Application of Leak-Before-Break concept in 316LN austenitic steel pipes welded using 316L

Gabriel Giannini De Cunto,Waldemar Alfredo Monteiro,Arnaldo Homobono Paes De Andrade

doi:10.3221/igf-esis.41.44

Abstract

The paper presents a study of the application of Leak-Before- Break (LBB) concept in a relatively small-diameter high energy reactor coolant line, where it is proposed type AISI 316LN to be used as base material welded with type AISI 316L coated electrode considering a pipe with diameter of 273 mm. The pipe material was characterized in terms of tensile test with Ramberg-Osgood analyses and fracture toughness tests with J-Resistance curve determination, considering base material, weld joint and heat affected zones. For the mechanical properties found in tensile tests and using the PICEP software, were determined the leak rate curves versus crack sizes, to determine the size of a detectable leakage crack, and the critical crack sizes, considering failure by plastic collapse. For the critical crack sizes found in weld, which presented the lowest toughness, J-Integral analysis was performed considering failure by tearing instability. Results show a well-defined mechanical behavior where base material has a high toughness, weld has a low toughness, and HAZ showed intermediate properties. For the load limit analysis, the lowest critical crack size was found for base material presenting circumferential cracks. For J- Integral analysis, it was demonstrated that failure by tearing instability will not occur.

Highlights

The LABGENE is a 48 MW thermal PWR prototype reactor under development in Brazil, that aims to develop and test the capability to design small and medium power reactors for electricity production and for nuclear propulsion
HMechanical tests results ot tensile test results show a well-defined behavior among the three zones, where the base material has a high toughness behavior with relative low yield strength and high uniform elongation, the weld show a low toughness behavior with relative high yield strength and low uniform elongation, and the heat affected zone (HAZ) showed intermediate mechanical properties between the base material and the weld
The results of all base material and HAZ are not valid according to ASTM E1820-13 because JQ is much larger than the Jlimit value

Summary

Introduction

The LABGENE is a 48 MW thermal PWR prototype reactor under development in Brazil, that aims to develop and test the capability to design small and medium power reactors for electricity production and for nuclear propulsion. A deterministic LBB evaluation performed using guidance from NUREG-1061 Volume 3 [1] and SRP 3.6.3 [2] is usually used to demonstrate this low probability of pipe rupture. This examination is based on fracture mechanics analysis that is used to demonstrate that a crack leak, present in a pipe, can be detected by the plant leak detection systems, with a factor of 10 between the predicted leakage and the plant leakage detection capability. Inadequate mechanical properties in any of these three zones is a threat to the LBB analysis

Methods

Results

Conclusion