 15 /16

16 CONCLUSION All of actions engaged and applied on 58 NPPs taking into account the large informations capitalised in database from the feedback experience informations, current Maintenance and exceptionnal maintenance give to the french utility the good approaches to the long term life Management The importance of Criteria combined with periodic inspection and in relation with: The global Maintenance program and strategy Specific Maintenance and Inspection for RPV and for Steam Generator The monitoring to enrich the feedback experience and database collected on Steam Generator and RPV To anticipate the exceptional maintenance Mainly for SGR To anticipate to order the strategic components are very important for Plant Life Mnagement Strategy 16 /16