15 research outputs found
Supercritical water-cooled nuclear reactors: thermodynamic-cycles options
Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.Currently there are a number of Generation IV
SuperCritical Water-cooled nuclear Reactor (SCWR)
concepts under development worldwide. The main objectives
for developing and utilizing SCWRs are: 1) Increase gross
thermal efficiency of current Nuclear Power Plants (NPPs)
from 33 – 35% to approximately 45 – 50%, and 2) Decrease
the capital and operational costs and, in doing so, decrease
electrical-energy costs (~$1000 US/kW or even less).
SCW NPPs will have much higher operating parameters
compared to current NPPs (i.e., pressures of about 25 MPa
and outlet temperatures up to 625°C). Additionally, SCWRs
will have a simplified flow circuit in which steam generators,
steam dryers, steam separators, etc. will be eliminated.
Furthermore, SCWRs operating at higher temperatures can
facilitate an economical co-generation of hydrogen through
thermo-chemical cycles (particularly, the copper-chlorine
cycle) or direct high-temperature electrolysis.
To decrease significantly the development costs of a
SCW NPP, to increase its reliability, and to achieve similar
high thermal efficiencies as the advanced fossil steam cycles
it should be determined whether SCW NPPs can be designed
with a steam-cycle arrangement that closely matches that of
mature SuperCritical (SC) fossil power plants (including their
SC turbine technology). The state-of-the-art SC steam cycles
in fossil power plants are designed with a single-steam reheat
and regenerative feedwater heating and reach thermal steamcycle
efficiencies up to 54% (i.e., net plant efficiencies of up
to 43% on a Higher Heating Value (HHV) Basis).
Therefore, simplified no-reheat, single-reheat, and
double-reheat cycles without heat regeneration and a singlereheat
cycle with heat regeneration based on the expected
steam parameters of future SCW NPPs were analyzed in
terms of their thermal efficiencies.
On this basis, several conceptual steam-cycle
arrangements of pressure-tube SCWRs, their corresponding
T–s diagrams and steam-cycle thermal efficiencies (based on
constant isentropic turbine and polytropic pump efficiencies)
are presented in this paper.vk201
Motor Deficits and Decreased Striatal Dopamine Receptor 2 Binding Activity in the Striatum-Specific Dyt1 Conditional Knockout Mice
DYT1 early-onset generalized dystonia is a hyperkinetic movement disorder caused by mutations in DYT1 (TOR1A), which codes for torsinA. Recently, significant progress has been made in studying pathophysiology of DYT1 dystonia using targeted mouse models. Dyt1 ΔGAG heterozygous knock-in (KI) and Dyt1 knock-down (KD) mice exhibit motor deficits and alterations of striatal dopamine metabolisms, while Dyt1 knockout (KO) and Dyt1 ΔGAG homozygous KI mice show abnormal nuclear envelopes and neonatal lethality. However, it has not been clear whether motor deficits and striatal abnormality are caused by Dyt1 mutation in the striatum itself or the end results of abnormal signals from other brain regions. To identify the brain region that contributes to these phenotypes, we made a striatum-specific Dyt1 conditional knockout (Dyt1 sKO) mouse. Dyt1 sKO mice exhibited motor deficits and reduced striatal dopamine receptor 2 (D2R) binding activity, whereas they did not exhibit significant alteration of striatal monoamine contents. Furthermore, we also found normal nuclear envelope structure in striatal medium spiny neurons (MSNs) of an adult Dyt1 sKO mouse and cerebral cortical neurons in cerebral cortex-specific Dyt1 conditional knockout (Dyt1 cKO) mice. The results suggest that the loss of striatal torsinA alone is sufficient to produce motor deficits, and that this effect may be mediated, at least in part, through changes in D2R function in the basal ganglia circuit
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Available from TIB Hannover: QN 278(B) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman