Zur selbsttätig sicheren Begrenzung von nuklearer Leistung und Brennstofftemperatur in innovativen Kernreaktoren

Nuclear energy probably will not contribute significantly to the future worldwide energysupply until it can be made catastrophefree. Therefore it has to be shown, that theconsequences of even largest accidents will have no major impact to the environmentof a power plant.In this paper one of the basic conditions for such a nuclear technology is discussed.Using mainly the modular pebble-bed high-temperature reactor as an example, thedesign principles, analytical methods and the level of knowledge as given today incontrolling reactivity accidents by inherent safety features of innovative nuclear reactorsare described. Complementary possibilities are shown to reach this goal with systems ofdifferent types of construction . Questions open today and resulting requirements forfuture activities are discussed .Today's knowledge credibly supports the possibility of a catastrophefree nucleartechnology with respect to reactivity event

V.S.O.P.(97) Computer Code System for Reactor Physics and Fuel Cycle Simulation : Input Manual and Comments

V.S.O.P. (97) is a computer code system for the comprehensive numerical simulation ofthe physics of thermal reactors. It implies processing ofcross sections, the setup ofthe reactor and ofthe fuel element, repeated neutron spectrum evaluation, neutron diffusion calculation in two or three dimensions, fuel burnup, fuel shuffling, reactor control, thermal hydraulics and fuel cycle costs. The thermal hydraulics part (steady state and time-dependent) is restricted to EM and to two spatial dimensions. V.S.O.P (97) can simulate the reactor operation from the initial core towards the equilibrium core. V.S.O.P. 97 - on the basis of V.S.O.P. 94 - has been improved with regard to a more detailed treatment of the build-up and the depletion of the heavy metal isotopes. Their chains now include theminor actinides. Resonance cross sections of the lumped resonance absorbers are evaluated burnup-dependent. Beyond this, the code has been reviewed in many details, aiming at an improved precision in the computer simulation ofthe features ofthe reactors and oftheir fuel cycle. The code consists of about 65400 FORTRAN statements. A memory of 32 MB should be available for its use

V.S.O.P. (99) for WINDOWS and UNIX : computer code system for reactor physics and fuel cycle simulation

V.S.O.P. is a computer code system for the comprehensive numerical simulation of the physics of thermal reactors. It implies the setup of the reactor and of the fuel element, processing of cross sections, neutron spectrum evaluation, neutron diffusion calculation in two or three dimensions, fuel burnup, fuel shuffling, reactor control, thermal hydraulics and fuel cycle costs. The thermal hydraulics part (steady state and time-dependent) is restricted to HTRs and to two spatial dimensions. The code can simulate the reactor operation from the initial core towards the equilibrium core. V.S.O.P.($\underline{99}$) represents the further development of V.S.O.P. ($\underline{97}$). Compared to its precursor, the code system has been improved in many details. Major extensions have been included concerning the thermal hydraulic sections. Beyond that, the many modules of the code-system have been condensed to only 2 executables in the "99",-release of V.S.O.P., to be comfortably handled on a WINDOWS-PC or a UNIX-computer. The necessary data input as well as tile handling and book-keeping of intermediate data sets has been condensed and simplified. A 64 MB memory should be available for the execution of the code. The hard disk requirement for the executables and the basic libraries associated with the code amounts to about 7 MB

V.S.O.P. (99/09) Computer Code System for Reactor Physics and Fuel Cycle Simulation; Version 2009

V.S.O.P.(99/ 09) represents the further development of V.S.O.P.(99/ 05). Compared to its precursor, the code system has been improved again in many details. The main motivation for this new code version was to update the basic nuclear libraries used by the code system. Thus, all cross section libraries involved in the code have now been based on ENDF/B-VII. V.S.O.P. is a computer code system for the comprehensive numerical simulation of the physics of thermal reactors. It implies the setup of the reactor and of the fuel element, processing of cross sections, neutron spectrum evaluation, neutron diffusion calculation in two or three dimensions, fuel burnup, fuel shuffling, reactor control, thermal hydraulics and fuel cycle costs. The thermal hydraulics part (steady state and time-dependent) is restricted to gas-cooled reactors and to two spatial dimensions. The code can simulate the reactor operation from the initial core towards the equilibrium core

Analysis of the European results on the HTTR's core physics benchmarks

In the frame of the European contract HTR-N, a work package is devoted to the code validation and method improvements as far as the hi-h temperature gas-cooled reactor (HTGR) core modelling is concerned. Institutions from three countries are involved in this work package: FZJ in Germany, NRG and IRI in the Netherlands, and CEA in France. The present work is based on a benchmark problem proposed by JAERI through the IAEA. It concerns the HTTR's start-up core physics experiments that were a good opportunity for the European partners to validate their calculational tools and methods. The number of fuel columns necessary to achieve the first criticality and the excess reactivity for 18, 24, and 30 fuel columns in the core had to be evaluated. Pre-test and post-test calculational results, obtained by the partners, are compared with each other and with the experiment. Parts of the discrepancies between experiment and pre-test predictions are analysed and tackled by different treatments. In the case of the Monte Carlo code TRIPOL14, used by CEA, the discrepancy between measurement and calculation at the first criticality is reduced to Deltak/k similar to 0.85%, when considering the revised data of the HTTR benchmark [Fujimoto, private communication]. In the case of the diffusion codes, this discrepancy is reduced to Deltak/k similar to 0.8% (FZJ) and 2.7 or 1.8% (CEA). (C) 2003 Elsevier Science B.V All rights reserved