The role of nuclear thermal-hydraulics in the licensing of Atucha-II: the LBLOCA
| Autor: | Oscar Mazzantini, G. M. Galassi, Francesco Saverio D'Auria |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Pressurized heavy-water reactor
Nuclear and High Energy Physics Channel type reactor 020209 energy Nuclear engineering Atucha-II PHWR Channel type reactor Positive void coefficient LBLOCA BEPU approach licensing in nuclear technology Thermal power station 02 engineering and technology 01 natural sciences Void coefficient 010305 fluids & plasmas law.invention Thermal hydraulics law Neutron flux Positive void coefficient 0103 physical sciences 0202 electrical engineering electronic engineering information engineering General Materials Science licensing in nuclear technology Safety Risk Reliability and Quality Waste Management and Disposal BEPU approach Mechanical Engineering Pressurized water reactor LBLOCA Coolant Nuclear Energy and Engineering Atucha-II PHWR Environmental science Loss-of-coolant accident |
| Popis: | The paper deals with the safety evaluation and the embedded licensing process of the Atucha-II 800 Mwe Pressurized Heavy Water Reactor (PHWR) in Argentina. Atucha-II was designed by Kraftwerk Union (KWU) during the 60’s, the related construction was started/stopped in the 90’s and restarted on 2006, and was connected to the electrical grid in 2014. Because of market policies, the KWU designer could not be directly involved in the licensing process during the first decade of the 2000 millennium: a licensing suited safety evaluation was performed by the Nucleoelectrica Argentina (NA-SA), utility owner of the Atucha-II, with support of external experts group. A designer-independent assessment was performed having access to the installed systems and components other than the relevant design documents. Large core size (related to Pressurized Water Reactor – PWR – producing the same thermal power), presence in the core of natural uranium and heavy water fluids, i.e. the coolant and the moderator driven by two circulation loops with different average temperatures, characterize the system design. In those conditions, during the early phase of a depressurization transient, the ‘hot’ coolant vaporizes and the colder moderator remains in the liquid phase: a positive void coefficient is created. The relevance of the Large Break Loss of Coolant Accident (LBLOCA) in safety assessment is discussed with emphasis given to the system design features, the approach pursued in the analysis and the key results. Break opening time and time of occurrence of the safety boron injection affect, during the early period of the transient, the propagation of (negative) pressure wave, the fluid flashing, the heat transfer and the neutron flux: a fission power excursion is expected to occur. The analysis of a complex three-dimensional situation, considering the unavoidable uncertainties associated with the computation, demonstrates that safety limits are preserved. |
| Databáze: | OpenAIRE |
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