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. The two recent irradiations were performed for the Georgetown University Medical Center and Sandia National Laboratory. NIST provides reference high-intensity Cf-252 neutron exposures in support of US nuclear programs.
NIST maintains the Californium Neutron Irradiation Facility (CNIF), which is an exposure facility providing fast neutrons for irradiations requiring high neutron fluence.
International Key Comparison of Neutron Fluence Measurements in Monoenergetic Neutron Fields CCRI(III)-K11
Created February 09, 2011, Updated September 21, 2016