Cladding burst behavior of Fe-based alloys under LOCA

Abstract

Burst behavior of austenitic and ferritic Fe-based alloy tubes has been examined under a simulated large break loss of coolant accident. Specifically, type 304 stainless steel (304SS) and oxidation resistant FeCrAl tubes were studied alongside Zircaloy-2 and Zircaloy-4 that are considered reference fuel cladding materials. Following the burst test, characterization of the cladding materials was carried out to gain insights regarding the integral burst behavior. Given the widespread availability of a comprehensive set of thermo-mechanical data at elevated temperatures for 304SS, a modeling framework was implemented to simulate the various processes that affect burst behavior in this Febased alloy. The most important conclusion is that cladding ballooning due to creep is negligible for Fe-based alloys. Thus, unlike Zr-based alloys, cladding cross-sectional area remains largely unchanged up to the point of burst. Therefore, for a given rod internal pressure, the temperature onset of burst in Fe-based alloys appears to be simply a function of the alloy's ultimate tensile strength, particularly at high rod internal pressures.

Severe Accident Analysis Of BWR Core Fueled With UO₂/FeCrAl with Updated Materials and Melt Properties From Experiments

“…Tests such as those conducted at the QUENCH facility are needed. Other information, such as that from burst testing [34], is underway. The additional information needs include knowledge of the possible eutectics formed during degradation, the failure points of the oxides under prototypic conditions, and the relocation characteristics of the collapsed fuel rods.…”

“…In reality, the rod burst phenomenon is both function of rod pressure and temperature. The burst characteristics of 1 st generation FeCrAl alloy claddings have been investigated [34]. For the same hoop stress, the FeCrAl clad was shown to have improved burst characteristic, ~10% higher burst onset temperature.…”

Risk-Informed Safety Analysis for Accident Tolerant Fuels

“…Some experiments have demonstrated a certain increased capacity (about 20%) of the FeCrAl fuel to the clad breaching under hightemperature and high-pressure conditions. 65 However, in this study we did not modify the code algorithm that predicts clad rupture, so the FeCrAl results should be considered somewhat conservative concerning clad breaching. A flowchart of the new RELAP5-3D workflow for the fuel clad oxidation model is shown in Fig.…”

Accident tolerant clad material modeling by MELCOR: Benchmark for SURRY Short Term Station Black Out

“…One can also see from the lead-up phase, decay heat and the stored energy cannot be rejected to a heat sink, which causes the fuel and clad temperature to increase. Zircaloy clad can fail if high enough temperatures are reached, and this can also generate significant hydrogen from oxidation (~1500 K; Massey et al, 2016). However, if ATF clad material is used, these effects could be significantly delayed or, potentially, avoided (Farmer et al, 2014).…”