Typical examples of integral circuits are the advanced gas-cooled reactors and the type of reactor used most commonly for ship propulsion. The original C02-

cooled reactors (Magnox) were of the loop type. However, the development of large concrete pressure vessel technology allowed the incorporation of the steam generators and circulators inside the pressure vessel, as illustrated in Figure 2.5. A typical marine reactor is illustrated in Figure 3.7, where the circulators, steam gen­erators, and reactor core are all encapsulated in a single steel pressure vessel.

The great advantage of the integral type of circuit is that all the primary cir­culating fluid is contained within the vessel, removing the need to circulate the primary fluid through connecting pipework to the steam generator. A possible accident source in the loop-type circuit is the rupture of one of the primary coolant pipes, and this is obviated in the case of the integral circuit.