RADKFILE is a file that relates radicals and kanji. I found it in JQuickTrans and took it. The problem is that JQuickTrans uses a customized one, so you can't easily upgrade it. I'll work on that in the future.
This is right out of the file itself, so here's some credit where it's due:
# The file is based on work done in 1994/1995 by Michael Raine in which he
# analyzed all the JIS1/2 kanji and identified the constituent radicals and
# other common elements, with the intention of facilitating the selection of
# kanji within a dictionary program by identifying multiple elements.
# The file was revised by Jim Breen in September 1995.