The BGRR was the world’s first reactor built solely to perform scientific research on peaceful uses of the atom.  During its years of operation, it was one of the principal research reactors in the U.S. The BGRR was an air-cooled, graphite-moderated reactor. It was enveloped in a biological shield made of high-density concrete containing scrap iron and limonite.

During reactor operations, filtered outside cooling air was drawn through the reactor pile, then through ductwork where it was cooled and filtered, and eventually exhausted through a 100 meter tall exhaust stack. The primary air-cooling system utilized cooling fans that were located in Building 704 Fan House separate from the Reactor Building (Building 701). Exhaust ducting constructed of reinforced concrete runs in two separate ducts below the ground from the reactor exhaust plenums to the system filters and coolers. Downstream of the filters, ducting rises above the ground and combined into one large duct, which was located on, and was supported by, Building 704. The individual cooling fans took suction through 48 in. diameter ducts that penetrated the building roof and connected at the duct bottom. There was approximately 225 ft. of above‑grade ducting that carried the cooling air to the stack. These ducts were removed as part of a previous BGRR remediation project. Additionally, the below-ground ducts filter, coolers and wetted portions of the primary liner have also been removed.

The BGRR fuel elements were charged and discharged through graphite channel openings on the south pile face.  Unused fuel channels could be used for experimental irradiation purposes. Reactor operations were controlled by the position of 16 control rods that penetrate the reactor horizontally in directions parallel to the diagonals of the reactor base.  The initial fuel of the BGRR was natural uranium (NU) which utilized aluminum fuel elements that were 11 ft. long and contained 33 NU fuel slugs each. During the operation with the NU fuel, there were 28 fuel element failures. These fuel element failures have been document and the fuel channels identified. In 1958, the NU fuel was replaced with enriched uranium (EU) fuel clad with aluminum. Each EU element was 24 in. long.

The reactor was designed for 32 megawatts, with a design-operating limit of 28 megawatts for NU fuel. The reactor normally operated at approximately 20 megawatts with EU. The facility operated from 1950 to 1968. In 1972, defueling and shipment of the fuel to the DOE Savannah River Site was completed. The BGRR complex was described as being in a safe shutdown condition by the U.S. Atomic Energy Commission and became a surplus facility within the DOE complex. From 1977 until 1997, portions of the facility were used as the BNL Science Museum. Figure 1 presents a to-scale map with the approximate site boundary of the BGRR.

Figure 1

Facility Structures

The following provides an overview of the primary BGRR buildings and structures. Figure 1 provides an orientation of the BGRR complex.  Note: The dotted line in Figure 1 defines the border of the BGRR decommissioning scope of work.

Building 701, Reactor Building

Building 701, or the Reactor Building, houses the biological shield and graphite pile. The building is also currently used as administrative offices and to support equipment and systems. The building is a riveted steel-frame structure with a multilayer brick exterior and covers a ground area of approximately 123 ft. by 142 ft. (16,800 ft^2), and is 72 ft. tall. It contains three floor levels plus the canal level below the main floor.

Building 701 has been isolated to the extent possible from Building 703.

Building 702 is the designation for the graphite pile, biological shield, control rods, and associated equipment. Building 702 is entirely enclosed within Building 701.

The graphite structure has the overall dimensions of a 25 ft. cube. It is divided into two halves by a 3⅛ in. (8.0 cm) wide vertical gap. Seventy-five layers of 4 by 4 in. blocks of various lengths up to 45 in. are laid horizontally to form the graphite structure. Figure 2 shows an isometric cutaway view of the graphite structure.

A total of 1368 channels running north and south through the graphite carried the fuel assemblies and cooling air. There are 37 rows of 37 holes each, except for the center hole in the 18^th row, which is occupied by a 12 in. square removable core. There are 30 experimental holes (5 rows of 6 holes each), each 4 in. square, which run horizontally east–west through the graphite structure

Cooling air drawn through roughing filters was pulled through the graphite to remove heat produced by the fuel and cool the graphite. The heated air then flowed out of the reactor into two underground concrete exhaust ducts connected to a plenum, then through in-duct filters and coolers. These concrete air ducts ran aboveground over the roof of Building 704, which enclosed the large primary exhaust fans. The exhaust air then was drawn through these fans and discharged to a 100 meter high exhaust stack.

Figure 2

Biological Shield

The biological shield is 55 ft. long by 37 ft. 6 in. wide by 33 ft. 7 in. high structure that surrounds the pile. The shield consists of an inner layer of steel 6 in. thick (two separate plates in some areas), 4 ft. 3 in. of high-density concrete (with steel punchings and limonite iron ore), and an outer casing on the sides (but not on top) of 3 in. of steel plate. There is also a 12 in. thick by 20 in. wide belt of steel around the gap in the pile. The biological shield was designed to shield personnel working within Building 701 from radiation emitted from the pile. Figure 3 below shows a cut-away diagram of the shield.

Figure 3

Control Rod Drive Mechanisms

There are two assemblies of control rods, rod-drive mechanisms, and support structures: one is on the southeast corner of the reactor, and the other on the southwest corner. During operation, these two mechanisms were operated concurrently for control of the nuclear fissioning process.

Yard

The yard area outside Buildings 701 and 702 is within the BGRR site boundary as shown in the shaded area of Figure 1. It consists of asphalt-paved and dirt areas to the east, south, and west of Building 701.