An assessment of the available alternatives for fusion relevant neutron sources

Abstract

The discovery of void swelling in neutron-irradiated stainless steels by Cawthorne and Fulton in 1966 showed that radiation effects would seriously affect the lifetime of fission reactors. A few years later, in the early 1970s, serious damage levels were observed in core components of the first commercial fission reactors that had been in operation for one decade. Driven by the harder neutron spectrum, the fusion community was impelled to explore the technical possibilities to make available a fusion relevant neutron source to anticipate the difficulties faced by the fission reactors community and ensure the long-term operation of a fusion reactor. In 1976, the conclusions of the first review published announced the assets and drawbacks of the different possibilities, which today despite the four decades passed and the sound technological advancements, continue being basically the same. A suitable neutron spectrum can be theoretically obtained both from plasma-based or accelerators based facilities with either gas, liquid or solids targets. Needed facilities performances, available irradiation volumes that the concept allow and cost are at stake. In the past, the cost of the most promising facility based on stripping the neutron from a deuteron on a lithium target was misleadingly peered with that of a fusion reactor. A tokamak with sufficient volume to irradiate equipment under fusion relevant conditions will be likely available in the future once commercial fusion reactors have become a reality; unfortunately, this concept does not match the needs timely, and is unrealistic w.r.t. its costs nowadays with worldwide efforts prioritizing ITER. In this article, we will focus on the technical aspects and assess the present maturity of different existing possibilities based on nowadays technologies to count with neutrons at a suitable flux and spectrum to characterize and qualify fusion materials to be timely ready with our world fusion roadmaps.

Recent technical progress on BA Program: DEMO activities and IFMIF/EVEDA

“…The concept being initially proposed in 1976 [20] has been continuously developed worldwide until the present maturity, ready for construction, thanks to the successful on-going accomplishment of the Engineering Validation and Engineering Design Activity (EVEDA) phase of the International Fusion Materials Irradiation Facility (IFMIF) project under the frame work of the BA Agreement, signed in February 2007 between the Japanese Government and EURATOM. Whereas the Engineering Validation Activity (EVA) phase has involved three major prototypes to validate the continuous operation of the facility: (1) the Linear IFMIF Prototype Accelerator (LIPAc) under installation in Rokkasho, the world highest beam average current linac; (2) the EVEDA Lithium Test Loop (ELTL) in operation in Oarai until November 2014, the world biggest liquid lithium loop; and (3) the High Flux Test Module constructed in KIT, cooled with He in the HELOKA loop (details of all the validation activities that is wider than the aforementioned major prototypes can be found elsewhere [21]), in turn the Engineering Design Activity (EDA) phase was successfully accomplished within the allocated time [22]. IFMIF [23] will consist of two 125 mA deuteron accelerators operating in CW (Continuous Wave, i.e.…”

“…In turn, the parallel activities related with the EVA phase aimed at validating the continuous and stable operation of each IFMIF subsystem. The design of the constructed prototypes part of the validation objectives: the accelerator facility, the target facility and the test facility were expected to be incorporated following their successful operation, which counted with a 9 MeV 125 mA CW deuteron linac, the world largest lithium loop at nominal operational conditions and full scale prototype of High Flux Test Module with its small scale test technique specimens inserted in the prototype capsules [22]. The time allocated for such an ambitious mandate was of 6 years, from the entry into force of the Agreement in June 2007.…”

“…Delays in the program were unavoidable. However, the Engineering Design Activities accomplished its scope on schedule delivering in June 2013 the IFMIF Intermediate Engineering Design Report (IIEDR), which was adopted by the BA Steering Committee following the recommendation by an ad-hoc committee formed by top multidisciplinary Japanese-European scientists, who emitted positive conclusions on its quality and achievement of objectives [22]. The design proposed in what concerns the target facility and test facility has been validated with the successful accomplishment in 2015 of all its objectives.…”

“…The IIEDR consists of 5 major sections: (1) an "Executive Summary", where the status of the validation activities at the time of the release is described [22]; (2) the "IFMIF Plant Design Description" (PDD), that digests the content of the full IIEDR consisting of more than 100 technical reports; (3) a careful cost and schedule report, incorporating the experience gained with the prototypes during the EVA phase and the help of Japanese and European engineering companies; (4) annexes to the PDD; and (5) 34 detailed design description documents of all the sub-systems supporting the PDD. A brief description of IFMIF follows.…”

Ion Beam Experiments to Emulate Nuclear Fusion Environment on Structural Materials at CMAM

“…Current neutron sources with an energy spectrum typical of fusion reactions (14 MeV neutrons) are far from the fluence expected in a fusion reactor, and they are only useful for a few cases involving functional materials not exposed to high radiation doses [8,9]. Therefore, a common approximation to test fusion materials consists of using ion irradiation to emulate the effects of neutron irradiation [10].…”