Nuclear Energy for New Europe 2009

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No: 303

Conference: Nuclear Energy for New Europe 2009

Title: Uncertainties and Risk-Informed Decision Making

Theme: Probabilistic Safety Assessment

Author(s): Andrija Volkanovski, Marko Čepin

Contact : Andrija Volkanovski

E-mail: andrija.volkanovski@ijs.si

Address: Institut "Jožef Stefan" R4
1001 Ljubljana

Country: Slovenia

The U.S. Nuclear Regulatory Commission encourages use of the probabilistic safety assessment to improve safety decision making and improve regulatory efficiency. The Regulatory Guide 1.174 defines acceptance guidelines for nuclear plants risk measures and their corresponding change resulting from the licensee initiated modifications. The risk measures used in the acceptance guidelines are the core damage frequency and large early release frequency.
The appropriate consideration of the uncertainties associated with the probabilistic safety assessment and their impact on results is necessary in order to address them in the context of the decisionmaking. The different types of epistemic uncertainty are parameter, model, and completeness uncertainties.
The uncertainty analysis on the reference model of the nuclear power plant is done. The core damage frequency for operating at-power light water reactor considering internal events is assessed. The analysed modification is extension of the test interval of the emergency diesel generators. The analysis is done with variation of the loss of offsite power initiating event frequency, truncation limits and minimal cut sets quantification approximations. The results from the uncertainty analysis are compared with the established acceptance criteria.
The obtained results show the necessity of appropriate consideration of the uncertainties in the probabilistic safety assessment in order to adequately support the risk-informed decision making.

No:	303
Conference:	Nuclear Energy for New Europe 2009
Title:	Uncertainties and Risk-Informed Decision Making
Theme:	Probabilistic Safety Assessment
Author(s):	Andrija Volkanovski, Marko Čepin
Contact :	Andrija Volkanovski
E-mail:	andrija.volkanovski@ijs.si
Address:	Institut "Jožef Stefan" R4 1001 Ljubljana
Country:	Slovenia

The U.S. Nuclear Regulatory Commission encourages use of the probabilistic safety assessment to improve safety decision making and improve regulatory efficiency. The Regulatory Guide 1.174 defines acceptance guidelines for nuclear plants risk measures and their corresponding change resulting from the licensee initiated modifications. The risk measures used in the acceptance guidelines are the core damage frequency and large early release frequency. The appropriate consideration of the uncertainties associated with the probabilistic safety assessment and their impact on results is necessary in order to address them in the context of the decisionmaking. The different types of epistemic uncertainty are parameter, model, and completeness uncertainties. The uncertainty analysis on the reference model of the nuclear power plant is done. The core damage frequency for operating at-power light water reactor considering internal events is assessed. The analysed modification is extension of the test interval of the emergency diesel generators. The analysis is done with variation of the loss of offsite power initiating event frequency, truncation limits and minimal cut sets quantification approximations. The results from the uncertainty analysis are compared with the established acceptance criteria. The obtained results show the necessity of appropriate consideration of the uncertainties in the probabilistic safety assessment in order to adequately support the risk-informed decision making.