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[en] The CNSC (Canadian Nuclear Safety Commission) evaluates the safety performance of nuclear power plant (NPP) licensees and prepares an annual report on their safety performance referred to as the Regulatory Oversight Report, which is presented to the Commission and is subsequently published on the CNSC web page. Prior to 2017, the report was referred to as the Regulatory Oversight Report for Canadian NPPs. However, in 2017, the report was expanded to include the safety performance evaluation of waste management facilities located at NPP sites. The report has been renamed as the Regulatory Oversight Report for Canadian Nuclear Power Generating Sites. The CNSC evaluates how well licensees meet regulatory requirements and CNSC expectations for the performance of programmes in 14 safety and control areas (SCAs) that are grouped in accordance with their functional areas of management, facility and equipment, or core control processes. These SCAs are further divided into 71 specific areas that define the key components of the SCA. The functional areas, SCAs and the specific areas that are used in CNSC’s safety performance evaluation are presented. An example of safety performance ratings for Canadian NPPs is given. An example of a conclusion of a CNSC Regulatory Oversight Report for Canadian Nuclear Power Generating Sites is as follows: The evaluations of all findings for the SCAs show that, overall, NPP licensees made adequate provisions for the protection of health, safety and security of Canadians and the environment from the use of nuclear energy, and took the necessary measures to implement Canada’s international obligations.
[en] GaN/AlN resonant tunneling diodes (RTDs) are studied to realize a high-speed nonvolatile memory based on the intersubband transactions and electron accumulation in the quantum well, which has the potential to operate at picosecond time scales. The crystal quality of GaN/AlN RTDs is improved by changing the growth conditions and structure of the buffer layer. The surface roughness and dislocation density of the GaN/AlN RTDs are successfully suppressed, and clear ON/OFF switching due to intersubband transitions is observed by inputting pulse voltage sequences. However, the voltages for write and erase operations are changed by improving the crystal quality of GaN/AlN RTDs. The theoretical analysis of resonant levels in the GaN/AlN RTDs indicates that the voltages for write and erase operations are very sensitive to the well and barrier widths and the density of electrons accumulating in the quantum well. Based on the results, the design of GaN/AlN RTDs for higher-performance nonvolatile memory operations is investigated. (© 2020 Wiley‐VCH GmbH)
[en] Herein, we present a new strategy for the synthesis of 2D porous MoP/MoN heterojunction nanosheets based on the pyrolysis of 2D [PMoO]-melamine (PMo-MA) nanosheet precursor from a polyethylene glycol (PEG)-mediated assembly route. The heterostructure nanosheets are ca. 20 nm thick and have plentiful pores (<5 nm). These structure features offer advantages to promote the HER activity, including the favorable water dissociation kinetics around heterojunction as confirmed by theoretical calculations, large accessible surface of 2D nanosheets, and enhanced mass-transport ability by pores. Consequently, the 2D porous MoP/MoN heterojunction nanosheets exhibit excellent HER activity with low overpotentials of 89, 91 and 89 mV to achieve a current density of 10 mA cm in alkaline, neutral and acidic electrolytes, respectively. The HER performance is superior to the commercial Pt/C at a current density >55 mA cm in neutral medium and >190 mA cm in alkaline medium. (© 2021 Wiley‐VCH GmbH)
[en] With conventional MRI, it is often difficult to effectively differentiate between contrast-enhancing brain tumors, including primary central nervous system lymphoma (PCNSL), high-grade glioma (HGG), and metastasis. This study aimed to assess the discrimination ability of the parameters obtained from DWI and the percentage signal recovery- (PSR-) optimized protocol of DSC-MRI between these three tumor types at an initial step. DSC-MRI using a PSR-optimized protocol (TR/TE = 1500/30 ms, flip angle = 90°, no preload) and DWI of 99 solitary enhancing tumors (60 HGGs, 24 metastases, 15 PCNSLs) were retrospectively assessed before treatment. rCBV, PSR, ADC in the tumor core and rCBV, and ADC in peritumoral edema were measured. The differences were evaluated using one-way ANOVA, and the diagnostic performance was evaluated using ROC curve analysis. PSR in the tumor core showed the best discriminating performance in differentiating these three tumor types with AUC values of 0.979 for PCNSL vs. others and 0.947 for HGG vs. metastasis. The ADC was only helpful in the tumor core and distinguishing PCNSLs from others (AUC = 0.897). Different from CBV-optimized protocols (preload, intermediate FA), PSR derived from the PSR-optimized protocol seems to be the most important parameter in the differentiation of HGGs, metastases, and PCNSLs at initial diagnosis. This property makes PSR remarkable and carries the need for comprehensive DSC-MRI protocols, which provides PSR sensitivity and CBV accuracy together, such as the preload use of the PSR-optimized protocol before the CBV-optimized protocol.
[en] To evaluate the efficiency of 2- and 3-class classification predictive tasks constructed from radiomics features extracted from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) pharmacokinetic (PK) protocol in discriminating among benign, borderline, and malignant ovarian tumors. One hundred and four ovarian lesions were evaluated using preoperative DCE-MRI. Radiomics features were extracted from 7 types of DCE-MR images. To explore the differential ability of radiomics between three types of ovarian tumors, two- and three-class classification tasks were established. The 2-class classification task was divided into three subtasks: benign vs. borderline (task A), benign vs. malignant (task B), and borderline vs. malignant (task C). For the 3-class classification task, 104 lesions were randomly divided into training (72 lesions) and validation (32 lesions) cohorts. The discrimination abilities of the radiomics signatures were established with the training cohort and tested with the independent validation cohort. The predictive performance of the task was evaluated by receiver operating characteristic (ROC) curve, calibration curve analysis, and decision curve analysis (DCA). For the 2-class classification task, the combination of PK radiomics signatures model (PK model) showed a good diagnostic ability with the highest area under the ROC curves (AUCs) of 0.899, 0.865, and 0.893 for tasks A, B, and C, respectively. Additionally, the 3-class classification task demonstrated a good discrimination performance with AUCs of 0.893, 0.944, and 0.891 for the benign, borderline, and malignant groups, respectively. Radiomics analysis based on the DCE-MRI PK protocol showed promise for discriminating among benign, borderline, and malignant ovarian tumors.
[en] An experiment has been conducted to evaluate the lifetime, reliability and operational performance of elementary semiconductor devices in the neutron radiation environment which supports to reduce the fatal in measurements and plan the preventive actions in nuclear facilities. It will also support the enhancement of electronics for nuclear facilities. The elementary semiconductor devices used in the experiment are Diode (1n4007), Zener Diode (5.1v), Light Emitting Diode, Transistor (BC547, 2n3904), Voltage controlling IC (7805), Operational Amplifier (LM741) and Optocoupler (4n35). The selection of devices has been made by keeping in mind their application in transmitting devices (i.e. Temperature transmitter, pressure transmitter, flow transmitter, monitors and controllers) for Indian test blanket system in ITER. Such devices are also used in general nuclear electronics. The devices have been irradiated in the Am-Be neutron source environment. The maximum fluence has been given up to 1011 n/cm2. The neutron source has energy range from low to high. All semiconductor devices have been characterized before and after irradiations. The deviation of 5 - 10% is observed in diodes I-V characteristics whereas transistors show a bit higher deflection in basic functionality. Optocoupler shows more than 50% deviation in its basic characteristics whereas voltage-controlling IC is not even functioning after the irradiation of 1011 n/cm2. The paper describes the details of the experiment and the behavior of semiconductor devices after irradiation. The experiment supports the selection and further research of the Indian test blanket system instruments. (author)
[en] The worldwide comparison of stable 15N and 13C isotope measurements provides confidence in the analytical performance of stable isotope laboratories and hence an important tool for external quality control. The 2020 Proficiency Test (PT) on 15N and 13C isotopic abundance in plant materials, organized by the University of Wageningen, the Netherlands, and funded by the SWMCN Laboratory has been successfully completed. The Wageningen Evaluating Programs for Analytical Laboratories (WEPAL, http://www.wepal.nl) is accredited for the organization of Inter-Laboratory Studies by the Dutch Accreditation Council. Every year, one FAO/IAEA 15N-enriched and three not 15N-enriched test samples are included in one round of the WEPAL IPE (International Plant-Analytical Exchange) programme. A special evaluation report for IAEA participants on the analytical performance in stable isotope analysis is issued by the SWMCN Laboratory and sent to the participants together with a certificate of participation in addition to the regular WEPAL evaluation report.
[en] We report experiments in which radiatively metastable 2 S positronium (Ps) atoms entered a waveguide whose internal surfaces were lined with smoked magnesium oxide (MgO) powder. The waveguide was built such that time-delayed microwave radiation pulses, tuned to drive 2 S→2 P transitions, could be applied to the Ps ensemble. The lifetime of 2 S atoms was measured using time-delayed microwave induced decay, yielding ≈200 ns. This is considerably shorter than the Zeeman shifted lifetime of 1070 ns, indicating that Ps atoms in the 2 S state do not survive multiple collisions with MgO nanocrystals.
[en] 3D multi-echo gradient-recalled echo (ME-GRE) can simultaneously generate time-of-flight magnetic resonance angiography (pTOF) in addition to T2*-based susceptibility-weighted images (SWI). We assessed the clinical performance of pTOF generated from a 3D ME-GRE acquisition compared with conventional TOF-MRA (cTOF). Eighty consecutive children were retrospectively identified who obtained 3D ME-GRE alongside cTOF. Two blinded readers independently assessed pTOF derived from 3D ME-GRE and compared them with cTOF. A 5-point Likert scale was used to rank lesion conspicuity and to assess for diagnostic confidence. Across 80 pediatric neurovascular pathologies, a similar number of lesions were reported on pTOF and cTOF (43–40%, respectively, p > 0.05). Rating of lesion conspicuity was higher with cTOF (4.5 ± 1.0) as compared with pTOF (4.0 ± 0.7), but this was not significantly different (p = 0.06). Diagnostic confidence was rated higher with cTOF (4.8 ± 0.5) than that of pTOF (3.7 ± 0.6; p < 0.001). Overall, the inter-rater agreement between two readers for lesion count on pTOF was classified as almost perfect (κ = 0.98, 96% CI 0.8–1.0). In this study, TOF-MRA simultaneously generated in addition to SWI from 3D MR-GRE can serve as a diagnostic adjunct, particularly for proximal vessel disease and when conventional TOF-MRA images are absent.
[en] Few studies have examined the geometry of endovascular mechanical thrombectomy pathways. Here we examine the tortuosity and angulations of catheter pathways from the aortic arch to the termination of the internal carotid artery (ICA) and its association with thrombectomy performance. We included 100 consecutive anterior circulation large vessel occlusion thrombectomy patients over 12 months. Computed tomography angiograms (CTA) were used for 3D segmentation of catheter pathway from the aortic arch to ICA termination. Tortuosity index (TI) and angulations of the catheter pathway were measured in a semi-automated fashion. TI and angulation degree were compared between sides and correlated with age and procedural measures. We analyzed 188 catheter pathways in 100 patients. Severe angulation (≤ 30°) was present in 5.8% and 39.4% of common carotid artery (CCA) and extracranial ICA segments, respectively. Five pathways (2.6%) had 360° loop. CCA and extracranial ICA tortuosity had a weak but significant correlation with age (r = 0.17, 0.21, p value = 0.05, 0.02 respectively), time from groin puncture to the site of occlusion (r = 0.29, 0.25, p values = 0.008, 0.026 respectively), and fluoroscopy time (r = 0.022, 0.31, p values = 0.016, 0.001 respectively). There was a significant difference in the pattern of angulation (p value = 0.04) and tortuosity between right and left side in CCA segment (TI = 0.20 ± 0.086 vs. 0.15 ± 0.82, p value < 0.001). There was a significant difference in CCA angulation between right and left sides. TI of extracranial CCA and ICA correlated with age and influenced time from groin puncture to the occlusion site and total fluoroscopy time.