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Definition and application of proton source efficiency in accelerator driven systems
KTH, Superseded Departments, Physics.
KTH, School of Engineering Sciences (SCI), Physics, Reactor Physics.ORCID iD: 0000-0002-6082-8913
KTH, Superseded Departments, Physics.
KTH, Superseded Departments, Physics.
2003 (English)In: Nuclear science and engineering, ISSN 0029-5639, E-ISSN 1943-748X, Vol. 145, no 3, 390-399 p.Article in journal (Refereed) Published
Abstract [en]

In order to study the beam power amplification of an accelerator-driven system (ADS), a new parameter, the proton source efficiency psi* is introduced. psi* represents the average importance of the external proton source, relative to the average importance of the eigenmode production, and is closely related to the neutron source efficiency rho*, which is frequently used in the ADS field. rho* is commonly used in the physics of subcritical systems driven by any external source (spallation source, (d,d), (d, t), Cf-252 spontaneous fissions, etc.). On the contrary, psi* has been defined in this paper exclusively for ADS studies where the system is driven by a spallation source. The main advantage with using psi* instead of rho* for ADS is that the way of defining the external source is unique and that it is proportional to the core power divided by the proton beam power, independent of the neutron source distribution.

Numerical simulations have been performed with the Monte Carlo code MCNPX in order to study psi* as a function of different design parameters. It was found that, in order to maximize psi* and therefore minimize the proton current needs, a target radius as small as possible should be chosen. For target radii smaller than similar to30 cm, lead-bismuth is a better choice of coolant material than sodium, regarding the proton source efficiency, while for larger target radii the two materials are equally good. The optimal axial proton beam impact was found to be located similar to 20 cm above the core center. Varying the proton energy, psi*/E-p was found to have a maximum for proton energies between 1200 and 1400 MeV Increasing the americium content in the fuel decreases psi* considerably, in particular when the target radius is large.

Place, publisher, year, edition, pages
2003. Vol. 145, no 3, 390-399 p.
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6746ISI: 000186289600008OAI: oai:DiVA.org:kth-6746DiVA: diva2:11544
Note
QC 20101005Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Source efficiency and high-energy neutronics in accelerator-driven systems
Open this publication in new window or tab >>Source efficiency and high-energy neutronics in accelerator-driven systems
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Transmutation of plutonium and minor actinides in accelerator-driven systems (ADS) is being envisaged for the purpose of reducing the long-term radiotoxic inventory of spent nuclear reactor fuel. For this reason, the physics of sub-critical systems are being studied in several different experimental programs across the world. Three of these experiments have been studied within the scope of the present thesis; the MUSE experiments in France, the Yalina experiments in Belarus and the SAD experiments in Russia. The investigations of the MUSE experiments have focused on three different neutronic parameters; the neutron energy spectrum, the external neutron source efficiency and the dynamic neutron source response. It has been shown that the choice of external neutron source has negligible effect on the neutron energy spectrum in the core. Therefore, from this point of view, the MUSE experiments can be considered representative of an ADS. From the analyses of different reactivity determination methods in the Yalina experiments, it can be concluded that the slope fit method gives results in good agreement with the results obtained by the Monte Carlo method MCNP. Moreover, it was found that the Sjöstrand method underestimates keff slightly, in comparison with MCNP and the other investigated methods. In the radiation shielding studies of the SAD experiments, it was shown that the entire part of the effective dose detected at the top of the biological shielding originates from the proton-induced spallation reactions in the target. Thus, it can be concluded that the effective dose is directly proportional to the proton beam power, but independent of the reactivity of the sub-critical core. In order to study the energy gain of an ADS, i.e., the core power divided by the proton beam power, the proton source efficiency, ψ*, has been studied for various ADS models. ψ* is defined in analogy with the neutron source efficiency, φ*, but relates the core power directly to the source protons instead of to the source neutrons. φ* is commonly used in the physics of sub-critical systems, driven by any external neutron source (spallation source, (D,D), (D,T), 252Cf spontaneous fission etc.). On the contrary, ψ* has been defined only for ADS studies, where the system is driven by a proton-induced spallation source. The main advantages of using ψ* instead of φ* are that the way of defining the external source is unique and that ψ* is proportional to the energy gain. An important part of this thesis has been devoted to studies of ψ* as a function of different system parameters, thereby providing a basis for an ADS design with optimal properties for obtaining a high core power over beam power ratio. For instance, ψ* was found to decrease considerably with increasing spallation target radius.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. xiv, 136 p.
Series
Trita-FYS, ISSN 0280-316X ; 2005:46
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-427 (URN)91-7178-147-1 (ISBN)
Public defence
2005-09-30, Sal FA32, AlvaNova, Roslagstullsbacken 21, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
QC 20101005Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2010-10-05Bibliographically approved

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Wallenius, Janne

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