James P. McNeece

The status of automated nuclear scanning systems

Abstract Present day minicomputers and microprocessors enable a range of automation, from partial to total, of tasks once thought beyond approach. The status of three computer controlled systems for quantitative track measurements is reviewed. Two systems, the Hanford optical track scanner (HOTS) and an automated scanning electron microscope (ASEM) are used for scanning solid state track recorders (SSTR). The third system, the emulsion scanning processor (ESP), is an interactive system used to measure the length of proton tracks in nuclear research emulsions (NRE). Current limitations of these systems for quantitative track scanning are presented. Experimental uncertainties attained with these computer controlled systems are described using results obtained from reactor neutron dosimetry.

Interactive system for scanning tracks in nuclear research emulsions

A computer‐based interactive system has been developed and successfully used for scanning proton‐recoil tracks in nuclear research emulsions. To our knowledge, this system is the first truly interactive system developed and used for emulsion scanning. Interfaces have been developed between the three fundamental interacting entities, namely man, microscope, and computer. Computer codes can be developed for different applications, thereby providing wide flexibility and versatility. Use of this system for neutron metrology is described. Differential neutron spectrometry as well as integral neutron dosimetry have been carried out in both 4π and unidirectional neutron fields. Results are presented which quantify the accuracy attained with this system for each of these different neutron measurement emulsion techniques. This system provides a substantial advance in the state‐of‐the‐art of emulsion scanning in terms of both accuracy and cost effectiveness. The ability to store, in computer memory, all relevant em...

Characterization of Fuel Distribution in the Three Mile Island Unit 2 (TMI-2) Reactor System by Neutron and Gamma-Ray Dosimetry

Neutron and gamma-ray dosimetry are being used for nondestructive assessment of the fuel distribution throughout the Three Mile Island Unit 2 (TMI-2) reactor core region and primary cooling system. The fuel content of TMI-2 makeup and purification Demineralizer A has been quantified with Si(Li) continuous gamma-ray spectrometry and solid-state track recorder (SSTR) neutron dosimetry. Results obtained from these gamma- ray and neutron dosimetry experiments were 1.3 ± 0.6 kg and 1.7 ± 0.6 kg, respectively, for the fuel content of TMI-2 Demineralizer A.

Automatic scanning of solid state track recorders: Calibration

Abstract A computer controlled microscope has been upgraded for the automatic scanning of solid- state track recorders. The system has been calibrated by using Muscovite mica exposed in direct contact with thin deposits of 2 4 2 Pu on stainless steel backing. These deposits were uniform in density and of accurately known mass. Calibrations were carried out for exposure ranging from 3.6 × 10 4 to 6.8 × 10 5 fissions cm -2 . Repeated scans generally give a reproducibility ∼2%. The scanning time for an area of 1.3 cm 2 varies from 30 min for low track densities up to a few hours for high track densities. Further upgrading of the system to increase speed and accuracy is planned.

Automated scanning of solid state track recorders: Computer controlled microscope

Abstract A computer controlled microscope for rapid processing of solid state nuclear track recorders is described. Specimen stage movements and autofocusing are controlled by stepping motors. A videcon camera and high speed digitizer produce the digital image for computer analysis. Processing times for a 1.3 cm2 track recorder range from 45 to 150 min depending on track density. Track counting accuracy of 2 – 3 percent is readily achievable with the automated system.

Progress in automated scanning electron microscopy for track counting

Abstract A computer automated scanning electron microscope system is under development for scanning tracks in solid state track recorders (SSTR). Basic elements that comprise the current system are delineated and system operation described. New design features to provide enhanced operation of the system are also presented.

Advances in Continuous Gamma-Ray Spectrometry and Applications

Recent advances and applications in continuous Compton recoil gamma-ray spectrometry are described. Applications of continuous gamma-ray spectrometry are presented for: 1 1) Characterization of light water reactor (LWR) pressure vessel (PV) environments. 2 2) Assessment of fuel distributions for Three Mile Island Unit 2 (TMI-2) reactor recovery. 3 3) Measurement of LWR-PV-neutron exposure. The latest improvements attained with the Janus probe, a special in-situ configuration of Si(Li) detectors, are presented. The status of current efforts to extend the domain af applicability of this method beyond 3 MeV is discussed with emphasis on recent work carried out with Si (Li) detectors of much larger volume.

Nondestructive Determination of Reactor Pressure Vessel Neutron Exposure by Continuous Gamma-Ray Spectrometry

A nondestructive method for determinating reactor pressure vessel (RPV) neutron exposure is advanced. It is based on the observation of characteristic gamma-rays emitted by activation products in the RPV with a unique continuous gamma-ray spectrometer. This spectrometer views the RPV through appropriate collimators to determine the absolute emission rate of these characteristic gamma-rays, thereby ascertaining the absolute activity of given activation products in the RPV. These data can then be used to deduce the spatial and angular dependence of neutron exposure at regions of interest in the RPV. In addition, this method can be used to determine the concentrations of different constituents in the RPV by measuring the absolute flux of characteristic gamma-rays from radioactivity induced in these constituents through neutron exposure. Since copper concentration may be a crucial variable in radiation- induced embrittlement of RPVs, the ability of this method to measure copper concentrations in base metal and weldments is examined.

Fast-neutron fluence spectra and integral reaction rates determined with nuclear research emulsions

Nuclear research emulsions are in use at the Westinghouse Hanford Company to characterize various neutron fields. Track measurements are accomplished with the use of an optical microscope interfaced with a computer. Whereas scanning by a person is still necessary, data is recorded in such a way that it is subject to many types of analyses. Examples given are the measurement of the spectrum-fluence of neutrons emitted in the spontaneous fission of /sup 252/C/sub f/, the measurement of the spectrum-fluence of neutrons inside the core of a breeder reactor, and the measurement of two types of integral reaction rates in a reactor environment.