Advanced applications of diagnostics techniques to fusion reactor materials

He bubble growth in a martensitic steel for fusion reactors

“…The experimental observation of these bubbles using transmission electron microscopy (TEM) is difficult because of their tiny sizes, generally around 10 Å, and because of the fact that these steels are magnetic. Small-angle neutron scattering (SANS) is therefore an appropriate technique to investigate this phenomenon, as also shown by previous studies (Albertini, Coppola & Rustichelli, 1993).…”

Recent applications of small-angle neutron scattering in the characterization of irradiated steels for nuclear technologies

“…Assuming that the helium concentration is equal to the nominal value (400 appm), the obtained variations on (Dq(R)) 2 range typically from À10% at 2 Å to +12% at 100 Å. The resulting variations in N(R) are generally of a few per cent, therefore well inside the statistical uncertainty band determined in previous work [10,11] where it had been assumed that ðDqÞ 2 ¼ ðq He À q F82H Þ 2 ¼ 4:833 Á 10 21 cm À4 [3]. The variable contrast function determined in this way has been included in the iterative procedure described in Section 2 to determine the distributions but without unphysical oscillations (which can be produced by an excessive number of splines).…”

“…The dependence of the contrast on the bubble radius was taken into account following the fitting procedure reported in [14,15], although given the small value of q He ¼ 0:588 Á 10 10 cm À2 [3], very large changes of the helium mass density would be necessary to lead to significantly different distributions. Assuming that the helium concentration is equal to the nominal value (400 appm), the obtained variations on (Dq(R)) 2 range typically from À10% at 2 Å to +12% at 100 Å.…”

“…Reviews of experimental work carried out in this area can be found in Refs. [1][2][3]. SANS allows in fact to non-destructively investigate massive samples, to distinguish non-magnetic and magnetic defects (such as some kind of precipitates), to detect light elements, including hydrogen.…”