PURPOSE: To obtain a method for deciding simply a hardening condition of a plastic solidified body, by detecting the generation of heat by a hardening reaction of therosetting plastics by detecting and measuring a temperature of the solidified body at the time of manufacturing the solidified boby by mixing the thermosetting resins with radioactive waste and hardening it.

CONSTITUTION: Radioactive waste is made powdery by a vertical type thin film drier and this powdery body is mixed with thermosetting plastics such as epoxy resin, unsaturated polyester etc. in a mixing vessel. 20:80W60:40 mixing ratios of the powdered body with the thermosetting plastics, are suitable. Next, polymerization inhibitor such as methyl ethyl ketone peroxide etc. and polymerization accelerators such as cobalt naphthenate etc., are mixed. Each of the blending quantity of the polymerization initiator and the polymerization accelerator is about 0.5pts.wt. for 100pts.wt. thermosetting plastics. After mixing, the sample is put in another vessel and a temperature is measured continuously by attaching a thermocouple nearly at the central part of the side face of the vessel. Generation of the head by the hardening reaction is shown by a rise in temperature and whether the hardening is carried out sufficiently or not, is decided by a degree of this temperature rise.