A safety analysis for the McMaster Nuclear Reactor has been carried out for
postulated scenarios of loss or termination of forced flow in the reactor core in a
state of shutdown, with loss of pool inventory of different magnitudes including core
uncovery. Models were developed to evaluate the natural convection flow through the
core assemblies for the different conditions within the aforementioned envelope. The
flow rate was used to get the temperature or enthalpy rise along the heated channel in
order to estimate the corresponding clad temperatures in the given scenarios.
The models were constructed from first principles using the one-dimensional momentum conservation law, incorporating the Boussinesq approximation for the single-phase
case and the Homogeneous Equilibrium Model assumptions when a two-phase mixture
was present. In order to obtain the flow rate and enthalpy rise along the channel,
knowledge of the assembly power and inlet temperature is required. The power was
calculated using a well known decay power correlation. The pool temperature which
was used as the assembly inlet temperature was calculated via a lumped parameter
model using a simple energy balance between the core output (again by using the
decay-heat profile) and the pool heatup. Heat losses from the pool were neglected and
the model allowed for reaching saturation temperature in the pool. In this case, water
vaporization was calculated using the latent heat to assess pool inventory loss rate.
For all scenarios before core uncovery, the models predict that clad and fuel
temperatures remained well below limits associated with clad blistering or melting.
Consequently, it is asserted natural convection and acceptable temperatures will be
sustained in the McMaster Nuclear Reactor while the core remains covered. In the
most severe draining before uncovery, in which the pool drains to just before exposing
the core, it takes approximately a week (180 hours) after shutdown for boiling to start
in the core’s hottest channel. For core uncovery, the models predict that the clad
remains below the blistering temperature for pool height at 9.4% of the heated channel’s
height (corresponding to exposing about 61.7 cm of the assembly), and below melting
temperature for pool height at 8.1% of the heated channel’s height (corresponding to
exposing about 62.5 cm of the assembly). Both heights are below the height of the
bottom of the lowest beam tube, at which the worst draining case will end. / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/17196 |
| Date | January 2015 |
| Creators | Schneider, Alexander Shlomo |
| Contributors | Luxat, John, Engineering Physics |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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