There is one pressurized water reactor (PWR) in the U.K., at Sizewell, which is currently under construction.There are several steel MAGNOX gas-cooled reactors in operation.The MAGNOX reactor operates at a lower pressure than a PWR, and has a large, relatively thin-walled ferritic steel reactor pressure vessel.The wall thickness is typically between 3 to 4.5 in.There is currently no formalized code or standard in the U.K. to which reactor pressure vessels are designed and operated.Guidelines have been published and these will be reviewed in this document.This document will present the current industry practice in the U.K. for assessing the integrity of steel reactor pressure vessels.The findings and recommendations in the second report from the Marshall Study Group on the Integrity of Pressurized Water Reactor Pressure Vessels are given particular emphasis.