Reconfiguration of the Rensselaer Polytechnic Institute Critical Facility to Lower Critical Mass

Since 1963, the Rensselaer Polytechnic Institute’s (RPI) critical facility has contained 6.01 kg of ²³⁵U, a load in excess of the 5-kg ²³⁵U formula quantity delimiting the stringent physical protection requirements of the Nuclear Regulatory Commission’s Category I. Because these requirements would be prohibitively expensive for RPI, a number of alternatives were examined including decommissioning. A combined experimental and analytical program has succeeded in reconfiguring the core to loading below the formula quantity. Core physics parameters are within the technical specifications as before, and the experimental utility of the core is preserved in most aspects. The analysis used conventional pressurized water reactor industry nodal methods and can be regarded as providing experimental tests on these methods.