Evaluation of Code accuracy in the prediction of OECD/CSNI ISP 22, OECD CSNI Final Workshop on ISP 22 - Pisa (I) July 2-4 1991

The results obtained in a more-than-a-decade application of thermal-hydraulic system codes to the analysis of experiments performed in Integral Test Facilities (ITF) and Separate Effect test Facilities (SETF) including the participation to several International Standard Problems (ISP) and Standard Problem Exercises (SPE), organized by OECD/NEA/CSNI (Organization for Economic Cooperation and Development / Nuclear Energy Agency / Committee on the Safety of Nuclear Installations) and by IAEA (international Atomic Energy Agency), respectively, suggested the need for new methods and procedures for code application. The words nodalization-qualification, qualitative-accuracy-evaluation, quantitative-accuracy-evaluation, and acceptability-thresholds were introduced. The present document deals with accuracy quantification at the transient level in relation to the ISP 22 performed in SPES facility. The FFTBM (Fast Fourier Transform Based method) developed at UNIPI was applied and a hierarchy of calculation quality by various participants was determined.