K. Kostadinov

Epithermal neutron activation analysis of uranium by neptunium-239 using high resolution gamma-spectrometry

The possibility to use the most intensive gamma-peak of239Np for INAA of uranium with epithermal neutrons and high resolution Ge(Li)-spectrometry is evaluated. A way for calculation of the peak area of overlapping peaks of153Sm and239Np is proposed. This can be used in other similar cases in the practice of NAA. On this basis a scheme for NAA of uranium in geological objects is proposed. Lower detection limit is 8·10−8 g U the precision 5–10% (relative standard deviation). The accuracy is demonstrated by the analysis of some geological standard reference materials.

Trace element analysis of biological materials by thermal and epithermal neutron activation analysis

A scheme for instrumental neutron activation analysis of biological materials is proposed. The scheme is based on a combination of thermal and epithermal activation. The accuracy is evaluated by analyzing 4 standard reference materials. Results from the analysis of human blood serum and plasma are given.

Epithermal neutron activation determination of uranium in environmental waters by neptunium-239 after preconcentration on activated carbon

A method for the analysis of uranium in natural waters based on preconcentration of uranium on activated carbon, irradiation with epithermal neutrons, and a high resolution gamma-spectrometry of239Np was developed. The chemical yield of uranium preconcentration is determined by treating a parallel sample to which a known uranium quantity is added. The lower limit of determination amounts to 1.4·10−8 g uranium per liter. The possible interfering in gamma-spectrometry of neptunium-239 was discussed too. The applicability of the proposed method is shown by the analysis of uranium in sea-, river-, geothermal-, drinking- and rain-water samples.

A method for preconcentration and measurement of cosmogenic beryllium-7 in natural waters

The measurement of beryllium-7 in natural waters usually requires a radiochemical procedure of preconcentration. A radiochemical method is proposed of fast separation and preconcentration of7Be from natural waters by adsorption of its complex with Eriochromcyanine-R on activated charcoal. The method permits to measure as littile as 0.1–0.05 Bq/l with an overall error less than 10%.

Uranium content variations in thermal waters from the West Rhodope cristalline massif during earthquakes in the Chepino Valley (South Bulgaria)

The uranium content of the thermal waters in the Chepino valley was determined in a period of increased seismic activity. Significant changes in the uranium concentration, much above the normal background values were established. In one group of water sources a well-expressed synchrony in the uranium content variations is observed and the maximum is reached about 1.5–2 months after the initial strong seismic shock.

14C measurements in Bulgarian and Hungarian wines from 1986

The measurements of14C in ethanol samples extracted from wines of different wine districts in Bulgaria and Hungary in 1986 showed that the atmospheric reservoir remained practically undisturbed by the emission due to Chernobyl accident.

Instrumental neutron activation analysis of trace elements in quartz

A scheme for INAA of 32 elements (As, Au, Ba, Br, Ca, Cd, Ce, Co, Cr, Cs, Eu, Fe, Hf, Hg, Ir, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, W. Yb, Zn) in quartz glass is proposed. The accuracy of the procedure is evaluated by the analysis of two NBS standard reference materials (SRM-1571 and SRM-1632-a). The method is convenient for routine work. The method was used for the determination of impurities in laboratory quartz glass.

Radioanalytical methods in the hot atom chemistry of sulfur in inorganic systems

The paper presents a comprehensive review of radioanalytical methods for chemical identification of radioactive sulfur atoms recoiling in neutron irradiated (or implanted) inorganic systems.

Radioanalytical method for determination of the chemical forms of35S hot atoms in reactor-irradiated AlCl3−FeCl3

A radioanalytical procedure for the determination of the chemical forms of35S in reactor irradiated crystals AlCl3, FeCl3 and AlCl3−FeCl3 is described. The method includes:35S extraction with trichloroethylene, precipitation of35S2− as iron sulfide and of (35SO42−+35SO32−) as Ba-salts. All fractions are converted to, and measured as, BaSO4.

Optimization of calculations for the preparation of standard solutions

Abstract The calculations necessary in the preparation of a large number of solutions used as standards, are time-consuming and tedious. The scheme proposed significantly shortens the time and makes the work more routine. The equations used are derived from wellknown stoichiometric expressions and mathematical representations of some necessary restrictions. The scheme has advantages when many solutions must be prepared for any analytical method.