Erfahrungs- und Forschungsbericht 2012 - Ensi

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Erfahrungs- und Forschungsbericht 2012 - Ensi

PISA-II

Pressure Vessel Integrity and Safety Analysis

Author und Co-author(s) M. Niffenegger, G. Qian, V. Gonzalez, B. Niceno,

M. Andreani

Institution

Paul Scherrer Institut, Laboratory for Nuclear Materials

Address

5232 Villigen

Tel., E-mail, Internet address +41 56 310 26 86 Markus.Niffenegger@psi.ch, www.psi.ch

and http://lnm.web.psi.ch/ssi/lnm_projects_cs.html

Duration of project July 2012 to July 2015

ABSTRACT

The PSI-ENSI project PISA-II is the continuation

of PISA-I [1, 2] and is dedicated to the

development and application of deterministic

and probabilistic integrity assessment methods.

The project is focussed on the simulation of

structural and fracture mechanics behaviour

of Reactor Pressure Vessels (RPV) subjected to

pressurized thermal shocks (PTS). Parameter

studies are showing the sensitivity of failure

probabilities on uncertainties in assumed model

parameters. Therefore, the load transients are

studied with the system code RELAP5, followed

by Computational Fluid Dynamic (CFD)

simulations. The results from the latter will be

used for the exact evaluation of time and location

dependent stresses by three dimensional

finite element calculations.

The main results achieved within the report

period 2012 are:

Probabilistic Fracture Mechanics (PFM) code

FAVOR was successfully applied to study the

conditional probabilities of crack initiation

and failure of a RPV with postulated cracks,

subjected to PTS loads.

Quantitative analyses of the Warm Pre-Stress

Effect (WPS) by using the Chell and Wallin

models were performed.

Elastic-perfect-plastic calculations were compared

with elasto-plastic ones.

Constraint effects at the crack front were

considered by T-stress calculations.

The Master Curve method has been applied

with the FAVOR code for a more realistic

consideration of the fracture toughness of

the RPV material.

The ASME model lead to more conservative

results than the FAVOR model, whereas the

Master Curve method yield the least conservative

results.

Since the Master Curve method is based on

fracture mechanics tests, it is more realistic

and promising than the FAVOR and ASME

model for considering the fracture toughness.

Valuable knowledge and expertise in the field

of RPV safety assessment were acquired within

the project.

ENSI Erfahrungs- und Forschungsbericht 2012 149

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