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Neutronics of minor-actinide burning accelerator-driven systems with ceramic fuel
KTH, School of Engineering Sciences (SCI), Physics, Reactor Physics.ORCID iD: 0000-0002-6082-8913
KTH, School of Engineering Sciences (SCI), Physics, Reactor Physics.
2005 (English)In: Nuclear Technology, ISSN 0029-5450, E-ISSN 1943-7471, Vol. 152, no 3, 367-381 p.Article in journal (Refereed) Published
Abstract [en]

We have investigated neutronic properties of lead-bismuth-cooled accelerator-driven systems with different minor-actinide-based ceramic fuels (two composite oxides and one solid-solution nitride). Adopting a transuranic composition with 40% plutonium in the initial load, transmutation rates of higher actinides (americium and curium) equal to 265 to 285 kg/GW(thermal) -yr are obtained. The smallest reactivity swing is provided by the magnesium oxide-based cercer fuel. The cercer cores, however, exhibit large coolant void worths, which is of concern in the case of gas bubble introduction into the core. Nitride and cermet cores are more stable with respect to void formation. The poorer neutron economy of the molybdenum-based cermet makes it difficult, however, to accommodate an inert matrix volume fraction exceeding 50%, a lower limit for fabricability. Higher plutonium fraction is thus required for the cermet, which would lead to lower actinide burning rates. The nitride core yields high actinide burning rates, low void worths, and acceptable reactivity losses.

Place, publisher, year, edition, pages
2005. Vol. 152, no 3, 367-381 p.
Keyword [en]
accelerator-driven system, minor-actinide burner, ceramic fuel
National Category
Subatomic Physics
Identifiers
URN: urn:nbn:se:kth:diva-4981ISI: 000233378500010Scopus ID: 2-s2.0-28044451522OAI: oai:DiVA.org:kth-4981DiVA: diva2:7337
Note
QC 20101008. Uppdaterad från accepted till published (20101008).Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Accelerator-driven systems: safety and kinetics
Open this publication in new window or tab >>Accelerator-driven systems: safety and kinetics
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The accelerator-driven system (ADS) is recognized as a promising system for the purpose of nuclear waste transmutation and minimization of spent fuel radiotoxicity. The primary cause for this derives from its accelerator-driven, sub-critical operating state, which introduces beneficial safety-related features allowing for application of cores employing fuel systems containing pure transuranics or minor actinides, thereby offering increased incineration rate of waste products and minimal deployment of advanced (and expensive) partitioning and transmutation technologies. The main theme of the thesis is safety and kinetics performance of accelerator-driven nuclear reactors. The studies are confined to the examination of ADS design proposals employing fast neutron spectrum, uranium-free lattice fuels, and liquid-metal cooling, with emphasis on lead-bismuth coolant. The thesis consists of computational studies under normal operation and hypothetical accidents, and of evaluation and identification of safety design features.

By itself, subcritical operation provides a distinct safety advantage over critical reactor operation, distinguished by high operational stability and additional margins for positive reactivity insertion. For a uranium-free minor actinide based fuel important safety parameters deteriorate. Specific analyses suggest that operation of such cores in a critical state would be very difficult. The studies of unprotected transients indicate that lead-bismuth cooled accelerator-driven reactors can be effective in addressing the low effective delayed neutron fraction and the high coolant void reactivity that comes with the minor actinide fuel, but some supportive prompt negative feedback mechanism might be considered necessary to compensate for a weak Doppler effect in case of a prompt critical transient. Although lead-bismuth features a high boiling point, the work underlines the importance of maintaining a low coolant void reactivity value. The transient design studies identified a molybdenum-based Ceramic-Metal (CerMet) fuel with favourable inherent safety features. A higher lattice pitch is suggested to avoid mechanical failure during unprotected loss-of-flow. Detailed coupled neutron kinetics and thermal hydraulic analyses demonstrated that the point kinetics approximation is capable of providing highly accurate transient calculations of subcritical systems. The results suggest better precision at lower keff levels, which is an effect of the reduced sensitivity to system reactivity perturbations in a subcritical state resulting in small spatial distortions. In the course of a beam reliability study, the accelerator was identified as responsible for frequent beam interruptions. It is clear that extensive improvement in the mean-time between beam failures is required.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 73 p.
Series
Trita-FYS, ISSN 0280-316X ; 2005:13
Keyword
Nuclear physics, Kärnfysik
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-146 (URN)91-7283-988-0 (ISBN)
Public defence
2005-03-18, Sal FA32, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101011Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2010-10-11Bibliographically approved

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