Liquid Scintillation Technique Research Articles

Testing a biexponential kinetic model for the heterogeneous isotopic exchange of phosphate ions on several types of soil

In this study, a new kinetic equation was applied for the heterogeneous isotopic exchange of phosphate ions on soil. Phosphate sorption on chernozem, marshy meadow and meadow soil was studied by P-32 heterogeneous isotopic exchange in steady-state. The soil samples were incubated with 5 different amounts of KH2PO4 for 1, 3, 13, 10, 12 and 22 weeks. Then they were equilibrated with destilled water, and after the equilibrium was reached, H332PO4 radiotracer was added to the soil solution. At different times samples were taken from the soil solution, and radioactivities were determined by liquid scintillation (LSC) technique. The concentration of phosphate ions was determined by photometry. The relative radioactivity of soil vs time could be fitted well by the biexponential kinetic equation, which assumes two types of weakly bonded phosphate. From the fitting parameters of the biexponential equation and the phosphate concentration determined by photometry the amounts of the two types of weakly bonded phosphate and their steady-state rates were determined. The amounts of weakly bonded phosphate were plotted vs phosphate concentration – data points could be fitted by a Langmuir-like representation or the S-shape sorption isotherms. The rate orders of the desorption proved to be 1 or 2; rate constants were determined. It can be concluded that in some cases cooperative sorption can occure, which can be due to hydrogen bonding between the hydrogenphosphate ions on the surface.

Determination of Tritium-Helium-3 differential cross-section in the energy range between 0.6 MeV and 3.3 MeV for tritium depth profiling in solids

The differential cross-section for the 3He+3H nuclear reaction was measured in a thin tritiated PdTi film that was deposited on a Si wafer. The sample was loaded with 3H2 gas at a temperature of 300 °C and at a pressure of 1.8 bar. The total activity of the sample, measured by the liquid scintillation technique, was found to be 395 MBq. Two peaks were observed in the spectrum of the thick Si detector, corresponding to the 3H(3He,d)4He and 3H(3He,p)5He reaction channels. The differential cross-section was determined for the energy range of the 3He beam from 0.6 to 3.4 MeV, at three scattering angles of 125, 135 and 155°. The differential cross-section for the first channel remained almost constant within the measured energy range, while the cross-section for the second channel increased with energy. In both cases, the cross-sections reached their maximum value at the lowest scattering angle measured. The differential cross-sections were verified using a thick solid tritiated tungsten target. For assessing the tritium depth profile, only the reaction channel 3H(3He,d)4He can be utilized.

Novel technique for simultaneous detecting three naturally occurring radon isotopes (222Rn, 220Rn and 219Rn)

Radon inspection is becoming increasingly prevalent due to its negative effects on human health. After cigarette smoking, radon is the second leading cause of lung cancer due to its internal dosage through respiration. In this study, we employed a novel liquid scintillation technique to simultaneously detect three naturally occurring radon isotopes (222Rn, 220Rn and 219Rn). The detection method utilises the delayed coincidence technique and the pulse shape discrimination implemented by digital charge comparison. Furthermore, a Monte Carlo simulation was performed to obtain the gamma response functions of the detector using standard 22Na, 60Co and 137Cs gamma sources. Additionally, the detector resolution and energy calibration parameters were determined by comparing the measured and simulated light output distributions. For the measurement, radon gas from the atmosphere was infused into 700 mL of Ultima Gold AB for 48 h. We determined that the minimum detectable activities of 222Rn (238U decay chain), 220Rn (232 Th day chain) and 219Rn (235U decay chain) were 1.7, 1.0 and 1.2 mBq/l, respectively. The proposed novel technique offers a potential application for detecting all three naturally occurring radon isotopes in water samples.

Applications of PERALS-Alpha Spectrometry for the Investigation of Radionuclides in Water Samples.

In this paper, experiences of the last 20 years with the PERALS-technique are described. PERALS stands for photo electron-rejecting alpha liquid scintillation. This liquid scintillation technique was developed by Jack McDowell in the 1970s and is a powerful technique for the analyses of many natural alpha nuclides and also the beta nuclide 90Sr. The principle is based on a selective extraction of the radionuclide from the water phase by means of a complexing or ion pair reagent. The extractant contains also a cocktail suitable for scintillation counting. Therefore, the extract can be analyzed directly after the extraction step. After removing quenchers, such as oxygen, and the proper setting of a pulse shape discriminator, alpha pulses can be counted with a photomultiplier. This paper describes the development of robust analysis schemes for the determination of traces of polonium, thorium, uranium and other actinides in water samples (groundwater, rain water, river water, drinking water, mineral water, sea water). For radon and radium, the enrichment in the extract is poor. Therefore, PERALS methods are not suitable for trace analyses of these analytes. In addition, the extraction of the beta-emitter 90Sr with a PERALS cocktail is discussed, even though its beta spectrum is not analyzed with a PERALS counter. Results from the survey of drinking water and mineral water in Switzerland are presented for every radio element.

The potential radio-immunotherapeutic α-emitter 227Th – part I: Standardisation via primary liquid scintillation techniques and decay progeny ingrowth measurements

Thorium-227 is a potential therapeutic radionuclide for applications in targeted α-radioimmunotherapy for the treatment of various types of cancer. To provide nuclear medicine departments involved in Phase I clinical trials traceability to the SI unit of radioactivity (Bq), a standardisation of a radiochemically pure 227Th aqueous solution has been performed at the National Physical Laboratory. This was achieved via two primary liquid scintillation (LS) techniques −4π(LS)-γ digital coincidence counting (DCC) and 4π LS counting. These absolute techniques were supported by the indirect determination of the 227Th activity via the measurement of the ingrowth and decay rate of the decay progeny by both ionisations chambers and high purity germanium (HPGe) gamma-ray spectrometry. The results of the primary techniques were found to be consistent, both with each other (zeta score = 1.1) and to the decay progeny ingrowth measurements. An activity per unit mass of 20.726 (51) kBq g−1 was determined for the solution. A procedure has been developed that provided an effective separation of the 227Th from its decay progeny, which was shown by the effective time zero of the 227Th-223Ra nuclear chronometer measured by HPGe gamma-ray spectrometry.

Desenvolvimento de técnicas de bioanálise in vitro para monitoração individual de 32P

The 32 P is used in the form of liquid unsealed sources in medical facilities, research and teaching, representing a risk of internal exposure in routine activities and in case of accidental incorporation. The evaluation of 32 P incorporation can be accomplished through in vitro bioanalysis of urine. This paper aims to provide a methodology to analyze 32 P in biological samples, applicable to internal individual monitoring using liquid scintillation technique. The minimum detectable activity of the system was determined and the sensitivity of the technique was evaluated, based on the detected minimum effective dose.

Studies on matrix interferences during uranium analysis by extractive liquid scintillation technique

The efficiency of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) in reducing the influence of salinity and extraction of iron and calcium into the organic phase along with uranium was studied. DTPA has been observed to be more suitable complexing agent compared to EDTA. Iron and calcium were found to be separated quantitatively with more than 95% recovery for uranium, facilitating its rapid and interference free analysis in the presence of DTPA. Uranium recovery under high salinity conditions was also observed to be in the range 89.7–98.6% in the presence of DTPA.

Influence of natural radium contamination of barium chloride on the determination of radium isotopes in the water samples using α/β liquid scintillation spectrometry

Abstract The determination of radium isotopes in drinking water by liquid scintillation technique requires some reagents that are used for separating radium from water samples. One of the main reagents is BaCl2·H2O. This paper presents the study of this compound and shows that barium chloride reagent is naturally contaminated with226Ra. The 226Ra activity concentration in BaCl2·H2O reagent produced by chemical companies from Poland and other countries is equal to a few dozen Bq/kg. Furthermore, 14 mL of 0.10 M BaCl2·H2O solution is the optimum amount which should be used for the chemical procedure. At the optimum amount of barium chloride and 2-hour measurement, the detection limit of 226Ra and 228Ra of the liquid scintillation counting method is equal to 5 and 30 mBq per sample, respectively.

Natural radioactivity content in groundwater of Mt. Etna’s eastern flank and gamma background of surrounding rocks.

<p>Waters of Mt. Etna are the main source of drinking water for the local population and are also distributed in municipal supply systems to neighbouring areas. Radioactivity in underground waters and surrounding rocks from the eastern flank of Mt.Etnawas investigated on the basis of 9 water and 8 rocks samples from 12 localities altogether. Three samples were from water drainage galleries and six from water wells. All water intakes are used for consumption. Activity concentration of uranium isotopes <sup>234,238</sup>U, radium isotopes <sup>226,228</sup>Ra and radon <sup>222</sup>Rn were determined with the use different nuclear spectrometry techniques. The determination of uranium isotopes was carried out with the use of alpha spectrometry. The measurements of radium and radon activity concentration in water were performed with the use of a liquid scintillation technique. Additionally, rocks surrounding the intakes were examined with gamma spectrometry. All water samples showed uranium concentration above Minimum Detectable Activity (MDA), with the highest total uranium (<sup>234</sup>U + <sup>238</sup>U) activity concentration equal to 149.2±6 mBq/L. Conversely, all samples showed radium isotopes activity concentrations below MDA. Radon activity concentration was within the range from 2.91±0.36 to 21.21±1.10 Bq/L, hence these waters can be classified as low – radon waters. Gamma natural background of the rocks surrounding the water sampling sites was found on the same levels as other volcanic rocks of Italy.</p>

Revisiting the Early BARC Tritium Results

Within days of the F&P announcement of 1989, several groups at BARC embarked on a program to look for the generation of neutrons and tritium when deuterium (or hydrogen) is loaded into metals such as Pd, Ti and Ni. Electrolytic, gas and plasma loading techniques were deployed. Post run electrolyte samples were analyzed for tritium content using standard liquid scintillation techniques. In the case of gas and plasma loaded “dry” samples, surface tritium content was measured directly using windowless beta counters. Autoradiography was deployed as a very effective tool to monitor the spatial distribution of tritium in the near surface layers of test samples. The first confirmation of copious tritium generation was obtained on 21 April 1989 in a commercial “Milton Roy” Pd–D2O electrolytic cell. The results obtained during the first year of the BARC Cold Fusion campaign were presented at ICCF 1 in March 1990 where we reported observing tritium generation in 22 different electrolytic cells, which were set up totally independently by diverse research groups. The present paper revisits the early BARC tritium results obtained in a variety of experimental configurations during the period 1989–1996.

Crosslinked plastic scintillators: A new detection system for radioactivity measurement in organic and aggressive media

The measurement of radioactive solutions containing organic or aggressive media may cause stability problems in liquid and plastic scintillation (PS) techniques. In the case of PS, this can be overcome by adding a crosslinker to the polymer structure. The objectives of this study are to synthesise a suitable crosslinked plastic scintillator (C-PS) for radioactivity determination in organic and aggressive media. The results indicated that an increase in the crosslinker content reduces the detection efficiency and a more flexible crosslinker yields higher detection efficiency. For the polymer composition studied, 2,5-diphenyloxazole (PPO) is the most adequate fluorescent solute and an increase in its concentration causes little change in the detection efficiency. The inclusion of a secondary fluorescent solute 1,4-bis-2-(5-phenyloxazolyl) benzene (POPOP) improves the C-PS radiometrical characteristics. For the final composition chosen, the synthesis of the C-PS exhibits good reproducibility with elevated yield. The obtained C-PS also displays high stability in different organic (toluene, hydrotreated vegetable oil (HVO) and methanol) and aggressive media (hydrochloric acid, nitric acid and hydrogen peroxide). Finally, the C-PS exhibits high detection efficiency both in water and in aggressive media and can also be applied in organic media showing similar or even higher detection efficiency values.

Direct measurement of tritium production rate in LiPb with removed parasitic activities: Preliminary experiments

Liquid scintillation (LS) technique applied to direct measurement of tritium activity produced in LiPb eutectic in Frascati HCLL TBM mock-up neutronic experiment has been tested so far in the case of LS measurement after long period since irradiation. LiPb samples irradiated in neutron filed show, except of tritium, meaningful activity of other radioisotopes (parasitic). Parasitic activity, mainly from isotopes of lead (209Pb, 204mPb, 203Pb) calculated with the use of FISPACT, exceeds ca 5 times tritium activity 1.4h after irradiation. We propose to remove disturbing radioisotopes in a chemical way to avoid long “cooling” of the irradiated samples before tritium measurement. Samples (1g of LiPb) irradiated in reactor fast neutron flux were diluted and metallic cations removed by chemical precipitation. For this purpose we used: potassium iodide (KJ), strontium chloride (SrCl2), APDC (C5H8NS2·NH4), NaDDTC (C5H10NNaS2·3H2O), and PAN (C15H11N3O). Precipitation procedure in each case lasted ca 5–25min, and the following filtration next 10–20min. In each filtrate (ca 120ml) we measured Pb concentration in total reflection X-ray fluorescence (TXRF) analyzer and parasitic activity (left after 21-day “cooling”) applying HPGe gamma spectrometer. Pb cations precipitated by SrCl2 and than by PAN lowered activity of Pb isotopes to less than 1% of the initial tritium activity. Another combination of reagents: NaDDTC followed by SrCl2 in a single and double step filtration reduced Pb concentration 102 and 104 times, respectively. Reduction of this order allows tritium radiometric measurement ca 3h after irradiation with acceptable accuracy. This time can be shortened by applying correction for decay of known parasitic activity. Input of 76As and other less abundant radioisotopes can be eliminated using high purity LiPb. Tritium activity of the filtrates measured in LS spectrometer showed no dependence upon used reagent being, within measurement error, the same as for analyzed LiPb samples.

Radon (222Rn) in underground drinking water supplies of the Southern Greater Poland Region.

Activity concentration of the 222Rn radionuclide was determined in drinking water samples from the Sothern Greater Poland region by liquid scintillation technique. The measured values ranged from 0.42 to 10.52 Bq/dm3 with the geometric mean value of 1.92 Bq/dm3. The calculated average annual effective doses from ingestion with water and inhalation of this radionuclide escaping from water were 1.15 and 11.8 μSv, respectively. Therefore, it should be underlined that, generally, it’s not the ingestion of natural radionuclides with water but inhalation of the radon escaping from water which is a substantial part of the radiological hazard due to the presence of the natural radionuclides from the uranium and thorium series in the drinking water.

Alpha/beta indices determination in drinking water using plastic scintillation and evaporation to dryness

Alpha/beta indices are screening parameters that provide a quick approach to the determination of the radioactivity levels of water samples. These indices have commonly been determined by methods involving measurement by proportional counter or liquid scintillation (LS) techniques. However, both of these types of techniques present some limitations. Plastic scintillation (PS) is an alternative technique that does not generate mixed wastes and also provides a solid surface onto which the sample can be evaporated. The objective of this study is to evaluate a new procedure for the determination of alpha/beta indices using PS microspheres and evaporation to dryness. For this purpose, the capabilities of this technique were first compared with those of LS and PS in solution. Various parameters were then optimised: the diameter of the microspheres, the discrimination values and the evaporation system. Next, the calibration procedure was established, and finally, the procedure was validated with the analysis of spiked water samples. The results show that this technique can be applied for alpha/beta indices determination with a simple procedure, high detection efficiency and acceptable uncertainties.

Tritium production rate in HCLL TBM: Conception of a measurement system with application of liquid scintillation technique

Validation of the calculated Tritium Production Rate (TPR) in the Test Blanket Modules (TBMs) needs relatively simple measurement procedure. Measurement system in TBM based on Tritium determination directly in LiPb and/or in Li compound(s) with application of the Liquid Scintillator Counting (LSC) is proposed. Expected high temperature in TBM while ITER operation in sample not less than 150°C when cooled irradiated material, and 300–400°C without cooling, impose constraints on the possible methods and technical design. Preliminary results performed on irradiated LiPb eutectic pellets housed at controlled conditions of elevated temperature showed remarkable loss of Tritium. Observed escape of Tritium ranged from ca. 91% (temp.: 300°C, t=60min) to ca. 52% (temp.: 370–390°C, t=10min) being in fair agreement with calculated values by use of dedicated code (rCADiff). Basic limitation of direct radiometric measurement of Tritium activity in LiPb is parasitic activity induced in Pb, predominantly coming from 203Pb and also from impurities present in Pb. Demand of obtaining information on TPR in relatively short time points to other lithium compounds used as monitors which after irradiation, followed by an easy preparation procedure, can be measured using simple version of LSC. Most promising monitors seem to be Li2O and LiF. Two different possible versions of the proposed systems were considered: (1) LSC measurement starts after long period of time since irradiation (not less than 20 days); (2) LSC measurement starts shortly after irradiation (an hour or less to several hours).

Endogenous Content and Release of [3H]-GABA and [3H]-Glutamate in the Spinal Cord of Chronically Undernourished Rat

The aim of this study was to determine the effect of chronic undernutrition on the content and release of γ-amino butyric acid (GABA) and glutamate (GLU) transmitters in the rat spinal cord. The release of [(3)H]-GABA and [(3)H]-GLU was determined by radioactive liquid scintillation techniques, and the concentrations of GABA and GLU in spinal cord preparations from control and undernourished young rats (50-60 days old) were measured by reverse-phase HPLC. The GABA and GLU contents in the lumbar spinal dorsal horn (L6 segment) were significantly lower in undernourished rats relative to control rats (22.2 ± 3.7 and 10.7 ± 1.9 %, respectively; P < 0.05). Spinal cord blocks from undernourished animals also showed lower rates of [(3)H]-GABA and [(3)H]-GLU release than controls (27.6 ± 3.5 and 12.8 ± 2.5 %, respectively; P < 0.01). We propose that the decreases in GLU content and release are consistent with a reduced activation of either afferent fibers, spinal glutaminergic neurons, or both. Furthermore, we propose that the decreased content and release of GABA in undernourished animals are related to a depression in pre- and post-synaptic inhibition. In addition, we hypothesize that the reductions in GABA content and release serve as compensatory mechanisms to counterbalance decreases in sensory transmission and GLU content in the spinal cord of the chronically undernourished rat.

Measurement of tritium production rate distribution in natural LiAlO2/HDPE assembly irradiated by D-T neutrons

A neutronics experiment was performed to measure the tritium production rate (TPR) profile in the breeder assembly with LiAlO2 as breeder and high density polyethylene (HDPE) as neutron reflector. The breeder assembly was irradiated with 14MeV neutrons from DT neutron generator at IPR Neutronics Laboratory. The objective of the experiment was to validate the tritium production prediction capability of the Monte-Carlo code MCNP and FENDL 2.1 data library. The tritium production rate profile in the breeding assembly was measured by irradiating Li2CO3 pellets kept at various locations and then tritium counting liquid scintillation technique. Experiment was analyzed with 3D Monte-Carlo code MCNP with FENDL 2.1 cross-section data library. The calculation results were found to agree with the measured tritium production rates except one point near to the source. This experiment is a starting experiment in the series of benchmark experiments for the Indian Demo breeding blanket.

Application of multi-way partial least squares calibration for simultaneous determination of radioisotopes by liquid scintillation technique

Three-way partial last squares (3-PLS2), as a multi-way calibration method was applied for determining the 235U/238U isotope ratio to overcome problems with spectral interferences in liquid scintillation spectra of these radioisotopes. The alpha energy spectra of samples in different energy channels and different cocktail to sample ratios were used as input data for 3-PLS2. The model was applied to a prediction set and satisfactory results were obtained. The 3-way PLS2 prediction results were compared with 2-way PLS2 and it was shown that 3-way PLS2 results are more accurate than the results of PLS2. Thermal ionization-mass spectrometry was used as a reference method for calculating the accuracy of our method.

Oscillation Analysis with and without Solar Term Using Super-K-I and Super-K-II Atmospheric Neutrino data

As part of the European LAGUNA design study on a next-generation neutrino detector, we propose the liquid-scintillator detector LENA (Low Energy Neutrino Astronomy) as a multipurpose neutrino observatory. The outstanding successes of the Borexino and KamLAND experiments demonstrate the large potential of liquid-scintillator detectors in low-energy neutrino physics. Low energy threshold, good energy resolution and efficient background discrimination are inherent to the liquid-scintillator technique. A target mass of 50 kt will offer a substantial increase in detection sensitivity.At low energies, the variety of detection channels available in liquid scintillator will allow for an energy – and flavor-resolved analysis of the neutrino burst emitted by a galactic Supernova. Due to target mass and background conditions, LENA will also be sensitive to the faint signal of the Diffuse Supernova Neutrino Background. Solar metallicity, time-variation in the solar neutrino flux and deviations from MSW–LMA survival probabilities can be investigated based on unprecedented statistics. Low background conditions allow to search for dark matter by observing rare annihilation neutrinos. The large number of events expected for geoneutrinos will give valuable information on the abundances of Uranium and Thorium and their relative ratio in the Earth’s crust and mantle. Reactor neutrinos enable a high-precision measurement of solar mixing parameters. A strong radioactive or pion decay-at-rest neutrino source can be placed close to the detector to investigate neutrino oscillations for short distances and sub-MeV to MeV energies.At high energies, LENA will provide a new lifetime limit for the SUSY-favored proton decay mode into kaon and antineutrino, surpassing current experimental limits by about one order of magnitude. Recent studies have demonstrated that a reconstruction of momentum and energy of GeV particles is well feasible in liquid scintillator. Monte Carlo studies on the reconstruction of the complex event topologies found for neutrino interactions at multi-GeV energies have shown promising results. If this is confirmed, LENA might serve as far detector in a long-baseline neutrino oscillation experiment currently investigated in LAGUNA-LBNO.

Intercomparison measurements of 222Rn concentration in water samples in Poland

The paper presents the results of intercalibration measurements of 222Rn concentration in water samples. The aim of the experiments was to evaluate the different measurement methods of radon determination in water samples performed by eleven laboratories in Poland and to test these methods in field work. In the years 2001–2003 three national intercomparison experiments were organized. The results allowed the participating laboratories to improve their measurement methodologies and to achieve better, i.e. more convergent results of determining radon concentration in water samples. The results show that the use of liquid-scintillation technique seems to be the best measurement method. It should be emphasized that comparative experiments are essential for all laboratories and they should be carried out as often as possible, based both on prepared samples with known concentration values of 222Rn and natural water samples, the most commonly used in laboratory practice.