Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Regulators and designers of nuclear reactors regard knowledge of the pebble fuel
temperature as important, due to the role that it plays in maintaining structural
integrity and the production of neutrons. By using special fuel assemblies fitted
with measuring equipment it is possible to measure the fuel temperature in
stationary fuel reactors. This, however, is not possible in the pebble bed modular
reactor due to its dynamic core. Designers of the pebble bed modular reactor
have reserved special inspection channel borings inside the center reflector for
fuel temperature measurement. By means of optical fibers and interferometry,
the temperature can be measured inside such a channel. Currently the only way
to control the fuel surface and core temperature is by measuring the gas inlet
and outlet temperatures.
This thesis attempts to determine the pebble temperature by measuring the
temperature in a reflector channel. This is done by constructing an electrically
heated pebble bed experimental setup simulating a cutout section of a pebble
bed modular reactor core. An additional computational fluid dynamics simulation
of the experimental setup was also performed. This thesis also attempts to
determine if there is a measureable temperature peak that can indicate where a
pebble was in contact with the reflector surface. This could then be used in
future studies to determine the pebble fuel velocity as it moves down the reactor
core.
The computational fluid dynamics results were validated by experimental
measurements. In the computational fluid dynamics model and experimental
setup, it was found that there was indeed a measureable temperature difference
on the temperature gradient along the reflector wall. The heat being conducted
away from the pebble through the contact area can explain this. These
differences were only observed when the channel was moved closer to the pebbles and it is therefore advised that some redesigning of the channel should
be done if the in-core temperature is to be accurately interpreted by the
designers at PBMR (Pty) Ltd. / AFRIKAANSE OPSOMMING: Reguleerders en ontwerpers van kern reaktore beskou die kennis van die korrel
brandstof temperatuur as belangrik. Dit is weens die rol wat die brandstof
temperatuur speel met die behoud van strukturele integriteit en die produksie
van neutrone binne-in die reaktor. Met behulp van spesiale brandstof montasies
toegerus met die meetings instrumentasie, is dit moontlik om die brandstof
temperatuur in stilstaande brandstof reaktore te meet. Dit is egter nie moontlik
in die korrel bed modulêre reaktor nie, as gevolg van sy dinamiese kern.
Ontwerpers van die korrel bed modulêre reaktor het spesiale kanale in die
binnekant van die middel reflektor vir brandstof temperatuur meeting
gereseveer. Deur middel van optiese vesel en interferometrie, kan die
temperatuur binne so 'n kanaal gemeet word. Tans is die enigste manier om die
brandstof-oppervlak temperatuur te berekern, net moontlik deur gebruik te
maak van die gemete gas inlaat-en uitlaat temperature van die reaktor.
Hierdie tesis poog om vas te stel of die korrel brandstof temperatuur deur die
meet van die oppervlak temperatuur in 'n reflektor-kanaal bepaal kan word. Dit
word gedoen deur 'n elektriese verhitte korrel bed eksperimentele opstelling te
bou wat 'n gedeelte van 'n korrel bed modulêre reaktor simuleer. 'n Bykomende
numeriese simulasie van die eksperimentele opstelling was ook uitgevoer.
Hierdie werk het ook probeer om vas te stel of daar 'n meetbare temperatuur
piek op die temperatuur profiel aandui kan word waar 'n korrel in kontak is met
die reflektor se oppervlak. Dit kan dan in toekomstige studies gebruik word om
te bepaal wat die korrel brandstof spoed was soos dit in die reaktor beweeg.
Die numerise simulasie uitslae was deur eksperimentele metings bevestig. In die
numerise simulasie model en die eksperimentele opstelling, is daar gevind dat
daar inderdaad 'n meetbare temperatuur verskil op die temperatuurgradiënt
teen die reflektor oppervlak is. Dit kan verduidelik word as gevolg van die hitte wat weg van die korrel gelei word deur middel van die kontak area. Hierdie
verskille was slegs waargeneem wanneer die kanaal nader aan die korrels geskuif
is en dit word as n aanbeveling aan PBMR (Pty) Ltd gemaak om sommige
herontwerpe aan die kanaal te doen indien die in-kerntemperatuur gemeet wil
word en akkuraat geinterpreteer wil word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4145 |
| Date | 03 1900 |
| Creators | Oswald, Elbrecht |
| Contributors | Dobson, R. T., University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 99 p. : ill. |
| Rights | University of Stellenbosch |
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