摘要:

AbstractA general view is given of the significance and practical application of critical experiments for design and development of high-temperature gas-cooled reactor (HTGR) pebble-bed cores, mainly in the Federal Republic of Germany. Some experimental results are presented, and the theoretical methods that are used to evaluate different effects are discussed. The main target seems to be attained; for HTGR pebble-bed cores, reliable methods for nuclear design are available.

ISSN:0029-5639    

DOI:10.13182/NSE87-A23490

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractA simple method has been developed for treating large cylindrical empty and rodded void regions in high-temperature gas-cooled reactors with each existing diffusion code. The cavity is treated as a diffusion region with zero reaction cross sections. Only diffusion constants, found by an optimization process, are used.Verification of this model is done by comparing results with transport solutions for identical problems. Very good agreement is attained when anisotropic diffusion is foreseen in the diffusion code. Even with isotropic diffusion, however, eigenvalues and rod reactivities proved to be acceptable.This treatment yields usual diffusion running times and allows three-dimensional calculations.

ISSN:0029-5639    

DOI:10.13182/NSE87-A23491

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractAn emergency shutdown system for high-temperature gas-cooled pebble-bed reactors is proposed in addition to the common absorber rod shutdown system. This system is based on the strongly absorbing effect of small boronated graphite spheres (called KLAK), which trickle in case of emergency by gravity from the top reflector into the reactor core.The inner reflector of the Siemens-Argonaut reactor was substituted by an assembly of spherical Arbeitsgemeinschaft Versuchsreaktor fuel elements, and the shutdown effect was examined by installing well-defined KLAK nests inside this assembly. The purpose was to develop and prove a calculational procedure for determining criticality values for assemblies of large fuel spheres and small absorbing spheres.

ISSN:0029-5639    

DOI:10.13182/NSE87-A23492

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe critical facility KAHTER was used to verify and to adjust theoretical models describing the physics of pebble-bed high-temperature gas-cooled reactors. Using methods such as evaluating critical masses, flux mappings, and reaction rate measurements, more sophisticated experimental and theoretical methods have been developed to get exact information and interpretation of control rod efficiency, power determination, and fast neutron damage.

ISSN:0029-5639    

DOI:10.13182/NSE87-A23493

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractSeveral fuel-loading concepts are proposed for high-temperature reactors of the pebble-bed type. A very promising one is the so-called OTTO (once through then out) loading scheme. Some of the intrinsic features of OTTO fuel loading are the axial nonsymmetrical power and neutron flux distribution with a pronounced maximum at the upper reactor core region. Since the neutron physics of OTTO cores will be very different from previous homogeneous fuel-loading schemes, detailed experimental and theoretical investigations of these objectives were performed at the critical facility KAHTER. Experimental and theoretical investigations have been carried out to determine critical masses, reaction rates, and control rod worths in the upper cavity and top reflector. Fast flux distributions in upper graphite reflectors were also measured to estimate graphite damage. The critical masses and keff’s are calculated using two- and three-dimensional code systems. The three-dimensional codes give keffvalues for the high-temperature gas-cooled reactor OTTO cores at zero burnup within a margin that is currently standard for these calculations. The agreement of measured and calculated reactivity worths of the top reflector rods is better than 2%.

ISSN:0029-5639    

DOI:10.13182/NSE87-A23494

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractIn collaboration with Kernforschungsanlage Jülich, Federal Republic of Germany, and other companies, dynamic experiments have been carried out with the Arbeitsgemeinschaft Versuchsreaktor (AVR) to test advanced dynamic computer models with the goal of using low-enriched uranium (LEU) fuel in future high-temperature gas-cooled reactors. Since LEU fuel has been used for the AVR since 1982, both experimental and theoretical behavior has been studied during the changeover from highly enriched uranium to LEU.The experiments comprise fast power transients that are initiated by either a fast control rod movement or a fast change of coolant flow. The neutron flux and other important parameters are registered in suitable time expansion.To prevent the cantilevered segments of the carbon brick core ceiling from being exposed to unallowable high-temperature gradients, the rod movements are restricted to limit the reactivity variation to∼60 mNile.For the coolant flow transients, the blower speed is usually reduced from 100 to 50%, and then elevated again to 80% after 30 min. A return to 100% is not possible because of the overshoot of the neutron flux. Also, in some experiments the speed is reduced to 80%, after which the core remains under the control of xenon influence for∼1 day.

ISSN:0029-5639    

DOI:10.13182/NSE87-A23495

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractIn the Arbeitsgemeinschaft Versuchsreaktor high-temperature reactor low-enriched fuel elements have been loaded for several years, replacing about half of the initial highly enriched uranium-thorium fuel. This changeover is accompanied by an elaborate experimental program wherein changes in the neutronics and thermohydraulics behavior of the system are monitored.Within this program reactor transients are induced by means of either circulator speed reduction or control rod movement. The resulting transients in neutron flux and temperatures are recorded and used as a basis for detailed theoretical analysis.Working groups at several institutions have carried out transient calculations using different dynamic codes. The results are presented and differences are discussed. In general, the experimental values were reproduced in a very satisfactory way.

ISSN:0029-5639    

DOI:10.13182/NSE87-A23496

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe measurements that were made in recent years to determine the hot and the cold coefficient of reactivity and the corresponding model calculations carried out by both Interatom and Hochtemperaturreaktorbau are described. The effects of the partial load of low-enriched uranium (LEU) fuel were of major interest.The cold coefficient is determined in shutdown periods by measuring the subcriticality at different core temperatures. The hot coefficient is determined under operation in connection with a change in coolant outlet temperature at constant power using a calibrated rod curve.In the case of the cold coefficient, experiment and model calculations are in perfect agreement. Calculated values for the hot coefficient are∼20% lower than the experimental ones. However, neither experiment nor model calculation show any significant change of the hot coefficient when about one-fourth of the core content was being replaced by LEU fuel.

ISSN:0029-5639    

DOI:10.13182/NSE87-A23497

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractFor light water reactors, loss of coolant is an important point in safety analysis, whereas for gas-cooled reactors the ingress of water into the core region is an incident of safety relevance. The applicability of the computer code system GAMTEREX to pebble beds of spherical high-temperature gas-cooled reactor fuel elements with simulated water ingress is verified by experiment. The measurements were performed at a Siemens-Argonaut reactor, using its ring core as a driver zone for a pebble-bed core in the center of the reactor.

ISSN:0029-5639    

DOI:10.13182/NSE87-A23498

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE87-A23489

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor