Glass formulation for nuclear waste containment DE LA RECHERCHE - PowerPoint PPT Presentation

Glass formulation for nuclear waste containment DE LA RECHERCHE À L’INDUSTRIE Joint ICTP-IAEA International School on Nuclear Waste Vitrification – 23 - 27 Septembre 2019 - TRIESTE E. Régnier Commissariat à l’énergie atomique et aux énergies alternatives - www.cea.fr 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

CEA-Marcoule Nuclear energy R&D … since 1955 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

CEA Marcoule center (~5000 peoples) Research facilities ICSM Institut for Separation Chemistry Vitrification Process development Material science ATALANTE Reprocessing Separation chemistry Cementation Conditioning matrices Decontamination Fuel fabrication Interim storage of spent fuels 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

Content I. Nuclear waste to be vitrified 1) Origin of nuclear waste 2) Objectives of nuclear waste containment II. Some basic knowledge on glass 1) Glass structure 2) Glass formers / modifiers / intermediates 3) Role of radioelements in the glass structure III. How to formulate a nuclear glass? 1) Which constraints have to be respected? 2) Methodology to formulate a nuclear glass 3) CEA experience in nuclear glass formulation 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

Introduction: Nuclear waste to be vitrified https://www.jnfl.co.jp/en/business/uran/  Nuclear waste produced at all stages of the Nuclear Fuel Cycle (from mines to spent fuel reprocessing) + Decommissioning & Dismantling (D&D) operations https://www.researchgate.net/figure/Uranium-and-nuclear-fuel-cycle-sectors_fig11_317779578 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

Introduction: Nuclear waste to be vitrified Waste classification Very short lived Short lived Long lived Very low level VLLW (disposed of at the CSTFA facility located in (VLLW) VSLW (managed first the Aube district) through on-site decay Low level waste LILW-SL (disposed of LLW-LL (near-surface and then disposed of as at the CSFMA facility repository) (LLW) conventional waste) (Aube)) Intermediate level ILW-LL (deep disposal, 63 % vol but 0,02 at 500 m, under dvpt) waste (ILW) % of radioactivity High level waste HLW (deep diposal, at 500 m, under dvpt) (HLW) Source : ANDRA, 2014  Used fuel reprocessing (PUREX process)  The resulting Fission Products (FP) / minor Actinids (mA) solutions are the main radioactive waste of the fuel cycle: 96 % of radioactivity (but 0,2 % vol) 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

Introduction: Nuclear waste to be vitrified Radiotoxicity of HLW Spent fuel / reprocessed spent fuel  Very important to propose a long term reliable solution for storage! Source : https://hal-cea.archives-ouvertes.fr/cea-01153306/file/cea6-en.pdf 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

Introduction: Nuclear waste to be vitrified  The highly radioactive and very complex FP solutions are produced by the PUREX process. They contain ~40 chemical elements that must be continuously stirred and cooled to dissipate their thermal power.  Conserving them in the liquid state is not a sustainable option => France (as well as US, UK, Canada) began to study solidification process in the 50’s. Fission Product / minor actinides solution Fission Products (FP) Addition elements Actinides Adjuvants Corrosion products CEA | DECEMBRE 2014 | PAGE 17 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

Introduction: Nuclear waste to be vitrified The aim is to confine radionuclides by establishing chemical bonds Si Act Al O B PF Na Remind: ~40 elements in the waste solution 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

Introduction: Nuclear waste to be vitrified Mica-phlogopite  The program began by attempting to produce synthetic minerals such as mica K[Si 3 Al][Mg 3 ]O 10 (OH) 2 or feldspar ((Na,K)AlSi 3 O 8 , but glass soon proved to be the only material capable of immobilizing all the elements present in such complex solutions.  Choice of glass in Canada, France, US, Germany, USSR.  In France, the first radioactive glass was synthesized at laboratory scale at CEA in 1957  Birth of vitrification in the 50’s  A new application of the glass was born: containment glasses  Needs of R&D on: - Material (specific composition of nucl. glass, long term behavior) - Process 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

Content I. Nuclear waste to be vitrified 1) Origin of nuclear waste 2) Objectives of nuclear waste containment II. Some basic knowledge on glass 1) Glass structure 2) Glass formers / modifiers / intermediates 3) Role of radioelements in the glass structure III. How to formulate a nuclear glass? 1) Which constraints have to be respected? 2) Methodology to formulate a nuclear glass 3) CEA experience in nuclear glass formulation 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

1) Glass structure Glass structure: a disordered structure 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

1) Glass structure Cristallized state (SiO 2 ): Vitreous state (SiO 2 ): - Repetition of elementary patterns - Assembly of connected polyhedra  Ordered material  No long range order Thanks to its disordered structure, glass is able to incorporate many different elements within its structure. However, the role of each element in this structure differs from an element to another. 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

2) Glass formers / glass modifiers - Network formers - SiO 2 , B 2 O 3 , GeO 2 , P 2 O 5  Able to form a glass alone (iono-covalent links)  SiO 4 , BO 4 / BO 3 … polyhedra linked by their tops SiO 2 glass SiO 2- B 2 O 3 glass 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

2) Glass formers / glass modifiers - Network modifiers - Alkaline, Alkali earth, some transition elements and rare earthes  Are not able to form glasses alone (cristallize) (ionic links)  In glass network: break the bonds example of Na + in SiO 2 glass Effect on the glass properties: • Decrease the melting temperature • Decrease the glass viscosity • Decrease the chemical durability 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

2) Glass formers / glass modifiers - Intermediate elements - Al 2 O 3 , ZnO, ZrO 2 , PbO, TiO 2  Are not able to form glasses alone (cristallize)  Can reinfore or break the bonds (depends on their content, on glass composition…) Case of Al 2 O 3  Can form [AlO 4 ] - tetrahedrons as well as [SiO 4 ] - if positive charges are available  Possible with alcaline ions  But if Al 2 O 3 /A 2 O < 1, then not enough alkalines to compensate [AlO 4 ] - charges => Al -> [AlO 6 ] = modifier. 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

2) Glass formers / glass modifiers - Summary - Formers Intermediates Modifiers SiO 2 Al 2 O 3 Li 2 O GeO 2 PbO Na 2 O B 2 O 3 ZnO K 2 O P 2 O 5 CdO CaO As 2 O 3 TiO 2 BaO As 2 O 5 V 2 O 5 (can be found in every books on glass science) 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

2) Role of radioelements in the glass structure Fission Product / minor actinides solution Remind Fission Products (FP) Addition elements Actinides Adjuvants Network formers : SiO 2 , Corrosion products B 2 O 3 , GeO 2 , P 2 O 5 Network modifiers : Alkaline , Alkali earth , some transition elements and rare earthes Intermediates : Al 2 O 3 , ZnO, ZrO 2 , PbO, TiO 2 CEA | DECEMBRE 2014 | PAGE 17  Most of the elements present in the FP solutions: unknown behavior in glass (no data from traditionnal glass industry)  Knowledge had to be acquired 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

2) Role of radioelements in the glass structure Knowledge acquired for Fission Product / minor actinides solution nuclear borosilicate glass Fission Products (FP) Addition elements Transition elements mainly Actinides Adjuvants act as intermediate elements. Corrosion products They have almost no impact on glass durability and viscosity, but can crystallize (cf. spinel). Fission products will generally act as intermediate elements. They tend to increase the resistance of glasses against water corrosion, increase glass viscosity and tend to lead to phase separation (Mo) CEA | DECEMBRE 2014 | PAGE 17 or crystallization (RE 2 O 3 , Ce, Mo). Specific case of platinoids elements: unsoluble elements in borosilicate glasses. They have almost no impact on glass corrosion by water, modify the glass rheology, and act as nucleating agents for crystallization. 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives

2) Role of radioelements in the glass structure More complex glasses? BO 3 BO 4 SiO 4 AlO 4 Complex glasses  a combination between an experimental approach / a statistical approach / basic knowledge on glass science is needed 26 septembre 2019 Commissariat à l’énergie atomique et aux énergies alternatives