Scott Greenway

Radiation Stability of Nafion Membranes Used for Isotope Separation by Proton Exchange Membrane Electrolysis

Abstract Proton exchange membrane electrolyzers (PEMEs) have potential interest for use for hydrogen isotope separation from water. In order for PEMEs to be fully utilized, more information is needed on the stability of Nafion when exposed to radiation. This work examines Nafion 117 under varying total dosage and dose rate and in water or air. Analytical tools, such as infrared spectroscopy, ion exchange capacity, dynamic mechanical analysis, and total inorganic carbon-total organic carbon (TIC-TOC) were used to characterize the exposed membranes. The water from saturated membranes was analyzed by fluoride and sulfate emissions and TIC-TOC, which provided important data on the stability of the membranes during radiation exposure.

The Effect of Low Concentrations of Tetrachloroethylene on the Performance of PEM Fuel Cells

Polymer electrolyte membrane (PEM) fuel cells use components that are susceptible to contaminants in the fuel stream. To ensure fuel quality, standards are being set to regulate the amount of impurities allowable in fuel. The present study investigates the effect of chlorinated impurities on fuel cell systems using tetrachloroethylene (PCE) as a model compound for cleaning and degreasing agents. Concentrations between 0.05 parts per million (ppm) and 30 ppm were studied. We show how PCE causes rapid drop in cell performances for all concentrations including 0.05 ppm. At concentrations of 1 and 0.05 ppm, PCE poisoned the cell at a rate dependent on the dosage of the contaminant delivered to the cell. PCE appears to affect the cell when the cell potential was over potentials higher than approximately 0.2 V. No effects were observed at voltages around or below 0.2 V and the cells could be recovered from previous poisoning performed at higher potentials. Recoveries at those low voltages could be induced by changing the operating voltage or by purging the system. Poisoning did not appear to affect the membrane conductivity. Measurements with long-path length IR results suggested catalytic decomposition of the PCE by hydrogen over the anode catalyst.

Hydrogen isotope recovery using a cathode water vapor feed PEM electrolyzer

Abstract A critical component of tritium glovebox operations is the recovery of high value tritium from the water vapor in the glove box atmosphere. One proposed method to improve existing tritium recovery systems is to replace the disposable hot magnesium beds used to separate the hydrogen and oxygen in water with continuous use Proton Exchange Membrane Electrolyzers (PEMEs). This study examines radiation exposure to the membrane of a PEME and examines the sizing difference that would be needed if the electrolyzer were operated with a cathode water vapor feed instead of an anode liquid water feed.

Effect of the Metal Hydride Tank Structure on the Reaction Heat Recovery for the Totalized Hydrogen Energy Utilization System

A Totalized Hydrogen Energy Utilization System (THEUS) is proposed for load leveling and stabilizing the grid. The THEUS is a novel unitized regenerative fuel cell system that achieves high overall efficiency through optimized heat utilization. In this paper, a metal hydride tank (MHT) is chosen as hydrogen storage. In the MHT, the heating and cooling from adsorption/desorption processes is used to produced heated and chilled water for building ventilation systems. A new horizontal type MHT was developed to enhance the recovery rate of the reaction heat. This tank has a double coil heat exchanger and contained 50kg of AB5 metal hydride. The experimental results were compared with the results which were developed previously at AIST. The new tank results showed an improvement for the heat recovery rate which is the ratio of recovered energy to the entire reaction heat of the metal hydride. The reaction heat recovery was improved due to the decrease of the thermal capacity of the tank.