The design of the APRF is a direct outgrowth of projected user requirements. Thus the reactor can be used both for high dose irradiations of small objects, as a point source for radiation detector studies, and irradiation of bulk objects. The former requirement led to the incorporation of a 1½-inch OD “glory hole” running through the center of the core, and providing a fast neutron fluence of about 9 × 10¹⁴ neutrons per square centimeter per pulse. The latter two requirements have resulted in the design of a large volume, low-radiation backscatter Reactor Building. Provision is made for moving the reactor both within the Reactor Building and to an outdoor test site at heights variable up to 44 feet above ground by means of a mechanical device called the reactor transporter. The reactor is also capable of intermittent steady state operation in the kilowatt range for classes of experiments requiring this mode of operation. [Illustration] [Illustration] [Illustration] The Facility The APRF is located on the military reservation of Aberdeen Proving Ground (APG), in southeastern Harford County, Maryland. The Reactor Building is at the center of the facility. This building is a windowless, circular structure with aluminum siding. Inside, the building is 100 feet in diameter and 65 feet high. There is a roll-up door in the south wall for the passage of the reactor transporter to the outdoor test site and another in the west wall for the access of vehicles to the building. A shielded stairway and maze provides access from the underground Control Building. This concrete structure provides radiological shielding for the personnel and controls associated with the operation of the reactor and the conduct of experiments. The area within a ~450-yard radius of the Reactor Building constitutes the APRF high-radiation area defined by a 10-foot anti-personnel fence. This high-radiation area is in turn surrounded by a nearly concentric restricted area defined at its outer boundary by a barbed wire warning fence at a radius of ~1500 yards from the Reactor Building. The Laboratory Building, located at the periphery of the restricted area, houses the administrative and support personnel for the APRF. Access to APRF is controlled at this point. [Illustration: APRF Reactor Core Assembly] [Illustration] The Reactor The reactor, (APRFR), is designed for both self-limited, super-prompt-critical pulse operation and steady state operation. The maximum available pulse has a yield of ~2.1 × 10¹⁷ fissions, while steady state operation is limited to about 10 kilowatts by the reactor core cooling system and activation of the core. [Illustration: High Yield Prompt Pulse Shape]