Reliability Methods for Passive Safety Functions

Abstract

This paper presents the study performed within the framework of a European Project called Reliability Methods for Passive Safety Functions (RMPS). Its objective is to propose a specific methodology to assess the passive system thermal-hydraulic (T-H) reliability. The methodology is tested on an example of industrial passive system: the Isolation Condenser System (ICS). The T-H calculations are performed using the RELAP5, ATHLET and CATHARE computer codes. In this paper, the present state of the methodology and its application to the example are described. Owing to the recent start of the project, only results concerning the first objective of the project (identification and quantification of the sources of uncertainties and determination of the important variables) are presented. A sensitivity analysis was carried out on 69 computation results performed with the RELAP5 code. This first analysis highlights the significant parameters influencing the performances of the ICS and shows a non-monotonous behavior of the system.

Application of REPAS Methodology to Assess the Reliability of Passive Safety Systems

“…It was the result of a joint cooperation between ENEA, UNIPI, and Polytechnic of Milan. Then this methodology was embedded in the RMPS EU project on the framework of the 5th EURATOM program [19], see also [3,4,16,17] and so forth, In this report is shown an improvement REPAS method is described and three applications related to a pool heat removal system of a prototypical integrated system, a scaled IC of an SBWR and TTL 1 experimental apparatus, were presented.…”

“…(1) The "figure of merit" approach proposed by [2]: the result is given in Figure 24. (2) The "cumulative probability" approach suggested by [16]: the result is given in Figure 25, where a comparison is made with the result from a previous REPAS application case b. (3) The R1 single-valued reliability definition is…”

Evaluation of uncertainties related to passive systems performance

“…The reliability methods for passive safety functions (RMPS) project, carried on within the fifth European Community Framework Programme (2001)(2002)(2003)(2004), must address the following tasks (Marques et al, 2002):…”