short time a f t e r the salt has been drained. The coolant-salt area, which includes the radiator, coolant pump, and coolant-salt drain tank, i s i n t h i s category. The west tunnel and the unshielded areas of the blower house are other examples. Equipment i n these areas can be repaired by d i r e c t approach. Class 111. These are areas t h a t are accessible during periods of low-power operation of the reactor, such a s the special equipment room and south e l e c t r i c service area, but cannot be entered i f the power i s above 1Mw. The equipment i n these areas can be inspected and repaired without draining the reactor.
Class IV. These are areas t h a t are accessible or habitable a t a l l times, except under the conditions described below i n Class V. These areas include office spaces, control rooms, etc. Class V. The maintenance control room w i l l be the only habitable area during maintenance operations when large, radioactive components are being removed from the reactor c e l l . The r e s t of the MSRE s i t e must be evacuated. This shielded room contains remote control units f o r the cranes and TV cameras. Building
Above grade, Building 7503 i s constructed of s t e e l framing and asbestos cement corrugated s ding with a sheet metal i n t e r i o r f i n sh. Reinforced concrete i s used i n almost a l l cases below the 850-ft elevation.
Floor plans a t the 852- and 84O-ft levels are shown i n Figs. 6 and The general location of equipment i s also shown i n Fig. 6, and an elevation view i s shown i n Fig. 9.
The west half of the building above the 852-ft l e v e l i s about 42 f t wide, 157 ft long, and 33 ft high. This high, or crane, bay area houses the reactor c e l l , drain tank c e l l , coolant-salt penthouse, and most of the auxiliary c e l l s . The eastern half of the building above the 852-ft elevation i s 38 ft wide, 157 Ft long, and about 1 2 ft high. Offices for operational personnel are located along the e a s t wall of the north end. The main cont r o l room (Fig. lo), auxiliary control room, and a room used f o r the data logger, computer, and by the s h i f t supervisor on duty are located across the h a l l on the western side. The large h a l l provides ample space for an observation gallery. Windows behind the control panels enable the operating personnel t o view the top of the reactor c e l l and other operating areas of the high bay. The change rooms are located near the center of the building. The southeastern corner i s used for an instrument shop, instrument stores, and offices f o r instrument department supervisory per-
Most of the western half of the building a t the 84.O-ft l e v e l i s occupied by the reactor c e l l , drain tank c e l l , and auxiliary c e l l s . The