1 - IAEA Nuclear Data Services

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About 100 special standard sources were prepared for
other laboratories, especially sets of ^-standards
with energies below 500 keV and a-standards with accuracies
of about 0.1%.
Improvement and Development of Counting Methods
A series of interchangeable counters, especially with
Si(Li)- and Ge(Li)-detectors has been constructed for
all kinds of high accuracy coincidence counting.
Various investigations have been performed, in order
to increase the accuracy of activity measurements:
the sorption in pipettes used for source preparation
has been shown to be below 0.01%; Inox wires have
been proved to be superior to nearly all other materials
for anodes, of gas counters with high ionization densities;
comparison of ZnS- and plastic detectors lead to
an extrapolation method for a-spectra in a-low-geometry
counting, which assures an accuracy of better than 0.1%
for this method; the Y-efficiency of p-gas-counters
was reinvestigated and the problems, not recognized
before, solved; optimum conditions for the liquid
scintillation counting of U were found; a special
coincidence-anticoincidence method for liquid scintillation
counting of low beta energy emitters was developed,
etc. r26K27![28]r29].
241
The possibilities for monitoring pure Pu have been
investigated, using liquid scintillation, windowless
flow counter and plastic scintillation techniques.
Most previously used methods were unsatisfactory.
Therefore a coincidence counter with two photomultipliers
connected to one plastic detector for the measurement
of solid probes and a new coincidence-anticoincidence
liquid scintillation technique for liquid
samples were developed. Both methods gave very satisfactory
results.