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AbstractWith the next generation of nuclear reactors under development, modeling and simulation tools are being developed by the U.S. Department of Energy to support their design, licensing, and future operation. Mirroring the physical test beds currently under construction (i.e., Demonstration and Operation of Microreactor Experiments, known as DOME, and Laboratory for Operating and Testing in the United States, known as LOTUS), the Virtual Test Bed was launched by the National Reactor Innovation Center in collaboration with the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program to support the advanced reactor community. This collaborative effort, which involves multiple teams at both Idaho National Laboratory and Argonne National Laboratory, aims to use state-of-the-art simulation tools to model a wide range of reactor designs. These models are automatically tested to ensure their continued functionality as the tools are further developed. Examples are extensively documented, each acting as a tutorial for applying the relevant NEAMS tools to that reactor design. Currently, five advanced reactor types (with a total of 12 specific design subvariants) are simulated by a variety of models. These models range from steady-state, core multiphysics simulations to integrated plant analysis during loss-of-flow transients. To our knowledge, this is the first publicly available library of multiphysics advanced reactor models distributed with extensive documentation and maintained through continuous integration.

Helical-coil steam generator (HCSG) technology is a major design candidate for small modular reactors due to its compactness and capability to produce superheated steam with high generation efficiency. In this paper, we investigate the feasibility of the passively autonomous power maneuvering by coupling the 3-D transient multi-physics of a soluble-boron-free (SBF) core with a time-dependent HCSG model. The predictor corrector quasi-static method was used to reduce the cost of the transient 3-D neutronic solution. In the numerical system simulations, the feedwater flow rate to the secondary of the HCSGs is adjusted to extract the demanded power from the primary loop. This varies the coolant temperature at the inlet of the SBF core, which governs the passively autonomous power maneuvering due to the strongly negative coolant reactivity feedback. Here, we simulate a 100-50-100 load-follow operation with a 5%/minute power ramping speed to investigate the feasibility of the passively autonomous load-follow in a 450 MWthSBF PWR. In addition, the passively autonomous frequency control operation is investigated. The various system models are coupled, and they are solved by an in-house Fortran-95 code. The results of this work demonstrate constant steam temperature in the secondary side and limited variation of the primary coolant temperature. Meanwhile, the variations of the core axial shape index and the core power peaking are sufficiently small.

Background: The dynamic on-bottom stability analysis represents a fundamental task in the design process of the subsea pipelines. Such analysis ensures the stability of the as-laid pipeline on the seabed against the lateral displacements, which are induced by the surrounding hydrodynamic forces. In this paper, the dynamic on-bottom stability analysis of a subsea pipeline is performed using finite element-based advanced offshore engineering simulation software called Flexcom. The latter predicts the pipeline response in a time-domain simulation based on a given environmental condition (i.e., the sea state, the soil frictional resistance, and the nonlinear behavior of the pipeline). A case study is conducted on a 22-in.-diameter pipeline, which is placed on a sandy soil in shallow water, under different loading combinations from two-dimensional irregular waves and a steady current. Results: The resultant maximum lateral displacements and the associated stresses decreased by increasing the concrete weight coating thickness. Pipeline response due to drag, lift, and inertia forces increased by increasing the total water particle velocity induced from the summation of wave-induced particle velocity and current velocity. Different random wave patterns generated from different random seed numbers assigned to wave components are important to verify the selection of the concrete weight coating thickness. Ignoring passive soil resistance reduced the total soil resistance significantly and resulted in conservative stability weight requirement. Conclusions: Several factors influence the pipeline stability such as pipeline submerged weight, hydrodynamic loads induced by random sea states, and soil friction model being used. The dynamic on-bottom stability analysis can optimize the design and results in less concrete weight coating if the actual case is modeled accurately; therefore, ignoring passive soil resistance reduced the prime advantage of this analysis compared to other simplified methods.

The assessment of students in community settings faces unique difficulties. Since students are usually posted in small groups in different community settings and since the learning (largely) takes place outside the classroom, assessing student performance becomes an intrinsically complex endeavor. In this article, the proposition is made and tested that peers may be used to accurately assess particular aspects of performance, in particular those which need extensive and close observation. Examples are: Effort displayed while working in a community, quality of the interaction with that community, display of leadership, and subject-matter contributions. The Faculty of Medicine of the University of Gezira, a community-based medical school, uses peer evaluation to assess these attributes of its students. Thirty four students divided into three groups participated in the present study. Goals of the study were to appraise the reliability, validity and acceptability of an instrument designed to measure these characteristics. Reliability was estimated using generalizability theory. A high generalizability coefficient (G) was found when all items were taken into account. In this case, G equaled 0.97. Its sub-scales each had also fairly high G-coefficients: Effort: 0.89, Subject-matter Contribution: 0.91, Community Interaction: 0.89, and Leadership: 0,88 respectively. The validity of the instrument was studied using confirmatory factor analysis. The results suggested that the proposed model of peer evaluation is reasonably valid. Finally, the instrument turned out to be quite acceptable to students.

No relevant conflicts of interest to declare.

Introduction:The vast majority ofmyeloproliferative neoplasms (MPNs) patients are characterized by a molecular genetic background and by variable symptoms reflecting disease burden that may correlate with prognosis.