Error Sources Considered in the "UMAE Driven" CIAU Methodology
NURETH-14 - 2011 September 25-30

Presented at:
2011 September 25-30
Toronto, Canada
Session Title:
O4-2 BEPU (Best Estimate code Plus Uncertainty) method, CSAU, Statistical Methods

Andriy Kovtonyuk (GRNSPG, Università di Pisa)
Alessandro Petruzzi (GRNSPG, Università di Pisa)
Francesco S. D'Auria (University of Pisa, GRNSPG, Italy)


Uncertainty analysis aims at characterizing the errors associated with experimental data and with results of computer codes when applied to the predictions of nuclear power plants related scenarios, in contradistinction with sensitivity analysis, which aims at determining the ‘amount of change’ in the predictions of codes when one or more input parameters varies within proper ranges of interest.

An outline of the features of independent approaches for estimating the uncertainty associated with predictions of system thermal-hydraulic codes is provided. The approach, according to which the uncertainty derives from the comparison between relevant measured data and results of corresponding code calculations, is discussed in details.

Within the framework of this approach, the UMAE (Uncertainty Method based on the Accuracy Extrapolation) method has been developed first and, later on, used as virtual engine for the method named Code with capability of Internal Assessment of Uncertainty (CIAU). The principle of UMAE is the consideration of the measure of accuracy as a statistical quantity independent of the scale. On this basis the value of accuracy measured at different scales is also valid at the scale of the Nuclear Power Plant and constitutes the uncertainty.

Individual Conference-Paper Copies (Electronic Where Available):

  • For CNS members, the first 5 copies per calendar year are free, and additional copies are $10 each.
  • For non-members, the price is $25 for the first Conference-paper copy in a request, and $10 each for additional copies of papers in the same conference and in the same request.
  • Contact the CNS office to order reprints.