Pure Gamma Research Articles

Optimizing gamma-ray shielding for boron neutron capture therapy by using unglazed ceramic composites

In this study, the researchers investigated the effectiveness of different ceramic samples in filtering gamma rays emitted by various sources. The samples, which contained varying concentrations of lead and barium, were evaluated for their potential use in beam-shapingassembly systems for Boron Neutron Capture Therapy techniques, specifically those using the 252Cf neutron source for cancer treatment. Stilbene and NaI (Tl) were used to measure the total and pure gamma rays in this study. In addition, theoretical calculations using the Phy-X/PSD software have been conducted across a broad energy range, spanning from 0.001 to 18 MeV. These calculations aim to determine the attenuation of gamma rays and the relative deviations compared to the corresponding measured gamma-ray energies. Various composites with different percentages of additives and thicknesses, ranging from 0.8 cm to 4 cm, have shown satisfactory attenuation properties for gamma-ray shielding applications. However, the samples containing lead, especially the unglazed ceramic composites with 15 % lead and 4 cm thickness, were found to have the most preferred attenuation properties. The results obtained indicate that samples with a higher lead content are more effective attenuators compared to those with additional barium. In addition, the relationship between the transmission gamma ray factor and the percentage of additives and energies of gamma rays can be determined from the experimental linear attenuation coefficient coefficients. In addition, various coefficients such as the mass attenuation coefficient, half-value layer, effective atomic numbers, and effective electron densities are studied theoretically for the unglazed ceramic samples. The dose rate is also taken into consideration.

Preparation and color tuning of Ba2+-Sr2+ co-doped γ-Ce2S3 pigments

In this work, Ba2+-Sr2+ co-doped γ-Ce2S3 (γ-[Ba, Sr]-Ce2S3) pigments were synthesized by using a co-precipitation method with a composition of n (Ba)/n (Ce1-xSrx) = 0.1 (molar ratio, x = 0, 0.01, 0.03, 0.05, 0.10, 0.15, 0.20, 0.30, and 0.40 mol). The effect of the doping content of Sr2+ on vulcanization temperature, phase composition, band gap, chroma and temperature stability of γ-[Ba, Sr]-Ce2S3 pigments was systematically studied. The results show that a pure gamma phase γ-[Ba, Sr]-Ce2S3 can be obtained at 850 °C when x varied from 0 to 0.30. With increasing Sr2+ content, the band gap of γ-[Ba, Sr]-Ce2S3 increased from 2.016 to 2.258 eV, and thus the color of pigments had changed from red ((L* = 32.97, a* = 47.74, b* = 39.20 (x =0.00)) to orange (L* = 39.86, a* = 41.66, b* = 48.15 (x =0.15)) and then to yellow (L* = 51.28, a* = 30.83, b* = 58.30 (x = 0.30)), indicating that Ba2+-Sr2+co-doping can effectively tune the color of γ-Ce2S3. The temperature stability of γ-[Ba, Sr]-Ce2S3 pigments was also improved from 479.9 °C (x = 0) to 564.4 °C (x = 0.30).

Grain growth kinetics of the gamma phase metallic uranium

Metallic uranium is a leading fuel form for sodium cooled fast reactors as an enabling technology of future nuclear energy systems. Mechanistic understanding of fuel behaviors and kinetics under thermodynamic equilibrium and highly non-equilibrium conditions are essential for evaluating fuel performance. It is important to understand and predict the grain and pore evolutions of metallic fuels under thermal and irradiation conditions. However, very limited data are available on the grain growth kinetics and mechanisms of pure gamma phase uranium. In this paper, the pure gamma uranium pellets with different grain structures were fabricated by combining high-energy ball milling and spark plasma sintering. Isothermal annealing tests were performed to investigate the grain growth behavior of the pure gamma phase uranium with different initial grain sizes. A parabolic relationship in grain growth with time was identified for the submicron-sized (374 nm) sample. In contrast, for the nano-sized (137 nm) sample, the grain growth shows a linear relationship with time. The activation energies of grain growth were determined as 199.5 KJ/mol and 80.6 KJ/mol for nano-sized and submicron-sized grain structures, respectively. For the nano-sized sample, the rate-control step of grain growth is dominated by the triple-junction migration, in which the grain boundary triple junction drags the grain growth, leading to a higher activation energy than the bulk diffusion. The dominating mechanism for the submicron-sized sample is grain boundary diffusion. The mechanistic understanding and critical data obtained on the kinetics of pure uranium phases will be useful to evaluate fuel behavior under thermodynamic equilibrium conditions and develop a high fidelity model to predict fuel performance.

Neuroaspis PLP10™, a nutritional formula rich in omega-3 and omega-6 fatty acids with antioxidant vitamins including gamma-tocopherol in early Parkinson’s disease: A randomized, double-blind, placebo-controlled trial

In the present study, we investigated whether Neuroaspis PLP10™, a well-designed intervention, rich in omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs) with specific antioxidant vitamins, may exert positive action in the improvement of Parkinson’s disease symptoms and perhaps delay the progression of the disease when used as an adjuvant to the conventional treatment. Forty patients were randomized 1:1 to receive either 20 ml dose, once daily, of control (pure virgin olive oil) or Neuroaspis PLP 10™, a formula containing a mixture of omega-3 (810 mg Eicosapentaenoic acid and 4140 mg Docosahexaenoic acid) and omega-6 fatty acids (1800 mg gamma-Linolenic acid and 3150 mg Linoleic acid) (1:1 w/w), with 0.6 mg vitamin A, vitamin E (22 mg) plus pure gamma (γ)-tocopherol (760 mg), for a total of 30 months in a randomized double-blind, placebo-controlled trial. Participants completed assessments based on the Hoehn and Yahr Staging Scale of Parkinson’s Disease (HY scale) and the Unified Parkinson's Disease Rating Scale (UPDRS) III.Overall, for this small sample size clinical trial, Neuroaspis PLP10™ supplementation as an adjuvant treatment for 30 months in PD patients significantly delayed disease progression according to UPDRS (p ≤ 0.05) Vs placebo.

Synthesis and Characterization of Optically Pure Gamma‐PNA Backbones by SIBX‐Mediated Reductive Amination

Chiral peptide nucleic acid (PNA) is a derivative of regular PNA by introducing a chiral center to its backbone, and is known to bind more strongly to DNA or RNA than regular PNA. In particular, in the case of a γ‐backbone, the L isomer stabilizes the PNA/DNA duplex, and the D‐isomer has the opposite effect. Therefore, the synthesis of an optically pure γ‐backbone is very important. Here, we report a novel synthetic strategy for the suppression of epimerization during the synthesis of the γ‐PNA backbone. A stabilized form of 2‐iodoxybenzoic acid (SIBX) was used as an oxidative reagent in the key intermediate of the N‐Boc‐amino acetaldehyde synthesis. This paper reports (1) the synthesis and comparison of three different γ‐PNA backbones (lysine, alanine, and glutamate) by three different synthetic routes (SIBX, lithium aluminum hydride, and Red‐Al) and (2) the determination of chiral purity from their derivative compounds. The enantiomeric excess purity of SIBX‐mediated γ‐PNA backbones was determined to be more than 99.4%, as ascertained by the high‐performance liquid chromatography (HPLC) chromatogram on a standard RP‐C18 column. It is comparatively higher than that of the other methods examined in this work.

Measuring gamma doses over the mGy-kGy range with a single type of TLD detector

Thermo-luminescent detectors are currently used to measure gamma doses in the medical and environmental surveillance fields. During the past few years, the CEA Reactor Studies Division tested and validated the use of these detectors for gamma flux characterization and nuclear heating measurements in mixed neutron/gamma fields of low power reactors. Doses were comprised between a few mGy and a few Gy for dose rates up to a few Gy.h-1. However, in MTR or TRIGA reactors, the gamma flux level is much higher (> 1012 n/cm2/s) and the TLD currently in use (CaF2:Mn and 7LiF:Mg,Ti) and their readout protocols were no longer suitable for the resulting doses. In order to extend the applicable dose range up to ∼1 MGy (dose rate of a few kGy.h-1), several options were explored. On one side, some adjustments were made to the readout protocols of CaF2:Mn and 7LiF:Mg,Ti, notably by testing the use of filters to reduce the amount of light received by the reader PMT to avoid saturation. On the other side, a new type of TLD (LiF:Mg,Cu,P) with different Li enrichments (natural or enriched in 7Li) was tested. This paper presents the calibration measurements results performed in pure gamma fields, at the irradiation platform of the CEA Cadarache Radioprotection Division, between 250 mGy and 3 Gy for all detector types. In addition to the calibration, these measurements also studied the Mg,Cu,P-doped detectors response: reproducibility, dose rate dependence, incoming photon energy dependence, high temperature effect when reading TLD, etc. Results show that at low doses Mg,Cu,P-doped TLDs are slightly less stable than CaF2:Mn and 7LiF:Mg,Ti. The sensitivity modification after a high dose exposure seems to indicate that a new protocol readout should be defined for Mg,Cu,P-doped sensors (high temperature peak).

Ionizing Radiation Effect upon Er/Yb Co-Doped Fibre Made by In-Situ Nano Solution Doping

In order to assess the possible use in terrestrial and space applications, radiation effects by different ionizing radiation (gamma ray, electron beam, and mixed neutron / γ radiation) upon erbium and ytterbium co-doped fibre (EYDF) made by in-situ nano solution doping have been investigated. The spectral attenuation, unsaturable loss at 830 nm, emission and lifetime of irradiated (max dose is up to 140 kGy) and non-irradiated EYDF samples are measured, and the outcomes were analysed and compared. The results indicate that both the spectral attenuation and unsaturable loss at 830 nm are increased significantly and that the emission is reduced by radiation induced attenuation (RIA) and the decrease of the lifetime. The radiation effects produced by electron beam and gamma ray are almost comparable. The comparison between the radiation effects induced by pure gamma radiation and mix gamma and neutron radiation indicates that the neutron irradiation may have, to some degree, opposite effects as compared with pure γ ray.

Idempotent and Pure Gamma Subacts of Multiplication Gamma Acts

The purpose of this article is to investigate pure gamma subacts of multiplication gamma acts and some related concepts. Some characterizations of pure gamma subacts are given. For this reason, we introduce the concept of idempotent gamma subacts and study some of its properties. Also, we discussed the relation among the pure, multiplication and idempotent gamma acts. Moreover, some result of pure gamma subacts of multiplication gamma acts are considered. Finally, we prove that the product of two pure gamma subacts is also pure.

Production of Gamma Alumina Using Plasma-Treated Aluminum and Water Reaction Byproducts.

High purity hydrogen and solid-state byproducts are produced using a proposed plasma-activated aluminum and water reactions approach. These byproducts could be transformed into pure gamma Al2O3 powder material, while hydrogen can be used for electricity generation. Various chemical methods can be used for the synthesis of gamma alumina, but most could result in high levels of remaining impurities. Boehmite is a cost-effective starting material for the production of high-purity Al2O3. Herein, we present a novel method for the synthesis of boehmite and its transformation into high-specific-surface-area γ-alumina. Specifically, this method implicates the direct reaction between distilled water and plasma-treated aluminum powder. The results show the structural and morphological changes of the byproduct of the aluminum/water reaction to boehmite and γ-Al2O3 after a simple heating procedure (at 280 and 500 °C respectively). The high-purity hydrogen produced during the aluminum/water reaction can be used for the high-efficiency and environmentally friendly production of electrical energy.

Search for neutral-current induced single photon production at the ND280 near detector in T2K

Neutrino neutral-current (NC) induced single photon production is a sub-leading order process for accelerator-based neutrino beam experiments including T2K. It is, however, an important process to understand because it is a background for electron (anti)neutrino appearance oscillation experiments. Here, we performed the first search of this process below 1 GeV using the fine-grained detector at the T2K ND280 off-axis near detector. By reconstructing single photon kinematics from electron–positron pairs, we achieved 95% pure gamma ray sample from protons-on-targets neutrino mode data. We do not find positive evidence of NC induced single photon production in this sample. We set the model-dependent upper limit on the cross-section for this process, at cm2 (90% C.L.) per nucleon, using the J-PARC off-axis neutrino beam with an average energy of GeV. This is the first limit on this process below 1 GeV which is important for current and future oscillation experiments looking for electron neutrino appearance oscillation signals.

Comparison of Biodosimetry Biomarkers for Radiation Dose and Injury Assessment After Mixed-Field (Neutron and Gamma) and Pure Gamma Radiation in the Mouse Total-Body Irradiation Model.

The detonation of a nuclear weapon and the occurrence of a nuclear accident represent possible mass-casualty events with significant exposure to mixed neutron and gamma radiation fields in the first few minutes after the event with the ensuing fallout, extending for miles from the epicenter, that would result primarily in photon (gamma- and/or x-ray) exposure. Circulating biomarkers represent a crucial source of information in a mass-casualty radiation exposure triage scenario. We evaluated multiple blood biodosimetry and organ-specific biomarkers for early-response assessment of radiation exposure using a mouse (B6D2F1, males and females) total-body irradiation model exposed to Co gamma rays over a broad dose range (3-12 Gy) and dose rates of either 0.6 or 1.9 Gy min and compared the results with those obtained after exposure of mice to a mixed field (neutrons and gamma rays) using the Armed Forces Radiobiology Research Institute Co gamma-ray source and TRIGA Mark F nuclear research reactor. The mixed-field studies were performed previously over a broad dose range (1.5-6 Gy), with dose rates of either 0.6 or 1.9 Gy min, and using different proportions of neutrons and gammas: either (67% neutrons + 33% gammas) or (30% neutrons + 70% gammas). Blood was collected 1, 2, 4, and 7 d after total-body irradiation. Results from Co gamma-ray studies demonstrate: (1) significant dose- and time-dependent reductions in circulating mature hematopoietic cells; (2) dose- and time-dependent changes in fms-related tyrosine kinase 3 ligand, interleukins IL-5, IL-10, IL-12, and IL-18, granulocyte colony-stimulating factors, thrombopoietin, erythropoietin, acute-phase proteins (serum amyloid A and lipopolysaccharide binding protein), surface plasma neutrophil (CD45) and lymphocyte (CD27) markers, ratio of CD45 to CD27, procalcitonin but not in intestinal fatty acid binding protein; (3) no significant differences were observed between dose-rate groups in hematological and protein profiles (fms-related tyrosine kinase 3 ligand, IL-5, IL-12, IL-18, erythropoietin, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, CD27, CD45, and ratio of CD45 to CD27) for any radiation dose at any time after exposure (p > 0.148); (4) no significant differences were observed between sex groups in hematological and protein profiles (fms-related tyrosine kinase 3 ligand, IL-18, erythropoietin, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, serum amyloid A, CD45) for any radiation dose at any time after exposure (p > 0.114); and (5) PCT level significantly increased (p < 0.008) in mice irradiated with 12 Gy on day 7 post-total-body irradiation without significant differences between groups irradiated at dose rates of either 0.6 or 1.9 Gy min (p > 0.287). Radiation-quality comparison results demonstrate that: (1) equivalent doses of pure gamma rays and mixed-field radiation do not produce equivalent biological effects, and hematopoietic syndrome occurs at lower doses of mixed-field radiation; (2) ratios of hematological and protein biomarker means in the Co study compared to mixed-field studies using 2× Co doses vs. 1× TRIGA radiation doses (i.e., 3 Gy Co vs. 1.5 Gy TRIGA) ranged from roughly 0.2 to as high as 26.5 but 57% of all ratios fell within 0.7 and 1.3; and (3) in general, biomarker results are in agreement with the relative biological effectiveness = 1.95 (Dn/Dt = 0.67) reported earlier by Armed Forces Radiobiology Research Institute scientists in mouse survival countermeasure studies.

Radiation resistance of elastomeric O-rings in mixed neutron and gamma fields: Testing methodology and experimental results.

Materials and components employed in the presence of intense neutron and gamma fields are expected to absorb high dose levels that may induce deep modifications of their physical and mechanical properties, possibly causing loss of their function. A protocol for irradiating elastomeric materials in reactor mixed neutron and gamma fields and for testing the evolution of their main mechanical and physical properties with absorbed dose has been developed. Four elastomeric compounds used for vacuum O-rings, one fluoroelastomer polymer (FPM) based and three ethylene propylene diene monomer rubber (EPDM) based, presently available on the market have been selected for the test. One EPDM is rated as radiation resistant in gamma fields, while the other elastomers are general purpose products. Particular care has been devoted to dosimetry calculations, since absorbed dose in neutron fields, unlike pure gamma fields, is strongly dependent on the material composition and, in particular, on the hydrogen content. The products have been tested up to about 2 MGy absorbed dose. The FPM based elastomer, in spite of its lower dose absorption in fast neutron fields, features the largest variations of properties, with a dramatic increase in stiffness and brittleness. Out of the three EPDM based compounds, one shows large and rapid changes in the main mechanical properties, whereas the other two feature more stable behaviors. The performance of the EPDM rated as radiation resistant in pure gamma fields does not appear significantly better than that of the standard product. The predictive capability of the accelerated irradiation tests performed as well as the applicable concepts of threshold of radiation damage is discussed in view of the use of the examined products in the selective production of exotic species facility, now under construction at the Legnaro National Laboratories of the Italian Istituto Nazionale di Fisica Nucleare. It results that a careful account of dose rate effects and oxygen penetration in the material, both during test irradiations and in operating conditions, is needed to obtain reliable predictions.

ENHANCED RADIOACTIVE CONTENT OF 'BALANCE' BRACELETS.

During a routine whole body counting measurement of a worker at the Nuclear Research Center Negev, abnormal activities of (232)Th and (238)U were measured. After a thorough investigation, it was found that the radioactivity was due to a rubber bracelet ('balance bracelet') worn by the worker during the measurement. The bracelet was counted directly by an high pure germanium gamma spectrometry system, and the specific activities determined were 10.80 ± 1.37 Bq g(-1) for (232)Th and 5.68 ± 0.88 Bq g(-1) for natural uranium. These values are obviously high compared with normally occurring radioactive material (NORM) average values. The dose rate to the wrist surface was estimated to be ∼3.9 µGy h(-1) and ∼34 mGy for a whole year. The dose rate at the centre of the wrist was estimated to be ∼2.4 µGy h(-1) and ∼21 mGy for a whole year. The present findings stresses a more general issue, as synthetic rubber and silicone products are common and widely used, but their radioactivity content is mostly uncontrolled, thus causing unjustified exposure due to enhanced NORM radioactivity levels.

Oxidative dehydrogenation of ethanol over AgLi–Al2O3 catalysts containing different phases of alumina

Oxidative dehydrogenation of ethanol over the AgLi–Al2O3 catalysts having different phase compositions of alumina was investigated. The pure gamma (CHI00), pure chi (CHI100) and equally mixed phases (CHI50) derived from the solvothermal synthesis can play important roles on the physicochemical properties of AgLi–Al2O3 catalysts. Especially, the amount of weak basic sites, the oxidation state of Ag, and the reduction behaviors of catalysts are crucial in determining the ethanol conversion and product selectivity. It was found that increased amounts of weak basic sites and Agnδ+ clusters enhanced the catalytic activity as seen for the AgLi–CHI50 catalyst.

Study of the thermal neutron detector ZnS(Ag)/LiF response using digital pulse processing

The neutron and gamma responses of a commercial 6Li loaded ZnS(Ag) detector (EJ-420) have been studied using a moderated 252Cf source and a set of pure gamma ray sources (137Cs and 241Am). Digital pulse processing was used to implement the pulse shape discrimination technique in order to well-separate neutrons from gamma-induced events. It was found that in case of a mixed neutron/gamma radiation field (252Cf) pulse-height discrimination technique works quite good for the measurement of the neutron field, but if one desires to reach a gamma-to-neutron sensitivity ratio lower than 0.7% pulse shape discrimination technique must be implemented. The decay time of the scintillation components of ZnS(Ag)/6LiF were determined by following the so called ``peeling off method''. The results were compared with some reported values. In order to better understand the shape of the neutron-induced pulses produced by the EJ-420 detector, a measurement with an EJ-440 detector of an alpha source (210Po) was performed. The response of both detectors must be very similar because these are based in ZnS(Ag) scintillator. It seems that for neutron detection with the EJ-420, the slow component of the scintillation yield produced by the tritium is higher than the one produced by the alpha particle. Finally, the neutron efficiency and some experimental features of the EJ-420 detector were determined and reproduced respectively by Monte Carlo simulations (GEANT4 9.6).

Efficient Radioisotope Energy Transfer by Gold Nanoclusters for Molecular Imaging.

Beta-emitting isotopes Fluorine-18 and Yttrium-90 are tested for their potential to stimulate gold nanoclusters conjugated with blood serum proteins (AuNCs). AuNCs excited by either medical radioisotope are found to be highly effective ionizing radiation energy transfer mediators, suitable for in vivo optical imaging. AuNCs synthesized with protein templates convert beta-decaying radioisotope energy into tissue-penetrating optical signals between 620 and 800 nm. Optical signals are not detected from AuNCs incubated with Technetium-99m, a pure gamma emitter that is used as a control. Optical emission from AuNCs is not proportional to Cerenkov radiation, indicating that the energy transfer between the radionuclide and AuNC is only partially mediated by Cerenkov photons. A direct Coulombic interaction is proposed as a novel and significant mechanism of energy transfer between decaying radionuclides and AuNCs.

Contemporary application of classical techniques in thyroid scanning

The thyroid consists of two lobes that are connected by an isthmus. It is located anterior to the trachea between the cricoid cartilage and the suprasternal notch. It produces two related hormones, thyroxine (T4) and triiodothyronine (T3). Benign nodules and thyroid cancer are relatively common and amenable to detection by physical examination. Nuclear medicine is a part of medicine that uses radioisotopes for the diagnosis and treatment of diseases. Technetium-99m-pertechnate is widely used for imaging the thyroid gland. 99mTc is trapped by thyroid, but unlike iodine, it does not undergo organification and remains in the gland for a relatively short period. Imaging is done 30 min after administration of radiotracer. 123Iodine has a short physical half-life of 13 h. Both tracers are pure gamma emitters. 131Iodine is worse for imaging (except metastases in thyroid differentiated cancer) because it gives a high absorbed radiation dose related to the long physical half-life of 8 days and beta emissions. It is ideal for the treatment of thyroid disease, and used in the management of differentiated thyroid cancer, Graves’ disease, and toxic nodular goitre. Indications for thyroid scintigraphy and RAI uptake are: differential diagnosis of thyrotoxicosis, before treatment with radioiodine 131I, measuring of goitre volume, ectopic goitre, congenital hypothyroidism. Other indications are metastases of well-differentiated thyroid cancer (eg. papillary or follicular cancer). Very rarely, ovarian goitre is present. The normal image of thyroid scan shows the typical butterfly shape (a shield shape according to the ancient Greeks), the position in the anterior neck area, the regular contour, without any interruption or mismatches. The distribution of the radiotracer is homogenous with intense, usually warm color in the middle of each lobe related to it thickness. The margins have a less intense color because of the decreased quantity of thyroid tissue. Physiologically the right lobe is often larger than the left one. There is imaging on the scan of the salivary glands. Nuclear imaging of Graves’ disease is characterized by an enlarged gland and increased tracer uptake (usually more than 55%) that is distributed homogenously. Toxic multinodular goitre shows irregular distribution of tracer and a normal or slightly elevated 131I uptake. The irregular tracer distribution is consistent with heterogeneity in cell function and growth, and the presence of micro- and macronodules. Large and discrete hyperfunctioning nodules may be associated with poor uptake in the extranodular thyroid tissue. The latter consists of suppressed normal tissue with less tracer accumulation. After 131I treatment, the areas that were cold may appear warm. Although the use of fine needle aspiration biopsy (FNAB) has diminished the use of thyroid scans in the evaluation of solid thyroid nodules, the functional features of thyroid nodules have some prognostic significance. So-called cold nodules, which have diminished or no tracer uptake, are usually benign. However, these nodules are more likely to be malignant (5-10%) than hot nodules, which are almost always benign. Subacute thyroiditis is associated with very low uptake because of follicular cell damage and TSH suppression. Drug-induced thyrotoxicosis or factitious thyrotoxicosis are also associated with low uptake. Thyroid scanning is used in the follow-up of thyroid cancer. After thyroidectomy and ablation using 131I, there is diminished tracer uptake in the thyroid bed, allowing the detection of metastatic thyroid cancer remnants that retain the ability to transport radioiodine. Whole body scans using 2-5 mCi (74-185 MBq) 131I are performed after thyroid hormone withdrawal to rise the TSH concentration or after the administration of rhTSH. Radioiodine 131I may be also used for treatment benign or malignant thyroid disorders.

Depth Profile of 137Cs Fallout in Soil in Cameron Highlands

137Cs is one of the important man-made radionuclide introduced into the environment through nuclear weapons testing and nuclear accidents. In Cameron Highlands meaningful activity concentration of 137Cs radionuclide has been measured. The present study embarked on the determination of 137Cs activity concentration in soils of the sloping area. This would enable the distribution profile in the soil be investigated. Soil profile samples were collected by using scrapper plate in the sloping area which covers top, centre and bottom of the hills and a core in the forest for comparison purpose. The scrapper is 40 cm long and able to obtain slice of 2 cm interval of soil with diameter of 15.2 cm. Soil samples were oven dried, ground, sieved, homogenize and seal properly into a plastic container. The 137Cs activity concentration was measured by using low background coaxial hyper pure germanium detector gamma spectrometer based on 137Cs 661.66 KeV gamma ray. Results showed there were trend of low activity on the top of the hill and subsequently increases downhill. In all location, two trends of profiles were observed starting from the depth of 0 cm to 18 cm and 18 cm to 30 cm which indicating the presence of two sources of 137Cs. The 137Cs activity concentrations range detected at top location was from 0.05 Bq/kg to 1.53 Bq/kg, centre was 0.22 Bq/kg to 2.11 Bq/kg, bottom was from 0.00 Bq/kg to 2.03 Bg/kg and forest was 0.00 Bq/kg to 0.96 Bq/kg. The basic parameters of the soil such as pH (top; 3.72, centre; 4.26, bottom; 4.02), density (top; 1.45 g/m3, centre; 1.41 g/m3 , bottom; 1.59 g/m3 ) and organic matter content (top; 17.08 %, centre; 16.75 %, bottom; 20.32 %) also being tested. These results show that the relative activity concentration of 137Cs at the top is lowest, while at the bottom is highest, representing the presence of downward transport. However, identical pattern of profiles were observed at the three points of the slopes.

Analysis of dark current images of a CMOS camera during gamma irradiation

We report on the behaviour of the dark current images of the Event Detection Intelligent Camera (EDICAM) when placed into an irradiation field of gamma rays. EDICAM is an intelligent fast framing CMOS camera operating in the visible spectral range, which is designed for the video diagnostic system of the Wendelstein 7-X (W7-X) stellarator. Monte Carlo calculations were carried out in order to estimate the expected gamma spectrum and dose for an entire year of operation in W7-X. EDICAM was irradiated in a pure gamma field in the Training Reactor of BME with a dose of approximately 23.5Gy in 1.16h. During the irradiation, numerous frame series were taken with the camera with exposure times 20μs, 50μs, 100μs, 1ms, 10ms, 100ms. EDICAM withstood the irradiation, but suffered some dynamic range degradation. The behaviour of the dark current images during irradiation is described in detail. We found that the average brightness of dark current images depends on the total ionising dose that the camera is exposed to and the dose rate as well as on the applied exposure times.

Analysis of the pulse shape mechanism in a plastic scintillator with efficient neutron/gamma pulse shape discrimination

A sample of the new plastic scintillator recently formulated by Zaitseva et al., and shown by them to have efficient pulse shape discrimination properties, was exposed to pure gamma and mixed neutron/gamma radiation from different sources, and the pulse shapes recorded by a digitising oscilloscope. Separate average neutron and gamma pulse shapes were derived, using pulse shape discrimination where necessary.A theoretical pulse shape formula, based on the conventional two-lifetime description of pulse shape formation in organic scintillators, was then fitted to these measured shapes to obtain numerical values for the lifetimes and proportions of the scintillator excitations. It is found that, although the conventional model explains much of the observed pattern of values, there are hints of behaviour that is not consistent with its assumptions.