SYMPOSIA PAPER Published: 01 January 1986

Annealing and Reirradiation Response of Irradiated Pressure Vessel Steels


This paper summarizes the results of a series of tests on irradiated, annealed, and reirradiated welds performed to provide a data base for annealing a reactor pressure vessel. Specimens from three test welds were irradiated to neutron fluences of 8 × 1018 n/cm2 and 1.5 × 1019 n/cm2 (E > 1 MeV) with most of the high-fluence specimens receiving an intermediate anneal. Anneals were performed at temperatures ranging from 340 to 454°C with the primary emphasis placed on one-week anneals. Partial recovery of the yield stress, Charpy transition temperature, Charpy upper-shelf energy, and upper-shelf fracture toughness (JIc) was noted after annealing at all temperatures. The least recovery was observed in the upper-shelf fracture toughness. In sharp contrast, the Charpy upper shelf was fully recovered after the 454°C, one-week anneals.

The increases in the yield stress and the Charpy transition temperature during the second cycle of irradiation were significantly smaller than the increases in the first cycle. The increase in these properties during the second cycle was only marginally larger than the increase in the irradiated but not annealed materials. These results indicate that the beneficial effects of annealing on the Charpy transition temperature are maintained during reirradiation.

A model of irradiation embrittlement and annealing based on copper precipitate coarsening is described. It has been previously demonstrated that a primary cause of embrittlement in these steels is the formation of small copper precipitates. The coarsening of the precipitate structure during annealing would produce a stable structure, which would cause a recovery of mechanical properties and not be subject to large embrittlement rate on reirradiation.

Author Information

Lott, RG
Westinghouse R & D Center, Pittsburgh, PA
Mager, TR
Westinghouse Water Reactors Division, Monroeville, PA
Shogan, RP
Westinghouse R & D Center, Pittsburgh, PA
Yanichko, SE
Westinghouse Water Reactors Division, Monroeville, PA
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Developed by Committee: E10
Pages: 242–259
DOI: 10.1520/STP23039S
ISBN-EB: 978-0-8031-4975-5
ISBN-13: 978-0-8031-0473-0