scholarly journals THE EFFECT OF POSITIVE TEMPERATURE COEFFICIENTS ON REACTOR STABILITY AND REACTOR TRANSFER FUNCTION

1955 ◽  
Author(s):  
R Siegel ◽  
H Hurwitz
Keyword(s):  
Transfer Function ◽  
Positive Temperature ◽  
Temperature Coefficients ◽  
Reactor Stability ◽  
Reactor Transfer

scholarly journals Review of kinetic modulation experiments in low power nuclear reactors

2020 ◽  
Vol 6 ◽  
pp. 55
Author(s):  
Yifeng Jiang ◽  
Benoit Geslot ◽  
Vincent Lamirand ◽  
Pierre Leconte
Keyword(s):  
Transfer Function ◽  
Kinetic Parameters ◽  
Nuclear Reactors ◽  
Function Analysis ◽  
Noise Analysis ◽  
Reactor Physics ◽  
Reactor Stability ◽  
Safety Improvement ◽  
Transfer Function Analysis ◽  
Reactor Transfer

The safety improvement of nuclear reactors requires continuous efforts in understanding the fundamental physical quantities related to the fission process. In neutronic models, the reactor dynamics is covered by the kinetic parameters to characterize the temporal behavior of the neutron population subject to perturbations. The reactor transfer function is a frequency domain analogy of this temporal description. It can be measured experimentally through transfer function analysis via noise analysis or kinetic modulation, for the study of reactor stability and kinetic parameters. This paper summarizes the experimental measurements of reactor transfer function through kinetic modulation. Extensive work have been conducted experimentally, starting from the beginning of reactor physics research. An overview is given regarding various experimental designs and conducted analyses. The concepts of the modulation system are also discussed. The current work is limited to online contents and internal archives of CEA Cadarache due to difficulties in accessing references traced back to 1950s.

Anomalous Temperature Dependence of the 127I Quadrupole Interaction in Tetraethylstiboniummetaperiodate (C2H5)4SbIO4

1987 ◽  
Vol 42 (3) ◽  
pp. 275-278 ◽  
Author(s):  
Dagmar G. Klobasa ◽  
Paul K. Burkert
Keyword(s):  
Solid State Nmr ◽  
Coupling Constants ◽  
Positive Temperature ◽  
Anomalous Temperature Dependence ◽  
Continuous Change ◽  
Nmr Studies ◽  
Anomalous Temperature ◽  
Gradient Tensor ◽  
Temperature Coefficients ◽  
Quadrupole Coupling

127I solid state NMR studies revealed second order quadrupole effects in (C2H5)4SbIO4 with anomalous positive temperature coefficients of the quadrupole coupling constants. This anomaly is caused by a continuous change of the axes of the electric field gradient tensor.

Positive temperature coefficients of remanence and coercivity in precipitation-hardened Gd–Co–Fe–Cu–Zr alloys

2004 ◽  
Vol 279 (2-3) ◽  
pp. 143-148 ◽  
Author(s):  
Chuan-bing Rong ◽  
Jian Zhang ◽  
Hong-wei Zhang ◽  
Xiao-bo Du ◽  
Shao-ying Zhang ◽  
...  
Keyword(s):  
Positive Temperature ◽  
Temperature Coefficients ◽  
Zr Alloys

Fabrication of (Ba,Pb)TiO3-based tapes with positive temperature coefficients of resistivity by the oxidation of malleable, metal-bearing precursors (the volume identical metal oxidation process)

1999 ◽  
Vol 14 (11) ◽  
pp. 4319-4328 ◽  
Author(s):  
Seyed M. Allameh ◽  
Kenneth H. Sandhage
Keyword(s):  
Oxidation Process ◽  
Cold Drawing ◽  
High Energy ◽  
Positive Temperature Coefficient ◽  
Thermal Treatments ◽  
Positive Temperature ◽  
Metal Oxidation ◽  
Powder Mixtures ◽  
Temperature Coefficients ◽  
Temperature Coefficient Of Resistivity

The feasibility of producing (Ba,Pb)TiO3-based thermistor tapes by the oxidation of malleable, metal-bearing precursors has been demonstrated. Intimate Ba–Pb–Ti–TiO2-bearing powder mixtures, produced by high-energy vibratory milling, were packed within a fugitive metal can and then compacted and formed into tapes of uniform thickness by cold drawing and rolling. The tape-shaped precursors were oxidized and converted into (Ba,Pb)TiO3-based tapes with a series of heat treatments at ≤1120 °C. With proper control of thermal treatments and chemical additions (Sb2O3 + MnO2 dopants), positive-temperature-coefficient-of-resistivity thermistors were produced that exhibited significant increases in resistivity commencing at temperatures ≥350 °C.

Localization of a Noise Source in VVER-1000 Reactor Core Using Neutron Noise Analysis Methods

2010 ◽  
Author(s):  
Hessam Malmir ◽  
Naser Vosoughi ◽  
Ehsan Zahedinejad
Keyword(s):  
Transfer Function ◽  
Noise Source ◽  
Noise Analysis ◽  
Reactor Core ◽  
Dynamic State ◽  
Inversion Method ◽  
Variable Strength ◽  
Neutron Noise ◽  
Spatial Discretisation ◽  
Reactor Transfer

In this paper, localization of a noise source from limited neutron detectors sparsely distributed throughout the core of a typical VVER-1000 reactor is investigated. For this purpose, developing a 2-D neutron noise simulator for hexagonal geometries based on the 2-group diffusion approximation, the reactor dynamic transfer function is calculated. The box-scheme finite difference method is first developed for hexagonal geometries, to be used for spatial discretisation of both 2-D 2-group static and noise diffusion equations. The dynamic state is assumed in the frequency domain which leads to discarding of the time disrcetisation. The developed 2-D 2-group neutron noise simulator calculates both the discretised forward and the adjoint reactor transfer function between a point-like source and its induced neutron noise, by assuming the noise source as an absorber of variable strength type. Benchmarking of the mentioned neutron noise simulator revealed that it works satisfactorily. Finally, by using the inversion method of reconstruction, the location and values of a noise source of the type absorber of variable strength (or reactor oscillator) in VVER-1000 reactor cores are determined. Accuracy of this method is highly acceptable.

Electronic properties of the actinide metals at low temperatures

1963 ◽  
Vol 276 (1367) ◽  
pp. 553-570 ◽  
Keyword(s):  
Electrical Resistivity ◽  
Low Temperatures ◽  
Negative Temperature Coefficient ◽  
Negative Temperature ◽  
Al Alloys ◽  
Positive Temperature ◽  
Positive Coefficient ◽  
Disorder Effects ◽  
Temperature Coefficients ◽  
Spin Disorder

The electrical resistivity and thermoelectric power of thorium, uranium, neptunium and plutonium have been measured down to liquid-helium and liquid-hydrogen temperatures. The resistivities are relatively high, especially those of neptunium and plutonium, while all the thermoelectric powers show complicated temperature relations. The temperature dependence of the resistance of a-plutonium is abnormal, being characterized by a small negative temperature coefficient above 105 °K and a large positive coefficient below this temperature. Some plutonium rich d-Pu + Al alloys also show similar behaviour. An explanation in terms of spin-disorder effects seems most reasonable, and it is suggested that both a- and d-plutonium may be antiferromagnetic. The resistance—temperature curves of uranium and neptunium also are unusual in that the positive temperature coefficients decrease monotonically with rising temperature. Possible reasons for this have been discussed.

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