[NTG-context] running PlainTeX from beta

I have some plaintex code to run from the ConTeXt beta-distribution, because I didn't install the complete TeXp-distribution (and if possible prefer to keep it that way). I did not fare well with running "texexec --make plain" and "mtxrun --script plain myfile.tex" The first command does not give a sign of dumping the plain format somewhere, the second command complains "I can't find the format file luatex-plain.fmt" It looks if I am on the wrong track for using luatex with plain. Will someone please be so kind to turn me in the right direction? Hans van der Meer