RE: Upgrading nuclear and medical waste to dark matter detectors
Unfortunately, not really (there is a catch; see below). All experiments exhibit null results so far, and the constraints on dark matter are hence stronger and stronger. However, one must keep in mind that these experiments target only a fraction of all available possibilities for dark matter. Only heavyish dark matter is probed, provided it is capable to recoil against the atomic nuclei making the detector. Which means that if dark matter is either too light or not interacting strongly enough, all sensitivity is lost. This is why new experiments are regularly designed and proposed, with the aim of opening up the parameter space in terms of probed regions.
Concerning positive results, there is however something: the DAMA/LIBRA signal, that has not been reproduced by any other experiment (so far). Results including 6 years of additional data have been released last year and the signal is still there (and is even stronger). This is stil a puzzle today and several experiments are trying to reproduce the DAMA/LIBRA results (you can for instance check this article). We however have to wait, probably for several years.