The CCR is a BWR and was proposed by the Toshiba Corporation (Heki et al., 2005) in cooperation with the JAPC (Okazaki et al., 2011). The targets for the design are the same as in the IMR and are summarized in Table 19.1. A schematic view of the reactor is shown in Figure 19.2. Its major specifications are summarized in Table 19.3. The core is shortened and cooled by the natural circulation of the coolant without the recirculation pumps. One of the characteristic features for the system simplification for this concept is the high pressure (about 4 MPa) resistant compact containment vessel without the suppression pool. The control rod drive mechanism is mounted at the top of the reactor vessel and, hence, the penetration at the bottom of the reactor vessel can be eliminated.

The power output is 423 MWe. The average discharge burnup is 45 GW d/t and the refueling interval is 24 months. The effective length of the core is shortened to 2.2 m to increase the driving force for the natural circulation core cooling. The system pressure is 7 MPa and is the same pressure as in the normal BWR. For the safety system design, the CCR concept is significantly simplified. That is, it does not require the ECCS and only requires the IC (isolation condensers) cooling system for decay heat removal. The IC system is a passive component system and is designed to remove decay heat for three days without any operation by the operators. As the control rod drive mechanism of the CCR is different from that of the BWR, and is also different from that in a PWR considering the operation in the steam environment, the abrasion-resistant tests for the material in the steam environment were conducted to confirm the applicability.

Containment Top mounted CRD

vessel. falling under gravity

Reactor pressure

vessel

Low

pressure

loss

water

separator

Control

rods

Reactor

core

(short

length)

f5.5 m

Figure 19.3 Construction cost evaluation of an IMR and a CCR.

From the economic point of view, the estimation results on the construction cost using the same evaluation method as for the large reactor are given in Figure 19.3 for the IMR and CCR concepts (Okazaki et al., 2011). In the figure, the unit construction cost per kWe are compared for the IMR, CCR and ABWR cases. The values are normalized by that of the ABWR case with 1356 MWe output. It can be recognized

that both the IMR and CCR concepts are at almost the same economic level as the typical large reactor of ABWR. The main reasons for this economic achievement are the simplification of the system by eliminating the systems and components and, hence, the resultant downsizing of the containment vessel. In addition, the downsizing of buildings due to the simplification of the systems and components enables the construction and civil engineering costs to be reduced. However, it should be noted that this evaluation is performed assuming that the new plant shares the port and the switching yard with the existing plant, and the additional costs for those facilities are required if the plant is established in a new site.

For further developments of CCR, optimization studies will be performed. In addition, possibilities of developing the concepts with various output range are considered, utilizing the technologies gained in the previous development. For example, a concept of a plant with 100 MWe output is developed based on the CCR concept.