Embrittlement recovery due to annealing of reactor pressure vessel steels

Embrittlement of nuclear reactor pressure vessels

“…More commonly, the DT t are evaluated using regulatory equations based on a large collection of surveillance data from many plants. 3,4 The DT t is controlled by many variables. Recent, physically based, statistical fits to the U.S. surveillance database show that the DT t depends on T i , f, ft >1 , Cu, Ni, P, and product form (weld, plate, and forging).…”

“…Recent, physically based, statistical fits to the U.S. surveillance database show that the DT t depends on T i , f, ft >1 , Cu, Ni, P, and product form (weld, plate, and forging). 4 Single-variable, test reactor studies show that DT t also depends on a number of other variables including manganese content and final heat-treatment conditions. 6 Predictive models must also account for strong synergistic interactions between variables, such as copper nickel.…”

“…7 The rate of reirradiation embrittlement following annealing is an important issue, but it is not yet fully characterized.…”

“…Transition temperature shifts have exceeded 200∞C in some cases. 4 Hence, embrittlement must be considered in RPV integrity 3 assessments and, if severe, may require either premature plant closure or vessel annealing.…”

An Evaluation of Through-Thickness Changes in Primary Damage Production in Commercial Reactor Pressure Vessels

“…The correlation of embrittlement with the so-called fast fluence (i.e. neutron fluence above 1.0 MeV) is rationalized by the assumption that most atomic displacements are generated by the high energy portion of the spectrum, and is well supported by ongoing data analysis [3]. However, it is well known that neutrons of lower energy also contribute to embrittlement and the use of atomic displacements per atom (dpa) has been recommended [4,5] as an improved correlation parameter, particularly when differences in neutron energy spectrum must be accounted for.…”