dc.contributor |
Kungl. Tekniska högskolan. Kärnkraftssäkerhet |
dc.contributor |
Dinh, Truc-Nam |
dc.contributor.author |
Abal López, Javier |
dc.date |
2006 |
dc.identifier.uri |
http://hdl.handle.net/2099.1/26201 |
dc.language.iso |
eng |
dc.publisher |
Universitat Politècnica de Catalunya |
dc.publisher |
Kungliga Tekniska Högskolan |
dc.rights |
Attribution-NonCommercial-NoDerivs 3.0 Spain |
dc.rights |
info:eu-repo/semantics/openAccess |
dc.rights |
http://creativecommons.org/licenses/by-nc-nd/3.0/es/ |
dc.subject |
Àrees temàtiques de la UPC::Energies::Energia nuclear::Centrals nuclears |
dc.subject |
Àrees temàtiques de la UPC::Matemàtiques i estadística::Probabilitat |
dc.subject |
Boiling water reactors -- Safety measures |
dc.subject |
Risk assessment -- Statistical methods |
dc.subject |
Boiling water reactors -- Risk assessment |
dc.subject |
Reactors nuclears d'aigua bullent -- Mesures de seguretat |
dc.subject |
Reactors nuclears d'aigua bullent -- Gestió del risc |
dc.subject |
Gestió del risc -- Mètodes estadístics |
dc.title |
A Deterministic/probalistic analysis of Ex-Vessel melt risk in a BWR |
dc.type |
info:eu-repo/semantics/masterThesis |
dc.description.abstract |
The present study is concerned with deterministic and probabilistic analysis of ex-vessel
melt risks in a Swedish designed BWR plant. The focus is placed on a station blackout
(SBO) scenario, with immediate SCRAM and subsequent activation of the main steam
valve isolation (at 52 s). Four sequences were examined in detail to study the effect of
two valves systems related to the operation of ADS (Automatic Depressurization
System), and cavity flooding by water from suppression pool. The later action
constitutes a cornerstone in the SAM (Severe Accident Management) strategy adopted
in the newer Swedish and Finnish BWR plants.
On the deterministic side, the US NRC MELCOR code was used to simulate the BWR
system behaviours and phenomena that govern threats to the containment integrity.
Remarkably, time factor (such as delays in instrumentation activation) was found to be
of paramount importance to the sequence’s dynamics and consequences. On the
probabilistic side, a review of methods in Level 2 Probabilistic Risk Analysis (PRA)
based on classical concepts of event trees-fault trees reveals that the existing methods
ignore the time dependence, suggesting the need and potential value to explore a
dynamic approach. In the present work, a recently-developed concept of dynamic fault
trees was adopted. Specifically, dynamic structures were built into the tree’s branching
points to enable capturing the effect of time-competing events in Level 2 PRA (severe
accidents). The technique was successfully implemented in Matlab\Simulink. The
method was then applied to four cases to compute the probability of occurrence of
various key events.
For the four cases studied, MELCOR results show the time for cavity rupture due to
debris ablation varied between the 17.5 h and the 30.5 h. They also show direct
containment heating (DCH) when ADS fails to operate. Interestingly, the probabilistic
results exhibit associative and competitive behaviours in the two valve systems,
confirming the need to account for their interdependence. |
dc.description.abstract |
Outgoing |