Horia Hulubei Research Articles

Discovery of Astatine by Horia Hulubei

The search for new chemical elements was a prominent scientific endeavor in the late 19th and early 20th centuries. This era saw the discovery of several elements such as radium, polonium, and radon by prominent scientists such as Marie Curie and Ernest Rutherford. Astatine was one of the missing elements from the periodic table, and its existence was predicted due to the periodicity of the elements, with iodine as its nearest stable neighbor. Scientists have sought to confirm its existence and properties. The discovery of astatine by Horia Hulubei and his collaborator Yvette Cauchois at the beginning of the 20th century is recognized by many scientists, although the authorship of this discovery was ignored by the Austrian radiochemist Friedrich Paneth, who was responsible for setting priorities in the discovery of new chemical elements. This article will delve into the historical background and scientific endeavors that led to the discovery of astatine by Horia Hulubei.

Probing deformed nuclei: Experimental insights into excited states of 152,153,154Gd isotopes through fusion-evaporation reactions

The rare-earth region has been the focus of various studies aiming at the understanding of nuclear structure and providing information on the details of the reaction mechanism. The Gd isotopes belong to this group of nuclei and despite the available spectroscopic information, several open questions about their structure still exist, such as the inter-band transitions related to shape evolution or branching-ratios in deformed states. In addition, production cross sections of different reactions to Gd isotopes are largely unknown.In this work, we report on an experimental attempt to populate the excited states in the isotopes 152,153,154Gd by employing the heavy-ion fusion reaction 18O+138Ba → 156-xGd + xn in the 58-64 MeV energy range (center-of-mass). The experiment was conducted at the 9 MV FV Pelletron Tandem at the Horia Hulubei National Institute for Physics and Nuclear Engineering, employing the ROSPHERE array. Several branching-ratios for energy levels in 152,153Gd have been measured, offering new and updated values. Furthermore, relative cross sections regarding the fusion-evaporation reactions 138Ba(18O, 4n)152Gd, 138Ba(18O, 3n)153Gd, and 138Ba(18O, 2n)154Gd have been measured and compared with theoretical calculations with PACE4.

A setup for high-energy [formula omitted]-ray spectroscopy with the ELI-NP large-volume LaBr3:Ce and CeBr3 detectors at the 9 MV Tandem accelerator at IFIN-HH

We have performed the first experimental campaign using large-volume LaBr3:Ce and CeBr3 detectors from several of the Extreme Light Infrastructure-Nuclear physics (ELI-NP) instrumental setups together with detectors and infrastructure from the ROSPHERE array at the 9 MV Tandem facility at the Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH). The performance of the detectors and the digital data acquisition system is shown to give a good energy resolution at high energies, and an excellent time resolution. We, furthermore, present the possibilities to integrate the detector system and the digital electronics with various ancillary detectors for, for example, charged particles.

Gamma spectroscopy of even-even Ytterbium isotopes

The even-even Ytterbium isotopes lack spectroscopic information with the increase of the neutron number and they are well deformed nuclei, presenting rotational properties. In this mass region of the nuclear chart predictions have shown rare phenomena related to nuclear structure, such as shape coexistence. In this work the population of excited states were investigated in the even-even Yb isotopes via the 2n-transfer reaction 168-174Yb (18O, 16O) 170-176Yb. The measurements were carried out at the 9 MV Tandem accelerator at the Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH) in Romania. The deduced gamma-ray angular distributions in the ground state bands are found to correspond with transitions, as expected

Quantification of 239Pu radioactivity in swipe samples by accelerator mass spectrometry

In the AMS Laboratory at the Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH) in Bucharest, Romania plutonium measurements started a few years ago. In the course of this period, we chemically processed environmental samples that could have contaminated the laboratory with 239Pu in the femtogram range. Swipe samples taken in the sample processing laboratory were investigated to quantify the potential plutonium contamination. Following the accelerator mass spectrometry measurements, the limit of detection for 239Pu in the order of 1 fg was determined, while the amount of 239Pu in the swipe samples was around 2 fg. The chemical procedure and the AMS measurement were validated by analyzing simulated swipe samples as a part of a proficiency test organized by the International Atomic Energy Agency. The obtained results show that the 1MV AMS system at IFIN-HH can be routinely used for determination of 239Pu concentrations in environmental matrices.

On the multipole mixing ratio of the 1066 keV transition from the 0.52 μs isomer of 180Hf

The nucleus 180Hf is one of the most primary examples of an axially symmetric prolate rotor. Combined with the presence of high-K isomers, spectroscopic studies can provide important information on the nature of its single-particle levels. Precise measurements are essential for constraining nuclear models and interpreting the nature of such isomeric states. In this work, the nucleus 180Hf was populated using the proton pick-up reaction 181Ta(11B,12C)180Hf at beam energy of 47 MeV at Horia Hulubei National Institute of Nuclear Physics and Engineering (IFIN-HH). The spin of the 1374 keV state and the mixing ratio of the 1066 keV transition have been measured, the latter with an increased precision compared to the previous value from literature. The presently measured spin of the 1374 keV state, currently assigned a tentative value of (41−), favors one of the two different values that were previously reported. The particular state constitutes the band-head of a rotational band in 180Hf. The measured multipolarity mixing ratio of the inter-band transition 1374→309 keV can provide important information for the testing and constraining of theoretical nuclear models used for the study of the intrinsic properties of 180Hf, as well as its neighboring isotopes.

DETERMINATION OF POTENTIAL AREAS OF INFLUENCE ON THE ROMANIAN TERRITORY OF UKRAINIAN NUCLEAR POWER PLANTS IN THE CONTEXT OF THE CRISIS GENERATED BY THE RUSSIAN-UKRAINIAN CONFLICT

In the context of the crisis generated by the Russian-Ukrainian conflict, radiological situation forecasts were made within the National Institute of Research and Development for Physics and Nuclear Engineering "Horia Hulubei" (IFIN-HH) for all nuclear power plants in Ukraine. Therefore, the resident decision support software systems for radiological and nuclear emergencies were used, with the main purpose of identifying potential areas of influence on the territory of Romania generated by Ukrainian power plants, as consequence of military actions. In the absence of pertinent and confirmed information, two hypothetical scenarios were considered by which the radioactive material could be dispersed into the atmosphere, for which appropriate accident source terms were built, using methods validated and approved by the international organizations in the field. The monitoring of the radiological situation of the Ukrainian nuclear power plants was carried out over a period of several months starting from the first day of the conflict outbreak. In the paper are presented comparative results obtained with two software systems for a representative case at the Zaporozhe Nuclear Power Plant, the largest nuclear power plant in Europe, situated in the center of several disputes.

New setup for basic radiobiology studies using a 3 MV TandetronTM: Design and developments

The aim of the study was to upgrade the Horia Hulubei National Institute for Physics and Nuclear Engineering existing facility - a 3 MV TandetronTM accelerator - to be used in radiobiology experiments. Irradiations were performed with 1.95 MeV protons (beam with uniform distribution over a 30 mm2). Particle fluence was determined with plastic track detectors and live monitored using Rutherford Backscattering Spectrometry technique. Absolute and relative dose (Advanced Markus ion chamber) and the lateral quality of the irradiation spot (radiochromic film) were measured. The dosimetric measurements were confirmed by Geant4 simulations of the dose averaged Linear Energy Transfer, the Bragg peak profile and the beam lateral energy distribution. A complete setup for exposing in vitro cell cultures to the particle beams was constructed from scratch. Preliminary data of survival rate of V79 fibroblast cells are reported. The obtained results are similarly with data reported using other proton beam facilities.

Preliminary results on neutrons TOF experiment using the Neutron Array

We have refurbished and tested a neutron array composed of 81 BC400 plastic scintillator detectors dedicated for neutron measurements in future fusion–fission experiments The Neutron Array (NA) detectors, installed at the 9 MV Tandem accelerator facility of the Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH), have been refurbished and the data acquisition system has been updated. We present the characteristics and performances of the NA and of the associated electronics.

Tracking and Monitoring of the Alignment System Used for Nuclear Physics Experiments

The ELI-NP (Extreme Light Intensity—Nuclear Physics) project, developed at the Horia Hulubei National Institute for RD in Physics and Nuclear Engineering (IFIN-HH), has included one component dedicated to the study of interactions between brilliant gamma-ray and matter, with applications in nuclear physics and the science of materials. The paper is focused on the interaction chamber, an important part of the facility which hosts the experiment’s samples. The interaction chamber is endowed with a mobile sample support (holder), which automatically tracks the γ-ray beam. The γ-ray radiation source presents a slight variation of the direction of the emitted radiation in time. The built system ensures the permanent collimation between the γ-ray beam and the sample that is being investigated. This is done with two electric motors, which have a symmetrical movement with respect to the center of a rectangle. The specific measures taken by the design and implementation that permit to reach performances of tracking system are emphasized in the paper. The methodology considers the relative displacement between the detectors with which the laboratory is equipped and the absolute position in space of the sample boundary. The control of this motion is designed to respect the symmetry of the system. Both facets of the project (hardware and software) are detailed, emphasizing the way in which the designers ensured compliance with the system of real-time operation conditions of the tracking and monitoring system.

First in-beam experiment with the ELIADE detectors: a spectroscopic study of 130La

The new facility, Extreme Light Infrastructure – Nuclear Physics (ELI-NP), is a combined laser-gamma nuclear physics research facility currently undergoing its final implementation stages in Măgurele near Bucharest, Romania. It already hosts two fully-operational 10 PW laser arms and, by 2023, it will also house a γ-beam system based on laser Compton backscattering, capable of delivering a high-brilliance, low-energy beam at E γ ≲ 19.5 MeV. Owing to this unique laser-gamma instrumentation combination, several types of experiments will be possible at ELI-NP, including high precision nuclear resonance fluorescence (NRF) experiments. In this case, the main γ-beam detection system for performing NRF studies at ELI-NP is represented by the ELI Array of DEtectors (ELIADE), featuring eight high-purity germanium (HPGe) segmented clover detectors. The current work presents the characteristics of two of the ELIADE detectors, including their photopeak detection efficiency, energy resolution, and peak-to-total ratio measured using γ-ray sources, as well as the timing performance obtained via in-beam measurements. For these latter detector tests, 130La was populated via the fusion evaporation reaction 121Sb(12C,3n)130La using a beam energy of 53 MeV at the Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH), also located in Măgurele. Herein, we report on the results of the ^130La linear polarization measurements taken using the ELIADE detectors as Compton polarimeters. The results obtained from the in-beam experiment were compared to several already published works and we present new information on the transition multipolarity in 130La.

MODELING OF DOSE RATES IN CASE OF A RADIOLOGICAL INCIDENT AT THE IFIN-HH INTERMEDIARY GRAPHITE STORAGE

The low and intermediate level activity wastes resulted from decommissioning of the VVR-S nuclear research reactor belonging to the “Horia Hulubei” National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH), are kept in an intermediary storage facility. The storage is located on the premises of the Institute near Bucharest, Romania and includes activated graphite from the reactor thermal column. In case of a very low probability hypothetical atmospheric radiological dispersal incident such as an unexpected fire, despite all the implemented safety measures, there is a certain radiological risk for the workers and general public due to potential ingestion or inhalation or contact with the radioactive aerosols released on a certain range from the storage building. For estimating the total gamma dose intake and adequate countermeasures for workers and public members, the JRODOS (Real-time On-line Decision Support) code system for off-site emergency management after nuclear accidents was used in the paper.

Characterization of a plutonium–beryllium neutron source

Here we present an investigation of a plutonium–beryllium neutron source available at the Horia Hulubei National Institute of Physics and Nuclear Engineering, Romania, to be used for detector characterization during the implementation of the Extreme Light Infrastructure – Nuclear Physics project. Using several different techniques and instruments, we have measured the isotopic composition for plutonium to be 75% 239Pu and 24% 240Pu, with a minor contribution from other isotopes. Furthermore, we have measured the source activity as of November 20th 2019 to be 2.220(5)×105 neutrons per second with a mean energy of 3.25(17) MeV. We have also measured both the γ-tagged and full neutron energy spectra, and discuss the origin of the observed structure in the neutron energies based on these. All these parameters are of importance both for traceability of nuclear material, radioprotection, and accurate detector characterization.

Nucleon inelastic scattering cross sections on O16 and Si28

This paper reports cross-section measurements of the ($n,{n}^{\ensuremath{'}}$) and ($p,{p}^{\ensuremath{'}}$) reactions on $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$ at Geel Electron Linear Accelerator and at the 9-MV Tandem Accelerator of Horia Hulubei National Institute for Physics and Nuclear Engineering, respectively. The main purpose was to measure the neutron- and proton-induced inelastic $\ensuremath{\gamma}$-production cross sections for all observed transitions in $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$, followed by the calculation of the corresponding total inelastic cross section. The results are compared with theoretical calculations performed using the talys 1.9 code, evaluated nuclear data, and previously reported experimental data. The broader goal of this work is to study whether and to what extent the neutron-induced inelastic cross sections of these nuclei can be inferred from those obtained using suitable charged particle reactions. We show that, by making use of the formal similarities between the neutron- and the proton-target optical model potentials and isospin symmetry in mirror nuclei, one can develop a procedure that combines experimental proton-induced inelastic cross sections with theoretical calculations to infer neutron inelastic cross sections. For $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$, the precision associated with this procedure is around 10--20% for most of the incident energy range.

Radiological Characterization of the Resulting Solid Materials from the Refurbishment of the Tritium Laboratory

The Tritium Laboratory at Horia Hulubei National Institute for Physics and Nuclear Engineering was initially licensed in 1976 and completely refurbished in 2011 as a unique isotope laboratory focused on tritium handling and processing to conduct a variety of scientific experiments. During laboratory renovation, different types of solid radioactive waste or potential waste contaminated with tritium were created: bricks, mortars, cements, false ceiling (polyvinyl chloride), linoleum, rubber, etc.In order to fulfill all the requirements of the license issued by the Romanian regulatory body, the characterization of the physical, chemical, and radiological properties of the waste, in order to establish the need for further treatment, conditioning, and for storage or disposal, was mandatory. The present work treats the development of a method for the determination of tritium activity in the solid waste according to the operation licensing framework. The measurement results, regarding the tritium-specific activity in different solid waste resulting from the renovation of the laboratory, are presented in this paper.

The Area Measurements in the Tritium Laboratory Within NIPNE Magurele

This paper reports the results of radiological measurements taken for the last 3 years in the controlled area and adjacent zone of the Tritium Laboratory of the the Horia Hulubei National Institute for Physics and Nuclear Engineering, Magurele. The radiological characterization has been performed by determination of total and removed tritium contamination for the following surfaces: pavement, walls, windows, radiochemical tables, radionuclide fume cupboards, glove boxes, and sinks. The fixed tritium contamination does not present representative radiological risk because beta particles emitted by tritium are unable to penetrate the skin. The removed tritium contamination represents that component of the total surface contamination that can be taken by mechanical processes. The removed contamination was analyzed as a priority because it represents the main radiological risk factor in tritium laboratories. The determination of surface contamination has been carried out by scanning of the analyzed surfaces using an LB 1230 UMo tritium surface monitor with an LB 1230 detector and by a smear test using extruded polystyrene smears followed by measurement of the removed activity with a liquid scintillation counter. The total surface contamination values, obtained by scanning, were below the detection limit of the equipment, except for radiochemical hood surfaces. The removed tritium contamination determined values are in the domain of 5 … 450 Bq/dm2. At the department level, the obtained values for surface tritium contamination are at the background level.

Alanine pellets comparison using EPR dosimetry in the frame of quality assurance for a Gamma Knife system in Romania

In the last decade, the use of alanine/Electronic Paramagnetic Resonance (EPR) system was extended to radiotherapy doses. In stereotactic radiosurgery, doses up to 70 Gy are delivered to the brain tumor preserving healthy tissues. This type of treatment is delivered using dedicated equipment, like Cyberknife or Gamma Knife. Alanine dosimeters are characterized by their small size (5 mm diameter) and by similarity with tissue. They are well adapted for this wide dose range for which the dosimeter response is linear, independent of dose rate and energy for the range around few MeV. Therefore Alanine/EPR system is a suitable method for accurate and stable dose measurements as passive dosimeters for narrow treatment beams, which makes it an excellent candidate for end to end testing of radiosurgery treatments using Gamma Knife. The present work describes the development of the alanine/EPR method at Horia Hulubei National Institute for Physics and Nuclear Engeneering (IFIN-HH) in Romania including the optimization of system parameters for the radiosurgery dose range in the frame of an IFIN-HH and the French national metrology institute Laboratoire National Henri Becquerel federated by the Laboratoire National de métrologie et d’Essais (LNE-LNHB) collaboration. Romanian alanine dose measurements capability is presented regarding a comparison of calibration curves between both National Laboratories using Bruker and Synergy Health alanine pellets.

Cercetări efectuate la Băile Figa în anii 2016–2019 și considerații privind deslușirea valențelor unui peisaj salin hibrid / Research carried out at Băile Figa during 2016–2019 Revealing the potential of a hybrid saltscape

Cercetări efectuate la Băile Figa în anii 2016–2019 și considerații privind deslușirea valențelor unui peisaj salin hibrid / Research carried out at Băile Figa during 2016–2019 Revealing the potential of a hybrid saltscape

Experimental study of the 2n-transfer reaction 138Ba(18O,16O)140Ba in the projectile energy range 61–67 MeV

Two-neutron transfer reactions serve as an important tool for nuclear-structure studies in the neutron-rich part of the nuclear chart. In this paper, we report on the first experimental attempt to populate the excited states of140Ba employing the 2n-transfer reaction138Ba(18O,16O)140Ba. 140Ba is highly important, as it is placed on the onset of octupole correlations and the lifetimes of its excited states are completely unknown, with the sole exception of the first state. The experiment was carried out at the Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN–HH) in Magurele, Romania. Lower limits on the lifetimes of the ground state band up to the state are reported. Furthermore, relative cross-sections regarding the 2n-transfer reaction with respect to the fusion and the total inelastic reaction channels have been deduced. Further investigation directions of the nuclear structure of 140Ba are also discussed.

Development of analysis methodology using Proton Induced X-ray Emission (PIXE) as a complementary technique to determine trace elements in environmental matrices

This article presents the methodology of analysis of industrial and environmental materials using Particle Induced X-ray Emission (PIXE) technique. The application of thick target PIXE technique using a 3 MeV proton beam at 3 MV Tandetron at Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH), Romania, in industrial and environmental complex studies proved to be very useful for the identification of a large series of trace elements, some of them being toxic for living organisms and humans and others contributing to the elemental cycling in natural environments. The main elements determined by PIXE are K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Br, Rb, Sr and Pb, using High Purity Germanium (HPGe) GDP-05145 (BSI) type detector of 20 mm2 surface, 8 mm thickness. In addition, Na, Mg, Al, Si, P, S, and Cl could be determined using external beam PIXE with X-123 SDD Fast Amptek silicon detector of 25 mm2 surface, 500 µm thickness. PIXE technique successfully complements other atomic and nuclear techniques, such as: energy dispersive X-ray fluorescence (ED-XRF), instrumental neutron activation analysis (INAA), inductively-coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS) and ion beam technique particle-induced gamma-ray emission (PIGE). A discussion is made regarding the suitability of PIXE technique to be further used in studies related to soil-crop toxic metal transfer in an agroecosystem, as well as heavy metals biosorbtion from industrial wastewater, for the investigation of level of contamination with metals and toxicants occurrence in environmental factors and human health risk assessment. The paper was presented at the Scientific Conference of the Doctoral School of Dunarea de Jos University of Galati (SCDS-UDJG), 7th edition, Galati, Romania, 13-14 June, 2019.