The tertiary containment system includes the reactor hall, rooms containing tritium processing equipment, the reactor building itself, the tritium effluent removal system (TERS), and the emergency tritium containment system (ETCS). The TERS is designed to operate on routine tritium losses while the ETCS is used only under abnormal conditions. . As with the primary and secondary systems, the reactor building is subdivided to reduce both the extent of loss and the extent of contamination in the event of a leak. Each reactor hall has a volume of 8.7 x 10^ m^ and may be divided radially to provide the least impediment to maintenance operations. The reactor building is maintained at 8.4 x 10^ Pa during operation, and the pressure can be reduced to 1.3 x 10^ Pa under emergency conditions. About 20% of the building volume atmosphere would be circulated each day, from areas of smallest to largest radioactive hazard before leaving through a stack of sufficient height to guarantee proper dispersal of the effluent. Under normal operation, this stack effluent would contain about 1 Ci per day. The emergency tritium containment system (ETCS) consists of a heated catalyst to oxidize HT and T2 to HTO and T2O, alumina beds presaturated with water at 100% humidity, and the required air handling equipment. The ETCS is used in the event of a simultaneous breakdown of both the primary and secondary systems to rapidly detritiate air from contaminated areas of the reactor building. During cleanup, the inlet dampers of contaminated areas are closed and only a small fraction of fresh air is allowed to circulate to reduce tritium losses from the stack. One further source of tritium leakage is the boiling water coolant. It has been calculated that the leak rate of tritium into the cooling water will be limited to a few curies per day. In the event that the leak rate increases, it is possible, without much increase in costs, to add equipment for removing tritium (in the range of 0.001 to 10 Ci/mL) by combined electrolysiscatalysis or by molecular photo-excitation. The 14-MeV neutrons from the fusion reaction induce radioactivity in the structure surrounding the plasma. Most of the activity originates in the inner region of the blanket. The blanket should be replaced every two years, and the material processed and stored on the plant site. 3.3 COST CHARACTERIZATIONS A comparative assessment of the electric generation costs for the SPS and alternative technologies requires that the cost components of each system be characterized on a consistent and normalized basis. Unfortunately, technology cost estimates from previous efforts were usually developed under assumptions that differed from study to study, and are inconsistent with the characteristics assumed for the nominal reference systems in this assessment. Thus the remainder of this section quantitatively documents the procedure used to derive a set of consistent capital and operation and maintenance (O&M) costs for the SPS and alternative technologies.
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