Pressurized Water Reactor Environment Effect on 316 Stainless Steel Stress Hardening/Softening: An Experimental Study

Abstract

In USA there are approximately 100 operating light water reactors (LWR) consisting fleet of both pressurized water reactors (PWR) and boiling water reactors (BWR). Most of these reactors were built before 1970 and the design lives of most of these reactors are 40 years. It is expected that by 2030, even those reactors that have received 20 year life extension license from the US nuclear regulatory commission (NRC) will begin to reach the end of their licensed periods of operation. For economical reason it is be beneficial to extend the license beyond 60 to perhaps 80 years that would enable existing plants to continue providing safe, clean and economic electricity without significant green house gas emissions. However, environmental fatigue is one of the major aging related issues for these reactors, and may create hurdles in long term sustainability of these reactors. To address some of the environmental fatigue related issues, Argonne National Laboratory (ANL) with the sponsorship of Department of Energy’s Light Water Reactor Sustainability (LWRS) program trying to develop mechanistic approach for more accurate life estimation of LWR components. In this context ANL conducted many fatigue experiments under different test and environment conditions on 316 stainless steel (316SS) material that is or similar grade steels are widely used in US reactors. Contrary to the conventional S∼N curve based empirical fatigue life estimation approach, the aim of the present DOE sponsored work is to understand material ageing more mechanistically (e.g. time dependent hardening and softening) under different test and environmental conditions. Better mechanistic understanding will help to develop computer based advanced modeling tools to better extrapolate stress-strain evolution of reactor component under multi-axial stress states and hence to help predicting their fatigue life more accurately. In this paper (part-I) the fatigue experiments under different test and environment conditions and related stress-strain results for 316 SS are discussed. In another paper (part-II) the related evolutionary cyclic plasticity material modeling techniques and results are discussed.

A Deterministic and Probabilistic Framework for Forecasting of Time-Series Damage States and Associated End-of-lIfe of a Pressurizer Water Reactor Surge Line under Design-Basis and Grid-Load-Following Loading Conditions

“…To avoid this issue, we developed a test strategy based on the test results of two initial fatigue tests. First, based on the results of an earlier stroke-controlled test (ET-F13 test [27] conducted with constant stroke amplitude and constant stroke rate) we estimated the initial mapping parameters between observed strain and applied stroke input. The ET-F13 strain versus applied stroke input for the first cycle is shown in Figure 4.2.…”

Methodology for Stress-Controlled Fatigue Test Under In-Air and Pressurized Water Reactor Coolant Water Condition and to Evaluate the Effect of Pressurized Water Reactor Water and Loading Rate on Ratcheting

“…Thus, the axial Transactions of the ASME deformation of the specimen must be measured or controlled by either frame crosshead displacement (i.e., stroke) or frame actuator position. Previously [13][14][15], we conducted PWR environment tests by controlling the crosshead displacement. To predict the strain from the crosshead displacement data of the PWR tests, we used stroke-strain mapping functions generated from in-air tests data, where the in-air tests were controlled by the same crosshead displacement used for PWR tests.…”

“…The details on stroke-strain calibration can be found in Refs. [13] and [14]. In this work, we followed the similar method for position-strain calibration which was used to predict strain from actuator position measurements during PWR environment tests.…”

Full-scale 3-D finite element modeling of a two-loop pressurized water reactor for heat transfer, thermal–mechanical cyclic stress analysis, and environmental fatigue life estimation

“…Hence it is justified to consider one fatigue cycle stress/strain results for fatigue evaluation. However, if cycle dependent elastic-plastic material parameters [39][40][41] are used the FE model may estimate different stress/strain results for different fatigue cycles, depending on the component geometry, boundary conditions, and loading severity. In that case it is essential to consider stress-strain from individual cycles separately.…”