Identifying Thermodynamic Mechanisms Affecting Reactor Pressure Vessel Integrity During Severe Nuclear Accidents Simulated by Laser Heating at the Laboratory Scale

In this work, radiance emission spectrometry is used to experimentally investigate the high-temperature behavior of the U-Fe-Zr-O system. Three-phase transitions are observed, in the vicinity of ~1100 K, ~1700 K and ~2200 K. Principal component analysis of the phase transition temperatures in the course of laser-heating thermal cycling indicates that the phase transition around ~1100 K is driven by the interaction of SS with metallic U, the phase transition around ~1700 K by the melting of SS, and the phase transition above ~2000 K by the eutectic melting of UO2. The results also reveal two hitherto overlooked interactions in the U-Fe-Zr-O system, which could have severe consequences for the containment of corium inside the reactor pressure vessel (RPV). Firstly, the phase transition temperatures of the samples varied extensively as a result of the laser-driven rapid thermal cycling. Variations of up to 390 K were observed in the phase transition temperatures, suggesting that, depending on the initial conditions of corium formation, the corium-driven ablation of the RPV wall could commence significantly earlier than the current state-of-the-art severe accident codes would predict. Additionally, evidence of a large exothermic reaction between zirconium and molten steel was observed upon stainless steel melting.

ATHANASAKIS-KAKLAMANAKIS Michail;  MANARA Dario;  VLAHOVIC Luka;  ROBBA Davide;  BOBORIDIS Konstantinos;  ERNSTBERGER Markus;  ELOIRDI Rachel;  AMADOR CELDRAN Pedro;  KONINGS Rudy; 

2023-11-22

TAYLOR & FRANCIS INC

JRC127666

0029-5639 (online),   

https://www.tandfonline.com/doi/full/10.1080/00295639.2022.2108643,    https://publications.jrc.ec.europa.eu/repository/handle/JRC127666,   

10.1080/00295639.2022.2108643 (online),