Micro-pocket fission detectors (MPFD) for in-core neutron flux monitoring

Abstract: Micro-pocket fission detectors (MPFD) have been fabricated and tested as in-core flux monitors in the 250kW TRIGA nuclear reactor at Kansas State University. The prototype devices have been coated with a natural uranyl-nitrate to provide a neutron reactive coating. The devices are composed of alumina substrates sealed together to form a miniature gas pocket 3mm in diameter and 1mm wide. The devices are radiation hard and can operate in pulse mode in a neutron flux exceeding 1012 cm−2 s−1. Placed in the central thimble of the reactor core, the MPFDs have shown count rate linearity from low to high power. Dead time losses become apparent at power levels exceeding 100kW, yet are still low enough to allow for pulse mode operation. [Copyright &y& Elsevier]