Measurement of Fast Neutron Spectrum and Flux in Central Thimble of TRIGA MARK-II Reactor

The measurements of the fast neutron flux and its spectrum have been carried out by the threshold detectors in the central thimble of TRIGA Mark-II reactor operating at 250 KW. The following reactions have been employed for these measurements, viz : Ni (n, p) Co ； (n, p) Na ； (n, ) Na . From the activation data the fast neutron spectrum were calculated by CDC-3600 computer making use of two semi-empirical methods. It has been verified that the validity of assumption of a fission spectrum in the central thimble exists only above 1 to 2 Mev energy level. With this spectrum, a fast neutron flux in the range of 1 10 n/-sec above the energy of 2.6 Mev was observed in the central thimble of TRIGA MARK-II reactor.