Institute Of Isotopes Research Articles

Bayesian inverse modeling and source location of an unintended <sup>131</sup>I release in Europe in the fall of 2011

Abstract. In the fall of 2011, iodine-131 (131I) was detected at several radionuclide monitoring stations in central Europe. After investigation, the International Atomic Energy Agency (IAEA) was informed by Hungarian authorities that 131I was released from the Institute of Isotopes Ltd. in Budapest, Hungary. It was reported that a total activity of 342 GBq of 131I was emitted between 8 September and 16 November 2011. In this study, we use the ambient concentration measurements of 131I to determine the location of the release as well as its magnitude and temporal variation. As the location of the release and an estimate of the source strength became eventually known, this accident represents a realistic test case for inversion models. For our source reconstruction, we use no prior knowledge. Instead, we estimate the source location and emission variation using only the available 131I measurements. Subsequently, we use the partial information about the source term available from the Hungarian authorities for validation of our results. For the source determination, we first perform backward runs of atmospheric transport models and obtain source-receptor sensitivity (SRS) matrices for each grid cell of our study domain. We use two dispersion models, FLEXPART and Hysplit, driven with meteorological analysis data from the global forecast system (GFS) and from European Centre for Medium-range Weather Forecasts (ECMWF) weather forecast models. Second, we use a recently developed inverse method, least-squares with adaptive prior covariance (LS-APC), to determine the 131I emissions and their temporal variation from the measurements and computed SRS matrices. For each grid cell of our simulation domain, we evaluate the probability that the release was generated in that cell using Bayesian model selection. The model selection procedure also provides information about the most suitable dispersion model for the source term reconstruction. Third, we select the most probable location of the release with its associated source term and perform a forward model simulation to study the consequences of the iodine release. Results of these procedures are compared with the known release location and reported information about its time variation. We find that our algorithm could successfully locate the actual release site. The estimated release period is also in agreement with the values reported by IAEA and the reported total released activity of 342 GBq is within the 99 % confidence interval of the posterior distribution of our most likely model.

LIST-mode applications for neutron multiplicity counting

In recent years, the data acquisition in neutron multiplicity measurements is rapidly changing from traditional shift-register electronics into fully digital LIST-mode acquisition machinery, allowing us to digitally record the detection time of each neutron.In the present study, we introduce two novel applications to the LIST-mode acquisition in neutron multiplicity counting. In the first application, we estimate the statistical uncertainty of the measurement using bootstrap analysis, and in the second application, we use the LIST mode acquisition to preform dead time corrections using a backward extrapolation technique.The applications were first tested by computer based simulations, and later applied to actual low mass fissile measurements conducted by the Institute of Isotopes in Hungary, showing satisfactory results.The methods presented in this study, while fairly easy to implement and do not require any prior calibration, often provide increased accuracy and higher reliability, when compared to the current methods traditionally used for shift-register multiplicity measurements.

A method for the estimation of fissile mass by measuring the number of neutron signals within a specific time interval

This paper presents a new method for fissile mass estimation by passive neutron interrogation. The method uses the stochastic transport equation to express the first three central moments (mean, variance and skewness) for the number of detected neutrons within a given time interval in terms of the fissile mass, the (α,n) rate and the multiplicity factor. Solving these three equations allows estimation of the fissile mass. As the primary validation of the method, it was implemented for several fissile mass measurements, which were conducted by the Nuclear Security Unit of the Joint Research Center (JRC) in Italy and by the Institute of Isotopes in Hungary.

Involvement of Jun Dimerization Protein 2 (JDP2) in the Maintenance of Epstein-Barr Virus Latency

Reactivation of the Epstein-Barr virus from latency is dependent on expression of the BZLF1 viral immediate-early protein. The BZLF1 promoter (Zp) normally exhibits only low basal activity but is activated in response to chemical inducers such as 12-O-tetradecanoylphorbol-13-acetate and calcium ionophore. We found that Jun dimerization protein 2 (JDP2) plays a significant role in suppressing Zp activity. Reporter, EMSA, and ChIP assays of a Zp mutant virus revealed JDP2 association with Zp at the ZII cis-element, a binding site for CREB/ATF/AP-1. Suppression of Zp activity by JDP2 correlated with HDAC3 association and reduced levels of histone acetylation. Although introduction of point mutations into the ZII element of the viral genome did not increase the level of BZLF1 production, silencing of endogenous JDP2 gene expression by RNA interference increased the levels of viral early gene products and viral DNA replication. These results indicate that JDP2 plays a role as a repressor of Zp and that its replacement by CREB/ATF/AP-1 at ZII is crucial to triggering reactivation from latency to lytic replication.

Energy monitoring device for 1.5–2.4 MeV electron beams

An easy-to-use and robust energy monitoring device has been developed for reliable detection of day-to-day small variations in the electron beam energy, a critical parameter for quality control and quality assurance in industrial radiation processing. It has potential for using on-line, thus providing real-time information. Its working principle is based on the measurement of currents, or charges, collected by two aluminium absorbers of specific thicknesses (dependent on the beam energy), insulated from each other and positioned within a faraday cup-style aluminium cage connected to the ground. The device has been extensively tested in the energy range of 4–12 MeV under standard laboratory conditions at Institute of Isotopes and CNR-ISOF using different types of electron accelerators; namely, a TESLA LPR-4 LINAC (3–6 MeV) and a L-band Vickers LINAC (7–12 MeV), respectively. This device has been also tested in high power electron beam radiation processing facilities, one equipped with a 7-MeV LUE-8 linear accelerator used for crosslinking of cables and medical device sterilization, and the other equipped with a 10 MeV Rhodotron TT100 recirculating accelerator used for in-house sterilization of medical devices. In the present work, we have extended the application of this method to still lower energy region, i.e. from 1.5 to 2.4 MeV. Also, we show that such a device is capable of detecting deviation in the beam energy as small as 40 keV.

Chaperone Properties of Mammalian Mitochondrial Translation Elongation Factor Tu

The main function of the prokaryotic translation elongation factor Tu (EF-Tu) and its eukaryotic counterpart eEF1A is to deliver aminoacyl-tRNA to the A-site on the ribosome. In addition to this primary function, it has been reported that EF-Tu from various sources has chaperone activity. At present, little information is available about the chaperone activity of mitochondrial EF-Tu. In the present study, we have examined the chaperone function of mammalian mitochondrial EF-Tu (EF-Tumt). We demonstrate that recombinant EF-Tumt prevents thermal aggregation of proteins and enhances protein refolding in vitro and that this EF-Tumt chaperone activity proceeds in a GTP-independent manner. We also demonstrate that, under heat stress, the newly synthesized peptides from the mitochondrial ribosome specifically co-immunoprecipitate with EF-Tumt and are destabilized in EF-Tumt-overexpressing cells. We show that most of the EF-Tumt localizes on the mitochondrial inner membrane where most mitochondrial ribosomes are found. We discuss the possible role of EF-Tumt chaperone activity in protein quality control in mitochondria, with regard to the recently reported in vivo chaperone function of eEF1A.

Gold catalyst research at the institute of Isotopes, Budapest

Gold catalyst research at the institute of Isotopes, Budapest

Application of Hypermet-PC in PGAA

Hypermet-PC has been developed in the mid-nineties at the Institute of Isotopes and Surface Chemistry based on a successful FORTRAN code from the seventies. With additional calibration routines and other helping features it has proved to be a very useful tool in quantitative analysis performed either with NAA or with PGAA. The sophisticated built-in peak-shape function allows the fitting of asymmetric peaks from large-volume germanium detectors over a very wide energy range needed for PGAA. The experience collected when evaluating several thousands gamma-spectra acquired for routine analysis and spectroscopic research, is summarized in the paper.

Measurements on Shielding Experiments Using Al203:Mg,Y TL Detectors

Experiments were performed in the irradiation tunnel of the 100 kW research reactor of the Institute of Nuclear Technics of the Technical University of Budapest. Dose rates were measured in a straight cylindrical duct and in ducts with bends of 30, 60 and 90 deg. Al2O3:Mg,Y ceramic TL detectors type D-2, developed at the Institute of Isotopes, were found to be better for measuring gamma ray dose than TLD-700, not only because of their linearity over a fairly wide dose range (10-1 - 103 Gy) but also their lower sensitivity (3.4 mGy per 1010 n.cm-2) to thermal neutrons.

Production and Use of Nitrogen-15 in German Agricultural, Biomedical and Ecological Research -A Historical Review-

Abstract The history of production and application of the stable nitrogen isotope15N in Germany is mainly part of the history of the former Institute of Stable Isotopes, later a part of the Central Institute of Isotope and Radiation Research (Zentralinstitut fur Isotopen-und Strahlenforschung) in Leipzig. In 1956, after a relatively large fractionation during isotopic exchange in the system NO/HNO3 was reported by SPINDEL and TAYLOR, the construction of an isotope enrichment plant was planned and started work in 1958 on a laboratory scale. The prodution of 15N-labelled material in the institute started in 1960, followed in 1968 by the start of a separation plant in Wolfen as a branch of industrial fertilizer production. The economy was optimized by feeding back the 15N decreased efflux to the fertilizer production line. The material produced was used for studies at home and abroad. Close contacts with the IAEA (International Atomic Energy Agency, Vienna) and the development of an easy-to-handle optical in...

Integral cross section of the99Tc(γ,γ′)99mTc reaction at 4 MeV

99mTc production was studied with the aid of photoexcitation by a 4 MeV endpoint energy bremsstrahlung from the LINAC of the Institute of Isotopes, Budapest. The intensity of the γ-flux was monitored by disc-shaped natural indium plates, placed in front of and behind the small cylindrical aluminium holders containing TcO2 samples in a powder form. Isomeric activities were measured through the 140 keV γ-line by a Ge spectrometer. The integral cross section at 4 MeV was found to be 63.3±7.1 μbMeV, which can be considered reasonable compared to the corresponding value of 55.3 μbMeV established for the115In (γ,γ′)115mIn reaction. We also attempted the photoexcitation of99mTc by irradiation with γ-rays from a 1.5×1015 Bq60Co source, but no isomeric activity could be observed. This places the first activation level between 1.33 and 4 MeV.

Vacuum treatment of CR-39 for the reduction of background in neutron induced autoradiography of boron

Abstract The influence of etching time and vaccum processing before, during, and after neutron irradiation on the “signal/noise” ratio of the neutron induced autoradiography of boron using CR-39 track detectors has been investigated. The neutron irradiation was carried out in a vacuum chamber using the Cf-252 neutron source of the Central Institute of Isotope and Radiation Research at Leipzig. Hungarian-made CR-39 type track detectors, MA-ND/p and MA-ND/α, produced in different years, are compared. After a few hours of 2 kPa (about 10 -2 Torr) vacuum treatment, the “signal/noise” ratio for boron determination is improved remarkably in most cases of the detector and etching-time combinations used.

Evaluation of Autoradiograms by Microdensitometry and Imaging

The aim of this work is to compare results of the densitometric evaluation techniques used in the Central Research Institute for Physics Budapes: (KFKI) to that performed at the Central Institute of Isotope and Radiation Research Leipzig (ZfI) on purpose to improve the resolution and precision respectively. Optical density distributions along defined lines of the autoradiograms are measured by a JOYCE LOEBL Double Beam Recording Microdensitometer type MK-III.CS in the KFKI laboratory and by a modified ZEISS-Schnellphotometer G2 in the ZfI laboratory. A full screen imaging of the autoradiograms may be performed by means of the DENSITRON 4 image analyzer developed in ZfI. Results obtained in this work will be discussed.

Benefits of Important Industrial Tracer Applications in the GDR

Tracers can be used to label substances or objects in order to discriminate between them, to follow their movement, to record changes of concentration and distribution between phases, etc. The main advantages of tracer investigations are the contactless recording of signals without influencing the observed process (also under rigorous operation conditions), the high detection sensitivity, the large number of available tracer nuclides (problems of all branches of industry can be solved) and the fact that tracer investigation can be carried out on operating production units, so that they provide valuable checks of the validity of design and process data. The cost-to-benefit ratio can be as low as 1:50. In the following some selected examples of tracer applications carried out by the staff of the Central Institute of Isotope and Radiation Research and their benefits will be presented.

20 Years Central Institute of Isotope and Radiation Research – A Review of the last 5 Years

In a review the most important results of the Central Institute of Isotope and Radiation Research (ZfI) in the last 5 years are given. Besides the theoretical studies about properties of isotopes a...

Das Mikrotron am ZfI Leipzig – Aufbau, Grundlagenuntersuchungen und Anwendungen

During December 1987 a microtron was put into operation at the Central Institute of Isotope and Radiation liesearch Leipzig. The maximum electron energy and current planned amounts to 25 MeV and 10 … 20 μA, respectively. After few weeks of operation an energy of 17 MeV was obtained. After conditioning the accelerator will be used preferably for activation analysis and radionuclide production. Some important components of the accelerator and possible applications are briefly discussed.

Über die Entwicklung des Praktikum-Programms für einen Trainingskurs in Radiochemie im Zentralinstitut für Isotopen- und Strahlenforschung

Since 1956 a radiochemical practice was performed at the Department of Radiation Sources and Nuclear Pharmaceuticals of the Central Institute of Isotope and Radiation Research of the Academy of Sciences of the GDR. Beginning about 1970 the programme of the course was entirely renewed to cover the field of application in the biological and medical sciences. Modern techniques of measurement, short-lived radionuclides from nuclide cows, labelling of proteins, compartment kinetics, radioimmunoassays and the estimation of binding constants are subjects of the recent programme.

Design, Evaluation and Handling of Gamma Irradiators – 10 Years of PANORAMA Unit Operation

Since 1976 a universal 60Co irradiation unit of the PANORAMA type has been available at the Central Institute of Isotope and Radiation Research, Leipzig. The great geometrical variety of the PANORAMA unit permits very different irradiation conditions. To use this flexibility and for optimum arrangement of the sources an extensive computer-aided evaluation by means of the code DOSKMF2 was developed and has successfully been applied. Some experience of the last 10 years in relation to the use, maintenance, limitations, efficiency and to the computer-aided evaluation of the PANORAMA unit as well as to the design of industrial facilities is summarized.

Dose intercomparison using spectrophotometric readout method for free radical dosimetry

The present paper describes the dose intercomparison studies with alanine and glutamine using the spectrophotometric readout method. These dosimeters were used for γ irradiations at the Institute of Isotopes, Budapest and ISOMED (BARC). Both electron (10 MeV) and γ irradiations were done at RISO (Denmark). There was a very good agreement between the measured and nominal dose values.

15 Jahre Strahlenforschung im Zentralinstitut für Isotopen- und Strahlenforschung Leipzig

An efficient potential for radiation research has been developed at the Central Institute of Isotope and Radiation Research in Leipzig since 1969. 2Iany problems in the field of basic and applied research of radiation chemistry and biology have been studied. Ten gamma plants and two electron accelerators have been designed and established for scientific, industrial and agricultural application.