David P. Lieb

Principle of operation of the thermal energy analyzer for the trace analysis of volatile and non-volatile N-nitroso compounds

The theoretical basis for the thermal energy analyzer is discussed. Using the principles outlined, the feasibility of selectivity detecting mug/kg levels of volatile and non-volatile N-nitroso compounds is established.

Liquid Chromatograph Detector for Trace Analysis of Non-Volatile N-Nitroso Compounds

Abstract A Thermal Energy Analyzer has been interfaced to a high performance liquid chromatograph. The hplc-TEA system can be used for analysis of nanogram amounts of N-nitroso compounds.

Radioisotope Thermionic Converters for Space Applications

The recent history of radioisotope thermionics is reviewed, with emphasis on the U.S. programs, and the prospects for the future are assessed. In radioisotope thermionic converters the emitter heat is generated by the decay of a radioactive isotope. The thermionic converter emitter is mounted directly on a capsule containing the isotope. The rest of the capsule is generally insulated to reduce thermal loss. The development of isotope-fueled thermionic power systems for space application has been pursued since the late 1960s. The U.S. effort was concentrated on modular systems with alpha emitters as the isotope heat source. In the SNAP-13 program, the heat sources were Cerium isotopes and each module produced about 100 watts. The converters were planar diodes and the capsule was insulated with Multi-Foil insulation. Unlike nuclear reactors, the isotope heat source cannot be turned off. Thus the isotope must be handled in a hot cell, and furthermore, once the isotope is inserted into the thermionic converter, the refractory metals must be protected from oxidation with either vacuum or inert atmosphere. With the advent of DC-to-DC converters which operate with low input voltage and high efficiency, radioisotope thermionic converters are attractive.

Analysis of fast gas-chromatographic signals with artificial neural systems

Thermedics Detections explosive detectors use fast gas chromatograph analyzers to identify key components in explosives. The analyzer produces a time series of measurements which identify mobility through the columns. This time series of measurements appears as a spectrum of values with peaks corresponding to certain substances, explosive and otherwise. The analytical task of the system is to isolate the signal peaks from the detection noise, background, pedestals and peaks from extraneous substances. A uniquely modified back- propagation neural network (non-linear adaptive filter) was developed to perform the signal analysis. The unique feature of this signal analysis system was the analysis to train the network to provide only signal amplitudes but, additionally, a measure of confidence in the derived amplitudes with respect to the simulated interferents, random noise and peak time jitter included in the training. Alarms can then be set according to confidence of detection.

Design of a planar thermionic converter to measure the effect of diffusion of uranium oxide on performance

A plane parallel variable‐spaced research converter was designed to investigate the effect of diffusion of uranium oxide fuel through the tungsten emitter. This work is part of the Thermionic Fuel Element (TFE) verification program. In the TFE program the cylindrical emitter is made of Chemical Vapor Deposited (CVD) tungsten from tungsten fluoride, which is over coated with CVD tungsten, from the chloride, resulting in a 〈110〉 crystal orientation. The planar converter has a similar emitter construction. This paper describes the design and preliminary testing of this converter.

Prediction of the start‐up characteristics of thermionic converter in a STAR‐C reactor

The design for a Space Thermionic Advanced Reactor‐Compact (STAR‐C) power system with a baseline power of 40 kW(e) consisted of 1230 parallel planar thermionic converters surrounding a space reactor system. The converters were similar to the Solar Energy Thermionic (SET) converters. The collectors were coupled to sodium‐filled heat pipes which rejected heat to heat pipe radiators. A cesium intercalated graphite reservior in each converter supplied cesium vapor. A computer thermal model was used to predict the start‐up characteristics of a converter in the STAR‐C system. During start‐up, the reactor heat was radiated to the emitter. Heat was radiated across the cesium gap to the collector and conducted to the cesium‐graphite reservoir located in the niobium of the collector heat pipe. Waste heat was removed by the heat pipe to the radiators. A transient, finite‐element computer‐model of the thermionic converter was developed to simulate the behavior of the STAR‐C converter. The subject of this paper is the...

Modeling of a cesium‐graphite reservoir critical component experiment for S‐prime

The S‐PRIME (Space Power Reactor, In‐core, Multi‐cell, Evolutionary) program has identified the cesium reservoir as a critical component requiring experimental validation. A test vehicle to measure the response of the cesium‐intercalated graphite reservoir has been designed. The geometric design of the test device parallels that of the in‐core, fueled device to the extent possible. Heat loss is through a gas gap to a water‐cooled jacket rather than to a molten metal loop. Auxiliary heaters were added to the collector and cesium reservoir heat sink region in order to provide flexibility to achieve the wide range of temperatures proscribed in the test protocol. The thermal finite difference computer model developed for the nuclear device was adapted to reflect the required modifications in the design of the experimental apparatus.This computer model indicated that the single test device is capable of simulating both types of cesium reservoirs required in the S‐PRIME system. The nominal operating conditions ...