The reasons for change

To meet enhanced safety requirements and achieve improvements in construction and operation a number of departures have been made from earlier AGR designs. The reactor core has been increased in size to accommodate approximately 10% more fuel channels. The boilers have also increased in size as a consequence of reactor gas outlet parameters and boiler constraints, and this increases the pressure vessel external diameter from 28.7 m to 33.8 m and height from 36 m to 39.3 m. Increased remote in-service inspection provision has been made so permitting examination of a wide range of items to check their integrity throughout life. Seismic criteria have to be met: design basis earthquake and safe shutdown earthquake. Special attention has been given to diversity of shutdown and post trip heat removal systems especially for the more frequent fault conditions. The present estimated cost, at March 1980 is pounds 1200 million. A system of quality assurance has been adopted for all safety related areas of the project. (U.K.)