The IFMIF-DONES project: a neutron source for fusion-like materials testing

Irradiation environment in the future Fusion Power Plants (and obviously also in DEMO independently of its specific design) is characterized by the presence of 14 MeV fusion neutrons in the first wall area. Understanding the degradation of the materials and components properties throughout the reactor operational life is a key issue to allow the design and subsequent facility licensing by the corresponding safety authorities.

This understanding can only be produced in an irradiation facility, and there is general consensus that the available (fission, spallation and ion beam) irradiation sources do not have the proper characteristics to fulfill the observed needs [1]. Although all the different types of irradiation experiments are being used and must continue to be used in the future in order to improve the basic understanding of radiation effects in materials, the need of a dedicated fusion neutron facility has been widely identified by the fusion materials community more than 30 years ago and confirmed along the time.

The main requirement for this neutron source is to produce fusion characteristic neutron spectrum with enough intensity to allow accelerated testing, up to a level above the expected operational lifetime, with an irradiation volume large enough to allow the characterization of the macroscopic properties of the materials of interest required for the engineering design of DEMO and the Power Plant. The need of a fusion relevant neutron source was clear from the start of the nuclear fusion developments. Intense discussions over the years concluded in the consensus driven by the material scientist community that an accelerator-based source utilizing deuteron-lithium nuclear reaction with a broad energy spectrum peaked at around 14 MeV would be the best choice for a materials irradiation facility [2] .The International Fusion Materials Irradiation Facility (IFMIF) was proposed to be such dedicated facility. IFMIF can achieve all these targets using two 40 MeV deuteron linear accelerators, each delivering a 125 mA beam current with 100% duty cycle. Both beams strike a liquid lithium jet as a target, thus providing an intense neutron flux density of about 1018 n/m2s with a broad energy peak near 14 MeV.

IFMIF design and engineering validation has been developed since 1990. Since 2006 it was agreed to address the so-called Engineering Validation and Engineering Design (IFMIF/EVEDA) phase as one of the main three projects of the Bilateral Agreement between EU and Japan for the Broader Approach (BA) to Fusion.

IIED Report

In this framework, the IFMIF/EVEDA project produced in 2013 the “IFMIF Intermediate Enineering Design Report”, an intermediate IFMIF engineering design for a generic site. The IIED Report assumes that the IFMIF mission is to produce the materials irradiation test data required for the DEMO/Power Plant design, licensing, construction and safe operation. That means that, besides the materials irradiation, the facility must be able to fully characterize the irradiated materials. The IIED Report was produced based on the assumptions and requirements defined by the Users community, i.e. materials scientist and DEMO/Power Plant designers at the beginning of the IFMIF/EVEDA project [4]. Among other requirements, target exposure dose levels up to 150 dpa were identified as required for the materials of the Power Plant.