Is "Rdxd2" algebraic chess notation valid? Is the algebraic notation Rdxd2 valid?

If there is a problem with this notation, then how can it be corrected?
If you have two rooks, standing on different files (one of them on the d-file), that could capture on d2, then Rdxd2 is the correct notation.
If you have two rooks on the d-file, and both can take on d2, then use the rank number to disambiguate, for instance R1xd2.
This is according to the Algebraic System required by FIDE's Laws of Chess (see appendix C, paragraph C.10).
In the very, very rare case that you have more than two pieces of the same kind that can capture on the same square, it might be necessary to use both rank and file to disambiguate. This could theoretically be needed for queens, bishops and knights, but never for rooks. As Martin Bonner explains in the comments, for this to be necessary you would need to have a piece which is on the same rank as another of the same kind and the same file as a third of the same kind, and all three attack the same square. That is not possible with rooks.