[en] The behaviour of irradiated steels of the 18-10, 16-15, 16-35 type and high-nikel alloys during high-temperature tests under loading is analyzed. The results of inpile and post-irradiation tests of tube samles are generalized. The conclusion is made that tests after irradiation are not representative for the estimation of creep rate and time to fracture for chromium-nickel steels of the 18-9 and 18-10 types in the temperature range of 500-600 deg C. For the temperature range of 650-700 deg C the tests under irradiation and after it show approximately similar values of high-temperature strength. Nickel-based alloys such as O3Kh17N77TYuR for example, with higher strength in nonirradiated state that steels during irradiation at high temperature retain the strength only in the case of small time to fracture (about 200 g). At higher time to fracture materials with a more stable structure are recommended ( steels of the 18-10 and 16-15 type)