The probability of containment failure by direct containment heating in Zion

Abstract

This report is the first step in the resolution of the Direct Containment Heating (DCH) issue for the Zion Nuclear Power Plant using the Risk Oriented Accident Analysis Methodology (ROAAM). This report includes the definition of a probabilistic framework that decomposes the DCH problem into three probability density functions that reflect the most uncertain initial conditions (UO, mass, zirconium oxidation fraction, and steel mass). Uncertainties in the initial

In-vessel retention coolability evaluation for Chinese improved 1000 MWe PWR

“…ROAAM approach is developed in 90's for evaluating the probability of containment failure (Pilch et al, 1994). Overall procedure of IVR evaluation is shown in Fig.…”

Issues on containment integrity during severe accidents

“…For higher heating rates (typically above 0.3-0.5 Kls), the oxide layer build up is slow causing zircaloy melting and relocation to lower core region while lower heating rates prevent zircaloy relocation and causes complete oxidation in-place [1]. Zircaloy oxidation also controls total amount of hydrogen release in the vessel with little contribution of core structures and U02 because of early melting of the structures and steam exposure of U02 limiting its oxidation [7,10,11].…”

“…Severity of consequences depends largely on the melt release states from RPY. Major processes constituting various ex-vessel phenomena are containment thermohydraulics, fission products transport, and melt dispersion [1,[7][8][9][10][11][12][13][14][15][16][17][20][21][22].…”

“…Other heat sources include combustion of hydrogen and carbon monoxide, and radioactive heating due to corium spread in the cavity. Heat sinks include all structural surfaces, leakages and deliberate releases from the containment volume [1,5,7,[10][11][12]14].…”

“…Variability in structural modeling/analysis is also to be accounted. Air leakage A. In-Vessel Phenomena In-vessel phenomena for PWR can be described under general topics of thermohydraulics, oxidation of core materials, core relocation and failure of reactor pressure vessel (RPV) [7][8][9][10][11].…”