Budapest Research Reactor Research Articles

PyEGAF: An open-source Python library for the Evaluated Gamma-ray Activation File

The Evaluated Gamma-ray Activation File (EGAF) is one of the most comprehensive resources for thermal neutron-capture data. This database contains data from prompt gamma activation analysis measurements carried out in a consistent manner using the same experimental configuration at the Budapest Research Reactor for 245 isotopes. Although these valuable datasets have been freely available for many years, one of the drawbacks is the outdated and cryptic Evaluated Nuclear Structure Data File (ENSDF) format that is currently adopted for dissemination, making it difficult for users unfamiliar with the format to access and utilize the data contained therein. Furthermore, the ENSDF format does not readily lend itself to modern computational technologies and a parser is required to interpret the complicated mixed-record format. To help overcome these challenges, we have developed a translator to convert the ENSDF-formatted datasets into an open standard JavaScript Object Notation (JSON) format enabling accessibility to applications using different programming languages running in different environments. To compliment this effort, we have also developed an open-source software package implemented in Python, pyEGAF, that is designed to interact with the JSON data structures for general purpose access, manipulation, and analysis of the neutron-capture γ-ray data in EGAF. The new format, together with the pyEGAF library, greatly enhances access to the wider applications community where EGAF data may be useful or is required.

Assessment of neutron-induced activation of irradiated samples in a research reactor

The combination of MCNP6 and the FISPACT codes was used to predict inventories of radioisotopes produced by neutron exposure of a sample in a research reactor. The detailed MCNP6 model of the Budapest Research Reactor and the specific irradiation geometry of the NAA channel was established, while realistic material cards were specified based on concentrations measured by PGAA and NAA, considering the precursor elements of all significant radioisotopes. The energy- and spatial distributions of the neutron field calculated by MCNP6 were transferred to FISPACT, and the resulting activities were validated against those measured using neutron-irradiated small and bulky targets. This approach is general enough to handle different target materials, shapes, and irradiation conditions. A general agreement within 10% has been achieved. Moreover, the method can also be made applicable to predict the activation properties of the near-vessel concrete of existing nuclear installations or assist in the optimal construction of new nuclear power plant units.

Measurement of the 242Pu(n, γ) cross section from thermal to 500 keV at the Budapest research reactor and CERN n_TOF-EAR1 facilities

The design and operation of innovative nuclear systems requires a better knowledge of the capture and fission cross sections of the Pu isotopes. For the case of capture on 242Pu, a reduction of the uncertainty in the fast region down to 8-12% is required. Moreover, aiming at improving the evaluation of the fast energy range in terms of average parameters, the OECD NEA High Priority Request List (HPRL) requests high-resolution capture measurements with improved accuracy below 2 keV. The current uncertainties also affect the thermal point, where previous experiments deviate from each other by 20%. A fruitful collaboration betwen JGU Mainz and HZ Dresden-Rossendorf within the EC CHANDA project resulted in a 242Pu sample consisting of a stack of seven fission-like targets making a total of 95(4) mg of 242Pu electrodeposited on thin (11.5 μm) aluminum backings. This contribution presents the results of a set of measurements of the 242Pu(n, γ) cross section from thermal to 500 keV combining different neutron beams and techniques. The thermal point was determined at the Budapest Research Reactor by means of Neutron Activation Analysis and Prompt Gamma Analysis, and the resolved (1 eV - 4 keV) and unresolved (1 - 500 keV) resonance regions were measured using a set of four Total Energy detectors at the CERN n_TOF-EAR1.

Improved 242Pu(n,$ \gamma$) thermal cross section combining activation and prompt gamma analysis

A good knowledge of the radiative capture cross section of 242Pu is required for innovative nuclear reactor studies, especially for MoX fuel reactors. However, the experimental data available show discrepancies in the energy regions of interest: the thermal point and the keV region. Previous experimental results of the thermal cross section deviate from each other by 20% and these discrepancies are reflected also in the evaluated libraries, each of them giving more credit to different data sets. A recent measurement by Genreith et al. did not succeed to solve the existing discrepancy due to the large uncertainties and correction factors in the analysis. This work presents a new measurement of the thermal capture cross section of 242Pu carried out in the Budapest Research Reactor using the same thin targets of a previous measurement at n_TOF-EAR1, each containing 30mg of 99.995% pure 242Pu . The combined analysis of the full prompt $ \gamma$-ray spectrum and the 243Pu decay has led to three compatible values for the thermal cross section. Their average value, 18.9(9)b, has an improved accuracy compared to recent measurements. Leaving aside the activation value of Genreith using an outdated intensity value for the 84 keV decay line of 243Pu , our average result is in very good agreement with the JEFF-3.2 evaluation and all the previous measurements, with the exception of the highest value 22.5(11)b reported by Marie et al., which has a strong influence in the ENDF evaluation.

Radiative-capture cross sections for the La139(n,γ) reaction using thermal neutrons and structural properties of La140

A set of prompt partial $\gamma$-ray production cross sections from thermal neutron-capture were measured for the $^{139}$La($n,\gamma$) reaction using a guided beam of subthermal (thermal and cold) neutrons incident upon a $^{\rm nat}$La$_{2}$O$_{3}$ target at the Prompt Gamma Activation Analysis facility of the Budapest Research Reactor. Absolute $^{140}$La cross sections were determined relative to the well-known comparator $^{35}$Cl($n,\gamma$) cross sections from the irradiation of a stoichiometric $^{\rm nat}$LaCl$_{3}$ sample. The total cross section for radiative thermal neutron-capture on $^{139}$La from the sum of experimentally measured cross sections observed to directly feed the $^{140}$La ground state was determined to be $\sigma_{0}^{\rm expt} = 8.58(50)$ b. To assess completeness of the decay scheme and as a consistency check, the measured cross sections for transitions feeding the ground state from levels below a critical energy of $E_{c} = 285$ keV were combined with a modeled contribution accounting for ground-state feeding from the quasicontinuum to arrive at a total cross section of $\sigma_{0} = 9.36(74)$ b. In addition, a neutron-separation energy of $S_{n} = 5161.005(21)$ keV was determined from a least-squares fit of the measured primary $\gamma$-ray energies to the low-lying levels of the $^{140}$La decay scheme. Furthermore, several nuclear structure improvements are proposed for the decay scheme. The measured cross-section and separation-energy results are comparable to earlier measurements of these quantities.

Preparation for activation measurements of concrete and PE-B4C-concrete to be applied for shielding at the European Spallation Source

To improve the effect of the concrete below 10 MeV where iron has resonances in the cross section, a new concrete have been developed. The PE-B4C-concrete utilizes hydrogen containing PE to thermalize the neutron and boron for in situ absorption. It is of utmost importance that the activation of the shielding material itself is well-understood, since it is planned to be used at the ESS. The first steps in this direction are shown the present study, in which concrete as well as reference aluminium samples are subject to XRF measurements to precisely determine the element content. This is compared to data sheets from the vender, and simulations are carried out to predict the sample activity.The samples are planned for insertion into the the Budapest Research Reactor, followed be activity and spectral measurements.

Measuring neutron capture rates on ILL-produced unstable isotopes (147Pm, 171Tm and 204Tl, and plans for 79Se and 163Ho) for nucleosynthesis studies

Neutron capture cross sections are among the main inputs for nucleosynthesis network calculations. Although well known for the majority of the stable isotopes, this quantity is still unknown for most of the unstable isotopes of interest. A recent collaboration between ILL, PSI, U. Sevilla and IFIC aims at producing the isotopes of interest at ILL, preparing suitable targets at PSI, and measuring their capture cross sections at facilities such as n_TOF/CERN, LiLiT and the Budapest Research Reactor (BRR). This work is focused on the description of the different beams and techniques and shows some highlights of the preliminary results of the capture measurements on 171Tm, 147Pm and 204Tl, along with the future plans for 79Se and 163Ho.

Thermal neutron capture cross sections forO16,17,18andH2

Author(s): Firestone, RB; Revay, Z | Abstract: Thermal neutron capture γ-ray spectra for O16,17,18 and H2 have been measured with guided cold neutron beams from the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) reactor and the Budapest Research Reactor (BRR) on natural and O17,18 enriched D2O targets. Complete neutron capture γ-ray decay schemes for the O16,17,18(n,γ) reactions were measured. Absolute transition probabilities were determined for each reaction by a least-squares fit of the γ-ray intensities to the decay schemes after accounting for the contribution from internal conversion. The transition probability for the 870.76-keV γ ray from O16(n,γ) was measured as Pγ(871)=96.6 ±0.5% and the thermal neutron cross section for this γ ray was determined as 0.164±0.003 mb by internal standardization with multiple targets containing oxygen and stoichiometric quantities of hydrogen, nitrogen, and carbon whose γ-ray cross sections were previously standardized. The γ-ray cross sections for the O17,18(n,γ) and H2(n,γ) reactions were then determined relative to the 870.76-keV γ-ray cross section after accounting for the isotopic abundances in the targets. We determined the following total radiative thermal neutron cross sections for each isotope from the γ-ray cross sections and transition probabilities; σ0(O16)=0.170±0.003 mb; σ0(O17)=0.67±0.07 mb; σ0(O18)=0.141±0.006 mb; and σ0(H2)=0.489±0.006 mb.

Upgrade of the Budapest neutron activation analysis laboratory

Just 1 year after the Budapest Research Reactor went critical on 29 March 1959, the Neutron Activation Analysis laboratory started its operation. During the past 55 years this laboratory contributed to many important innovations in NAA and gamma spectroscopy, including the k 0-standardization, irradiation-site characterization, detector efficiency calibration and gamma spectroscopy. From 2012, the laboratory is being revitalized and instrumentally modernized. This paper gives a comprehensive overview of the present technical capabilities, the ongoing upgrade program and the prospects for future utilization. The analysis protocols are discussed in details to give guidance to our user community.

Serial Delay-Line Readout for Position Sensitive Neutron Beam Monitor

The intensity of neutron beams is measured by neutron beam monitor detector at research reactors, in order to allow normalization of neutron scattering data. A two dimensional position sensitive neutron beam monitor has been developed, able to measure the distribution of beam intensity in its cross-section. The neutron adsorption efficiency of these monitor detectors are low enough to minimize the intensity loss, but high enough to provide low statistical error. Since the number of detected events is not too high, the dead time is not crucial for these detectors. A novel readout method has been developed that slightly increases the dead time but eventuates a robust, simple and flexible system. This new method relies on the serial connection of the delay-lines, minimizing the number of analogue signals. Two or three analogue signal outputs are enough to reconstruct the two-dimensional intensity matrix. Combining this new method with a comprehensive acquisition on the primary signals, the quality parameters of the detectors are also improved. Design and measurement results at the Budapest Research Reactor are presented.

Improving Research Reactor Accident Response Capability at the Hungarian Nuclear Safety Authority

The paper describes the design and implementation of an on-line operation monitoring and accident response support system to be used at the emergency response center of Hungarian Atomic Energy Authority (HAEA). The system is called CERTA VITA and it is able to monitor the four VVER-440 units of the Hungarian Paks nuclear power plant (NPP) during their normal operation and during emergencies (including severe accidents). As a result from the analyses following the severe accident at Fukushima the HAEA decided to extend the CERTA VITA system on the Budapest Research Reactor (BRR), which is a tank type research reactor with 10 MW thermal power. The extension of the present system was realized in co-operation with the Centre for Energy Research, the operator of BRR. It is believed that by the introduction of this new on-line system the accident response capabilities of HAEA will be further enhanced and the BRR emergencies will be handled at the same professional level as potential emergencies at Paks NPP.

Neutron Based Imaging and Element-mapping at the Budapest Neutron Centre

The Budapest Neutron Centre (BNC) is a consortium of institutes to co-ordinate research activities carried out at the Budapest Research Reactor. It hosts two neutron imaging facilities (RAD and NORMA) operated by the Centre for Energy Research, Hungarian Academy of Sciences and offers access to this scientific infrastructure for the domestic and international users.The radiography station (RAD) at the thermal neutron beamline of the reactor gives a possibility to study relatively large objects by thermal neutron-, gamma- and X-ray radiography, and to benefit from the complementary features of the different radiations. RAD is being extended in 2014 with digital imaging and tomographic capabilities. The image detection is based on suitable converter screens. The static radiography and tomography images are acquired by a new, large area sCMOS camera, whereas the dynamic radiography is accomplished by a low-light-level TV camera and a frame grabber card.The NORMA facility is designed to perform neutron radiography and tomography on small samples using guided cold neutrons. Here two non-destructive techniques are coupled to determine the chemical composition and to visualize the internal structure of heterogeneous objects. The position-sensitive element analysis with prompt-gamma activation analysis (PGAA) and the imaging with neutron radiography/tomography (NR/NT) are integrated into a unique facility called NIPS-NORMA. The goal of such a combination of these methods is to save substantial beam time in the so-called NR/NT-driven PGAI (Prompt Gamma Activation Imaging) mode, in which the interesting regions are first visualized and located, and subsequently the time-consuming prompt-gamma measurements are made only where it is really needed.The paper will give an overview about the technical details of the facilities, and the latest results of selected applications from the fields of archaeometry, engineering and material science.

Radiative Capture Cross Sections of 155,157Gd for Thermal Neutrons

Thermal neutron radiative capture cross sections σ0γ of 155,157Gd are determined by summing the transition cross sections feeding the ground states of the respective product nuclei. The transition cross sections feeding the ground states from the discrete states in the low-excitation region, where the decay schemes are known completely, were measured using a guided cold neutron beam at the Budapest Research Reactor. Transitions from the states at the higher excitation, the so-called quasi-continuum levels, are determined from simulations with the extreme statistical model normalized to the intensity balance through the low-lying discrete levels. A significant non-1/v correction was applied to 155,157Gd, leading to σ0γ(155Gd) = 56 700(2100) b and σ0γ(157Gd) = 239 000(6000) b.

Neutron Flux Characterization of the Cold Beam PGAA-NIPS Facility at the Budapest Research Reactor

Reliable flux characterization is essential for facilities using neutron beams. Hence, the NIPS station at the Budapest Research Reactor has recently been equipped with neutron-tomographic equipment. The beam can also be characterized by means of a large surface wire chamber and application of the time-of-flight method. The energy distribution was measured at three horizontal positions with the surface wire chamber in pinhole geometry, while the spatial inhomogeneity was determined by means of our new neutron-tomographic equipment.

New Measurement of the Thermal-capture Cross Section for the Minor Isotope 180W

Tungsten occurs naturally in five isotopic forms; four of them, 182,183,184,186W, contribute significantly to the overall elemental abundance (with each contribution between 14 and 30 %), whereas 180W only occurs at the 0.12 % level and is a minor isotope. Given its very low abundance, a precise measurement of the thermal neutron-capture cross section is extremely challenging. This work reports a new value of the thermal neutron-capture cross section from a direct 180W(n,γ) measurement using a guided-thermal beam at the Budapest Research Reactor, incident upon an 11.35 % enriched sample to induce prompt γ-ray activation within the sample. The thermal-capture cross section was determined as the sum of experimentally observed partial neutron-capture γ-ray cross sections feeding the ground state directly, and, the modeled contribution from the (unobserved) ground-state feeding predicted from statistical-model calculations using the Monte Carlo program DICEBOX. The preliminary value of the 180W(n,γ) thermal neutron-capture cross section is 20.5(42) b.

Determination of the 151Eu(n,γ)[formula omitted]Eu and 153Eu(n,γ)154Eu Reaction Cross Sections at Thermal Neutron Energy

We have measured partial γ-ray cross sections following neutron capture in enriched 151Eu and 153Eu targets at the cold-neutron-beam facility of the Budapest Research Reactor. The cross sections were standardized using a stoichiometric natEuCl3 target with the well-known 1951-keV γ-ray cross section from the 35Cl(n,γ)36Cl reaction at the cold-neutron-beam facility of the Garching Research Reactor. The γ-ray cross sections were corrected for effective g-factors. These data were combined with the structural information of 152Eu and 154Eu given in the Evaluated Nuclear Structure Data File to produce capture γ-ray level schemes. The total radiative capture cross sections of the 151Eu(n,γ)152m1,gEu and 153Eu(n,γ)154Eu reactions were determined by summing the experimental transition intensities from known levels with simulated intensities of transitions from higher excitations to the ground- or metastable-state. The individual 151Eu(n,γ)152m1Eu and 151Eu(n,γ)152gEu reaction cross sections disagree with values in the literature. However, the total cross section of the 151Eu(n,γ)152Eu reaction does agree with those values. Also, our deduced cross section for the 153Eu(n,γ)154Eu reaction closely follows the data in the literature. These results are supported by an earlier standardization experiment done at the Budapest Research Reactor using a target of Eu2O3 solution in H2SO4.

Proceedings of 6th International k 0-Users’ Workshop

The upcoming 32 papers in this issue of the Journal of Radioanalytical and Nuclear Chemistry have been presented at the 6th International k0-Users’ Workshop at Hotel Gellert in Budapest 22–27 Sep, 2013. The conference was organized by k0 International Scientific Committee and by the Laboratory of Nuclear Analytical Chemistry at the Center for Energy Research at Budapest. Previous workshops in the series were held in Astene, Belgium (1992); Ljubljana, Slovenia (1996); Bruges, Belgium (2001); Funchal, Portugal (2005) and Belo Horizonte, Brazil (2009). Forty participating scientists from 13 different countries (Argentina, Australia, Brazil, Canada, Germany, Hungary, India, Italy, Morocco, Peru, Portugal, Slovenia, USA) from all five continents met in Budapest to discuss the latest developments in the field of k0-based Neutron Activation Analysis. At the beginning of the conference, a lifeachievement award was presented to Andras Simonits, one of the inventors of the k0 method. The papers were presented in the following sessions: Facilities, Prompt Gamma Activation Analysis, Methodological Developments, Software, Quality Assurance/Quality Control, New Nuclear Data, Special Session for Radioactive Targets, and Applications. A scientific visit was paid to the Budapest Research Reactor at the PGAA and at the NAA laboratories. The next, 7th k0-Users’ Workshop is expected to be held in Montreal, Canada in 2017. k0 International Scientific Committee (members active during the period of the organization of the conference)

Investigation of the tungsten isotopes via thermal neutron capture

Total radiative thermal neutron-capture $\ensuremath{\gamma}$-ray cross sections for the ${}^{182,183,184,186}$W isotopes were measured using guided neutron beams from the Budapest Research Reactor to induce prompt and delayed $\ensuremath{\gamma}$ rays from natural and isotopically-enriched tungsten targets. These cross sections were determined from the sum of measured $\ensuremath{\gamma}$-ray cross sections feeding the ground state from low-lying levels below a cutoff energy, ${E}_{\mathrm{crit}}$, where the level scheme is completely known, and continuum $\ensuremath{\gamma}$ rays from levels above ${E}_{\mathrm{crit}}$, calculated using the Monte Carlo statistical-decay code dicebox. The new cross sections determined in this work for the tungsten nuclides are ${\ensuremath{\sigma}}_{0}{(}^{182}\mathrm{W})=20.5(14)$ b and ${\ensuremath{\sigma}}_{11/{2}^{+}}{(}^{183}{\mathrm{W}}^{m},5.2\phantom{\rule{0.28em}{0ex}}\mathrm{s})=0.177(18)$ b; ${\ensuremath{\sigma}}_{0}{(}^{183}\mathrm{W})=9.37(38)$ b and ${\ensuremath{\sigma}}_{{5}^{\ensuremath{-}}}{(}^{184}{\mathrm{W}}^{m},8.33\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{s})=0.0247(55)$ b; ${\ensuremath{\sigma}}_{0}{(}^{184}\mathrm{W})=1.43(10)$ b and ${\ensuremath{\sigma}}_{11/{2}^{+}}{(}^{185}{\mathrm{W}}^{m},1.67\phantom{\rule{0.28em}{0ex}}\mathrm{min})=0.0062(16)$ b; and, ${\ensuremath{\sigma}}_{0}{(}^{186}\mathrm{W})=33.33(62)$ b and ${\ensuremath{\sigma}}_{9/{2}^{+}}{(}^{187}{\mathrm{W}}^{m},1.38\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{s})=0.400(16)$ b. These results are consistent with earlier measurements in the literature. The ${}^{186}$W cross section was also independently confirmed from an activation measurement, following the decay of ${}^{187}$W, yielding values for ${\ensuremath{\sigma}}_{0}{(}^{186}\mathrm{W})$ that are consistent with our prompt $\ensuremath{\gamma}$-ray measurement. The cross-section measurements were found to be insensitive to choice of level density or photon strength model and only weakly dependent on ${E}_{\mathrm{crit}}$. Total radiative-capture widths calculated with dicebox showed much greater model dependence; however, the recommended values could be reproduced with selected model choices. The decay schemes for all tungsten isotopes were improved in these analyses. We were also able to determine new neutron-separation energies from our primary $\ensuremath{\gamma}$-ray measurements for the respective ($n,\ensuremath{\gamma}$) compounds: ${}^{183}$W [${S}_{n}=6190.88(6)$ keV]; ${}^{184}$W [${S}_{n}=7411.11(13)$ keV]; ${}^{185}$W [${S}_{n}=5753.74(5)$ keV]; and, ${}^{187}$W [${S}_{n}=5466.62(7)$ keV].

Prompt Gamma Activation Analysis at the Budapest Research Reactor

Abstract Prompt gamma activation analysis is a powerful method, but it is not yet well enough known in the nuclear data community. For this reason, we describe the PGAA measurement and data evaluation processes, as well as the energy and spatial distribution measurements on our cold neutron beam at the PGAA-NIPS facilities of the Budapest Research Reactor. We emphasize that the strong spatial inhomogeneity of the neutron beam puts a constraint on the samples to be analysed if it is important to obtain accurate quantitative measurement results. Finally, an overview of our recent experiments is given.

Neutron techniques for developing engineering welding methods

This paper examines important technical issues pertaining to the methodological limitations of the welding techniques currently in use, with particular consideration given to welding mathematical modelling procedures. The recent progress achieved with high nano-technologies suggests the application of similar approaches to conventional mechanics and materials science, with particular reference to welding processes. Recent studies on welded joints have highlighted the benefits to be derived from ‘Industrial Applications of Neutron Techniques’ giving access to fundamental information – not obtainable using other methods – for improving quality and durability. ‘Small angle neutron scattering’ and ‘determination of residual stress by neutron diffraction’ make it possible to characterize materials at the atomic and nanoscale level, offering existing technologies the essential contribution of precise structural methods. This paper describes the fundamental theoretical aspects of both techniques, along with several welding studies conducted using ‘small angle neutron scatter’. An experimental programme has recently been devised by Rogante Engineering, in collaboration with the Budapest Research Reactor, to develop welding processes aimed at improving safety, quality control, and durability control for the joints under consideration.