Development of vanadium self-powered detectors for power reactor in core application

Vanadium self-powered detectors are commonly used for reactor in-core neutron flux-mapping. When exposed to neutrons, these detectors give a small d.c. signal proportional to the incident neutron flux. The detectors work on neutron activation principle and do not need any polarizing voltage. The fabrication and testing procedures have been standardized. Ten vanadium detectors have been fabricated and will be installed in Kakrapar unit II. A special detector with 5 metre long cable has been developed for testing at Cirus and has been installed in the J rod annulus in a flux of 1013 nv. All these detectors have 2 mm dia 21 cm long emitters, Inconel 600 outer sheath and alumina insulation. They are coupled to 2 mm dia twin-core m.i. cables of 10 and 20 metre length. Tested at Apsara core they showed an average neutron sensitivity of 8 x 10-21 A/nv. (author). 6 refs., 1 fig., 2 tabs