40 research outputs found
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Solid state track recorder measurements in the poolside critical assembly
Fission rate measurements using solid state track recorders (SSTR) have been performed at the PCA. A schematic representation of a cross-section of the PCA is shown. Fission rates were measured in the pressure vessel simulator at the T/4, T/2 and 3T/4 positions and in the void box (VB). SSTR measurements were carried out with /sup 232/Th, /sup 235/U (bare and cadmium covered), /sup 238/U and /sup 237/Np fissionable deposits. Midplane only measurements were carried out for /sup 235/U and /sup 237/Np, while 5 axial locations at 1/4T and 1/2T and 3 axial locations at 3/4T and in the VB were sampled for /sup 232/Th and /sup 238/U. The HEDL SSTR fission rate measurements reported herein for both configurations together with NBS and CEN/SCK fission chamber measurements will be used to establish absolute and relative fission reaction rates, and ratios for the PCA pressure vessel Benchmark Facility
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Buffon needle method of track counting
A new technique of quantitative track counting, the Buffon needle method, is advanced. It is based on random sampling of the solid state track recorder (SSTR) surface. This new method extends quantitative track scanning to track densities well up into the track pile-up regime. It is shown that the Buffon needle method possesses a reduced dependence upon both track density nonuniformity and track size distribution. Sources of experimental error arising in the Buffon needle method are assessed. The validity of the Buffon needle method is demonstrated down to at least the 10% uncertainty level (1sigma) by manual sampling of high fission track density mica SSTR observed with scanning electron microscopy
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Selected etching and annealing properties of Brazilian quartz crystals for solid state track recorder applications
The etching and annealing properties of Brazilian quartz crystals are under investigation to determine their suitability for use as solid state track recorders (SSTR) and damage monitors in nuclear reactor environments, where temperatures and neutron fluences are high. Observer objectivity in counting fission tracks has been established at the 1 to 2% level, and a method of standardizing chemical etching from one sample of quartz to another has been found. A method has also been found to make corrections for track loss due to thermal annealing in terms of the effect of the annealing on the track size in the direction of maximum bulk etch rate parallel to the 100 plane, provided the fractional track loss does not exceed approx. 40%
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Solid State Track Recorder applications in United States nuclear reactor energy programs
The domain of Solid State Track Recorder (SSTR) applications in United States nuclear reactor energy programs extends from the harsh high temperature environments found in high power reactor cores to very low flux environments arising in out-of-core locations, critical assemblies, or away from reactors (AFR) experiments. The neutron energy region arising in these applications is very broad, covering more than eight orders of magnitude from thermal up to fusion energies. The range of neutron flux/fluence intensity is even greater, extending over more than thirteen orders of magnitude. As a consequence, use of a variety of SSTR is entailed in US nuclear reactor energy programs
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Applications of solid state track recorder neutron dosimetry for fuel debris location in the Three Mile Island Unit 2 reactor coolant system
As a result of the Three Mile Island Unit (TMI-2) accident on March 28, 1979, fuel debris was dispersed into the primary coolant and auxilliary systems of the reactor. The presence of fuel may be traced by using the neutron activity which is associated with the burn-in of higher actinides (about 300 neutrons/sec/kgU). Solid state track recorder (SSTR) neutron dosimetry is the most sensitive technique for measuring low neutron fluxes. Hence, neutron dosimetry is being performed at TMI-2 to locate fuel debris and subsequently aid the reactor recovery effort. Herein, the results of a scoping measurement on the fuel content of TMI-2 Makeup Demineralizer A are reported along with relevant calibration measurements. The total amount of fuel estimated in Demineralizer A, 1.7 kg, corresponds to a total neutron source of about 400 neutrons/sec. At the detector positions, data were obtained with neutron fluxes as low as 10/sup -3/ n/sec/cm/sup 2/, demonstrating the extreme sensitivity of the SSTR method