In the last four decades, large eﬀorts have been undertaken to provide reliable thermal-hydraulic system codes for the analyses of transients and accidents in nuclear power plants. Whereas the ﬁrst system codes, developed at the beginning of the 1970s, utilized the homogenous equilibrium model with three balance equations to describe the two-phase ﬂow, nowadays the more advanced system codes are based on the so-called “two-ﬂuid model” with separation of the water and vapor phases, resulting in systems with at least six balance equations. The wide experimental campaign, constituted by the integral and separate eﬀect tests, conducted under the umbrella of the OECD/CSNI was at the basis of the development and validation of the thermal-hydraulic system codes by which they have reached the present high degree of maturity. However, notwithstanding the huge amounts of ﬁnancial and human resources invested, the results predicted by the code are still aﬀected by errors whose origins can be attributed to several reasons as model deﬁciencies, approximations in the numerical solution, nodalization eﬀects, and imperfect knowledge of boundary and initial conditions. In this context, the existence of qualiﬁed procedures for a consistent application of qualiﬁed thermal-hydraulic system code is necessary and implies the drawing up of speciﬁc criteria through which the code-user, the nodalization, and ﬁnally the transient results are qualiﬁed.
|Autori:||PETRUZZI A.; D'AURIA F.|
|Titolo:||Thermal-Hydraulic System Codes in Nulcear Reactor Safety and Qualification Procedures|
|Anno del prodotto:||2008|
|Appare nelle tipologie:||1.1 Articolo in rivista|