The Materials Test Station: An Accelerator Driven Neutron Source for Fusion Materials Testing

1. The Materials Test Station:An Accelerator Driven Neutron Source for Fusion Materials Testing Eric Pitcher Presented at: Sixth US-PRC Magnetic Fusion Collaboration Workshop July 10-12, 2012 LA-UR-12-22739

2. The need for a fusion relevant intense neutron source is well established • 2007 FESAC (Greenwald) Report • Identified a neutron irradiation facility as one of nine initiatives • Recommended assessing the potential for alternative facilities to reduce or possibly eliminate the need for the US to participate as a full partner in the International Fusion Materials Irradiation Facility (IFMIF) • 2009 FES Research Needs Workshop (ReNeW) • Advocated a fusion-relevant neutron source to be an essential mission requirement • 2012 FESAC Opportunities for Fusion Materials Science and Technology Research Now and During the ITER Era • “The lack of an intense fusion relevant neutron source for conducting accelerated experiments is the largest obstacle to achieving a rigorous scientific understanding and developing effective strategies for mitigating neutron-induced material degradation.” The LANL Materials Test Station is a moderate cost option that can largely satisfy this mission need.

3. Materials Test Station Mission: Irradiate nuclear fuels and materials in a fast neutron spectrum • The DOE Office of Nuclear Energy (DOE-NE) has funded the conceptual design of the Materials Test Station (MTS) as a fast spectrum nuclear fuels and materials test bed • Once completed, the MTS will be the only fast neutron spectrum irradiation capability outside of Russia and Asia • The MTS can provide the US with a fast spectrum test capability in 4 years for about $85M • The MTS neutron irradiation environment is also suitable for fusion materials testing

4. MTS will be built at the Los Alamos Neutron Science Center (LANSCE), a multidisciplinary National User Facility • Lujan Neutron Scattering Center • Materials science • Biology • Nuclear cross sections • Weapons Neutron Research Facility • Nuclear cross sections • semiconductor testing • Proton Radiography • dynamic imaging • Ultra-Cold Neutron Source • nuclear physics • Isotope Production Facility • medical & research isotopes • Materials Test Station(under design) • fuels and materials testing UCN MTS LujanCenter pRad WNR IPF H+ H–

5. MTS will be built in an existing experimental hall Use of existing materials and infrastructure greatly reduces capital costs compared to a green field The MTS will be driven by a 1-MW proton beam delivered by the LANSCE accelerator

6. MTS neutron flux and energy spectrum is similar to a fast reactor, with an added high-energy tail NEUTRON ENERGY SPECTRUM SPATIAL DISTRIBUTION OF THE FAST NEUTRON FLUX MTS flux level will be half of the world’s most intense research fast reactors.

7. Figures of merit for fusion materials testing • Irradiation temperature • 300˚C to 1000˚C range, controllable to ±10˚C • He/dpa ratio • “Fusion relevant” range is 10 – 15 appm He/dpa • Damage rate • Desirable to reach a total dose exceeding 100 dpa in a few years • Irradiation volume • Sufficient to simultaneously irradiate hundreds of test specimens • Nuclear recoil spectrum similar to fusion reactor 1st wall • Similar evolution in elemental composition with dose With the exception of damage rate, the MTS substantially satisfies these figures of merit.

8. Peak dpa rate is 32 dpa/fpy or 17 dpa/year (50% LANSCE availability) There is an irradiation volume of about 100 cm3 where samples will receive 7 dpa/year or more with fusion-relevant He/dpa ratios MTS produces a broad range of He/dpa ratios fuels irradiation region “fusion relevant”He/dparatio from 10 to 15 appm/dpa materials irradiation region

9. Different facilities exhibit distinct features in their neutron and nuclear recoil energy spectra (DEMO) Low-energy portion of the neutron and nuclear recoil spectra are similar for fusion reactor, fast reactor, and MTS.

10. The damage production function W(T) of a fusion reactor 1st wall and MTS match in the critical region below 50 keV Isolated defectswith higher rate of survivability Sub-cascade production

11. Major elemental composition evolution in MTS is similar to that for a fusion reactor first wall reflector materials samples proton beam spallation target backstop fuel samples mask proton beam spallation target materials samples reflector materials region tally volumes EUROFER97 irradiated to 200 dpa

12. Summary • The irradiation environment in MTS is appropriate for fusion materials testing of steel alloys with respect to: • irradiation temperature • He/dpa ratio • nuclear recoil spectrum • change in elemental composition with dose • Peak damage rate for iron alloys is 17 dpa/calendar year • Irradiation volume is sufficient for the simultaneous irradiation of hundreds of miniature test specimens • Conceptual design completed last year, awaiting DOE approval • MTS provides the US a cost effective alternative to joining the ITER Broader Approach