PURPOSE: To discover defects of atomic energy machinery easily and also, to seal up defective parts, by using lead acrylate, iron acrylate etc. as main components of an impregnant and incorporating fluorescent material and hardening material etc.

CONSTITUTION: A permeating flaw inspecting impregnant is composed of e.g. 45% lead acrylate, 25% boron acrylate, 5% lead oxide, 5% barium sulfate, 5% thallium oxalate, 0.01% oil color, 3% polyoxy propylene glycol, 2% tetraethylene glycol, 5% aluminum oxide and 5% diacrylate oligoethylene glycol phthalate. A large quantity of metallic compounds of iron, beryllium, lithium etc. is used other than said compounds of lead and boron in order to shelter from γ-rays, hot neutron rays etc. The oil color is fluorescent material for deciding defective parts. This permeating flaw inspecting impregnant is hardened at a temperature higher than a certain temperature and the defective parts are sealed up by said impregnant.