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Ågren, Olov
Publications (10 of 77) Show all publications
Chernitskiy, S. V., Moiseenko, V. E., Ågren, O. & Noack, K. (2017). A fuel cycle for minor actinides burning in a stellarator-mirror fusion-fission hybrid. PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY (1), 36-39
Open this publication in new window or tab >>A fuel cycle for minor actinides burning in a stellarator-mirror fusion-fission hybrid
2017 (English)In: PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, ISSN 1562-6016, no 1, p. 36-39Article in journal (Refereed) Published
Abstract [en]

The MCNPX Monte-Carlo code has been used to model a concept of a fusion-fission stellarator-mirror hybrid aimed for transmutation transuranic content from the spent nuclear fuel. A fuel cycle for the subcritical fusion-fission hybrid is investigated and discussed.

Place, publisher, year, edition, pages
KHARKOV INST PHYSICS & TECHNOLOGY, 2017
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-340983 (URN)000413444800010 ()
Available from: 2018-02-16 Created: 2018-02-16 Last updated: 2018-02-16Bibliographically approved
Ågren, O. & Moiseenko, V. E. (2017). On improved confinement in mirror plasmas by a radial electric field. Plasma Physics and Controlled Fusion, 59(11), Article ID 115001.
Open this publication in new window or tab >>On improved confinement in mirror plasmas by a radial electric field
2017 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 59, no 11, article id 115001Article in journal (Refereed) Published
Abstract [en]

A weak radial electric field can suppress radial excursions of a guiding center from its mean magnetic surface. The physical origin of this effect is the smearing action by a poloidal E x B rotation, which tend to cancel out the inward and outward radial drifts. A use of this phenomenon may provide larger margins for magnetic field shaping with radial confinement of particles maintained in the collision free idealization. Mirror fields, stabilized by a quadrupolar field component, are of particular interest for their MHD stability and the possibility to control the quasi neutral radial electric field by biased potential plates outside the confinement region. Flux surface footprints on the end tank wall have to be traced to avoid short-circuiting between biased plates. Assuming a robust biasing procedure, moderate voltage demands for the biased plates seems adequate to cure even the radial excursions of Yushmanov ions which could be locally trapped near the mirrors. Analytical expressions are obtained for a magnetic quadrupolar mirror configuration which possesses minimal radial magnetic drifts in the central confinement region. By adding a weak controlled radial quasi-neutral electric field, the majority of gyro centers are predicted to be forced to move even closer to their respective mean magnetic surface. The gyro center radial coordinate is in such a case an accurate approximation for a constant of motion. By using this constant of motion, the analysis is in a Vlasov description extended to finite beta. A correspondence between that Vlasov system and a fluid description with a scalar pressure and an electric potential is verified. The minimum B criterion is considered and implications for flute mode stability in the considered magnetic field is analyzed. By carrying out a long-thin expansion to a higher order, the validity of the calculations are extended to shorter and more compact device designs.

Keyword
radial invariant, radial electric field, biased potential plates, magnetic mirror, mirror machine, hybrid reactor, minimum B
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-336287 (URN)10.1088/1361-6587/aa8544 (DOI)000411155900001 ()
Available from: 2018-01-25 Created: 2018-01-25 Last updated: 2018-01-25Bibliographically approved
Moiseenko, V. E., Nemov, V. V., Ågren, O., Kasilov, S. V. & Garkusha, I. E. (2016). Fast ion motion in the plasma part of a stellarator-mirror fission-fusion hybrid. Plasma Physics and Controlled Fusion, 58(6), Article ID 064005.
Open this publication in new window or tab >>Fast ion motion in the plasma part of a stellarator-mirror fission-fusion hybrid
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2016 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 58, no 6, article id 064005Article in journal (Refereed) Published
Abstract [en]

Recent developments of a stellarator-mirror (SM) fission-fusion hybrid concept are reviewed. The hybrid consists of a fusion neutron source and a powerful sub-critical fast fission reactor core. The aim is transmutation of spent nuclear fuel and safe fission energy production. In its fusion part, a stellarator-type system with an embedded magnetic mirror is used. The stellarator confines deuterium plasma with moderate temperature, 1-2 keV. In the magnetic mirror, a hot component of sloshing tritium ions is trapped. There, the fusion neutrons are generated. A candidate for a combined SM system is a DRACON magnetic trap. A basic idea behind an SM device is to maintain local neutron production in a mirror part, but at the same time eliminate the end losses by using a toroidal device. A possible drawback is that the stellarator part can introduce collision-free radial drift losses, which is the main topic for this study. For high energy ions of tritium with an energy of 70 keV, comparative computations of collisionless losses in the rectilinear part of a specific design of the DRACON type trap are carried out. Two versions of the trap are considered with different lengths of the rectilinear sections. Also the total number of current-carrying rings in the magnetic system is varied. The results predict that high energy ions from neutral beam injection can be satisfactorily confined in the mirror part during 0.1-1 s. The Uragan-2M experimental device is used to check key points of the SM concept. The magnetic configuration of a stellarator with an embedded magnetic mirror is arranged in this device by switching off one toroidal coil. The motion of particles magnetically trapped in the embedded mirror is analyzed numerically with use of motional invariants. It is found that without radial electric field particles quickly drift out of the SM, even if the particles initially are located on a nested magnetic surface. We will show that a weak radial electric field, which would be spontaneously created by the ambipolar radial particle losses, can make drift trajectories closed, which substantially improves particle confinement. It is remarkable that the improvement acts both for positive and negative charges.

Keyword
fusion reactor, fission reactor, fusion-fission hybrid, stellarator, magnetic mirror
National Category
Fusion, Plasma and Space Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-298077 (URN)10.1088/0741-3335/58/6/064005 (DOI)000376275600005 ()
Available from: 2016-06-30 Created: 2016-06-29 Last updated: 2017-11-28Bibliographically approved
Ågren, O. & Moiseenko, V. E. (2014). Radial constant of motion for particles in magnetic mirror fields. Plasma Physics and Controlled Fusion, 56(9), 095026
Open this publication in new window or tab >>Radial constant of motion for particles in magnetic mirror fields
2014 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 56, no 9, p. 095026-Article in journal (Refereed) Published
Abstract [en]

It is crucial for magnetic fusion devices that particle confinement occurs for long periods in a magnetic flux tube, and radial loss from the flux tube by a collision-free radial drift needs to be eliminated. Longitudinal, as well as radial, confinement is required. Two standard constants of motion, the energy and the magnetic moment of the gyrating particle, provide longitudinal confinement. A third constant of motion, which implies bounded radial motion, would be sufficient for radial confinement, but it is often impossible to identify such an invariant. A closed form expression for a radial invariant is derived for magnetic mirrors with a stabilizing quadrupolar field. A weak radial electric field, controlled by electrically biased endplates, is a tool for making a collision-free motion radially bounded in open systems. Experimental results in such magnetic confinement schemes indicate a qualitative agreement with our predictions for the existence of a radial invariant. Voltage and power requirements for the biased endplates are vanishingly small if the magnetic drifts are minimized in the magnetic field design. The power requirements to sustain the biased potentials are expected to be vanishingly small for a gross stable plasma.

Keyword
radial invariant, radial constant of motion, radial drift loss, magnetic mirror, mirror machine, hybrid reactor, biased endplates
National Category
Physical Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-234178 (URN)10.1088/0741-3335/56/9/095026 (DOI)000341854100036 ()
Available from: 2014-10-15 Created: 2014-10-14 Last updated: 2017-12-05Bibliographically approved
Moiseenko, V. E., Kotenko, V. G., Chernitskiy, S. V., Nemov, V. V., Ågren, O., Noack, K., . . . Garkusha, I. E. (2014). Research on stellarator-mirror fission-fusion hybrid. Plasma Physics and Controlled Fusion, 56(9), 094008
Open this publication in new window or tab >>Research on stellarator-mirror fission-fusion hybrid
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2014 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 56, no 9, p. 094008-Article in journal (Refereed) Published
Abstract [en]

The development of a stellarator-mirror fission-fusion hybrid concept is reviewed. The hybrid comprises of a fusion neutron source and a powerful sub-critical fast fission reactor core. The aim is the transmutation of spent nuclear fuel and safe fission energy production. In its fusion part, neutrons are generated in deuterium-tritium (D-T) plasma, confined magnetically in a stellarator-type system with an embedded magnetic mirror. Based on kinetic calculations, the energy balance for such a system is analyzed. Neutron calculations have been performed with the MCNPX code, and the principal design of the reactor part is developed. Neutron outflux at different outer parts of the reactor is calculated. Numerical simulations have been performed on the structure of a magnetic field in a model of the stellarator-mirror device, and that is achieved by switching off one or two coils of toroidal field in the Uragan-2M torsatron. The calculations predict the existence of closed magnetic surfaces under certain conditions. The confinement of fast particles in such a magnetic trap is analyzed.

Keyword
fusion reactor, fission reactor, fusion-fission hybrid, stellarator, mirror
National Category
Physical Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-234179 (URN)10.1088/0741-3335/56/9/094008 (DOI)000341854100009 ()
Available from: 2014-10-15 Created: 2014-10-14 Last updated: 2017-12-05Bibliographically approved
Goude, A. & Ågren, O. (2014). Simulations of a vertical axis turbine in a channel. Renewable energy, 63, 477-485
Open this publication in new window or tab >>Simulations of a vertical axis turbine in a channel
2014 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 63, p. 477-485Article in journal (Refereed) Published
Abstract [en]

The power coefficient of a turbine increases according to the predictions from streamtube theory for sites with a confined fluid flow. Here, a vertical axis turbine (optimized for free flow) has been simulated by a two-dimensional vortex method, both in a channel and in free flow. The first part of the study concerns the numerical parameters of channel simulations. It is found that for free flow and wide channels, a large number of revolutions is required for convergence (around 100 at the optimal tip speed ratio and increasing with higher tip speed ratio), while for smaller channels, the required number of revolutions decreases. The second part analyses changes in turbine performance by the channel boundaries. The turbine performance increases when the channel width is decreased, although the results are below the predictions from streamtube theory, and this difference increases with decreasing channel width. It is also observed that the optimal tip speed ratio increases with decreasing channel width. By increasing the chord, which decreases the optimal tip speed ratio, the power coefficient can be increased somewhat.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
Vertical axis turbine, Vortex method, Channel flow, Simulation, Current power
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-183737 (URN)10.1016/j.renene.2013.09.038 (DOI)000330488100054 ()
Available from: 2012-11-01 Created: 2012-11-01 Last updated: 2017-12-07Bibliographically approved
Chernitskiy, S. V., Gann, V. V. & Ågren, O. (2014). Static Neutronic Calculation of a Fusion Neutron Source. Problems of Atomic Science and Technology (6), 12-15
Open this publication in new window or tab >>Static Neutronic Calculation of a Fusion Neutron Source
2014 (English)In: Problems of Atomic Science and Technology, ISSN 1562-6016, no 6, p. 12-15Article in journal (Refereed) Published
Abstract [en]

The MCNPX numerical code has been used to model a fusion neutron source based on a combined stellarator-mirror trap. Calculation results for the neutron flux and spectrum inside the first wall are presented. Heat load and irradiation damage on the first wall are calculated.

National Category
Physical Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-243083 (URN)000347167400003 ()
Available from: 2015-02-06 Created: 2015-02-04 Last updated: 2015-11-11Bibliographically approved
Chernitskiy, S. V., Moiseenko, V. E., Noack, K., Ågren, O. & Abdullayev, A. (2014). Static neutronic calculation of a subcritical transmutation stellarator-mirror fusion-fission hybrid. Annals of Nuclear Energy, 72, 413-420
Open this publication in new window or tab >>Static neutronic calculation of a subcritical transmutation stellarator-mirror fusion-fission hybrid
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2014 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 72, p. 413-420Article in journal (Refereed) Published
Abstract [en]

The MCNPX Monte-Carlo code has been used to model the neutron transport in a sub-critical fast fission reactor driven by a fusion neutron source. A stellarator-mirror device is considered as the fusion neutron source. The principal composition for a fission blanket of a mirror fusion-fission hybrid is devised from the calculations. Heat load on the first wall, the distribution of the neutron fields in the reactor, the neutron spectrum and the distribution of energy release in the blanket are calculated. The possibility of tritium breeding inside the installation in quantities that meet the needs of the fusion neutron source is analyzed. The portion of the plasma column generates fusion neutrons that mainly do not reach the fission reactor core is proposed to be surrounded by a vessel filled with borated water to absorb the flying out neutrons. The flux of the neutrons escaping from the device to surrounding space is also calculated.

Keyword
Fusion-fission hybrid, Spent nuclear fuel, MCNPX calculations, Effective multiplication factor, Neutron flux
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-231973 (URN)10.1016/j.anucene.2014.06.001 (DOI)000340314000042 ()
Available from: 2014-09-15 Created: 2014-09-12 Last updated: 2017-12-05Bibliographically approved
Noack, K., Ågren, O., Moiseenko, V. E. & Hagnestål, A. (2013). Comments on the power amplification factor of a driven subcritical system. Annals of Nuclear Energy, 59, 261-266
Open this publication in new window or tab >>Comments on the power amplification factor of a driven subcritical system
2013 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 59, p. 261-266Article in journal (Refereed) Published
Abstract [en]

The power amplification factor PAF of a driven subcritical system is defined as the ratio of the fission power output of the blanket to the power which the driver must deliver to sustain its neutron source intensity. This parameter decisively determines the effectiveness of the whole system independent of its special purpose as energy amplifier or as transmutation facility. The present note derives a refined analytical expression for the PAF which reveals more physical details than the expressions given by other authors. Moreover, the traditionally used forms of the static reactor eigenvalue equation and of its adjoint equation are rewritten for subcritical systems and used in the derivation of the expression for the PAF. The derived formula and the modified eigenvalue equations are discussed.

Keyword
Driven subcritical system, Fusion–fission hybrid, Power amplification factor, Static reactor eigenvalue equation
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-190422 (URN)10.1016/j.anucene.2012.06.020 (DOI)000320834800030 ()
Available from: 2013-01-08 Created: 2013-01-08 Last updated: 2017-12-06Bibliographically approved
Ågren, O., Moiseenko, V. E., Noack, K., Hagnestål, A., Källne, J. & Anglart, H. (2013). Hybrid Reactor Studies Based on the Straight Field Line Mirror. Paper presented at Joint Conference of 9th International Conference on Open Magnetic Systems for Plasma Confinement (OS) and 3rd International Workshop on Plasma Material Interaction Facilities for Fusion Research (PMIF), AUG 27-31, 2012, Tsukuba, JAPAN. Fusion science and technology, 63(1T), 52-57
Open this publication in new window or tab >>Hybrid Reactor Studies Based on the Straight Field Line Mirror
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2013 (English)In: Fusion science and technology, ISSN 1536-1055, E-ISSN 1943-7641, Vol. 63, no 1T, p. 52-57Article in journal (Refereed) Published
Abstract [en]

The straight field line mirror (SFLM) hybrid reactor studies aim to identify a concept where the safety of fission power production could be enhanced. A fusion neutron source could become a mean to achieve this. The SFLM studies address critical issues such as reactor safety, natural circulation of coolants, steady state operation for a year or more and means to avoid too strong material loads by a proper geometrical arrangement of the reactor components. A key result is that power production may be possible with a fusion Q factor as low as 0.15. This possibility arises from the high power amplification by fission, which within reactor safety margins may exceed a factor of 100. The requirements on electron temperature are dramatically lower for a fusion hybrid compared to a stand-alone fusion reactor. This and several other factors are important for our choice to select a mirror machine for the fusion hybrid reactor studies.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-224503 (URN)000333412900011 ()
Conference
Joint Conference of 9th International Conference on Open Magnetic Systems for Plasma Confinement (OS) and 3rd International Workshop on Plasma Material Interaction Facilities for Fusion Research (PMIF), AUG 27-31, 2012, Tsukuba, JAPAN
Available from: 2014-05-14 Created: 2014-05-13 Last updated: 2017-12-05Bibliographically approved
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