| 1. |
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| 2. |
- Ahlström, Per-Erik, et al.
(författare)
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- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Persson, Carl Magnus, et al.
(författare)
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Analysis of reactivity determination methods in the subcritical experiment Yalina
- 2005
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 554:1-3, s. 374-383
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Tidskriftsartikel (refereegranskat)abstract
- Different reactivity determination methods have been investigated, based on experiments performed at the subcritical assembly Yalina in Minsk, Belarus. The development of techniques for on-line monitoring of the reactivity level in a future accelerator-driven system (ADS) is of major importance for safe operation. Since an ADS is operating in a subcritical mode, the safety margin to criticality must be sufficiently large. The investigated methods are the Slope Fit Method, the Sjostrand Method and the Source Jerk Method. The results are compared with Monte Carlo simulations performed with different nuclear data libraries. The results of the Slope Fit Method are in good agreement with the Monte Carlo simulation results, whereas the Sjostrand Method appears to underestimate the criticality somewhat. The Source Jerk Method is subject to inadequate statistical accuracy.
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| 4. |
- Persson, C. -M, et al.
(författare)
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Comparison of neutron kinetic parameters of the subcritical ads experiments Yalina and Yalina Booster
- 2005
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Konferensbidrag (refereegranskat)abstract
- Subcritical experiments, devoted to investigation of characteristics of accelerator-driven systems, have been constructed at the Joint Institute for Power and Nuclear Research - Sosny in Minsk, Belarus. Different methods for reactivity determination have previously been investigated in the thermal ADS experiment "Yalina", and recently, a coupled fast-thermal facility "Yalina Booster" was launched. This study presents the neutron kinetic characteristics of the Yalina and the new Yalina Booster setups, and points out some important differences. For the Yalina setup, neutron kinetic parameters, such as keff, α, βeff and Λ have been determined by Monte Carlo simulations and they have previously been verified experimentally. For Yalina Booster, these parameters have been estimated by Monte Carlo simulations in a preliminary study, and they will be verified in upcoming experiments.
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| 5. |
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| 6. |
- Polanski, A., et al.
(författare)
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Power upgrade of the subcritical assembly in Dubna (SAD) to 100 kW
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 562:2, s. 879-882
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Tidskriftsartikel (refereegranskat)abstract
- The paper present results of Monte Carlo modeling of an Experimental Accelerator Driven System (ADS), which employs a subcritical assembly and a 660 MeV proton accelerator operating at the Laboratory of Nuclear Problems of the Joint Institute for Nuclear Research in Dubna. The mix of oxides PuO2 + UO2 MOX fuel designed for the reactor will be adopted for the core of the assembly. The design of the experimental subcritical assembly in Dubna (SAD) is based on the core with a nominal unit capacity of 30 kW (thermal). This corresponds to the multiplication coefficient K-eff = 0.95 and the accelerator beam power of I kW. A subcritical assembly has been modeled in order to increase power of this experimental set up. Different options for the target and fuel elements have been considered.
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| 7. |
- Seltborg, Per, et al.
(författare)
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Definition and application of proton source efficiency in accelerator driven systems
- 2003
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Ingår i: Nuclear science and engineering. - 0029-5639 .- 1943-748X. ; 145:3, s. 390-399
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
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| 9. |
- Seltborg, Per
(författare)
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External Source Effects and Neutronics in Accelerator-driven Systems
- 2003
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transmutation of plutonium and minor actinides inaccelerator-driven systems (ADS) is being envisaged for thepurpose of reducing the long-term radiotoxic inventory of spentnuclear reactor fuel. Consequently, the physics of sub-criticalsystems are being studied in several different experimentalprograms across the world, one of them being the MUSE(MUltiplication of External Source) program. In theseexperiments, an intense external neutron source is coupled to asub-critical core. In order to investigate the neutronics andsourceeffects in a sub-critical system, Monte Carlosimulations have in this thesis been performed for a modelrepresentative of the MUSE-4 experiments. The investigationshave focused on three different neutronic parameters; theneutron energy spectrum, the external neutron source efficiency(φ*) and the dynamic neutron source response.In order to study the beam power amplification of an ADS, wehave introduced a new parameter, the proton source efficiency(Ψ*). Ψ* represents the average importance of theexternal proton source, relative to the average importance ofthe eigenmode neutron production. It is defined in analogy withthe neutron source efficiency φ*, but relates the corepower to the source protons instead of to the source neutrons.φ* is commonly used in the physics of sub-criticalsystems, driven by any external neutron source (spallationsource, (d,d), (d,t),252Cf spontaneous fission etc.). On the contrary,Ψ* has been defined only for ADS studies, where the systemis driven by a proton-induced spallation source. The mainadvantages with using Ψ* instead of φ* are that theway of defining the external source is unique and that Ψ*is proportional to the core power divided by the proton beampower, independently of the neutron source distribution. Thesecond part of this thesis has focused on studying Ψ* as afunction of different system parameters, thereby providing abasis for an ADS design with optimal proton beamamplification.
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| 10. |
- Seltborg, Per, et al.
(författare)
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Impact of heterogeneous Cm-distribution on proton source efficiency in accelerator-driven systems
- 2004
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Ingår i: Proceedings of the PHYSOR 2004. - 0894486837 ; , s. 489-497
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Konferensbidrag (refereegranskat)abstract
- The proton source efficiency (ψ*) was studied for homogeneous and heterogeneous distributions of minor actinides in a nitride-fuelled and lead-bismuth-cooled accelerator-driven system. The findings from the MCNPX simulations indicate that, compared to a homogeneous configuration, a gain in ψ* by up to 16% can be obtained by distributing the minor actinides heterogeneously, Cm being placed in the inner zone of the active core and Am in the outer zone. The reason for this is the higher fission probability for neutrons for Cm than for Am in the energy range below 1.0 MeV. Moreover, a comparative study of two different physics packages available in MCNPX, the Bertini and the CEM models, has been performed, focusing on the production of neutrons in the spallation target and on the proton source efficiency. The Bertini model was found to produce a higher number of neutrons in the low-energy range (below ∼15 MeV) than the CEM model. Consequently, the Bertini model also over-estimates ψ* by about 10%, compared to the CEM model.
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| 11. |
- Seltborg, Per, et al.
(författare)
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Investigation of neutron source effects in subcritical media and application to a model of the MUSE-4 experiments
- 2001
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Konferensbidrag (refereegranskat)abstract
- Monte Carlo simulations have been performed to investigate the neutron sourceeffects in a sub-critical media successively coupled to a (d,d)-source, a (d,t)-source and aspallation source. The investigations have focused on the neutron energy spectra in thefuel and on the source relative efficiency j*. The calculations have been performed forthree sub-critical configurations, representative of the coming MUSE-4 experiments.The Monte Carlo codes MCNP and MCNPX have been used to compute j*. j*has been found to be low for the (d,d)-source (~1.35 compared to 1.0 for an averagefission neutron), while considerably higher for the (d,t)-source (~2.15) and the spallationsource (~2.35). The high value of j* for the spallation source has been shown to be dueto the fraction of high-energy neutrons (17 % of total source with En > 20 MeV) bornfrom spallation, which contribute for 50 % to the total number of fission neutronsproduced in the core. The variations of j* with neutron importance have also beenstudied for some spherical configurations with a (d,d)- and a (d,t)-source. For the class ofvariations considered here, j* was found to remain constant or increase only slightly inthe interval 0.70 < keff < 0.996.
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| 12. |
- Seltborg, Per, et al.
(författare)
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Proton source efficiency for heterogeneous distribution of actinides in the core of an accelerator-driven system
- 2006
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Ingår i: Nuclear science and engineering. - 0029-5639 .- 1943-748X. ; 154:2, s. 202-214
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Tidskriftsartikel (refereegranskat)abstract
- The distribution of actinides in the core of an accelerator-driven system loaded with plutonium, americium, and curium has been studied in order to optimize the proton source efficiency psi*. The optimization of psi* was performed by keeping some important characteristics of the system, e.g., the radial power profile and the reactivity of the core, constant. One of the basic assumptions of the study, that the magnitude of psi* is sensitive primarily to the composition of actinides in the inner part of the core, whereas only marginally to that in the outer part, has been confirmed. It has been shown that the odd-N nuclides (those nuclides with an even number of neutrons) in general and Am-241 and Cm-244 in particular have favorable properties with respect to improving psi* if they are placed in the innermost part of the core. The underlying reason for this phenomenon is that the energy spectrum of the source neutrons in the inner part of the core is harder than that of the average fission neutrons. Moreover, it has been shown that loading the inner part of the core with only curium increases psi* by similar to 7%. Plutonium, on the other hand, in particular high-quality plutonium consisting mainly of Pu-239 and Pu-241, was found to be a comparatively source inefficient element and is preferably located in the outer part of the core. The differences in psi* are due to combined effects from relative changes in the average fission and capture cross sections and in the average fission neutron yield.
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| 13. |
- Seltborg, Per, et al.
(författare)
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Radiation shielding of high-energy neutrons in SAD
- 2005
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 550, s. 313-328
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Tidskriftsartikel (refereegranskat)abstract
- The radiation fields and the effective dose at the Sub-critical Assembly in Dubna (SAD) have been studied with the Monte Carlo code MCNPX. The effective dose above the shielding, i.e. in the direction of the incident proton beam of 3.0 mu A, was found to be about 190 mu Sv h(-1). This value meets the dose limits according to Russian radiation protection regulations, provided that access to the rooms in this area is not allowed for working personnel during operation.By separating the radiation fields into a spallation- and a fission-induced part, it was shown that the neutrons with energy higher than 10MeV, originating exclusively from the proton-induced spallation reactions in the target, contribute for the entire part of the radiation fields and the effective dose at the top of the shielding. Consequently, the effective dose above the SAD reactor system is merely dependent on the proton beam properties and not on the reactivity of the core.
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| 14. |
- Seltborg, Per, 1973-
(författare)
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Source efficiency and high-energy neutronics in accelerator-driven systems
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 15. |
- Seltborg, Per, et al.
(författare)
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Source efficiency as function of fuel and coolant in accelerator-driven systems
- 2006
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 33:9, s. 829-832
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the efficiency of spallation neutron sources for different combinations of coolant and fuel in 80 MWth, sub-critical, cores. It has been found that the proton source efficiency, psi*, is reduced by 10% when switching coolant from helium to lead-bismuth eutectic. Substituting MOX fuel with an americium based fuel, results in another 10% reduction of psi*. The relatively high source efficiencies found for prototype accelerator-driven systems, using standard MOX fuel and helium coolant, may thus be difficult to achieve in future systems dedicated to the transmutation of higher actinides. Our results are in agreement with previous investigations of the dependence of the source efficiency on the selection of coolant.
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