Abbreviations

HLW = High Level Waste
ILW = Intermediate Level Waste
LILW = Low and Intermediate Level Waste
LLW = Low Level Waste
Mg = Mega gram, formerly t = Ton
SM = Heavy Metal, contents of uranium or uranium and plutonium in fuel elements
t = Tons
VLLW =  = Very Low Level Waste

You can find more information in the study
"Nuclear Waste Management in the European Union"