Primary system concept designs

Each of the above alternatives was carried to the point of preliminary drive system sizing and overall subsystem layout. Based on that information, our evaluation of the alternatives has led to the selection of the conventional crank-driven orbital scroll as the primary design direction. This represents a conservative choice in the design of this system element, consistent with the overall need embodied in the program objectives to demonstrate the performance of the overall system concept. 

This program was first developed (Petrangeli, 1983 Petrangeli et al., 1993) for the study of a new safety system (the CRS described in Appendix 10) based on the voluntary depressurization of the primary system and on the passive injection (by accumulators under pressure) of cooling water. This basic concept has been subsequently applied to various reactor designs. 

A modular power center, commonly found in computer-room installations, provides a comprehensive solution to AC power-distribution and ground-noise considerations. Such equipment is available from several manufacturers, with various options and features. A computer power-distribution center generally includes an isolation transformer designed for noise suppression, distribution circuit breakers, power-supply cables, and a status-monitoring unit. The system concept is shown in Fig. 10.268. Input power is fed to an isolation transformer with primary taps to match the AC voltage required at the facility. A bank of circuit breakers is included in the chassis, and individual preassembled and terminated cables supply AC power to the various loads. A status-monitoring circuit signals the operator if any condition is detected outside normal parameters. 

The confinement system for NFR is based on separation of energy and controlled release concepts. The system Is designed so the thermal energy in the primary loop would be released from the building... 

Simplified operational licensing requirements. The MASLWR concept utilizes natural circulation for primary coolant flow and relies on passive safety systems. This results in a reduced amount of operator training and plant certification required for plant licensing. Due to the small scale of the concept, design certification based on testing is simplified because of the relatively low cost of a full-scale prototype facility. 

SCOR is a compact reactor in many ways similar to BWRs and the SIR concept [10]. The containment is assumed consist of a pressure suppression compartment. The specific feature of the SCOR design is that it includes two physically separated areas one located below the mating surface that couples the reactor and the SG and another one located above this surface. The upper area contains the reactor vessel with all its small diameter pipe connections. The lower area is in contact with only the secondary system when the reactor is in operation, and with the primary system during maintenance operations. 

The hybrid heat transport system (HHTS). The MR employs natural circulation and a self-pressurized primary coolant system, altogether resulting in a simple primary system design without reactor coolant pumps and pressurizer it also reduces maintenance requirements. In addition, the use of HHTS concept makes it possible to reduce the size of the reactor vessel. The HHTS is a kind of two-phase natural circulation system. The coolant starts boiling in the upper part of the core two-phase coolant flows up in the riser and is condensed and cooled by SGs. Such design approach increases coolant flow rate and thus, reduces the required height of the reactor vessel (RV) to transport the heat from the core, Fig. VI-2. 

Early LFR concepts initially considered both pool-type and loop-type primary coolant systems however, more recent designs have focused on pool-type primary systems, mainly to avoid the seismic issues associated with lead-filled piping. 

While the European design efforts leading to the ELSY/ELFR/ALFRED series of LFR concepts were being conducted, parallel efforts were being pursued to develop an array of innovative designs. Projects in Russia, Japan, Korea, the USA, and China concurrently pursued a variety of different concepts with considerable innovation and creativity with respect to primary system design as well as the entire reactor systems. 

In summary, the primary system designs of the GIF reference reactors (as well as a multitude of other design concepts in various stages of development) provide a range of different approaches to primary system design appropriate for LFR reactor systems. 

The ELFR is a design resulting from the update and modification of the earlier ELSY reactor concept. Fig. 6.2 provides an overview sketch of the primary system configuration of the ELFR reactor. 

The incentives for considering the pool concept as an alternate design are its safety against primary pipe leaks and ruptures and its compact design, which may lead to lower overall capital costs. Potential advantages of the loop concept relate mainly to the ease of maintenance and access to primary system components, thus reflecting potential increases in overall plant availability. There also has been more experience behind this concept. It provides a relatively clear-cut separation of primary system components and places components in a more controllable and predictable environment. These considerations are discussed in more detail in the following section. 

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