Pressure vessel fracture studies pertaining to the PWR thermal-shock issue: experiments TSE-5, TSE-5A, and TSE-6

Abstract

Thermal-shock experiments TSE-5, TSE-5A, and TSE-6 were conducted for the purpose of investigating the behavior of surface flaws under pressurized-water-reactor (PWR) overcooling-accident conditions. These experiments were the fifth, sixth, and seventh in a series of thermal-shock experiments conducted with large steel cylinders (A 508 class-2 chemistry; 991-mm OD by 76- and 152-mm wall by 1.2-m length) as a part of the Heavy-Section Steel Technology (HSST) Program for this purpose. For each of these experiments, the initial flaw was on the inner surface and extended the full length of the cylinder. The thermal shock was applied to the inner surface only, and this was accomplished by effectively dunking the test cylinder, initially at approx.93/sup 0/C, into a large volume of liquid nitrogen. Results of the experiments have confirmed that (1) linear-elastic fracture-mechanics is valid for thermal-shock loading; (2) crack arrest will take place in accordance with recently developed crack-arrest concepts; (3) crack-arrest toughness values for rising and falling K/sub I/ fields are the same; (4) warm prestressing is effective in preventing crack initiation; (5) thermal shock alone cannot drive a flaw all the way through the wall; (6) dynamic effects for PWR-vessel thermal-shock loading conditions are negligible; (7) in the absencemore » of cladding and under severe thermal-shock loading conditions, finite-length flaws will extend on the surface to become very long; and (8) there can be very large scatter in small-specimen fracture-toughness data. 24 refs., 114 figs., 29 tabs.« less