TREAT Fast-Neutron Hodoscope: Improvements in Time and Mass Resolution of Fuel Motion
The fast-neutron hodoscope at the Transient Reactor Test Facility detects fuel motion in thick opaque capsules during in-core destructive transient tests. Counts from several hundred detectors, each with rates up to a megahertz, are collected at intervals as short as a millisecond for up to tens of seconds. The large amount of data must be decoded, normalized, represented in suitable forms, and analyzed. A computer-controlled magnetic disk data acquisition system has been installed which provides shorter data collection intervals, simplifies decoding, and permits immediate data analysis. Data normalizations and representations have been developed which significantly increase the dynamic range, yield sensitive quantitative indications of fuel mass motion, and render the data intuitively comprehensible. The improved hodoscope system performance level is demonstrated by results from a recent transient test, Pinex-2, which show the quantitative evolution of fuel mass motion from 1515 MW peak reactor power through a 1 MW post-scram radiation level.
Fuel-motion diagnostics and cineradiography
Nuclear and non-nuclear applications of cineradiography are reviewed, with emphasis on diagnostic instrumentation for in-pile transient-reactor safety testing of nuclear fuel motion. The primary instrument for this purpose has been the fast-neutron hodoscope, which has achieved quantitative monitoring of time, location, mass, and velocity of fuel movement under the difficult conditions associated with transient-reactor experiments. Alternative diagnostic devices that have been developed have not matched the capabilities of the hodoscope. Other applications for the fuel-motion diagnostic apparatus are also evolving, including time-integrated radiography and direct time- and space-resolved fuel-pin power monitoring. Although only two reactors are now actively equipped with high-resolution fuel-motion diagnostic systems, studies and tests have been carried out in and for many other reactors.
IN-PILE PHOTOGRAPHIC STUDIES OF EBR-II MARK-I AND FERMI CORE--A SAMPLE MELTDOWN
S>Fast reactor fuei sample meltdown experiments were performed, in the TREAT reactor, with high speed color photography. EBR-II Mark-I and half-length Enrico FerrmCore-A type elements were studied. In addition, preliminary experiments were performed on EBR-II size UO/sub 2/ samples. Sampie conditions at the times of failures, types of failures, and rates of emission of material from the elements were obtained. Course of failure following the initial emission of material is obscured, in the EBR-II sample case, by release of clouds'' of sodium originally present inside the element to effect a thermal bond between fuei and cladding. Photographic results were found to be consistent with previous deductions on sample failures obtained from opaque meltdown experiments. (auth)