TRITIUM ASSAY IN MATERIALS BY THE BREMSSTRAHLUNG COUNTING METHOD

To estimate depth profiles and the amount of tritium captured in mater ials, the applicability of a bremsstrahlung counting method was examin ed. Two kinds of materials were used as model samples. One was a triti um source made of an organic polymer and the other was a disk of ZrNi- alloy containing tritium. For both samples, bremsstrahlung X-ray spect ra showed a single broad peak. The maximum intensity of each peak appe ared at similar to 7-8 keV. The intensities were 19 counts s(-1) for t he 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 c omputer simulation agreed quite well with those of the spectrum observ ed for the polymer source, whereas for the ZrNi disk, a significant di fference was observed at the higher energy side of the peak. The diffe rence could be attributed to the superposition of bremsstrahlung and c haracteristic X-rays arising from nickel. The detection depth was dete rmined to be similar to 1 mm for a polymer source consisting mainly of carbon atoms, and similar to 0.1 mm for the ZrNi disk. The present me thod is highly promising for non-destructively measuring tritium captu red deep in materials and to estimate tritium concentration profiles. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.