Research Needs for Magnetic Fusion Energy Sciences - US Burning ...

dose fusion-relevant environment with accompanying high he and h generation from nuclear
transmutations is unknown. because he substantially affects bulk properties, it is essential to
carefully quantify its effect in order to develop a safe and reliable fusion power system. The figure
above illustrates how he bubbles on grain boundaries can cause severe embrittlement at high
temperatures. Therefore, a fusion-like neutron source is absolutely essential to generate a bulk
materials property irradiation database necessary for design, construction, licensing, and safe
operation of next-step fusion nuclear devices and fusion power plants.
exploring the simultaneous effects of neutron displacement damage and he production by transmutations
on a wide range of materials requires a fusion relevant neutron source. This is the conclusion
of various high-level international assessments. The number of he atoms produced divided
by the number of atoms displaced (he/dpa ratio) is an important fusion relevant attribute. The
need to generate a database of environment-specific material properties is consistent with experience
in all previous nuclear and other safety-sensitive nonnuclear technologies. There are several
options for creating fusion-relevant neutron irradiation conditions, such as the proposed international
Fusion materials irradiation Facility, the materials test station, and the dynamic trap neutron
source. consequently, a key activity in this Thrust element is to carefully evaluate the various
options and select the most technically attractive and cost effective approach or combination of approaches.
key criteria for a fusion relevant neutron source include flux, test volume and operational
availability sufficient for accelerated testing to end-of-lifetime doses in a reasonable time. more
specifically ≥0.5 liter volume with ≥2 mW/m 2 equivalent 14 mev neutron flux to enable accelerated
testing up to at least 10 mWy/m 2 (with larger volumes at lower neutron fluences for testing larger
components), availability ≥70%, and flux gradients ≤20%/cm. These criteria will form the basis to
evaluate the various options for conducting materials irradiation studies. selections will be made
that balance the need to obtain relevant bulk material property information with the cost, schedule
and potential for international participation to leverage investments by the Us.
a later possibility might be to include a provision for materials irradiation capabilities as part of a
large-scale nuclear facility such as the proposed Fusion nuclear science Facility. however, it must
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Figure 2. He bubbles on grain boundaries
can cause severe embrittlement at high
temperatures.