“…This molten material is therefore able to propagate and accelerate the core melt progression at rather low temperatures. 4,5) The control rod constituents found on the surface of most of the nozzles examined by ANL indicate that there had been a debris bed of control rod constituents deposited as solid particles on the lower head before the relocation of molten UO 2 and ZrO 2 occurred. The debris bed at the location of the most heavily damaged nozzle, H8, was overwhelmingly zirconium-rich and contained control rod alloy.…”