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@PHDTHESIS{Beler:788529,
author = {Beßler, Yannick},
othercontributors = {Natour, Ghaleb and Singheiser, Lorenz},
title = {{S}trömungsmechanische {S}imulation und experimentelle
{V}alidierung des kryogenen {W}asserstoff-{M}oderators für
die {E}uropäische {S}pallationsneutronenquelle {ESS}},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2020-04622},
pages = {1 Online-Ressource (XXIV, 154, xxxiii Seiten) :
Illustrationen, Diagramme},
year = {2020},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, Rheinisch-Westfälische Technische
Hochschule Aachen, 2020},
abstract = {The European spallation neutron source ESS is currently
under construction and should start part-load operation in
2023. With an average proton beam power of 5 MW, it will
become the most powerful spallation neutron source
worldwide. A key component of a spallation neutron source is
the cold moderator. At the ESS, the cold moderator will be
operated with liquid parahydrogen at a temperature and
pressure around 20 K and 10 bar respectively and is intended
to slow down (moderate) the fast neutrons, released by the
spallation process, to the required low velocity level.
Latest particle-transport-simulations show that the neutron
yield can be increased by up to 30 $\%$ by optimizing the
existing cold moderator. The present dissertation therefore
examines the technical feasibility of this new moderator for
full-load operation of the European spallation neutron
source ESS. The primary goal is to verify whether the cold
moderator can be operated at full proton beam power or up to
which beam power a safe operation is possible. In addition,
the feasibility from the structural mechanical and
manufacturing point of view will be assessed. In order to
investigate the flow behavior in the cold moderator, a
numerical flow simulation was first carried out. The flow
guiding has been optimized for the best possible heat
transfer because the pulsed proton beam causes an enormous
fluctuation in thermal load. Furthermore, sources of errors
of the simulation were identified and minimized. For this
purpose, the model error of the flow simulation was
determined by particle image velocimetry (PIV) comparison
measurements. As part of the parameter studies, it turned
out that the cold moderator can only be safely operated up
to a proton beam power of approx. 3.4 MW under the given
requirements and with a conservative consideration of all
errors. Therefore, a several additional options were shown,
by which the proton beam power might be significantly
increased, and the goal of 5 MW would still be possible. The
structural mechanical part of this work, in which the cold
moderator was designed according to the nuclear code
RCC-MRx, showed that the pressure vessel withstands all
static and dynamic loads. Thereby the radiation as well as
all loads in normal and abnormal operation were considered.
Finally, an initial prototype of the optimized cold
moderator has been manufactured and tested. The joining
technology for the selected aluminum alloy AW 6061-T6 was of
special importance, since this alloy is generally difficult
to weld. Electron beam welding was used because it leads to
lowest possible distortions and minimized local heat input.
Finally, non-destructive tests were carried out to confirm
the high quality of the manufacturing, and thus the
suitability of the cold moderator for a safe operation under
the extreme operating conditions.},
cin = {417610},
ddc = {620},
cid = {$I:(DE-82)417610_20040731$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2020-04622},
url = {https://publications.rwth-aachen.de/record/788529},
}
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