Neutron Imaging Beamline for Advanced Imaging Applications at Dhruva reactor, India

Neutron radiography has long been used in various scientific investigations and industrial applications that require thermal neutrons for characterization. Different kinds of sources such as radioactive sources, portable and accelerator based neutron generators and nuclear reactors can be used to provide thermal beam of neutrons suited for neutron radiography. Among the different varieties of neutron sources, reactors offer the largest steady state thermal neutron flux. In this paper, we present design and development of a state-of-art neutron imaging beamline at Dhruva reactor for advanced neutron imaging applications such as tomography and phase contrast imaging. This beam line has been developed on a core facing port HS-3018 (diameter about 380 mm) of the reactor with a specially designed collimator to maximize neutron to gamma ratio. The maximum beam size of neutrons has been restricted to ~ 140 mm diameter at the sample position. The collimator has been designed in such a way that radiography, tomography or phase contrast imaging studies can be performed on the same beamline. The shielding hutch and motorized shielding door of the beamline have been designed using modular and easy to assemble blocks of borated polythene and lead. A cadmium ratio of ~ 250 with L/D ratio of 160 and thermal neutron flux of ~ 4x10 n/cm/s at the sample position has been measured. In this work, different aspects of the beamline design such as collimator, shielding, sample manipulator, digital imaging system are described. Results of some preliminary nondestructive radiography experiments on fuel pins, zirconium hydride blisters, locomotive parts etc. are also presented.