Chapter 3—Radiation Surveillance Program for Combustion Engineering, Inc. Reactor Vessel Materials

Abstract

The Radiation Surveillance Program for Combustion Engineering (C-E) Reactor Vessel Materials is designed to provide the operating utility with the capability of determining the radiation-induced changes in the mechanical and fracture toughness properties of the materials in the region of the reactor vessel encompassing the core. The term “materials” is used to collectively describe the metallurgical characteristics of base metal, deposited weld metal, and the heat-affected-zone (HAZ) metal. By conducting such determinations periodically, the neutron-induced changes in the initial reference temperature (RTNDT) can be assessed by direct measurement and the conservatism in the planned adjustments to plant operating parameters to compensate for the RTNDT changes can be verified.

Radiation embrittlement in the pressure-vessel steels of nuclear power plants

“…The muchgreater@BTTfortheweldmetal is consistent with the general conclusion that the weld metal is the most radiation sensitive material in the beltline of the Maine Yankee vesseJ. 16 For the past two decades or so, since the work ofPotapovs and Hawthorne,17 copper has been recognized as a major promoter of radiation embrittlement, and the three design curves in Figure 4 reflect this awareness. More recently, however, nickel also has been implicated as giving rise to greater amounts of radiation embrittlement, particularly in steels with higher copper contents.…”

“…The reactor core is contained within pressure vessels made of heavy-section ferritic steel. Because PWRs operate at higher pressures than BWRs (about 16.5 MPa versus about 8.25 MPa), the PWR vessels are smaller and thicker. PWR pressure vessels are typically 3.4-4.3 m in diameter and 20-23 cm thick, while BWR pressure vessels are 5.2-6.4 m in diameter and 15-18 cm thick.…”