Neutron activation analysis with PE moderated252Cf neutron source

The 1.369 MeV -rays emitted from²⁴Na²⁴Mg+^–+ after²³Na(n,)²⁴Na reaction were counted by high purity germanium (HPGe) detector and the half-life of²⁴Na was derived. This process was simulated by Monte Carlo Neutron and Photon Transport Code (MCNP-4A).²⁵²Cf neutron source was moderated by a polyethylene (PE) cylinder to increase the cross section of neutron absorption reaction and to decrease the biological hazard. NaCl powder of 20 cm³ and 40 cm³ volume in cylindrical polypropylene capsules were irradiated by the neutrons passed through the moderator. MCNP-4A was used to determine the optimum size of PE moderator, to assume the realistic geometry of the HPGe detector, and to assume the absolute efficiencies of the detector. The count rates for 1.369 MeV -rays in the HPGe detector were calculated by MCNP-4A for 20 cm³ and 40 cm³ NaCl. The accumulated counts calculated tumed out to be higher than those actually measured by 31% with a relative error of 3%. The half-life of²⁴Na measured within 4% and 1% for 20 cm³ and 40cm³ NaCl agrees with that of the reference. So, we can say that the result of MCNP-4A has about 30% of accuracy and 3% of precision in simulating the neutron activation analysis.     

In vivo analysis for nitrogen using a252Cf source

A set up forin vivo determination of nitrogen has been built. Phantoms containing different amounts of nitrogen have been measured as well as a volunteer in a pilot study. A total body protein content of 18.8 kg was calculated, to be compared with 17.0 kg estimated from potassium measurements.     

Neutron energy spectra of 252Cf, Am-Be source and of the D(d,n)3He reaction

The neutron energy spectrum of the following sources were measured using a fast neutron spectrometer with the NE-213 liquid scintillator: ²⁵²Cf, Am-Be and D(d,n)³He reaction from a 3 MeV Pelletron accelerator in Tokyo Institute of Technology. The measured proton recoil pulse height data of ²⁵²Cf, Am-Be and D(d,n)³He were unfolded using the mathematical program to obtain the neutron energy spectrum. The ²⁵²Cf and Am-Be neutron energy spectra were measured and the results obtained showed a good agreement with the spectra usually published in the literature. The neutron energy spectrum from D(d,n)³He was measured and the results obtained also showed a good agreement with the calculation by time of flight (TOF) methods.     

Mercury and cadmium determination in water by prompt (n, γ) method—252Cf as the neutron source

An evaluation of the sensitivity of mercury and cadmium determinations in large volumes of water is presented. A 10-μg²⁵²Cf source immersed in the water sample served as a neutron source. The (n, γ) reaction on hydrogen and the inelastic scattering from oxygen produced a background count rate that limited sensitivity. A lower limit of 20 ppm for both mercury and cadmium was found. The procedures described here can be applied to most of the other heavy metals. Research sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corporation.     

Instrumental neutron activation analysis of Al,V and Ti employing252Cf as a thermal neutron source

A rapid method for the determination of Al, V and Ti has been developed and is used for the analysis of these elements in different ores and alloys. An isotopic neutron source²⁵²Cf having a thermal neutron flux of the order of 8.5×10⁷ n·cm^–2 sec^–1 has been used for thermal neutron bombardment. Activity measurements were performed on a HPGe detector coupled to a PC based MCA unit. Depending on the half-life of the (n, ) product, different irradiation and cooling times were employed and thus the elements of interest were analyzed sequentially.     

A neutron induced prompt gamma-ray spectroscopy system using a 252Cf neutron source for quantitative analysis of aqueous samples

A neutron induced prompt γ -ray spectrometry (NIPS) facility has been developed at the Nuclear Chemistry Research Division, of the Korea Atomic Energy Research Institute (KAERI) with the aim of analyzing the major components of various elements in aqueous samples. The facility is equipped with a ²⁵²Cf neutron source and a γ-γ coincidence setup with two n-type coaxial HPGe detectors based on NIM spectrometric modules in association with data acquisition and spectral analysis systems. The development of the system, its set-up and the calibration of detection efficiency up to 8 MeV using a set of radionuclides and the (n,γ) reactions of chlorine are described in the paper. This revised version was published online in July 2006 with corrections to the Cover Date.     

Activation analysis of halogens in photographic emulsions using a252Cf neutron multiplier

A nondestructive neutron activation technique for the simultaneous direct determination of chlorine, bromine, and iodine in silver halide mixtures is described using a²⁵²Cf neutron multiplier (CFX). About 5–50 mg of sample are used. The analysis is semiroutine, without the need for a monitor included with each sample since the flux stability and reproducibility are within ±1%, decaying only with the 2.65 year half-life of²⁵²Cf. The precision and accuracy are counting-statistics controlled and are generally ±1% RSD or better. The method offers an attractive alternative to existing chemical and instrumental methods for these determinations in silver halide mixtures because it has the potential for providing reasonably rapid analyses with good precision and accuracy.     

Neutron spectrum and doses in a 18 MV LINAC

Bonner sphere spectrometer with TLDs pairs has been utilized to measure the neutron spectrum 100 cm from isocenter of a 18 MV LINAC, simultaneously the ambient dose equivalent due to neutrons and photons was measured in the control room area with neutron and gamma-ray area monitors. Measurements were carried out when the LINAC was delivering a dose of 600 MU at the isocentre that was located at 5 cm depth of a head phantom. Undesired neutron field in the treatment room produce activation reactions with nuclei in different materials of LINAC, couch, air, and phantom. To determine the dose due to decay of activation nuclei the ambient dose due to gamma-rays was measured inside the treatment room immediately after dose was delivered. Measured spectrum has two peaks, one between 0.1–1 MeV and other in the thermal region, the ambient dose equivalent in the control room are 3.1 and 0.93 μSv h⁻¹ for photons and neutrons, respectively. In the treatment room the ambient dose equivalent due to photons produced during decay of activation nuclei varies from 6 to 26.1 μSv h⁻¹.     

Additivity of inelastic gamma ray scattering in methanol—water and ethanol—water solutions

Compton profiles of water, methanol, ethanol and mixtures of methanol—water and ethanol—water have been measured using 60 keV gamma rays from a 5 Ci annular²⁴¹ Am source. The profile of each mixture has been compared with the profile of the sum of the components and at all concentrations a linear behaviour has been found.     

Comparison between the minimum detection limits of radioisotope X-ray fluorescence technique and activation analysiś with a low intensity252Cf neutron source

A comparative study of radioactive X-ray fluorescence and neutron activation analysis using a low-intensity²⁵²Cf source has been carried out. X-ray fluorescence proved to be superior to NAA if ion-exchange preconcentration preceds the instrumental method, while less difference in the minimum detectable limit was found in direct analysis of aqueous solutions.     

Determination of some macro and micro nutrients in soils of Maharashtra State by instrumental neutron activation analysis using 252Cf as a thermal neutron source

Some macro and micronutrients in soils from some districts of Maharashtra State have been determined by instrumental neutron activation analysis. Neutrons from ²⁵²Cf have been used for irradiation. The activity induced was measured by a HPGe detector coupled to a MCA unit. The statistical evaluation of the method has been explained. This revised version was published online in August 2006 with corrections to the Cover Date.     

Quantitative variability in the 252Cf plasma desorption mass spectra of triglycerides and waxes

A series of mixtures of solid triglycerides and waxes are examined using ²⁵²Cf plasma desorption mass spectrometry. The relative abundances of diagnostic ions are found to vary with sample preparation, handling, and composition. It is proposed that the less efficiently packing, shorter chain, compounds are forced to the analysis site, i.e. the surface. This takes place at varying rates that reflect the bulk properties of the mixture as revealed by its phase diagram and thermal history. Mixtures that remain liquids during analysis show ion abundances correctly reflecting their composition. Mixtures of isotopomeric glycerides also show normal ion abundances.     

Cumulative yields of127gSn and128Sn in the spontaneous fission of252Cf

The potteries found on the Tremiti Isles (Italy, Adriatic Sea) have been characterized through their trace elements content. The goal of the work was to find out the number of ore deposits that supplied the clay used to manufacture the pottery. Neutron activation analysis has been employed for trace elements content determinations; the results have been statistically evaluated, clusterized and discussed.     

Precise assay of weight per cent sodium in high-level processed nuclear tank waste using a <Superscript>252</Superscript>Cf neutron source

An infrared furnace (ULVAC RHL-410P) was newly applied to the extraction of tritium from concrete samples. After studying the tritium recovery yield regarding temperature and time, the best extraction conditions were set to 800 °C (setting temperature) for 30 minutes under Ar-gas flow of 200 ml/min. Tritium was collected in two cold traps and transferred to a vial for liquid scintillation counting. It took about one hour for the extraction of tritium. Reproducibility and recovery yield of tritium were about 100% compared to the values obtained by the ordinary heating method using an electric furnace. Gamma-ray emitters and tritium of concrete samples collected from several accelerator facilities have been determined. The specific activity of tritium strongly correlated with that of ¹⁵²Eu and ⁶⁰Co, so it was found that tritium was produced by thermal neutron reaction by the ⁶Li(n,)³H reaction. The results indicate that the tritium specific activity in concrete can be estimated from the ⁶⁰Co specific activity obtained easily by -ray measurement.On leave from IHEP, Beijing.This work was supported by Japan Society for the Promotion of Science. The authors also are grateful to Dr. S. Watanabe, Center for Nuclear Study, University of Tokyo, Dr. T. Ohtsuki, Laboratory of Nuclear Science, Tohoku University, and Dr. T. Saito, Research Center for Nuclear Physics, Osaka University, and their colleagues for concrete sampling.     

Determination of depth of a radionuclide source in a tissue equivalent phantom

Hydrophilic materials which refer to a group of cross-linked polymers originally developed in the 60s to produce soft contact lenses are characterised by an equilibrium water uptake in the range 15–95 % by wet weight when hydrated in water or normal saline solution at 25 °C. This ability to absorb controlled amounts of water makes them suitable human tissue substitutes. Four types of hydrophilic materials of different composition and thickness were placed between a ²²Na calibrated point source and a single LaBr₃: Ce (5 %) detector (Saint-Gobain) at a fixed distance between source and detector. The scatter-to-peak ratio was determined by selecting five scatter angle windows between 25 and 50^° (467–376 keV), at 5^° intervals, to study how the ratio varied with attenuating material, thickness and composition. From photon spectra recorded a ‘best’ estimate of the depth of the source in the hydrophilic material was obtained by finding the most sensitive scattering window. Theoretical and practical models of the source-to-detector geometries are included and discussed.     

Moisture profile measurements of concrete samples in vertical water flow by gamma ray transmission method

Samples of concrete for popular habitation (0.1×0.03×0.1 m) and cellular concrete (0.1×0.05×0.1 m) were submitted to water vertical ascending infiltration. The moisture content spatial and temporal evolution of each sample it was monitored in three halfway positions in a same horizontal line, applying the gamma rays transmission method. The data were taken with a 137Cs (3.7×1010 Bq, 0662 MeV) source, Nal (Tl) of 2×2″ detector coupled to gamma ray spectrometry standard electronic with multichannel analyzer and a micrometric table. For the popular habitation concrete, there was a clear correlation between wetting profiles and concrete strength. The cellular concrete showed a wetting profile compatible to its greater porosity.     

Neutron induced prompt gamma ray method in the quantitative elemental analysis of materials and compounds determination of antimony in Bi-Pb-Cu-Sr-Ca-Sb-O high temperature superconducting ceramics

The in-beam neutron induced prompt -ray method of quantitative elemental analysis of materials and compounds used in Neutron Research Department (NRD) of PNPI and experimental arrangement installed on the horizontal channel of WWR-M reactor are described. The results of measurements of antimony concentration in the antimony doped sample of HTSC ceramics after two stages of annealing are reported.     

Movement of tritium labelled water from a point source in soils

The migration of HTO from a point source was studied in the soil of the storage of radioactive waste at horizontal distances of 10 to 40 cm from the source between 2 and 4 m depths at 5 different rainfalls, up to 7641/m². The water movement changed from 0.17 cm/l (at 10 cm) to 0.28 cm/l (at 40 cm distance) when 186 1 was irrigated, while at 764 1 rainfall it was found to be 0.11 cm/l at every distance. The estimated parameters of a three-dimensional migration model constructed to characterize HTO movement revealed that the HTO distribution migrates downwards in a small, about 1 m thick layer with an initial rate of 0.17 cm/l to slow down to about 0.05 cm/l after 50 years. The distribution is spreading horizontally with a constant rate of about 0.08 cm/l.