What is the Future of our radioactive waste?

1. What is the Future of our radioactive waste? Gabrielle DUPRÉ, Professor University of Orléans, and CNRS - ICARE ORLÉANS, France E-mail : gabrielle.dupre@cnrs-orleans.fr

2. What is the Future of radioactive waste? Before thinking of the future of radioactive waste for the next centuries - and in some cases for the next millenaries -, we have to know: • some elements of atomic and nuclear physics • what is called « radioactive waste »? • the specific properties? • their origin? • their peculiar treatment? • their storing mode? • the long-term memory of their storing?

3. Some elements of atomic physics The ATOM is theultimate entity of a simple species constituted of a nucleus and electrons

4. Some elements of atomic physics Atomic Nucleus : • is positively charged (charge = multiple of |e|) • contains the most part of the atom mass in a tiny volume • has no influence on chemical reactions but is fundamental for nuclear reactions • contains A nucleons (nucleons = protons + neutrons) • with a “mass number”: A = Z + N • Z: number of protons • Mass = mp = 1,6726 x 10-27 kg > mp • Positive charge = |e| = + 1,602 x 10-19 C • N: number of neutrons • Mass = mn = 1,6749 x 10-27 kg • Electric charge = 0

5. Some elements of atomic physics Electrons are gravitating around the atomic nucleus • very low mass: me = 9,1094 10-31 kg • negative charge: e = - 1,602 x 10-19 C • number: equal to the number of protons = Z • essential for chemical reactions, but not for nuclear reactions Nucleus and electrons, equally but oppositely charged, provide the neutrality of the atom

6. Some elements of atomic physics Isotopes of a same chemical element are: nuclides with the same number of protons (identical Z) but with a different number of neutrons N and a different mass number A Examples: Isotopes AZX: same Z and different A and N 23892U, 23592U, 23492U constituting the natural U element 11H , 21H, 31U, 41H constituting the H element

7. Stability of the atomic nucleus • Electrons belonging to a given atom are relatively independent: • they can escape from the attractive force of the nucleus, giving a positive ion • or other electron(s) can be attracted by the positively charged nucleus, giving a negative ion • Protons and neutrons, main constituents of the nucleus, are linked by very strong interactions, making generally the atomic nucleus very stable, although the Z protons having the same positive charge should flee from each other because of repulsion forces. However, • Protons and neutrons stay together within the nucleus • Nucleus mass: mnucleus < Z mp + N mn for a stable nucleus

8. Stability of the atomic nucleus For a stable atom: mnucleus < Z . mp + N . mn Δm = mnucleus - (Z mp + N mn ) is the“mass deficit” withΔm < 0 • Δm is the equivalent of the formation energy of the nucleus from its constituents: Z protons + N neutrons → nucleus (ΔHf) • According to Einstein: ΔHf = Δm . c2 (c: speed of light) • Since Δm is < 0, ΔHf is also < 0 • The link energy inside the nucleus EL corresponds to the energy necessary for dissociating the nucleus into its nucleons: EL = - ΔHf > 0

9. Stability of the atomic nucleus • For a stable nucleus: Δm < 0 and EL > 0 • For a radioactive (thus unstable) nucleus: Δm = 0 and EL = 0 • For a radioactive nucleus with very short life-time: Δm > 0 and EL < 0 EL depends on the number of nucleons: • If Z ≤ 20, then Z # N stable nucleus (N, O, Cl…) • If Z > 20, then N must increase to get a stable nucleus • There is a curve N = f(Z) around which nucleus are stable Away from the curve N = f(Z), and for N/Z ≥ 1.6 unstable nucleus are able to disintegrate spontaneously

10. Different types of radioactive disintegration reactions Emission β-: emission of electrons (e-) Ex:126C → 147N + 0-1e- Emission β+: emission of positrons (e+) Ex:116C → 115B + 01e+ Emission γ: electromagnetic emission It accompanies almost all disintegration reactions Emission α: emission of hellions (He nucleus) For high Z and A (A ≥ 206 : 84206Po isotope), the nucleus breaks into 2 pieces: Ex:23892U → 23490Th + 42He

11. Different other types of nuclear reactions Emission of neutrons: as the result of the collision of a light atom with a: - α particule: Ex:94Be + 42He → 126C + 10n stable stable - γ photon: Ex:94Be + 00γ → 84Be + 10n stable radioactive Fusion reaction: needs T # 108 K (ITER International Program) Ex: 21H + 31H → 42He + 10n + E (17.6 MeV) Fission reaction: Ex: 23592U + 10n →(9438Sr + 14054Xe) + (2 or 3 10n) + hν + E Fission products Several n Radiation Energy (≥ 200 MeV)

12. Fusion energy • Fusion energy: in thermonuclear reactors • None operating at present in France (the two existing have been stopped) • Fundamental research carried out at an international level in the Atomic Energy Commissariat (CEA) in Cadarache, Provence, France (ITER Project for a very long term: 22nd century)

13. Advantages and difficulties of fusion energy D + T → He (E = 3.5 Mev) + n (E = 14.1 MeV) • Advantages • Abundant resources of D and Li (→ T) inside the sea • Very little risk of uncontrolled reaction • Constant production, at any time, in all seasons • Very few radioactive waste, with a short half-life time (T = 12,3 y) • Activated reactor materials but with rapid decrease (T < 100 y) • Very little impact on environment (no CO2, no dust…) • Difficulties • Very high temperature having to be reached (plasma of ≈ 108 K) • Problems due to rapid neutrons • Risk of Tritium proliferation (→ thermonuclear bomb or bomb H)

14. Fission energy • Fission energy: in REP (Reactors with Pressurized Water), based on the fission of natural Uranium enriched with U235 isotope • REP : the only operating reactors in France at present (58 units on 19 different sites): 2nd generation of reactors • EPR : 3rd generation (1 EPR under construction at Flamanville, Normandy; another decided also in Normandy; one being built in Finland; others to be built in India, China…) • 4th generation (being conceived for 2040-2050)

15. Advantages and difficulties of fission energy 23592U + 10n →(9438Sr + 14054Xe) + (2 or 3 10n) + hν + E • Advantages • Abundant resources of Uranium in stable countries • Constant production, at any time, in all seasons (900–1400 MWe/unit) • 58 French REP, on 19 sites, along rivers or Atlantic ocean • Low impact on environment (no CO2, nor dust…) • Most waste with short radioactive period (managed by ANDRA) • Difficulties • Some radioactive waste with very long period, and strong activity (fission products, actinides) • Risk of uncontrolled reactions: limited but real (cf Tchernobyl, Fukushima) • Risk of proliferation of U enriched with U235 and with Pu (→A bomb) • Finite resources of Uranium (may be towards 2100-2200)

16. Reaction of fission in a Pressurized Water Reactor called « REP » Fission reaction: Ex: 23592U + 10n →(9438Sr + 14054Xe) + (2 or 3 10n) + hν + E Fissile Neutron Fission products Several n Energy nucleus (≥ 200 MeV) Remaining after reaction: 23892U and 23592U: recycled Production of: - Fission products: harmful waste (200 different FP) - Minor Actinides (Np, Am, Cm): long-life heavy nuclei - All Plutonium isotopes: among them, 23994Pu, a fissile nucleus, being separated at La Hague re-treatment plant -23994Puoxide mixed with natural U oxide provides a new nuclear matter called MOX (Mixed OXides of U and Pu)

17. Definition of waste, of radioactive waste • A waste is officially “any residue from production, transformation, or utilization processes, any substance, material, product, or more generally any abandoned staff or staff the owner wants to abandon” • A radioactive waste contains radioactive isotopes that are characterized by: • the production of dangerous ionizing radiations of very short wavelength (thus of large energy) • their long term activity and life-time

18. Among industrial waste: radioactive waste In France: Global amount of industrial waste: 2500 kg / year.person among them: 100 kg of toxic chemical waste 380 kg of home waste And only1 kg of radioactive waste (0.04%)

19. Origin of radioactive waste (in France) • Electro-nuclear waste (85%): production of electricity via nuclear energy • Some waste from care activities, from hospitals (14%), for diagnostics and/or therapy: slightly radioactive • Waste from other industries: food sterilization, quality control in metallurgy… • Waste from nuclear research and from production of radioactive isotopes • Waste from nuclear armament (not included in the %)

20. Electro-nuclear sites in the world, United States has the most important potential in terms of MegaWatts installed (99.210 MWe*) France has the second one (63.363 MWe*), but the first one if compared to respective population between USA and France Japan (47.839 MWe*: 3rd one), Germany, United Kingdom… are well equipped Italy has no more operating nuclear plants since 1997, but a certain number of storage sites do exist * 1995 data

22. Location of nuclear sites in the world

23. Location of nuclear sites in Europe

24. Location of nuclear sites in France

26. In Italy: 4 old nuclear plants (red points) and nuclear storage sites (black points and stars)

27. Classification of radioactive waste Ra → Rn + He (disintegration reaction) t = 0 n0 0 0 Any t>0 n < n0 Reaction rate: v = - dn / dt = λ n 1st order reaction Radioactive period: T = ln 2 / λ Classification according two criteria: • Radioactive activity: A = v = - dn / dt A provides the importance of protections to use for protection against ionizing radiations from waste • Radioactive period: T T defines the duration of waste potential nuisance

28. Classification of radioactive waste (in France) According to both criteria: A and T, several categories of waste are considered for storage: • very low radioactive waste coming from uranium mines and from deconstruction of some old nuclear plants (TFA) • waste of low and moderated activity with a short radioactive period (FMA) • waste of high activity (HA) and of moderated activity with a long radioactive period (MAVL) • waste containing graphite and/or radon

29. Classification of radioactive waste In France, for example: Global amount per year and per person: 1 kg of radioactive waste (0.04%) 900 g100 g « Short life-time »« Long life-time » (T<30 years, low or moderate A) (T>30 years or with high A) 80 g 20 g T>30 years high activity

31. Retreatment of used combustible

32. Three barriers for the confinement of radioactive matter in the case of a « REP » • 1st barrier: the metallic pencils containing uranium oxide enriched with 235U isotope • 2nd barrier: the concrete envelope of the reactor core • 3rd barrier: the double concrete wall of the reactor or concrete wall + metallic envelope

34. The UO2 or MOX pastilles are pilled in a series of long tubes, made of “zircaloy” (alloy of Zirconium (Zr) and 2.5% Tin (Sn)), forming the so called « combustible pencils » and thefirst barrier between the combustible matter and the environment The first barrier: the combustible pencil

35. The second barrier: a thick concrete wall surrounding the reactor core

36. The third barrier : the double thick concrete wall enveloping the reactor

37. Storage of nuclear (and other radioactive) waste

38. Several categories of radioactive waste (in France) with the purpose of storage According to both criteria: A and T, several categories of waste are considered for storage: • very low radioactive waste coming from uranium mines and from deconstruction of some old nuclear plants (TFA) • waste of low and moderated activity with a short radioactive period (FMA) • waste of high activity (HA) and of moderated activity with a long radioactive period (MAVL) • waste containing graphite and/or radon

40. Waste with very low activity (TFA)stored in Morvilliers center

45. Waste of low and moderated activity with a short radioactive period (FMA)

50. Waste of high activity (HA) and of moderated activity with a long radioactive period (MAVL)