A dipping method for radioactivity measurement in water using plastic scintillator

Journal of Radioanalytical and Nuclear Chemistry - A new dipping method was studied for the measurement of radioactive solution using plastic scintillator sheets and pellets (PSs) and a liquid...     

The effect of scintillator materials on the fast neutron multiplicity measurement

Journal of Radioanalytical and Nuclear Chemistry - To analyze the effect of scintillator detectors on the fast neutron multiplicity, this paper uses Geant4 and Matlab to simulate and study three...     

The use of energy information in plastic scintillator material

Plastic scintillator material is often used for gamma-ray detection in many applications due to its relatively good sensitivity and cost-effectiveness compared to other detection materials. However, due to the dominant Compton scattering interaction mechanism, full energy peaks are not observed in plastic scintillator spectra and isotopic identification is impossible. Typically plastic scintillator detectors are solely gross count detectors. In some safeguards and security applications, such as radiation portal monitors for vehicle screening, naturally-occurring radioactive material (NORM) often triggers radiation alarms and results in innocent or nuisance alarms. The limited energy information from plastic scintillator material can be used to discriminate the NORM from targeted materials and reduce the nuisance alarm rate. An overview of the utilization of the energy information from plastic scintillator material will be presented, with emphasis on the detection capabilities and potential limitations for safeguards and security applications.     

Development of continuous inflow tritium measurement in water technology using electrolysis and a plastic scintillator

Our goal was to develop a mobile tritium monitor for continuous inflow system for water sample. The system is based on electrolysis and a plastic scintillator detection system. The minimum detectable activity (MDA) of the prototype system is 431 kBq L^?1, while the MDA of a commercially available product is 740 kBq L^?1. We expected to achieve a 5.73-times lower MDA by optimizing detection geometry using a multi-hydrogen-gas-channel. The system can be applied either as a mobile leakage surveying method or as a fixed-type monitor for detecting tritium in drinking water by adapting conventional background reduction technologies.     

Studies on atmospheric plasma abatement of PFCs

Microwave plasma at 2.45 GHz frequency operating at atmospheric pressure in synthetic gas mixtures containing N₂, CF₄, C₂F₆, CHF₃, and SF₆ were investigated experimentally for various gas mixture constituents and operating conditions, with respect to their ability to destroy perfluorocompounds. It was found that the destruction and removal efficiency (DRE) of the process is highly dependent on the total gas flow. DREs of up to 99.9% have been achieved using 1.8 kW of microwave power at 20 l/min total flow rate.     

Experimental study of a large plastic scintillator response with different reflective coverings based on digital pulse processing method

Journal of Radioanalytical and Nuclear Chemistry - Digital pulse processing methods have various applications in radiation spectroscopy due to their unique properties. Here, the effect of light...     

The effect of surface treatments of glass capillaries on column performance

Summary The effects of etching and/or silylation of glass capillaries on column efficiency were studied. Coated with apolar OV-101, only columns subjected to the combined treatment showed an increase of about 50% in the number of effective plates. Surface hydroxylation, prior to silylation, gave a small additional improvement for this stationary phase.     

A radioxenon detection system using CdZnTe,an array of SiPMs,and a plastic scintillator

This paper presents the design and characterization of a prototype compact beta–gamma radioxenon detection system that utilizes a coplanar CdZnTe crystal, an array of SiPMs, and a plastic scintillator. The detector is directly mounted on a custom PCB. The system provides the advantage of room-temperature operation, while being compact, low noise, and with simple readout electronics. Preliminary measurements using ¹³⁷Cs, ¹³⁵Xe, and ^133/133mXe were conducted to optimize various system parameters to achieve optimal resolution of key photopeaks. The purpose of this research was to explore the potential of these radiation detection elements for use in beta–gamma coincidence applications.     

Accurate measurement of atmospheric helium isotopes.

We have developed an analytical system to measure atmospheric 3He/4He ratios precisely by using a static vacuum operation mass spectrometer and an ultrahigh-vacuum purification line. After purification of the sample, helium was introduced into the mass spectrometer. Ion beams of 3He and 4He were measured at the same time by a double collector system. A resolving power of about 700 at the 5% level of the peak height was attained for the complete separation of 3He ions from those of HD and H3. Repeated analysis of a sample calibrated against a standard showed a precision of about 0.2% error margin (2sigma). This system has been applied to evaluating the 3He/4He ratio of He Standard of Japan (HESJ), and for the assessment of the atmospheric variation of latitude. The observed 3He/4He ratio of HESJ, 20.405+/-0.040Rair (2sigma) agrees well with the value of 20.408+/-0.044Rair by Lupton and Evans, but is smaller than the recommended value of 20.63+/-0.10Rair in a literature. Air samples collected from 45 to 20 degrees N in the Far East showed a slight decrease of the 3He/4He ratio with latitude. Even though the variation is attributable to an experimental artifact, it may not preclude the possibility that the anthropogenic release of crustal 4He is significant in the high-latitude region of the northern hemisphere.     

Surface modifications of PET in argon atmospheric pressure plasma: Gas flow rate effect

The correlation between plasma optical properties and the treated polyethylene terephthalate (PET) surface characteristics have been studied at various Ar flow rate. The rotational T_rot and vibrational T_vib temperatures of APPJ were determined from SPS emission band. The pristine and plasma-treated PET surfaces were characterized by several techniques including X-ray photoelectrons spectroscopy (XPS), Raman spectroscopy, contact angle (CA), and atomic force microscope (AFM). The CA decreased rapidly in the flow rate range 1–3 L/min and weakly dependent as flow rate > 3 L/min. XPS results showed that C 1s % of plasma-treated PET surfaces decreases and has a minimum for samples treated at 3–4 L/min, while O 1s has a maximum at the same flow rate range. The carbon C 1s peak of pristine and plasma treated PET samples resolved into five subcomponents: C–C, C–O, C=O, O–C=O, and π–π bonds with variable percentage ratio accordance to the plasma gas flow rate. Raman data revealed a partial loss in the crystallinity of the treated PET samples and also confirm the incremental of C–O band at Ar flow rate of 3 L/min. AFM images showed that the surface roughness of treated PET films increases as Ar flow rate increases.     

Effects of electrochemical and plasma treatments on carbon fibre surfaces

This paper summarizes the chemical changes induced on carbon fibre surfaces (examined by X-ray photoelectron spectroscopy, XPS) by a variety of electrochemical treatment in aqueous electrolytes together with the improvements in fibre/resin bonding in the corresponding composite materials. It was found that there was no correlation between the amount of chemical functionality introduced onto the fibre surface and the fibre/resin bond strength, i.e. chemical bonding does not play a major role in fibre resin adhesion. This does not rule out the possibility of chemical bonding between the fibre and resin—it simply implies that it is not the governing factor. It is suggested that the immediate surface concentration of chemical groups is too low to make a significant contribution. To tailor interfacial properties it would be desirable to promote chemical bonding between fibre and matrix. The use of a specially designed plasma treatment cell has led to an increase in the surface concentration of chemical groups ( C OH, hydroxyl) that have the potential to react chemically with the resin. By exploiting grazing angle data taken from XPS analysis, it is shown that changes in the chemical nature of the fibres only occurs in the outermost layers, whereas the electrochemical reaction proceeds well into the fibre sublayers. Selective introduction of nitrogen-containing functionality (such as amines,  NH₂) has been achieved. The reactivity towards a particular plasma is shown to be largely dependent on the structure of the fibre surface. The number of C/N groups produced on higher modulus fibres was undesirably low. Their concentration was increased by biasing the fibres to a negative potential (10–30 V) during plasma exposure.     

Solid scintillator "Ready Cap" for measurement with a liquid scintillation counter--spectra and counting efficiencies for 15 different radionuclides

"Ready Cap", a small plastic container coated with solid scintillator has recently been introduced (Beckman Instruments, Inc.). Pulse height spectra and counting efficiencies obtained with a liquid scintillator and Ready Cap using a liquid scintillator counter were compared for 15 different radionuclides. For radionuclides emitting low-energy beta-rays or characteristic X-rays, the spectra for Ready Cap shifted toward the higher energy side compared with the spectra for the liquid scintillator. This tendency was reversed for the nuclides emitting higher-energy beta-radiations (36Cl and 32P). Generally, counting efficiencies both in Ready Cap and in liquid scintillator increased with increase in the energy of beta- or X-rays. For some nuclides, Ready Cap gave higher counting efficiencies and for others it gave lower values than in the liquid scintillator. However, the differences were not large within each nuclide. The use of Ready Cap is recommended for measurements of radionuclides when liquid scintillation cocktails have no means of waste disposal under the present Japanese radioisotope regulation.     

The effect of mechanochemical treatments of sepiolite with CsCl on the calcination products

Calcination of sepiolite and of two sepiolite/CsCl mixtures, unground and air-ground was investigated by thermo-XRD-analysis. At 200 °C sepiolite, neat, mixed or air-ground with CsCl lost interparticle and zeolitic water. The framework of sepiolite persisted during the dehydration but became defected, mainly in the air-ground mixture, less in the unground mixture and little in the neat clay. At 500 °C, with the loss of bound water, the neat clay was folded and transformed into sepiolite anhydride. In sepiolite/CsCl mixtures the dehydrated variety persisted but the degree of crystal-imperfection increased in the air-ground mixture more than in the unground mixture. At 700 °C the neat clay remained crystallized, but the CsCl mixtures became amorphous. Some crystalline dehydrated sepiolite or sepiolite anhydride persisted in the unground and air-ground CsCl mixtures, respectively. At 850 °C, the neat clay crystallized into protoenstatite with some enstatite and clinoenstatite. The amorphous fraction of sepiolite in the unground sepiolite/CsCl mixtures crystallized into pollucite and forsterite and the crystalline fraction was transformed into enstatite, protoenstatite, and clinoenstatite. In the air-ground mixture, the amorphous phase was transformed into pollucite with some forsterite and the crystalline fraction into enstatite.     

A radiometrie fourier transform spectrometer for the measurement of downwelling atmospheric emission

Radiometrically accurate downwelling emission from the atmosphere has been measured using a ground-based ambient temperature Michelson interferometer with a liquid-helium-cooled SiAs detector. Measurements were made under a wide range of atmospheric conditions covering very-cold, very-dry, very-clear sky conditions to heavy overcast with traces of sleet. Spectral resolutions of 0.5 and 0,1 cm^–1 were obtained with a radiometric accuracy of less than 0.5 K and a noise level on the order of 0.25 K rms.Overflights were made with the NASA ER2 high altitude research aircraft carrying a similar instrument [1, 2]. Aircraft and ground based LIDAR, radiosonde and other cloud physics experiments were also made at the same time to provide a data set complete enough to enable a much better understanding of the role of thin high clouds in the Earth's radiation balance.Measurements were made over the period from 10/24/86 to 11/21/86 in support of the NOAA/NASA/NSF project FIRE (First ISCCP Regional Experiment).     

Determination of oil reservoir radiotracer (SCN) in a single step using a plastic scintillator extractive resin

The analysis of radiotracers is important in the study of oil reservoir dynamics. One of the most widely used radiotracer is S¹⁴CN⁻. Prior to activity measurements by Liquid Scintillation (LS), routine determinations require the pretreatment steps of purification and concentration of the samples using anion exchange columns. The final elution media produces samples with high salt concentration that may lead to problems with phase separation during the LS measurement. Plastic Scintillation (PS) is an alternative technique that provides a solid surface that can be used as a platform for the immobilisation of selective extractants to obtain a PS resin. The proposed procedure unifies chemical separation and sample measurement preparation in a single step, serving to reduce the number of reagents needed and manpower required for the analysis while also avoiding mixed waste production by LS.     

Influence of atmospheric plasma on physicochemical properties of vapor-grown graphite nanofibers

Vapor-grown graphite nanofibers (GNFs) were modified by plasma treatments using low-pressure plasmas with different gases (Ar gas only and/or Ar/O2 gases), flow rates, pressures, and powers. Surface characterizations and morphologies of the GNFs after plasma treatment were investigated by X-ray photoelectron spectroscopy (XPS), contact angle, titration, and transmission electron microscopy (TEM) measurements. Also, the investigation of thermomechanical behavior and impact strengths of the GNFs/epoxy composites was performed by dynamic-mechanical thermal analysis (DMTA) and Izod impact testing, respectively. The plasma treatment of the fibers changed the surface morphologies by forming a layer with a thickness on the order of 1 nm, mainly consisting of oxygen functional groups such as hydroxyl, carbonyl, and carboxyl groups. After functionalization of the complete surfaces, further plasma treatment did not enhance the superficial oxygen content but slightly changed the portions of the functional groups. Also, the composites with plasma-treated GNFs showed an increase in T(g) and impact strength compared to the composites containing the same amount of plasma-untreated GNFs.     

Effects of plasma treatments for improving extreme wettability behavior of cotton fabrics

A simple, environmentally benign and energy efficient process for fabricating single faced superhydrophilic/hydrophobic cotton fabrics by controlling surface texture and chemistry at the nano/microscale is reported here. Stable ultra-hydrophobic surfaces with advancing and receding water droplet contact angles in excess of 146° as well as extreme superhydrophilic surfaces are obtained. Hydrophobic water-repellent cotton fabrics were obtained following plasma treatment through diamond-like carbon (DLC) coating by plasma enhanced chemical vapour deposition. The influence of changing different precursor’s plasma pre-treatments such as H₂, Ar or O₂ on the properties of DLC coatings is also evaluated using atomic force microscopy, X-ray photoelectron spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, and analysed in terms of contact angle measurements. Because of the DLC coating, the coated fabric showed to endure its superhydrophobic character even after 12 months.     

Influence of air plasma treatment at atmospheric pressure on wood extractives

The influence of an atmospheric pressure plasma treatment on wood extractives has been investigated by means of surface energy determination and XPS. Polar and disperse component of the surface energy show only marginal influence of plasma treatment, whereas XPS indicates plasma induced oxidation and degradation of the extractives.