Decomissioning & Waste Management Unit GRAPHITE GAS REACTORS SLA1 & SLA2 : FROM SAMPLING STRATEGY TO WORKING CONDITIONS Atoms for the future 27 th -30 th June 2016 Contact : Clémence WEILL clemence.weill@edf.fr
OVERVIEW 1. EDF s DECOMMISSIONNING & WASTE MANAGEMENT UNIT 2. INTRODUCTION TO GRAPHITE GAS REACTORS 3. WASTE MANAGEMENT GENERAL INFORMATION 4. AN ATYPICAL PROJECT A. SAMPLING STRATEGY B. PREPARATORY WORKS C. WORKING CONDITONS D. RESULTS E. ANALYSIS 5. CONCLUSION Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 2
1. EDF s DECOMMISSIONNING & WASTE MANAGEMENT UNIT 450 people (Lyon/Paris), 1 incinerator and 1 melting furnace, 9 reactors with an ongoing nuclear decommissioning: 1 heavy reactor, 1 PWR, 6 graphite gas, 1 Fast Neutron. Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 3
2. INTRODUCTION TO GRAPHITE GAS REACTORS OF SAINT-LAURENT A Industrial data: First industrial production : SLA1 : 1969, SLA2 : 1971 Power output : SLA1 : 480MWe, SLA2 : 515MWe Final shut down SLA1 : 1990, SLA2 : 1992 Decommissioning: Conventional and industrial buildings are removed, Nuclear decommissioning on-going out of the reactor Fuel removed after the shutting down Copyright Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 4
2. INTRODUCTION TO GRAPHITE GAS REACTORS OF SAINT-LAURENT A 56 m hight Fuel : natural uranium Moderator : graphite Coolant : Gas CO 2 56 m high 30 m in diameter Cavity: 17 x 40 m Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 5
3. WASTE MANAGEMENT GENERAL INFORMATION Managing nuclear waste : a long process CHARACTERIZATION ANDRA Waste acceptance Packaging /Transport Disposal on repository Characterization : Getting a radiological inventory and knowledge of your waste Activation Contamination Chemical composition and neutron flux Modelisation (tools) Measurements Samples Samples are the first step to evacuate your waste Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 6
4. AN ATYPICAL PROJECT A. Sampling strategy Two main objectives : 1. Build the radiological inventory Core reactor : activation and contamination Smears surfacic contamination Metallic samples Chemical composition of steels (for activation calculations) 2. Confirm the mechanical characteristics of the metallic structure «Massive» metallic samples (up to 6 kg) The mechanical characteristics and level of corrosion and irradiation metal structures Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 7
4. AN ATYPICAL PROJECT B. Preparatory works Before intervention : Identification and localisation of the differents steels based on the knowledge of the steels : Identification of those which need samples Pre-positionning of samples and therefore identification of new sampler machines Machines processing and tests Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 8
4. AN ATYPICAL PROJET C. Working conditions Limited duration of the interventions Max duration 1h45 due to temperature conditions ( 25-30 C) First risk of accident : faintness Working clothes Suits : Various suits tested due to sweating issues Respiratory protection devices Powered fresh air hose breathing apparatus to prevent from internal contamination 5 pairs of gloves! 2 Copyright Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 9
4. AN ATYPICAL PROJECT D. Results «MASSIVES» METALLIC SAMPLES 5/6 days / sample SMEARS : Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 10
4. AN ATYPICAL PROJECT D. Results The table below shows the number of each sample Type Number of samples for each reactor Smear 106 Metallic samples 83 Duration (from studies to intervention on site) : 27 months Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 11
4. AN ATYPICAL PROJECT D. Analysis getting the radiological inventory In order to get the composition of steels, the following analysis will be done on µ-core : Analysis of trace elements with ICP/MS Smears : radiological analysis Gamma spectrometry Gross alpha and gross beta Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 12
4. AN ATYPICAL PROJECT D. Analysis verification of holding structures In order to prove the holding of the reactor, 2 sets of analysis were done on massive metallic samples: 1. Corrosion : Visual examinations, Metallographic examinations, Microscope investigations to determine the corrosion thickness 2. Mechanical characteristics Tenacity values, Traction tests, Resilience tests, Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 13
5. CONCLUSION 1. Feedback : 1. Hard working conditions : 1. Temperature 2. Suits 2. Samples : 1. Enable to check the structure, 2. Will give the radiological inventory (in progress) Dismantling is not only about removing the equipements it s also about disposing of the radiological waste and the first step is to know the radiological inventory meaning caracterizing by sampling! Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 14
Thank you - Any questions? Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 15
2. WASTE MANAGEMENT GENERAL INFORMATION Repositories A single public body in charge : ANDRA (National Radiological Waste Agency) French nuclear waste classification Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 16
ANDRA DIFFERENT REPOSITORIES CIRES CSA CIGEO (under development) Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 17
CIRES Schematic diagram of a disposal cell at ANDRA VLL waste repository Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 18
Nuclear waste (without used fuel) FAMA vl 300t Graphite 17 000t FAMA vc 50 000t TFA 115 000t Conventionnel 800 000t < 0,05 % < 2% ~ 5% ~ 15% ~ 80% The first reactor generation s nuclear waste Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 19
NUMERICAL ACTIVATION SCHEME nuclear data base - cross sections nuclear data base - cross sections - radioactive series measured radioactive inventory (x,y,z,t 1 ) 1 Monte Carlo code solving Boltzmann equation 3D neutron flux map (x,y,z,e,t) 2 code solving Bateman equations system calculated radioactive inventory (x,y,z,t i ) 3 comparisons between Calculated and Measured results validated calculated radioactive inventory (x,y,z,t 2 ) - 3 dimensional geometry - chemical compositions with no impurities - calculated neutron sources - nominal power rating conditions - chemical compositions with impurities - history of irradiation C/M * ratios * : calculated/measured values copyright Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 20
WASTE MANAGEMENT GENERAL INFORMATION Caracterization - activated circuits / waste Phase 1 : determination of ratios Phase 2 : activity measurement Chemestry & historical data Calculations Dose rates measurement on waste Definition of scaling factor versus tracers ( 60 Co and 137 Cs) : Example for tritium : 3 H : x Bq/g 60 Co :y Bq/g SF3H= x/y Objective : one method applicable to all nuclear waste that have the same origin of contamination Activity of 60 Co or 137 Cs Utilisation of SF to determine all RN Example for determination of 3H activity : 3H = x/y * measure of 60 Co Evaluation of each radionuclide Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 21
WASTE MANAGEMENT GENERAL INFORMATION Caracterization - contaminated circuits/ waste Phase 1 : determination of ratios Phase 2 : activity measurement Realization of several samples representative of the circuits Laboratories Definition of ratios versus tracers ( 60 Co and 137 Cs) : Example for tritium : 3 H : x Bq/g 60 Co :y Bq/g Ratio 3H= x/y Objective : one method applicable to all nuclear waste that have the same origin of contamination Dose rates measurement on waste Activity of 60 Co or 137 Cs Utilisation of ratios to determine all RN Example for determination of 3H activity : 3H = x/y * measure of 60 Co Evaluation of each radionuclide Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 22
GRAPHITE GAS REACTOR Top head Guides tubes Graphite block Core Barrel Thermal shield Liner Core support floor Steam generator modules Support skirt Circulators Bottom head penetrations Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 23
GRAPHITE GAS REACTORS OF SAINT-LAURENT A Graphite gas reactors with internal heat exchangers Upper exchangers zone Annular zone Lower exchangers zone Access tunnels Copyright ou crédit photo Graphite Gas reactors : from sampling strategy to operating conditions 2016/06/28 24