Preliminary neutron kinetic. Thermal hydraulic coupled analysis of the ALFRED reactor using PHISICS/RELAP5-3D

The development of a lead-cooled fast reactor (LFR) demonstrator was proposed, mainly in EU, to investigate the feasibility of an industrial size ELFR (European Lead-cooled Fast Reactor). The demonstrator, called ALFRED (Advanced Lead-cooled Fast Reactor European Demonstrator), consists of a pool-type lead-cooled fast reactor, with a nominal thermal power of 300 MWt. This paper aims to verify the capability of the PHISICS/RELAP5-3D coupled approach to simulate transients of such reactor and to evaluate the effects of accidental scenarios relevant for the safety analysis on the system thermal-hydraulics and on the core power spatial evolution. RELAP5-3D©, developed at Idaho National Laboratory (INL), is a thermal-hydraulic system code, validated for a wide range of transient simulations. The code provides the possibility to simulate innovative working fluids (such as lead and lead alloys) and to use a fully integrated multi-dimensional nodalization. In addition, the need to study complex neutronic systems recommended the development of a new kinetic model allowing the calculation with any number of energy groups and also considering the transport for the angular variations. At this purpose, INL developed PHISICS (Parallel and Highly Innovative Simulation for INL Code System) and its coupling methodology with RELAP5-3D. The simulation activity described in this paper has been focused on the safety analysis of ALFRED reactor assuming the occurrence of two unprotected transient scenarios: unprotected loss of flow (ULOF) and unprotected transient overpower (UTOP). At this purpose, a thermal-hydraulic geometrical scheme of the whole reactor has been developed. The models and the outcomes of the calculations are described and discussed in the paper, highlighting the capability of the coupling approach to obtain results consistent with the ones available in the literature

On the critical energy required for homogeneous nucleation in bubble chambers employed in dark matter searches

Two equations for the calculation of the critical energy required for homogeneous nucleation in a superheated liquid, and the related critical radius of the nucleated vapour bubble, are obtained, the former by the direct application of the first law of thermodynamics, the latter by considering that the bubble formation implies the overcoming of a barrier of the free enthalpy potential. Comparisons with the currently used relationships demonstrate that the sensitivity of the bubble chambers employed in dark matter searches can be sometimes notably overestimated.Comment: 15 pages, 5 figures, 1 tabl

Effects of the thermodynamic conditions on the acoustic signature of bubble nucleation in superheated liquids used in dark matter search experiments

[EN] In the framework of the search for dark matter in the form of WIMPs using superheated liquids, a study is conducted to establish a computational procedure aimed at determining how the thermodynamic conditions kept inside a particle detector affect the acoustic signal produced by bubble nucleation. It is found that the acoustic energy injected into the liquid by the growing vapour bubble increases as the liquid pressure is decreased and the superheat degree is increased, the former effect being crucial for the generation of a well-intelligible signal. A good agreement is met between the results of the present study and some experimental data available in the literature for the amplitude of the acoustic signal. Additionally, the higher loudness of the alpha-decay events compared with those arising from neutron-induced nuclear recoils is described in terms of multiple nucleations.The authors are grateful to Walter Fulgione for the valuable discussions and suggestions and for his help in reviewing the manuscript.Ardid Ramírez, M.; Baschirotto, A.; Burgio, N.; Corcione, M.; Cretara, L.; De Matteis, L.; Felis-Enguix, I.... (2019). Effects of the thermodynamic conditions on the acoustic signature of bubble nucleation in superheated liquids used in dark matter search experiments. The European Physical Journal C. 79(11):1-9. https://doi.org/10.1140/epjc/s10052-019-7485-xS197911W.J. Bolte et al., Nucl. Instr. Meth. Phys. Res. A 577, 569–573 (2007)E. Behnke et al., Astropart. Phys. 90, 85–92 (2017)M. Felizardo et al., E3S Web Conf. 12, 03002 (2016)E. Behnke et al., Phys. Rev. D 88, 021101 (2013)C. Amole et al., Phys. Rev. Lett. 118, 251301 (2017)A. Antonicci et al., Eur. Phys. J. C 77, 752 (2017)D.A. Glaser, Phys. Rev. 87, 655 (1952)F. Seitz, Phys. Fluids 1, 2–13 (1958)E. Behnke et al., Phys. Rev. Lett. 106, 021303 (2011)D.A. Glaser, D.C. Rahm, Phys. Rev. 97, 474–479 (1955)Yu.N. Martynyuk, N.S. Smirnova, Sov. Phys. Acoust. 37, 376–378 (1991)F. Aubin et al., New J. Phys. 10, 103017 (2008)M. Felizardo et al., Nucl. Instr. Meth. Phys. Res. A 589, 72–84 (2008)P.K. Mondal, B.K. Chatterjee, Phys. Lett. A 375, 237–244 (2011)S. Archambault et al., New J. Phys. 13, 043006 (2011)C. Amole et al., Phys. Rev. Lett. 114, 231302 (2015)R. Sarkar et al., Phys. Lett. A 381, 2531–2537 (2017)I.A. Pless, R.J. Plano, Rev. Sci. Instr. 27, 935–937 (1956)D.V. Bugg, Progr. Nucl. Phys. 7, 2–52 (1959)A. Norman, P. Spiegler, Nucl. Sci. Eng. 16, 213–217 (1963)A.G. Tenner, Nucl. Instr. Meth. 22, 1–42 (1963)Ch. Peyrou, In Bubble and Spark Chambers (Academic Press, New York, 1967)C.R. Bell et al., Nucl. Sci. Eng. 53, 458–465 (1974)G. Bruno et al., Eur. Phys. J. C 79, 183 (2019)B.M. Dorofeev, V.I. Volkova, High Temp. 43, 620–627 (2005)L.D. Landau, E.M. Lifshitz, Fluid Mechanics. Course of Theoretical Physics, vol 6, 2nd edn. (Butterworth-Heinemann, Kidlington, Oxford, 1987)Y.Y. Sun, B.T. Chu, R.E. Apfel, J. Comp. Phys. 103, 126–140 (1992)M.S. Plesset, S.A. Zwick, J. Appl. Phys. 25, 493–500 (1954)L.E. Scriven, Chem. Eng. Sci. 10, 1–13 (1959)H.S. Lee, H. Merte, Int. J. Heat Mass Transf. 39, 2427–2447 (1996)A.J. Robinson, R.L. Judd, Int. J. Heat Mass Transf. 47, 5101–5113 (2004)F. d’Errico, Rad. Prot. Dos. 84, 55–62 (1999)B.B. Mikic, W.M. Rohsenow, P. Griffith, Int. J. Heat Mass Transf. 13, 657–666 (1970)P.J. Linstrom, W.G. Mallard (eds.) NIST Chemistry WebBook, NIST-SRD 69 (National Institute of Standards and Technology, Gaithersburg, MD). https://doi.org/10.18434/T4D303M. Barnabé-Heider et al., Nucl. Instr. Meth. Phys. Res. A 555, 184–204 (2005)D.V. Jordan et al., Appl. Rad. Isot. 63, 645–653 (2005

New dimensionless correlations for the evaluation of the thermal resistances of a district heating twin pipe system

The heat losses from pre-insulated double-pipe district heating (DH) systems buried in a homogeneous soil are studied numerically. The study is conducted using the diameter of the pipes and their distance, the size of the insulation, the thermal conductivity ratio between the insulation and the soil, as well as the burial depth of the double-pipe system, as controlling parameters. A computational code based on a control-volume formulation of the finite-difference method has been developed using the open-source framework OpenFOAM with the purpose to compute the heat transfer rate across adjacent solid regions with different thermophysical properties. The main scopes of the study are: (a) to investigate in what measure the geometry and the relative position of the warm and cold pipes, as well as the temperature imbalance, the burial depth and the physical properties of both the insulation and the soil, affect the heat losses; (b) to analyze the existence of an optimal configuration of the DH system by the thermal resistance enhancement viewpoint; and (c) to develop accurate correlating equations for the evaluation of the thermal resistance existing between each pipe and its surroundings, useful for practical thermal engineering applications

Dimensionless correlations for natural convection heat transfer from an enclosed horizontal heated plate

Natural convection from a horizontal plate with identically heated top and bottom sides, enclosed in gas- or liquid-filled square cavities cooled at sides, is studied numerically. A computational code based on the SIMPLE-C algorithm for pressure-velocity coupling is used to solve the system of the governing conservation equations of mass, momentum and energy. Simulations are performed using the Rayleigh number based on the plate length, the Prandtl number, the cavity width normalized by the plate length and the distance of the plate from the bottom wall of the enclosure normalized by the cavity width, as controlling parameters. It is found that the heat transfer rate enhances as the Rayleigh number, the Prandtl number and the dimensionless size of the cavity are increased, while it deteriorates as the dimensionless elevation of the plate is increased. Additionally, the heating of the upper side of the plate has an almost imperceptible effect on the heat transfer rate at the lower side of the plate, whereas the amount of heat transferred from the upper side of the plate normally decreases when the lower side of the plate is heated rather than being insulated. Based on the results obtained, suitable dimensionless heat transfer correlations are developed for the entire plate and each heated side

Effective exploitation of a geyser bubble-chamber equipment as a background-free fast neutron detector

MOSCAB equipment, a geyser-concept bubble-chamber originally thought for the search of dark matter in the form of WIMPs, is employed for the detection of fast neutrons. Once the background-free operating conditions are determined such that the detector is sensitive only to neutrons, which occurs when the neutron energy threshold required for nucleation is higher than approximately 2.5 MeV, the detector response to fast neutrons is investigated using an AmBe neutron source. Sets of detection efficiency functions are then produced via Monte Carlo simulations and post-processing, their validation being performed experimentally and discussed. Finally, the use of the detector to measure the fast neutron activity of very weak n-sources in clean environments, as well as to monitor the cosmic ray variations through the neutron component of the Extensive Air Showers, is considered.Comment: 16 pages, 10 figures, submitted to EPJ

Buoyancy-Induced Convection in Water From a Pair of Horizontal Heated Cylinders Enclosed in a Square Cooled Cavity

Buoyancy-driven convention from a pair of horizontal heated cylinders, set side by side inside a square cooled cavity filled with water, is studied numerically. The system of the conservation equations of mass, momentum and energy expressed in dimensionless form is solved through a control-volume formulation of the finite-difference method. The pressure-velocity coupling is handled using the SIMPLE-C algorithm. Numerical simulations are executed for different values of the Rayleigh number based on the cylinder diameter, as well as the width of the cavity, the inter-cylinder spacing and the distance of the cylinders from the bottom wall of the cavity normalized by the cylinder diameter. Two heat and fluid flow configurations are generally found to establish inside the cavity, according as the cylinders are located at close distance or at such a distance that the effects of the lateral walls of the cavity become important, each of these configurations being distinguished by the existence of an optimum inter-cylinder spacing which maximizes the overall heat transfer rate. Moreover, when the inter-cylinder spacing is such that the cylinders are located sufficiently close to the cavity sides, a periodic flow arises

Measurement of fast neutron background in the Gran Sasso underground laboratory using a geyser-concept bubble-chamber

Abstract A measurement of the fast neutron background in the Gran Sasso underground laboratory has been performed by the MOSCAB thermodynamic bubble chamber, a neutron detector which identifies fast neutrons passing through the metastable fluid by scattering ions. The result of this measurement confirms the results previously obtained using detectors based on totally different techniques, thus corroborating the previous results in terms of both integral intensity and spectral characteristics, at least in the energy region where the current measurement technique is sensitive

The multifaceted HR-role : A study about HR Practitionersexperience of the work situation

Det moderna arbetslivet genomgår snabba och stora förändringar och ändrar  örutsättningarna för många yrkesgrupper i hur arbetet ska bedrivas på bästa och mest effektiva sätt. Detta får konsekvenser för olika yrkesgruppers arbetssituationer. En yrkesgrupp som inte har fått ett allt för nämnvärt fokus i forskningen kring förändrade arbetssituationer är HR-medarbetare. Syftet med den här studien är att öka förståelsen för hur HR-medarbetare upplever och hanterar sin arbetssituation utifrån arbetskrav och arbetsresurser. Tre frågeställningar har utformats för att omfamna och konkretisera syftet ytterligare. Studien baseras på fem utvalda respondenter, som arbetar som HR-generalister eller HR Business Partners. Studien har genomförts med en kvalitativ forskningsmetod i form av intervjuer och har utgått från en abduktiv ansats. Studien påvisar att det finns olika uppfattningar mellan HR-medarbetare om vilka resurser som anses viktiga i arbetet. Studien har även visat på att HR-medarbetare ställs inför höga arbetskrav i form av framför allt hög arbetsbelastning och stora rollkonflikter. Resultatet  visar att HR-medarbetarna vanligtvis hanterar svåra arbetssituationer genom problemfokuserade hanteringsstrategier.The modern working life is going through big and rapid changes, which change the prerequisites for a lot of professions in how work should be conducted and utilized in best manners. This leads to consequences in the work situation for different professions. One profession that hasn’t a cquired a lot of focus in the research about changing work situations, is the HR Practitioners. The aim of this study is to increase the understanding in how HR Practitioners experience and manage their work situation from the basis of work demands and work resources. Three research questions have further been formed, with the aim to embrace and concrete the purpose of the study. The study is based on five selected candidates, who works as HR Generalists or HR Business Partners. The study has been conducted with a qualitative research method in the form of interviews and an abductive approach. The study demonstrates different opinions among the HR Practitioners about which kind of work resources that is considered most important at work. Results also show that HR Practitioners faces high work demands, mostly in the form of high work load and big role conflicts. Finally, the results show that HR Practitioners mostly apprehend and manage the severe work situations they face with a problem focused coping strategy