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Analysis of Accidents in Sodium-Cooled Fast ReactorsWutzler, Whitney A. 28 July 2011 (has links)
No description available.
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Developmental Analysis and Design of a Scaled-down Test Facility for a VHTR Air-ingress AccidentArcilesi, David J., Jr. 26 June 2012 (has links)
No description available.
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Fuel and Core Physics Considerations for a Pressure Tube Supercritical Water Cooled ReactorMcDonald, Michael H. 10 1900 (has links)
<p>The supercritical water cooled reactor (SCWR) is a Generation IV reactor concept that features light water coolant in a supercritical state. Canada is developing a pressure tube variant of the supercritical water reactor as an evolution of the CANDU reactor. The main advantages of the pressure tube SCWR are an improved thermal efficiency over current reactors, enhanced safety through passive safety features, and plant simplifications. The objective of this thesis was to investigate current fuel and core designs for the Canadian SCWR concept.</p> <p>Simulations of 2-D lattice cells for fuel assemblies containing 43 and 54 fuel elements were performed using the neutron transport code WIMS-AECL. Safety parameters and fuel burnup performance were investigated here. Three dimensional full core simulations were performed using the diffusion code RFSP. These studies examined batch fueling, cycle length, radial and axial power profiles, linear element ratings, and reduction of axial power peaking through graded enrichment along the fuel channel. Finally, a study of reactivity transients was performed using the FUELPIN heat transfer/point kinetics code.</p> <p>The main results of the studies show that the coolant density change that occurs as water passes through the pseudocritical point strongly affects fuel performance. It is concluded that the 54 element assembly design is acceptable in terms of coolant void reactivity performance with lattice pitch smaller than 26 cm. To meet the burnup target, a fuel enrichment of about 5% is required. From the RFSP studies, this level of fuel enrichment will provide an operating period of 370 days between refueling. Relatively high axial power peaking is observed at the beginning of cycle conditions. A main finding is that the proposed reactor power level of 2540 MWth produces unacceptably high linear element ratings. This is confirmed using the FUELPIN code. A reduction in linear element rating is suggested for consideration.</p> / Master of Applied Science (MASc)
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Innovative Analysis Techniques for Canadian SCWR NeutronicsSharpe, Jason 11 1900 (has links)
Knowledge of the effects of nuclear data uncertainties and physics approximations is crucial
for the development, design, operation, and accident mitigation, of nuclear power
plants. A framework to create a simulated fuel bundle, based on sensitivities and similarities,
has been developed. The methodology allows safe-to-handle fuel to be manufactured
such that it mimics irradiated fuel and can be used to reduce simulation uncertainties and
better predict an application’s response. In this work, similarity values of ck = 0.967,
E = 0.992, and G = 0.891 were found between between the irradiated fuel, and non-irradiated
simulated fuel. In addition, a set of ZED-2 experiments has been analyzed
that are applicable to an SCWR nuclear data adjustment and simulation bias determination.
This was shown through high sensitivity coverage of many important nuclides,
however, a low completeness value of R=0.24 indicates the set of 39 experiments alone is
not sufficient for an accurate bias determination. Lastly, a technique has been presented
that reduces diffusion calculation errors through the use of novel and practical mean
discontinuity factors. The discontinuity factors have shown to reduce maximum channel
power errors by up to 6.7%, and reactivity errors by 2.6 mk, compared to conventional
analysis techniques. / Thesis / Doctor of Philosophy (PhD) / Use of practical discontinuity factors has shown to reduce channel power predictions significantly. Furthermore, an experimental and numerical technique has been developed to improve neutron transport predictions. Finally, a set of experiments have been modeled and simulated to determine their applicability to the SCWR.
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Continuous Beam of Laser-Cooled Ytterbium Atoms for Precision MeasurementsRathod, Ketan D January 2014 (has links) (PDF)
What if an elementary particle such as an electron had an intrinsic electric dipole moment (EDM)? Existence of such an EDM would be an indication of time-reversal symmetry
violation in the laws of Physics. The Standard model of Physics is considered incomplete, and theories that go beyond the standard model predict existence of such EDM’s within experimental reach. Experiments that search for their existence serve as a test bed for these theories. Use of laser-cooled Yb atoms launched in a fountain for EDM search has been proposed earlier.
This thesis describes the main experimental work on generating a continuous cold
beam of Yb atoms using laser cooling. Such cold beams are ideal for performing EDM
experiments and have several advantages over the more common pulsed fountain. We
demonstrate two ways to achieve this (i) extracting the beam from atoms trapped in 2-
dimensions and (ii) deflecting the atomic beam using 1D-optical molasses. We find that
the latter method gives a longitudinal temperature of 41 mK, which is a factor of 3 better than the former one. We also demonstrate the implementation of Ramsey’s separated oscillatory field technique in a thermal beam to measure the larmor precession frequency with high precision. This serves as a first step towards implementation with cold beam.
Extending the work reported here, we suggest future experiment for measuring an EDM.
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Influence of geometric and environmental parameters on air-cooled steam condenser performanceJoubert, Retief 03 1900 (has links)
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Air-cooled steam condensers (ACSCs) are used in the power generation industry to directly
condense turbine exhaust steam in areas where cooling water is expensive or unavailable.
Large axial flow fans force ambient air through A-frame heat exchanger bundles made up of a
number of rows of finned tubes through which the steam is ducted and consequently
condensed during the heat transfer process to the air. The heat rejection rate or performance
of an ACSC is proportional to the air mass flow rate, determined by fan volumetric
performance, and the temperature difference between the finned tubes and the air.
The air flow through a 30 fan ACSC (termed the generic ACSC) operating under windy
conditions is solved using the commercial computational fluid dynamics (CFD) code FLUENT
and the required data is extracted from the solution to calculate performance trends. It is
found that fan performance is reduced due to a combination of factors. The first is additional
upstream flow losses caused by separated flow occurring primarily at the leading edge of the
ACSC and secondarily at the fan bellmouth inlets. The second factor leading to reduced fan
performance is the presence of distorted flow conditions at the fan inlets. Hot plume air
recirculation is responsible for decreased ACSC thermal performance due to increased fan inlet
air temperatures. It is found that reduced fan performance is the greater contributor to
reduced ACSC performance.
The performance effects of varying two geometrical parameters of the generic ACSC, namely
the fan platform height and the windwall height, are investigated under windy conditions. It is
found that each parameter is linked to a specific mechanism of performance reduction with
the fan platform height affecting fan performance and the windwall height affecting
recirculation. The respective platform and windwall heights specified for the generic ACSC are
found to provide acceptable performance results.
To mitigate wind induced performance reductions a number of modification and additions to
the ACSC are investigated. These primarily aim at improving fan performance and included the
addition of walkways or skirts, the addition of wind screens beneath the fan platform,
removing the bellmouth fan inlets, using different types of fans and increasing fan power. The
addition of a periphery walkway and windscreens is considered to be the most practical
methods of improving ACSC performance under windy conditions. The generic ACSC is
modified to include both modifications and under high wind conditions the performance is
found to increase measurably. The modifications also resulted in the ACSC performance being
less sensitive to wind direction effects. / AFRIKAANSE OPSOMMING: Lugverkoelde kondensators word in die kragopwekkings industrie gebruik om turbine
uitlaatstoom te kondenseer, veral in gebiede waar verkoelingwater duur of onbeskikbaar is.
Aksiaalvloei-waaiers forseer omgewingslug deur A-raam warmteuitruiler bondels wat bestaan
uit verskeie rye vinbuise. Die uitlaatstoom vloei in die vinbuise en kondenseer as gevolg van
die warmteoordrag na die lug. Die warmteoordragkapasiteit van die lugverkoelde stoom
kondensator is eweredig aan die massavloei-tempo van die lug, wat bepaal word deur die
waaierwerkverigting, en die temperatuur verskil tussen die vinbuise en die lug.
Die lugvloei deur 'n 30 waaier lugverkoelde stoom kondensator (genoem die generiese
lugverkoelde stoom kondensator) onderworpe aan winderige toestande word opgelos deur die
gebruik van die kommersiële vloeidinamika-pakket, FLUENT. Die nodige data is onttrek uit die
oplossing en werkverrigting neigings is bereken. Dit is gevind dat waaierwerkverigting
verminder as gevolg van 'n kombinasie van faktore. Die eerste is bykomende vloeiverliese wat
veroorsaak word deur vloeiwegbreking wat plaasvind primêr by die voorste rand van die
lugverkoelde stoom kondensator asook by die klokvormige waaier-inlate. 'n Tweede faktor wat
lei tot vermindere waaierwerkverigting is die teenwoordigheid van lugvloeiversteurings by die
waaier-inlate. Hersirkulering van warm pluim lug is ook verantwoordelik vir verminderde
lugverkoelde stoom kondensator werkverrigting. Daar word bevind dat die vermindering in
waaierwerkverrigting die grootste bydraende faktor tot vermindere lugverkoelde stoom
kondensator werkverrigting is.
Die effek van verandering van twee geometriese lugverkoelde stoom kondensator parameters,
naamlik die waaierplatformhoogte en die windwandhoogte is ondersoek onder winderige
toestande. Daar word bevind dat elk van die parameters gekoppel is aan 'n spesifieke
meganisme van vermindere lugverkoelde stoom kondensator verrigting: Die
waaierplatformhoogte beïnvloed waaierverrigting terwyl die windwandhoogte hersirkulering
beinvloed. Daar word ook bevind dat die onderskeie waaierplatform- and windwandhoogtes
van die generiese lugverkoelde stoom kondensator, van so 'n aard is dat dit aanvaarbare
werkverrigting tot gevolg het.
Om verlaging in werksverrigting in winderige toestande te verminder is verskeie modifikasies
en byvoegings tot die lugverkoelde stoom kondensator ondersoek wat primêr gemik is op
verbetering in waaierwerkverigting. Die ondersoek dek die byvoeging van 'n loopvlak, die
byvoeging van windskerms onder die waaierplatform, verwydering van die klokvormige
waaier-inlate, die gebruik van verskillende waaiers en die verhoging van waaierdrywing. Daar
was besluit dat die byvoeging van 'n loopvlak rondom die rand van die lugverkoelde stoom
kondensator en die byvoeging van windskerms die mees praktiese manier was om die
lugverkoelde stoom kondensator verigting te verbeter. Die generiese lugverkoelde stoom
kondensator was aangepas om beide veranderings in te sluit en meetbare verbetering in
werkrigting was verkry. Die veranderings het ook meegebring dat die lugverkoelde stoom
kondensator minder sensitief is vir windrigting effekte.
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Performance and thermo-mechanical cost evaluation of API 661 air-cooled heat exchangersAckers, Mogamat Sadley 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The optimal design of a heat exchanger for a specified heat transfer, pressure drop
and set of ambient conditions entails minimising space, weight, material usage and
overall cost. However, the variables which influence the performance as well as the
overall cost of a heat exchanger are not related in a simple way and it is not obvious
which variables play the most important roles (Perry & Green, 1997:11-44).
Air cooled heat exchangers (ACHEs) are normally designed in three stages, by
different experts in the field, and with the aid of specially designed software. This
project combines these thermal, mechanical and cost estimation processes into a MS
Excel model which makes it easier to see the influence that design parameters have
on the overall cost of the heat exchanger.
A thermal model was created to design an API 661 (2006) ACHE. The results from
this model compared well with those of HTRI Xchanger Suite 6.0 software, with
HTRI being more conservative in its design mode.
A mechanical design model was then developed, which uses as inputs the outputs of
the thermal design. The output from this mechanical design model is the minimum
material thicknesses based on the stress criteria of Appendix 13 of ASME VIII div 1
(2007) Boiler and Pressure Vessel Code.
An experiment on a finned tube bundle was performed in a wind tunnel facility to
determine performance characteristics and compare these to existing correlations in
literature. The results showed that both the heat transfer coefficient (h) and loss
coefficient (Eu) correlations proposed by Ganguli et al. (1985) closely predict the
measured data, and were consequently used in the thermal design model. During this
experiment it was also shown that the tube bundle reached 8 % - 9 % of its allowable
internal fouling factor, due to rust build up inside the tubes, and in a testing period of
only nine days. The thermal and mechanical models were then combined with a cost estimation
process to perform both a thermal and mechanical parametric study. The thermal
study showed that to obtain an optimal solution, the design must attempt to maximise
the length, increase the width rather than the number of bays, make use of two
bundles per bay with fewer but larger fans and employ a large number of tube rows
with the least number of tube passes. These guidelines were used to create an initial
design; Excel Solver was then applied to locate the optimum combination of bundle
length and width that result in the minimum heat exchanger cost. Two mechanical considerations were investigated, both requiring additional welding
and thus increased welding cost. Firstly the use of stay plates result in reduced
required plate thicknesses according to the stress criteria since it provides additional
stiffness in the header box design. Secondly the use of more (but smaller) nozzles as
opposed to less (but larger) nozzles was also considered. The mechanical parametric
study showed no specific trends, but both considerations should still be checked as it
can be cost beneficial in a specific design. / AFRIKAANSE OPSOMMING: Optimale ontwerp van ’n warmteoordraer vir ’n gespesifiseerde warmteoordrag,
drukval en stel van omgewingstoestande behels die minimalisering van ruimte,
gewig, materiaalverbruik en algehele koste. Die veranderlikes wat egter die
werkverrigting, sowel as die algehele koste, van ’n warmteoordraer beïnvloed, hou
nie in ’n eenvoudige sin met mekaar verband nie, en dit is nie vanselfsprekend watter
veranderlikes die belangrikste rolle speel nie (Perry & Green, 1997:11-44).
Lugverkoelde warmteoordraers (air-cooled heat exchangers of ACHEs) word
normaalweg in drie fases ontwerp deur verskillende kundiges in die veld en met
behulp van spesiaal ontwerpte programmatuur. Hierdie studie kombineer dié
termiese, meganiese en kosteberamingsprosesse in ’n MS Excel-model, wat dit
makliker maak om van te stel wat die invloed wat ontwerpparameters op die algehele
koste van die hitteruiler is.
’n Termiese model is geskep om ’n “API 661 (2006) ACHE” te ontwerp. Die
resultate van hierdie model het goed vergelyk met dié van die HTRI Xchanger Suite
6.0-program, met HTRI meer konserwatiew in die ontwerp af.
Na die termiese model geskep is, is ’n meganieseontwerp-model ontwikkel, wat as
insette die uitsette van die termiese ontwerp gebruik het. Die uitset van hierdie
meganieseontwerp-model is die minimum materiaaldikte gebaseer op die
spanningskriteria van Bylae 13 van “ASME VIII div 1 (2007) Boiler and Pressure
Vessel Code.” Daar is ’n eksperiment op ’n vinbuisbundel in ’n windtonnelfasiliteit uitgevoer om
werkverrigtingskarakteristieke te bepaal en dit met bestaande korrelasies in die
literatuur te vergelyk. Die resultate het getoon dat sowel die
warmteoordragskoëffisiënt (h) en die verlieskoeffisient (Eu) korrelasies, voorgestel
deur Ganguli et al. (1985), die data wat gemeet is akkuraat voorspel, en gevolglik is
die korrelasies in die termieseontwerp-model gebruik. Gedurende die eksperiment is
ook getoon dat die buisbundel 8 % - 9 % van sy toelaatbare interne-aanpakkingfaktor
bereik het vanweë roesopbou binne-in die buise, en dit in ’n toetsingtydperk van slegs
nege dae.
Die termiese en meganiese modelle was toe gekombineer met ’n
kosteberamingsproses om ’n termiese sowel as ’n meganiese parametriese studie uit
te voer. Die termiese studie het getoon dat, om ’n optimale oplossing te verkry, die
ontwerp moet poog om die lengte te maksimeer; die wydte eerder as die aantal strate
(bays) te vermeerder; van twee bundels per straat gebruik te maak met minder, maar
groter waaiers; en ’n groot aantal buisrye met die kleinste hoeveelheid buisdeurvloeiweë in te span. Hierdie riglyne is gebruik in ’n aanvanklike ontwerp,
waarna die Excel Solver gebruik is om die optimale kombinasie van bundellengte en
–wydte vas te stel met die oog op die laagste moontlike warmteoordraerkoste.
Twee meganiese oorwegings is ondersoek wat albei addisionele sweiswerk sou vereis
en dus tot verhoogde sweiskoste sou lei. Eerstens lei die gebruik van ankerplate (stay
plates) tot ’n vermindering in die vereiste plaatdiktes volgens die spanningskriteria,
aangesien dit addisionele stewigheid in die spruitstukhouerontwerp bied. Tweedens is
die gebruik van meer (maar kleiner) spuitstukke teenoor minder (maar groter)
spuitstukke ook oorweeg. Die meganiese parametriese studie het geen spesifieke
voorkeurneigings getoon nie, maar altwee oorgewings moet nog getoets word want
dit kan koste voordelig word in 'n spesifieke ontwerp.
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Simultaneous measurement of air flow conditions and resultant blade and gearbox loading at large-scale cooling system fansMuiyser, Jacques 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Axial flow fans used in large-scale air-cooled steam condensers (ACSCs) may operate
under distorted inflow conditions. These conditions occur due to the prevailing wind
conditions, the presence of buildings, and the location of the fan within the ACSC. Fans
located on the periphery of the ACSC are affected the most due to their exposure to
strong winds and the inner fans drawing in air past them. Distorted inflow conditions
cause varying fan blade and gearbox loading conditions.
The purpose of the investigation was to simultaneously measure the inlet air flow
and the resultant blade and gearbox loading conditions of a single fan located on the
periphery of a large-scale ACSC. Inlet and heat exchanger bundle outlet air flow velocities
were measured using a combination of ultrasonic and propeller anemometers while
blade loading was measured with strain gauges attached at the neck of the specific blade
being monitored. Strain gauges were also attached to the low-speed fan shaft to measure
gearbox loading.
Measurements were recorded over a period of 8 days where it was found that increased
wind resulted in increased air flow in the axial direction of the fan, which then
caused a reduction in average blade loading. This was due to a decreased static pressure
rise over the fan. The fan blade was found to vibrate at its own natural frequency of
6 Hz when excited by the variable aerodynamic loading. The aerodynamic loading was
extracted from the measured data and was found to correlate well with previous experimental
work performed by Bredell et al. (2006a). Shaft bending stresses and torque were
found to oscillate at the fan’s rotational frequency of 2Hz with a large torque exerted on
the shaft during fan start-up. / AFRIKAANSE OPSOMMING: Aksiaalvloeiwaaiers wat by groot lugverkoelde stoomkondensors gebruik word, werk
dikwels onder verwronge inlaat lugvloei toestande wat geskied as gevolg van heersende
winde, die teenwoordigheid van geboue en die posisie van die waaier in die kondensor.
Waaiers wat geleë is op die rand van die kondensor word die meeste beïnvloed as gevolg
van blootstelling aan die sterk winde en dwarsvloei wat deur die binneste waaiers geïnduseer
word. Verwronge inlaat lugvloei veroorsaak gevolglik variërende waaierlem en
ratkas belastingstoestande.
Die doel van hierdie ondersoek was om terselfdetyd die inlaat lugvloei asook waaierlem
en ratkas belastingstoestande van ’n enkele waaier wat op die rand van ’n grootskaalse
lugverkoelde stoomkondensor geleë is, te meet. Waaier inlaat en warmteruiler
uitlaat lugvloei snelhede is gemeet met ’n kombinasie van ultrasoniese- en skroefwindsnelheidsmeters
terwyl die lem en ratkas belastings gemeet is met rekstrokies.
Metings is oor ’n tydperk van 8 dae geneem. Die bevindinge toon dat ’n toename
in windsnelheid ’n toename in aksiale lugvloei tempo, deur die waaier veroorsaak. ’n
Afname in die gemiddelde lembelasting is waargeneem as gevolg van ’n afname in die
waaier statiese druk. Daar is ontdek dat die waaierlem teen ’n natuurlike frekwensie van
6 Hz vibreer wanneer dit opgewek word deur die wisselende aerodinamiese belasting.
Die aerodinamiese belasting is verkry uit die gemete data en vergelyk goed met die numeriese
werk van Bredell et al. (2006a). Daar is ook bevind dat waaier-as buigspannings
en wringkragte ossileer teen die waaier se rotasiefrekwensie van 2Hz met ’n groot wringkrag
wat op die as uitgeoefen word wanneer die waaier aangeskakel word.
iii
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Perimeter fan performance in forced draught air-cooled steam condensersVan der Spuy, Sybrand Johannes 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Axial flow fan arrays form part of air-cooled steam condensers in direct drycooled
power plants. This dissertation investigates the performance of axial flow
fans when located at the perimeter of a fan array. The perimeter (or edge) fans
may experience a reduction in air flow through the fan due to the prevalence of
distorted inlet conditions upstream of the fan. The reduction in air flow leads to a
reduction in the heat transfer capability of the steam condenser and a consequent
reduction in the electricity output of the power plant.
Due to the physical size of an air-cooled condenser, full-scale experiments are
often impractical and computational fluid dynamics (CFD) is used to model its
performance under various conditions. To limit the size of the CFD model the
axial flow fans in the CFD analysis are represented by means of simplified
methods. Three different simplified methods are presented and applied to a CFD
model of a single axial flow fan, namely the pressure jump method (PJM),
actuator disc method (ADM) and extended actuator disc method (EADM). The
results are compared to experimental values. The comparison highlights the
limitations of the models: The ADM fails to model fan performance correctly at
low flow rates, while the PJM ignores the variation in fan blade properties at
different locations within the fan rotor. The EADM is presented as an
improvement on both the other two models.
A multiple fan test facility is constructed, consisting of three 630 mm diameter
fans extracting air from a common inlet chamber. The inlet chamber is
constructed in such a way that one of the three fans act as the perimeter (edge)
fan. The floor of the inlet chamber can be adjusted to increase or reduce the inlet
flow distortion experienced by the edge fan. Six different fan configurations are
tested in the position of the edge fan and an empirical method is derived by which
the volumetric effectiveness of an edge fan can be predicted. The experimental
results are compared to CFD results for the same facility using the three different
simplified simulation methods investigated previously. Particle image velocimetry
(PIV) measurements are also performed upstream of the edge fan and the velocity
profiles at the inlet of the fan are compared to the profiles obtained numerically.
The comparisons show that the EADM predicts the performance of the edge fan
more accurately than the ADM en PJM.
The effect of adding a walkway and removing the bell mouth upstream of the
edge fan was investigated using the EADM. The results are used to show the
location of the loss mechanisms upstream of the edge fan. The addition of a
walkway moves the location of the pressure loss away from the edge fan bell
mouth towards the edge of the walkway. Consequently the distortion directly
upstream of the edge fan is reduced and its volumetric effectiveness increased.
The effect of removing the edge fan’s bell mouth is similar to the effect of adding
a walkway upstream of the edge fan. / AFRIKAANSE OPSOMMING: Aksiaalwaaiermatrikse vorm deel van lugverkoelde kondensors in direk droëverkoelde
kragstasies. Hierdie verhandeling ondersoek die werkverrigting van
aksiaalwaaiers wat geleë is op die rand van ‘n groot waaiermatriks. Die
randwaaiers kan ’n vermindering in deurvloei ondervind as gevolg van versteurde
inlaattoestande stroom-op vanaf die waaier. Die vermindering in lugvloei lei tot ’n
vermindering in die warmetoordagvermoë van die stoomkondensor en ’n
gepaardgaande afname in die elektrisiteitslewering van die kragstasie.
As gevolg van die fisiese grootte van die lugverkoelde kondensor is volskaalse
eksperimente gewoonlik onprakties en word berekeningsvloeimeganika (BVM)
gebruik om die werking van die aanleg onder verskeie toestande te modelleer. Ten
einde die grootte van die BVM model te beperk, word die aksiaalwaaiers in so ‘n
BVM analiese voorgestel met behulp van vereenvoudigde metodes. Drie
verskillende vereenvoudigde metodes word aangebied en toegepas op ‘n BVM
model van ‘n enkelwaaier, naamlik die druksprongmetode, die aksieskyfmetode
en die verlengde aksieskyfmetode. Die resultate word vergelyk met
eksperimentele waardes. Die vergelyking benadruk die beperkings van die
modelle: Die aksieskyfmetode kan nie die werking van die waaier akkuraat
voorspel by lae vloeie nie en die druksprongmetode ignoreer die variasie in
lemeienskappe op verskillende liggings binne-in die waaierrotor. Die verlengde
aksieskyfmetode word voorgestel as ‘n verbetering op die ander twee metodes.
‘n Veelvuldige waaiertoetsfasiliteit is saamgestel, bestaande uit drie 630 mm
deursnee waaiers wat lug uit ’n gemeenskaplike inlaatkamer suig. Die inlaatkamer
is so saamgestel dat een van die waaiers in die fasiliteit ‘n randwaaier
verteenwoordig. Die vloerhoogte van die inlaatkamer kan aangepas word om die
inlaatversteuring wat deur die raandwaaier ondervind word te vermeerder of te
verminder. Ses verskillende waaierkonfigurasies is getoets in die
randwaaierposisie. ‘n Empiriese metode waarmee die volumetriese effektiwiteit
van ‘n randwaaier voorspel kan word is afgelei. Die eksperimentele resultate word
vergelyk met ooreenstemmende BVM resultate vir dieselfde fasiliteit deur gebruik
te maak van die drie verskillende vereenvoudigde metodes wat vroeër ondersoek
is. Partikelbeeld snelheidsmetings word ook stroom-op vanaf die randwaaier
uitgevoer en die snelheidsprofiele by die inlaat van die waaier word vergelyk met
profiele wat numeries bereken word. Die vergelykings wys dat die verlengde
aksieskyfmetode die werkverrigting van ’n aksiaalwaaier meer akkuraat voorspel
as die aksieskyf- of druksprongmetodes.
Die effek van die installering van ‘n loopvlak en die verwydering van die
randwaaier se inlaatmondstuk word ondersoek met behulp van BVM deur gebruik
te maak van die verlengde aksieskyfmetode. Die resultate word spesifiek gebruik
om die ligging van die verliesmeganismes stroom-op vanaf die randwaaier aan te
dui. Die resultate wys dat die installering van ‘n loopvlak die ligging van die
drukverlies wegneem vanaf die rand van die waaierinlaat na die rand van die
loopvlak. Dit verminder die inlaatversteuring stroom-op vanaf die randwaaier en die volumetriese effektiwiteit word verhoog. Die verwydering van die randwaaier
se inlaatmondstuk het ‘n soortgelyke effek as die installering van ‘n loopvlak
stroom-op vanaf die randwaaier.
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Development of a Neutron Flux Monitoring System for Sodium-cooled Fast ReactorsVerma, Vasudha January 2017 (has links)
Safety and reliability are one of the key objectives for future Generation IV nuclear energy systems. The neutron flux monitoring system forms an integral part of the safety design of a nuclear reactor and must be able to detect any irregularities during all states of reactor operation. The work in this thesis mainly concerns the detection of in-core perturbations arising from unwanted movements of control rods with in-vessel neutron detectors in a sodium-cooled fast reactor. Feasibility study of self-powered neutron detectors (SPNDs) with platinum emitters as in-core power profile monitors for SFRs at full power is performed. The study shows that an SPND with a platinum emitter generates a prompt current signal induced by neutrons and gammas of the order of 600 nA/m, which is large enough to be measurable. Therefore, it is possible for the SPND to follow local power fluctuations at full power operation. Ex-core and in-core detector locations are investigated with two types of detectors, fission chambers and self-powered neutron detectors (SPNDs) respectively, to study the possibility of detection of the spatial changes in the power profile during two different transient conditions, i.e. inadvertent withdrawal of control rods (IRW) and one stuck rod during reactor shutdown (OSR). It is shown that it is possible to detect the two simulated transients with this set of ex-core and in-core detectors before any melting of the fuel takes place. The detector signal can tolerate a noise level up to 5% during an IRW and up to 1% during an OSR.
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