Helmholtz-Zentrum Dresden-Rossendorf Research Articles

Production of Medical Radionuclides in the Center for Radiopharmaceutical Tumor Research—A Status Report

A new Center for Radiopharmaceutical Cancer Research was established at the Helmholtz-Zentrum Dresden-Rossendorf in 2017 to centralize radionuclide and radiopharmaceutical production, as well as enable chemical and biochemical research. Routine production of several radionuclides was put into operation in recent years. We report on the production methods of radiopharmaceutical radionuclides, in particular 11C, 18F, and radio metals like 61Cu, 64Cu, 67Cu, 67Ga, 131Ba, and 133La that are used regularly. In the discussion, we report typical irradiation parameters and achieved saturation yields.

Модель реактора ВВЕР-1000 у прецизійному коді SERPENT 2 для розрахунку розподілу енерговиділення в активній зоні

A VVER-1000 reactor model using the Monte Carlo Serpent 2 code for core power distribution calculation is presented. The core and zones located near to the core were modeled in detail, without simplification. The assembly power distribution and axial power profiles were calculated for fresh core of the X2 VVER-1000 benchmark, namely the core of the KhNPP2 first loading for the hot zero power. The results were compared with the data obtained by specialists from Helmholtz-Zentrum Dresden-Rossendorf.

Vibrations Analysis of Bubble Evolution in Liquids of Varying Physical Properties

In recent years there is an attempt to control the gas stirring intensity in metal-making ladles with the aid of vibration measurements. Understanding better the induced vibrations in two-phase flows can substantially improve the existing models for gas stirring control. In this work, highly sensitive accelerometers were used for the vibration measurements in a liquid metal alloy; Sn–40 wt pctBi alloy at 200 °C and water at 20 °C. The examination of the liquids was conducted in the ladle mockup integrated into the Liquid Metal Model for Steel Casting facility at Helmholtz-Zentrum Dresden Rossendorf. Single bubbles were generated in the respective liquids by controlled argon injection at low flow rates in the range of 0.01 to 0.15 NL min−1 through a single nozzle installed at the bottom of the ladle. Obtained results demonstrate differences between the induced vibrations in the examined liquids in terms of the magnitude of the root mean square values of vibration amplitude and the shape of the resulting curves with increasing flow rate. Furthermore, continuous wavelet transform reveals variations in the duration and vibrational frequency of the evolved bubble phenomena. The findings suggest that differences in the physical properties of the examined liquids result in variations in the vibrations induced during bubble evolution.

Background studies and normalization of signal events in the Mu2e experiment

The Mu2e experiment is currently being constructed at Fermilab to search for the neutrino-less conversion of negative muons into electrons in the field of an aluminum nucleus. The experiment aims at a sensitivity of four orders of magnitude higher than previous related experiments, which implies highly demanding accuracy requirements both in the design and during the operation. To achieve such a goal, two important tasks should be accomplished. First, it is essential to estimate precisely the particle yields and all the backgrounds that could mimic the monoenergetic conversion electron signal. Second, it is necessary to normalize the signal events accurately. The normalization of the signal events is planned to be done using a detector system made of an HPGe detector and a Lanthanum Bromide detector, which will measure the rate of muons stopped on the aluminum target by looking at the emitted characteristic X-and γ-rays of energies up to 1809 keV. Therefore, it is essential to evaluate the detector system's performance before the start of the actual experiment. In this study, the first task was addressed by an extensive campaign of Monte Carlo simulations to investigate the relevant parameters and their impact on the experiment's sensitivity. The second task was handled by taking advantage of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) pulsed Bremsstrahlung photon beam at the ELBE facility. The detector system was tested at the ELBE facility under timing and background conditions similar to the ones expected at the Mu2e experiment. The study presents and discusses the simulation results and the detector system testing campaign.

Overarching Data Management Ecosystem at HZDR

When dealing with research data management, researchers at Helmholtz- Zentrum Dresden – Rossendorf (HZDR) face a variety of systems and tools. These range from the project planning phase (proposal management, data management plans and policies), over documentation during the experiment or simulation campaign, to the publication (collaborative authoring tools, metadata catalogs, publication systems, data repositories). In addition, modern research projects usually are required to interact with a variety of software stacks and workflow management systems to allow comprehensi- ble and FAIR science on the underlying IT infrastructure (HPC, data storage, network file systems, archival). This article first demonstrates the data management systems and services provided at HZDR, followed by an overview of a self-developed guidance system. It is concluded by a real-world example.

Photo-response of the N=Z nucleus ^{24}Mg

The electric E1 and magnetic M1 dipole responses of the N=Z nucleus ^{24}Mg were investigated in an inelastic photon scattering experiment. The 13.0 MeV electrons, which were used to produce the unpolarised bremsstrahlung in the entrance channel of the ^{24}Mg(gamma ,gamma ^{prime }) reaction, were delivered by the ELBE accelerator of the Helmholtz-Zentrum Dresden-Rossendorf. The collimated bremsstrahlung photons excited one J^{pi }=1^-, four J^{pi }=1^+, and six J^{pi }=2^+ states in ^{24}Mg. De-excitation gamma rays were detected using the four high-purity germanium detectors of the gamma ELBE setup, which is dedicated to nuclear resonance fluorescence experiments. In the energy region up to 13.0 MeV a total B(M1)uparrow = 2.7(3)~mu _N^2 is observed, but this N=Z nucleus exhibits only marginal E1 strength of less than sum B(E1)uparrow le 0.61 times 10^{-3} e^2 , fm^2. The B(varPi 1, 1^{pi }_i rightarrow 2^+_1)/B(varPi 1, 1^{pi }_i rightarrow 0^+_{gs}) branching ratios in combination with the expected results from the Alaga rules demonstrate that K is a good approximative quantum number for ^{24}Mg. The use of the known rho ^2(E0, 0^+_2 rightarrow 0^+_{gs}) strength and the measured B(M1, 1^+ rightarrow 0^+_2)/B(M1, 1^+ rightarrow 0^+_{gs}) branching ratio of the 10.712 MeV 1^+ level allows, in a two-state mixing model, an extraction of the difference varDelta beta _2^2 between the prolate ground-state structure and shape-coexisting superdeformed structure built upon the 6432-keV 0^+_2 level.

Verification & validation of CFD predictions regarding pressurized thermal shock (PTS) situations in ROCOM installation: Comparison with IAEA benchmark

The current paper documents the Computational Fluid Dynamics (CFD) code validation activity, carried out at the Nuclear Research Center of Birine relevant of Atomic Energy Commission of Algeria as part of International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP): Application of Computational Fluid Dynamics Codes for Nuclear Power Plant Design to assess the current capabilities of these codes and to contribute to technological progress in their verification and validation. A set of ROCOM CFD-grade test data of Pressurized Thermal Shock test (PTS) specifications was made available in the framework of this (CRP) by Helmholtz Zentrum Dresden-Rossendorf, (HZDR) Germany, to perform detailed calculations of the proposed test. The reference point is the injection of relatively cold core cooling water (ECC), which can induce buoyant stratification. The data obtained from the PTS experiment were compared with the results of Ansys-CFX calculations in this paper. Unsteady Reynolds-Averaged Navier-Stokes (URANS) model is used to examine the buoyancy-influenced flows in the reactor pressure vessel for condition where natural circulation is a dominant factor. The Shear Stress Transport (SST k-ω) turbulence model is used to take into account the turbulence effects on the mean flow. Calculation results show a good qualitative and quantitative agreement with the experiment data.

Generation of Optimal Weight Values Based on the Recursive Monte Carlo Method for Use in Monte Carlo Deep Penetration Calculations

In nuclear engineering, Monte Carlo (MC) methods are commonly used for reactor analysis and radiation shielding problems. These methods are capable of dealing with both simple and complex system models with accuracy. The application of MC methods experiences challenges when dealing with the deep penetration problems that are typically encountered in radiation shielding cases. It is difficult to produce statistically reliable results due to poor particle sampling in the region of interest. Therefore, such calculations are performed by the Monte Carlo N-Particle Transport (MCNP) code in association with the weight window (WW) variance reduction technique, which increases the particle statistics in the desired tally region. However, for large problems, MCNP’s built-in weight window generator (WWG) produces zero WW parameters for tally regions located far from the source. To address this issue, the recursive Monte Carlo (RMC) method was proposed. This paper focuses on the RMC methodology and its implementation in the Helmholtz-Zentrum Dresden-Rossendorf’s (HZDR’s) in-house code TRAWEI, which is responsible for producing optimal zone weight parameters used for optimizing deep penetration MC calculations. In addition, this paper discusses the verification of the TRAWEI weight generator program to that of an existing MCNP WWG. The performance of TRAWEI-generated weight values is assessed using a handful of test cases involving two shield materials. Globally, the TRAWEI-generated weight values improved not only the statistical variance and computational efficiency of the MC run compared to the analog MCNP simulation but also those of the simulation with WW values generated by the standard MCNP WWG.

Impact of Submerged Entry Nozzle (SEN) Immersion Depth on Meniscus Flow in Continuous Casting Mold under Electromagnetic Brake (EMBr)

Complex multi-phase phenomena, including turbulent flow, solidification, and magnetohydrodynamics (MHD) forces, occur during the continuous casting (CC) under the applied electromagnetic brake (EMBr). The results of the small-scale experiment of the liquid metal model for continuous casting (mini-LIMMCAST) at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), investigating MHD flow with a deep immersion depth of 100 mm, are supplemented by newly presented numerical studies with the shallow position of the submerged entry nozzle (SEN) at 50 mm below the meniscus. Herein, the focus is on the MHD effects at the meniscus level considering (i) a fully insulating domain boundary, (ii) a perfectly conductive mold, or (iii) the presence of the solid shell. The volume-of-fluid (VOF) approach is utilized to model a Galinstan flow, including free surface behavior. A multiphase solver is developed using conservative MHD formulations in the framework of the open-source computational fluid dynamics (CFD) package OpenFOAM®. The wall-adapting local eddy-viscosity (WALE) subgrid-scale (SGS) model is employed to model the turbulent effects on the free surface flow. We found that, for the deep immersion depth, the meniscus remains calm under the EMBr for the conductive and semi-conductive domain. For the insulated mold disregarding the SEN position, the self-inducing MHD vortices, aligned with the magnetic field, cause strong waving of the meniscus and air bubble entrapment for shallow immersion depth. Secondary MHD structures can form close to the meniscus under specific conditions. The influence of the EMBr and immersion depth on the flow energy characteristics is analyzed using power spectral density (PSD).

Resonance region evaluation of 16O for criticality safety and reactor applications

The intent of this paper is to present the resolved resonance evaluation of 16O in the energy range from thermal to 6 MeV. The newness of the present work is that recent cross-section data for the 16O(n,α) 13C reaction taken at the GELINA time-of-flight facility and transmission data obtained at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR ) were included in the evaluation. The evaluation was carried out with the SAMMY code. The evaluation was used to calculate critical benchmark experiment sensitive to the 16O cross sections.

OpenFOAM-Hybrid: A Morphology Adaptive Multifield Two-Fluid Model

Industrial multiphase flows are typically characterized by coexisting morphologies. Modern simulation methods are well established for dispersed [e.g., Euler-Euler (E-E)] or resolved [e.g., volume-of-fluid (VOF)] interfacial structures. Hence, a morphology adaptive multifield two-fluid model is proposed that is able to handle dispersed and resolved interfacial structures coexisting in the computational domain with the same set of equations. An interfacial drag formulation for large interfacial structures is used to describe them in a VOF-like manner. For the dispersed structures, the baseline model developed at Helmholtz-Zentrum Dresden-Rossendorf is applied. The functionality of the framework is demonstrated by investigating a single rising gas bubble in a stagnant water column, a two-dimensional stagnant stratification of water and oil sharing a large-scale interface that is penetrated by micro gas bubbles, and an isothermal countercurrent stratified flow case. Recent developments focus on the transition region, where bubbles are overresolved or underresolved either for E-E or for VOF. Furthermore, a concept is presented for the transition of oversized dispersed bubbles into the resolved phase.

Numerical investigation of the flow inside a precession-driven cylindrical cavity with additional baffles using an immersed boundary method

In this paper, we present a numerical approach to solve the Navier–Stokes equations for arbitrary vessel geometries by combining a Fourier-spectral method with a direct-forcing immersed boundary method, which one allows to consider solid–fluid interactions. The approach is applied to a paradigmatic setup motivated by the precession dynamo experiment currently under construction at Helmholtz–Zentrum Dresden–Rossendorf. The experiment consists of a fluid-filled cylinder rotating about two axes, which induces a precession-driven flow inside the cavity. The cylinder is also equipped with baffles at the end caps with adjustable penetration depth to impact the flow. The numerical details and simulation results for the spin-up and precession-driven flow in a circular cylinder with additional baffles are presented. The results provide a first confirmation that the use of such baffles in the precession dynamo experiment is a useful way of influencing the flow, allowing more efficient driving without changing the known flow structure too much.

Beam pulse structure and dose rate as determinants for the flash effect observed in zebrafish embryo

Background and purposeContinuing recent experiments at the research electron accelerator ELBE at the Helmholtz-Zentrum Dresden-Rossendorf the influence of beam pulse structure on the Flash effect was investigated. Materials and methodsThe proton beam pulse structure of an isochronous cyclotron (UHDRiso) and a synchrocyclotron (UHDRsynchro) was mimicked at ELBE by quasi-continuous electron bunches at 13 MHz delivering mean dose rates of 287 Gy/s and 177 Gy/s and bunch dose rates of 106Gy/s and 109 Gy/s, respectively. For UHDRsynchro, 40 ms macro pulses at a frequency of 25 Hz superimposed the bunch delivery. For comparison, a maximum beam intensity (2.5 × 105 Gy/s mean and ∼109 Gy/s bunch dose rate) and a reference irradiation (of ∼8 Gy/min mean dose rate) were applied. Radiation induced changes were assessed in zebrafish embryos over four days post irradiation. ResultsRelative to the reference a significant protecting Flash effect was observed for all electron beam pulse regimes with less severe damage the higher the mean dose rate of the electron beam. Accordingly, the macro pulsing induced prolongation of treatment time at UHDRsynchro regime reduces the protecting effect compared to the maximum regime delivered at same bunch but higher mean dose rate. The Flash effect of the UHDRiso regime was confirmed at a clinical isochronous cyclotron comparing the damage induced by proton beams delivered at 300 Gy/s and ∼9 Gy/min. ConclusionThe recent findings indicate that the mean dose rate or treatment time are decisive for the normal tissue protecting Flash effect in zebrafish embryo.

Laboratory Investigation of Tomography-Controlled Continuous Steel Casting.

More than 96% of steel in the world is produced via the method of continuous casting. The flow condition in the mould, where the initial solidification occurs, has a significant impact on the quality of steel products. It is important to have timely, and perhaps automated, control of the flow during casting. This work presents a new concept of using contactless inductive flow tomography (CIFT) as a sensor for a novel controller, which alters the strength of an electromagnetic brake (EMBr) of ruler type based on the reconstructed flow structure in the mould. The method was developed for the small-scale Liquid Metal Model for Continuous Casting (mini-LIMMCAST) facility available at the Helmholtz-Zentrum Dresden-Rossendorf. As an example of an undesired flow condition, clogging of the submerged entry nozzle (SEN) was modelled by partly closing one of the side ports of the SEN; in combination with an active EMBr, the jet penetrates deeper into the mould than when the EMBr is switched off. Corresponding flow patterns are detected by extracting the impingement position of the jets at the narrow faces of the mould from the CIFT reconstruction. The controller is designed to detect to undesired flow condition and switch off the EMBr. The temporal resolution of CIFT is 0.5 s.

How 5 f Electron Polarisability Drives Covalency and Selectivity in Actinide N-Donor Complexes.

Invited for the cover of this issue is the group of Moritz Schmidt at the Helmholtz-Zentrum Dresden-Rossendorf. The image depicts the relative strength of bonds from an actinide to a pyrrole-based ligand in comparison with the salen ligand. Read the full text of the article at 10.1002/chem.202102849.

Intermittent chaotic flows in the weakly magnetised spherical Couette system

AbstractExperiments on the magnetised spherical Couette system are presently being carried out at Helmholtz‐Zentrum Dresden‐Rossendorf (HZDR). A liquid metal (GaInSn) is confined within two differentially rotating spheres and exposed to a magnetic field parallel to the axis of rotation. Intermittent chaotic flows, corresponding to the radial jet instability, are described. The relation of these chaotic flows with unstable regular (periodic and quasiperiodic) solutions obtained at the same range of parameters is investigated.

A new system for real-time data acquisition and pulse parameterization for digital positron annihilation lifetime spectrometers with high repetition rates

We present a new system for high repetition rate and real-time pulse analysis implemented at the Monoenergetic Positron Source (MePS) at the superconducting electron LINAC ELBE at Helmholtz-Zentrum Dresden-Rossendorf. Dedicated digital signal processing and optimized algorithms are employed allowing for high bandwidth throughput, online pulse analysis and filtering. Positrons generated from radioisotopes and from bremsstrahlung pair production by means of highly intense accelerator-based positron beams serve as a microstructure probe allowing material characterizations with respect to chemical, mechanical, electrical, and magnetic properties. Positron annihilation lifetime events with up to 13 MHz repetition rate are being processed online without losses while performing signal selections for pile-up reduction, online energy calibration, and — for radioisotope-based measurements — identification of start and stop events.

Generation of Reverse Meniscus Flow by Applying An Electromagnetic Brake

A numerical study is presented that deals with the flow in the mold of a continuous slab caster under the influence of a DC magnetic field (electromagnetic brakes (EMBrs)). The arrangement and geometry investigated here is based on a series of previous experimental studies carried out at the mini-LIMMCAST facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The magnetic field models a ruler-type EMBr and is installed in the region of the ports of the submerged entry nozzle (SEN). The current article considers magnet field strengths up to 441 mT, corresponding to a Hartmann number of about 600, and takes the electrical conductivity of the solidified shell into account. The numerical model of the turbulent flow under the applied magnetic field is implemented using the open-source CFD package OpenFOAM®. Our numerical results reveal that a growing magnitude of the applied magnetic field may cause a reversal of the flow direction at the meniscus surface, which is related the formation of a “multiroll” flow pattern in the mold. This phenomenon can be explained as a classical magnetohydrodynamics (MHD) effect: (1) the closure of the induced electric current results not primarily in a braking Lorentz force inside the jet but in an acceleration in regions of previously weak velocities, which initiates the formation of an opposite vortex (OV) close to the mean jet; (2) this vortex develops in size at the expense of the main vortex until it reaches the meniscus surface, where it becomes clearly visible. We also show that an acceleration of the meniscus flow must be expected when the applied magnetic field is smaller than a critical value. This acceleration is due to the transfer of kinetic energy from smaller turbulent structures into the mean flow. A further increase in the EMBr intensity leads to the expected damping of the mean flow and, consequently, to a reduction in the size of the upper roll. These investigations show that the Lorentz force cannot be reduced to a simple damping effect; depending on the field strength, its action is found to be topologically complex.

A tunable autocorrelator for pulse measurements at IR FEL-oscillator facilities

Radiation characteristics of a Free-Electron Laser (FEL) such as pulse length, time structure, intensity, bandwidth, wavelength, power, frequency, etc., which were measured on a diagnostics table, are thoroughly discussed. In this respect, pulse length measurements of an Infrared FEL (IR-FEL) beam are evaluated through an intensity autocorrelator, designed and installed as a diagnostics tool at the “Helmholtz-Zentrum Dresden-Rossendorf (HZDR)-Radiation Source ELBE” of Germany. In addition, the autocorrelator was designed as a unique, cost-effective, and in-house setup. It operates within the wavelength range of 3–35 microns, using Cadmium-Telluride (CdTe) crystals in the Second Harmonic Generation (SHG) medium. The intensity autocorrelation curves were obtained for the FEL beam with the wavelength of 26.2 microns, indicating an FWHM pulse duration ranging between 3.29–8.03 ps with different optical cavity detuning values. Furthermore, the pulse duration of Ti: sapphire laser beam is measured between 1–3 ps through the designed autocorrelator at the ELBE light source. On the other hand, the setup may pave the way for pulse length measurements of the Turkish infrared FEL-oscillator facility (TARLA) as well, which is currently under the hardware installation phase. Finally, it is elaborated in section 3 that the unique autocorrelator design fully meets all requirements for pulse length measurements of an infrared FEL source.

Benchmarking of computational fluid dynamic models for bubbly flows

Eulerian-Eulerian computational fluid dynamic (CFD) models allow the prediction of complex and large-scale industrial multiphase gas–liquid bubbly flows with a relatively limited computational load. However, the interfacial transfer processes are entirely modelled, with closure relations that often dictate the accuracy of the entire model. Numerous sets of closures have been developed, often optimized over few experimental data sets and achieving remarkable accuracy that, however, becomes difficult to replicate outside of the range of the selected data. This makes a reliable comparison of available model capabilities difficult and obstructs their further development. In this paper, the CFD models developed at the University of Leeds and the Helmholtz-Zentrum Dresden-Rossendorf are benchmarked against a large database of bubbly flows in vertical pipes. The research groups adopt a similar modelling strategy, aimed at identifying a single universal set of widely applicable closures. The main focus of the paper is interfacial momentum transfer, which essentially governs the void fraction distribution in the flow, and turbulence modelling closures. To focus on these aspects, the validation database is limited to experiments with a monodispersed bubble diameter distribution. Overall, the models prove to be reliable and robust and can be applied with confidence over the range of parameters tested. Areas are identified where further development is needed, such as the modelling of bubble-induced turbulence and the near-wall region, as well as the best features of both models to be combined in a future harmonized model. A benchmark is also established and is available for the testing of other models. Similar exercises are encouraged to support the confident application of multiphase CFD models, together with the definition of a set of experiments accepted community-wide for model benchmarking.