Absolute intensity of the 140.5 keV gamma-ray of99Mo

The induced activity of the⁹⁹Mo isotope is mostly determined via the 140.5 keV γ-line, which is the strongest gamma-ray of its daughter,^99mTc. Some recent literature, however, indicates a direct feeding of this energy level from the mother isotope as well. Considering the importance of this line in practice as well as the large controversy and scattering in relevant nuclear data available at present, a combined effort was made to remeasure this questionable absolute intensity. A relative method of irradiating a Mo-target with reactor neutrons and repeatedly measuring its (n,γ) induced activity relative to the 181.1 keV and 739.5 keV gamma lines of⁹⁹Mo as internal references was used. The weighted average of different runs yielded γ(⁹⁹Mo, 140.5 keV)=(5.07±0.37)%. As a consequence, when the 140.5 keV gamma line is used, the contribution from the⁹⁹Mo mother isotope should always be taken into account, e.g. in neutron cross-section measurements and neutron activation analysis.     

Reinvestigation of the234Pa gamma-ray spectrum

The decay of²³⁴Pa(UZ) was reinvestigated using high-resolution coaxial and planar HPGe detectors. Accurate energy and intensity values of 327 photons are given, of which 144 previously unobserved.     

Estimation of <Superscript>235</Superscript>U concentration in some depleted uranium samples by high resolution gamma-ray spectrometry using 185 keV and 1001 keV gamma-energies of <Superscript>235</Superscript>U and <Superscript>234m</Superscript>Pa

The migration of ²³⁷Np in an undisturbed Chinese loess column was investigated by direct γ-ray method. The column was taken from a field test site and installed in a laboratory simulation hall. Radionuclide ²³⁷Np in the form of neptunium nitrate, mixed with quartz, was introduced into the column and covered with loess. Artificial rainfall was applied to the column for about 3 years and, the counting rates of ²³⁷Np in the column from 56 to 616 days at different vertical positions were detected with a γ-ray detection system. Based on the counting rates of ²³⁷Np in the simulation column at different vertical positions and the distance from the source layer, the relationship of the mass center of ²³⁷Np in the column at different experimental periods to the experimental time was established, C _m = 0.36 log(t)-2.75. Here C _m is the mass center of ²³⁷Np in the column, cm, and t is the experimental time in days. Based on this relationship, the mass center of ²³⁷Np for the 1,073-day experiment was predicted and compared to that obtained with the final destructive method. The good agreement between the prediction and the experimental values indicates that the direct γ-ray method could be used to predict the migration of strongly adsorbed radionuclides such as ²³⁷Np in environmental media with the help of laboratory simulation columns.     

Prompt gamma-ray neutron activation analysis by the absolute method

In this study an investigation into the applicability of the absolute method in Prompt Gamma-ray Neutron Activation Analysis (PGNAA) was undertaken. Although the system parameters are adequately characterized, the scatter in nuclear data for a number of elements is significant. For our particular experimental set up the K-factors were calculated for a number of elements using both Au and Fe as monostandards. A comparison was made between the calculated and experimentally determined K-factors and from this comparison the feasibility of the absolute method in neutron prompt gamma-rays can be realized for a number of elements.     

Measurement of the absolute infrared intensity of the fundamental vibration of HCl in low temperature matrices

Using the concentration of HCl in the argon mixture in the gas phase (1:2000), the pathlength of a film (estimated by monitoring interference fringes) and the measured integrated absorbance of the HCl band, we have obtained the absolute intensity, A, for monomeric HCl isolated in the argon matrix. The average value is A = 40±5 km mole^?1, comparing very closely with the intensity of A=39km mole^?1 of HCl in the gas phase. These results are compared with the studies of the intensity of HCl in other environments and correlated with the proton affinities of the matrix molecules or atoms.     

Measurement of mass attenuation coefficients for four mixtures using X-rays from 13 keV up to 40 keV

The total absorption coefficients for some selected organic compounds relevant to health physics, Triaflol BN (C₃H₄O₂)_n, Triaflol TN (C₁₂H₁₈O₇)_n, Kapton (C₄₄H₂₀O₁₀)_n, and Melinex (C₁₀H₈N₄O₄)_n were measured in the X-ray energy range from 13 keV up to about 40 keV using a collimator, high purity germanium detector with thin Be window and variable energy X-ray source. The measured values are compared with the theoretical ones obtained using the XCOM code. The agreement is generally good within a few percent.     

The absolute intensity of depolarised light scattering from liquid argon

The depolarised light scattering intensity from liquid argon has been measured relative to the 991 cm^?1 Raman line of benzene, whose absolute intensity is known. The mean-square induced polarisability anisotropy is (10.6±1.0) × 10^?51 cm⁶, approximately five times larger than previously reported, but in agreement with simulations based on the dipole-induced-dipole model and with another recent measurement.     

Measurement of attenuation coefficients of some dilute solutions at 662 keV

Linear attenuation coefficients of solutions of some compounds in aqueous medium have been measured at 662 keV. From the precisely measured densities of these solutions, mass attenuation coefficients were then obtained. The composition dependence of these mass attenuation coefficients has been successfully used to determine mass attenuation coefficients of the respective solutes which agree very well with the values obtained through XCOM calculations.     

Measurement of radioactive samples in Marinelli beakers by gamma-ray spectrometry

Radioactivity measurement of environmental samples is frequently assayed by gamma-ray spectrometry using Marinelli beakers. In this work, self-absorption and coincidence summing effects arising in activity measurements for Marinelli beaker geometry have been studied with a Ge detector. Three types of Marinelli beakers which have capacities of 450 mL, 1 L, and 2 L were developed. Self-attenuation effects for density variation of radioactive samples in each type of the Marinelli beakers were measured as a function of gamma-ray energy, and also the results were compared with calculated values by mathematical model. Meanwhile, the coincidence summing effects of¹²⁵Sb and¹⁵⁴Eu nuclides were obtained from the determination of the full-energy peak and total efficiencies for a Ge detector.     

Measurement of the ash content of iron-rich coals by gamma-ray irradiation

Ash contents of some coal samples from Enugu mines in Nigeria were measured using gamma-ray irradiation technique. The method employed gamma-ray energies of 0.060, 0.662 and 1.33 MeV of²⁴¹Am,¹³⁷Cs and⁶⁰Co, respectively, and a counting system with a scintillation detector, to obtain empirical relationships between the conventionally determined ash content and the measured gamma-attenuation coefficient in the sample. The sensitivity of the method was observed to decrease drastically with increase in ash content above 35% ash, and with increase in energy of the gamma-ray. Further analyses showed that the error in the ash content determination was due to iron content which was not constant, but increased with ash content, with vidth variation above a mean value of ±0.64% Fe₂O₃.     

Measurement of total and photoelectric cross sections of rare earth elements present in compounds for 123.6 keV and 145.4 keV photons

A new, simple and direct method proposed earlier by us has been employed here to measure the total photoelectric cross section of rare earth elements in the range 58 Z 66 present in compounds at 123.6 keV and 145.4 keV photon energies. The K X-ray fluorescence intensities emitted by these elements, from irradiating their compounds by the photons of above energies, are measured using a NaI (Tl) spectrometer system in a 2π geometrical configuration. The K X-ray fluorescence cross sections of the rare earth elements are determined, from which the total photoelectric cross sections are evaluated. Total mass attenuation coefficients of compounds for the K X-ray and the incident radiations respectively have been measured and these values were compared with the corresponding theoretical values and a good agreement between them is obtained.     

Computer-aided data reduction of absolute infrared intensity measurements by transmission and reflection

The profiles and intensities of infrared absorption bands of liquids provide information about the dynamic structure of materials in the liquid state. Such data can also provide secondary reference standards for checking intensity measurements made on both dispersive and Fourier transform infrared spectrophotometers. A method for evaluating the absorption intensities of thin films of liquids is described. The results are expressed in terms of the optical constants (n, k). The method is based on measurement of the film transmission over the full wavenumber range of the measurement combined with an additional measurement of the attenuated total reflection spectrum over a short range in a region of low absorption. Recent measurements on a series of thirteen common organic liquids are cited as are measurements on free standing polymer films.     

Method of absolute estimation of the quality of a software for doublet deconvolution in semiconductor gamma-ray spectrometry

The method for absolute estimation of software quality for doublet deconvolution based on a system of penalty points is presented. The method developed is an effective means as for independable and correspondence competition of programs for doublet processing and for fine tuning of these programs. The application of the suggested method is demonstrated and discussed on the example of test spectrum No. 400 by IAEA.     

Determining 234Th and 238U in rocks, soils, and sediments via the doublet gamma at 92.5 keV

Efficient and accurate measurements of uranium (U) and U-series radionuclides in earth's materials are needed to assess its environmental impact, reconstruct geochemical histories, and quantify heat production in the crust. To date, measurements of 234Th and 238U by gamma spectrometry have relied on the quantification of 234Th gamma emissions at approximately 63 keV (absolute intensity = 3.7%) and the (234m)Pa gamma at 1001 keV (absolute intensity = 0.84%). However, use of the 63 keV emissions can be hampered by 232Th interferences and self absorption, and the 1001 keV photon has a very low yield. Here we describe the effective use of the 234Th doublet gamma emission at approximately 92.5 keV (total absolute intensity = 4.8%) for 234Th and 238U measurements. This doublet has been largely ignored because of its proximity to the Th K(alpha1) (93.3 keV) and thus its vulnerability to a Th self-fluorescence interference. We demonstrate that additions of U and 40K to a Th ore sample do not increase the count rate at 92-93 keV above that which would be expected from the associated additions of U and 234Th. We also show that the Th self-fluorescence interference appears to be an anomaly associated only with the analysis of relatively thick (>1 mm) Th minerals, and suggest that fluorescence will not complicate the 92-93 keV region in most environmental samples. A review of decay data reveals that Th K(alpha1) X-rays associated with the decay of 235U and 228Ac can significantly interfere with quantification of the 92.5 keV 234Th doublet. We show that simple experimentally-derived correction factors for these X-rays can be used to accurately determine 234Th using its strongest gammas, resulting in higher count rates and smaller self-absorption corrections relative to the traditional analytical lines. Total 1 sigma analytical error associated with U measurements at 92.5 keV ranged from 1 to 9% and is dominated by the relative size of the 228Ac interference. Detection limits for U in environmental samples using this technique are on the order of 50 ppb.     

Precise determination of the intensity of 226Ra alpha decay to the 186 keV excited state

There is a significant discrepancy in the reported values for the emission probability of the 186 keV gamma-ray resulting from the alpha decay of ²²⁶ Ra to 186 keV excited state of ²²² Rn. Published values fall in the range of 3.28 to 3.59 gamma-rays per 100 alpha-decays. An interesting observation is that the lower value, 3.28, is based on measuring the 186 keV gamma-ray intensity relative to the ²²⁶ Ra alpha-branch to the 186 keV level. The higher values, which are close to 3.59, are based on measuring the gamma-ray intensity from mass standards of ²²⁶ Ra that are traceable to the mass standards prepared by HÓNIGSCHMID in the early 1930's. This discrepancy was resolved in this work by carefully measuring the ²²⁶ Ra alpha-branch intensities, then applying the theoretical E2 multipolarity internal conversion coefficient of 0.692±0.007 to calculate the 186 keV gamma-ray emission probability. The measured value for the alpha branch to the 186 keV excited state was (6.16±0.03)%, which gives a 186 keV gamma-ray emission probability of (3.64±0.04)%. This value is in excellent agreement with the most recently reported 186 keV gamma-ray emission probabilities determined using ²²⁶ Ra mass standards.     

Measurement of30Si as a tracer by neutron-induced prompt gamma-ray analysis

The application of stable isotope analysis using neutron-induced prompt -ray analysis (PGA) with cold/thermal neutron beams for the tracer study of geological materials are discussed. Silicon has three natural isotopes differing in abundance:²⁸Si (92.23%),²⁹Si (4.67%) and³⁰Si (3.10%). For the purpose of the assessment of Si migration in engineered barrier material, enriched³⁰Si can be used as a tracer due to its nuclear and chemical properties. Isotope analysis of³⁰Si was performed by PGA during the tracer study. Neutron intensity at the sample position was 1.4·10⁸ n¢cm^–2·s^–1, 2.4·10⁷ n·cm^–2·s^–1 for cold and themal neutron guided beams of JRR-3M, respectively. Calibration curves and analytical sensitivity of³⁰Si were determined based on measurement of standard samples. BG and detection limits for³⁰Si analysis were also measured in Japanese bentonite (Kunigel V1 and Kunipia F) and their pore water. Fiffteen elements were determined simultaneously using PGA.