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.
Proton-Recoil Proportional Counter Tests at Treat
A methane filled proton-recoil proportional counter will be used as a fission neutron detector in the fastneutron hodoscope. To provide meaningful fuel-motion information the proportional counter should have: a linear response over a wide range of reactor powers (space charge effects are minimized); a good signal-to-background ratio (the number of high energy neutrons detected must be maximized relative to low energy neutrons, and the gamma ray sensitivity must be kept small); and a detector efficiency for fission neutrons above 1 MeV of approximately 1%. In addition, it is desirable that the detector and the associated amplifier/discriminator be capable of operating at counting rates in excess of 500 kHz. This paper reports on tests that were conducted on several proportional counters at the TREAT reactor. The goal of these tests was the determination of a set of counter parameters that would optimize fuel motion detection. The results show that a proton-recoil proportional counter with a methane gas pressure of 0.5 MPa, a counter diameter of 25.4 mm, an anode wire diameter of 0.0504 mm, and a length of 200 mm will be able to meet most of the hodoscope detector requirements.
Strategies for glass based photonic system integration
There is a clear tendency to integrate more and more opto-electronic and micro-optical components like optical fibers, laser diodes, modulators, isolators, beam-splitting components and micro lenses in also increasingly dense and complex assemblies. The paper will discuss thin glass as a very promising base material for that kind of photonic packaging on interposer and board level including optical interconnection using fibers.