Page 113 - Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

86 Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

Cladding temperature distribution and hot spots
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Pressure drop
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Fluid structure interaction
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Flow-induced vibrations
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Grid-to-rod fretting
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l Fuel assembly bow
3.2.1.3 Integral tests
Integral test data are, in principle, applicable to full-scale nuclear plant conditions
(Martelli et al., 2015). Nevertheless, the data can be extrapolated to full scale, if
the test facilities and the initial and boundary conditions of experiments are properly
scaled, that is, the scaling will not affect the evolution of physical processes important
for the postulated accident scenario. This evaluation determines whether the data may
be used in nuclear plant safety analyses.
On the other side, integral tests are fundamental for supporting the development
and demonstrating the reliability of computer codes in simulating the behavior of a
nuclear power plant, during a postulated accident scenario: in general, this is a regu-
latory requirement. Applications of computer codes to accident analyses require the
implicit assumptions that these codes have the capabilities to scale up phenomena and
processes from test facilities to full-scale plant conditions. However, the different
scale, in terms of geometry, characterizing any facility and a nuclear plant, does
not ensure a priori that a code, which is able to reproduce a generic transient in a scaled
facility, is also able to calculate with the same accuracy the same transient in a nuclear
power plant.
These considerations imply that integral tests are unavoidable and complex activ-
ities, which involve the following objective and areas of investigations:

l Phenomena and processes of interest at system level and connected with design, safety, and
operation issues
l Simulations and analyses of a broad spectrum of accident scenarios
l Accident management procedures
l Component testing
l Scaling issue
l Generating databases for supporting licensing process
l Code assessment and validation

3.2.2 HLM large pool design

In the following, the conceptualization of a large test pool facility is described, con-
sidering in the design phase the aim to support the development of a lead fast reactor,
according at least part of the open issues mentioned earlier.
The conceptual design is based on the following constraints:
No mechanical pump is adopted for the coolant flowing, while gas-enhanced circulation is
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adopted to promote circulation.