Thomas V. Congedo

Diagnostics and modeling of RF discharge dissociation in N/sub 2/O

Measurements were made of the RF discharge dissociation of N/sub 2/O in a parallel-plate reactor by downstream mass spectrometry using a wide range of gas flows and powers at 10 kHz and 13.56 MHz. The results show that the mass 44 signal (N/sub 2/O/sup +/), which is a measure of the amount of undissociated N/sub 2/O, is a function of the discharge input energy per N/sub 2/O molecule (eV/N/sub 2/O). A plug flow, rate equation model of the discharge was used to predict the experimental dissociation rates. A DC Monte Carlo simulation was used to calculate rate coefficients for electron-impact neutral dissociation, ionization, and dissociative ionization. The rate equation model also includes reactions among the dissociation products of N/sub 2/O and species which are synthesized in the discharge, as well as neural and electron-ion recombination at the electrodes. The model predictions identify the major reaction pathways and the sensitivities of the results to the rate coefficient values used. >

Detection Limits of a Laboratory Pulsed Gamma Neutron Activation Analysis System for the Nondestructive Assay of Mercury, Cadmium, and Lead

Detection of Hg, Cd, and Pb within concrete matrices located in 8-gal drums was successfully demonstrated using a pulsed gamma neutron activation analysis system. Real-time assays of 600 s led to the detection of these metals at concentration levels ranging, in parts per million (ppm) by weight, from 487 to 19,820 for Hg, 485 to 8181 for Cd, and 9927 to 19,950 for Pb. The measurements of Hg and Cd relied on the observation of thermal neutron-induced prompt gamma rays, whereas the Pb measurements relied on the observation of decay gamma rays from {sup 207m}Pb, a product of fast neutron-induced reactions in Pb. The projected lower limits of detection of the current system for a 600-s run are 15, 170, and 8600 ppm for Cd, Hg, and Pb, respectively. Up to a one-order magnitude of improvement in sensitivity is anticipated through the enhancement of the system`s detector and neutron source. The results obtained confirm the potential of prompt and decay gamma neutron activation analysis as an effective method of the nondestructive analysis of hazardous metals in mixed-waste drums.

Pulsed neutron interrogation for detection of concealed special nuclear materials

A new neutron interrogation technique for detection of concealed Special Nuclear Material (SNM) is described. This technique is a combination of timing techniques from pulsed prompt gamma neutron activation analysis with silicon carbide (SiC) semiconductor fast neutron detector technology. SiC detectors are a new class of radiation detectors that are ultra-fast and capable of processing high count rates. SiC detectors can operate during and within nanoseconds of the end of an intense neutron pulse, providing the ability to detect the prompt neutron emissions from fission events produced by the neutrons in concealed SNM on a much faster pulsing time scale than has been achieved by other techniques. Neutron-induced fission neutrons in 235U have been observed in the time intervals between pulses of 14-MeV neutrons from a deuterium-tritium electronic neutron generator. Initial measurements have emphasized the detection of SNM using thermal-neutron induced fission. Neutron pulsing and time-sequenced neutron counts were carried out on a hundreds of microseconds time scale, enabling the observation of prompt fission neutrons induced by the die-away of thermal neutrons following the 14-MeV pulse. A discussion of pulsed prompt-neutron measurements and of SiC detectors as well as initial measurement results will be presented.

Experimental verification of modeling results for a PGNAA system for nondestructive assay of RCRA metals in drums

The use of pulsed gamma neutron activation analysis (PGNAA) for the nondestructive assay of mercury, cadmium and lead in a concrete matrix has been demonstrated. Calculations have also been performed to study interference with PGNAA detection sensitivity resulting from the presence of 238U, 235U, and 239Pu at levels expected in mixed waste. Analyses based on transport calculations examined the effects of these nuclides on neutron kinetics, and the contribution from the capture, fission and decay gamma-rays emitted by the nuclides to the gamma-ray spectrum. These calculations predicted insignificant effects on the systems detection limits (115, 9 and 4400 ppm for Hg, Cd and Pb, respectively, for a 2000 s assay). This paper describes verification measurements recently conducted using samples of 235U and 231U in the test drum geometry, which have provided experimental confirmation of the modeling results.

Technology Road Mapping to Guide Development Planning

For the past five years, Westinghouse Electric Company, PLC, has made ever increasing use of Technology Road Mapping, to direct company development efforts to achieve maximum benefits for our customers and ourselves. Comprised of business units in Nuclear Fuels, Nuclear Services and Nuclear Power Plants, including domestic and international business segments, Westinghouse must pay particular attention to coordinating development to satisfy the diverse needs of our growing international customer base. We must develop products which both benefit the individual Business Unit customer base, and which create synergy to produce the best possible offerings to the broader marketplace. The knowledge we gain through customer contacts and direct customer participation provides the basis from which we develop the Technology Road Map. This Road Map development process can be compared to painting a picture, where the background colors and features correspond to drivers related to the Customer and the prevailing features of the market environment. The subsequent layers of detail include broad Technical Objectives and then specific Technical Goals which will support achieving those Objectives. The process is described in detail, and examples are provided.Copyright