Material Interactions in Severe Accidents – Benchmarking the MELCOR V2.2 Eutectics Model for a BWR-3 MARK-I Station Blackout: Part I – Single Case Analysis

Journal Article · Thu Sep 02 00:00:00 EDT 2021 · Nuclear Engineering and Design

DOI:https://doi.org/10.1016/j.nucengdes.2021.111292· OSTI ID:1822227

Albright, Lucas I. ^[1]; Andrews, Nathan ^[2]; Humphries, Larry L. ^[2]; Piro, Markus H.A. ^[3]; Sjoden, Glenn E. ^[4]; Luxat, David L. ^[2]; Jevremovic, Tatjana ^[5]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Univ. of Utah, Salt Lake City, UT (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
3. Ontario Tech University, Oshawa, ON (Canada)
4. Univ. of Utah, Salt Lake City, UT (United States)
5. International Atomic Energy Agency, Vienna (Austria)

Here in this analysis, the two material interaction models available in the MELCOR code are benchmarked for a severe accident at a BWR under representative Fukushima Daiichi boundary conditions. This part of the benchmark investigates the impact of each material interaction model on accident progression through a detailed single case analysis. It is found that the eutectics model simulation exhibits more rapid accident progression for the duration of the accident. The slower accident progression exhibited by the interactive materials model simulation, however, allows for a greater degree of core material oxidation and hydrogen generation to occur, as well as elevated core temperatures during the ex-vessel accident phase. The eutectics model simulation exhibits more significant degradation of core components during the late in-vessel accident phase – more debris forms and relocates to the lower plenum before lower head failure. The larger debris bed observed in the eutectics model simulation also reaches higher temperatures, presenting a more significant thermal challenge to the lower head until its failure. At the end of the simulated accident scenario, however, core damage is comparable between both simulations due to significant core degradation that occurs during the ex-vessel phase in the interactive materials model simulation. A key difference between the two models’ performance is the maximum temperatures that can be reached in the core and therefore the maximum ΔT between any two components. When implementing the interactive materials model, users have the option to modify the liquefaction temperature of the ZrO₂-interactive and UO₂-interactive materials as a way to mimic early fuel rod failure due to material interactions. Through modification of the liquefaction of high melting point materials with significant mass, users may inadvertently limit maximum core temperatures for fuel, cladding, and debris components.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: NA0003525
• OSTI ID: 1822227
• Report Number(s): SAND--2021-7616J; 697219
• Journal Information: Nuclear Engineering and Design, Journal Name: Nuclear Engineering and Design Vol. 382; ISSN 0029-5493
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
36 MATERIALS SCIENCE
Eutectics model
Interactive materials model
MELCOR
Material interactions
Severe accident