Non-destructive examination of roman silver coins by neutron activation analysis

The detection of “plated” specimens (ancient falsifications consisting of a copper core with a silver outer layer) amidst a great collection of silver coins was performed by non-destructive neutron analysis. The “plating” can be detected by measuring the Ag/Cu ratio. In practice it is more convenient to determine the Au/Cu ratio which is proportional to it, A short activation in a low thermal neutron flux is sufficient for this purpose. Consequently the induced activity of the long-lived^110mAg is small. The necessary correction for self-absorption on the measured ratio is small. A series of 2000 coins was analysed in this way.     

Instrumental neutron activation analysis of some ancient punchmark coins from India

A nondestructive instrumental neutron activation analysis technique is applied for the analysis of precious ancient punchmark coins. Coins ranging between 8th century B.C. to 2nd century B.C. were irradiated with thermal neutrons in a²⁵²Cf neutron source facility and analyzed by comparator method of instrumental neutron activation analysis, using high purity germanium detector coupled to a multichannel analyzer, the activities being measured at photopeak energies of the corresponding radioisotopes. It is observed that punchmark coins are mainly of two types: copper or silver based. Other elements present in varying proportions are gold, arsenic and antimony.     

Neutron activation analysis on ancient Greek silver coins and related materials

66 archaic Greek silver coins have been analyzed for the minor elements Cu, Au, Bi and Pb, and for the trace elements Na, Mn, Co, Ni, As, Sn, Sb and Ir. Instrumental neutron activation has been used for the determination of Cu and Au and atomic absorption spectroscopy for Pb and Bi. The trace elements could be detected only after a separation of the interfering matrix activities by an extraction with a diethyl-dithio-carbamate complex. The homogeneity of Au and Cu in the coins and the significance of the trace elements are discussed. The statistical evaluation of the analytical data reveals distinct groups for coins of some provenances.     

Determination of the alloying elements in ancient silver coins

Isotope excited energy dispersive X-ray fluorescence (EDXRF) was used for the determination of the major components, silver and copper, of ancient coins. A ring shaped ¹²⁵I source was used for excitation. Various methods were developed and compared for quantitative evaluation in order to eliminate matrix effects and the effects caused by the differences in geometry. The method proposed by the authors ensures determination with acceptable error using certified standard samples of alloys. The results of this method were compared with those of prompt gamma activation analysis (PGAA) and with data from contemporary written sources.     

Determination of major components and trace elements in ancient silver by thermal neutron activation analysis

Thermal neutron activation of minute samples of ancient silver objects has provided useful information concerning their silver, copper and gold content. The results of such analysis of eighteen Sasanian silver objects are discussed together with consideration of the sampling problems involved. In order to extend these measurements to include other elements, an isotopic exchange system has been developed to separate other activities present in irradiated silver specimens quantitatively from the silver, copper and gold activities. Following exchange with cuprous and silver iodides it has been possible to count quantitatively the activity of fourteen additional elements: As, Br, Co, Cr, Fe, Hg, Ir, K, Mn, Na, Sb, Sc, Se and Zn. Research supported in part by the U. S. Atomic Energy Commission.     

Determination of silver traces in air by neutron activation analysis

A non-destructive system for determination of silver traces in air particulates collected on cellulose filters is described, based on neutron activation followed by¹¹⁰Ag β⁻ counting instead of the 657.7 keV γ-ray. The determination limit (for 10% confidence limit) is estimated to be about 10⁻⁹ g. The method is easily applicable to the determination of silver in cloud seeding experiments, since the filters themselves provide a consistent and fairly uniform source and samples are collected in general far from industrial areas, where the concentration of possible interfering elements in air is reasonably low.     

Determination of silver in biological reference materials by neutron activation analysis

Silver in selected, predominantly biological, reference materials (NIST SRM 1515, 1547, 1549, 1566a, 1571, 1577b, 2704, CTA-OTL-1, and Bowen’s Kale) was determined using neutron activation analysis (NAA) in two different analytical modes: instrumental NAA with epithermal neutrons (ENAA), and NAA with radiochemical separation (RNAA). The ENAA mode was based on long-time 5-hour irradiation of samples in a special Cd lined box with counting after 8-month decay. The RNAA procedure consisted in 20-hour irradiation of samples, their decomposition/dissolution by alkaline-oxidative fusion, and precipitation of AgCl including several purification steps. Both methods provided Ag contents in the analyzed reference materials consistent with certified and/or literature values down to the ng·g⁻¹ level.     

Determination of silver using cyclic epithermal neutron activation analysis

A fast pneumatic transfer facility was installed in Nuclear Engineering Teaching Laboratory (NETL) of the University of Texas at Austin for the purpose of cyclic thermal and epithermal neutron activation analysis. In this study efforts were focused on the evaluation of cyclic epithermal neutron activation analysis (CENAA). Various NIST and CANMET certified materials were analyzed by the system. Experiment results showed ¹¹⁰Ag with its 25 s half-life as one of the isotopes favored by the system. Thus, the system was put into practical application in identifying silver in metallic ores. Comparison of sliver concentrations as determined by CENAA in CANMET certified reference materials gave very good results.     

Multielement instrumental neutron activation analysis of silver-copper coins

Neutron activation, applied to silver and copper based coinage, leads to a measure of the mean concentrations of major and 12 trace elements, even if their distribution is heterogeneous. The drawbacks of this activation method applied to such a matrix are shielding effects and high radioactivity of major elements. Both effects were avoided by accurately calculating the correction coefficients and by choosing the optimal working conditions. Analytical results obtained lead to a better knowledge of the chronology and origin of Armorican protohistorical coinage.     

The rapid determination of silver to silver plus copper ratios in coins using 14 MeV neutron activation analysis

A non-destructive method for the analysis of the silver to silver plus copper ratio in coins using 14 MeV neutron activation analysis has been studied. The mass of silver to the mass of copper is obtained by measuring the 0.511 MeV annihilation radiation emitted by⁶⁴Cu and¹⁰⁶Ag at two separate times after irradiation. A series of British silver three-penny pieces dated 1891–1941 were analysed and agreed well with the mint assay. The interference from the presence of zinc in some coins was investigated.     

Multielement analysis of archaic Chinese bronze and antique coins by fast neutron activation analysis

Samples of archaic bronze have been investigated by fast neutron activation analysis using both the absolute and relative method. The components Cu, Zn, Sn and Pb have been determined quantitatively. For the detection of lead via the short-lived isomeric state^207mPb, cyclic activation and measurement technique was used with pneumatic sample transfer between detector and central irradiation position of the neutron tube. For nondestructive analysis of antique Chinese coins the samples had to be irradiated outside the neutron generator KORONA. The activation reactions, the evaluation of the elemental concentrations and the accuracy of the results are discussed. The data were corrected for -ray self-absorption in the samples and summing of coincident -rays in the detector. According to reported typical compositions of Chinese bronze from different dynasties, the age of the samples has been derived from the results obtained.     

Determination of noble elements in coins by gamma activation analysis

Silver and gold were analysed in coins and medals by inelastic gamma-scattering reaction. The irradiation was performed with a 740 TBq (20 kCi)⁶⁰Co source. After irradiation the isomer activities were measured with a well type NaI(Tl) scintillation counter and evaluated by means of a software program.     

Multielement content of coal by neutron activation analysis techniques

Due to the interaction with components present in natural waters, radionuclides may be present in different physico-chemical forms, varying in size, charge and density. The distribution pattern will influence the transport, mobility and biological uptake of the radionuclides. Size fractionation based on hollow fiber is useful for the determination of the size distribution pattern of radionuclides in natural waters. Furthermore, a continuous mixing and separation system has been developed for the investigation of the association of radionuclides with naturally occurring colloids. Results based on radionuclides in waste water from the Forsmark nuclear power plant, Sweden, will illustrate the potential usefulness of the technique.     

Determination of iron isotopes by neutron activation analysis

Instrumental neutron activation analysis has been applied to the determination of Fe isotopic abundances in iron materials with the experimental accuracy of 5%. The proposed method can be considered as a quite simple and fast quality check system on the iron isotope enriched oxides used as standard in Mössbauer spectroscopy.     

Determination of lithium by instrumental neutron activation analysis

The fast transfer system in the DR 2 reactor for irradiation at a thermal neutron flux density of 10¹³ n·cm⁻²·sec⁻¹ was used for the determination of lithium by the⁷Li(n, γ)⁸Li reaction. β-counting with a large perspex Cerenkov detector begun at 0.3 s after the end of irradiation, and multi-scaler data was accumulated in 300 channels at 0.1 s per channel. With a suitable choice of discrimination level only¹⁶N and background interfere, and the 0.84 s half-life of⁸Li was resolved by the method of weighted least squares. Results are presented for 36 international geochemical reference materials, and for a few biological samples, including BOWEN's kale and the NBS Standard Reference Material 1571 Orchard Leaves.     

Determination of gunshot residues by neutron activation analysis

Systematic investigations of gunshot residues, deposited around the bullet hole, have been carried out. The traces were produced by firing on filter papers from distances of 5 to 200 cm using one rifle and three pistols as arms. Antimony, lead and barium were quantitatively determined after irradiating the samples in the nuclear reactor TRIGA Mainz by measurement of gamma-lines of^122mSb,¹²²Sb,^207mPo and¹³⁹Ba. The determinations were made purely instrumentally and-where the half lives were long enough-also after chemical separation of the nuclides. The amount of the elements were determined in dependence of the firing distance and of the area around the bullet hole.     

Determination of the iron content of aluminate liquors from the Bayer alumina process by neutron activation analysis

The behaviour of iron in the Bayer process has been investigated by neutron activation analysis and Ge(Li) spectrometry, using bauxite samples of various origin. The amount of iron impurities in alumina was found to be independent of the origin of the bauxites. Alumina is contaminated by iron in the process of decomposition of aluminate liquors; regardless whether iron is present in ‘dissolved’ form or as a floating impurity, it will pass into the alumina almost completely.     

Determination of gold in platinum by neutron activation analysis

The determination of gold in platinum by neutron activation analysis is described. The possibility of screening out the influence of the nuclear reactions on the final result of the determination was studied. In the case of microamounts of gold in platinum, gold was separated previously by extraction chromatography with dithizone as organic stationary phase. Gold fixed on the column was irradiated and determined gamma-spectrometrically.