Thirteen reference materials prepared under the Euratom Working Group on Reactor Dosimetry (EWGRD) monitor materials programme are now available. The determination of trace impurities has recently been completed for rhodium metal (iridium 26.0 ± 0.6 mg·kg−1, platinum < 5 mg·kg−1) and these values will be proposed for certification. Certification analyses of titanium metal, which are continuing, indicate scandium < 0.1 mg·kg−1.
The preparation of alloys for neutron fluence rate measurements are discussed. Satisfactory homogeneity in aluminium alloys can be difficult to achieve on a milligramme scale due to the formation of coarse intermetallic particles, and suitable processing with a high solidification rate, cold working and annealing is essential. The example is given of the alloys Al-15 wt% U and Al-14 wt% Pu, where the inhomogeneity (in terms of relative standard deviation of alloying element) was determined by isotope dilution mass spectrometry as < 0.2% in each case for 20 mg samples.
Some recent examples of dosimeter encapsulation are given including NpO2 and UO2 microspheres in high purity vanadium and Al-Pu and Al-U fission foils in cold-pressed aluminium containers.