NIST maintains the Californium Neutron irradiation Facility (CNIF), which is an exposure facility providing fast neutrons for irradiations requiring high neutron fluence. The facility also provides Cf-252 and monoenergetic neutrons that can be used for detector calibration and testing and other similar activities.
A high-activity Cf-252 source is housed in a large (approximately 15 m x 10 m x 10 m high) room with concrete walls, floor, and ceiling (see photograph) at a depth of 10 meters-water-equivalent. In addition, there are two monoenergetic neutron generators for 2.5 MeV and 14 MeV neutrons that produce neutron emission rates of order 106/s and 108/s, respectively. Inside the concrete is a 5.4 cm thick shell (5.3 m x 5.3 m x 5.9 m high) of anhydrous borax, which prevents neutrons scattered by the concrete from returning to the source. Typical irradiations include detector calibrations, neutron transport studies, sample activation experiments, electronic damage studies, and other special tests requiring high neutron fluence and a low-room-scatter environment. Calibrated fission monitors allow neutron fluence to be determined to high accuracy and can be traceable to NBS-1. Closed-circuit TV coverage of the experimental area is provided, and experiments requiring active monitoring may be reached with approximately 25 m of cable. Recent customers include the Georgetown University Medical Center, Sandia National Laboratory, and various internal NIST projects. NIST provides reference high-intensity Cf-252 neutron exposures in support of US nuclear programs.