Tritium assay in materials by the bremsstrahlung counting method

To estimate depth profiles and the amount of tritium captured in materials, the applicability of a bremsstrahlung counting method was examined. Two kinds of materials were used as model samples. One was a tritium source made of an organic polymer and the other was a disk of ZrNi-alloy containing tritium. For both samples, bremsstrahlung X-ray spectra showed a single broad peak. The maximum intensity of each peak appeared at ∼7–8 keV. The intensities were 19 counts s−1 for the polymer source and 240 counts s−1 for the ZrNi disk. To evaluate the detection depth, the observed spectra were compared with those by numerical analysis. The spectral shape and peak position obtained by computer simulation agreed quite well with those of the spectrum observed for the polymer source, whereas for the ZrNi disk, a significant difference was observed at the higher energy side of the peak. The difference could be attributed to the superposition of bremsstrahlung and characteristic X-rays arising from nickel. The detection depth was determined to be ∼1 mm for a polymer source consisting mainly of carbon atoms, and ∼0.1 mm for the ZrNi disk. The present method is highly promising for non-destructively measuring tritium captured deep in materials and to estimate tritium concentration profiles.