Nenad Debrecin

Outline of the Uncertainty Methodology Based on Accuracy Extrapolation

AbstractUncertainty methodology based on accuracy extrapolation (UMAE) is outlined. This methodology is suitable for evaluating the uncertainty in the prediction of transient scenarios in nuclear reactors when carried out by thermal-hydraulic system codes. It is based on the extrapolation of the accuracy resulting from a comparison between code results and relevant experimental data obtained in small scale facilities. A simplified diagram of the UMAE is compared with a similar one derived for the code scaling, applicability and uncertainty evaluation (CSAU) previously proposed by the U.S. Nuclear Regulatory Commission. A few results related to the full application of the UMAE to a small-break loss-of-coolant accident in a pressurized water reactor, including core uncovery, are also reported.

Application of Relap5/Mod3 to the evaluation of loss of feedwater in test facilities and in nuclear plants

Abstract The present paper deals with the evaluation of the capabilities of the Relap5/Mod3 code (7J version) in simulating the phenomena occurring following the application of an accident management procedure in the case of a loss of feedwater transient in PWR type nuclear plants; the actuation of high pressure injection system is not foreseen in the primary side. The proposed procedure is based upon the intervention of auxiliary feedwater after the occurrence of dryout in the core region. This is a consequence of primary inventory loss from the pressurizer relief valve. Two experiments performed in Lobi and Spes facilities are the reference data base for the activity. Post-test analyses were performed by using the above code to evaluate the differences with respect to Relap5/Mod2 code results as well. Nuclear plant performance was predicted with reference to the same plant scenario.

Analysis of power plants competitiveness using stochastic methods

The paper describes the application of a stochastic method for comparing economic parameters of future electrical power generating systems including conventional and nuclear power plants. The input data for calculation are cost elements defined in the frame of certain limits of expected occurrence with a probability distribution within the limits. The method is applied to establish competitive specific investment costs of future nuclear power plants when compared with combined cycle gas fired units combined with wind electricity generators using best estimated and optimistic input data.

External costs: an attempt to make power generation a fair game (case study Croatia)

External costs of electricity represent the monetary value of the environmental damage caused by electricity generation. They are here calculated applying the impact pathway methodology on Croatian specific conditions. This paper estimates the external costs of coal and gas fired power plants determined as main candidates for Croatian power system expansion till 2030. It is analyzed how the estimated external costs, when incorporated into total production costs, would affect the competitiveness of fossil–fired plants compared to other electricity generation options, i.e. how they influence the optimal expansion strategy of the Croatian power system.