Pre-test analyses for pressurized thermoshock tests. Vessel I

This report describes the pre-test analyses performed for the thermoshock tests with the first model pressure vessel conducted at the Prometey Institute in Gatsina, U.S.S.R.. The calculations were performed at the Nuclear Engineering Laboratory and at the Metals Laboratory of the Technical Research Centre of Finland. Mainly simplified calculation methods were used in the pre-test analyses. The temperature calculation was made using both a computer code based on the Fourier series and the finite-element method. As the next step the stresses due to internal pressure and thermal transient were calculated using both analytical formulas and the finite-element method. To evaluate the structural integrity, the VTTSIF program based on the influence function method was applied to obtain the stress intensity factor values, which were compared to material toughness values obtained from the Prometey Institute. So far, five tests have been made with the same model pressure vessel using four different flaw geometries. In the first three tests, the flaw was actually a blunt notch. In the last two tests (tests 4 and 5), a sharp pre-crack was produced before the test. Test 6, which is considered as the final test, will be performed using the same flaw as in test 5. The calculated temperatures and stresses are presented in this report. When these are compared to measured values, a good correlation is observed. For each flaw the assessment is performed and for the last flaw geometry (test 6) the calculated stress intensity is presented as a function of loading time and crack tip temperature. When this stress intensity factor is compared to the material fracture initiation toughness values obtained from the Prometey Institute, crack initiation is clearly predicted.