The effect of atmospheric plasma treatments on plastic scintillator for beta-ray measurement

A plastic scintillator (PS) can be used for beta-ray measurements using a liquid scintillation counter (LSC) without the necessity for a liquid scintillator when liquid samples of beta-emitters are placed on the PS. However, the measurement efficiency with the PS in this study was not high, especially in the case of tritium. With a sample of tritiated water, a long measurement time was necessary with a conventional LSC. However, the measurement efficiency was improved drastically by modifying the PS surface with atmospheric-pressure glow-plasma processing (the plasma method). A 2 Bq, 20 μL sample of tritiated water placed between two PS sheets was successfully measured within 2 min by an LSC. The measurement efficiency was same as that of using liquid scintillator: 48 ± 2 % for tritiated water. The measurement efficiency was initially increasing over time, and after almost 6 h, it plateaued and remained at a constant value for several weeks. Additionally, the measurement efficiency of the plasma-modified PS was identical when it was used soon after the treatment and after being properly stored for 1 week The results show that plasma-modified PS can be used stably after storage in a freezer or a deep freezer. The plasma method is advantageous because it produces little radioactive waste fluid. This paper presents these results and the results of an investigation of the surface of the plasma-modified PS under observation with an atomic force microscope, and the mechanism behind the high measurement efficiency is discussed.     

Low-energy neutron flux measurement using a resonance absorption filter surrounding a lithium glass scintillator

The resonance absorption filter technique has been used to determine the thermal/epithermal neutron flux. The main idea in this technique is to use an element with a high and essentially singular resonance in the neutron absorption cross section as a filter surrounding a miniature-type lithium glass scintillator. The count with and without the filter surrounding the detector gives the number of resonance-energy neutrons. Some preliminary results and a comparison with the MCNP code are shown.     

Accurate fast neutron activation analysis for oxygen in geological materials

Sources of error in the fast neutron activation analysis determination of oxygen have been investigated and minimised. The oxygen contents of eighteen international rock standards and a sulphide ore standard have been determined, and compared with the values calculated by difference using the reported full analyses. Accuracies of 0.3% average deviation and reproducibilities of ±0.2% standard deviation have been obtained, where oxygen contents exceeded 1.0 g.     

Determination of cadmium in environmental materials by fast neutron activation analysis

Cadmium is determined by activation analysis with fast neutrons, obtained by irradiation of a thick beryllium target with 14.5-MeV deutrons. Cadmium-111m, formed via the ¹¹²Cd(n, 2n)^111mCd and ¹¹¹Cd(n, n′)^111mCd reactions, is separated by liquid—liquid extraction with zinc dithyldithiocarbamate in chloroform and measured with a Ge(Li) γ-spectrometer. For low concentrations, cadmium is precipitated as cadmium ammonium phosphate after the extraction. NBS and BCR reference materials were analyzed: for concentrations between 3 and 500 μg g^?1, the relative standard deviation ranges from 5 to 3% The results obtained for sewage sludge are compared with those obtained by reactor neutron activation analysis.     

Multiple fast neutron and gamma-ray beam systems for the detection of illicit materials

Neutron and photon sources have been combined in order to assess the performance of these combinations to discriminate between materials of similar composition. The evaluation has been carried out on the basis of the maximum and minimum ratio values of the relative transmissions of high-energy gamma- or X-ray and neutrons. The number of materials with similar ratio values was used as an indicator of the effectiveness of each source combination. The use of three sources, instead of two, significantly improves the capability of neutron/photon combination to separate similar in composition materials.     

The application of moisture measurement in materials used in ironmaking by neutron moderation techniques

Nucleonic moisture gauges, extensively used in the British Steel Corporation, i.e., insert probe and surface mounted types, as well as transmission gauging are discussed.     

The multielement potential of fast neutron cyclic activation analysis

Cyclic neutron activation analysis (CNAA), has, in recent years been developed as a useful analytical tool for the assay of short-lived isotopes in single element situations. The work described in this paper investigates the potential of the technique for composite samples having a wide range of elements that produce short-lived and long-lived isotopes on neutron irradiation. Accelerator-derived neutrons with average energies of 3 MeV, 6MeV and 14MeV were employed in what has been dubbed Fast Neutron Cyclic Neutron Activation Analysis (FNCAA). The approach to multi-element analysis entailed: (a) determination of cycle parameters in single element samples via the reactions²⁷Al(n, p)²⁷Mg (9.6 min,E =840keV), and¹³⁷Ba(n, n)^137mBa(2.3min,E =662keV), (b) a test of the method on a composite rock sample, (c) determination of analytical sensitivities using both powdered kale and rock standards and (d) a comparison of analytical results with other techniques. The results obtained in all these measurements are presented and discussed.     

Nickel determination in biological materials at ultratrace level by fast neutron radiochemical activation analysis

Using radiochemical separation of cobalt following the fast neutron reaction⁵⁸Ni(n, p.)⁵⁸Co and long high fluence irradiation, we attempted to improve the determination limit for Ni to the nanogram and sub-nanogram level. A Compton suppression spectrometer was shown to be the best choice compared to co-axial or well-type HPGe detectors. Results for low level biological reference materials such as serum and milk powder are discussed. Use of both dried and pre-ashed samples showed that losses of Ni and Co on ashing are non-significant. The influence of the silica ampoule blank was also investigated.     

The effect of hydrogen ion on the steady-state multiplicity of substrate-inhibited enzymatic reactions

In this paper we concentrate our attention on the stability and transient behavior of the isothermal system (CSTR) with a substrate-inhibited enzyme reaction producing hydrogen ions. Our investigation covers the region of multiple steady states uncovered previously (1) (ordinary hysteresis and isola). We investigate the local stability characteristics of the different steady states, the effect of the initial condition on the transient behavior and the response of the system to feed disturbances of various magnitudes and durations.     

An unusual effect of fast neutron irradiation of lanthanide /III/ chlorides

When anhydrous EuCl₃, GdCl₃, DyCl₃ or Eu₂O₃ are irradiated with fast neutrons and then dissolved in dilute hydrochloric acid, small amounts of reducing species, believed to be divalent lanthanide cations, are revealed. The amount produced increases with the thermodynamic stability of the Ln²⁺ species /Eu>Dy>Gd>/.     

The effect of hydrogen ions on the steady state multiplicity of substrate-inhibited enzymatic reactions

The present investigation concentrates on the study of the complex phenomenon of multiplicity in membranes carrying substrate-inhibited, hydrogen ion-sensitive enzyme. The investigation takes into consideration both symmetrical and asymmetrical steady states. The number of steady states (symmetrical and asymmetrical) found in this case is quite large, giving rise to multiple hysteresis loops and multiple “isolas.”     

The effect of hydrogen ion production on the steady-state multiplicity of substrate-inhibited enzymatic reactions

The phenomenon of multiplicity is investigated for an isothermal continu ous stirred tank reactor (CSTR) in which an enzyme reaction producing hydrogen ions is taking place. The activity of the enzyme considered is sensitive to the hydrogen ion concentration and is inhibited by excess substrate. The enzyme is bound and the washout phenomenon is negligible. The investigation has uncovered a new type of hysteresis, consisting of a closed curve on the multiplicity diagram, and is disconnected from the rest of the multiplicity curve. This phenomenon has also been observed and analyzed by Uppal et al. (1) in their investigation of the non-isothermal, non-adiabatic (CSTR), and they have termed those closed curves “Isolas.” In the present paper we have elucidated the physical reason for the occurrence of those “Isolas” for the enzymatic reaction under consideration. We have also investigated the effect of different parameters on the appearance, disappearance, and size of the “Isolas.”     

The determination of fluorine in bone by fast neutron activation analysis

A routine method is presented for the determination of fluorine in small bone samples by activation analysis with fast conversion neutrons. Both the purely instrumental determination and the analysis by chemical separation are discussed. The activations are performed with the AVF cyclotron of Philips-Duphar at Petten. Use was made of a rabbit system equipped with a Be-target, which can be inserted in the internally deflected beam of the cyclotron. The sensitivity of the instrumental method is ≈1 μg. Application of chemical isolation results in a sensitivity of ≈0.1 μg.     

The effect of pressure on neutron irradiated ammonium chromates

The effect of pressure on neutron irradiated ammonium chromate and ammonium dichromate has been studied. Compression was found to have no effect on the retention and on the M and DP yields in both salts. Pressure applied before heating was found to retard annealing in ammonium chromate, while it appeared to have no influence on the annealing of ammonium dichromate.     

The effect of neutron and mixed gamma and neutron irradiation on the solar properties of borosilicate glass

Neutron and mixed gamma and neutron irradiation, at different absorbed doses, of borosilicate glass with four different chemical compositions was conducted to investigate the effects on the solar properties of the glass. Irradiation was performed in the tangential beam tube and central thimble of a nuclear reactor. The effect of thermal and epithermal neutrons on such solar properties as secondary heat-transfer factor, solar factor (the total solar energy transmittance), and shading coefficient of the borosilicate glass were investigated to determine the effect on the solar properties of borosilicate glass, because of its neutron absorbance property.     

The effect of spin multiplicity on the photochemical reaction of a 2-vinylnaphthalene-dichloromaleic anhydride system

Research on Chemical Intermediates - The photochemical reaction of a 2-vinylnaphthalene — dichloromaleic anhydride system has been studied in order to elucidate the correlation between the...     

Elemental analysis of fertilizer by fast neutron activation

A simple and accurate technique has been developed to analyse the commercial fertilizers for phosphorous, potassium, chlorine, magnesium and silicon. The method is based on the fast neutron activation.     

The NIMROC samples as reference materials for neutron activation analysis

The NIMROC reference materials NIM-D, NIM-G, NIM-L, NIM-N, NIM-P, and NIM-S and the precious metal ore PTO-1 have been analysed using thermal and epithermal methods of instrumental neutron activation. The abundances of 40 major, minor and trace elements are reported. The usefulness of the NIMROC reference materials is assessed in terms of the requirements of neutron activation techniques. Of the seven reference materials, NIM-L is the most useful geochemical material for activation analysis. It contains suitably high concentrations of most elements that can be determined. Inhomogeneity problems encountered in PTO-1 for some elements give emphasis to the difficulty of selecting suitable geological material for ultra-trace elements where small quantities of sample are used.