Abstract
The SCANAIR code due to French research organisation IRSN (Institut de Radioprotection et de Sûreté Nucléaire) has been developed to model the mechanics, thermal hydraulics and fission gas behaviour of a single fuel rod during the reactivity initiated accident (RIA). For the last few years, an outdated version of the code, SCANAIR V4 (V4beta to be exact), has been in use and under development at VTT. The new version of SCANAIR, V6, was made available to VTT in spring 2009. There are two major improvement areas in the new SCANAIR version compared to the previously used version. Firstly, the thermal hydraulics modelling has been improved substantially. The second major development is the introduction of a module that calculates the rod failure mechanics.
This module named CLARIS is a post-processing tool that utilizes the SCANAIR results in the prediction of rod failure probability in RIA.
The introduction of the code at VTT and the evaluation of the new and improved models of the code were done within this thesis. In practice this was executed by calculating a set of selected validation tasks. At first however, the relevant RIA related issues and the models in SCANAIR are presented in the thesis to have a basic understanding of the research field and the code. As a first application, a hypothetical boron dilution accident in a VVER type reactor was calculated to test the thermal hydraulic model of the code in pressurized water reactor (PWR) conditions. The second validation task considered the evaluation of the CLARIS module by calculating an RIA test named LS-1. The third task was to instigate the evaluation of the SCANAIR calculation uncertainties that are induced by the steady-state initialization of the calculation.
The initialization is conducted by using a separate steady-state code. The new SCANAIR code version with the new models was stated to perform as expected.
The convergence problems afflicting the PWR conditions with the previously used code version were absent. The fracture mechanical approach of CLARIS was found to have sources of uncertainties that make the failure evaluation somewhat inexact. Of all the initialization data, the initialization of the fission gases was concluded to have the most profound effect on SCANAIR results.
The goals set for this thesis were met with the calculated validation tasks, and improvement areas within the modelling were distinguished. With the validation work reported in this thesis, the obligations of the in-kind work specified in the SCANAIR software licence agreement for the year 2009 have been fulfilled.
This module named CLARIS is a post-processing tool that utilizes the SCANAIR results in the prediction of rod failure probability in RIA.
The introduction of the code at VTT and the evaluation of the new and improved models of the code were done within this thesis. In practice this was executed by calculating a set of selected validation tasks. At first however, the relevant RIA related issues and the models in SCANAIR are presented in the thesis to have a basic understanding of the research field and the code. As a first application, a hypothetical boron dilution accident in a VVER type reactor was calculated to test the thermal hydraulic model of the code in pressurized water reactor (PWR) conditions. The second validation task considered the evaluation of the CLARIS module by calculating an RIA test named LS-1. The third task was to instigate the evaluation of the SCANAIR calculation uncertainties that are induced by the steady-state initialization of the calculation.
The initialization is conducted by using a separate steady-state code. The new SCANAIR code version with the new models was stated to perform as expected.
The convergence problems afflicting the PWR conditions with the previously used code version were absent. The fracture mechanical approach of CLARIS was found to have sources of uncertainties that make the failure evaluation somewhat inexact. Of all the initialization data, the initialization of the fission gases was concluded to have the most profound effect on SCANAIR results.
The goals set for this thesis were met with the calculated validation tasks, and improvement areas within the modelling were distinguished. With the validation work reported in this thesis, the obligations of the in-kind work specified in the SCANAIR software licence agreement for the year 2009 have been fulfilled.
| Original language | English |
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| Qualification | Master Degree |
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| Publication status | Published - 2010 |
| MoE publication type | G2 Master's thesis, polytechnic Master's thesis |