based on the hydrostatic loading of the vessel, and its weight under static condition, result in a maximum stress on the vessel with a thickness of 2.5 cm to be 1.4 ksi, which is well below the 3.5 ksi value that already includes most of the factor of safety in arriving at the number (see Fig. 4.1 showing the vessel and the stress distribution).
Fig. 4.1. (a) Reactor vessel and (b) reactor vessel stress distribution under load.
The reactor vessel is attached to the external load-bearing concrete structure by support brackets that allow for lateral motion that may occur during operation, installation, or removal.7 By using Lubrite plate and an interstitial gap between the anchoring bolts that attach the reactor vessel and concrete, small lateral motion can be accommodated without transmitting large forces. Similar design is incorporated on the bolts that make the vertical support connection. The reactor will be designed to account for operational basis earthquake at the deployment site. The overall reactor design philosophy is to make the design as modular as possible. All components of the reactor are introduced from the top (Fig. 4.2). The IHX and DRACS heat exchangers, the reactor core, the reflector, and the control rods have flanged entry points at the top of the reactor. This series of flanges in three concentric circles interlock to form the top closure of the reactor vessel. An outermost top closure flange rests on top of the reactor vessel flange which, in turn, rests on the supporting reinforced concrete pad (Figs. 4.2 and 4.3). This top closure flange supports the weight of all the reactor vessel internals and transfers this load to the surrounding reactor vessel flange. The core reflector, the PHXs, the DRACS heat exchangers, and the downcomer “skirt” that constitutes the inner boundary of the annular downcomer are all suspended directly from this closure flange. The central closure plate or “core bonnet” supports the reactor core and transfers the resulting load to the top closure flange. The control rods are inserted through this central closure plate but have the ability to be raised or lowered independently of the central plate. 4.3 4.3.1
REACTOR FUEL AND CORE Introduction
Three different SmAHTR fuel compact mechanical configurations have been evaluated: cylindrical, annular, and plate form. The SmAHTR design could also accommodate a pebble-bed-type core, although this core form has not yet been evaluated.
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