Β-ray Energy Research Articles

Parametric optimization for estimating beta detection efficiency in thin plastic scintillation detector

A condenser air removal system plays a crucial role in radiation monitoring within nuclear power plants, specifically for detecting potential leaks of radioactive material from primary-to-secondary systems. This system assesses the leakage rate (LR) by measuring the emission of β particles from noble gases using a thin plastic scintillation (TPS) detector, which is specifically designed for counting purposes. Among the factors used in LR calculation, the detection efficiency (k) must be experimentally determined in advance. However, this is challenging because of the limitations posed by radiation safety regulations. Moreover, simulation-based calculations are difficult to achieve because only a portion of the β-ray energy is transferred in the TPS detectors, resulting in a lack of prior energy information. To overcome these challenges, this study employed a multi-objective parameter optimization technique to simultaneously calculate the parameters required for the β-ray detection response function and energy calibration equation. Subsequently, k values were calculated using the optimization results. The optimization performance was demonstrated by comparing the measured spectra of the TPS detector with the spectra obtained from the Monte Carlo N-particle simulation. Furthermore, we confirmed that the calculated k values agreed with the reference values.

Study on the γ + X, γ + β, γ + α Coincidence Summing Effects of the Intrinsic Background Instrument Spectrum of a LaBr3(Ce) Scintillation Counter

The energy resolution of a LaBr3(Ce) scintillation counter can reach 2.7% (662 keV) at room temperature. As a radiation measuring device, it has remarkably good characteristics. However, the LaBr3(Ce) crystal has its own intrinsic radioactivity background, which mainly comes from 138La and from 227Ac and its daughters. 138La can emit β, γ and X-rays through β and γ decay; 227Ac and its daughters can emit α, β and γ-rays through a, β and γ decay. α, β and X-ray energy are characteristic while β-ray energy is continuous. The energy of α, β and X-rays is mainly deposited in the crystal unless the α, β and X-rays at the edge of the crystal can escape from the crystal. Therefore, the α, β, γ and X-rays generated by the intrinsic radioactivity of the crystal are superimposed on the instrument spectrum, which makes the instrument spectrum more complicated and produces the coincidence summing effects of γ + X, γ + β and γ + α.In this research, the GEANT4.9.5 software package was used to simulate the spectra of α, β, γ and X-rays. On the basis of a combination of fitting decomposition and reconstruction, the simulation spectrum of the LaBr3(Ce) self-radioactive background was obtained accurately and was verified by using physical experiments.

The β-ray energy and angular response of the EYE-D™ eye-lens dosemeter

Following the recent ICRP recommendation to decrease the limit of occupational exposure to the eye lens from 150 mSv to 20 mSv/year, a dedicated individual eye-lens dosemeter, EYE-D™, was developed at the IFJ PAN. This dosemeter uses MCP-N (LiF:Mg,Cu,P) thermoluminescent detectors covered with a polyamide capsule and was so far optimized to achieve a flat photon energy and angular response for X-ray exposures typical in interventional radiology. To verify the applicability of this eye-lens dosemeter in external β-ray fields which arise, e.g. in nuclear medicine procedures, we measured and calculated its β-ray energy and angular response. Measurements, applying β-rays from Sr-90/Y-90 isotope, were performed at the Beta Secondary Standard type 2 (BSS 2) in CLOR. Calculations, using the PENELOPE Monte Carlo transport code which simulates coupled electron and photon transport in arbitrary materials, were performed for P-32, K-42 and Sr-90/Y-90 fields to simulate doses received by the eye lens within the human body. PENELOPE Monte Carlo transport code was also used to calculate doses received with EYE-D™ detectors. We found good agreement between the measured and calculated energy and angular responses which confirms the suitability of this dosemeter in assessing Hp(3) to estimate the eye lens. Obtained results and conclusions, however preliminary, conform with current ICRP recommendations when performing individual radiation protection dosimetry in external β-ray fields occurring in nuclear industry and nuclear medicine activities.

Observation of β-ray spectra after penetrating absorbing materials

β-Ray spectra after penetrating absorbing materials of various thicknesses were observed by the use of a scintillation-type β-ray spectrometer equipped with a flat NE-102 plastic scintillator of 5 mm thickness for sources of 60Co, 90Sr– 90Y, 137Cs, 147Pm and 204Tl. Although the spectra changed rapidly with increasing absorber thickness, the average β-ray energy was kept nearly constant for a wider range. These results are consistent in that the β-ray absorption curve becomes quasi-linear in a semi-logarithmic plot. Spectra including scattered β-rays from several materials placed behind the source were also measured for 137Cs and 204Tl. It may be concluded that mean energy measurements by the use of β-ray spectrometer of this kind is useful for the identification of nuclides in radiation protection purposes even in worse source-conditions.

皮膚汚染を模擬した線量評価用β線源を用いたサーベイメータの校正

A calibration method has been studied for the surveymeters used for estimating the doses from skin contamination. Two types of surveymeters with ionization chamber and GM tube were calibrated with newly developed β-ray sources simulating skin contamination. Ion-exchange membrane sources were used for preparation of the calibration sources. The tissue absorbed dose rates from the sources were directly determined with an extrapolation chamber.The ratios of the reading of surveymeter to the dose rate from the sources were measured about maximum β-ray energy, active area and source-to-detector distance. The ratios for the infinite plane source were reasonably determined with 6 calibration sources and many small membrane sources. Through the calibration works, the validity and reliability of this method were discussed.

Preparation of extended sources with homogeneous polyethylene ion-exchange membranes

The development of extended radionuclide sources by sorption on ion-exchange membranes is described. Conditions for the preparation of sources of 60Co, 137Cs, 90Sr-Y, 147Pm and 204Tl have been defined experimentally. β-ray counting efficiencies have been measured as functions of β-ray energy and membrane thickness. For sources 180 × 140 mm, the uniformity of the activity distribution per unit membrane mass was better than 1% for all of the radionuclides studied, with the exception of 147Pm for which it was about 3%.

Counting efficiency and colour quenching in measuring Cherenkov radiation

The counting efficiency of Cherenkov radiation by the liquid scintillation counter is studied in several solvents. The relation between the strength of the pulse height by the Cherenkov radiation and the maximum energy of β-rays was fairly proportional. The colour quenching can be corrected by measuring the absorbance of solution.

Calculation of efficiency functions in 4π β-γ counting

An attempt is made to calculate an efficiency function applicable to 4πβ-γ coincidence measurements as the first stage of evaluating the order of the polynomial of the fitting function. For this purpose, the β-ray energy spectra and self-absorptions of spherical particle sources are calculated by the Monte Carlo simulation under the continuous slowing down approximation. On the other hand, it is shown that three sets of absorption coefficients and partial intensity ratios corresponding to a β-ray group give analytically the self-absorption for the same particle sources. Finally, we show that the efficiency functions applicable to 59Fe and 134Cs are easily obtained by using the energy spectra or self-absorptions.

Z dependence of thick-target β-ray backscattering

Variation of β-ray backscattering with the atomic number of target material has been studied using thick targets of polythene, aluminum, iron, copper, zinc, tin, silver, tungsten, and lead for five β emitters, viz., 35S, 147Pm, 204Tl, 32P, and 90Sr-90Y. Effects of geometry and β-ray end-point energy have been investigated using a reflection geometry in which the geometry factors were varied by more than 40 and β-ray energy varied over a range 0.167–2.27 MeV. It is found that the mean value of the index of Z dependence of β-ray backscattering is 1.840.05 over these regions of geometry and energy. Deviations for soft β emitters have been confirmed as due to air absorption. The importance of these results in studies of two-component systems is emphasized.

β線吸収線量率測定器の開発 ディスクリミネータ・フィルタ併用法

A method and an instrument were developed for measuring directly the β-ray absorbed dose rate almost independent of β-ray energy and corresponding to the epidermal thickness of tissue. A discriminator, of which discrimination level was set according to the epidermal thickness of tissue, and a filter, controlling the number of incident β-rays, were used for obtaining a constant dose sensitivity (counting rate per absorbed dose rate). The filter was composed of two semicircular plates of acrylic resin, whose thickness was 25 and 1, 000mg/cmcm2, respectively. The shape of filter is a disk. The dose rate was obtained by subtracting the counting rate measured with the filter from that measured without the filter and by multiplying this remainder by a constant factor (reciprocal of the constant dose sensitivity).The dose sensitivity of instrument was constant at 40cps/(mrad/hr)±15% for β-rays with the maximum energy 0.35-3.5MeV (epidermal thickness: 7mg/cmcm2) and 0.3-3.5MeV (epidermal thickness: 40mg/cmcm2). The constant factor was 2.5×10-2(mrad/hr)/cps. The lower limit was 3.5×10-2mrad/hr(7mg/cmcm2) and 2.1×10-2mrad/hr(40mg/cmcm2).

Heavy isotopes of actinium: 229Ac, 230Ac, 231Ac and 232Ac

By irradiation of 232Th with 150-MeV bremsstrahlung and with 14-MeV neutrons, three new neutron-rich isotopes of actinium, 230Ac, 231Ac and 232Ac, were produced and identified and the previously reported isotope, 229Ac, was confirmed. The actinium isotopes were chemically isolated by a fast procedure based on elution with α-hydroxyisobutyric acid from cation exchange resins. For 229Ac, a half-life of 62·7 ± 0·5 min and a β-ray energy of 1·14 ± 0·15 MeV were found; 35 γ-rays were observed, the strongest ones with the following energies and relative intensities: 135·3(34), 146·4(35), 164·6(100), 252·2(24), 261·9(39), 317·0(23), 539·9(20), 569·1(91), and 605·2 keV(23). For 230Ac, a half-life of 80 ± 10 sec and γ-rays of 454·4(100) and 508·1 keV (58) were obtained. 231Ac was found to decay with a half-life of 7·5 ± 0·1 min. A total of 22 γ-rays were detected with the strongest ones at 185·6(43), 221·2(49), 240·6(11), 282·3(100), 306·9(77) and 368·8 keV (38). For 232Ac, a half-life of 35 ± 5 sec was obtained.

Decays of 114Sb and 112Sb

Decays of 114 Sb and 112 Sb were investigated with single and coincidence experiments. In the decay of 114 Sb, new γ rays at energies of 322 keV(5.5%), 393 keV(1.1%) and 716 keV(3.8%), were found, in addition to the known γ rays at energies of 887 keV(17.7%) and 1300 keV(100%). The highest β-ray end-point energy was obtained to be 4.1 MeV. The half-life of 114 Sb was determined to be 200±5 sec. In the decay of 112 Sb, γ rays at energies of 992 keV(12.1%) and 1258 keV(100%) were seen. The highest β-ray end-point energy was found to be 5.2 MeV. Decay schemes for 114 Sb and 112 Sb were proposed. Some properties of the decay schemes may be interpreted in terms of the pairing theory.

Radiometrische und Analytische Ausnützung der Natürlichen Instabilität von87Rb

Possibilities of radiometric determination of Rb in liquid and solid samples using87Rb are discussed. In spite of the relatively low β-ray energy of87Rb, it is possible to achieve relatively high total counting efficiency (up to 75%) using gas flow GM counters. This fact makes possible to use the natural instability of87Rb also for the purposes of calibration. In this paper the conditions of radiometric determination mainly of small amounts of Rb are described (minimum measurable amount is 0.07% of Rb).87Rb can be used for the minimum activity determination by measuring β-radiation in the interval of energy of 0.27 MeV.

530. 塩素の光核反応による無担体<SUP>33</SUP>Pの製造

Phosphorus-33 is a useful radioisotope of phosphorus for biological and medical restarch, for its long half life (25.4d) and low β-ray energy (0.25MeV) compared with 32P (14.3d, 1.70MeV).Two methods of production of this radioisotope in carrier free state have been already reported. 33S (n, p) reaction with reactor neutrons and 34S (γ, p) reaction with γ-rays from electron linear accelerator. These methods however use natural targets, and the resulting 33P/32P ratio is low.The present report describes a method for producing high ratio 33P/32P by 37Cl (γ, α) reaction with γ-rays from an electron linear accelerator giving a maximum energy of 18 MeV. For target material, NaCl and NH4Cl are taken up. The 33P/32P ratio of the phosphorus fraction after chemical separation with cation and anion exchange columns is about 12/1 at the end of irradiation when using NaCl as torget.

Discussion of paper by R. C. Whitten, I. G. Poppoff, R. S. Edmonds, and W. W. Berning, ‘Effective recombination coefficients in the lower ionosphere’

Whitten et al. [1965] (hereafter referred to as WPEB) recently inferred values of certain recombination coefficients from an experiment carried out during one of the high-altitude nuclear tests in 1962. In the experiment, measurements of the angular β-ray energy flux, dF/dΩ, were made from a rocket that also carried a phase-coherent three-frequency beacon. From the measured dF/dΩ, and a theoretical model for the β-ray energy spectrum at the detector, WPEB infer an electron production rate, q, using their equation 6. From the dispersive Doppler measurements of total electron content between beacon and receiver, with the assumption that horizontal gradients and time dependence of the electron number density are negligible, WPEB infer the electron number density at the rocket position, Ne.

Einfluß von festkörpereffekten auf die β-γ-Richtungskorrelation des 166Ho

The β-γ directional correlation of 166Ho has been measured in metal, oxide and chloride sources, in order to study the influence of solid state effects on the correlation. In metal sources an energy-independent attenuation factor G 2 = 0.356 ± 0.005 was found. The oxide and chloride sources showed attenuation factors which varied with the β-ray energy. Between 0.5 and 1.8 MeV G 2 was found to increase from 0.16 to 0.25 (oxide), and from 0.25 to 0.37 (chloride evaporated in vacuo).

Praseodymium-143 from Neutron-Irradiated Uranium

From neutron-irradiated uranium cooled for about 2 days, 143Pr was separated indirectly by solvent extraction. After removing uranium and some extractable nuclides with bis(2-ethyl hexyl)orthophosphoric acid from 10 M nitric acid solution, 143Ce was extracted with bis(2-ethyl hexyl) orthophosphoric acid (n-heptane diluent) from a 10 M nitric acid solution containing potassium bromate. Then, 143Pr was purified after most of the 143Ce had decayed off. Detailed measurements indicated a half-life of 13.55 ±0.02 days and maximum β-ray energy of 0.93±0.05 MeV.

Etude comparée de la mesure des activités bêta sur cpuches chromatographiques minces: Influence du détecteur, de la nature de la couche mince et de l'energie du rayonnement bêta

Comparative study of the measurement of β-activities on thin chromatographic layers: influence of the detector, of the nature of the thin layer and of the β-ray energy To measure β-activities on thin chromatographic layers of adsorbant or of ion-exchange resins we can employ either a Geiger-Müller counter or a gel scintillator combined with a photomultiplier. After re-stating the method of preparing the thin layers, particularly those of exchange resin, and also their treatment with a gel scintillator, the authors examine the effect of three factors (the thickness of the fluorescent gel, the β-ray energy and the nature of the thin layer) on the “relative statistical note” which is defined as the ratio: [(efficiency) 2proper movement] gel scintillator [(efficiency) 2proper movement] Geiger-M u ̈ ller . They proceed to show that the detection efficiency for C 14 on a thin layer of silica may exceed 75 per cent with a gel scintillator and that the fluorescence photons are not diffused in the thin layer, which is a condition for a satisfactory resolving power.

RADIATION EXPOSURE FROM RADIOIODINE COMPOUNDS IN PEDIATRICS.

The increasing use of radionuclides in diagnostic procedures and the importance of minimizing radiation exposure to infants and children necessitate accurate and detailed information concerning the doses sustained during these procedures. Although abundant data are available for dosages to adults (1.1, 35, 36) only an occasional reference is found to those received by children of various ages (12). Furthermore, much of the available information deals with exposure to the in-organic form of the radionuclide, while today many of the administered radionuclides are “tagged” to various organic molecules. Since these tagged substances are not handled by the body in the same manner as the inorganic compound, greater or less radiation exposure may result. This situation is particularly pertinent in the case of radioiodine which, because of its abundance, ease of detection, and chemical properties, has been incorporated as a tag for many organic compounds. Table III records the average whole-body radiation doses received by normal newborn infants, children of varying ages, and “standard man” for diagnostic tests employing various forms of radioiodine and, for comparison, those received during selected diagnostic radiographic procedures. Doses received by certain organs are shown in Tables IV and V. Since the amount of radioiodine used in a given test is likely to vary widely in different laboratories, the doses are calculated per micro-curie of administered compound. A short discussion of the metabolic fate of each of the compounds considered is presented, together with some necessary assumptions. Method of Calculation The radiation dose to a tissue is the sum of that received from beta and gamma radiation emanating from the radioactive material within the tissue, as well as that received from gamma radiation from sources distant from the tissue. Dose from radioactivity within the tissue: If an essentially uniform distribution of radionuclide within a tissue is assumed, and the volume of distribution is much larger than the range of the beta particles, the average absorbed dosages from beta radiation (Dβ) and from gamma radiation (Dγ) are calculated as follows (13); where 73.8 and 0.0346 are conversion factors to appropriate energy units E̅β is the average β-ray energy per disintegration in Mev. Iγ is the γ-ray dose rate constant in air in r/hr. at 1 cm. from 1 mc. ρ is the density of tissue in gm./c.c. g̅ is the average geometrical factor in cm. C0 is the initial concentration of the nuclide in the tissue in μc/gm. T is the effective half-life in days. These formulas give the radiation dose in rads. When considering doses of smaller magnitude, the use of the millirad is more convenient. A millirad is 1/1000 of a rad. E̅β and Iγ are characteristic of the particular radioactive isotope and may be obtained from various tables (10, 23); ρ for tissue is essentially 1.0.

富士γ線用バッジフィルムのβ線感度とβ線の被曝線量の評価

The sensitivities of Fuji Badge Film to β-rays were investigated using the isotopes, 35S, 185W, 204Tl, 32P, 90Sr-90Y and natural uranium plaque.Plane sources for exposure were prepared, and the contact radiography showed the uniformity of the source was within ±10% over the whole area, 5.5cmφ.The flux of β particles was counted with a G-M counter calibrated by 4π flow counter. The surface doses were calculated about the mean energy of β spectrum by Bethe-Bloch formula.The particle sensitivity was found to have the peak around 0.2 MeV in maximum energy which can be explained considering the relation between the range of β-rays and the thickness of emulsion coating.The dosage sensitivity was found to increase with β-ray energy and to be almost in flat maximum above 1.5 MeV in maximum energy.By using the results above, an example was shown how to estimate the apparent energy of incident β-rays and to evaluate the skin dose and the lens dose of eye with three plastic filters of JAERI Film Badge, Model III.