M. Derbyshire et al., Preparation of two uranium glass reference materials for fission-track dating of geological samples, RADIAT MEAS, 34(1-6), 2001, pp. 419-422
The European Commission produced and certified uranium glass for fission-tr
ack dating in 1996 (Reference Material IRMM-540). This material is now out
of stock and a project for the preparation of two new reference glasses is
underway. The new glasses, containing nominally 15 and 55 mg kg(-1) uranium
, were prepared from blended oxide powder, and cast using an improved metho
d, which minimised micro-scale defects and optimised the yield. Glass rods
were produced which were then cut into discs of 2 mm thickness and 15 mm di
ameter and subsequently polished.
Uranium homogeneity and fission-track stability are critical properties of
the glass. An extensive study was carried out to verify the homogeneity by
fission-track counting, investigating both within-disc and between disc eff
ects, and to investigate potential track fading due to thermal annealing, N
o evidence of uranium heterogeneity was detected. The stability study, usin
g an "isochronous" method, in which all measurements are made at the end of
exposure to artificial ageing, is still underway.
The reference material will be certified for isotopic composition (natural)
, uranium mass fraction and neutron fluence (one disc out of each set of th
ree will be irradiated, together with a mica foil, to induce fission tracks
in a certified fluence). The reference materials will be released as IRMM-
540R (15 mg kg(-1) U) and IRMM-541 (55 mg kg(-1) U). (C) 2001 Elsevier Scie
nce Ltd. All rights reserved.