Haut PDF Gamma-heating and gamma flux measurements in the JSI TRIGA reactor, results and prospects

Gamma-heating and gamma flux measurements in the JSI TRIGA reactor, results and prospects

Gamma-heating and gamma flux measurements in the JSI TRIGA reactor, results and prospects

IV. C ONCLUSION AND OUTLOOKS This study aimed at comparing measurements and calculations of dose rates in different irradiation positions of the JSI TRIGA reactor. Given the low number of measurements in each position, the preliminary analysis shows a qualitatively good agreement. This work should be continued by taking into account different correction factors for the measurement analysis, and by an additional effort in the experiment modeling. The TLD700 results are not presented since their readout protocol was not suited for such high integrated dose levels. Further study on the TLD700 readout protocol are to be performed, based on work on reading procedures for high dose measurement with LiF:Mg,Cu,P detectors [10]-[12].
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Gamma-Heating and Gamma Flux Measurements in the JSI TRIGA Reactor: Results and Prospects

Gamma-Heating and Gamma Flux Measurements in the JSI TRIGA Reactor: Results and Prospects

total signal. However, the difference is of 1.5%, comparable to the measurement uncertainty, making it difficult to analyze. Dose rate calculations, including the electron and gamma sources due to decay of radioactive products were calculated using the JSIR2S code package [35]. The reactor power was simulated in 109 steps, following the measured reactor power to a logarithmically interpolated precision of 1% at 4 kW and 15% at 10 W. The measured and modeled reactor power, as well as FC and IC signals in their respective positions as measured during and after 4 kW reactor power excursion, are displayed in Fig. 11. The absorbed dose calculations were performed in 10 steps during each TLD irradiation (Fig. 12). The transport part was performed using the ENDF/B-VII.1 nuclear data library [36], while the isotopic inventory calculations were performed using the JEFF 3.3 nuclear data library [37]. The comparison between calculated and measured doses during experiments is presented in Tab. V. The last experimental measurement (from 32 minutes after the SCRAM during 137 minutes) was not calculated. Uncertainties on the calculated values are between 3 to 4.5 % for each step. The experimental values and the calculated ones are in very good agreement. The dose rate calculations after shut down show a very good
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Improvements in neutron and gamma measurements for material testing reactors

Improvements in neutron and gamma measurements for material testing reactors

Tests performed from 2012 to 2015 at the French OSIRIS reactor and at the Polish MARIA reactor proved the consistency of the MIC signal with other evaluations of gamma flux. Furthermore, tests performed in 2014 at the Slovenian TRIGA Mark II reactor confirmed the relevance of MIC sensor for online and real-time evaluation of gamma flux over a wide range of flux level. MIC has proven to be particularly appropriate to monitor real-time the reactor power, but also to follow reactor SCRAMs (reactor shutdown with rapid insertion of control rods).
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Measurements of miniature ionization chamber currents in the JSI TRIGA Mark II reactor demonstrate the importance of the delayed contribution to the photon field in nuclear reactors

Measurements of miniature ionization chamber currents in the JSI TRIGA Mark II reactor demonstrate the importance of the delayed contribution to the photon field in nuclear reactors

Joˇ zef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana, Slovenia Abstract The characterization of experimental locations of a research nuclear reactor implies the determination of neutron and photon flux levels within, with the best achievable accuracy. This study focuses on the photon flux problematic. In nuclear reactors, photon fluxes are commonly calculated by Monte Carlo simulations but rarely measured on-line. In this context, experiments were conducted with a miniature gas ionization chamber (MIC) based on miniature fission chamber mechanical parts, recently developed by the CEA (French Atomic Energy and Alternative Energies Commission) irradiated in the core of the Joˇzef Stefan Institute TRIGA Mark II reactor in Ljubljana, Slovenia. The aim of the study was to compare the measured MIC currents with calculated currents based on simulations with the MCNP6 code. A discrepancy of around 50% was observed between the measured and the calculated currents; in the latter taking into consideration only the prompt photon field. Further experimental measurements of MIC currents following reactor SCRAMs (reactor shutdown with rapid insertions of control rods) provides evidence that over 30% of the total measured signal is due to the delayed photon field, originating from fission and activation products, which are untreated in the calculations. In the comparison between the measured and calculated values, these findings imply an overall discrepancy of less than 20% of the total signal which is still unexplained.
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Simultaneous Measurements of Nuclear Heating and Thermal Neutron Flux Obtained with the CALMOS-2 Measurement Device inside the OSIRIS Reactor

Simultaneous Measurements of Nuclear Heating and Thermal Neutron Flux Obtained with the CALMOS-2 Measurement Device inside the OSIRIS Reactor

USE OF THE ZERO METHOD IN UPPER PART OF THE CORE The zero method can be considered as an absolute heating measurement and has to confirm, at least for low heating levels, results obtained with preliminary calibration. To study the linearity loss, an intensive use of this procedure was made during the measurement campaign (Fig. 4a). However, it could only be performed in upper part where heating levels remain under around 4 W.g -1 , due to the maximum intensity current (2 A) applicable to heater wires. Fig. 4b gathers 21 heating measurements obtained both by calibration and zero methods on the 0 - 4 W.g -1 range. All measurements are obtained by the new 4-wires technique, measuring together voltage (U) and current (I) applied to the reference heater. Fig. 4b shows that all results are within 2% discrepancy up to around 2.5 W.g -1 . Accounting for uncertainties, we can consider that both methods are very close to each other up to that point. Beyond that level, the zero method provides values slightly higher than those obtained by calibration. That leads to apply to the calibration a Kc factor close to 1.04 at 3.5 W.g -1 and 1.05 at 4 W.g -1 .
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First In-Core Simultaneous Measurements of Nuclear Heating and Thermal Neutron Flux obtained with the Innovative Mobile Calorimeter CALMOS inside the OSIRIS Reactor

First In-Core Simultaneous Measurements of Nuclear Heating and Thermal Neutron Flux obtained with the Innovative Mobile Calorimeter CALMOS inside the OSIRIS Reactor

IV. I N - CORE MEASUREMENTS AT NOMINAL POWER Generalities We remind that OSIRIS is a pool type light water reactor with an open core. The core is a compact unit, with an horizontal section of 60 cm × 70 cm and a height of 70 cm. The core housing contains a rack of 56 cells. This rack is loaded with 38 standard fuel elements, 6 control elements and up to 7 beryllium elements. At least two experimental locations (22 and 26) are used for radioisotopes production for medical application (MOLY devices). Remaining locations (24, 44 and 64) are dedicated to welcome experiments, and equipped with water boxes (82mm x 82mm) which can contain up to 4 experiment rigs (37mm in diameter)(Fig. 3). Purpose of the CALMOS device is to make measurements in 24, 44 and 64 locations. Note that the heating level is higher and higher when we go up to the north, i.e 24 then 44 then 64. Until the end of 2012, safety considerations limited first campaigns [5] not to go beyond 6W.g -1 . Therefore all measurements carried out in central locations (44, 64) which offer higher heating rates, were made with a reactor power limited to 40MW. Then, results were extrapolated to the nominal power.
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MONACO v2: Multipurpose and Integrated Data Acquisition System for On-line Neutron and Gamma Measurements

MONACO v2: Multipurpose and Integrated Data Acquisition System for On-line Neutron and Gamma Measurements

ONSIDERING local neutron flux measurement techniques in nuclear research reactors environments in addition with reactor command control, online gaseous detectors are suffering from the lack of up-to-date and integrated signal acquisition system on the nuclear instrumentation market. CEA needs for research reactor neutron field characterization led to the development of a multipurpose and integrated data acquisition system for online neutron and gamma measurements called MONACO, standing for ‘Multichannel Online Neutron Acquisition in Campbell mOde’. After two years of development, this paper presents the recent second version [1][2] features and the validation of two MONACO v2 prototypes in the Slovenian TRIGA Mark II reactor.
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Last Improvements of the CALMOS Calorimeter Dedicated to Thermal Neutron Flux and Nuclear Heating Measurements inside the OSIRIS Reactor

Last Improvements of the CALMOS Calorimeter Dedicated to Thermal Neutron Flux and Nuclear Heating Measurements inside the OSIRIS Reactor

VII. U SE OF THE Z ERO M ETHOD IN U PPER P ART OF THE C ORE The zero method can be considered as an absolute heating measurement and has to confirm, at least for low heating levels, results obtained with preliminary calibration. To study the linearity loss, an intensive use of this procedure was made during the measurement campaign (Fig. 7). However, it could only be performed in upper part where heating levels remain under around 4 W.g -1 , due to the maximum intensity current (2 A) applicable to heater wires. Fig. 8 gathers 21 heating measurements obtained both by calibration and zero methods on the 0 - 4 W.g -1 range. All measurements are obtained by the new 4-wires technique, measuring together voltage (U) and current (I) applied to the reference heater. Fig. 8 shows that all results are within 2% discrepancy up to around 2.5 W.g -1 . Accounting for uncertainties, we can consider that both methods are very close to each other up to that point. Beyond that level, the zero method provides values slightly higher than those obtained by calibration. That leads to apply to the calibration a Kc factor close to 1.04 at 3.5 W.g -1 and 1.05 at 4 W.g -1 .
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Evaluation of the Effect of Burn-up on Neutron Flux and Reaction Rate Distributions in the TRIGA Mark II Reactor

Evaluation of the Effect of Burn-up on Neutron Flux and Reaction Rate Distributions in the TRIGA Mark II Reactor

Although this topic has already been tackled using similar approaches to calculating the fuel burnup [4–6], the research in the paper represents a step forward regarding the detailed Monte Carlo analysis of crucial reactor parameters and most importantly validating the results of the burnup calculations against in-core fission chamber measurements. In the paper the method for assessing the burnup and computing the consequent isotopic composition of individual fuel elements will be presented. The latter will be used to construct several Monte Carlo models of the reactor, each distributing different radial and axial distributions of fuel burnup. Its effect on the multiplication factor of the reactor model, neutron spectra, neutron flux and reaction rate distributions will be shown and concluded with a measurement to calculation comparison. 2. Burnup Assessment
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Delayed Gamma Measurements in Different Nuclear Research Reactors Bringing Out the Importance of Their Contribution in Gamma Flux Calculations

Delayed Gamma Measurements in Different Nuclear Research Reactors Bringing Out the Importance of Their Contribution in Gamma Flux Calculations

F. Malouch is with the Alternative Energies and Atomic Energy Commission: CEA, DEN, DM2S, Saclay, 91191, Gif-sur-Yvette, France. I. I NTRODUCTION Neutron and gamma flux levels are key parameters in nuclear research reactors. In Material Testing Reactors, such as the future Jules Horowitz Reactor, under construction at the French Alternative Energies and Atomic Energy Commission (CEA Cadarache, France), the expected gamma flux levels are very high (nuclear heating is of the order of 20 W/g at 100 MWth). As gamma rays deposit their energy in the reactor structures and structural materials it is important to take them into account when designing devices for experimental channels.
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Tests and foreseen developments of fibered-OSLD gamma heating measurements in low-power reactors

Tests and foreseen developments of fibered-OSLD gamma heating measurements in low-power reactors

 Abstract— In this paper are presented test measurements of a fibered-OSLD system performed during a dedicated experimental phase in EOLE zero-power reactor. The measurement setup consists of an OSLD crystal connected onto the extremity of an optical fiber and a laser stimulation system, manufactured by the CEA/LIST in Saclay. The OSL sensor is remotely stimulated via an optical fiber using a diode-pumped solid-state laser. The OSL light is collected and guided back along the same fiber to a photomultiplier tube. Results obtained using this system are compared to usual gamma heating measurement protocol using OSLD pellets. The presence of induced radio-luminescence in the OSLD during the irradiation was also observed and could be used to monitor the gamma flux.
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Evaluation of biases and experimental uncertainties of the fission rate profile measurements at the JSI TRIGA Mark II research reactor

Evaluation of biases and experimental uncertainties of the fission rate profile measurements at the JSI TRIGA Mark II research reactor

fission rate measurements as well as a detailed description of the influence of fuel material data error and fuel burn-up on the experimental and computational uncertainty. It is shown that the insertion of fission chambers and guide tubes into the core of the TRIGA reactor significantly influences the neutron spectrum in the measuring positions and thus the fission rate measurements themselves – the difference between reaction rates in experimental setups without aluminium instrumentation and with it can amount up to 13 % due to the fact that they cause water dislocation and thus decrease neutron thermalization. The contribution of the fuel material data uncertainty to the total experimental uncertainty of the reaction rate measurements was also analysed using a computational approach where perturbations of the fuel density were performed. The effect of the fuel density variations on the axial fission rate profiles is presented in the paper. Since the support Monte Carlo calculations were performed using a reactor model with fresh fuel, additional computations to investigate the effect of core burn-up on the fission rates were made. In the study the average burnup of individual fuel elements, ranging from 0.6 MWd to 4.9 MWd, was calculated with which the axially dependent isotopic composition of the burnt fuel meat was assessed. In the paper a comparison of fission rate profiles using fresh and burnt fuel is presented where it can be seen that the differences are greatest at the centre of the active part of the fuel, where burnup is highest – it is shown that a 10 % deficit of 235 U mass results in an approximately 10 % decrease of fission reaction rate.
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Benchmark experiments at the TRIGA Mark II reactor

Benchmark experiments at the TRIGA Mark II reactor

After some years of operation the criticality benchmark was repeated with burned fuel [8]. This benchmark provides useful information for testing of cross sections of burnup calculation codes as well as the reactivity effect of burnup. In addition the fuel burnup of individual fuel elements was measured by reactivity experiments [9][10]. Recently we initiated activities to thoroughly record the operational history of the reactor together with excess reactivity and control rod worth measurements, which could be used for testing of core management codes such as TRIGLAV [11] or Monte Carlo codes such as SERPENT [12]. It is important to note that one of the major uncertainties in fuel burnup determination is the uncertainty in the measured reactor power level [13]. The major source of uncer- tainty in the JSI TRIGA Mark II reactor is the neutron flux redistribution or tilt in radial direction due to asymmetric control rod insertion. As the reactor power is measured with one detector only, the change in measured power level can be as much as 20-30 %. This can be corrected by applying cor- responding correction factors [14] or measuring the reactor power using multiple detectors [15]. The above approaches were verified experimentally and calculationally and are described in section 2.2.
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Searches for Higgs boson pair production in the $hh\to bb\tau\tau, \gamma\gamma WW*, \gamma\gamma bb, bbbb$ channels with the ATLAS detector

Searches for Higgs boson pair production in the $hh\to bb\tau\tau, \gamma\gamma WW*, \gamma\gamma bb, bbbb$ channels with the ATLAS detector

difference between γγ+jets and γγ`ν+jets samples is studied using simulation. A difference below 1% is observed. Taking all these di fferences as systematic uncertainties, the fraction of background events in the signal mass window is f SB = 0.135 ± 0.004. With 9 (N SB Data ) events observed in the data sidebands, it leads to N SR est = 1.40 ± 0.47 events from the continuum background. Figure 4 (a) also shows the contribution expected from single SM Higgs boson production. The data prefer a larger cross section than the SM prediction for single Higgs boson production, consistent with the measurement reported in Ref. [ 66 ]. The uncertainties on the signal acceptances are estimated following the same procedure as the hh → bbττ analysis. The total experimental uncertainty is found to vary between 4% and 7% for di fferent signal samples under consideration, dominated by the contribution from the jet energy scale. The theoretical uncertainties from PDFs, the renormalization and factorization scales, and the strong coupling constant are 3%, 1%, and 3%, respectively, the same as for the hh → bbττ analysis.
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Ni-based superalloy: crystalline orientation mapping and gamma - gamma’ phases discrimination with the iCHORD method

Ni-based superalloy: crystalline orientation mapping and gamma - gamma’ phases discrimination with the iCHORD method

All the images are then stacked together and the residual drift is corrected. At the end, intensity profiles can be extracted by plotting the intensity of each pixel along the stack, at a given (X,Y) position in all the images. The secondary electron detector used for the acquisition of images series can also be used to detect secondary ions, by changing its polarity. The resulting images present a strong contrast between γ and γ ’ phases, with also a bit of channeling contrast. To remove the channeling information, several images are acquired at different orientation (during the rotation series) and an average image is calculated. A threshold operation can then be applied to this average image, with no more channeling contrast.
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en
                                                                    fr

en fr Perisomatic inhibition in gamma oscillations and auditory learning Inhibition périsomatique dans les oscillations gamma et dans l'apprentissage auditif

7.2.8 Fixation and staining Standard tissue fixation and staining techniques were employed for preparing the brain of mice for microscopic examination. Mice were deeply anaesthetized by brief exposure to isoflurane followed by intraperitoneal injection of urethane (as 10% m/v urethane in ACSF; 0.2 mL per body 10 g of weight). Prior to initiating the surgery, pain reflexes were confirmed to have been abolished by the anaesthesia. After performing an incision in the abdomen and thorax, the heart was exposed and a needle, connected to a peristaltic pump (2115 multiperpex, LKB), was inserted in the left heart. Next, the animal underwent transcardial perfusion with 2 solutions (8-mL/min volumetric flow rate): first, the blood was drained from the circulatory system with PBS (for 1 min) through large cuts made in the liver; second, the whole body was perfused (for 13 min) with fixative (4% depolymerized PFA). Subsequently, the animal was decapitated, the skull was opened and the brain resected and stored in fixative overnight. Afterwards, the brain was transferred to PBS and coronal slices (50-µm thick) were taken from the MGB and ACx with a vibratome (DTK-1000, D.S.K.). On the same day, slices were treated with various PBS-based solutions according to the following protocol: (a) slices were permeabilized in 0.4% TritonX-100 (for 30 min, at room temperature [RT]), (b) then blocked in 0.2% TritonX-100 and 4% normal goat serum (NGS, for 30 min, at RT) and (c) incubated in 0.1% TritonX-100 and 2% NGS together with the primary antibodies (overnight, at 4°C). On the next day, slices were again treated with several PBS-based solutions according to the following protocol: (a) slices were washed in 1% NGS (3 times for 10 min each), (b) then incubated in 1.5% NGS together with the secondary antibodies (for 2–2.5 h, at RT), (c) washed yet again with 1% NGS (2 times for 10 min each), (d) incubated with DAPI (for 5 min), (e) washed in PBS alone (2 times, for 10 min each) and, finally, (f) mounted in Mowiol solution (composition in Table 7.6). All antibodies and DAPI were applied using a dilution of 1:1000.
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Characterization of the unfolding, refolding, and aggregation pathways of two protein implicated in cataractogenesis : human gamma D and human gamma S crystallin

Characterization of the unfolding, refolding, and aggregation pathways of two protein implicated in cataractogenesis : human gamma D and human gamma S crystallin

2 3 4 5 6 7 8 9 10 11 12 Figure 6-2 Time dependent recruitment of wild-type and N143D HyS-Crys to the HyD-Crys aggregate. Refolding of denatured HyS-Crys was initiated and an equal concentration of denatured HyD-Crys was added after 0, 2, 10, 30, 60, or 120 minutes. The protein samples were allowed to refold together overnight and then the solutions were centrifuged at 40,000 RPM. The resolubilized pellet was resolved on a 14% polyacrylamide gel. Lanes 1 through 6 show the time dependent refolding and aggregation of wild-type HyS-Crys and HyD-Crys, while lanes 7 to 12 show N143D HyS-Crys and HyD-Crys. The time of addition of denatured HyD-Crys after HyS-Crys refolding was begun is indicated at the top of the lanes.
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Pertes de coïncidence gamma-gamma dans des sources épaisses

Pertes de coïncidence gamma-gamma dans des sources épaisses

1. Contexte Cette étude est motivée par un projet de mesures de section efficaces ayant pour but la détermination expérimentale des taux de production de noyaux exotiques riches en neutrons attendus dans les cibles d'UCx de Spiral2. Les cibles sont constituées de barillets cylindriques, eux mêmes composés de disques. Une estimation expérimentale du taux de production dans la cible peut donc être faite en sélectionnant un certain nombre de disques selon leur position dans la cible et en mesurant le nombre de noyaux présents. La cible est décrite dans [1]. Des calculs de taux de production ont ensuite été faits par M. Fadil [2]. La motivation de la mesure est qu'une simulation de l'expérience à IGISOL pour une cible mince (90 mg/cm2) [3] a donné des résultats trop optimistes qui suggèrent que les bibliothèques de section efficaces ne sont pas fiables aux énergies neutroniques à considérer pour Spiral2. Il est d'abord envisagé d'irradier une feuille d'uranium assez mince (quelques g/cm 2 ) par des neutrons pour obtenir des sections efficaces. Une proposition d'expérience a été acceptée par le PAC de Jyväskylä où un faisceau de neutrons obtenu par l'envoi de deutons de 40 MeV sur un convertisseur de carbone, analogue à celui de Spiral2, est disponible et est bien connu [4]. Ce faisceau est présenté sur la figure 1. La mesure comportera une série de cycles avec une irradiation par les neutrons, un transport de la cible puis la détection les radiations gamma émises par les noyaux se trouvant dans les cibles.
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Absolute cross-sections from X - $\gamma$ coincidence measurements

Absolute cross-sections from X - $\gamma$ coincidence measurements

sity (∼ 10 5 pps) radioactive ion beams provides the opportunity to study the effect of exotic structures on the reaction mechanism. Both these studies re- quire making sensitive measurements and employ- ing techniques which are able to extract a weak sig- nal in the presence of a relatively large background. The fusion cross section is extracted from direct or indirect measurements of evaporation residues. The direct detection of evaporation residues can be per- formed using a recoil mass separator [1]. In the case of light and low incident energy beams, the small re- coil energies and large charge of the residue make these measurements difficult. Measurements of in-
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Search for Higgs and $Z$ Boson Decays to $J/\psi\gamma$ and $\Upsilon(nS)\gamma$ with the ATLAS Detector

Search for Higgs and $Z$ Boson Decays to $J/\psi\gamma$ and $\Upsilon(nS)\gamma$ with the ATLAS Detector

Observed 33 29 41 28 44 In conclusion, the first search for the decays of the SM Higgs and Z bosons to J/ψ γ and Υ(nS) γ (n = 1, 2, 3) has been performed with √ s = 8 TeV pp collision data samples corresponding to integrated luminosities of up to 20.3 fb −1 collected with the ATLAS detector at the LHC. No significant excess of events is observed above the back- ground. In the J/ψ γ final state the 95% CL upper limits on the relevant branching fractions for the SM Higgs and Z bosons are 1.5 × 10 −3 and 2.6 × 10 −6 , respectively. The corresponding upper limits in the Υ(1S, 2S, 3S) γ chan- nels are (1.3, 1.9, 1.3) × 10 −3 and (3.4, 6.5, 5.4) × 10 −6 , for the SM Higgs and Z bosons respectively. These are the first experimental bounds on exclusive Higgs and Z bo- son decays to final states involving quarkonia.
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