| 1. |
- Dykin, Victor, 1985, et al.
(författare)
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Qualitative and quantitative investigation of the propagation noise in various reactor systems
- 2014
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Ingår i: Progress in Nuclear Energy. - : Elsevier BV. - 0149-1970. ; 70, s. 98-111
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Tidskriftsartikel (refereegranskat)abstract
- The space-dependent neutron noise, induced by propagating perturbations (propagation noise for short) is investigated in a one-dimensional homogeneous model of various reactor systems. By using two-group theory, the noise in both the fast and the thermal group is calculated. The purpose is to investigate the dependence of the properties of the space-dependent fast and thermal propagation noise on the static neutron spectrum as well as on the presence of the fluctuations of several cross sections. The motivation for this study arose in connection with recent work on neutron noise in molten salt reactors (MSR) with propagating fuel of various compositions. Some new features of the induced noise were observed, but it was not clear whether these were due to the propagating perturbation alone, or to the propagation of the fuel and hence that of the delayed neutron precursors. The present study serves to clarify the significance of the spectral properties of the different cores through calculating the propagation noise in four different reactor systems, as well as considering the influence of the perturbation of the various cross sections. By comparing the results with those obtained in MSR, the effect of the moving fuel on the propagation noise is clarified. It is shown that in fast systems the noise in the fast group is much larger than in the thermal group and hence can gain diagnostic importance. It is also shown that the coexistence of several cross section fluctuations leads to qualitatively and quantitatively new characteristics of the noise, hence it is important to model the effect of e.g. temperature fluctuations of the coolant in a proper way. (C) 2013 Elsevier Ltd. All rights reserved.
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| 2. |
- Jonsson, Anders, 1984, et al.
(författare)
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Analytical investigation of the properties of the neutron noise induced by vibrating absorber and fuel rods
- 2012
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Ingår i: Kerntechnik. - : Walter de Gruyter GmbH. - 0932-3902 .- 2195-8580. ; 77:5, s. 371-380
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Tidskriftsartikel (refereegranskat)abstract
- Analytical solution methods for the neutron noise in a one-dimensional multi-region system in two-group theory, which have so far been based on the adjoint function technique, are extended here to using the forward Green's function technique. The forward Green's functions were calculated analytically for a noise source in a core surrounded by reflector regions at both sides. It is shown that with symbolic computation methods, the forward Green's function can be used for the calculation of the space- and frequency-dependent noise in the first order approximation for arbitrary noise sources which have an analytical representation. The properties of the induced neutron noise were investigated for vibrations of both absorbers and fuel assemblies, with two representations of the noise sources: a point-like source which corresponds to the vibrations of a fuel rod, and a finite width source which corresponds to vibrations of a fuel assembly The contributions of the components induced by the fluctuations of the various types of macroscopic cross sections in the total noise are also discussed and the information content of the noise in the fast group is explored for the identification of fuel assembly vibrations.
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| 3. |
- Jonsson, Anders, 1984, et al.
(författare)
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Two-group theory of neutron noise in Molten Salt Reactors
- 2011
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 38:6, s. 1238-1251
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Tidskriftsartikel (refereegranskat)abstract
- In a previous paper, the kinetics, dynamics and the neutron noise in a Molten Salt Reactor (MSR) was investigated in a simple homogeneous reactor model in one-group diffusion theory. In this paper those investigations are extended to two-group theory in the same reactor model. In addition, unlike in the previous paper where in the quantitative work data from a thermal LWR were used, here material data of a conceptual MSR with a thermal spectrum and thorium fuel are used, along with data from both fast and thermal LWRs. Among other things, the relative weight and the range of the local component is investigated. It is found that the strong neutronic coupling in an MSR, which was pointed out in the preceding paper, diminishes the role of the local component as compared to light water reactors. Some further new features of the noise in MSR, not directly related to the two-group approach, are also found. (C) 2011 Elsevier Ltd. All rights reserved.
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| 4. |
- Pazsit, Imre, 1948, et al.
(författare)
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Analytical solutions of the molten salt reactor equations
- 2012
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 50, s. 206-214
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Tidskriftsartikel (refereegranskat)abstract
- The one-group diffusion theory of molten salt reactors in a homogeneous reactor model is revisited. First, the integral terms in the equation for the flux, obtained after the elimination of the delayed neutron precursors, are given a physical interpretation. This gives an understanding of the physical meaning of the concept of infinite fuel recirculation velocity, which eliminates one of the two integral terms, introduced in earlier work in order to find analytic solutions. In the light of the physical interpretation, another approximation, representing a different limiting case can be defined, corresponding to long recirculation times, i.e. no recirculation of the delayed neutron precursors to the core. This approximation incurs the neglecting of the other integral term, and it can also be solved analytically. Finally it is shown that the full equation, without neglecting any of the integral terms, has also a compact analytical solution and it is demonstrated how the case of the infinite velocity can be obtained as a limit case of the full solution. The analytical solutions open up the possibility to study a number of questions in analytical form, such as the calculation of the point kinetic response of the reactor, or the effect of the different boundary conditions. As an illustration, the solutions corresponding to the vanishing of the flux at the extrapolated boundary are compared to those obtained from the logarithmic boundary conditions.
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| 5. |
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| 6. |
- Pazsit, Imre, 1948, et al.
(författare)
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Reactor Kinetics, Dynamic Response, and Neutron Noise in Molten Salt Reactors
- 2011
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Ingår i: Nuclear Science and Engineering. - 0029-5639 .- 1943-748X. ; 167, s. 61-76
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic space- and frequency dependent response of a Molten SaltReactor (MSR) to stationary perturbations is investigated in asimple analytical model. The Green's function of the system isinvestigated in the general case of arbitrary fuel recirculationvelocity and in the limiting case of infinite fuel velocity whichpermits closed form solutions both in the static and dynamic case.It is found that the amplitude of the induced noise is generallyhigher and the domain of the point kinetic behaviour valid up tohigher frequencies than in a corresponding traditional system. Thisis due to the differing behaviour of the delayed neutron precursorsas compared to the traditional case. The MSR equations are notself-adjoint and the adjoint equation and adjoint function have tobe constructed, which is also done here. Finally the space-dependentneutron noise, induced by propagating perturbations of theabsorption cross section is calculated. A number of interestingproperties that are relevant to full size MSRs are found andinterpreted. The results are consistent with those in traditionalsystems but the domains of various behaviour regimes (point kinetic,space dependent etc.) are shifted to higher frequencies or systemsizes.
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| 7. |
- Pazsit, Imre, 1948, et al.
(författare)
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Reactor kinetics, dynamic response and neutron noise in molten salt reactors
- 2010
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Ingår i: International Conference on the Physics of Reactors 2010, PHYSOR 2010. - 9781617820014 ; 2, s. 979-999
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The dynamic space- and frequency dependent response of a Molten Salt Reactor (MSR) to stationary perturbations is investigated in a simple analytical model. The Green's function of the system is investigated in the general case of arbitrary fuel recirculation velocity and in the limiting case of infinite fuel velocity which permits closed form solutions both in the static and dynamic case. It is found that the amplitude of the induced noise is generally higher and the domain of the point kinetic behaviour valid up to higher frequencies than in a corresponding traditional system. This is due to the differing behaviour of the delayed neutron precursors as compared to the traditional case. The MSR equations are not self-adjoint and the adjoint equation and adjoint function have to be constructed, which is also done here. Finally the space-dependent neutron noise, induced by propagating perturbations of the absorption cross section is calculated. A number of interesting properties that are relevant to full size MSRs are found and interpreted. The results are consistent with those in traditional systems but the domains of various behaviour regimes (point kinetic, space dependent etc.) is shifted to higher frequencies or system sizes.
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