The reactor core area from the top of the pressure tank. The reactor core (right side of the box) comprises a uranium-fueled section (a center array of three hole by nine holes for fuel control rods) surrounded by reflector material or experiments, to compose the complete four-by-eleven hole core array. The fueled core contains twenty-two stationary rods and five movable cadmium and fuel control rods. The reflector material on three sides includes two cadmium and beryllium movable regulating rods, three similar shim safety rods, and twelve fixed reflector plugs or experiments. The fueled core housing has reflector plates on the right and left sides and aluminum end-plates. Along side the fueled section is a large four-by-eight hole reflector section(left side of the box), which provides facilities for inserting up to thirty-two experiments, one for each hole. The whole core structure sits on a stainless steel rack in the stainless-steel-lined pressure vessel (nine feet in diameter by thirty-one feet high). Three thermal shields are visible (the three rings) around the core. Two large vertical test holes run next to the end of the cores. One large tube runs through the large reflector section and another runs next to the fueled section. Three smaller beam tubes about the right side of the core and three others are on the reflector side (left).