A simple method for the determination of uranium and thorium by delayed neutron counting is described. One portion of the
sample is irradiated in a reactor and the delayed neutrons are counted. Another portion of the sample is mixed with B4 C powder absorbing the thermal neutrons, and irradiated in the same position. From those data, both uranium and thorium can
be calculated when a quantitative calibration has been made beforehand. The detection limits for the pure elements are 0.07
ppm for uranium and 2 ppm for thorium with the minimum analyzing time being 2 min. The accuracy of the method is investigated
by comparing results obtained by the method described here with results obtained by epithermal activation analysis.
A reactor neutron activation analysis procedure for the determination of the silver content of silver coins is described. The samples are irradiated for 1 s, cooled for 85 s and measured for 60 s with a Ge-detector. The analysis is based on the measurement of110Ag and108Ag. Aluminium is used for flux monitoring and pulse pile-up correction. A calibration curve is prepared by irradiating and measureing a series of discs with known silver contents. An average precision of ±2.1% is obtained. The analysis of coins with known silver contents shows good agreement with the given values. The analysis time is 2.5 minutes per sample.
A method for the neutron activation analysis of arsenic, selenium and antimony has been developed. A radiochemical separation
is performed by distillation followed by precipitation of the individual elements. Selenium and arsenic are precipitated by
reduction to the elemental form while antimony is precipitated as sulfide. The chemical yields and detection limits using
0.5 g samples are the following: As 90–100%, 0.4 ppb, Se 80–100%, 8 ppb and Sb 50–70%, 0.2 ppb. Results from the analysis
of nine international biological standard samples are given.
The results of a literature survey on non-radiometric analytical techniques for the determination of long-lived radionuclides are described. The methods which have been considered are accelerator mass spectrometry, inductively coupled plasma mass spectrometry, thermal ionization mass spectrometry, resonance ionization spectrometry, resonance ionization mas spectrometry and neutron activation analysis. Neutron activation analysis has been commonly used for the determination of129I and237Np in environmental samples. Inductively coupled mass spectrometry seems likely to become the method of choice for the determination of99Tc,237Np and Pu-isotopes. The methods are discussed and the chemical separation methods described.
Neutron activation analysis methods for the determination of impurities in zirconium cladding material and uranium oxide are described. Detection limits for the elements Al, Cd, Cr, Co, Cu, Hf, Fe, Mn, Ni, W and U in zirconium are below that required by the ASTM B 352-79 standard. The method has been tested on the NIST SRM 360a Zircaloy-2 from which the elements Na, Mg, Al, Ca, V, Cr, Fe, Co, Ni, Cu, Eu and U have been detected. The values for Cr, Fe, Ni and Cu are compared with the certified values. A method for the pre-irradiation separation of the elements Mg, Na, Al, K, Sc, Ca, V, Mn, Cr, Fe, Co, Cu, Zn, Rb, Zr, Cd, Cs, REE and Hf from uranium has been developed. A neutron activation analysis method for the determination of those elements in uranium is described. The method is tested by the analysis of the IAEA reference sample SR-54/64. The elements Al, Mn, V, Cu, Cr, Co, Ni and Fe have been detected and the results compared with the certified values.
An INAA procedure for routine analysis of rock samples is described. Samples are irradiated using a rotating sample holder.
Measurement of the induced gamma activity is performed using an automatic gamma spectrometer and the elemental concentrations
are calculated by a computer. The analytical error is discussed and the precision and accuracy evaluated experimentally. An
average error of ±3–5% without considering counting statistics is obtained. Results for 19 elements in 8 international standard
rocks are reported. A short discussion of the cost of the analysis is included.
A computer program for calculating activation analysis results is described. The program comprises two gamma spectrum analysis
programs, STOAV and SAMPO and one program for calculating elemental concentrations, KVANT. STOAV is based on a simple summation
of channels and SAMPO is based on fitting of mathematical functions. The programs are tested by analyzing the IAEA G-1 test
spectra. In the determination of peak location SAMPO is somewhat better than STOAV and in the determination of peak area SAMPO
is more than twice as accurate as STOAV. On the other hand, SAMPO is three times as expensive to use with a Cyber 170 computer
A simple method for the radiochemical neutron activation analysis of bromine in rock samples is described. The irradiated
samples are ignited in an induction furnace in a flow of air for four minutes. The bromine expelled is collected onto activated
charcoal which is measured using a Ge(Li) detector. The yield of the chemical separation is 85–100% and the detection limit
is 7 ppb. The method is discussed and results for the analysis of 14 USGS standard rock samples are presented.