NOTFORPUBLICATION(COMMERCIAL)
These will be confined to cover gas volumes at low to moderate pressure in the lead cooled design but for the helium cooled version a larger outer containment volume and/or intermediate prestressed concrete containment may be required . 7 .9 .2 Preheating Preheating to about 600 °C for the salt circuits and 330 C for lead will be required . In some cases it will be more economic and convenient to heat whole spaces such as the reactor vault and processing plant, but where longer lengths of pipework are involved as in the lead pipes to the steam generators, trace heating would be preferred . No particular problems have been encountered with preheating on the ORNL MSRE . 7 .9 .3 Shielding
No calculations have been made . A nominal thickness of 3 metres has been allowed on the drawings at the critical positions . 7 .9 .4 Pumps The single stage centrifugal salt pumps shown in Design 1 can be similar in principle to those successfully tested in the ~SRE and in loops up to 16,000 hours running at 650 C . For the two stage semi-axial design basic development work may be, required ; in both cases development and testing will be required to successfully increase sizes to the 5-12 MW range . There is no direct experience of high power, continuously running lead pumps . The design principles would probably follow the sodium pump design developed f'or sodium fast reactors but with higher power and strength requirements . 1 .9 .5 Steam Plant
Standard steam conditions of 16 .3 MN/~2 (235O psig) at 838K (1050 °F) with reheat to 811K (1000 F) are proposed using once-through boilers . For costing and layout purposes a once-through U tube design or evaporator, superheater and reheater has been used . Units are duplicated in each of the main circuits to reduce the tube plate size . Two 1350 MW(e) gross output T/A sets are shown, although a greater number of lower power sets could be equally conveniently situated . Station load would be about 200 MW including approximately 160 MW pumping power, giving a net efficiency of 41 .7% .
29