Steam Oxidation Testing in the Severe Accident Test Station

Steam Oxidation and Burst Testing in the Severe Accident Test Station

“…Thus, the steam oxidation behavior of candidate materials is a key metric in the evaluation of ATF concepts and also an important input into models [20][21][22]. Prior work has emphasized collecting steam oxidation and integral data on FeCrAl cladding so that the modeling uses the correct physical properties [23][24][25][26]. Traditionally, high temperature oxidation studies have included isothermal testing to measure reaction rates which then can be compiled to determine an activation energy such that oxidation can be modeled over a wide temperature range [7].…”

“…Also, because conventional coal-and nuclear-powered steam plants only operate at ≤600°C and advanced concepts envision 760°C as a peak temperature [27], the prior steam testing did not include such high temperatures as are now being considered (1000°-1700°C). In addition, since most accident scenarios include steadily increasing temperatures, more recent results have focused on "ramp" testing [6,12] and have examined the effect of varying the ramp rate or other variations in the heating schedule [24][25][26]. Thus, with no prior literature for comparison, some of the new steam oxidation behavior of FeCrAl and FeCr alloys has been surprising and difficult to interpret.…”

Steam Oxidation, Burst and Critical Heat Flux Testing of FeCrAl Cladding in the Severe Accident Test Station

“…Higher temperature testing of C26M specimens is in progress. The current hypothesis is that reducing the Cr content from 21% to 12-13% (Table 1) reduces the maximum temperature where a protective alumina scale can form on FeCrAl in steam, particularly when the ramp rate is >2°C/min [25]. However, the protective behavior of C26M at 1475°C suggests that temperature debit is minimal for the new commercial tubing.…”

“…An ATF cladding would significantly reduce the rate of heat and hydrogen generation in the core during a coolant-limited severe accident [16][17][18]. In the search for materials with steam oxidation rates that are 100× slower than current Zr-based alloys at ≥1200°C, FeCrAl alloys quickly became the focus of research at ORNL including alloy development [8], physical properties [9,10,[12][13][14][19][20][21][22][23] and integral data [24][25][26][27] to populate models [28][29][30][31][32].…”

“…While the high temperature oxidation behavior of FeCrAl alloys has been studied for almost 60 years [33,34], it was typically studied isothermally to measure reaction rates and activation energies [7] and it was not studied in steam at such high temperatures above current advanced steam concepts of 760°C [35]. More recent experiments have focused on "ramp" testing of low-Cr Fe-(10-13wt.%)Cr-(5-6%)Al compositions [6,12] and have examined the effect of varying the ramp rate or other variations in the heating schedule [25][26][27]. Experiments are now focusing on the new commercial C26M FeCrAl tubing that was inserted into Plant Hatch in February 2018.…”