This works fine for me. I have attached the output.
result = Table[<|"t" -> t, "k" -> k, "result" -> First@{(Nu/Nuc)/(fRe/fRec)}|>,
{t, 0, 1, 0.01}, {k, 0.001, 1, 0.01}] // Flatten // Dataset
Export["results.xlsx", results]
Why do you need to use Excel for plotting? Why not plot in Mathematica?
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