287 research outputs found
Calibration and monitoring of the GENEPI neutron source for the MUSE IV experiment
Rapport intern
The Thorium Molten Salt Reactor : Moving on from the MSBR
A re-evaluation of the Molten Salt Breeder Reactor concept has revealed
problems related to its safety and to the complexity of the reprocessing
considered. A reflection is carried out anew in view of finding innovative
solutions leading to the Thorium Molten Salt Reactor concept. Several main
constraints are established and serve as guides to parametric evaluations.
These then give an understanding of the influence of important core parameters
on the reactor's operation. The aim of this paper is to discuss this vast
research domain and to single out the Molten Salt Reactor configurations that
deserve further evaluation.Comment: 11 pages, 8 figures, 6 table
Analytical investigation and experimental application of the source modulation technique to measure
In recent years great interest has been displayed, worldwide, for Accelerator Driven Sub critical reactors (ADS) to incinerate the minor actinides generated by the existing energy producing reactors. In sub critical systems, the effective neutron multiplication factor is lower than 1.0 and the neutrons otherwise required to maintain the chain reaction, can be put to other uses, in particular, the destruction of nuclear wastes such as minor actinides (MA). One of the major advantages of such ADS systems is that it can be operated with very high M.A content without jeopardizing the overall safety due to a small effective delayed neutron fraction, a small Doppler temperature coefficient and possibly also a large void coefficient depending on the chosen coolant. This enhanced safety however prerequisites at all time a sufficient subcriticality margin. Reliable reactivity monitoring techniques are hence required to achieve this goal. The MUSE-4 program is a series of low power experiments carried out at the CEA-Cadarache MASURCA facility to investigate the various methods leading to the measurement of the reactivity level and associated kinetic parameters such as the effective delayed neutron fraction. The aim of this paper is to present the results obtained with a method which directly gives the ratio, for a sub critical assembly, between the reactivity ρ and the effective delayed neutron fraction βeff. By combining these results to those obtained with the kp-method for the prompt neutron multiplication coefficient, we have access to the parameters which govern the prompt and the slow kinetics of a sub critical assembly. These parameters can be obtained without reference to any calibration measurement in critical configuration. It opens the way to the control of larger sub critical demonstrators which are operating with fuels which cannot be used in critical reactor, and, thanks to sub criticality, which are characterized by a deterministic safety
Fast Thorium Molten Salt Reactors started with Plutonium
One of the pending questions concerning Molten Salt Reactors based on the 232Th/233U fuel cycle is the supply of the fissile matter, and as a consequence the deployment possibilities of a fleet of Molten Salt Reactors, since 233U does not exist on earth and is not yet produced in the current operating reactors. A solution may consist in producing 233U in special devices containing Thorium, in Pressurized Water or Fast Neutrons Reactors. Two alternatives to produce 233U are examined here: directly in standard Molten Salt Reactors started with Plutonium as fissile matter and then operated in the Th/233U cycle; or in dedicated Molten Salt Reactors started and fed with Plutonium as fissile matter and Thorium as fertile matter. The idea is to design a critical reactor able to burn the Plutonium and the minor actinides presently produced in PWRs, and consequently to convert this Plutonium into 233U. A particular reactor configuration is used, called unique channel configuration in which there is no moderator in the core, leading to a quasi fast neutron spectrum, allowing Plutonium to be used as fissile matter. The conversion capacities of such Molten Salt Reactors are excellent. For Molten Salt Reactors only started with Plutonium, the assets of the Thorium fuel cycle turn out to be quickly recovered and the reactors characteristics turn out to be equivalent to Molten Salt Reactors operated with 233U only. Using a combination of Molten Salt Reactors started or operated with Plutonium and of Molten Salt Reactors started with 233U, the deployment capabilities of these reactors fully satisfy the condition of sustainability
Thorium fuel cycles : a graphite-moderated molten salt reactor versus a fast spectrum solid fuel system
Prompt reactivity determination in a subcritical assembly through the response to a Dirac pulse
The full understanding of the kinetics of a subcritical assembly is a key issue for its online reactivity control. Point kinetics is not sufficient to determine the prompt reactivity of a subcritical assembly through the response to a dirac pulse, in particular in the cases of a large reflector, a small reactor, or a large subcriticality.Taking into account the distribution of intergeneration times, which appears as a robust characteristic of each type of reactor, helps to understand this behaviour.Eventually, a method is proposed for the determination of the prompt reactivity. It provides a decrease rate function depending on the prompt multiplication coefficient Keffp. Fitting a measured decrease rate with this function, calculated once for the reactor, gives the true value of keffp. The robustness of the method is tested. (Elsevier
Monitoring Of 14 Mev Neutrons
Long-lived fission products and minor actinides produced in nuclear power plants are the most radiotoxic nuclear wastes. They can be transmuted into stable nuclei or into nuclei with shorter lifetime thanks to the so-called Accelerator Driven Systems (ADS), consisting of the coupling of an intense high energy proton beam, a spallation target and a sub-critical reactor core. For safety reasons, an on-line and robust measurement of the reactivity during loading and power operation is mandatory. The investigation of the relationship between the current of the accelerator and the power level (or neutron flux) of the reactor appears to be powerful, any change in reactivity being accessible through the measurement of the current and the flux. Such a relationship will be studied in an experiment to be performed at the YALINA facility (JIPNR Sosny - Belarus) in the framework of the EUROTRANS IP (6 FP). At this installation, 14 MeV neutrons are produced in T(d,n)He reactions by a deuteron beam impinging on a TiT target. Due to the tritium consumption over time, the intensity of the deuteron beam cannot be used for the monitoring of the neutron beam. The source neutron yield itself has to be accessed. This contribution describes the performance of a three-element silicon telescope dedicate
Le Thorium Molten Salt Reactor : Au-delà du MSBR
La re-évaluation du concept de Molten Salt Breeder Reactor a fait apparaître des problèmes liés à la sûreté et à la complexité du retraitement. Une nouvelle réflexion est menée afin de trouver des solutions et ainsi d'aboutir au concept du Thorium Molten Salt Reactor. Plusieurs contraintes principales sont établies et vont servir de guides aux études paramétriques. Celles-ci permettent alors de comprendre l'influence de paramètres importants du coeur sur le comportement du réacteur. Le but de cet article est de présenter ce vaste domaine de recherche et d'indiquer quelles configurations intéressantes de Réacteurs à Sels Fondus peuvent être étudiées plus avant
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