The ETGBR grew out of the AGR technology developed in the UK during the 1970s. The core design took advantage of lessons learned from both AGR technology and the fuel design took advantage of experience of the sodium-cooled fast reactor (SFR) experience.

An important objective for the fuel and core design was to obtain a good breeding gain. The fuel consisted of MOX or UOX in a steel clad. Reactivity was controlled by three diverse and separate control rod systems for both control and shutdown. The burn-up target was 10%.

The reactor coolant system consisted of an integrated AGR design, with the boiler and circulators contained in a pre-stressed concrete pressure vessel. The main components were based on AGR technology in terms of materials and design. Since the core temperatures were cooler than those for AGRs (limited by maximum clad temperature), the cooling system had to withstand a less demanding environment than for AGRs.

The containment was designed to be less embracing compared with the primary/se — condary containment adopted for LWRs. It was, however, vented to mitigate the release under severe accident conditions.

It was felt that the design and safety philosophy of the ETGBR could be potentially licensable in the UK. There has also been recent interest in the design because it can be flexible in its fuel cycle. This could provide the option of achieving modest breeding or alternatively to enable the burning of plutonium and minor actinides.

The cost was reviewed in the 1970s, being found to be 10% greater than a PWR of the day. These costs were favourable in comparison with the AGR figure (increase of 25%) and the LMFBR figure of 60%. More recent studies have shown that the ETGBR could be economically competitive in comparison with other advanced reactors.

There have also been interest in GCFR technology in the US and a number of designs developed.