International Fusion Materials Irradiation Facility

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The International Fusion Materials Irradiation Facility ( IFMIF ) is a research facility that has been planned since the 1990s to test materials for their suitability for use in potential fusion reactors . In a fusion reactor, a large number of neutrons hit the wall material with very high energy. In order to be able to examine the damage caused by this load and to be able to compare it with calculations, IFMIF is to use a particle accelerator to generate a high neutron flux with corresponding particle energy. It is a joint project of the EU , Japan , Russia and the USA under the auspices of the International Atomic Energy Agency .

The project is currently (2020) in the so-called Engineering Validation and Engineering Design Activities (EVEDA) phase. With regard to the location of this international plant, the European agency Fusion for Energy (F4E) assessed the joint proposal by Spain and Croatia to set up IFMIF-DONES ( DEMO Oriented NEutron Source ) in Granada as positive in December 2017 .

Material problem of fusion reactors

Some structural parts of the reactor must - in addition to high thermal loads - withstand high neutron loads for a sufficiently long time (e.g. two years). In the case of steel, for example, the dislocation damage that accumulates during this downtime is in the "first wall", i.e. the blanket parts bordering the fusion plasma , in the order of 50 dpa ( displacements per atom , displacements per atom) Atom). A similarly important type of damage is the development of gas (hydrogen and helium) through neutron reactions in the material (see reactor materials ).

So far, these loads can only be incompletely simulated experimentally. Neutron irradiation in high-flux research reactors is of only limited use because the energy spectrum of the neutrons does not go as high as in the fusion reactor. Experiments with self-implantation - ions of the target material are shot at the same material with high energy, for example tungsten ions on tungsten - result in dislocations, but not the simultaneous evolution of gas. Several studies have shown that none of the previously common neutron source types is suitable.

However, materials whose strength properties are still sufficient after the damage mentioned cannot be developed under realistic conditions without irradiation tests. A test fusion reactor like ITER does not offer these conditions either, because it will not run continuously, but rather in relatively short experimental phases with interim conversion breaks. However, the structural material to be developed should already be available for the construction of the DEMO prototype power plant , i.e. at the end of the ITER's useful life.

IFMIF concept

IFMIF target with accelerator beams and test cell

Neutron source

In order to create a suitable neutron source with today's technology, IFMIF is to use neutrons that are triggered by fast deuterons in lithium . Two parallel high-current linear accelerators each deliver a deuteron beam of 40 MeV and a high current of 125 milliamps; the two beams overlap on the target , a 2.5 cm thick layer of flowing, liquid lithium. In this layer the deuterons are completely stopped. The lithium is pumped through a cooler in a closed circuit in order to dissipate the inevitable high heat output. With the high deuteron energy, the neutrons are mainly released by the (d, n) stripping reaction. They therefore do not emerge isotropically , but preferentially to the front of the target. The test cell with the irradiation samples is located there.

A prototype of the high-current accelerator is under construction in Rokkasho (Japan).

The shape of the neutron energy spectrum measured in a cyclotron experiment differs significantly from the fusion reactor spectrum, but it can be compared well with it in terms of material damage.

Test cell

The test cell is divided into a high flow zone of 500 cm 3 close to the target, a larger medium flow zone behind and an even larger low flow zone. According to calculations, 20 to 55 dpa (depending on location) per year of irradiation are achieved in iron materials in the high flow zone. It is intended to accommodate miniaturized structural material samples. In the medium and low flow zones, for example, neutron multiplier and breeding materials (see blanket ) can be tested. Since months and years of irradiation are necessary, the test cell needs a powerful cooling system that can also be quickly switched to heating in order to be able to keep the temperature of the samples constant in the event of an unexpected failure of the accelerator.

The structural materials to be tested include the low-activation steels currently being developed, but z. B. also CFC ( carbon fiber carbon composite , carbon fiber reinforced carbon ), SiC / SiC (silicon carbide fiber reinforced silicon carbide) and tungsten as material for divertor plates .

literature

About the accelerator:

  • A. Mosnier, PY Beauvais, B. Branas et al .: The accelerator prototype of the IFMIF / EVEDA project. Proceedings of the International Particle Accelerator Conference , Kyoto, Japan, 2010, pp. 588-590.

To the test cell:

  • A. Möslang, V. Heinzel, H. Matsui et al .: The IFMIF test facilities design. Fusion Engineering and Design Volume 81 (2006) pages 863-871

About the lithium target:

  • H. Nakamura, P. Agostini, K. Ara et al .: Status of engineering design of liquid lithium target in IFMIF-EVEDA. Fusion Engineering and Design Volume 84 (2009) pages 252-258

Individual evidence

  1. ↑ J. Knaster, F. Arbeiter, P. Cara et al .: IFMIF, the European-Japanese efforts under the Broader Approach agreement towards a Li (d, xn) neutron source: Current staus and future options. Nuclear Materials and Energy , Volume 9 (2016) pages 46–54
  2. ↑ T. Muroga, A. Möslang, E. Diegele: User's perspective on D-Li neutron sources (A-FNS and IFMIF-DONES) for DEMO and beyond. Journal of Nuclear Materials Volume 535 (2020) Art. No. 152 186
  3. ↑ J. Knaster, A. Ibarra, J. Abal et al .: The accomplishment of the engineering design acticities of IFMIF / EVEDA: the European-Japanese project towards a Li (d, xn) fusion relevant neutron source. Nuclear Fusion Volume 55 (2015), 08603 [1]
  4. Jump up ↑ A. Ibarra, R. Heidinger, P. Barabaschi, F. Mota, A. Mosnier, P. Cara, FS Nitti: A Stepped Approach from IFMIF / EVEDA Toward IFMIF. Fusion Science and Technology Volume 66 (2017) pp. 252-259, DOI: 10.13182 / FST13-778
  5. ↑ https://ifmifdones.org/about-dones/concept-and-mission/
  6. ↑ S. Zinkle and A. Moeslang, Evaluation of irradiation facility options for fusion materials research and development, Fusion Engineering and Design 88 (2013) 472-482
  7. ↑ P. Vladimirov and A. Moeslang, Comparison of material irradiation conditions for fusion, spallation, stripping, and fission neutron sources, Journal of Nuclear Materials 33 (2004) 329-340
  8. ↑ P. Cara, R. Heidinger, S. O'hira u. A .: The linear IFMIF prototype accelarator (LiPAc) design development under the Europea-Japanese collaboration. Proceedings of IPAC2016 , Busan, Korea (2016)
  9. ↑ S. Ishida ∗, A. Kasugai, K. Sakamoto, P. Cara, H. Dzitko: Progress of IFMIF / EVEDA Project and Prospects for A-FNS . doi: 10.18429 / JACoW-SRF2019-MOP047 (2019)
  10. ^ [2] Website of the IFMIF work in Rokkasho
  11. ↑ U. v. Möllendorff, F. Maekawa, H. Giese, H. Feuerstein: A nuclear simulation experiment for the International Fusion Materials Irradiation Facility (IFMIF) . Research Center Karlsruhe, Report FZKA 6764 (2002)
  12. ^ A b E. Daum, PPH Wilson, U. Fischer and K. Ehrlich: Characterization of the irradiation parameters in the IFMIF high flux test region. Journal of Nuclear Materials Vol. 258-263, pp. 413-420 (1989)
  13. ↑ AAF Tavassoli, E. Diegele, R. Lindau, N. Luzginova, H. Tanigawa: Current status and recent research achievements in ferritic / martensitic steels. Journal of Nuclear Materials Volume 455 (2014) pages 269-276
  14. ↑ W. Wang, S. Liu, G. Xu, B. Zhang, Q. Huang: Effect of thermal aging on microstructure and meechanical properties of China Low-Acivation Martensitic Steel at 550 0 C. Nuclear Engineering and Technology Volume 48 (2016 ) Pages 518-524

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