SUPPRESSION OF HE-3 BUBBLE FORMATION BY IMPURITIES IN TRITIDES - SWELLING OF THE DILUTE ALLOY NBO0.015 T0.01-X HE-3(X)

Swelling at ambient temperature of a NbO0.015 solution containing 1% ( T/M) of tritium was investigated using strain gauges for a period of a pproximately 1 year. In this case, the observed swelling rate resultin g from tritium decay to He-3 is significantly lower than found in prev ious work on undoped Nb containing tritium in the alpha-phase, but som ewhat above the values found at low temperatures where He-3 is immobil e. This effect is attributed to the trapping of He-3 atoms by the rand omly dissolved O-atoms which suppresses bubble formation but results i n a fine dispersion of small He-3 clusters attached to the trapping ce nters. The experimental observations are discussed in terms of an impe ded diffusion of He-3 interstitial atoms and a correspondingly enhance d He-3 cluster nucleation efficiency.