EVALUATION OF AN IN-LINE NEUTRON COINCIDENCE COUNTER

A neutron coincidence counter installed at the Rocky Flats Plutonium Recovery and Recycling Facility is designed to measure samples containing up to two kilograms of plutonium. The IRT Corporation HEC-100 Electronics and Controller is used to determine correlated neutron events detected by a box-shaped thermal neutron detector system. A FORTRAN handler was developed to handle communications between the HEC-100 controller and a Digital Equipment Corporation PDF 11/23 microcomputer running the RSX-11M operating system. Approximately 1.5 percent of system stability measurements where significantly degraded by electronic noise. A statistical algorithm was developed to determine if a single measurement has been significantly degraded by noise. Count rates of a point source varied approximately 15 percent over the 190 mm diameter surface of the sample container. The largest source of measurement error was caused by multiplication and geometry effects. Calibration techniques and results are discussed.