A rapidly pulsed triga reactor for neutron radiography

Abstract Many TRIGAR reactors are used as the source of thermal neutrons for neutron radiography. The majority of these applications involve steady state operation of the reactor which provides sufficient fluence for radiographic plates or real-time imaging. Many real-time applications would benefit from substantially increased fluences in a single frame (1/30 sec) or in a few frames if the number is limited by motion of the NR target. A pulsed TRIGA reactor can be useful in such cases. The low repetition rate for the standard pulsed TRIGA reactor (∽6/hour) has seriously limited this application. owever, the modern control rod drives and related digital instrumentation have made it possible to produce 60MW pulses at the rate of 1 at least every 5 to 6 seconds (∽10/ min or at least 100 times more frequent). The increased fluence in each of such pulses provides the capability to use electronic imaging with substantially increased resolution and signal-to-noise in a single frame. As an example. a 250kw steady state TRIGA reactor with L/D= 100 can provide a NR fiuence of about 1.8 x 109 n/cm2 in 3 minutes i.e., with 45000 kw sec). A single frame of an electronic imaging system receives a fiuence from the same reactor corresponding to about 8.3 kw-sec, A TRIGA reactor pulsed every 6 seconds to 60MW will give a fluence in a single pulse corresponding to about 1800kw sec. This will allow a single frame to receive the fluence corresponding to the integration of more than 200 frames from the referenced steady state operation but without the electronic noise that accompanies extended frame integration. At least two areas of improved neutron radiography can result from use of the proposed rapidly pulsed TRIGA reactor. Not only would there be significant improvements in spatial and temporal resolution for radioscopy of moving NR objects but real-time cold neutron radiography would become more easily achievable.