Subcritical Graphite Reactor Facility

The graphite sub-critical reactor facility (GSR) was constructed at Penn State in 1958 as part of a graduate student project. The pile was intended to expand upon the research reactor facility’s capabilities to educate students in the burgeoning field of nuclear engineering. Since then, it has been used continuously for 55 years as part of the reactor physics curriculum. Currently the GSR is used as the basis for teaching subcritical physics to approximately 100 undergraduate students each year. Additionally, the facility is used by researchers who require a well-thermalized neutron field for their experiments. Recently, the facility has been used to develop sensitive neutron detectors for nuclear safeguards purposes. The inherent simplicity and flexibility of the GSR ensures that it will be useful for many years to come. The GSR is constructed of several hundred blocks of reactor-grade graphite and the entire facility is clad in cadmium sheeting covered in aluminum. The cadmium covers shield the users from the neutron flux generated by the pile. The facility can be used as a sigma pile by inserting from one to five one curie plutonium-beryllium neutron sources at various points. It can also become a subcritical reactor by replacing some of the graphite with natural uranium rods. The fuel was donated by the Atomic Energy Commission in 1958. The fuel can be configured in four analyzed loadings for different experiments. The maximum flux in the pile is approximately 104 n/cm2s and the maximum keff is approximately 0.7. By removing graphite, various measurements can be performed with neutron detectors and activation foils.
Penn State Graphite Reactor (cadmium cover partially removed)


The Radiation Science & Engineering Center (RSEC) was established to manage Penn State's comprehensive nuclear research facilities, including the Breazeale Nuclear Reactor, Gamma Irradiation Facility, Radioactive sources and Radiation measurement resources. The RSEC provides safe nuclear analytical and testing facilities in support of the research and education activities of faculty, staff, and students at Penn State.

Radiation Science & Engineering Center

101 Breazeale Nuclear Reactor

The Pennsylvania State University

University Park, PA 16802-4710

Phone: 814-865-6351