Aim of this work was the detection of fission products activity distribution along the axial dimension of irradiated fuel elements (FEs) at the TRIGA Mark II research reactor of the Technische Universitat (TU) Wien. The activity distribution was measured by means of a customized fuel gamma scanning device, which includes a vertical lifting system to move the fuel rod along its vertical axis. For each investigated FE, a gamma spectrum measurement was performed along the vertical axis, with steps of 1 cm, in order to determine the axial distribution of the fission products. After the fuel elements underwent a relatively short cooling down period, different fission products were detected. The activity concentration was determined by calibrating the gamma detector with a standard calibration source of known activity and by MCNP6 simulations for the evaluation of self-absorption and geometric effects. Given the specific TRIGA fuel composition, a correction procedure is developed and used in this work for the measurement of the fission product Zr-95. This measurement campaign is part of a more extended project aiming at the modelling of the TU Wien TRIGA reactor by means of different calculation codes (MCNP6, Serpent): the experimental results presented in this paper will be subsequently used for the benchmark of the models developed with the calculation codes.

The prediction of the time evolution of the nuclear fuel composition is one of the key issues concerning the design and operation of nuclear plants. With this target in mind, a methodology, based on Monte Carlo codes calculations validated by direct measurements, was developed to estimate the transmutation rates of nuclides relevant for the study and analysis of nuclear fuel composition under irradiation, focusing on major and minor actinides build-up and burn-up and on fission product production and depletion. Material targets containing the nuclides relevant for the study and analysis of nuclear fuel composition were irradiated in a well characterized irradiation position of the TRIGA Mark II reactor of Vienna Atominstitut in order to detect the transmutation rates (production & depletion) by means of gamma-ray spectrometry technique. The experiment was then simulated using the Serpent-2 reactor model recently developed and validated as presented at the RRFM 2017 conference. Calculated and experimental results were then compared to verify the capability of Serpent-2 reactor model to predict changes in the composition of nuclear fuel under irradiation and are reported in this paper.

The Vienna TRIGA Mark II reactor was modelled by means of the Serpent-2 Monte Carlo burnup calculation code. The purpose of the modelling is the determination of core critical parameters and of nuclear fuel composition time evolution. This paper presents the Serpent-2 reactor model validation process carried out during the last year. Taking into account the irradiation history, the fuel composition was calculated for a certain number of fuel elements in the current core. The fuel elements were selected in order to sample the different core areas, rising from internal B ring to the external part of the core. Subsequently, the calculation results were compared with different fission product activity values measured in the corresponding fuel elements. The measurement campaign was previously performed by means of a fuel gamma-scanning machine installed at the reactor as presented at the RRFM 2016. The comparison of fission products activity values obtained by Serpent-2 model calculation and by direct measurements are presented in this paper.

F rom the analysis of a data sample corresponding to an integrated luminosity of 4.63 pb -1 taken during the 1990 run of LEP at centre of mass energies between 88.2GeV an 94.2GeV, the tau decays r ~ e g e v T , r -* ,u-~ .v~ , r ~ z c ( K ) v T , r r p v ~ and their charge conjugates have been studied. The following branching ratios have been measured; B R ( r ~ e aTeVT) = 18.6 + 0.8 (stat.) _ 0.6 (sys.)%, BR (z---+ /~17u vT) = 17.4 • 0.7 + 0.6%, B R ( r ~ z c ( K ) v T ) = 11.9_+0.7_ 0.7%, BR ( r > p vT) = 22.4 + 0.8 + 1.3%, in good agreement with world averages. The measured electronic and muonic branching ratios lead to a measurement of the strong coupling constant, es (mT) = 0.26 + 0.09 Extrapolating the c L value from -0 .12" m T to m z yields cL(mz)=0 .109 +0.012 0.028" The average polarization P~ of taus produced in Z---, r + r decays has also been measured using the above decay modes. The weighted mean of the polarizations obtained from the four decay modes is PT = 0.24 _+ 0.07. This value of PT gives, in the improved Born approximation, a ratio between the axial and vector coupling constants of the tau of vT/aT=0.12+__O.04, and hence a value of the effective electroweak mixing parameter sin 2 0 w(m~) = 0.220 _ 0.009.

An analysis of the production of the baryon in the hadronic decays of the Z is presented based on about K multihadronic events collected by the DELPHI detector at LEP during and The di erential cross section of the and the correlations between and  produced in the same event are compared to current models based both on string fragmentation and on cluster decay The predictions of the string fragmentation model are found to give satisfactory agreements with the data clearly better than those of the cluster model To be submitted to Physics Letters B

The core of the TRIGA Mark II research reactor at the Vienna University of Technology/Atominstitut has been recently fully refurbished with new fuel, slightly irradiated. This new core configuration needs to be properly characterized in order to support future research activities. Aim of this work is to present the results of the measurements of the in-core neutron flux distribution and energy spectrum performed applying a method based on the synergetic use of the Monte Carlo code MCNP and of a de-convolution technique of activated foils. This method is very flexible and can be applied to characterize nuclear reactors that present a wide variability of core geometries, structural materials' compositions, fuel composition and neutron energy spectra. The method allows to measure both slow and fast neutron components proving as result a neutron spectrum in 620 energy groups. In the case of the measurements presented in this work, the absolute neutron flux was evaluated within an accuracy less than 10%.

The safety design of a nuclear reactor needs to maintain the steady state operation at desired power level. The safe and reliable reactor operation demands the complete knowledge of the core multiplication and its changes during the reactor operation. Therefore it is frequently of interest to compute the changes in core multiplication caused by small disturbances in the field of reactor physics. These disturbances can be created either by geometry or composition changes of the core. Fortunately if these changes (or perturbations) are very small, one does not have to repeat the reactivity calculations. This article focuses the study of small perturbations created in the Central Irradiation Channel (CIC) of the TRIGA mark II core to investigate their reactivity influences on the core reactivity. For this purpose, 3 different kinds of perturbations are created by inserting 3 different samples in the CIC. The cylindrical void (air), heavy water (D2O) and Cadmium (Cd) samples are inserted into the CIC separately to determine their neutronics behavior along the length of the core. The Monte Carlo N-Particle radiation transport code (MCNP) is applied to simulate these perturbations in the CIC. The MCNP theoretical predictions are verified by the experiments performed on the current reactor core. The behavior of void in the whole core and its dependence on position and water fraction is also presented in this article.

Burn up Calculations and Validation by Gamma Scanning of a TRIGA HEU Fuel (Page 148) R. Khan, S. Karimzadeh, H. Bock, M. Villa, and T Stummer The TRIGA Mark II research reactor operated by Atominstitut (Vienna/Austria) is one of the few TRIGA reactors, which still utilizes several High Enriched Uranium (HEU) Zirconium-Hydride (U-Zr-H) fuel elements. Its current core is a completely mixed core with 3 different types of fuel elements including one HEU type with 70 % enrichment and a stainless steel cladding. The present paper calculates the burn up of the FLIP (Fuel Lifetime Improvement Program) fuel using the burn up code ORIGEN2 and validates the theoretical results by high resolution gamma spectrometry using a unique fuel scanning device (FSD) developed at the Atominstitut especially for TRIGA fuel. For this purpose a FLIP fuel element was removed from the reactor core and stored in the research reactor pool for an appropriate cooling period. The fuel element was then transferred into the fuel scanning device to determine the Cesium-137 isotope distribution along the axis of the fuel element. The comparison between theoretical predictions and experimental results is the highlight of the present paper.

This paper presents an algorithm for numerical simulations of non-steady states of the TRIGA Mark II reactor in Vienna, Austria. The primary focus of this work has been the development of an algorithm which provides time series of integral neutron flux after reactivity changes introduced by perturbations without the usage of thermal-hydraulic/neutronic numerical code systems for the TRIGA reactor in Vienna, Austria. The algorithm presented takes into account both external reactivity changes as well as internal reactivity changes caused by feedback mechanisms like effects caused by temperature changes of the fuel and poisoning effects. The resulting time series have been compared to experimental results.

The Monet Carlo simulation of the TRIGA Mark II research reactor core has been performed employing the radiation transport computer code MCNP5. The model has been confirmed experimentally in the PhD research work at the Atominstitute (ATI) of the Vienna University of Technology. The MCNP model has been extended to complete biological shielding of the reactor including the thermal column, radiographic collimator and four beam tubes. This paper presents the MCNP simulated results in the thermal column and one of the beam tubes (beam tube A) of the reactor. To validate these theoretical results, thermal neutron flux density measurements using the gold foil activation method have been performed in the thermal column and beam tube A (BT-A). In the thermal column, the theoretical and experimental results are in fairly good agreement i.e. maximum thermal flux density in the centre decreases in radial direction. Further, it is also agreed that thermal flux densities in the lower part is greater than the upper part of the thermal column. In the BT-A experiment, the thermal flux density distribution is measured using gold foil. The experimental and theoretical diffusion lengths have been determined as 10.77cm and 9.36cm respectively with only 13% difference, reflecting good agreement between the experimental and simulated results. To save the computational cost and to incorporate the accurate and complete information of each individual Monte Carlo MC particle tracks, the surface source writing capability of MCNP has been utilized to the TRIGA shielding model. The variance reduction techniques have been applied to improve the statistics of the problem and to save computational efforts.

Gamma spectrometry is one of the common methods to inspect the spent fuel from research reactors. This method has been applied to in-pool measurements of the Spent Fuel Elements (SPEs) of the TRIGA Mark II research reactor. Due to mixed nature of the reactor core and complicated irradiation history of the fuel elements (FEs), the gamma spectrometry of the FE establishes improvements in the calculation and measurement of the SPE. In order to inspect the TRIGA SPE from dry storage and cooled fuel from the reactor pool, the selected spend fuels are scanned and measured using the fuel-scanning machine. Gamma spectrometry is performed by HPGe detector for spend fuel inspection and determination of the 137Cs activity and 134Cs/137Cs ratio. In this work, the steps of the detector calibration and the use of the Monte Carlo radiation transport code (MCNP5) have been described. In addition, the fuel-scanning machine and the gamma spectrometer are modelled by MCNP5 to simulate the gamma transport from fuel to detector. It also simulate the gamma spectrometer calibration for the burn up determination of the spend fuel. The results from MCNP5 simulation are applied to spectroscopic measurements and compared with the theoretical predictions of the neutronics code ORIGEN2 in this research work.

The Cesium (Cs-137) isotopic concentration due to irradiation of TRIGA Fuel Elements FE(s) is calculated and measured at the Atominstitute (ATI) of Vienna University of Technology (VUT). The Cs-137 isotope, as proved burn-up indicator, was applied to determine the burn-up of the TRIGA Mark II research reactor FE. This article presents the calculations and measurements of the Cs-137 isotope and its relevant burn-up of six selected Spent Fuel Elements SPE(s). High-resolution gamma-ray spectroscopy based non-destructive method is employed to measure spent fuel parameters. By the employment of this method, the axial distribution of Cesium-137 for six SPE(s) is measured, resulting in the axial burn-up profiles. Knowing the exact irradiation history and material isotopic inventory of an irradiated FE, six SPE(s) are selected for on-site gamma scanning using a special shielded scanning device developed at the ATI. This unique fuel inspection unit allows to scan each millimeter of the FE. For this purpose, each selected FE was transferred to the fuel inspection unit using the standard fuel transfer cask. Each FE was scanned at a scale of 1cm of its active length and the Cs-137 activity was determined as proved burn-up indicator. The measuring system consists of a high-purity germanium detector (HPGe) together with suitable fast electronics and on-line PC data acquisition module. The absolute activity of each centimeter of the FE was measured and compared with reactor physics calculations. The ORIGEN2, a one-group depletion and radioactive decay computer code, was applied to calculate the activity of the Cs-137 and the burn-up of selected SPE. The deviation between calculations and measurements was in range from 0.82% to 12.64%.

Distributions of event shape variables obtained from 120600 hadronic Z decays measured with the DELPHI detector are compared to the predictions of QCD based event generators. Values of the strong coupling constant c~ s are derived as a function of the renormalization scale from a quantitative analysis of eight hadronic distributions. The final result, c% (Mz) = 0.113 +_ 0.007, is based on second order perturbation theory and uses two hadronization corrections, one computed with a pat ton shower model and the other with a QCD matrix element model.

We describe microdosimetric measurements and simulations with Geant4 and FLUKA Monte Carlo codes in silicon and tissue. Analyses of deposited energy in sensitive volumes of some micrometers were carried out after exposure to heavy ion radiation.

A study of inclusive production of the meson resonances r!°, [{•o(892), f 0 (975) and f 2 (1270) in hadronic decays of the zo is presented. The measured mean meson multiplicity per hadronic event is 0.83 ± 0.14 for the (Jo, 0.64 ± 0.24 for the [{• (892), 0.10 ± 0.04 for the fo(975) in the momentum range p > 0.05Pbeam (xp > 0.05) and 0.11 ±0.05 for the fz(l270) for Xp > 0.1. These values and the corresponding differential cross sections 1/ O'hadr · dO' / dxp for the vector mesons are in good agreement with the predictions of the JETSET 7.3 PS and HERWIG 5.4 models. The fz(1270) production is overestimated by HER\VIG but its Xpshape is correctly reproduced. The measured ratios of the production cross sections 0'(!2(1270))/0'((Jo) = 0.22 ± 0.08 and 0'(!2(1270))/0'(!0 (975)) = 3~i for Xp > 0.1 are consistent with the results obtained in hadronic reactions. (Submitted to Physics Letters B)

A measurement of the strange quark forwardbackward asymmetry at the Z ~ peak was performed using 718,000 multihadronic Z ~ decays collected by the DELPHI detector at LEP in 1992. The s q u a r k was tagged by the presence of high momentum charged kaons identified by the Ring Imaging Cherenkov detector and by A~ decaying into pro-. The s q u a r k purity obtained was estimated for the two hadrons to be 43%. The average s q u a r k asymmetry was found to be 0.131 4, 0.035 (star.) 4. 0.013 (s~ls~.). The forward-backward asymmetry was measured for unresolved d and s quarks, tagged by the detection of a high energy neutron or neutral kaon in the Hadron Calorimeter. The combined d and s q u a r k purity was 69% and their asymmetry was found to be 0.112 40.031 (star.) 40.054 (syst.).

Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.

sion 7.2, giving: e (b) = (8 + ~ ___ 2)10 -3. The corresponding value of the mean fraction of the beam energy taken by a B hadron in the fragmentation of a b quark is: + 0 02 X~=0.69 0"03-t-0.01. If the values of F~ and F n are taken from the Standard Model, the following value is obtained for the mean semi-leptonic braching fraction of B hadrons" BR~I=(10.1 +0.7)%. Taking the value of Fb~/F n from an independent analysis of DELPHI data based on the use of the boosted sphericity product, a value: BRs~ =(10.1 -+ 1.3)% is obtained. 1 I n t r o d u c t i o n In the Standard Model the Z ~ boson couples with different strengths to up and down type quarks. Experimentally jets produced by heavy quarks are the easiest to isolate because of the use of characteristic properties of heavy hadron production and decay. In the present paper, semi-leptonic decays of B hadrons are used to isolate the Z ~ decays into bb pairs. Studying the distributions of the lepton energy and transverse momentum relative to the jet axis allows one to select this channel. This measurement provides a value for the coupling of the Z ~ to b quarks weighted by the mean semi-leptonic branching fraction of B hadrons. DELPHI has measured previously the fraction of b quarks produced in hadronic events using the distribution of an event shape variable, the boosted sphericity product [1], and also by studying the impact parameter distribution of charged tracks at the level of the beam interaction point [2]. Combining these measurements allows one to give a value for the mean semi-leptonic branching fraction of B hadrons produced in Z ~ decays. The lepton energy distribution is sensitive to the energy distribution of heavy hadrons and a comparison between data and Monte Carlo simulations allows the fragmentation distributions of the b quark to be studied. Leptons coming from the decays of charm particles do not have such distinctive features as leptons from direct B decays and with the present statistics only very crude measurements could be extracted on c g production. For this reason, in the following analysis, it was assumed that the production of c quarks is given by the Standard Model. After a description of the event selection and of the aspects of the apparatus that are relevant for this analysis, measurements obtained with selected data samples enriched in muons and in electrons are presented separately and then combined to get the final results. 2 D a t a a n d d e t e c t o r 2.1 Event selection and apparatus For this analysis, the sample of 120 K hadronic events recorded in DELPHI in 1990, were required to fulfill the following selection criteria: at least 7 reconstructed charged particles with momentum greater than 100 MeV/c; a total charged energy greater than 14% of the centre of mass energy; the thrust axis of the event at more than 32 ~ from the beam axis; the muon chambers had to be operational for the muon analysis; the barrel electromagnetic calorimeter (the HPC) had to be operational for the electron analysis. The resulting samples of about 100 K events were analyzed for the presence of electron and muon candidates. To define the solid angle covered by the detectors the following conventions were used. The z axis was taken along the electron beam direction and the y axis was vertical. Polar coordinates of a point in the transverse (x, y) plane were labeled R and ~. The 0 angle was used to define a direction relative to the z axis. The muon identification relied mainly on the muon chambers, a set of drift chambers providing three dimensional information. In the barrel part of the detector (52~ 0 < 128 ~ there are 3 sets of chambers (see Fig. 1). One set of chambers is located just inside the hadron calorimeter and two sets are just beyond it, with 2 layers I X ' ~ DELPHI InteraCtive Analysis i

The demand for installation and use of radiation monitors at border crossing points and other locations in a country has significantly increased due to fact that terrorist threats may also involve the use of radiation dispersal devices (RDDs, dirty bombs). One of the problems, customs officers and security forces run into is caused by passengers at airports having undergone a medical treatment, as they cause "innocent" radiation alarms with a high frequency. Since half-life of the isotopes, which are used for medical treatment, ranges from hours to several days, the dose-rate for several days and weeks after the treatment is high enough to trigger a radiation alarm of a border monitor. In this paper we describe the development and test of a real time gamma spectrometer, based on a commercially available large volume NaI detectors and a computer-coupled multi channel analyser (MCA) with fast data collection, stabilisation of the energy scale and isotope identification software. The system is capable of measuring a burst of gamma spectra in second intervals, to identify the isotopes and to produce a "green" alarm in real time when a medical isotope is present and a "red" alarm in other cases. The system has successfully been tested under laboratory conditions, as well as at an international airport and on patients of the radiation ward in hospitals. This work has been performed under IAEA Research Agreements between the Atom Institute of the Austrian Universities, the Austrian Research Center Seibersdorf and the International Atomic Energy Agency.