It seems that G4RadioactivityTable is not filled in MT mode (it is filled in sequential mode) The problem can be seen in example rdecay02, Run::WriteActivity(), with proton-beam.mac
Th immediate problem is the line if (isMaster) fRun->EndOfRun(); in RunAction::EndOfRunAction(const G4Run*) The master RDM process carries no data, while each of the worker RDM threads do. So no data gets written to the tables in MT mode. A temporary fix would be to remove the test for master and just do fRun->EndOfRun(); Then the tables will be filled, but there will be a table for each thread at the end of the run so that some post-processing of the output will need to be done to collect everything. The proper fix, however, is deeper and requires a re-design of the RDM biased mode. Basically radioactive decay collects run data in a table in the process, which in general, processes should not do. So I will propose this redesign of the radioactive decay biased mode as a project and close this report as "WONTFIX"