3-D thermal and radiation-matter interaction simulations of a SiC solid-state detector for neutron flux measurements in JSI TRIGA Mark II research reactor

Neutron detection is a relevant topic in the field of nuclear instrumentation. It is at the heart of the concerns for fusion applications (neutron diagnostics, measurements inside the Test Blanket Modules TBM) as well as for fission applications (in-core and ex-core monitoring, neutron mapping or safety applications in research reactors). Moreover, due to the even more harsh conditions of the future experimental reactors such as the Jules Horowitz Reactor (JHR) or International Thermonuclear Experimental Reactor (ITER), neutron detectors need to be adapted to high neutron and γ fluxes, high nuclear heating rates and high temperatures. Consequently, radiation and temperature hardened sensors with fast response, high energy resolution and stability in a mixed neutron and γ environment are required. All these requirements make wide-bandgap semiconductors and, more precisely, Silicon Carbide (SiC) serious candidates due to their intrinsic characteristics in such extreme environments. Thus, since the last decades, SiC-based detectors are developed and studied for neutron detection in various nuclear facilities. In this paper, a SiC-based neutron detector is 3-D designed and studied through thermal and radiation-matter interaction numerical simulations for a future irradiation campaign at the Jožef Stefan Institute TRIGA Mark II research reactor in Slovenia. Firstly, this paper presents the scientific background and issues of our SiC-based detectors. In a second part the 3-D geometry is shown. Thereafter, the 3-D numerical thermal simulation results are reported. Finally, the 3-D numerical radiation/matter interaction simulations results are presented.

Study review of the CALORRE differential calorimeter: definition of designs for different nuclear environments

This paper deals with the CALORRE differential calorimeter patented by Aix-Marseille University and the CEA in 2015. Firstly, the paper focuses on the presentation of the first prototype of CALORRE calorimeter qualified under real conditions during the MARIA irradiation campaign in 2015. Then, a review of the studies restricted to one CALORRE calorimetric cell realized thanks to experimental characterizations under laboratory conditions is detailed. Several configurations were studied to determine the influence of the cell height, its horizontal fin geometry and the nature of the material of its structure on its response for a calibration protocol: linearity, sensitivity, range, reproducibility, response time and absolute temperatures. Finally, within the framework of the new CALORI project, an optimization of the calorimeter assembly and its design were carried out in order to remove contact thermal resistances and provide a new configuration of CALORRE calorimeter suited for the in-core water loop of the MIT reactor (2 W.g-1). The response of this new calorimeter is estimated thanks to thermal simulations.

Characterization of calorimeter responses under laboratory conditions thanks to an optimized transient thermal test bench

This paper presents an experimental study of the calibration of a non-adiabatic single-cell calorimeter called KAROLINA. This type of sensor is used to quantify the nuclear heating rate inside MTRs (Material Testing Reactors). The calibration of this sensor type is carried out in laboratory conditions without irradiation. The calibration corresponds to a preliminary step, which is crucial to use this sensor in real conditions. In the case of the studied single-cell calorimeter owning no heating element, the calibration is realized with a specific test bench, called BERTAN, based on thermal transient regimes. First of all, the paper describes the methodology of the determination of the calorimeter sensitivity and the dedicated experimental set-up developed recently. Then the paper is devoted to a parametric study carried out on the KAROLINA single-cell calorimeter to determine the influence of several parameters on its thermal time constant (temperature, velocity, phase, method).

Calibration of a Single-Cell Calorimeter in a New Transient-state Test Bench

The nuclear radiation energy deposition rate is a key value for the thermal design of experiments, on materials and nuclear fuels, carried out in experimental channels of nuclear research reactors. Studies are led for two kinds of sensor currently dedicated to quantifying this value and corresponding to calorimeter. Development of new sensors but also improvement of their calibration and their associated interpretation methods are necessary. These aims are possible by many ways such as numerical simulations of sensor, characterizations under laboratory conditions and experimental campaign under irradiation conditions. The calibration step under non-irradiation conditions represents a crucial phase. This phase requires the development of specific benches. The present paper focuses on a new thermal-transient bench and its use to perform calibration of a polish single-cell calorimeter. The new bench is detailed. First studies of the influence of external conditions (temperature, velocity) on the calorimeter sensitivity are presented and discussed.

Comparison of the Responses of New Reduced-Size Calorimetric Cells Made of Different Structure Materials for High Energy Deposition

This paper concerns experimental and numerical works on a new differential calorimeter called CALORRE and validated recently under irradiation conditions in MARIA reactor at low nuclear absorbed dose rate level. Works focus on a specific configuration of CALORRE which was designed especially for the measurement of high nuclear energy deposition rates inside Material Testing Reactors. Due to the high level, a new calibration system was fabricated in order to determine the response of the new configuration under laboratory conditions for a very wide range of electrical power never applied in the literature. The response of the new configuration can be considered linear for this very wide range of electrical power. An analytical calculation shows the contribution of each heat transfer in specific zones. 3D thermal simulations performed by means of COMSOL Multiphysics under irradiation conditions give the predictions of the calorimeter behavior under real conditions (up to 20W.g−1).

Study of the Flow Temperature and Ring Design Influence on the Response of a New Reduced-Size Calorimetric Cell for Nuclear Heating Quantification

This paper concerns experimental studies of different designs of a new compact calorimetric cell under laboratory conditions. This kind of cell is used for the measurement of the nuclear heating rate inside Material Testing Reactors thanks to differential calorimetry. The results, obtained by applying an operating protocol corresponding to a preliminary out-of-pile calibration step, are presented for three designs. The influence of the horizontal-fin design is shown on the calibration curve and the sensor sensitivity. The influence of the external fluid flow temperature is given for the quarter design. The different responses of the calorimetric cell are explained by taken into account a 1D analytical thermal model coupling thermal conductive and radiative transfers.

Review of Nuclear Heating Measurement by Calorimetry in France and USA

This paper gives a short review of sensors dedicated to measuring nuclear heating rate inside fission reactors in France and USA and especially inside Material Testing Reactors. These sensors correspond to heat flow calorimeters composed of a single calorimetric cell or of two calorimetric cells at least with a reference cell to obtain a differential calorimeter. The aim of this paper is to present the common running principle of these sensors and their own special characteristics through their design, calibration methods, and in-pile measurement techniques, and to describe multi-sensor probes including calorimeters.

Model for ion injection into a quadrupole ion trap to assess the distribution of initial conditions of confinement

A pulsed ion-injection mode for a quadrupole ion trap is described. Switched direct current (d.c.) potentials are applied to the source and trap electrodes to inject the ions into the trap and slow them down. The injection time is sufficient to ensure a steady distribution of the injected ions at the beginning of the confinement. An elementary uni-dimensional model is detailed giving the axial positions and velocities of the ions injected into the trap. The ion distribution in phase space, the number of injected ions and the number of injected ions that will be trapped are also given. These expressions depend on ion position and velocity at the creation, applied potentials and spatial location of the source and trap electrodes. This model is validated by comparing simulation and experimental results. For this purpose the number of confined ions is plotted versus the slowing-down potentials applied on the ring and the upper end-cap of the trap. The size of the area of removable ions in the source is deduced from these results.

Characterization of a familial t(16;22) balanced translocation associated with congenital cataract leads to identification of a novel gene, TMEM114, expressed in the lens and disrupted by the translocation

Molecular characterization of chromosomal rearrangements is a powerful resource in identification of genes associated with monogenic disorders. We describe the molecular characterization of a balanced familial chromosomal translocation, t(16;22)(p13.3;q11.2), segregating with congenital lamellar cataract. This led to the discovery of a cluster of lens-derived expressed sequence tags (ESTs) close to the 16p13.3 breakpoint. This region harbors a locus associated with cataract and microphthalmia. Long-range PCR and 16p13.3 breakpoint sequencing identified genomic sequence in a human genome sequence gap, and allowed identification of a novel four-exon gene, designated TMEM114, which encodes a predicted protein of 223 amino acids. The breakpoint lies in the promoter region of TMEM114 and separates the gene from predicted eye-specific upstream transcription factor binding sites. There is sequence conservation among orthologs down to zebrafish. The protein is predicted to contain four transmembrane domains with homology to the lens intrinsic membrane protein, LIM2 (also known as MP20), in the PMP-22/EMP/MP20 family. TMEM114 mutation screening in 130 congenital cataract patients revealed missense mutations leading to the exchange of highly-conserved amino acids in the first extracellular domain of the protein (p.I35T, p.F106L) in two separate patients and their reportedly healthy sibling and mother, respectively. In the lens, Tmem114 shows expression in the lens epithelial cells extending into the transitional zone where early fiber differentiation occurs. Our findings implicate dysregulation of expression of this novel human gene, TMEM114, in mammalian cataract formation.

Non-linearity influences on the axial secular-motion spectrum of ions confined in a Fourier transform ion trap mass spectrometer. Experimental studies

A Fourier transform operating mode is applied to an ion trap. The trap is truncated at 2r(0) and presents unwanted defects that induce confinement electric-field non-linearities. Ion axial secular-motion spectrum is examined by experiments near the resonance line beta(z) = 0.5. Ion-loss processes and ion axial-motion peak splitting are observed. In the non-linear ion trap, the ion-motion frequency depends on its initial conditions in position and velocity. This brings an enlargement of the motion-frequency peak and limits the resolution. With a 2r(0) truncated ion trap, the Fourier transform ion trap mass spectrometer (FTIT-MS) leads experimentally to a mass resolution of about 4000 at 130 u.

Domain disruption and mutation of the bZIP transcription factor, MAF, associated with cataract, ocular anterior segment dysgenesis and coloboma

Human congenital cataract and ocular anterior segment dysgenesis both demonstrate extensive genetic and phenotypic heterogeneity. We identified a family where ocular developmental abnormalities (cataract, anterior segment dysgenesis and microphthalmia) co-segregated with a translocation, t(5;16)(p15.3;q23.2), in both balanced and unbalanced forms. We hypothesized that this altered the expression of a gene of developmental significance in the human lens and ocular anterior segment. Cloning the 16q23.2 breakpoint demonstrated that it transected the genomic-control domain of MAF, a basic region leucine zipper (bZIP) transcription factor, first identified as an oncogene, which is expressed in vertebrate lens development and regulates the expression of the eye lens crystallins. The homozygous null mutant Maf mouse embryo demonstrates defective lens formation and microphthalmia. Through mutation screening of a panel of patients with hereditary congenital cataract we identified a mutation in MAF in a three-generation family with cataract, microcornea and iris coloboma. The mutation results in the substitution of an evolutionarily highly conserved arginine with a proline at residue 288 (R288P) in the basic region of the DNA-binding domain of MAF. Our findings further implicate MAF/Maf in mammalian lens development and highlight the role of the lens in anterior segment development. The 16q23.2 breakpoint transects the common fragile site, FRA16D, providing a molecular demonstration of a germline break in a common fragile site.

Coupling of a Rydberg electron capture ion source with a quadrupole mass filter

The coupling of a Rydberg electron capture ion source with a Nermag R10-10H quadrupole mass filter is described. Details are given of the addition to this instrument of a creation cell for atoms excited in Rydberg states. Within the Nermag ion source, such atoms allow attachment of electrons of well-defined thermal energy. SF(6) was used for optimization of the main experimental parameters (gas pressures and voltages applied to the electrodes). The procedure by which Rydberg electron attachment was confirmed is described. A polychlorobiphenyl compound was used to illustrate the performance of this ionization technique. Ion formation was observed in the absence of fragmentation.

Utility of CT scan for the diagnosis of chest wall tuberculosis

The objective of this study was to determine the utility of CT scan findings for the diagnosis of chest wall tuberculosis, excluding the spine. We reviewed 15 patients (13 Africans and 2 Indians) with chest wall tuberculosis, retrospectively. The radiologic examination consisted of a plain X-ray and a CT scan of the chest for each patient. The site of disease was the rib in 13 patients or the body of the sternum in 2 patients. One rib was involved in 11 patients, 2 contiguous ribs (one site) in 2 patients, and bilateral disease (two sites) was observed in the remaining patient. The 14 rib sites involved the posterior arc or costovertebral joint in 11 cases, the anterior arc in 2 cases, and the anterior and middle arc in 1 case. The CT scan findings were an abscess (n = 14) or a soft tissue mass (n = 2), osteolytic lesions (n = 13), periosteal reaction (n = 10), and sequestrum (n = 14). Bone sclerosis was observed only in 3 cases of rib involvement. The association of a soft tissue abscess, an osteolytic lesion, and sequestrum, especially in immigrants to France, suggests chest wall tuberculosis on CT scan.

A transcription factor involved in skeletal muscle gene expression is deleted in patients with Williams syndrome

Williams-Beuren syndrome (WS) is a developmental disorder caused by a hemizygous microdeletion of approximately 1.4MB at chromosomal location 7q11.23. The transcription map of the WS critical region is not yet complete. We have isolated and characterised a 3.4 kb gene, GTF3, which occupies about 140 kb of the deleted region. Northern blot analysis showed that the gene is expressed in skeletal muscle and heart, and RT-PCR analysis showed expression in a range of adult tissues with stronger expression in foetal tissues. Part of the conceptual GTF3 protein sequence is almost identical to a recently reported slow muscle-fibre enhancer binding protein MusTRD1, and shows significant homology to the 90 amino-acid putative helix-loop-helix repeat (HLH) domains of the transcription factor TFII-I (encoded for by the gene GTF2I). These genes may be members of a new family of transcription factors containing this HLH-like repeated motif. Both GTF3 and GTF2I map within the WS deleted region, with GTF2I being positioned distal to GTF3. GTF3 is deleted in patients with classic WS, but not in patients we have studied with partial deletions of the WS critical region who have only supravalvular aortic stenosis. A feature of WS is abnormal muscle fatiguability, and we suggest that haploinsufficiency of the GTF3 gene may be the cause of this.

Reactivity of 87 monoclonal antibodies against tissues in vivo and resting and irradiated endothelial cells in vitro

Altered expression of vascular endothelial cell (EC) surface antigens in response to irradiation is one of the early events of radiation-induced damage. Using flow cytometry, we investigated the immunocytochemical reactivity of a blind panel comprising 87 mAbs submitted to the endothelial section of the 6th International Workshop on Human Leukocyte Differentiation Antigens with irradiated and resting human dermal microvascular endothelial (HDME) and EA cell lines. Monolayers of irradiated cells received a single 5 Gy dose of 72 h prior to staining but were otherwise treated the same as resting cells. For comparative purposes we have also examined the immunohistochemical reactivity of the mAb panel with EC in ovarian tumour, Wilms' tumour and human placenta. In the flow cytometry experiments 42 and 44 mAbs stained HDME and EA cells respectively and while no antibody stained irradiated but not unirradiated cells, upregulation was seen for CD31, CD34, CD141 and CD146 in irradiated cells. The upregulation of thrombomodulin (CD141) is noteworthy since it is a marker of EC damage and thus may be a useful reagent in investigations of vascular injury. Comparison with tissue staining showed that 21 mAbs were reactive with at least one tissue but not with either EA or HDME cells. Nine mAbs showed no cross reactivity with tissue and of these one reacted with EA cells only.

Glucosaminylmuramyl dipeptide (GMDP) modulates endothelial cell activities in vitro but has no effect on angiogenesis in vivo

OBJECTIVE AND DESIGN

The aim of the study was to evaluate the effects of GMDP on angiogenesis in vivo and as a modulator of human umbilical vein endothelial cell proliferation, cell surface antigen expression and cell adhesion in vitro.

MATERIALS

Human umbilical vein endothelial cells (HUVEC), fertilized white leghorn chicken eggs, antibodies against adhesion molecules and glucosaminylmuramyl dipeptide (GMDP).

TREATMENT

GMDP [0.01-100 micrograms/ml] applied to cell cultures for 6-72 h and to the chick chorioallantoic membrane (CAM) for four days.

METHODS

Angiogenic activity of GMDP in vivo was assessed using the CAM assay; HUVEC proliferation was measured by tritiated thymidine incorporation and cell cycle studies; cell surface antigen expression by indirect immunofluorescence and flow cytometry; cell adhesion by quantification of [3H]-thymidine labeled leukocyte adherence to HUVEC monolayers. Statistical analysis was performed using one-way ANOVA and if necessary was followed by Duncan's multiple range test for variables.

RESULTS

GMDP induced [3H]-thymidine incorporation in a concentration- and time-dependent manner (p < 0.003) and significantly increased the porportion of cells in the S phase of the cell cycle (p < 0.03). It weakly augmented the expression of ICAM-1 and CD31 but not adhesion of leukocytes to HUVEC monolayers GMDP was not angiogenic in the CAM assay.

CONCLUSIONS

GMDP can modulate endothelial cell activity without the induction of angiogenesis in vivo which may have implications for its use as a therapeutic agent.