Beta Scintillation Research Articles

Radiocolloids in leachate from the NRC field lysimeter investigations

An investigation of colloidal particles has been completed on leachate samples collected from sand and soil-filled lysimeters (of the Field Lysimeter Investigation: Low-Level Waste Data Base Development Program) in which low-level radioactive waste forms were buried. An array of analytical techniques including: gamma spectroscopy, liquid scintillation spectrometry, gross alpha and beta particle proportional counting, energy dispersive X-ray analysis (EDX), neutron activation analysis (NAA), X-ray fluorescence analysis (XRF), proton induced X-ray emission analysis (PIXE), gravimetric analysis, and scanning electron microscopy (SEM), were performed on samples thought to contain colloidal particles to determine particle composition and the nature of their association with radioactive material. Several different types of particles ranging in size from 0.02 to 20 μm were identified within the leachate including crystalline calcium hydroxide particles, rounded siliceous grains, angular weathered soil, and spherical particles apparently composed of an organic polymer. The primary radioactive material associated with these particles was Sr-90. About 2% of the total Sr-90 activity in the leachate is associated with colloidal particles. This information indicates that colloidal particles play a role in radioactive material transport through lysimeter soils.

In SituMicroassay of Ornithine Decarboxylase

Ornithine decarboxylase catalyses the principal step in the biosynthesis of polyamines (1, 2) and is reported to be a proto-oncogen implicated in the control of both FIG. 1. Modified rubber stopper. cell growth and transformation (3). Its activity is induced by a number of agents such as amino acids, pharmaceuticals, hormones, and growth stimuli (4). The cient to completely cover the plated cells so that very non-in situ assay methods of ornithine decarboxylase little radioactive substrate was needed. The screw-cap mentioned in the literature have several disadvanof each flask was removed and immediately replaced by tages: they require large numbers of cells, and the enzya modified rubber stopper. Figure 1 shows a perforated matic activity measured in cell-free extracts does not rubber stopper that contains an Eppendorf tube pushed necessarily reflect its true activity because the enzyme tightly into the hole to give a force-fit; the tube is 5.0 is unstable. The ornithine decarboxylase has a PEST mm diameter and 45 mm long, and its volume is 500 region (5) and is rapidly degraded. ml. The bottom of the tube was cut off with a razor Recently, a microassay of decarboxylation reactions blade 5 mm from the end. A hyamine-moistened paper in cultured cells was described by Bartos et al. (6). This strip (30 1 2 mm) was previously introduced into the method uses standard petri dishes with a modified tube to trap the CO2. At the desired incubation time, cover to permit the collection of CO2 evolved in the the reaction was stopped by injecting 0.5 ml of 50% decarboxylase reactions. We propose an alternative HClO4 with a hypodermic syringe through the rubber and simple method for the in situ determination of ornistopper. After 30 min the paper strip moistened with thine decarboxylase activity in cells cultured in ordihyamine from the Eppendorf tube was introduced into nary T-flasks. The only manipulation required for the the liquid scintillation counter vials and the CO2 proassay is replacing the screw-caps with modified rubber duced by the ornithine decarboxylase reaction was stoppers. counted by a Rack Beta (LKB, Sweden) scintillation We tested the method by using a new cell line (named CT-2) cloned in our laboratory from cells derived from a human colorectal carcinoma. The cells were cultured at 377C under 5% CO2 in DMEM–Ham’s F-12 culture medium that was supplemented with 10% FCS and antibiotics. The karyotypes of this newly established cell line determined after more than 50 metaphase analyses were 30% diploid and 55% hypodiploid (43– 44 chromosomes), and the remaining 15% were hyperdiploid, either triploid or tetraploid. Many micronuclei were observed. We also cultured the HT-29 human colon cell line from the ATCC to compare the results. The cells were seeded in ordinary cell-culture T-flasks, cell density was 5 1 10 cells/25 cm. To begin the test, the growth medium was discarded and replaced by 1.5 ml of PSS (1.2 mM KH2PO4, 16 mM NaH2PO4, 120 mM NaCl, 0.6 mM MgSO4, 3 mM KCl, 1.4 mM CaCl2, pH 7.4) containing 11 mM glucose, 1.0 mM L-ornithine and 5 mM [1-C]ornithine (0.4 mCi). This volume was suffi-

Radionuclide detection by ion-chromatography and on-line ICP/MS and beta detection: Fission product rare earth element measurements

Separation and analysis of235U fission produced rare earth elements (REE) is described. Rare earth elements were separated using a high presure ion chromatographic separation where by each rare earth is isolated and individually detected. Detection is performed by inductively coupled plasma mass spectrometry (ICP/MS) and solid scintillation beta counting. The resulting detection methods allow complete evaluation of all stable (non-radioactive) and many radioactive REE fission products. The two detection methods (ICP/MS and Beta) illustrate how mass selective and radiometric data can be used to provide complimentary information regarding the isotopic characterization of radioactive samples.

Selective, high-energy beta scintillation sensor for real-time, in situ characterization of uranium-238 and strontium-90

A novel scintillating-fiber sensor for detecting high-energy beta particles has been designed and built at the Pacific Northwest Laboratory to characterize238U and90Sr in surface soils. High-energy betas generate unique signals as they pass through multiple layers of scintillating fibers that make up the active region of the detector. Lower-energy beta particles, gamma rays, and cosmic-ray-generated particles comprise the majority of the background interferences. The resulting signals produced by these latter phenomena are effectively discriminated against due to the combination of the sensor's multi-layer configuration and its interlayer coincidence/anti-coincidence circuitry.

Characterization and calibration of a large area beta scintillation detector for determination of Sr-90

A large area beta scintillation detector has been developed which is currently capable of determining Sr-90/Y-90 contamination in surficial soils. The detector system employs scintillating fiber optic arrays, with active dimensions approximately 15 cm wide by 100 cm long, both ends of which are coupled to multiple photomultiplier tubes (PMTs). Electronic processing includes coincidence requirements to optimize sensitivity and selectivity for the 2.28 MeV (maximum) beta particle from Y-90. Low energy beta particles and gamma rays are discriminated against using double ended and multi-layer coincidence requirements. The detector system is personal-computer-software controlled and data restored in a format compatible with standard database software for ease of final data reduction. Experimental calibration studies have shown a linear response for Sr-90/Y-90 soil concentrations from 12 to over 500 pCi/g and a discrimination factor of 50 to 1 versus Cs-137.

A flow-through detector for nano-Curie activities encountered in HPLC analysis of PET tracer metabolites

The need for a flow-through detector with high efficiency and vanishingly low background arises in HPLC (high-pressure liquid chromatography) analysis of PET (positron emission tomography) tracer metabolites, where the free drug input function must be separated from the total circulating activity in sequential blood samples. Subnanocurie activities of positron emitters in 100 mu l plasma samples are chemically resolved, and then assayed by a triple coincidence beta - gamma - gamma -detector. Multiple coincidence logic between a BC-400 plastic scintillator flow-cell, sandwiched between two large NaI(Tl) gamma detectors, reduces the background event rate to 10/sup -3/ to 10/sup -6/ counts per second, with an overall efficiency of 25% for /sup 18/F-labeled eluates. Careful attention is paid to the construction of the beta cell, maintaining the chemical resolution of the HPLC system while optically transporting the few beta scintillation photons to multiple photomultipliers without losing the solid angle to the surrounding mantle of gamma detectors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Spectrometry and Visualisation of 'Standard' Hot Particles from the Chernobyl Accident

The nuclide composition of five fuel hot particles is reported. A comparison with the content of standard type hot particles and reactor fuel is performed. The activities of the hot particles under investigation were determined by gamma and alpha spectrometry. An investigation by scintillation beta spectrometry was carried out for one of the hot particles, and the content of pure beta emitters determined. Methods and techniques for visualisation of these hot particles using scanning electron microscopy (SEM) are described

A Proposed Multi-detector Method for Prompt 90Sr Detection in Post-accident Environmental Matrices

Strontium-90 is of relevant biological importance among fission products released during a fission reactor accident. Rapid information on its concentration in environmental matrices is extremely valuable, yet this implies chemical separations and handling with a shift in daughter equilibrium and therefore the need to wait a sufficient time for the equilibrium to be reestablished. The work concerns a feasibility study of a multi-detector system for a prompt evaluation of the 90Sr activity or, at least, a prompt determination of its order of magnitude in the presence of other pure beta and beta-gamma emitters; their interferences are examined on the basis of the Chernobyl releases and their decay properties. The technique is based on a plastic scintillator beta detector and a guard ring of BGO counters which can be logically connected in coincidence and anticoincidence. The evaluations show that a few hours are sufficient to determine a specific activity comparable with the Maximum Permissible Concentration in air by sampling 10 m3.

Validation of a Direct Radioimmunoassay of Melatonin in the Blue Fox

A direct radioimmunoassay procedure for the determination of melatonin in the blood of blue fox has been validated and applied. The assay required 50 μl of sample and standard, 100 ul of antiserum and 100 μl of (3H)melatonin. After overnight incubation at 4°C the antibody bound melatonin was separated from the free hormone with dextran-coated charcoal. Following centrifugation the antibody bound (3H)melatonin was determined in a beta scintillation counter. The antiserum bound 30–35 % of the (3H)melatonin at a final dilution of 1:36000. The non specific binding represented less than 5% of the total radioactivity in all assays. The lowest detectable amount of melatonin was 2.6 fmol/tube, corresponding to 52.5 pmol/1. The inter-assay coefficient of variation at 178 and 510 pmol/1 was 15.6 and 8.8%, respectively. The precision profile, calculated from a 10-replicate standard curve, showed that the coefficient of variation decreased from 43% at 84 pmol/1 to 15% at 336 pmol/1, and remainded at or below 10% for concentrations exceeding 670 pmol/1. Plasma was collected from 2 male blue foxes at about hourly intervals during a 24 h period in September and assayed for melatonin. Maximum (421 pmol/1) and minimum (97 pmol/1) concentrations of the hormone were inversely related to light intensity.

Micromethod for assaying reverse transcriptase of human T-cell lymphotropic virus type III/lymphadenopathy-associated virus

A micromethod for assaying the reverse transcriptase enzyme of human T-cell lymphotropic virus type III/lymphadenopathy-associated virus in cocultures of clinical specimens for viral isolation was developed and compared with the macromethod in use. Ultracentrifuged, pelleted, and solubilized viral culture supernatants were transferred into either tubes (macromethod) or microtiter plates (micromethod) and incubated with tritiated enzyme substrate. Trichloroacetic acid-precipitated DNA was collected on individual filter papers with a Millipore filtration manifold (macromethod) or on filter sheets using a semiautomated cell harvester (micromethod). Filters were then placed in scintillation fluid and counted on a beta scintillation counter. Results of the micromethod significantly correlated to those of the macromethod, with a linear relationship between the two. The cutoffs for positivity based on the mean + 2 standard deviations for a set of known negative specimens (n = 19) was 4,973 cpm for the micromethod compared with 5,336 for the macromethod. The intrarun and interrun variations were comparable for both methods. There was a 67% increase in the maximal daily number of specimens which could be run (100 versus 60) as well as a reduction in reagent use. In summary, the micromethod utilizing a semiautomated cell harvester is comparable to the existing macromethod in accuracy and is an improvement due to savings in time and reagents.

Pulsed cathode luminescence of bismuth germanate

This paper presents the results of spectroscopic kinetic investigation of the pulsed cathode luminescence (CL) in the alpha, beta and gamma scintillation of BGO (Bi/sub 4/Ge/sub 3/O/sub 12/) crystals. The single crystals of bismuth orthogermanate were grown according to the Czochralski method in platinum crucibles. The cathode luminescence was studied in the 80-500/sup 0/K range with excitation by a beam of electrons with j = 1 A/cm/sup 2/, a lifetime t/sub 0.5/ = 10nsec., and a maximum energy of 200 keV. Radionuclides were used for the investigation of the scintillation properties. Results include the discovery of broadband short-wavelength luminescence in the 2.5-4-eV range, which makes the main contribution to the fast nanosecond scintillation component. The investigation of the form of the scintillation pulses in BGO revealed protracted fronts for the beginning of luminescence and a characteristic ''rounded'' peak for the scintillation pulse. The UV luminescence band discovered, as well as the features of the kinetics of the pulsed CL, are similar to those in CaWO/sub 4/. Therefore, the excitation model first proposed for calcium tungstate and considered as applied to BGO fairly completely reflects the mechanisms for the transfer of luminescence energy and the act of scintillation.

Process monitoring of tritium concentration

Tritium fueling and recycling processes for the fusion industry need measurements of tritium concentrations, at various points, for control decisions. A prototype process sampling and analysis system built to monitor tritium concentration in a thermal diffusion column (used to enrich tritium) is described. The system draws a 2‐cm3 gas sample from a selected point and analyzes tritium concentration. Concentration is determined using a beta scintillation detector to measure the tritium partial pressure in ratio to the total sample pressure measured, using a 1 Torr capacitance manometer. The percent relative (% rel) calibration accuracy of the beta scintillation detector is 1.4% rel/°C plus the electrometer zero drift. Accuracies ≤6% rel for 1 mol % of tritium reducing to ≤1.5% rel at 90 mol% tritium are routinely produced in a typical air‐conditioned laboratory. Temperature control of ±0.1 °C improves accuracies to one‐fifth the level for ambient conditions. For high purity tritium (>90 mol%), a miniature quadrupole mass spectrometer with Faraday ion detection is required to assay tritium purity by differences (100% minus nontritium components). The detection limits of 0.2 mol% for DT and 0.5 mol% for HT and HD place ultimate limits on purity measurements. The sampling and analysis system is fully automated allowing arbitrary sampling points or a timed sampling sequence. A method is also presented for direct measurement of tritium partial pressure in exhaust lines of a fusion device.

Passage of beta particles through dielectrics in presence of an electric field

The effect of an electric field on the passage of thallium-204 beta particles through polymethyl methacrylate, polystyrene, polyethylene terephthalate (Lavsan), and polyethylene targets was investigated. The number of transmitted beta particles and their angular and energy distributions were determined. The transmission curves were obtained with a SBT-7 counter. The angular distribution was investigated in a specially designed scattering chamber, and the energy distribution was determined with a scintillation beta spectrometer incorporating the USD-1 and AI-100 instruments. It was found that the relative change in the number of transmitted beta particles depends on the size of the entrance solid angle, depends linearly on the potential difference applied to the dielectric, and is practically independent of the dielectric material if its thickness is expressed in mass units. It was also found that the relative change in angular distribution up to 60° with potential differences of not more than 10 kV is independent of the scattering angle. The energy distribution is not only shifted on the energy scale, but its shape is also altered. The results are attributed to the effect of the electric field on both the energy of the particles and the direction of their momentum. A simple method of calculating the effect of the field on the number of transmitted beta particles is proposed. The results of calculation agree with the experimental data.

Backscattering of electrons from phosphors and a matrix method for correcting backscattering and resolution in scintillation beta spectrometers

The response functions for monoenergetic electrons incident on anthracene, plastic and cesium iodide phosphors have been studied. A matrix method for correcting beta spectra for resolution and backscattering has been proposed and applied to electron spectra. The difficulties of applying backscattering correction to positron spectra have been discussed and a method of eliminating backscattering has been studied. The technique has been used to determine the end energy of the weak 1.8-MeV positron group from 22Na.

Decay Of Eu159

The decay scheme of Eu 159 was investigated by using beta and gamma ray scintillation spectrometers with a fast-slow coincidence circuit. The half-life of Eu 159 was measured as 19.0±0.5 min. Beta rays with end-point energies 2.57±0.05, 2.35±0.05, 1.90±0.05, 1.75±0.05, 1.50±0.05 and 1.0±0.1 MeV, and gamma rays with energies 1500, 1100, 800, 670, 220, 145, 130, 90 and 75 keV were found. On the bases of the experimental results obtained by β-γ, γ-β and γ-γ coincidence measurements, a tentative decay scheme of Eu 159 was proposed. The assignments of the excited levels were made based on the Nilsson model and the systematics in neighbouring odd-N nuclei. The systematic behaviour of low excited levels of gadolinium isotopes and N =95 isotones are discussed.

Internal conversion coefficients employing internal-external-conversion technique using a scintillation spectrometer

A beta scintillation spectrometer with a well type of plastic phosphor is assembled for the measurement of total internal conversion coefficients employing the internal-external-conversion technique. With foils of elements ranging from lead to copper as external converters, measurements were made and the values obtained for the total ICC are 0.112 ± 0.011 and 0.21 ± 0.03 for the 661 keV and 279 keV transitions of 137Ba and 203Tl isotopes respectively. The deduced α κ values are in satisfactory agreement with the theoretical values.

Decay of Eu159

The decay scheme of Eu 159 was investigated by using beta and gamma ray scintillation spectrometers with a fast-slow coincidence circuit. The half-life of Eu 159 was measured as 19.0±0.5 min. Beta rays with end-point energies 2.57±0.05, 2.35±0.05, 1.90±0.05, 1.75±0.05, 1.50±0.05 and 1.0±0.1 MeV, and gamma rays with energies 1500, 1100, 800, 670, 220, 145, 130, 90 and 75 keV were found. On the bases of the experimental results obtained by β-γ, γ-β and γ-γ coincidence measurements, a tentative decay scheme of Eu 159 was proposed. The assignments of the excited levels were made based on the Nilsson model and the systematics in neighbouring odd-N nuclei. The systematic behaviour of low excited levels of gadolinium isotopes and N =95 isotones are discussed.

An improved scintillation beta spectrometer

A scintillation beta spectrometer using NaI(Tl) as detector has been constructed and tested. The spectrometer shows a resolution of 8.3% on the 624 keV conversion electron peak of Ce 137.

Decay ofNd149toPm149

The radiations from the decay of the 1.8-h /sup 149/Nd were investigated using an intermediate-image beta spectrometer and scintillation coincidence spectrometers in conjunction with a 512-channel analyzer. Various gamma-gamma and beta-gamma coincidence measurements, not reported earlier, were made in order to establish the decay scheme with improved techniques. The beta spectrum showed four major components with end-point energies 1555 kev (6%), 1425 kev (38%), 1130 kev (26%), and 1025 kev (30%). The singles gamma spectrum showed the following gamma rays: 650 kev. The 62, 80, 158, 272, and 330-kev gamma rays were not reported earlier. To explnin the various gammagamma and beta-gamma coincidences a new decay scheme with levels in /sup 149/Pm at 114, 210, 272, 352, 510, 538, 650, and 750 kev is proposed, The K-conversion coefficient of the 114-kev transition, which is not determined earlier, was measured and is found to be 0.83 plus or minus 0.1. (auth)

Nuclear levels of 199Au

The low energy level scheme of 199Au as observed in the decay of 30 min acitivity of 199Pt has been studied using an intermediate image beta ray spectrometer and scintillation coincidence spectrometers in conjunction with a 512-channel analyser. Four beta groups of end-point energies at 1690±50, 1370, 1150 and 900 keV have been identified. The gamma-rays of energies 75, 197, 245, 320, 475, 540, 715, 790 and 960 keV were observed in the scintillation spectrum. To explain the various β-γ, γ-β and γ-γ coincidences and their relative intensities, levels at 75, 320, 475, 540, 737, 790 and 960 keV have been proposed. This new level scheme of 199Au shows a close similarity with those of neighbouring odd-mass gold nuclei. An isomeric state at about 475 keV has been identified, also suggesting a possible existence of the h 11 2 state in the 199Au nucleus.