Irradiation and post-irradiation examination techniques for reactor pressure vessel steels at GKSS

For reactor pressure vessel steel irradiations, especially for big fracture mechanics specimens, FRG-2, a swimming-pool-type reactor operated in 7 m x 7 m pool at 15 MW, offers favorable conditions because of its good accessibility. Well proven irradiation devices for small specimens are at hand. They are equipped with a specimen carrier 56 mm in diamter and 480 mm in length which is inserted into a 3-zone electrical furnace, the time and space variations of specimen temperature can be kept within +-5 K. An irradiation rig for corrosion experiments in water at 3400C and 150 bar can be used to study the influence of the reactor primary water on the irradiation effects on small pressure vessel steel steel specimens. Rigs for fracture mechanics specimens are being developed; the main design goal is to maintain sufficiently small gradients of temperature and neutron fluence within the large specimens. For material testing of irradiated specimens two shielded impact test machines, which can be operated automatically, further a 50 kN tear testing machine for experiments in the temperature range from -1960C to +8000C, a hardness tester and several optical systems are installed in lead cells of the hot laboratory. A shielded drop weight machine has been brought into operation recently. The installation of a 250 t tear testing machine is being prepared. As yet irradiation experiments on steel 26NiCrMoV145 (comparable to ASTM A543), on several heats of steel 15MnMoNiV53, which is used for the pressure vessel of NS OTTO HAHN, on steel 13CrMo44, which some time ago had been selected for the pressure vessel of a HTR type reactor and lastly on steel ASTM A533 B within the IAEA coordinated program; on the latter steel also the effects of different recovery heat treatments and experiments with small fracture mechanics specimens have been performed. (orig.)