Forschungszentrum Karlsruhe Research Articles

^{74}Ge(n,gamma ) cross section below 70 keV measured at n_TOF CERN

Neutron capture reaction cross sections on ^{74}Ge are of importance to determine ^{74}Ge production during the astrophysical slow neutron capture process. We present new resonance data on ^{74}Ge(n,gamma ) reactions below 70 keV neutron energy. We calculate Maxwellian averaged cross sections, combining our data below 70 keV with evaluated cross sections at higher neutron energies. Our stellar cross sections are in agreement with a previous activation measurement performed at Forschungszentrum Karlsruhe by Marganiec et al., once their data has been re-normalised to account for an update in the reference cross section used in that experiment.

Mathematical efficiency calibration in gamma spectroscopy

Abstract Mathematical efficiency calibration with the LabSOCS software was introduced for two detectors in the measurement laboratory of the Central Safety Department of Forschungszentrum Karlsruhe. In the present contribution, conventional efficiency calibration of gamma spectroscopy systems and mathematical efficiency calibration with LabSOCS are compared with respect to their performance, uncertainties, expenses, and results. It is reported about the experience gained, and the advantages and disadvantages of both methods of efficiency calibration are listed. The results allow the conclusion to be drawn that mathematical efficiency calibration is a real alternative to conventional efficiency calibration of gamma spectroscopy systems as obtained by measurements of mixed gamma ray standard sources.

Assessment of ASTEC 2.1 capability to predict reactor core behaviour at the late phase of severe accident progression based on QUENCH-12

The presented paper discusses capability of recently developed version 2 revision 1, patch 1 of ASTEC computer code to predict a fuel behaviour at late phase of severe accident progression. The conducted assessment is part of the ASTEC validation based on available information from performed tests in QUENCH program for these purposes. It has been selected QUENCH-12 experiment for simulation of investigated phenomena as fuel cladding, oxidation and hydrogen generation, including temperature escalation during heat up followed by quenching overheated surface fuel cladding.The QUENCH-12 experiment was proposed by FZK together with RIAR Dimitrovgrad and IBRAE Moskow (Russia). The test was conducted at Forschungszentrum Karlsruhe on 27 December, 2006 in the frame of EC-supported ISTC program.The selected QUENCH-12 experiment was performed to extend knowledge gathered in previous QUENCH test to fuel behaviour in other LWRs slightly different from well investigated western type PWR with squared lattice. The fuel assemblies with a hexagonal lattice and containing fuel rod claddings made of Zr1%Nb (E 110) using in the VVER reactors are investigated in the experiment.The developed QUENCH-12 model for ASTEC code successfully predicted the entire sequence from initial heat-up to quench phase of experiment, except hydrogen generation during quenching phase at the end of transient.

TESTING THE IDEAS GUIDELINES AS APPLIED TO PLUTONIUM INTAKES.

The IDEAS Guidelines [Doerfel, H., et al General Guidelines for the Estimation of Committed Effective Dose from Incorporation Monitoring Data. Report FZKA 7243, Forschungszentrum Karlsruhe, GmbH (2006); Castellani, C. M., Marsh, J. W., Hurtgen, C., Blanchardon, E., Berard, P., Giusani, A. and Lopez, M. A. IDEAS Guidelines (Version 2) for the Estimation of Committed Doses from Incorporation Monitoring Data. EURADOS Report 2013-01, Braunschweig (2013)] provide a structured approach to the assessment of intakes of radionuclides. In order to check that the guidelines, when applied to typical monitoring programmes, lead to reliable assessments, a number of numerically-generated datasets have been constructed and assessed using the guidelines. The dose and intake obtained by the assessment can be compared with the 'true' dose and intake. In this way, the accuracy of the IDEAS assessment process can be examined when applied to monitoring programmes that are typically used in the nuclear industry. The simulations focus on assessments carried out as a result of elevated (239)Pu activities in routine urine samples, which lead to follow-up urine and faecal samples being provided. Cases where the assessor makes the correct initial assumption about lung solubility can be compared with cases where this initial choice is wrong. The results of these simulations and the implication for the use of monitoring programmes are discussed.

Assessment of the models in RELAP/SCDAPSIM with QUENCH-06 analysis

A fundamental principle of accident management in a nuclear power plant is the injection of water to cool the core. In this framework, a series of QUENCH tests have been conducted at Karlsruhe Institute of Technology (formerly Forschungszentrum Karlsruhe). The test results constitute a significant experimental database not only for further understanding of reflooding behavior, but also for code validation and improvement. The RELAP/SCDAPSIM code is a system code that is used to model reactor behavior and is widely used around the world. To date, assessment and validation have been performed with numerous experiments, including QUENCH tests. In the previous studies, the results of QUENCH simulations were referred to be sensitive to two main parameters: the electrical resistance and the thermal conductivity of the shroud insulator, which are subject to relatively large uncertainty. It is important to investigate these two parameters in detail, because this would enable identification of those SCDAP models that require further improvement. In this study, the uncertainty of the electrical resistance was reduced by modification of the code and subsequent validation with experimental data. In addition, modification of the thermal properties of the shroud insulator is suggested with consideration of the argon atmosphere in the facility. Finally, upcoming problems and questions are discussed. A rather good agreement was obtained than those of previous studies. As a result, more accurate modeling of the electrical resistance and the thermal properties of the shroud insulator was conducted and the importance of these parameters was evaluated.

Modelling of QUENCH-03 and QUENCH-06 Experiments Using RELAP/SCDAPSIM and ASTEC Codes

To prevent total meltdown of the uncovered and overheated core, the reflooding with water is a necessary accident management measure. Because these actions lead to the generation of hydrogen, which can cause further problems, the related phenomena are investigated performing experiments and computer simulations. In this paper, for the experiments of loss of coolant accidents, performed in Forschungszentrum Karlsruhe, QUENCH-03 and QUENCH-06 are modelled using RELAP5/SCDAPSIM and ASTEC codes. The performed benchmark allowed analysing different modelling features. The recommendations for the model development are presented.

Three-Dimensional Modeling of Debris Mixing and Sedimentation in Severe Accidents Using the Moving Particle Semi-Implicit Method Coupled with Rigid Body Dynamics

Particle mixing and sedimentation, related to corium debris bed formation and coolability in severe accidents, is investigated using a new computational fluid dynamics tool: the Analysis of Debris Dynamics and Agglomeration (ADDA) code. ADDA was developed based on an enhanced numerical method combining the moving particle semi-implicit algorithm with a rigid body dynamic model. The analysis successively simulates the entire process of debris bed formation, including corium jet breakup, mixing, and sedimentation. The methodology allows identification of key characteristics in the formation of the corium debris bed. Two-dimensional (2-D) and three-dimensional (3-D) simulations were utilized to model the detailed flow structures and mixing phenomena, along with the final sedimentation process, and were compared to the Q21 QUEOS test performed at Forschungszentrum Karlsruhe, Germany. For the analysis of debris bed formation, it is recommended that full 3-D simulations be utilized to provide enhanced accuracy related to corium debris field prediction. The 2-D simulations were found to be insufficient because of the debris field dependence on particle agglomeration and mixing, prior to debris settling.

Comparison of actinides and fission products recycling scheme with the normal plutonium recycling scheme in fast reactors

Multiple recycling of actinides and non-volatile fission products in fast reactors through the dry re-fabrication/reprocessing atomics international reduction oxidation process has been studied as a possible way to reduce the long-term potential hazard of nuclear waste compared to that resulting from reprocessing in a wet PUREX process. Calculations have been made to compare the actinides and fission products recycling scheme with the normal plutonium recycling scheme in a fast reactor. For this purpose, the Karlsruhe version of isotope generation and depletion code, KORIGEN, has been modified accordingly. An entirely novel fission product yields library for fast reactors has been created which has replaced the old KORIGEN fission products library. For the purposes of this study, the standard 26 groups data set, KFKINR, developed at Forschungszentrum Karlsruhe, Germany, has been extended by the addition of the cross-sections of 13 important actinides and 68 most important fission products. It has been confirmed that these 68 fission products constitute about 95% of the total fission products yield and about 99.5% of the total absorption due to fission products in fast reactors. The amount of fissile material required to guarantee the criticality of the reactor during recycling schemes has also been investigated. Cumulative high active waste per ton of initial heavy metal is also calculated. Results show that the recycling of actinides and fission products in fast reactors through the atomics international reduction oxidation process results in a reduction of the potential hazard of radioactive waste.

Availability measurement of grid services from the perspective of a scientific computing centre

The Karlsruhe Institute of Technology (KIT) is the merger of Forschungszentrum Karlsruhe and the Technical University Karlsruhe. The Steinbuch Centre for Computing (SCC) was one of the first new organizational units of KIT, combining the former Institute for Scientific Computing of Forschungszentrum Karlsruhe and the Computing Centre of the University. IT service management according to the worldwide de-facto-standard "IT Infrastructure Library (ITIL)" [1] was chosen by SCC as a strategic element to support the merging of the two existing computing centres located at a distance of about 10 km.The availability and reliability of IT services directly influence the customer satisfaction as well as the reputation of the service provider, and unscheduled loss of availability due to hardware or software failures may even result in severe consequences like data loss. Fault tolerant and error correcting design features are reducing the risk of IT component failures and help to improve the delivered availability. The ITIL process controlling the respective design is called Availability Management [1]. This paper discusses Availability Management regarding grid services delivered to WLCG and provides a few elementary guidelines for availability measurements and calculations of services consisting of arbitrary numbers of components.

Performance testing of engineered corium cooling systems

Abstract The coolability of ex-vessel core debris continues to be an issue of concern in the realm of light water reactor safety. Extensive research into corium/concrete interaction phenomena has been unable to establish the certainty of melt quench and stabilization within the containment boundary for all credible cases of cooling restricted to top flooding. As a result, there has been continuing interest in engineered systems that can augment cooling. This paper describes the testing of two passive cooling concepts that inject water into corium from below via nozzles embedded within the basemat: one with porous concrete nozzles and the other with a type of composite nozzle. The latter supplements water injection with noncondensable gas to stabilize flow and suppress vapor explosions. Each test involved a 136 kg melt composed of 56/23/14 wt% UO 2 /ZrO 2 /siliceous concrete at an initial depth of 30 cm. The setup with the porous concrete nozzles successfully injected water into the melt at heads as low as 2.3 m. The composite nozzle test was partially successful, with three nozzles delivering coolant while a fourth was damaged by the melt and failed to inject water. The melts cooled twice as fast as similar ones tested in a top flooding configuration. These experiments confirmed earlier work at Forschungszentrum Karlsruhe and elsewhere indicating that cooling via bottom water injection is a particularly effective method for quenching ex-vessel corium melts.

Test Results of the High Temperature Superconductor Prototype Current Leads for Wendelstein 7-X

The Karlsruhe Institute of Technology (which is a merger of former Forschungszentrum Karlsruhe and Karlsruhe University) is responsible for the design, construction and testing of the high temperature superconductor (HTS) current leads for the stellarator Wendelstein 7-X (W7-X) which is presently under construction at the Greifswald branch of the Max-Planck-Institute for Plasma Physics. The current leads are of the binary type, the HTS part covering the temperature range between 4.5 K and 60 K while the heat exchanger covers the range between 60 K and room temperature being cooled by 50 K He. In total 2 prototypes and 14 series current leads are required with a nominal current of 14 kA and a maximum current of 18.2 kA. The paper describes the design and first test results of the prototype HTS current leads.

KIT induced activities to support fabrication, assembly and qualification of technology for the HCPB-TBM

Fabrication concepts for the Helium Cooled Pebble Bed Test Blanket Module have been developed for more than one decade in the KIT (the former Forschungszentrum Karlsruhe). In accordance to the progressing design verification, key technology of fabrication and assembly need to be transferred from experimental scale to industrial application in relevant dimensions taking into account the requirements for qualification of processes. This paper describes fabrication development activities of the KIT recently started or planned to be performed in the near future. Several developments described in this paper are a continuation of activities done in the framework of EFDA/F4E contracts. Others will continue KIT (FZK) self financed developments. The general scope is to identify development needs and to minimize the risk in transfer and scale up of process parameters, already developed for small- and lab-scale fabrication Mock Ups, to bigger dimensions. This will provide the link between the present status (the experimental stage of welding) and the planned mid-term future activities, to define preliminary Welding Procedure Specifications (pWPS) for Mock Ups in TBM relevant size in collaboration with industry by prototypical Mock Ups.

High temperature superconductor current leads for fusion machines

All large fusion experimental machines presently under construction like the tokamak ITER, the stellarator Wendelstein 7-X (W7-X), and the satellite tokamak JT-60SA will use high temperature superconductor (HTS) current leads to reduce the cryogenic load and operational cost. The Karlsruhe Institute of Technology (KIT which is a merger of former Forschungszentrum Karlsruhe and University Karlsruhe) designed, constructed and successfully tested a 68 kA HTS current lead demonstrator for ITER which led to the decision by ITER IO to use HTS current leads for the ITER magnet system, and the Chinese Domestic Agency is in charge of providing these leads as a part of the superconducting feeder system. KIT is in charge of design, construction and test of HTS current leads for W7-X and JT-60SA. The paper discusses the status of the current lead development and describes the results of the W7-X prototype test which has been performed recently.

This Special Issue of Microsystem Technologies is devoted to Professor Dr.-Ing. Jürgen Haußelt on the occasion of his 65th birthday

Professor Dr.-Ing. Jurgen Hauselt, for many years the Head of the Institute of Materials Research III at the Forschungszentrum Karlsruhe, today Karlsruhe Institute of Technology (KIT), and also Professor and Head of the Laboratory of Materials Process Technology at the University of Freiburg will be celebrating his 65th birthday on May 21, 2011. His outstanding professional career features about 16 years of work in industry and 24 years in science and teaching at academic and research institutions. Jurgen Hauselt studied physics at the University of Erlangen-Nurnberg in Bavaria, Germany, and finished his diploma thesis in 1971. Under the guidance of the Professors Bernhard Ilschner and Wolfgang Blum at the Institute of Materials Science of the university he accomplished a PhD thesis on the recovery of the dislocation structure after stationary deformation with an Al-Zn alloy. After being awarded his doctoral degree (Dr.-Ing.) in 1975, he worked as a scientific assistant at this institute and during this time he took a year-long sabbatical for a postdoc position with Prof. W.D. Nix at Stanford University, USA. Back from the USA, Jurgen Hauselt started his industrial career in July 1977 as group leader in the Metal Research Department of Degussa AG at Hanau-Wolfgang, Germany. At the beginning he worked on the development of new alloys for dental and brazing technologies. In 1983 he became the Technical Director of Degussa Dental, Inc. at Long Island City, USA. As consequence of his remarkable success, he was promoted in November 1984 to the position of the division manager ‘Metallurgy’ at Degussa-Metal Research at Hanau-Wolfgang. The next steps of his career at Degussa had been appointments to a department head in 1987 connected with an enlargement of responsibilities for electronic materials, thin film materials and structural ceramics and in 1989 to the department director ‘‘Manufacturing Technology’’ with responsibility for the Central Research ‘‘Metal’’ which included melting and casting techniques as well as metal forming and powder metallurgy. A new phase of Jurgen Hauselt’s life began on October 1, 1993 with the acceptance of the position of Head of the Institute of Materials Research III at the Kernforschungszentrum Karlsruhe which was renamed Forschungszentrum Karlsruhe in 1995. In 1996 he was additionally appointed Professor and Head of the Laboratory of Materials Process Technology at the Department of Microsystems Engineering (IMTEK) at the University of Freiburg. Promoted by the two appointments of Jurgen Hauselt, a close scientific and personal cooperation of both institutions has developed in the field of Microsystems Technology, particularly. Credit is due to him also for his considerable contribution as vice-spokesman to the formation of the DFG-Collaborative Research Centre 499 ‘‘Design, production and quality assurance of moulded microcomponents made of metallic and ceramic materials’’. By reason of his outstanding scientific competence in several fields of materials science and process technologies for microsystems but also due to his charismatic and engaging personality, his membership in numerous executive and scientific committees has been very much appreciated. Beside his manifold activities in the science community and as a university professor, Jurgen Hauselt K.-H. Zum Gahr (&) Karlsruhe Institute of Technology, Karlsruhe, Germany e-mail: karl-heinz.zumgahr@kit.edu

Application of high temperature superconductors for fusion

The use of High Temperature Superconductor (HTS) materials in future fusion machines can increase the efficiency drastically. For ITER, W7-X and JT-60SA the economic benefit of HTS current leads was recognized after a 70 kA HTS current lead demonstrator was designed, fabricated and successfully tested by Karlsruhe Institute of Technology (KIT, which is a merge of former Forschungszentrum Karlsruhe and University of Karlsruhe). For ITER, the Chinese Domestic Agency will provide the current leads as a part of the superconducting feeder system. KIT is in charge of design, construction and test of HTS current leads for W7-X and JT-60SA. For W7-X 14 current leads with a maximum current of 18.2 kA are required that are oriented with the room temperature end at the bottom. JT60-SA will need 26 current leads (20 leads @ 20 kA and 6 leads @ 25.7 kA) which are mounted in vertical, normal position. These current leads are based on BiSCCO HTS superconductors, demonstrating that HTS material is now state of the art for highly efficient current leads. With respect to future fusion reactors, it would be very promising to use HTS material not only in current leads but also in coils. This would allow a large increase of efficiency if the coils could be operated at temperatures ≥65 K. With such a high temperature it would be possible to omit the radiation shield of the coils, resulting in a less complex cryostat and a size reduction of the machine. In addition less refrigeration power is needed saving investment and operating costs. However, to come to an HTS fusion coil it is necessary to develop low ac loss HTS cables for currents well above 20 kA at high fields well above 10 T. The high field rules BiSCCO superconductors out at temperatures above 50 K, but RE-123 superconductors are promising. The development of a high current, high field RE-123 HTS fusion cable will not be targeted outside fusion community and has to be in the frame of a long term development programme for DEMO. KIT has already demonstrated a scalable concept using RE-123 HTS tapes that are assembled to Roebel type conductors. This concept can be expanded to form Rutherford cables as starting point for a development of a high current fusion cable. The status and prospect of using HTS conductors for fusion is discussed.

THE EXTENSIVE AIR SHOWER EXPERIMENT KASCADE-GRANDE

The extensive air shower experiment KASCADE-Grande (KArlsruhe Shower Core and Array DEtector and Grande array) is located on site of the Forschungszentrum Karlsruhe in Germany. The original KASCADE experiment consisted of a densely packed scintillator array with unshielded and shielded detectors for the measurement of the electromagnetic and muonic shower component independently, as well as muon tracking devices and a hadron calorimeter. The Grande array as an extension of KASCADE consists of 37 scintillation detector stations covering an area of 700×700 m2. The main goal for the combined measurements of KASCADE and Grande is the investigation of the energy spectrum and composition of primary cosmic rays in the energy range of 1016 to 1018 eV. In this paper an overview of the KASCADE-Grande experiment and recent results will be presented.

Preliminary thermal design and related DEMO relevancy of the EU-HCPB TBM in vertical arrangement

In the frame of the activities of the European Test Blanket Module Consortium of Associates the Helium-Cooled Pebble-Bed Test Blanket Module (HCPB TBM) is developed in Forschungszentrum Karlsruhe (FZK) to investigate DEMO relevant concepts for blanket modules. A series of four different HCPB TBMs of the EU will be installed into the ITER Vacuum Vessel connected to one dedicated equatorial port. During different test campaigns, the 4 TBMs will test the three main functions of a blanket module (removing heat, breeding tritium and shielding sensitive components from radiation). In 2006–2007 a preliminary version of the HCPB TBM sub-components design has been proposed extrapolating the neutronic analyses performed for the horizontal HCPB TBM. With the input data provided by the preliminary design, together with the ITER 3D 40° toroidal sector model, new nuclear analyses for the vertical HCPB TBM have been performed. Nuclear results are necessary to assess the sub-components design and to validate the design of the HCPB TBM: with this aim thermal analyses of a 1/4 scaled assembly of the vertical HCPB TBM have been performed. As the generation of data in ITER supporting the design of DEMO is very important in the road map to the commercial fusion reactor, the results of nuclear and thermal analyses are fundamental to perform studies concerning the TBM DEMO relevancy.

Air oxidation of Zircaloy-4 in the 600–1000 °C temperature range: Modeling for ASTEC code application

Progress in the treatment of air oxidation of zirconium in severe accident (SA) codes are required for a reliable analysis of severe accidents involving air ingress. Air oxidation of zirconium can actually lead to accelerated core degradation and increased fission product release, especially for the highly-radiotoxic ruthenium. This paper presents a model to simulate air oxidation kinetics of Zircaloy-4 in the 600–1000 °C temperature range. It is based on available experimental data, including separate-effect experiments performed at IRSN and at Forschungszentrum Karlsruhe. The kinetic transition, named “breakaway”, from a diffusion-controlled regime to an accelerated oxidation is taken into account in the modeling via a critical mass gain parameter. The progressive propagation of the locally initiated breakaway is modeled by a linear increase in oxidation rate with time. Finally, when breakaway propagation is completed, the oxidation rate stabilizes and the kinetics is modeled by a linear law. This new modeling is integrated in the severe accident code ASTEC, jointly developed by IRSN and GRS. Model predictions and experimental data from thermogravimetric results show good agreement for different air flow rates and for slow temperature transient conditions.

Fuel Pin Behavior up to Cladding Failure under Pulse-Type Transient Overpower in the CABRI-FAST and CABRI-RAFT Experiments

In the CABRI-FAST and CABRI-RAFT programs within a collaboration with the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) and Forschungszentrum Karlsruhe (FZK), five pulse-type transient overpower tests were performed in order to study fuel pin behavior and failure condition in the Unprotected Loss-of-Flow (ULOF) accident. In these tests, two types of low-smear-density fuels irradiated in the French Phénix reactor at different burn-up levels were used so that an experimental database extension from the former CABRI-1 and CABRI-2 programs can be obtained. Pin failure took place in three of these tests giving information on the failure threshold. In two tests, no pin failure took place and useful information related to the transient fuel behavior up to failure and failure mechanism was obtained. These test results were interpreted through detailed analysis of experimental data and PAPAS-2S code calculations. In these calculations, pretransient fuel characteristics obtained from the sibling fuels were reflected, such that the uncertainty of the boundary condition can be minimized. Through the comparison among these tests and formerly existing CABRI tests, generalized understanding on the transient fuel behavior was obtained. It was concluded that the low-smear-density fuel mitigates cavity pressurization, thereby enhancing the margin-to-failure. It was also understood that this failure-thresholdenhancing capability is dependent on the type of transient.

German contributions to the CMS computing infrastructure

The CMS computing model anticipates various hierarchically linked tier centres to counter the challenges provided by the enormous amounts of data which will be collected by the CMS detector at the Large Hadron Collider, LHC, at CERN. During the past years, various computing exercises were performed to test the readiness of the computing infrastructure, the Grid middleware and the experiment's software for the startup of the LHC which took place in September 2008. In Germany, several tier sites are set up to allow for an efficient and reliable way to simulate possible physics processes as well as to reprocess, analyse and interpret the numerous stored collision events of the experiment. It will be shown that the German computing sites played an important role during the experiment's preparation phase and during data-taking of CMS and, therefore, scientific groups in Germany will be ready to compete for discoveries in this new era of particle physics. This presentation focuses on the German Tier-1 centre GridKa, located at Forschungszentrum Karlsruhe, the German CMS Tier-2 federation DESY/RWTH with installations at the University of Aachen and the research centre DESY. In addition, various local computing resources in Aachen, Hamburg and Karlsruhe are briefly introduced as well. It will be shown that an excellent cooperation between the different German institutions and physicists led to well established computing sites which cover all parts of the CMS computing model. Therefore, the following topics are discussed and the achieved goals and the gained knowledge are depicted: data management and distribution among the different tier sites, Grid-based Monte Carlo production at the Tier-2 as well as Grid-based and locally submitted inhomogeneous user analyses at the Tier-3s. Another important task is to ensure a proper and reliable operation 24 hours a day, especially during the time of data-taking. For this purpose, the meta-monitoring tool "HappyFace", which was developed at the University of Karlsruhe, is used in order to allow even non-expert shift crews to monitor and operate a centre continuously and to contact on-call experts, if needed.