High Power Protons: ESS & ADS. Steve Peggs, ESS & BNL

Transcription

1 High Power Protons: ESS & ADS, ESS & BNL

2 Q: Why ESS? A: Long pulses of cold neutrons Many research reactors in Europe are aging & will close before Up to 90% of their use is with cold neutrons There is a urgent need for a new high flux cold neutron source - Most users are fully satisfied by a long pulse source - Existing short pulse sources (ISIS, JPARC, SNS) can supply the present and imminent future need of short pulse users Pulsed cold neutrons will always be long pulsed as a result of the moderation process F. Mezei, NIM A,

3 Neutrons in 2019! 5 MW beam power 2.5 GeV protons (H+) 2.9 ms pulses 14 Hz rep rate 50 ma pulse current 704 MHz RF frequency < 1 W/m beam losses 7.5 MW upgradability? NO H- injection, no accumulator/compressor ring! 3

4 Evolution of neutron sources Effective thermal neutron flux n/cm 2 -s X-10 CP-2 Berkeley 37-inch cyclotron 350 mci Ra-Be source Chadwick NRX CP-1 MTR NRU HFIR HFBR ILL ZINP-P / WNR ZINP-P IPNS KENS ISIS SINQ Steady State Sources Pulsed Sources FRM-II SNS J-PARC ESS (Updated from Neutron Scattering, K. Skold and D. L. Price, eds., Academic Press, 1986)

5 The ESS site is in Sweden! Sweden, Denmark & Norway cover 50% of cost Lund! The other 14 member states covers the rest, with the European Investment Bank 5

6 Fixed linac end & target Max-IV under construction 6

7 The ESS green field 7

8 Technical issues 8

9 32-28 MW - the green strategy Liquifiers 69 GWh/y Klystrons Instruments 5 GWh/y Accelerator 123 GWh/y Ion source 7 GWh/y Target station 11 GWh/y 9

10 The sustainable way Responsible Carbon dioxide: -30,000 ton/y Renewable Carbon dioxide: -120,000 ton/y Recyclable Carbon dioxide: -15,000 ton/y

11 energyworkshop 11

12 Cryomodules continuous, segmented... or hybrid? SPL/ESS A half cryomodule is being built & will be tested at SM18 in collaboration with CERN BASELINE continuous elliptical cryomodules (LEFT) W. Hees, ESS, V. Parma, CERN & G. Devanz, CEA 12

13 Cryomodules 2011 HYBRID layout is under evaluation. A ~70K sleeve encloses (most cold) interconects, reducing heat load. Some interconnects may be left warm, e.g. to simplify beam instrumentation. 13

14 Target-to-neutrons How difficult can it be? v=ijwwfcw0foo Rotating tungsten disk target - cooled by helium - diameter 1.50 m - thickness 0.08 m - rotation rate 0.5 Hz Target-to-neutron-lines - 22 neutron lines - Not all instruments commissioned on Day 1 - Moderators ~10 cm above & below target 14

15 Target-to-accelerator Accelerator-to-Target - Rise from -10 to +1.6 m - Tune-Up Dump - Beam windows - Distributed systems - Beam diagnostics - Protection systems 15

16 SRF linac optics Transverse beta functions (TOP) increase smoothly - weakening doublets - ~constant beam size - little emittance growth Longitudinal optics (BOTTOM) represented by phase advance rate Spokes Lo-beta High-beta - matched transitions - one klystron per cavity M. Eshraqi, H. Danared, K. Rathsman 16

17 Longitudinal strengths 28 spoke cavities 64 low beta elliptical cavities 120 high beta elliptical cavities Extrapolate these idealized optics to the real world: - SNS experience with a broad range of as-built cavity gradients - ILC planning for a +/-20% range of gradients Quality assurance, production testing, sorting, re-tuning, simulating? 17

18 Beam losses Radio-activation is unacceptable from losses larger than about 1 W/m. Intra-beam stripping is plausibly an important source of beam losses in H- linacs like the SNS (0.2 W/m) - but not in the H+ ESS! Other potential beam loss sources: 1. Space charge resonances 2. Transverse overfocusing 3. Uncollimated low energy beam halo Confidently predicting the relative importance of loss mechanisms is a fundamental challenge to our ability to design multi-mw proton linacs. Resolve by 1) simulation & theory, 2) experiment (eg, SNS)... 18

19 RF issues Higher Order Modes - There is risk in NOT damping, & also IN damping HOMs - HOM couplers will be installed if ongoing studies indicate the need - Could be instrumented to measure transverse displacements Field Emission & Multipacting - SNS experience indicates that FE & MP may limit cavity performance - Excessive power into HOM electronics, via thermal detuning? - A simulation campaign has been launched Low Level RF - Protons: semi-relativistic speeds cause phase & amplitude errors to accumulate along the linac - Investigations (eg of modulator ripple & droop) are in progress 19

20 Thorium: With or without Accelerators? 20

21 Energy Amplifier Grid Reactor core Energy extraction Protons Neutrons Accelerator Spallation target Neutron multiplication factor typically k = 0.98 Protons hitting a target generate external neutrons into a subcritical thorium reactor core that burns, creating heat & electricity. Power generation ceases immediately when the beam stops Inherent safety (?) at the cost of high reliability (?) 21

22 Medium power parameters? 22

23 ESS technology on the ADS roadmap Finding #5: The missions for Accelerator Driven Sub-critical (ADS) technology lend themselves to a technology development, demonstration & deployment strategy in which successively complex missions build upon technical developments of the preceding mission. U.S. Dept. of Energy White Paper (2010) [**50] < 1 ESS [**50 ma in 2.9 ms pulses at 14 Hz] 23

24 Sustainability World Thorium Resources Country Australia India USA Norway Canada South Africa Brazil Other countries World total Reserve Base (tons) 340, , , , ,000 39,000 18, ,000 1,400,000 Known Thorium reserves are more than sufficient for millenia of significant power production. India, Australia, Canada, U.S., Norway have lots of Thorium. More will be found Thorium has been of little interest, so far Source: U.S. Geological Survey, Mineral Commodity Summaries, January

25 ThEC10 First Thorium Energy Conference, ThEC10, London Bring thorium communities together: Mining & nuclear industries, NP, HEP, accelerator science, reactor engineering, chemistry, patent law, venture capital, private individuals,... Both solid fuel and Molten Salt Reactors were discussed, both of them with and without accelerator drivers. All 4 options remained viable at the end of the workshop. 25

26 The public case One speaker was Stephen Tindale, - ex-executive Director of Greenpeace UK - advocate of nuclear power as green. Q: How to make a public case for thorium? A1: Emphasize 2 advantages 1) Carbon dioxide and other waste reduction 2) Elimination of weapons grade material A2: De-emphasize 3 advantages, even though true 3) Vast thorium resources outweigh Uranium (ore) 4) Lower cost (if true) 5) Reduced need for renewables: wind, solar, bio-mass. 26

27 Molten Salt Reactors The MSR proponents dominated at ThEC10, with many activities in Japan, the U.S., and France. The enthusiastic proponents were (IMHO) too willing to brush aside legitimate questions: - corrosion issues - potential for irrecoverable leak scenarios. It may be possible to show (now or later) that these issues are not relevant or major. But they must be taken seriously and thoughtfully, especially when raised by a friendly audience 27

28 Aker ADSR Aker Solutions (now Jacobs) propose a 0.6 GWe full scale solid fuel thorium power station driven by an accelerator, - nominally 4 or 5 MW total power - dual 1 GeV CW superconducting linacs, ~200 m long. First implementation was suggested for Aker uses k = 0.995, even though k wanders over a peak-to-peak range of 0.03 during a fuel cycle. The difference is compensated by using control rods Q: So why use an accelerator? 28

29 Why use an accelerator? A1: (Specific) For rapid load following/balancing - a smart grid reacts when the wind stops blowing or clouds obscure solar panels. A2: (General) To provide neutrons on demand - Turn off, up, or down very quickly - Tailor the neutron spectrum (?) - Thus accelerators have 3 Thorium related uses: 1) Transmute waste 2) Breed U-233 3) Help generate electric power Q2: How much more responsive are ADSRs? - A high-level controls modeling problem? - Aker addresses this in a recent patent with Rubbia? 29

30 ThEC11 New York City next week 30

31 An emerging U.S. perspective? 31

32 Office of Science White Paper Sept 2010 Nuclear engineering Project-X SNS MYRRHA

33 DOE White Paper findings Finding #1: There are active programs in many countries, although not in the U.S., to develop, demonstrate and exploit acceleratordriven systems technology for nuclear waste transmutation and power generation. Finding #2: Accelerator-driven sub-critical systems offer the potential for safely burning fuels which are difficult to incorporate in critical systems, for example fuel without 238U or 232Th. Finding #3: Accelerator driven subcritical systems can be utilized to efficiently burn minor actinide waste Finding #4: Accelerator driven subcritical systems can be utilized to generate power from Thorium-based fuels

34 Less stringent reliability Finding #6: Recent detailed analyses of thermal transients in the subcritical core lead to beam trip requirements that are much less stringent than previously thought; while allowed trip rates for commercial power production remain at a few long interruptions per year, relevant permissible trip rates for the transmutation mission lie in the range of many thousands of trips per year with duration greater than one second. 34

35 Linacs!? Finding #7: For the tens of MW beam power required for most industrial-scale ADS concepts, superconducting linear accelerator technology has the greatest potential to deliver the required performance. {Peggs: Many linac labs on the committee??} Finding #8: One of the most challenging technical aspects of the ADS accelerator system, the Front-End Injector, has demonstrated performance levels that meet the requirements for industrial-scale systems, although reliability at these levels has not yet been proven.

36 Technology is advancing Finding #9: Superconducting radio-frequency accelerating structures appropriate for the acceleration of tens of MW of beam power have been designed, built and tested; some structure types are in routinely operating accelerator facilities. Finding #10: Ten to one-hundred fold improvements in long-duration beam trip rates relative to those achieved in routine operation of existing high power proton accelerators is necessary to meet industrial-scale ADS application requirements.

37 Empirical reliability Empirical evidence (ISIS, LANSCE, PSI, SNS) suggests a universal power law for cumulative probability distribution of trip rate vs. trip length - exponent of ~ -2/3 for trips of less than one day in duration. D.Findlay & C.Plostinar, 2010 J.Galambos et al, CPL04, (Also see comments by R.Seviour) 37

38 14 years is a long time Finding #11: The technology available to accelerator designers and builders of today is substantially different from, and superior to, that which was utilized in early ADS studies, in particular in the design which was considered in the 1996 National Research Council report. Finding #12: Spallation target technology has been demonstrated at the 1-MW level, sufficient to meet the Transmutation Demonstration mission. 38

39 Full power generation Beam power for 0.8 GWe ADS Aker quote k = 0.995! ESS

40 Targets & Reliability Finding #13: With appropriate scaling at each step along a technology demonstration path, there are no obstacles foreseen that would preclude the deployment of spallation targets at a power level (10 to 30 MW) needed to meet the application of ADS at an industrial scale. Finding #14: Technology is sufficiently well developed to meet the requirements of an ADS demonstration facility; some development is required for demonstrating and increasing overall system reliability.

41 Technology readiness

42 Summary 42

43 Summary 1. The European Spallation Source will be built in Lund. 2. The design will ensure a long life with many upgrades. 3. The accelerator design, prototyping & construction is being performed in a collaboration. 4. The energy aspects of the accelerator complex are very important. 5. We look forward to welcoming more collaborators to ESS! Many thanks to all members of the emerging ESS accelerator collaboration, and to SNS! 43

44 Office of Science White Paper Finding #15: For Industrial-Scale Transmutation requiring tens of MW of beam power many of the key technologies have been demonstrated, including front-end systems and accelerating systems, but demonstration of other components, improved beam quality and halo control, and demonstration of highly-reliable sub-systems is required. 44

45 There is only one Thorium boat! Fuel cycle: solid or molten? Accelerator: cyclotron, synchrotron, FFAG, linac, NONE? Expectations: beware of giddy enthusiasm Gunfire: shoot out of the big tent, not into it! 45

46 Finis "The transformation of waste is perhaps the oldest pre-occupation of man." Patti Smith, 25th Floor. 46