From Waste to Value : Accelerator-based Inherently Safe Nuclear Power

1. From Waste to Value :Accelerator-based Inherently Safe Nuclear Power Y. Kadi CERN, Switzerland 20-21 September 2007, Nuclear Risks - Safety and Security, Oslo, Norway Y. Kadi

2. A new primary energy source • By 2050, the world’s consumption (+ 2%/y) should reach 34 TW, of which 20 TW should come from new energy sources:A major innovation is needed in order to replace the expected “decay” of the traditional energy sources! • This implies a strong R&D effort, which is the only hope to solve the energy problem on the long term. This R&D should not exclude any direction a priori! • Renewables • Nuclear (fission and fusion) • Use of hydrogen • Can nuclear energy play a major role? • Nuclear energy has the potential to satisfy the demand for a long time (at least 15 centuries for fission, essentially infinite for fusion if it ever works), and is obviously appealing from the point of view of atmospheric emissions. Y. Kadi

3. Which type of nuclear energy? • Nuclear fusion energy: not yet proven to be practical. Conceptual level not reached (magnetic or inertial confinement?). ITER a step, hopefully in the right direction. • Nuclear fission energy: well understood, and the technology exists, with a long (≥ 50 years) experience, however, present scheme has its own problems: • Military proliferation (production and extraction of plutonium); • Possibility of accidents (Chernobyl [1986]; Three Mile island [1979]); • Waste management. • However, it is not given by Nature, that the way we use nuclear fission energy today is the only and best way to do it. One should rather ask the question:Could nuclear fission be exploited in a way that is acceptable to Society? • To answer this question, Scientists around the world have carried out, since the 1990’s, an extensive experimental programme which has led to a conceptual design of a new type of nuclear fission system, driven by a proton accelerator, with very attractive properties. Y. Kadi

4. Historical Background p The idea of producing neutrons by spallation with an accelerator has been around for a long time: + In 1950, Ernest O. Lawrence at Berkeley proposed to produce plutonium from depleted uranium at Oak Ridge. The Material Testing Accelerator (MTA) project was abandoned in 1954. + In 1952, W. B. Lewis in Canada proposed to use an accelerator to produce 233U from thorium, in an attempt to close the fuel cycle for CANDU type reactors. Concept of accelerator breeder : exploiting the spallation process to breed fissile material directly soon abandoned. Ip ≈ 300 mA + Renewed interest in the 1980's and beginning of the 1990's, in particular in Japan (OMEGA project at Japan Atomic Energy Research Institute), in the US (Hiroshi Takahashi et al. proposal of a fast neutron hybrid system at Brookhaven for minor actinide transmutation and Charles Bowman a thermal neutron molten salt system based on the thorium cycle at Los Alamos), and in Europe (SPIN program at the French-CEA). Y. Kadi

5. Transmutation of nuclear waste Direct use of spallation neutrons ? Where : qfp = fraction of FP to be transmuted (99Tc, 129I, 135Cs, 90Sr, 85Kr and 93Zr ≈ 28%) Ep = incident proton energy (1000 MeV) sp = spallation neutron yield (≈ 30 for Pb target) b = electrical efficiency for accelerating protons (≈ 50%) T = thermal efficiency (≈ 33%) This would represent 60/200 ≈ 30% of the total fission energy produce not economical ! Y. Kadi

6. Basic Principle of Energy Amplifier Systems • One way to obtain intense neutron sources is to use a hybrid sub-critical reactor-accelerator system called Accelerator-Driven System:  The accelerator bombards a target with high-energy protons which produces a very intense neutron source through the spallation process.  These neutrons can consequently be multiplied (fission and n,xn) in the sub-critical core which surrounds the spallation target. Y. Kadi

7. Neutron Multiplication In and ADS ? Where : k = neutron multiplication factor * = source importance (≈ 1.5)  = neutrons emitted per fission (≈ 2.5) Ef = energy generated per fission (≈ 3.1x10-10 W) i = accelerator current C = charge of a proton (= 1.6x10-19 C) In order for the process to be self-sufficient Y. Kadi

8. The FEAT experiment 3.6 tons of natural uranium Y. Kadi

9. Main FEAT results Y. Kadi

10. Physics of Sub-Critical Systems Y. Kadi

11. There is a spectacular difference between a critical reactor and an EA (reactivity in $ = r/b; r = (k–1)/k) : • Figure extracted from C. Rubbia et al., CERN/AT/95-53 9 (ET) showing the effect of a rapid reactivity insertion in the Energy Amplifier for two values of subcriticality (0.98 and 0.96), compared with a Fast Breeder Critical Reactor. • 2.5 $ (Dk/k ~ 6.510–3) of reactivity change corresponds to the sudden extraction of all control rods from the reactor. Advantages of Sub-Critical Systems • EAs operate in a non self-sustained chain reaction mode  minimises criticality and power excursions • EAs are operated in a sub-critical mode stays sub-critical whether accelerator is on or off  extra level of safety against criticality accidents • The accelerator provides a control mechanism for sub-critical systems  more convenient than control rods in critical reactor  safety concerns, neutron economy • EAs accept fuels that would not be acceptable in critical reactors  Minor Actinides  High Pu content  LLFF... Y. Kadi

12. Energy Amplifiers vs Critical Reactors Main objective is to reduce the production of nuclear waste (TRU) • Energy Amplifier : • sub-critical • fast neutrons • Thorium + 233U +TRU (Pu + Minor Actinides) • Reactor : • critical • slow neutrons • Uranium + Pu Y. Kadi

13. Fast neutrons and high burn-up Fast neutrons allow a more efficient use of the fuel by allowing an extended burnup Y. Kadi

14. Evolution of radiotoxicity of nuclear waste • TRU constitute by far the main waste problem [long lifetime – reactivity]. The system should be optimized to destroy TRU. Same as optimizing for a system that minimises TRU production. Interesting for energy production! Typically 250kg of TRU and 830 kg of FF per Gwe Y. Kadi

15. The strategy consists in using the hardest possible neutron flux, so that all actinides can fission instead of accumulating as waste. Note: thermal fission resilient elements Nuclear waste: • Fission Fragments:(4%)the results of fissions transform them into stable elements through neutron capture • TRU:(1.1%)produced by neutron capture;dominated by plutonium: destroy them through fission Y. Kadi

16. Principle of LLFP destruction Y. Kadi

17. Experimental Setup Y. Kadi

18. TARC Results (2) Y. Kadi

19. Energy Amplifiers vs Critical Reactors Main objective is to reduce the production of nuclear waste (TRU) • Energy Amplifier : • sub-critical • fast neutrons • Thorium + 233U +TRU (Pu + Minor Actinides) • Reactor : • critical • slow neutrons • Uranium + Pu Y. Kadi

20. Radiotoxicity • The radiotoxicity of spent fuel reaches the level of coal ashes after only 500 years, and is similar to what is predicted for future hypothetical fusion systems Y. Kadi

21. General Features of Energy Amplifier Systems Subcritical system driven by a proton accelerator: • Fast neutrons (to fission all transuranic elements) • Fuel cycle based on thorium (minimisation of nuclear waste) • Lead as target to produce neutrons through spallation, as neutron moderator and as heat carrier • Deterministic safety with passive safety elements (protection against core melt down and beam window failure) Y. Kadi

22. Detailed Features of Energy Amplifier Systems Y. Kadi

23. R&D Activity in Europe Vast R&D activity in Europe over last 10 years: 12 countries, 43 institutions EU  31 MEuros Member States 100 MEuros Y. Kadi

24. STELLA Loop CIRCE Loop CEA ENEA VICE Loop CHEOPE Loop CorrWett Loop SCK-CEN ENEA PSI CIRCO Loop TALL Loop CIEMAT KTH DEMETRA: Test Facilities • In FP5, a complementory combination of test facilities was set up in Europe. • EUROTRANS is fully using these test facilities. Y. Kadi

25. NUDATA: Experimental Facilities GSI @ Darmstadt (Germany) Gelina @ Geel (UE-Belgium) nTOF @ CERN (Switzerland) and its TAS g-calorimeter Neutron capture (n,g) resonances in one actinide Cyclotron @ Uppsala (Sweden) Y. Kadi

26. MEGAPIE TARGET • MEGAPIE Project at PSI • 0.59 GeV proton beam • 1.3 MW beam power • Goals: • Demonstrate feasablility • One year service life • Operating since August 2006 F. Groeschel et al. (PSI) Proton Beam Y. Kadi

27. The eXperimental Accelerator-Driven System (XADS) in the 5° FP of the EU • 50 MW LBE-cooled XADS (MYRRHA) • 80 MW LBE-cooled XADS • 80 MW Gas-cooled XADS Y. Kadi

28. Worldwide Programs Y. Kadi

29. Conclusions • Can atomic power be green ? Physics suggests it can !! • Present accelerator technology can provide a suitable proton accelerator to drive new types of nuclear systems to destroy nuclear waste (including nuclear weapons) and/or to produce energy. • An Energy Amplifier could destroy TRU through fission at about x4 the rate at which they are produced in LWRs. LLFF such as 129I and 99Tc could be transmuted into stable elements in a parasitic mode, around the EA core, making use of the ARC method. • Next step: DEMO ? when ? where ? Y. Kadi