State-of-the-Art Reactor Consequence Analyses Project: Uncertainty Analyses for Station Blackout Scenarios

Perspectives on a Severe Accident Consequences—10 Years after the Fukushima Accident

“…Therefore, the accident progression and radiological releases were predicted with uncertainties. Recently, systematic approaches to handle these uncertainties in the phenomenological and physical modellings of a severe accident analysis have been developed [21,22], which enabled handling of the uncertainties in a rigorous statistical manner [23]. Typical uncertainty calculation included sensitivity studies on sequence related parameters such as primary safety valve stochastic number of cycles until failure-to-close, in-vessel accident progression related model parameters such as Zircaloy melt breakout temperature, molten clad drainage rate, and ex-vessel accident progression related model parameters such as hydrogen ignition criteria, chemical form of iodine, aerosol dynamics shape factor, containment convection heat transfer coefficient [21].…”

“…Using Monte-Carlo or Latin hypercube sampling methods, about 300-1000 calculations were performed for a typical scenario, such as station black out (SBO), whose accident progression is similar to that of Fukushima. Widespread radiological release was observed between calculated median, mean, and 95th percentile curves [21,22]. These analyses results are integrated with the MACCS (MELCOR Accident Consequence Code System) [24] analyses to predict latent cancer fatality (LCF) risk statistics.…”

The EC MUSA Project on Management and Uncertainty of Severe Accidents: Main Pillars and Status

“…Currently under way is the setting up of uncertainty cases that requires the implementation of the uncertainty sources defined in WP2, and the coupling of SA codes with UQ tools as covered in WP3. This step also draws on experiences made in WP4 and in earlier works such as [21].…”

Safety Analysis for Accident-Tolerant Fuels with Increased Enrichment and Extended Burnup

“…The hold-up by oxide shell model aims to capture the mechanical effect of the outer shell formed around the Zr cladding when oxidation occurs with steam. This oxide shell has a higher melting temperature than the underlying cladding and has been observed to maintain structural integrity even as the unoxidized cladding material inside the shell melts away [67]. MELCOR allows a ZrO2 shell to remain intact and able to support a melt up to 2400 K, after which a time-at-temperature failure mode was activated, and the cladding begins to fail.…”