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.
Image Restoration to Increase Resolution of the Fast-Neutron Hodoscope
The fast-neutron hodoscope is a cineradiographic device that monitors fuel motion within thick opaque test capsules during power transients at the Transient Reactor Test Facility reactor which simulate LM FBR accident conditions. By means of a collimator and a detector array, emissive neutron radiographic digital data is collected in time-resolved and time-integrated (scan) modes. The data is digitally reconstructed into radiographic images and used directly for quantitative analysis. Spatial resolution is adequate in most cases (due in part to fuel-motion correlation), but is marginal for a few experiments. To enhance the resolution of existing collimators, hardware and software techniques are being applied, including collimator repositioning, decreasing scan increments, noise reduction, and fitting procedures involving fuel-motion models and deconvolution. Significant improvements in spatial resolution have been obtained.
Proposed beam diagnostics instrumentation for the LANSCE refurbishment project
Presently, the Los Alamos National Laboratory is in the process of planning a refurbishment of various subsystems within its Los Alamos Neutron Science Center accelerator facility. A part of this LANSCE facility refurbishment will include some replacement of and improvement to existing older beam-diagnostics instrumentation. While plans are still being discussed, some instrumentation that is under improvement or replacement consideration are beam phase and position measurements within the 805-MHz side-coupled cavity linac, slow wire profile measurements, typically known as wire scanners, and possibly additional installation of fast ionization-chamber loss monitors. This paper will briefly describe the requirements for these beam measurements, what we have done thus far to answer these requirements, and some of the technical issues related to the implementation of the instrumentation.