Coded aperture imaging methods for fuel motion measurement

Coded aperture imaging techniques are being applied to fuel motion detection in core disruptive safety experiments in the LMFBR. Its potential for time resolved broad source X-radiography is being investigated, and for the Sandia Annular Core Pulse Reactor (ACPR) a system is being developed to image moving fuel with approximately 1 mm spatial resolution at about 104 frames/sec. Thus far in the investigations of these systems a number of feasibility milestones have been reached. (1) A fuel pin shaped object has been imaged with 2 mm resolution using a large area 10 MeV electron bremstrahlung spectrum and coded source X-radiography. (2) An extended 252Cf fission gamma ray source has been imaged with film through 1.27 cm of steel (simulating reactor containment). (3) The 252Cf extended source has been imaged through 1.27 cm of steel with X-ray image intensifier amplification. (4) Collimation and shielding tests indicate that at ACPR it should be possible to obtain adequate signal to noise at the detector when the fuel is observed through a slot in the core