Scaling Issues for the Experimental Characterization of Reactor Coolant System in Integral Test Facilities and Role of System Code as Extrapolation Tool

The phenomenological analyses and thermal hydraulic characterization of a nuclear reactor are the basis for its design and safety evaluation. In light of the impossibility and huge cost of performing meaningful experiments at full scale, scaled down experimental tests - Integral Effect Test (IET) and Separate Effect Test (SET) - are more feasible in developing “assessment database”. The data are useful in characterizing the prototype design and in the validation of computational tools for safety analysis. The analyses of system behaviors including component interactions in the Reactor Coolant System (RCS), the Containment System (PCV) and the RCS/PCV coupled system have been extensively investigated using IETs in the past decades. Though several scaling methods, e.g. Linear, Power/Volume, Three level scaling, H2TS..., have been developed and applied in the IET and SET design, a direct extrapolation of the data to the prototype, i.e. the scalability, is in general not possible due to unavoidable scaling distortions. The scaling distortions are related to many factors, mainly the complex geometry, multiple component interactions and two phase thermal hydraulic phenomena in steady state and transient condition of a nuclear reactor. The complex nature of scaling a nuclear reactor requires a large number of scaling parameters to be simultaneously fulfilled. In addition, physical construction and funding constraints demand that a scaling compromise is inevitable. Therefore a scaling approach, e.g. time preserved/not preserved, full height/reduced height, full pressure/reduced pressure, full power/reduced power…, has to be adopted in accordance with the objective of the IET or SET. Together with the scaling analysis, Best Estimate (BE) thermal hydraulic system code has been used for supporting experiment activity (design facilities, interpretation of results, etc) and for extrapolating results to full scale prototype conditions. Since the closure laws in the system code are mainly based on scaled test data, the extrapolation of code results remains a challenging and open issue. Starting from a brief analysis of the main characteristics of IETs and SETFs, the main objective of this paper is to analyze some IET scaling approaches used to the simulation of RCS responses which characterize the main scaling limits. The scaling approaches and their constraints in ROSA-III, FIST and PIPER-ONE facility will be used to analyze their impact to the experimental prediction in Small Break LOCA counterpart tests. The liquid level behavior in the core and the core cladding temperature analysis are discussed used as judging criteria for the facilities scaling-up limits

Association of war zone–related stress with alterations in limbic gray matter microstructure

IMPORTANCE: Military service members returning from theaters of war are at increased risk for mental illness, but despite high prevalence and substantial individual and societal burden, the underlying pathomechanisms remain largely unknown. Exposure to high levels of emotional stress in theaters of war and mild traumatic brain injury (mTBI) are presumed factors associated with risk for the development of mental disorders. OBJECTIVE: To investigate (1) whether war zone–related stress is associated with microstructural alterations in limbic gray matter (GM) independent of mental disorders common in this population, (2) whether associations between war zone–related stress and limbic GM microstructure are modulated by a history of mTBI, and (3) whether alterations in limbic GM microstructure are associated with neuropsychological functioning. DESIGN, SETTING, AND PARTICIPANTS: This cohort study was part of the TRACTS (Translational Research Center for TBI and Stress Disorders) study, which took place in 2010 to 2014 at the Veterans Affair Rehabilitation Research and Development TBI National Network Research Center. Participants included male veterans (aged 18-65 years) with available diffusion tensor imaging data enrolled in the TRACTS study. Data analysis was performed between December 2017 to September 2021. EXPOSURES: The Deployment Risk and Resilience Inventory (DRRI) was used to measure exposure to war zone–related stress. The Boston Assessment of TBI-Lifetime was used to assess history of mTBI. Stroop Inhibition (Stroop-IN) and Inhibition/Switching (Stroop-IS) Total Error Scaled Scores were used to assess executive or attentional control functions. MAIN OUTCOMES AND MEASURES: Diffusion characteristics (fractional anisotropy of tissue [FA(T)]) of 16 limbic and paralimbic GM regions and measures of functional outcome. RESULTS: Among 384 male veterans recruited, 168 (mean [SD] age, 31.4 [7.4] years) were analyzed. Greater war zone–related stress was associated with lower FA(T) in the cingulate (DRRI-combat left: P = .002, partial r = −0.289; DRRI-combat right: P = .02, partial r = −0.216; DRRI-aftermath left: P = .004, partial r = −0.281; DRRI-aftermath right: P = .02, partial r = −0.219), orbitofrontal (DRRI-combat left medial orbitofrontal cortex: P = .02, partial r = −0.222; DRRI-combat right medial orbitofrontal cortex: P = .005, partial r = −0.256; DRRI-aftermath left medial orbitofrontal cortex: P = .02, partial r = −0.214; DRRI-aftermath right medial orbitofrontal cortex: P = .005, partial r = −0.260; DRRI-aftermath right lateral orbitofrontal cortex: P = .03, partial r = −0.196), and parahippocampal (DRRI-aftermath right: P = .03, partial r = −0.191) gyrus, as well as with higher FA(T) in the amygdala-hippocampus complex (DRRI-combat: P = .005, partial r = 0.254; DRRI-aftermath: P = .02, partial r = 0.223). Lower FA(T) in the cingulate-orbitofrontal gyri was associated with impaired response inhibition (Stroop-IS left cingulate: P < .001, partial r = −0.440; Stroop-IS right cingulate: P < .001, partial r = −0.372; Stroop-IS left medial orbitofrontal cortex: P < .001, partial r = −0.304; Stroop-IS right medial orbitofrontal cortex: P < .001, partial r = −0.340; Stroop-IN left cingulate: P < .001, partial r = −0.421; Stroop-IN right cingulate: P < .001, partial r = −0.300; Stroop-IN left medial orbitofrontal cortex: P = .01, partial r = −0.223; Stroop-IN right medial orbitofrontal cortex: P < .001, partial r = −0.343), whereas higher FA(T) in the mesial temporal regions was associated with improved short-term memory and processing speed (left amygdala-hippocampus complex: P < .001, partial r = −0.574; right amygdala-hippocampus complex: P < .001, partial r = 0.645; short-term memory left amygdala-hippocampus complex: P < .001, partial r = 0.570; short-term memory right amygdala-hippocampus complex: P < .001, partial r = 0.633). A history of mTBI did not modulate the association between war zone–related stress and GM diffusion. CONCLUSIONS AND RELEVANCE: This study revealed an association between war zone–related stress and alteration of limbic GM microstructure, which was associated with cognitive functioning. These results suggest that altered limbic GM microstructure may underlie the deleterious outcomes of war zone–related stress on brain health. Military service members may benefit from early therapeutic interventions after deployment to a war zone

Exposure to repetitive head impacts is associated with corpus callosum microstructure and plasma total tau in former professional American football players

BACKGROUND: Exposure to repetitive head impacts (RHI) is associated with an increased risk of later-life neurobehavioral dysregulation and neurodegenerative disease. The underlying pathomechanisms are largely unknown. PURPOSE: To investigate whether RHI exposure is associated with later-life corpus callosum (CC) microstructure and whether CC microstructure is associated with plasma total tau and neuropsychological/neuropsychiatric functioning. STUDY TYPE: Retrospective cohort study. POPULATION: Seventy-five former professional American football players (age 55.2 ± 8.0 years) with cognitive, behavioral, and mood symptoms. FIELD STRENGTH/SEQUENCE: Diffusion-weighted echo-planar MRI at 3 T. ASSESSMENT: Subjects underwent diffusion MRI, venous puncture, neuropsychological testing, and completed self-report measures of neurobehavioral dysregulation. RHI exposure was assessed using the Cumulative Head Impact Index (CHII). Diffusion MRI measures of CC microstructure (i.e., free-water corrected fractional anisotropy (FA), trace, radial diffusivity (RD), and axial diffusivity (AD)) were extracted from seven segments of the CC (CC1-7), using a tractography clustering algorithm. Neuropsychological tests were selected: Trail Making Test Part A (TMT-A) and Part B (TMT-B), Controlled Oral Word Association Test (COWAT), Stroop Interference Test, and the Behavioral Regulation Index (BRI) from the Behavior Rating Inventory of Executive Function, Adult version (BRIEF-A). STATISTICAL TESTS: Diffusion MRI metrics were tested for associations with RHI exposure, plasma total tau, neuropsychological performance, and neurobehavioral dysregulation using generalized linear models for repeated measures. RESULTS: RHI exposure was associated with increased AD of CC1 (correlation coefficient (r) = 0.32, P < 0.05) and with increased plasma total tau (r = 0.34, P < 0.05). AD of the anterior CC1 was associated with increased plasma total tau (CC1: r = 0.30, P < 0.05; CC2: r = 0.29, P < 0.05). Higher trace, AD, and RD of CC1 were associated with better performance (P < 0.05) in TMT-A (trace, r = 0.33; AD, r = 0.31; and RD, r = 0.28) and TMT-B (trace, r = 0.31; RD, r = 0.34). Higher FA and AD of CC2 were associated with better performance (P < 0.05) in TMT-A (FA, r = 0.36; AD, r = 0.28), TMT-B (FA, r = 0.36; AD, r = 0.27), COWAT (FA, r = 0.36; AD, r = 0.32), and BRI (AD, r = 0.29). DATA CONCLUSION: These results suggest an association among RHI exposure, CC microstructure, plasma total tau, and clinical functioning in former professional American football players. LEVEL OF EVIDENCE: 3 Technical Efficacy Stage: 1

Custom Integrated Circuits

Contains reports on nine research projects.Analog Devices, Inc.International Business Machines CorporationJoint Services Electronics Program Contract DAAL03-89-C-0001U.S. Air Force - Office of Scientific Research Contract AFOSR 86-0164BDuPont CorporationNational Science Foundation Grant MIP 88-14612U.S. Navy - Office of Naval Research Contract N00014-87-K-0825American Telephone and TelegraphDigital Equipment CorporationNational Science Foundation Grant MIP 88-5876

Custom Integrated Circuits

Contains reports on twelve research projects.Analog Devices, Inc.International Business Machines, Inc.Joint Services Electronics Program (Contract DAAL03-86-K-0002)Joint Services Electronics Program (Contract DAAL03-89-C-0001)U.S. Air Force - Office of Scientific Research (Grant AFOSR 86-0164)Rockwell International CorporationOKI Semiconductor, Inc.U.S. Navy - Office of Naval Research (Contract N00014-81-K-0742)Charles Stark Draper LaboratoryNational Science Foundation (Grant MIP 84-07285)National Science Foundation (Grant MIP 87-14969)Battelle LaboratoriesNational Science Foundation (Grant MIP 88-14612)DuPont CorporationDefense Advanced Research Projects Agency/U.S. Navy - Office of Naval Research (Contract N00014-87-K-0825)American Telephone and TelegraphDigital Equipment CorporationNational Science Foundation (Grant MIP-88-58764

Custom Integrated Circuits

Contains reports on ten research projects.Analog Devices, Inc.IBM CorporationNational Science Foundation/Defense Advanced Research Projects Agency Grant MIP 88-14612Analog Devices Career Development Assistant ProfessorshipU.S. Navy - Office of Naval Research Contract N0014-87-K-0825AT&TDigital Equipment CorporationNational Science Foundation Grant MIP 88-5876

Pressure drops in nuclear thermal-hydraulics: Principles, experiments, and modelling - Chapter 8

Pressure drops and heat transfer are of main concern in system thermal-hydraulics. This reflects in the importance of related modeling and results of system code application to the prediction of accident scenarios in Nuclear Power Plants. Although pressure drops and heat transfer constitute key parts of the modeling for system thermal-hydraulic codes, discussed in Chapters 5 and 9 of the book, special devoted chapters are foreseen, namely Chapter 7 and current chapter dealing with heat transfer and pressure drop, respectively. Pressure drop models are characterized by a long history dated since the beginning of previous century as discussed in Chapter 2 of the book and outlined in this chapter. Furthermore, pressure drops directly affect the phenomena and the accident scenarios discussed in Chapters 6 and 15 of the book. The discussion in this chapter shall be seen as complementary and linked to what discussed in those chapters. Qualification is discussed in Chapter 13 of the book and directly includes pressure drop models

FFTBM assessment of reverse natural circulation transient in PKL test facility

The fast Fourier transform based method (FFTBM) was proposed in the 1990s and is used for accuracy quantification of computer codes. FFTBM provides frequency-based measures for each single TH variables as well as the whole transient calculations. The measurement-prediction discrepancies in the frequency domain are assessed by the average amplitude (AA), which is dependent to the proper selection of time windows, weighting factors, number of discrete data used. This paper summaries the application of FFTBM from publications in the last 30 years based on the previous review papers. It attempts to provide some insights and guidelines for FFTBM application. The second part deals with the applications of FFTBM for code accuracy quantification, to perform a sensitivity analysis on loss coefficients at geometric discontinuities in the framework of a virtual benchmark activity. RELAP5/MOD3.3 code was used for calculation, with qualified nodalizations for PKL test facility. The objective of the virtual benchmark and the sensitivity calculation is to investigate the impact of pressure drop modeling inadequacies in the selected transients

Prioritizing pressure drop research in nuclear thermal hydraulics

Prediction of pressure drop by wall friction and at geometric discontinuities is important in nuclear thermal hydraulics simulation. Pressure-drop models were established and upgraded for decades; however, errors in predictions of experimental data are up to 40%, namely in low flow and two-phase conditions and particularly at geometric discontinuities. In order to clarify the impact in situations of interest for nuclear reactors, noticeably accident scenarios investigated in scaled experimental facilities, we propose a virtual benchmark on Reverse Natural Circulation (RNC) in the PKL test facility

Review of FONESYS and SILENCE Nuclear Thermal-Hydraulic Networks Achievements

The FONESYS and SILENCE networks are run by some of the leading organizations working in the nuclear sector, and work in a cooperative manner since about a decade having one or two meetings per year. The FONESYS members are developers of some of the major system thermal-hydraulic codes adopted worldwide. FONESYS has been created to strengthen the current technology, cooperate and share recent advances, identify and discuss further ways of improvements in system thermal-hydraulic code development and their application especially for licensing purposes and safety analyses. On the other hand, SILENCE members own and operate important thermal-hydraulic experimental facilities. SILENCE aimed at promoting: cooperation and knowledge transfer; discussion on state-of-the-art technological issues; revival of interest in significant experimental campaigns; support to organizations and countries embarking in large experimental programs. SILENCE is also the promoter of SWINTH, an international workshop on instrumentation and measurement techniques. In this paper selected key achievements from the networks are presented and some activities proposed to address the remaining issues in thermal-hydraulics are summarized