Karlsruhe Nuclear Research Center Research Articles

Neutron Interactions with 3He Revisited–III: Neutron Cross Sections between 24 and 30 MeV

The relative yield excitation functions of neutron-3He elastic cross sections reported in 1982 by the Karlsruhe (Germany) Nuclear Research Center were converted into consistent angle-dependent absolute differential cross sections at 24, 27, and 30 MeV by constructing the elastic cross sections from the total cross sections and the nonelastic cross sections and using them as constraint. This work presents absolute differential cross sections of the elastic and of the two-body nonelastic reactions up to 30 MeV together with reliable estimates of the breakup cross sections. It makes neutron cross-section data of all neutron-3He reactions up to 30 MeV available, expanding the energy range of the data given in Parts I and II.

Thirty years of LWR safety research at Karlsruhe

When nuclear power plants equipped with light water reactors (LWR) became commercialized, the German federal government from the mid-60s on increasingly supported initiatives in reactor safety research at national research centers, universities, and in industry. At the Karlsruhe Nuclear Research Center, this resulted in the establishment of the Nuclear Safety Project in early 1972 as the administrative focus of various research and development (R&D) activities in LWR safety to be further extended. In the seventies, the related R&D program concentrated on the quantification of safety margins in nuclear power plants, mainly derived from investigations into the loss-of-coolant accident (‘deterministic approach’). In the 80s, the program consisted of major contributions to safety analyses for incorporation into the German Risk Study which were based on hypothetical sequences of core meltdown accidents (‘probabilistic approach’). The program in the nineties was devoted to an advanced quality in safety as required for future nuclear power plants by the German Atomic Energy Act as amended in 1994. This new quality was based on complementary preventive and mitigative safety installations against accidental releases of radioactive materials. The paper concludes with a glimpse at the current situation of nuclear electricity generation in Germany and, in this connection, aspects of competence preservation in the field of nuclear safety.

The German fast breeder program (a historical overview)

Basic and technology programs on German fast breeder reactor (FBR) research were launched by the government and industry in the sixties. At the Karlsruhe Nuclear Research Center (KfK), the 20-MWe sodium-cooled KNK experimental nuclear power station was built by INTERATOM. It was operated successfully until 1991. A German–Belgian–Netherlands consortium was responsible for planning and building the SNR 300, a 300-MWe prototype breeder, in Kalkar. For political reasons, the plant was never commissioned; it was stopped in 1991. In the nineties, Germany together with France and the United Kingdom participated for some time in the development of the European Fast Reactor (EFR).

The KASCADE cosmic ray experiment

KASCADE is an extensive air shower experiment under construction in the Karlsruhe Nuclear Research Centre. Its main aim is to measure primary cosmic ray composition above the range where direct measurements are possible. The experiment will register a larger number of observables for each individual shower than previous ones and should be able to distinguish at least three groups of primaries: the light elements (p, He), the C-N-O and the iron groups.

High-precision readout circuit for LIGA acceleration sensors

Abstract For the past few years capacitive LIGA acceleration sensors have been fabricated at the Karlsruhe Nuclear Research Center. The advantages of LIGA acceleration sensors are their high zero-acceleration capacitance of 5 pF, temperature-compensated design with low offset temperature coefficient (TCO = 1.5 × 10−4 FSO K−1) and high linearity. In addition, a high-precision readout circuit has been developed. The electronic circuit's distinguishing feature is its extremely low noise, so that capacitance changes of 5 aF Hz −1 2 can be detected. Combined with a 1g LIGA acceleration sensor, a resolution of 1μg Hz −1 2 has been achieved. A feedback system has been developed for a further improvement of linearity. The electronic circuit has been realized as a multichip module (MCM) in multilayer thick-film technique on a 10 mm × 20 mm Al2O3 substrate. The final result is a sensor system with excellent properties as regards temperature behaviour, dynamic range and resolution.

Microfluidic components in LIGA technique

The transport of small amounts of fluids and gases must be controlled with a view to automated drug dosage, chemical analysis with microsensors, and hydraulic as well as pneumatic microactuators. Components for microfluidic systems have been developed at Karlsruhe Nuclear Research Center which are manufactured by the LIGA technique. Micropumps have been fabricated by combining thermoplastic molding with membrane techniques. It is envisaged to integrate these micropumps into a module for handling gases and liquids. The module can then be coupled with different sensor modules to form microsystems, e.g. for the detection of toxic chemicals in the environment or for bedside analysis in hospitals. Microvalve systems and fluidic beam amplifiers have been developed for hydraulic and pneumatic actuators. These devices are capable of controlling a liquid or gas stream and may be used to steer e.g. instruments in a catheter tip for minimally invasive surgery.

Microstructure technologies and their potential in medical applications.

One of the major fields of application of microstructure technology and microsystems technology will probably be centered in medical engineering. Above all in neurosurgery, highly sophisticated surgical instruments featuring high functionality combined with high reliability are needed. Products fabricated by conventional manufacturing technologies can fulfill these demanding requirements only to a limited extend. At the Karlsruhe Nuclear Research Center first prototype components such as microspectrometers, microturbines and microfluidics structures are presently fabricated and tested which can be used in future microendoscopes as sensors or actuators. Combined with adequate information processing and suitable interface technology, it will be possible to create microsystems for various medical applications.

Testing of elastomer-sealed, dust-contaminated vacuum valves

Within the framework of the European Fusion Programme a contract has been awarded to the Karlsruhe Nuclear Research Centre for the investigation of the compatibility with graphite dust of the elastomer-sealed vacuum valves under tokamak operating conditions. Three types of elastomer seal (VITON, BUNA-N and EPDM) are investigated in the SPARTA test facility. A seal tightness of <10 −6 mbar l s −1 is measured despite dust loading of up to 80% and a particle mean diameter of the dust agglomerates of up to 100 ωm. The experimental results obtained are discussed in this paper.

Results of the verification period 1985–1990 of the German-Swiss high converting reactor PWR-C1

Abstract A high converting reactor (HCR), the PWR-C1, is described, which was developed on the basis of the commercially proven pressurized water reactor (PWR) technology by Siemens AG Power Generation Group in cooperation with the Karlsruhe Nuclear Research Center (KfK), the Paul Scherrer Institute at Wurenlingen (PSI) and the Technical University of Braunschweig (TUBS). The essential features of the concept in comparison to the conventional Konvoi-reactor core are a triangular fuel pin lattice with a tighter pitch and a higher density of control assemblies. The main goal was a better fuel utilization, which was achieved mainly by hardening of the neutron energy spectrum. Because of the lower moderation ratio due to the tighter pitch, the neutron spectrum is shifted into the epithermal energy range, whereby the conversion rate is augmented, from 0.35 for a Konvoi-reactor core to 0.75 for a PWR-C1. The PWR-C1 concept is the result of extensive investigations of tight and very tight fuel pin lattices, concerning neutron physics, thermohydraulics, emergency cooling and mechanical design. For establishment and improvement of codes several experiments were performed in the mentioned areas; (1) the PROTEUS experiments for physics investigations at PSI Wurenlingcon, (2) the CHF experiments at Siemens Karlstein and KfK, and (3) the NEPTUN and FLORESTAN flooding experiments at PSI and KfK. All these experiments led to the validation or improvement of codes and/or the verification of calculational methods. Also methods used in conventional design activities could be improved. The investigations in mechanical design too led to results, which partly are of great use for conventional design work.

Technologies for Sustained Development A New Task for Big Science

AbstractThe Karlsruhe Nuclear Research Centre is one of the two largest research establishments in Germany, employing more than 4200 persons. Over the past decade, the emphasis of the work carried out has increasingly shifted to embrace non-polluting high technologies. An overview of these research activities, which form the basis of the other contributions to this special issue, is presented under the groupings: environmental research; energy research; microsystems technology; and fundamental physical research.

Superconductivity for Energy Technology

Abstract Investigations of applications of the attractive properties of superconductors in energy technology started in principle with the discovery of practical conductors about 25 years ago. The Karlsruhe Nuclear Research Centre has been active in parts of this area for about 15 years. As this paper describes, the potential applicability covers most of the well known fields of electrical power engineering, such as motors, power transmission cables and transformers, and novel devices such as superconducting energy storage systems and fault current limiters also become feasible. However, the complexity of superconductivity technology sets technical and economic limits to the use of this technology in all these areas. A major component is the superconductor itself, which has to meet stringent operating conditions. There is no doubt that the potential for superconductor applications in energy technology will greatly increase when, besides the already well developed classical superconductors with liquid heli...

Superconductivity for Energy Technology

Investigations of applications of the attractive properties of superconductors in energy technology started in principle with the discovery of practical conductors about 25 years ago. The Karlsruhe Nuclear Research Centre has been active in parts of this area for about 15 years. As this paper describes, the potential applicability covers most of the well known fields of electrical power engineering, such as motors, power transmission cables and transformers, and novel devices such as superconducting energy storage systems and fault current limiters also become feasible. However, the complexity of superconductivity technology sets technical and economic limits to the use of this technology in all these areas. A major component is the superconductor itself, which has to meet stringent operating conditions. There is no doubt that the potential for superconductor applications in energy technology will greatly increase when, besides the already well developed classical superconductors with liquid helium cooling, high temperature superconductors for use at liquid nitrogen temperature become available with the necessary properties for these applications. As shown, for some applications, power transmission cables for example, only with cooling temperatures ≥77 K will the use of superconductors have the possibility of becoming economic. Another critical design area is high voltage components in cryogenic environments, where specific techniques are needed. In spite of advanced experimental results for several applications such as generators and energy storage systems, commercial implementation will take another decade at least.

Nuclear Fusion Technology

Abstract Nuclear fusion is a physical process in which the nuclei of heavy hydrogen atoms (deuterium, tritium) are united by fusion to become an atomic nucleus of helium while releasing large amounts of energy. The energy emitted by the Sun is generated by nuclear fusion. In nuclear fusion research, reproduction of that process in a technical scale device, the fusion reactor, at high temperatures, is attempted. In this review a short outline is given of the national, European and worldwide technology programmes initiated during the last decade. The contributions which the Karlsruhe Nuclear Research Centre makes to these programmes on the basis of experience accumulated over several decades are described. The cooperation of specialists from various disciplines in the two central activities of magnet technology and the nuclear part of the fusion reactor, the so called blanket, is described more fully. In conclusion, the most important milestones on the way to the commercial fusion reactor are indicated, and...

Nuclear Fusion Technology

Nuclear fusion is a physical process in which the nuclei of heavy hydrogen atoms (deuterium, tritium) are united by fusion to become an atomic nucleus of helium while releasing large amounts of energy. The energy emitted by the Sun is generated by nuclear fusion. In nuclear fusion research, reproduction of that process in a technical scale device, the fusion reactor, at high temperatures, is attempted. In this review a short outline is given of the national, European and worldwide technology programmes initiated during the last decade. The contributions which the Karlsruhe Nuclear Research Centre makes to these programmes on the basis of experience accumulated over several decades are described. The cooperation of specialists from various disciplines in the two central activities of magnet technology and the nuclear part of the fusion reactor, the so called blanket, is described more fully. In conclusion, the most important milestones on the way to the commercial fusion reactor are indicated, and the critical problems faced in development of the technology are pointed out.

High Temperature Superconductors From Basic Research to Technology

This paper reviews R&D activities at Karlsruhe Nuclear Research Centre carried out in the field of superconductivity, covering the whole spectrum between fundamental research and superconductor development preceding application. Particular emphasis is laid on cuprate high Tc superconductors. Topics covered include electronic structure, lattice dynamics, thermodynamic properties, thin films, critical currents, wires and tapes, and texturised bulk materials with a high flux trapping capability.

The Kascade Cosmic Ray Experiment

AbstractKascade is a large detector which is being built on the site of the Karlsruhe Nuclear Research Centre to study extensive air showers initiated by high energy cosmic ray particles in the atmosphere. The aim of the experiment is to obtain information about the chemical composition of primary cosmic rays in the energy range 500 TeV to 10 PeV, where little if anything is known at present. Special features of Kascade, as compared with previous experiments on extensive air showers, are the capability of registering many variables of a shower simultaneously and a very high rate of sampling. The design of the experiment, its present status and predicted performance are described.

Variances of the vertical and horizontal wind measured by tower instruments and SODAR

At the Karlsruhe Nuclear Research Center, a monostatic Doppler SODAR has been operated near a 200 m high meteorological tower. Vertical profiles of the components of the wind vector and of the variances of the vertical wind and of the horizontal wind direction have been sampled continuously from the SODAR and the tower instruments as 30-min mean values. During seven episodes lasting more than 2 h, the instantaneous vertical wind speed was measured simultaneously by a sonic anemometer and the SODAR, and spectra were calculated. An intercomparison of the spectra and wind data measured directly by the SODAR and the tower instruments has been performed by a linear regression and correlation analysis referring to different height levels of measurement and stability classes.

Gas to gas heat transfer in micro heat exchangers

By the method of mechanical manufacture of microstructures jointly developed by the Karlsruhe Nuclear Research Center (KfK) and Messerschmitt-Bölkow-Blohm (MBB) very compact cross-flow micro heat exchangers have been fabricated whose active volumes are 1 × 1 × 1 cm 3 and whose typical channel cross-sections are 75 × 90 μm 2. Measurements with nitrogen, argon and helium as heat transfer fluids were performed on two copper and stainless steel finned plate heat exchangers. With the stainless steel heat exchanger overall heat transfer coefficients up to 1700 W m −2 K −1 have been attained in the range investigated using helium as the fluid. For low flow rates greatly reduced overall heat transfer coefficients have been measured compared with the values to be anticipated for laminar flow. In some ranges higher heat transfer rates have been achieved with the stainless steel heat exchanger compared with the system made from copper. This leads to the conclusion that the heat transfer behavior for low gas flow rates is largely determined by heat conduction in the longitudinal direction within the wall and fin materials. With a homogeneous model the influence of longitudinal heat conduction in the stationary walls can be explained and is in fairly good agreement with the experimental data.

Experimental Investigations of Helium Cryotrapping by Argon Frost (Status report)

AbstractAt the Karlsruhe Nuclear Research Centre (KfK) cryopumping techniques are being investigated by which the gaseous exhausts from the NET/ITER reactor can be pumped out during the burn-and dwell-times. Cryosorption and cryotrapping are techniques which are suitable for this task. It is the target of the investigations to test the techniques under NET/ITER conditions and to determine optimum design data for a proto-type. They involve measurement of the pumping speed as a function of the gas composition, gas flow and loading condition of the pump surfaces. The following parameters are subjected to variations: Ar/He ratio, specific helium volume flow rate, cryosurface temperature, process gas composition, impurities in argon trapping gas, three-stage operation and two-stage operation. This paper is a description of the experiments on argon trapping techniques started in 1990.1, 2 Eleven tests as well as the results derived from them are described. The general potential of helium cryotrapping by argon w...

Dynamic tritium inventory of a NET/ITER fuel cycle with lithium salt solution blanket

At the Karlsruhe Nuclear Research Center (KfK) a flexible tool is being developed to simulate the dynamics of tritium inventories. This tool can be applied to any tritium handling system, especially to the fuel cycle components of future nuclear fusion devices. This instrument of simulation will be validated in equipment to be operated at the Karlsruhe Tritium Laboratory. In this study tritium inventories in a NET/ITER type fuel cycle involving a lithium salt solution blanket are investigated. The salt solution blanket serves as an example because it offers technological properties which are attractive in modeling the process; the example does not impair the general validity of the tool. Usually, the operation strategy of complex structures will deteriorate due to failures of the subsystems involved. These failures together with the reduced availability ensuing from them will be simulated. The example of this study is restricted to reduced availabilities of two subsystems, namely the reactor and the tritium recovery system. For these subsystems the influence of statistically varying intervals of operation is considered. Strategies were selected which are representative of expected modes of operation. In the design of a fuel cycle, care will be taken that prescribed availabilities of the subsystems can be achieved; however, the description of reactor operation is a complex task since operation breaks down into several campaigns for which rules have been specified which enable determination of whether a campaign has been successful and can be stopped. Thus, it is difficult to predict the overall behavior prior to a stimulation which includes stochastic elements. Using the example mentioned above the capabilities of the tool will be illustrated; besides the presentation of results of inventory simulation, the applicability of these data will be discussed.