C-14 in wastes from LWR and its relevance to the longterm safety of waste disposal

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1 C- in wastes from LWR and its relevance to the longterm safety of waste disposal Vanessa Montoya , Karlsruhe, Germany

2 Content General Aspects of C- C- in the nature C- from human activities Source of C- in Nuclear Power generation (LWR) Transformation of C- during storage and disposal 2

3 Carbon Radionuclide: β emitter T 1/2 = 5,730 years Weak beta emitters Long half-live High isotopic exchange ( 12 C and 13 C) Incorporation into living organisms β decay 3

4 Carbon Production and release of C- Nuclear weapon testing (not anymore) 1x10 15 Bq/y Yim et al. 2006, Progress in Nuclear Energy, 2 Natural production By cosmic ray neutron interaction with N CO 2 Nuclear Power Plants Nuclear Power generation Reprocessing 4

5 Nuclear Power generation Source: World Nuclear Association Fuel Reprocessing Nuclear Power Plant Nuclear Waste Disposal 5

6 Nuclear Power Plant C- world inventory 444 reactors in operation* 185 reactors (58 France) 287 PWR + 78 BWR Research reactors are not included *Data from June 2016 (IAEA) 6

7 Nuclear Power Plant Type of Nuclear reactors: Light Water Reactors Moderator = coolant = Water Slows down the neutrons released from fission To transfer the heat Nuclear reactor primary system 7

8 Nuclear Power Plant Type of Nuclear reactors: Light Water Reactors 8

9 Nuclear Power Plant Source of C- From Nitrogen + neutrons Component or impurity in fuels (cladding), moderators, coolants, structural hardware (metals). β decay (Estable) (99.6% abundance) T 1/2 = 5,730 years 9

10 Nuclear Power Plant Source of C- From 13 Carbon + neutrons From 17 Oxygen + neutrons 13 C + 1 n (1.1% abundance) C + γ Graphite moderators (Not relevant for LW Reactors) 17 O + 1 n C + 2 α (0.038 % abundance) Oxide fuels, moderators = coolants (Water) 10

11 Nuclear Power Plant Source of C- Fuel N impurities zircaloy/uo 2 BWR N impurities UO 2 PWR Coolant Presure 17 O in H 2 O 13 CO 2 dissolved is negligible 1TBq = Bq 11

12 The chemistry of C- C- chemical system at 25 C CO 2 (g) Kinetics can play a role C(+IV) C(0) C(-IV) Speciation depends on: Eh ph Temperature Other organics are not included (mixed oxidation states) 12

13 The chemistry of C- Chemical conditions in LWR Pressurized water reactor (PWR) Reducing conditions H 2 + C? C - organics CO 2 C (s) CH 4 (g) C - organics organics = formaldehyde + methanol ( H Reducing conditions (high P 155 bar) 2 CO) ( CH 3 OH) H C Coolant system = % organics 13

14 The chemistry of C- Chemical conditions in LWR Boiling water reactor (BWR) Oxidizing conditions C CO 2 (g) H CO 3 - Oxidizing conditions Vance et al. 1995, TR EPRI 300 C and 72 bar Coolant system = HCO 3 -

15 The chemistry of C- Chemical conditions in LWR and forms of waste Solid Gas production Solid phase Aqueous (coolant) CO 2 CH 4, Treatment in the NPP < 3 x Bq/y ( 3 order of magnitude lower than natural background) Yim et al. 2006, Progress in Nuclear Energy, 2 Spent Fuel Zircaloy Steel (metals) Structural fuel material Resins (ion exchange) H CO - 3 C organics (colloids) H CO 3 - C organics (colloids) 15

16 Form of waste in LLW Initial inventory of C Dry radioactive waste: plastic, textiles and cellulose, in the form of protective clothing, rags, paper etc. Reactor coolant Cleanup filters. (Recently increase due to the use of sub-micron size filters). Yim et al. 2006, Progress in Nuclear Energy, 2 16

17 Radioactive waste NPP Final disposal Irradiated Nuclear fuel Waste from reprocessing (i.e vitrified) Intermediate storage Repository for heat generating radioactive waste Heat generating radioactive waste (NPP operational waste and decommissioning) Repository for radioactive waste with negligible heat generation Negligible heat generating waste Intermediate storage 17

18 Radioactive waste Reprocessing CO 2 (g) 18

19 Intermediate storage LLW Operational waste (effluent treatment, circuit, etc) Resins T Intermediate storage Chemical transformation T Temperature Redox conditions (O 2 ) Microbial activity Degradation Contact with chemicals H CO 3 - C - organics HCO 3 -, C(s),? C - organics CO 2 (g) 19

20 Final storage LLW - near surface disposal at ground level Schematic diagram of a disposal cell (ANDRA-France) 20

21 Final storage LLW - near surface disposal at ground level LLW Drigg, Cumbria (NDA-UK) LLW-ILW El Cabril (ENRESA-Spain) LLW Rokkasho-Mura (JNFL-Japan) LLW Texas Compact (WCS-USA) 21

22 Final disposal LLW/ILW - near surface disposal below ground level short-lived radioactive waste 50 m (Baltic sea) SFR, Forsmark (SKB-Sweden) 22

23 Final disposal Multibarrier system 23

24 Multibarrier system Waste matrix and waste container Cement matrix Synthetic polymers Glassy carbon High ph porewater (> 12) Low porosity, permeability Silicon carbide matrix Organic compounds Polyethylene, bitumen Graphite matrix Low porosity, permeability High temperature stability Waste container Properties close to diamond (expensive) (Very resistant to attack by natural environment) Highly durable waste container (metallic, High integry containers) 24

25 Management of C in LLW Spent Ion exchange resins Waste (NPP) Interim storage Final disposal Resins with C H CO 3 - C - organics Treatment of the resins Separation Resin / C Change enviroment C (solid matrix) Degradation of the resins with C (SIER) Microbial actions (gas production) Groundwater infiltration. 25

26 Management of C in LLW Irradiated steel Waste (NPP) Interim storage Final disposal Steel NPP structures Nuclear fuel assemblies C-steel Stainless steel Ni-alloys (Decommissioning) Cemented waste Corrosion Carbides (M n-1 C 2*x ) (covalent, ionic) + H 2 O? Release of C by corrosion Aerobic Anaerobic conditions. HCO 3 -, alcohols? CH 4 + hydrocarbons 26

27 Intermediate storage HLW including Spent Fuel Spent Fuel UO 2 pellets ~95 wt% UO 2 matrix N impurities U 17 O 2 matrix + n C (especiation?) 27

28 Intermediate storage HLW including Spent Fuel Spent Fuel Intermediate storage (dry cask) T H CO 3 - C (especiation?) (pools) Pools are monitored and cleaned (filters) 28

29 Intermediate storage HLW including Spent Fuel (dry cask) 6 m Zwilag s ZZL (Switzerland) Gorleben (Germany) 29

30 Final disposal HLW including Spent Fuel Isolation is provided by a combination of engineered and natural barriers (rock, salt, clay) and no obligation to actively maintain the facility is passed on to future generations. A multi-barrier concept, with the waste packaging, the engineered repository and the geology all providing barriers to prevent the radionuclides from reaching humans and the environment. 30

31 Management of C in HLW Spent Fuel Waste (NPP) Interim storage Final disposal Spent Fuel (including zircaloy) Corrosion Release from SF? (Matrix dissolution, IRF) Release of C by corrosion Aerobic Anaerobic conditions. Dose of C in spent fuel very small compared with other radionuclides Presentation E. Gonzalez-Robles 31

32 What have we learnt? Production of C- C- in the nature C- from human activities (Nuclear Energy production) Source of C- in Nuclear Power generation (LWR) Transformation of C- during storage and disposal 32

33 What have we learnt? Nuclear PP Interim storage Final disposal Source of C Spent Fuel Metallic Structures Ion exchange resins H CO 3 - (inorganic) C - organics Transformation Temperature Redox conditions (O 2 ) Microbial activity Degradation Contact with chemicals Corrosion C waste H CO - 3 (inorganic) C - organics Safety Analysis Presentation V. Metz tomorrow CO 2 (g) C is a long lived radionuclide 33

34 The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/ ) under grant agreement (CAST project) 34